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Sample records for dna perturbs telomere

  1. Quadruplexes of human telomere DNA

    Czech Academy of Sciences Publication Activity Database

    Vorlíčková, Michaela; Chládková, Jana; Kejnovská, Iva; Kypr, Jaroslav

    2007-01-01

    Roč. 24, č. 6 (2007), s. 710 ISSN 0739-1102. [The 15th Conversation . 19.06.2007-23.06.2007, Albany] R&D Projects: GA ČR(CZ) GA204/07/0057; GA AV ČR(CZ) IAA100040701 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : DNA tetraplex * human telomere * CD spectroscopy Subject RIV: BO - Biophysics

  2. Chromatid interchanges at intrachromosomal telomeric DNA sequences

    International Nuclear Information System (INIS)

    Fernandez, J.L.; Vazquez-Gundin, F.; Bilbao, A.; Gosalvez, J.; Goyanes, V.

    1997-01-01

    Chinese hamster Don cells were exposed to X-rays, mitomycin C and teniposide (VM-26) to induce chromatid exchanges (quadriradials and triradials). After fluorescence in situ hybridization (FISH) of telomere sequences it was found that interstitial telomere-like DNA sequence arrays presented around five times more breakage-rearrangements than the genome overall. This high recombinogenic capacity was independent of the clastogen, suggesting that this susceptibility is not related to the initial mechanisms of DNA damage. (author)

  3. RTEL1 dismantles T loops and counteracts telomeric G4-DNA to maintain telomere integrity.

    Science.gov (United States)

    Vannier, Jean-Baptiste; Pavicic-Kaltenbrunner, Visnja; Petalcorin, Mark I R; Ding, Hao; Boulton, Simon J

    2012-05-11

    T loops and telomeric G-quadruplex (G4) DNA structures pose a potential threat to genome stability and must be dismantled to permit efficient telomere replication. Here we implicate the helicase RTEL1 in the removal of telomeric DNA secondary structures, which is essential for preventing telomere fragility and loss. In the absence of RTEL1, T loops are inappropriately resolved by the SLX4 nuclease complex, resulting in loss of the telomere as a circle. Depleting SLX4 or blocking DNA replication abolished telomere circles (TCs) and rescued telomere loss in RTEL1(-/-) cells but failed to suppress telomere fragility. Conversely, stabilization of telomeric G4-DNA or loss of BLM dramatically enhanced telomere fragility in RTEL1-deficient cells but had no impact on TC formation or telomere loss. We propose that RTEL1 performs two distinct functions at telomeres: it disassembles T loops and also counteracts telomeric G4-DNA structures, which together ensure the dynamics and stability of the telomere. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Peroxiredoxin 1 Protects Telomeres from Oxidative Damage and Preserves Telomeric DNA for Extension by Telomerase

    Directory of Open Access Journals (Sweden)

    Eric Aeby

    2016-12-01

    Full Text Available Oxidative damage of telomeres can promote cancer, cardiac failure, and muscular dystrophy. Specific mechanisms protecting telomeres from oxidative damage have not been described. We analyzed telomeric chromatin composition during the cell cycle and show that the antioxidant enzyme peroxiredoxin 1 (PRDX1 is enriched at telomeres during S phase. Deletion of the PRDX1 gene leads to damage of telomeric DNA upon oxidative stress, revealing a protective function of PRDX1 against oxidative damage at telomeres. We also show that the oxidized nucleotide 8-oxo-2′deoxyguanosine-5′-triphosphate (8oxodGTP causes premature chain termination when incorporated by telomerase and that some DNA substrates terminating in 8oxoG prevent extension by telomerase. Thus, PRDX1 safeguards telomeres from oxygen radicals to counteract telomere damage and preserve telomeric DNA for elongation by telomerase.

  5. Epigenetic telomere protection by Drosophila DNA damage response pathways.

    Science.gov (United States)

    Oikemus, Sarah R; Queiroz-Machado, Joana; Lai, KuanJu; McGinnis, Nadine; Sunkel, Claudio; Brodsky, Michael H

    2006-05-01

    Analysis of terminal deletion chromosomes indicates that a sequence-independent mechanism regulates protection of Drosophila telomeres. Mutations in Drosophila DNA damage response genes such as atm/tefu, mre11, or rad50 disrupt telomere protection and localization of the telomere-associated proteins HP1 and HOAP, suggesting that recognition of chromosome ends contributes to telomere protection. However, the partial telomere protection phenotype of these mutations limits the ability to test if they act in the epigenetic telomere protection mechanism. We examined the roles of the Drosophila atm and atr-atrip DNA damage response pathways and the nbs homolog in DNA damage responses and telomere protection. As in other organisms, the atm and atr-atrip pathways act in parallel to promote telomere protection. Cells lacking both pathways exhibit severe defects in telomere protection and fail to localize the protection protein HOAP to telomeres. Drosophila nbs is required for both atm- and atr-dependent DNA damage responses and acts in these pathways during DNA repair. The telomere fusion phenotype of nbs is consistent with defects in each of these activities. Cells defective in both the atm and atr pathways were used to examine if DNA damage response pathways regulate telomere protection without affecting telomere specific sequences. In these cells, chromosome fusion sites retain telomere-specific sequences, demonstrating that loss of these sequences is not responsible for loss of protection. Furthermore, terminally deleted chromosomes also fuse in these cells, directly implicating DNA damage response pathways in the epigenetic protection of telomeres. We propose that recognition of chromosome ends and recruitment of HP1 and HOAP by DNA damage response proteins is essential for the epigenetic protection of Drosophila telomeres. Given the conserved roles of DNA damage response proteins in telomere function, related mechanisms may act at the telomeres of other organisms.

  6. DNA-PKcs is critical for telomere capping

    Energy Technology Data Exchange (ETDEWEB)

    Gilley, David; Tanaka, Hiromi; Hande, M. Prakash; Kurimasa,Akihiro; Li, Gloria C.; Chen, David J.

    2001-04-10

    The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is critical for DNA repair via the non-homologous end joining (NHEJ) pathway. Previously, it was reported that bone marrow cells and spontaneously transformed fibroblasts from SCID (severe combined immunodeficiency) mice have defects in telomere maintenance. The genetically defective SCID mouse arose spontaneously from its parental strain CB17. One known genomic alteration in SCID mice is a truncation of the extreme carboxyl-terminus of DNA-PKcs, but other as yet unidentified alterations may also exist. We have used a defined system, the DNA-PKcs knockout mouse, to investigate specifically the role DNA-PKcs specifically plays in telomere maintenance. We report that primary mouse embryonic fibroblasts (MEFs) and primary cultured kidney cells from 6-8 month old DNA-PKcs deficient mice accumulate a large number of telomere fusions, yet still retain wildtype telomere length. Thus, the phenotype of this defect separates the two-telomere related phenotypes, capping and length maintenance. DNA-PKcs deficient MEFs also exhibit elevated levels of chromosome fragments and breaks, which correlate with increased telomere fusions. Based on the high levels of telomere fusions observed in DNA-PKcs deficient cells, we conclude that DNA-PKcs plays an important capping role at the mammalian telomere.

  7. Molecular recognition in complexes of TRF proteins with telomeric DNA.

    Directory of Open Access Journals (Sweden)

    Miłosz Wieczór

    Full Text Available Telomeres are specialized nucleoprotein assemblies that protect the ends of linear chromosomes. In humans and many other species, telomeres consist of tandem TTAGGG repeats bound by a protein complex known as shelterin that remodels telomeric DNA into a protective loop structure and regulates telomere homeostasis. Shelterin recognizes telomeric repeats through its two major components known as Telomere Repeat-Binding Factors, TRF1 and TRF2. These two homologous proteins are therefore essential for the formation and normal function of telomeres. Indeed, TRF1 and TRF2 are implicated in a plethora of different cellular functions and their depletion leads to telomere dysfunction with chromosomal fusions, followed by apoptotic cell death. More specifically, it was found that TRF1 acts as a negative regulator of telomere length, and TRF2 is involved in stabilizing the loop structure. Consequently, these proteins are of great interest, not only because of their key role in telomere maintenance and stability, but also as potential drug targets. In the current study, we investigated the molecular basis of telomeric sequence recognition by TRF1 and TRF2 and their DNA binding mechanism. We used molecular dynamics (MD to calculate the free energy profiles for binding of TRFs to telomeric DNA. We found that the predicted binding free energies were in good agreement with experimental data. Further, different molecular determinants of binding, such as binding enthalpies and entropies, the hydrogen bonding pattern and changes in surface area, were analyzed to decompose and examine the overall binding free energies at the structural level. With this approach, we were able to draw conclusions regarding the consecutive stages of sequence-specific association, and propose a novel aspartate-dependent mechanism of sequence recognition. Finally, our work demonstrates the applicability of computational MD-based methods to studying protein-DNA interactions.

  8. Detection of circular telomeric DNA without 2D gel electrophoresis.

    Science.gov (United States)

    Dlaska, Margit; Anderl, Conrad; Eisterer, Wolfgang; Bechter, Oliver E

    2008-09-01

    The end of linear chromosomes forms a lasso-like structure called the t-loop. Such t-loops resemble a DNA recombination intermediate, where the single-stranded 3' overhang is arrested in a stretch of duplex DNA. Presumably, such a t-loop can also be deleted via a recombination process. This would result in the occurrence of circular extrachromosomal telomeric DNA (t-circles), which are known to be abundantly present in immortal cells engaging the recombination-based alternative lengthening of telomeres pathway (ALT pathway). Little is known about the basic mechanism of telomeric recombination in these cells and what ultimately causes the generation of such t-circles. Current standard procedures for detecting these molecules involve 2D gel electrophoresis or electron microscopy. However, both methods are labor intense and sophisticated to perform. Here, we present a simpler, faster, and equally sensitive method for detecting t-circles. Our approach is a telomere restriction fragment assay that involves the enzymatic preservation of circular DNA with Klenow enzyme followed by Bal31 degradation of the remaining linear DNA molecules. We show that with this approach t-circles can be detected in ALT cell lines, whereas no t-circles are present in telomerase-positive cell lines. We consider our approach a valid method in which t-circle generation is the experimental readout.

  9. RTEL1 contributes to DNA replication and repair and telomere maintenance

    NARCIS (Netherlands)

    Uringa, Evert-Jan; Lisaingo, Kathleen; Pickett, Hilda A.; Brind'Amour, Julie; Rohde, Jan-Hendrik; Zelensky, Alex; Essers, Jeroen; Lansdorp, Peter M.

    2012-01-01

    Telomere maintenance and DNA repair are important processes that protect the genome against instability. mRtel1, an essential helicase, is a dominant factor setting telomere length in mice. In addition, mRtel1 is involved in DNA double-strand break repair. The role of mRtel1 in telomere maintenance

  10. RTEL1 contributes to DNA replication and repair and telomere maintenance

    NARCIS (Netherlands)

    E.J. Uringa; K. Lisaingo (Kathleen); H.A. Pickett (Hilda); J. Brind'Amour (Julie); J.-H. Rohde (Jan-Hendrik); A. Zelensky (Alexander); J. Essers (Jeroen); P.M. Lansdorp (Peter)

    2012-01-01

    textabstractTelomere maintenance and DNA repair are important processes that protect the genome against instability. mRtel1, an essential helicase, is a dominant factor setting telomere length in mice. In addition, mRtel1 is involved in DNA double-strand break repair. The role of mRtel1 in telomere

  11. Single-strand DNA-binding protein SSB1 facilitates TERT recruitment to telomeres and maintains telomere G-overhangs.

    Science.gov (United States)

    Pandita, Raj K; Chow, Tracy T; Udayakumar, Durga; Bain, Amanda L; Cubeddu, Liza; Hunt, Clayton R; Shi, Wei; Horikoshi, Nobuo; Zhao, Yong; Wright, Woodring E; Khanna, Kum Kum; Shay, Jerry W; Pandita, Tej K

    2015-03-01

    Proliferating mammalian stem and cancer cells express telomerase [telomerase reverse transcriptase (TERT)] in an effort to extend chromosomal G-overhangs and maintain telomere ends. Telomerase-expressing cells also have higher levels of the single-stranded DNA-binding protein SSB1, which has a critical role in DNA double-strand break (DSB) repair. Here, we report that SSB1 binds specifically to G-strand telomeric DNA in vitro and associates with telomeres in vivo. SSB1 interacts with the TERT catalytic subunit and regulates its interaction with telomeres. Deletion of SSB1 reduces TERT interaction with telomeres and leads to G-overhang loss. Although SSB1 is recruited to DSB sites, we found no corresponding change in TERT levels at these sites, implying that SSB1-TERT interaction relies upon a specific chromatin structure or context. Our findings offer an explanation for how telomerase is recruited to telomeres to facilitate G-strand DNA extension, a critical step in maintaining telomere ends and cell viability in all cancer cells. Cancer Res; 75(5); 858-69. ©2015 AACR. ©2015 American Association for Cancer Research.

  12. Single-strand DNA binding protein SSB1 facilitates TERT recruitment to telomeres and maintains telomere G-overhangs

    Science.gov (United States)

    Pandita, Raj K.; Chow, Tracy T.; Udayakumar, Durga; Bain, Amanda L.; Cubeddu, Liza; Hunt, Clayton R.; Shi, Wei; Horikoshi, Nobuo; Zhao, Yong; Wright, Woodring E.; Khanna, Kum Kum; Shay, Jerry W.; Pandita, Tej K.

    2015-01-01

    Proliferating mammalian stem and cancer cells express telomerase (TERT) in an effort to extend chromosomal G-overhangs and maintain telomere ends. Telomerase-expressing cells also have higher levels of the single-stranded DNA binding protein SSB1, which has a critical role in DNA double-strand break repair. Here we report that SSB1 binds specifically to G-strand telomeric DNA in vitro and associates with telomeres in vivo. SSB1 interacted with the TERT catalytic subunit and regulates its interaction with telomeres. Deletion of SSB1 reduced TERT interaction with telomeres and lead to G-overhang loss. While SSB1 was recruited to DSB sites, we found no corresponding change in TERT levels at these sites, implying that SSB1-TERT interaction relied upon a specific chromatin structure or context. Our findings offer an explanation for how telomerase is recruited to telomeres to facilitate G-strand DNA extension, a critical step in maintaining telomere ends and cell viability in all cancer cells. PMID:25589350

  13. Non-erythroid alpha spectrin prevents telomere dysfunction after DNA interstrand cross-link damage

    OpenAIRE

    Zhang, Pan; Herbig, Utz; Coffman, Frederick; Lambert, Muriel W.

    2013-01-01

    Telomere integrity is critical for telomere function and genomic stability. We previously demonstrated that non-erythroid ?-spectrin (?IISp) is present in mammalian cell nuclei where it is important in repair of DNA interstrand cross-links (ICLs) and chromosome stability. We now demonstrate that ?IISp is also important for telomere maintenance after ICL damage. It localizes to telomeres in S phase after ICL damage where it has enhanced association with TRF1 and TRF2 and is required for recrui...

  14. Involvement of DNA repair in telomere maintenance and chromosomal instability in human cells

    International Nuclear Information System (INIS)

    Ayouaz, Ali

    2008-01-01

    Telomeres are a major actor of cell immortalization, precursor of a carcinogenesis process. Thus, it appears that the maintenance of telomeres is crucial in the implementation of carcinogenesis process. Due to their structures and under some conditions, telomeres can be assimilated in some respects to chromosomal breakages. Within this perspective, this research thesis aims at determining under which circumstances telomeres can be taken as targets by DNA repair mechanisms. More precisely, the author addressed the respective contributions of two repair mechanisms (the Non-Homologous End-Joining or NHEJ, and Homologous Recombination or HR) in the maintenance of telomere integrity. The author first discusses knowledge related to the interaction between chromosomal extremities and repair mechanisms. Then, he defines the behaviour of these mechanisms with respect to telomeres. He shows that, in absence of recombination mechanisms, the integrity of telomeres is not affected. Finally, he reports the attempt to determine their respective contributions in telomeric homeostasis [fr

  15. Human telomeres are hypersensitive to UV-induced DNA Damage and refractory to repair.

    Directory of Open Access Journals (Sweden)

    Patrick J Rochette

    2010-04-01

    Full Text Available Telomeric repeats preserve genome integrity by stabilizing chromosomes, a function that appears to be important for both cancer and aging. In view of this critical role in genomic integrity, the telomere's own integrity should be of paramount importance to the cell. Ultraviolet light (UV, the preeminent risk factor in skin cancer development, induces mainly cyclobutane pyrimidine dimers (CPD which are both mutagenic and lethal. The human telomeric repeat unit (5'TTAGGG/CCCTAA3' is nearly optimal for acquiring UV-induced CPD, which form at dipyrimidine sites. We developed a ChIP-based technique, immunoprecipitation of DNA damage (IPoD, to simultaneously study DNA damage and repair in the telomere and in the coding regions of p53, 28S rDNA, and mitochondrial DNA. We find that human telomeres in vivo are 7-fold hypersensitive to UV-induced DNA damage. In double-stranded oligonucleotides, this hypersensitivity is a property of both telomeric and non-telomeric repeats; in a series of telomeric repeat oligonucleotides, a phase change conferring UV-sensitivity occurs above 4 repeats. Furthermore, CPD removal in the telomere is almost absent, matching the rate in mitochondria known to lack nucleotide excision repair. Cells containing persistent high levels of telomeric CPDs nevertheless proliferate, and chronic UV irradiation of cells does not accelerate telomere shortening. Telomeres are therefore unique in at least three respects: their biophysical UV sensitivity, their prevention of excision repair, and their tolerance of unrepaired lesions. Utilizing a lesion-tolerance strategy rather than repair would prevent double-strand breaks at closely-opposed excision repair sites on opposite strands of a damage-hypersensitive repeat.

  16. RTEL1 contributes to DNA replication and repair and telomere maintenance.

    Science.gov (United States)

    Uringa, Evert-Jan; Lisaingo, Kathleen; Pickett, Hilda A; Brind'Amour, Julie; Rohde, Jan-Hendrik; Zelensky, Alex; Essers, Jeroen; Lansdorp, Peter M

    2012-07-01

    Telomere maintenance and DNA repair are important processes that protect the genome against instability. mRtel1, an essential helicase, is a dominant factor setting telomere length in mice. In addition, mRtel1 is involved in DNA double-strand break repair. The role of mRtel1 in telomere maintenance and genome stability is poorly understood. Therefore we used mRtel1-deficient mouse embryonic stem cells to examine the function of mRtel1 in replication, DNA repair, recombination, and telomere maintenance. mRtel1-deficient mouse embryonic stem cells showed sensitivity to a range of DNA-damaging agents, highlighting its role in replication and genome maintenance. Deletion of mRtel1 increased the frequency of sister chromatid exchange events and suppressed gene replacement, demonstrating the involvement of the protein in homologous recombination. mRtel1 localized transiently at telomeres and is needed for efficient telomere replication. Of interest, in the absence of mRtel1, telomeres in embryonic stem cells appeared relatively stable in length, suggesting that mRtel1 is required to allow extension by telomerase. We propose that mRtel1 is a key protein for DNA replication, recombination, and repair and efficient elongation of telomeres by telomerase.

  17. RTEL1 contributes to DNA replication and repair and telomere maintenance.

    OpenAIRE

    Uringa, E.-J.; Lisaingo, K.; Pickett, H. A.; Brind'Amour, J.; Rohde, J.-H.; Zelensky, A.; Essers, J.; Lansdorp, P. M.

    2012-01-01

    textabstractTelomere maintenance and DNA repair are important processes that protect the genome against instability. mRtel1, an essential helicase, is a dominant factor setting telomere length in mice. In addition, mRtel1 is involved in DNA double-strand break repair. The role of mRtel1 in telomere maintenance and genome stability is poorly understood. Therefore we used mRtel1-deficient mouse embryonic stem cells to examine the function of mRtel1 in replication, DNA repair, recombination, and...

  18. TERRA and hnRNPA1 orchestrate an RPA-to-POT1 switch on telomeric single-stranded DNA.

    Science.gov (United States)

    Flynn, Rachel Litman; Centore, Richard C; O'Sullivan, Roderick J; Rai, Rekha; Tse, Alice; Songyang, Zhou; Chang, Sandy; Karlseder, Jan; Zou, Lee

    2011-03-24

    Maintenance of telomeres requires both DNA replication and telomere 'capping' by shelterin. These two processes use two single-stranded DNA (ssDNA)-binding proteins, replication protein A (RPA) and protection of telomeres 1 (POT1). Although RPA and POT1 each have a critical role at telomeres, how they function in concert is not clear. POT1 ablation leads to activation of the ataxia telangiectasia and Rad3-related (ATR) checkpoint kinase at telomeres, suggesting that POT1 antagonizes RPA binding to telomeric ssDNA. Unexpectedly, we found that purified POT1 and its functional partner TPP1 are unable to prevent RPA binding to telomeric ssDNA efficiently. In cell extracts, we identified a novel activity that specifically displaces RPA, but not POT1, from telomeric ssDNA. Using purified protein, here we show that the heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) recapitulates the RPA displacing activity. The RPA displacing activity is inhibited by the telomeric repeat-containing RNA (TERRA) in early S phase, but is then unleashed in late S phase when TERRA levels decline at telomeres. Interestingly, TERRA also promotes POT1 binding to telomeric ssDNA by removing hnRNPA1, suggesting that the re-accumulation of TERRA after S phase helps to complete the RPA-to-POT1 switch on telomeric ssDNA. Together, our data suggest that hnRNPA1, TERRA and POT1 act in concert to displace RPA from telomeric ssDNA after DNA replication, and promote telomere capping to preserve genomic integrity.

  19. Cooperation of DNA-PKcs and WRN helicase in the maintenance of telomeric D-loops

    DEFF Research Database (Denmark)

    Kusumoto-Matsuo, Rika; Opresko, Patricia L; Ramsden, Dale

    2010-01-01

    Werner syndrome is an inherited human progeriod syndrome caused by mutations in the gene encoding the Werner Syndrome protein, WRN. It has both 3'-5' DNA helicase and exonuclease activities, and is suggested to have roles in many aspects of DNA metabolism, including DNA repair and telomere...... D-loop model substrate. In addition, the length of telomeric G-tails decreases in DNA-PKcs knockdown cells, and this phenotype is reversed by overexpression of WRN helicase. These results suggest that WRN and DNA-PKcs may cooperatively prevent G-tail shortening in vivo....

  20. Fission yeast shelterin regulates DNA polymerases and Rad3(ATR kinase to limit telomere extension.

    Directory of Open Access Journals (Sweden)

    Ya-Ting Chang

    2013-11-01

    Full Text Available Studies in fission yeast have previously identified evolutionarily conserved shelterin and Stn1-Ten1 complexes, and established Rad3(ATR/Tel1(ATM-dependent phosphorylation of the shelterin subunit Ccq1 at Thr93 as the critical post-translational modification for telomerase recruitment to telomeres. Furthermore, shelterin subunits Poz1, Rap1 and Taz1 have been identified as negative regulators of Thr93 phosphorylation and telomerase recruitment. However, it remained unclear how telomere maintenance is dynamically regulated during the cell cycle. Thus, we investigated how loss of Poz1, Rap1 and Taz1 affects cell cycle regulation of Ccq1 Thr93 phosphorylation and telomere association of telomerase (Trt1(TERT, DNA polymerases, Replication Protein A (RPA complex, Rad3(ATR-Rad26(ATRIP checkpoint kinase complex, Tel1(ATM kinase, shelterin subunits (Tpz1, Ccq1 and Poz1 and Stn1. We further investigated how telomere shortening, caused by trt1Δ or catalytically dead Trt1-D743A, affects cell cycle-regulated telomere association of telomerase and DNA polymerases. These analyses established that fission yeast shelterin maintains telomere length homeostasis by coordinating the differential arrival of leading (Polε and lagging (Polα strand DNA polymerases at telomeres to modulate Rad3(ATR association, Ccq1 Thr93 phosphorylation and telomerase recruitment.

  1. Strand exchange of telomeric DNA catalyzed by the Werner syndrome protein (WRN) is specifically stimulated by TRF2

    Science.gov (United States)

    Edwards, Deanna N.; Orren, David K.; Machwe, Amrita

    2014-01-01

    Werner syndrome (WS), caused by loss of function of the RecQ helicase WRN, is a hereditary disease characterized by premature aging and elevated cancer incidence. WRN has DNA binding, exonuclease, ATPase, helicase and strand annealing activities, suggesting possible roles in recombination-related processes. Evidence indicates that WRN deficiency causes telomeric abnormalities that likely underlie early onset of aging phenotypes in WS. Furthermore, TRF2, a protein essential for telomere protection, interacts with WRN and influences its basic helicase and exonuclease activities. However, these studies provided little insight into WRN's specific function at telomeres. Here, we explored the possibility that WRN and TRF2 cooperate during telomeric recombination processes. Our results indicate that TRF2, through its interactions with both WRN and telomeric DNA, stimulates WRN-mediated strand exchange specifically between telomeric substrates; TRF2's basic domain is particularly important for this stimulation. Although TRF1 binds telomeric DNA with similar affinity, it has minimal effects on WRN-mediated strand exchange of telomeric DNA. Moreover, TRF2 is displaced from telomeric DNA by WRN, independent of its ATPase and helicase activities. Together, these results suggest that TRF2 and WRN act coordinately during telomeric recombination processes, consistent with certain telomeric abnormalities associated with alteration of WRN function. PMID:24880691

  2. Perturbed soliton excitations in inhomogeneous DNA

    International Nuclear Information System (INIS)

    Daniel, M.; Vasumathi, V.

    2005-05-01

    We study nonlinear dynamics of inhomogeneous DNA double helical chain under dynamic plane-base rotator model by considering angular rotation of bases in a plane normal to the helical axis. The DNA dynamics in this case is found to be governed by a perturbed sine-Gordon equation when taking into account the interstrand hydrogen bonding energy and intrastrand inhomogeneous stacking energy and making an analogy with the Heisenberg model of the Hamiltonian for an inhomogeneous anisotropic spin ladder with ferromagnetic legs and antiferromagentic rung coupling. In the homogeneous limit the dynamics is governed by the kink-antikink soliton of the sine-Gordon equation which represents the formation of open state configuration in DNA double helix. The effect of inhomogeneity in stacking energy in the form of localized and periodic variations on the formation of open states in DNA is studied under perturbation. The perturbed soliton is obtained using a multiple scale soliton perturbation theory by solving the associated linear eigen value problem and constructing the complete set of eigen functions. The inhomogeneity in stacking energy is found to modulate the width and speed of the soliton depending on the nature of inhomogeneity. Also it introduces fluctuations in the form of train of pulses or periodic oscillation in the open state configuration (author)

  3. Systematic Analysis of the DNA Damage Response Network in Telomere Defective Budding Yeast

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    Eva-Maria Holstein

    2017-07-01

    Full Text Available Functional telomeres are critically important to eukaryotic genetic stability. Scores of proteins and pathways are known to affect telomere function. Here, we report a series of related genome-wide genetic interaction screens performed on budding yeast cells with acute or chronic telomere defects. Genetic interactions were examined in cells defective in Cdc13 and Stn1, affecting two components of CST, a single stranded DNA (ssDNA binding complex that binds telomeric DNA. For comparison, genetic interactions were also examined in cells with defects in Rfa3, affecting the major ssDNA binding protein, RPA, which has overlapping functions with CST at telomeres. In more complex experiments, genetic interactions were measured in cells lacking EXO1 or RAD9, affecting different aspects of the DNA damage response, and containing a cdc13-1 induced telomere defect. Comparing fitness profiles across these data sets helps build a picture of the specific responses to different types of dysfunctional telomeres. The experiments show that each context reveals different genetic interactions, consistent with the idea that each genetic defect causes distinct molecular defects. To help others engage with the large volumes of data, the data are made available via two interactive web-based tools: Profilyzer and DIXY. One particularly striking genetic interaction observed was that the chk1∆ mutation improved fitness of cdc13-1 exo1∆ cells more than other checkpoint mutations (ddc1∆, rad9∆, rad17∆, and rad24∆, whereas, in cdc13-1 cells, the effects of all checkpoint mutations were similar. We show that this can be explained by Chk1 stimulating resection—a new function for Chk1 in the eukaryotic DNA damage response network.

  4. Cytogenetic Analysis of Populus trichocarpa - Ribosomal DNA, Telomere Repeat Sequence, and Marker-selected BACs

    Science.gov (United States)

    M.N. lslam-Faridi; C.D. Nelson; S.P. DiFazio; L.E. Gunter; G.A. Tuskan

    2009-01-01

    The 185-285 rDNA and 55 rDNA loci in Populus trichocarpa were localized using fluorescent in situ hybridization (FISH). Two 185-285 rDNA sites and one 55 rDNA site were identified and located at the ends of 3 different chromosomes. FISH signals from the Arabidopsis-type telomere repeat sequence were observed at the distal ends of each chromosome. Six BAC clones...

  5. Leishmania replication protein A-1 binds in vivo single-stranded telomeric DNA

    International Nuclear Information System (INIS)

    Neto, J.L. Siqueira; Lira, C.B.B.; Giardini, M.A.; Khater, L.; Perez, A.M.; Peroni, L.A.; Reis, J.R.R. dos; Freitas-Junior, L.H.; Ramos, C.H.I.; Cano, M.I.N.

    2007-01-01

    Replication protein A (RPA) is a highly conserved heterotrimeric single-stranded DNA-binding protein involved in different events of DNA metabolism. In yeast, subunits 1 (RPA-1) and 2 (RPA-2) work also as telomerase recruiters and, in humans, the complex unfolds G-quartet structures formed by the 3' G-rich telomeric strand. In most eukaryotes, RPA-1 and RPA-2 bind DNA using multiple OB fold domains. In trypanosomatids, including Leishmania, RPA-1 has a canonical OB fold and a truncated RFA-1 structural domain. In Leishmania amazonensis, RPA-1 alone can form a complex in vitro with the telomeric G-rich strand. In this work, we show that LaRPA-1 is a nuclear protein that associates in vivo with Leishmania telomeres. We mapped the boundaries of the OB fold DNA-binding domain using deletion mutants. Since Leishmania and other trypanosomatids lack homologues of known telomere end binding proteins, our results raise questions about the function of RPA-1 in parasite telomeres

  6. Convergence of The Nobel Fields of Telomere Biology and DNA Repair.

    Science.gov (United States)

    Fouquerel, Elise; Opresko, Patricia L

    2017-01-01

    The fields of telomere biology and DNA repair have enjoyed a great deal of cross-fertilization and convergence in recent years. Telomeres function at chromosome ends to prevent them from being falsely recognized as chromosome breaks by the DNA damage response and repair machineries. Conversely, both canonical and nonconical functions of numerous DNA repair proteins have been found to be critical for preserving telomere structure and function. In 2009, Elizabeth Blackburn, Carol Greider and Jack Szostak were awarded the Nobel prize in Physiology or Medicine for the discovery of telomeres and telomerase. Four years later, pioneers in the field of DNA repair, Aziz Sancar, Tomas Lindahl and Paul Modrich were recognized for their seminal contributions by being awarded the Nobel Prize in Chemistry. This review is part of a special issue meant to celebrate this amazing achievement, and will focus in particular on the convergence of nucleotide excision repair and telomere biology, and will discuss the profound implications for human health. © 2016 The American Society of Photobiology.

  7. A colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA based on silver nanoclusters and unmodified gold nanoparticles

    Science.gov (United States)

    Qu, Fei; Chen, Zeqiu; You, Jinmao; Song, Cuihua

    2018-05-01

    Human telomere DNA plays a vital role in genome integrity control and carcinogenesis as an indication for extensive cell proliferation. Herein, silver nanoclusters (Ag NCs) templated by polymer and unmodified gold nanoparticles (Au NPs) are designed as a new colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA. Ag NCs can produce the aggregation of Au NPs, so the color of Au NPs changes to blue and the absorption peak moves to 700 nm. While the telomere DNA can protect Au NPs from aggregation, the color turns to red again and the absorption band blue shift. Benefiting from the obvious color change, we can differentiate the length of telomere DNA by naked eyes. As the length of telomere DNA is longer, the variation of color becomes more noticeable. The detection limits of telomere DNA containing 10, 22, 40, 64 bases are estimated to be 1.41, 1.21, 0.23 and 0.22 nM, respectively. On the other hand, when telomere DNA forms G-quadruplex in the presence of K+, or dsDNA with complementary sequence, both G-quadruplex and dsDNA can protect Au NPs better than the unfolded telomere DNA. Hence, a new colorimetric platform for monitoring structure conversion of DNA is established by Ag NCs-Au NPs system, and to prove this type of application, a selective K+ sensor is developed.

  8. Telomeric Allelic Imbalance Indicates Defective DNA Repair and Sensitivity to DNA-Damaging Agents

    DEFF Research Database (Denmark)

    Birkbak, Nicolai J.; Wang, Zhigang C.; Kim, Ji-Young

    2012-01-01

    with triple-negative breast cancer (TNBC). In serous ovarian cancer treated with platinum-based chemotherapy, higher levels of NtAI forecast a better initial response. We found an inverse relationship between BRCA1 expression and NtAI in sporadic TNBC and serous ovarian cancers without BRCA1 or BRCA2 mutation...... of defective DNA repair in cell lines and tumors and correlated these signatures to platinum sensitivity. The number of subchromosomal regions with allelic imbalance extending to the telomere (NtAI) predicted cisplatin sensitivity in vitro and pathologic response to preoperative cisplatin treatment in patients...... also benefit from these agents. NtAI, a genomic measure of unfaithfully repaired DNA, may identify cancer patients likely to benefit from treatments targeting defective DNA repair. Cancer Discov; 2(4); 366–75. ©2012 AACR. This article is highlighted in the In This Issue feature, p. 288...

  9. [RTEL1 (regulator of telomere elongation helicase 1), a DNA helicase essential for genome stability].

    Science.gov (United States)

    Le Guen, Tangui; Jullien, Laurent; Schertzer, Mike; Lefebvre, Axelle; Kermasson, Laetitia; de Villartay, Jean-Pierre; Londoño-Vallejo, Arturo; Revy, Patrick

    2013-12-01

    RTEL1 (regulator of telomere length helicase 1) is a DNA helicase that has been identified more than 10 years ago. Many works since, mainly in the nematode Caenorhabditis elegans and the mouse, have highlighted its role in chromosomal stability, maintenance of telomere length, and DNA repair. Recently, four laboratories have characterized RTEL1 mutations in patients with dyskeratosis congenita (DC) and Hoyeraal-Hreidarsson (HH) syndrome, a rare and severe variant of DC. We here summarize the current knowledge on RTEL1 and discuss the possible other functions that RTEL1 could play. © 2013 médecine/sciences – Inserm.

  10. TRF1 and TRF2 use different mechanisms to find telomeric DNA but share a novel mechanism to search for protein partners at telomeres.

    Science.gov (United States)

    Lin, Jiangguo; Countryman, Preston; Buncher, Noah; Kaur, Parminder; E, Longjiang; Zhang, Yiyun; Gibson, Greg; You, Changjiang; Watkins, Simon C; Piehler, Jacob; Opresko, Patricia L; Kad, Neil M; Wang, Hong

    2014-02-01

    Human telomeres are maintained by the shelterin protein complex in which TRF1 and TRF2 bind directly to duplex telomeric DNA. How these proteins find telomeric sequences among a genome of billions of base pairs and how they find protein partners to form the shelterin complex remains uncertain. Using single-molecule fluorescence imaging of quantum dot-labeled TRF1 and TRF2, we study how these proteins locate TTAGGG repeats on DNA tightropes. By virtue of its basic domain TRF2 performs an extensive 1D search on nontelomeric DNA, whereas TRF1's 1D search is limited. Unlike the stable and static associations observed for other proteins at specific binding sites, TRF proteins possess reduced binding stability marked by transient binding (∼ 9-17 s) and slow 1D diffusion on specific telomeric regions. These slow diffusion constants yield activation energy barriers to sliding ∼ 2.8-3.6 κ(B)T greater than those for nontelomeric DNA. We propose that the TRF proteins use 1D sliding to find protein partners and assemble the shelterin complex, which in turn stabilizes the interaction with specific telomeric DNA. This 'tag-team proofreading' represents a more general mechanism to ensure a specific set of proteins interact with each other on long repetitive specific DNA sequences without requiring external energy sources.

  11. Lack of association of colonic epithelium telomere length and oxidative DNA damage in Type 2 diabetes under good metabolic control

    Directory of Open Access Journals (Sweden)

    Kennedy Hugh

    2008-10-01

    Full Text Available Abstract Background Telomeres are DNA repeat sequences necessary for DNA replication which shorten at cell division at a rate directly related to levels of oxidative stress. Critical telomere shortening predisposes to cell senescence and to epithelial malignancies. Type 2 diabetes is characterised by increased oxidative DNA damage, telomere attrition, and an increased risk of colonic malignancy. We hypothesised that the colonic mucosa in Type 2 diabetes would be characterised by increased DNA damage and telomere shortening. Methods We examined telomere length (by flow fluorescent in situ hybridization and oxidative DNA damage (flow cytometry of 8 – oxoguanosine in the colonic mucosal cells of subjects with type 2 diabetes (n = 10; mean age 62.2 years, mean HbA1c 6.9% and 22 matched control subjects. No colonic pathology was apparent in these subjects at routine gastrointestinal investigations. Results Mean colonic epithelial telomere length in the diabetes group was not significantly different from controls (10.6 [3.6] vs. 12.1 [3.4] Molecular Equivalent of Soluble Fluorochrome Units [MESF]; P = 0.5. Levels of oxidative DNA damage were similar in both T2DM and control groups (2.6 [0.6] vs. 2.5 [0.6] Mean Fluorescent Intensity [MFI]; P = 0.7. There was no significant relationship between oxidative DNA damage and telomere length in either group (both p > 0.1. Conclusion Colonic epithelium in Type 2 diabetes does not differ significantly from control colonic epithelium in oxidative DNA damage or telomere length. There is no evidence in this study for increased oxidative DNA damage or significant telomere attrition in colonic mucosa as a carcinogenic mechanism.

  12. Escape from Telomere-Driven Crisis Is DNA Ligase III Dependent

    Directory of Open Access Journals (Sweden)

    Rhiannon E. Jones

    2014-08-01

    Full Text Available Short dysfunctional telomeres are capable of fusion, generating dicentric chromosomes and initiating breakage-fusion-bridge cycles. Cells that escape the ensuing cellular crisis exhibit large-scale genomic rearrangements that drive clonal evolution and malignant progression. We demonstrate that there is an absolute requirement for fully functional DNA ligase III (LIG3, but not ligase IV (LIG4, to facilitate the escape from a telomere-driven crisis. LIG3- and LIG4-dependent alternative (A and classical (C nonhomologous end-joining (NHEJ pathways were capable of mediating the fusion of short dysfunctional telomeres, both displaying characteristic patterns of microhomology and deletion. Cells that failed to escape crisis exhibited increased proportions of C-NHEJ-mediated interchromosomal fusions, whereas those that escaped displayed increased proportions of intrachromosomal fusions. We propose that the balance between inter- and intrachromosomal telomere fusions dictates the ability of human cells to escape crisis and is influenced by the relative activities of A- and C-NHEJ at short dysfunctional telomeres.

  13. Chalcone-imidazolone conjugates induce apoptosis through DNA damage pathway by affecting telomeres

    Directory of Open Access Journals (Sweden)

    Kamal Ahmed

    2011-04-01

    Full Text Available Abstract Background Breast cancer is one of the most prevalent cancers in the world and more than one million women are diagnosed leading to 410,000 deaths every year. In our previous studies new chalcone-imidazolone conjugates were prepared and evaluated for their anticancer activity in a panel of 53 human tumor cell lines and the lead compounds identified were 6 and 8. This prompted us to investigate the mechanism of apoptotic event. Results Involvement of pro-apoptotic protein (Bax, active caspase-9 and cleavage of retinoblastoma protein was studied. Interestingly, the compounds caused upregulation of p21, check point proteins (Chk1, Chk2 and as well as their phosphorylated forms which are known to regulate the DNA damage pathway. Increased p53BP1 foci by immunolocalisation studies and TRF1 suggested the possible involvement of telomere and associated proteins in the apoptotic event. The telomeric protein such as TRF2 which is an important target for anticancer therapy against human breast cancer was extensively studied along with proteins involved in proper functioning of telomeres. Conclusions The apoptotic proteins such as Bax, active caspase-9 and cleaved RB are up-regulated in the compound treated cells revealing the apoptotic nature of the compounds. Down regulation of TRF2 and upregulation of the TRF1 as well as telomerase assay indicated the decrease in telomeric length revealing telomeric dysfunction and thereby controlling the rapid rate of cell proliferation. In summary, chalcone-imidazolone conjugates displayed significant DNA damage activity particularly at telomeres and caused both apoptosis and senescence-like growth arrest which suggested that these compounds have potential activity against breast carcinoma.

  14. Mitosis, double strand break repair, and telomeres: a view from the end: how telomeres and the DNA damage response cooperate during mitosis to maintain genome stability.

    Science.gov (United States)

    Cesare, Anthony J

    2014-11-01

    Double strand break (DSB) repair is suppressed during mitosis because RNF8 and downstream DNA damage response (DDR) factors, including 53BP1, do not localize to mitotic chromatin. Discovery of the mitotic kinase-dependent mechanism that inhibits DSB repair during cell division was recently reported. It was shown that restoring mitotic DSB repair was detrimental, resulting in repair dependent genome instability and covalent telomere fusions. The telomere DDR that occurs naturally during cellular aging and in cancer is known to be refractory to G2/M checkpoint activation. Such DDR-positive telomeres, and those that occur as part of the telomere-dependent prolonged mitotic arrest checkpoint, normally pass through mitosis without covalent ligation, but result in cell growth arrest in G1 phase. The discovery that suppressing DSB repair during mitosis may function primarily to protect DDR-positive telomeres from fusing during cell division reinforces the unique cooperation between telomeres and the DDR to mediate tumor suppression. © 2014 The Author. Bioessays published by WILEY Periodicals, Inc.

  15. Monovalent cation induced structural transitions in telomeric DNAs: G-DNA folding intermediates

    International Nuclear Information System (INIS)

    Hardin, C.C.; Watson, T.; Henderson, E.; Prosser, J.K.

    1991-01-01

    Telomeric DNA consists of G- and C-rich strands that are always polarized such that the G-rich strand extends past the 3' end of the duplex to form a 12-16-base overhang. These overhanging strands can self-associate in vitro to form intramolecular structures that have several unusual physical properties and at least one common feature, the presence of non-Watson-Crick G·G base pairs. The term G-DNA was coined for this class of structures. On the basis of gel electrophoresis, imino proton NMR, and circular dichroism (CD) results, the authors find that changing the counterions from sodium to potassium specifically induces conformational transitions in the G-rich telomeric DNA from Tetrahymena, d(T 2 G 4 ) 4 (TET4), which results in a change from the intramolecular species to an apparent multistranded structure, accompanied by an increase in the melting temperature of the base pairs of >25 degree, as monitored by loss of the imino proton NMR signals. They infer that the multistranded structure is a quadruplex. The results indicate that specific differences in ionic interactions can result in a switch in telomeric DNAs between intramolecular hairpin-like or quadruplex-containing species and intermolecular quadruplex structures, all of which involve G·G base pairing interaction. They propose a model in which duplex or hairpin forms of G-DNA are folding intermediates in the formation of either 1-, 2-, or 4-stranded quadruplex structures

  16. DNA copy number, including telomeres and mitochondria, assayed using next-generation sequencing

    Directory of Open Access Journals (Sweden)

    Jackson Stuart

    2010-04-01

    Full Text Available Abstract Background DNA copy number variations occur within populations and aberrations can cause disease. We sought to develop an improved lab-automatable, cost-efficient, accurate platform to profile DNA copy number. Results We developed a sequencing-based assay of nuclear, mitochondrial, and telomeric DNA copy number that draws on the unbiased nature of next-generation sequencing and incorporates techniques developed for RNA expression profiling. To demonstrate this platform, we assayed UMC-11 cells using 5 million 33 nt reads and found tremendous copy number variation, including regions of single and homogeneous deletions and amplifications to 29 copies; 5 times more mitochondria and 4 times less telomeric sequence than a pool of non-diseased, blood-derived DNA; and that UMC-11 was derived from a male individual. Conclusion The described assay outputs absolute copy number, outputs an error estimate (p-value, and is more accurate than array-based platforms at high copy number. The platform enables profiling of mitochondrial levels and telomeric length. The assay is lab-automatable and has a genomic resolution and cost that are tunable based on the number of sequence reads.

  17. Thermodynamic characterization of binding Oxytricha nova single strand telomere DNA with the alpha protein N-terminal domain.

    Science.gov (United States)

    Buczek, Pawel; Horvath, Martin P

    2006-06-23

    The Oxytricha nova telemere binding protein alpha subunit binds single strand DNA and participates in a nucleoprotein complex that protects the very ends of chromosomes. To understand how the N-terminal, DNA binding domain of alpha interacts with DNA we measured the stoichiometry, enthalpy (DeltaH), entropy (DeltaS), and dissociation constant (K(D-DNA)) for binding telomere DNA fragments at different temperatures and salt concentrations using native gel electrophoresis and isothermal titration calorimetry (ITC). About 85% of the total free energy of binding corresponded with non-electrostatic interactions for all DNAs. Telomere DNA fragments d(T(2)G(4)), d(T(4)G(4)), d(G(3)T(4)G(4)), and d(G(4)T(4)G(4)) each formed monovalent protein complexes. In the case of d(T(4)G(4)T(4)G(4)), which has two tandemly repeated d(TTTTTGGGG) telomere motifs, two binding sites were observed. The high-affinity "A site" has a dissociation constant, K(D-DNA(A)) = 13(+/-4) nM, while the low-affinity "B site" is characterized by K(D-DNA(B)) = 5600(+/-600) nM at 25 degrees C. Nucleotide substitution variants verified that the A site corresponds principally with the 3'-terminal portion of d(T(4)G(4)T(4)G(4)). The relative contributions of entropy (DeltaS) and enthalpy (DeltaH) for binding reactions were DNA length-dependent as was heat capacity (DeltaCp). These trends with respect to DNA length likely reflect structural transitions in the DNA molecule that are coupled with DNA-protein association. Results presented here are important for understanding early intermediates and subsequent stages in the assembly of the full telomere nucleoprotein complex and how binding events can prepare the telomere DNA for extension by telomerase, a critical event in telomere biology.

  18. Super DNAging-New insights into DNA integrity, genome stability and telomeres in the oldest old.

    Science.gov (United States)

    Franzke, Bernhard; Neubauer, Oliver; Wagner, Karl-Heinz

    2015-01-01

    Reductions in DNA integrity, genome stability, and telomere length are strongly associated with the aging process, age-related diseases as well as the age-related loss of muscle mass. However, in people reaching an age far beyond their statistical life expectancy the prevalence of diseases, such as cancer, cardiovascular disease, diabetes or dementia, is much lower compared to "averagely" aged humans. These inverse observations in nonagenarians (90-99 years), centenarians (100-109 years) and super-centenarians (110 years and older) require a closer look into dynamics underlying DNA damage within the oldest old of our society. Available data indicate improved DNA repair and antioxidant defense mechanisms in "super old" humans, which are comparable with much younger cohorts. Partly as a result of these enhanced endogenous repair and protective mechanisms, the oldest old humans appear to cope better with risk factors for DNA damage over their lifetime compared to subjects whose lifespan coincides with the statistical life expectancy. This model is supported by study results demonstrating superior chromosomal stability, telomere dynamics and DNA integrity in "successful agers". There is also compelling evidence suggesting that life-style related factors including regular physical activity, a well-balanced diet and minimized psycho-social stress can reduce DNA damage and improve chromosomal stability. The most conclusive picture that emerges from reviewing the literature is that reaching "super old" age appears to be primarily determined by hereditary/genetic factors, while a healthy lifestyle additionally contributes to achieving the individual maximum lifespan in humans. More research is required in this rapidly growing population of super old people. In particular, there is need for more comprehensive investigations including short- and long-term lifestyle interventions as well as investigations focusing on the mechanisms causing DNA damage, mutations, and telomere

  19. Telomerer og telomerase

    DEFF Research Database (Denmark)

    Bendix, Laila; Kølvraa, Steen

    2010-01-01

    In 2009 the Nobel Prize in Medicine was awarded to EH Blackburn, CW Greider and JW Szostak for their work on "How chromosomes are protected by telomeres and the enzyme telomerase". Telomeres are specialized DNA structures localized at the end of linear chromosomes. Telomeres are known as the biol......In 2009 the Nobel Prize in Medicine was awarded to EH Blackburn, CW Greider and JW Szostak for their work on "How chromosomes are protected by telomeres and the enzyme telomerase". Telomeres are specialized DNA structures localized at the end of linear chromosomes. Telomeres are known...

  20. Repair of O6-methylguanine adducts in human telomeric G-quadruplex DNA by O6-alkylguanine-DNA alkyltransferase

    Science.gov (United States)

    Hellman, Lance M.; Spear, Tyler J.; Koontz, Colton J.; Melikishvili, Manana; Fried, Michael G.

    2014-01-01

    O6-alkylguanine-DNA alkyltransferase (AGT) is a single-cycle DNA repair enzyme that removes pro-mutagenic O6-alkylguanine adducts from DNA. Its functions with short single-stranded and duplex substrates have been characterized, but its ability to act on other DNA structures remains poorly understood. Here, we examine the functions of this enzyme on O6-methylguanine (6mG) adducts in the four-stranded structure of the human telomeric G-quadruplex. On a folded 22-nt G-quadruplex substrate, binding saturated at 2 AGT:DNA, significantly less than the ∼5 AGT:DNA found with linear single-stranded DNAs of similar length, and less than the value found with the telomere sequence under conditions that inhibit quadruplex formation (4 AGT:DNA). Despite these differences, AGT repaired 6mG adducts located within folded G-quadruplexes, at rates that were comparable to those found for a duplex DNA substrate under analogous conditions. Repair was kinetically biphasic with the amplitudes of rapid and slow phases dependent on the position of the adduct within the G-quadruplex: in general, adducts located in the top or bottom tetrads of a quadruplex stack exhibited more rapid-phase repair than did adducts located in the inner tetrad. This distinction may reflect differences in the conformational dynamics of 6mG residues in G-quadruplex DNAs. PMID:25080506

  1. An enzyme-catalyzed multistep DNA refolding mechanism in hairpin telomere formation.

    Directory of Open Access Journals (Sweden)

    Ke Shi

    Full Text Available Hairpin telomeres of bacterial linear chromosomes are generated by a DNA cutting-rejoining enzyme protelomerase. Protelomerase resolves a concatenated dimer of chromosomes as the last step of chromosome replication, converting a palindromic DNA sequence at the junctions between chromosomes into covalently closed hairpins. The mechanism by which protelomerase transforms a duplex DNA substrate into the hairpin telomeres remains largely unknown. We report here a series of crystal structures of the protelomerase TelA bound to DNA that represent distinct stages along the reaction pathway. The structures suggest that TelA converts a linear duplex substrate into hairpin turns via a transient strand-refolding intermediate that involves DNA-base flipping and wobble base-pairs. The extremely compact di-nucleotide hairpin structure of the product is fully stabilized by TelA prior to strand ligation, which drives the reaction to completion. The enzyme-catalyzed, multistep strand refolding is a novel mechanism in DNA rearrangement reactions.

  2. Human telomeric DNA: G-quadruplex, i-motif and Watson–Crick double helix

    Science.gov (United States)

    Phan, Anh Tuân; Mergny, Jean-Louis

    2002-01-01

    Human telomeric DNA composed of (TTAGGG/CCCTAA)n repeats may form a classical Watson–Crick double helix. Each individual strand is also prone to quadruplex formation: the G-rich strand may adopt a G-quadruplex conformation involving G-quartets whereas the C-rich strand may fold into an i-motif based on intercalated C·C+ base pairs. Using an equimolar mixture of the telomeric oligonucleotides d[AGGG(TTAGGG)3] and d[(CCCTAA)3CCCT], we defined which structures existed and which would be the predominant species under a variety of experimental conditions. Under near-physiological conditions of pH, temperature and salt concentration, telomeric DNA was predominantly in a double-helix form. However, at lower pH values or higher temperatures, the G-quadruplex and/or the i-motif efficiently competed with the duplex. We also present kinetic and thermodynamic data for duplex association and for G-quadruplex/i-motif unfolding. PMID:12409451

  3. Fragile sites, dysfunctional telomere and chromosome fusions: What is 5S rDNA role?

    Science.gov (United States)

    Barros, Alain Victor; Wolski, Michele Andressa Vier; Nogaroto, Viviane; Almeida, Mara Cristina; Moreira-Filho, Orlando; Vicari, Marcelo Ricardo

    2017-04-15

    Repetitive DNA regions are known as fragile chromosomal sites which present a high flexibility and low stability. Our focus was characterize fragile sites in 5S rDNA regions. The Ancistrus sp. species shows a diploid number of 50 and an indicative Robertsonian fusion at chromosomal pair 1. Two sequences of 5S rDNA were identified: 5S.1 rDNA and 5S.2 rDNA. The first sequence gathers the necessary structures to gene expression and shows a functional secondary structure prediction. Otherwise, the 5S.2 rDNA sequence does not contain the upstream sequences that are required to expression, furthermore its structure prediction reveals a nonfunctional ribosomal RNA. The chromosomal mapping revealed several 5S.1 and 5S.2 rDNA clusters. In addition, the 5S.2 rDNA clusters were found in acrocentric and metacentric chromosomes proximal regions. The pair 1 5S.2 rDNA cluster is co-located with interstitial telomeric sites (ITS). Our results indicate that its clusters are hotspots to chromosomal breaks. During the meiotic prophase bouquet arrangement, double strand breaks (DSBs) at proximal 5S.2 rDNA of acrocentric chromosomes could lead to homologous and non-homologous repair mechanisms as Robertsonian fusions. Still, ITS sites provides chromosomal instability, resulting in telomeric recombination via TRF2 shelterin protein and a series of breakage-fusion-bridge cycles. Our proposal is that 5S rDNA derived sequences, act as chromosomal fragile sites in association with some chromosomal rearrangements of Loricariidae. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. DNA-PKcs phosphorylates hnRNP-A1 to facilitate the RPA-to-POT1 switch and telomere capping after replication.

    Science.gov (United States)

    Sui, Jiangdong; Lin, Yu-Fen; Xu, Kangling; Lee, Kyung-Jong; Wang, Dong; Chen, Benjamin P C

    2015-07-13

    The heterogeneous nuclear ribonucleoprotein A1 (hnRNP-A1) has been implicated in telomere protection and telomerase activation. Recent evidence has further demonstrated that hnRNP-A1 plays a crucial role in maintaining newly replicated telomeric 3' overhangs and facilitating the switch from replication protein A (RPA) to protection of telomeres 1 (POT1). The role of hnRNP-A1 in telomere protection also involves DNA-dependent protein kinase catalytic subunit (DNA-PKcs), although the detailed regulation mechanism has not been clear. Here we report that hnRNP-A1 is phosphorylated by DNA-PKcs during the G2 and M phases and that DNA-PK-dependent hnRNP-A1 phosphorylation promotes the RPA-to-POT1 switch on telomeric single-stranded 3' overhangs. Consequently, in cells lacking hnRNP-A1 or DNA-PKcs-dependent hnRNP-A1 phosphorylation, impairment of the RPA-to-POT1 switch results in DNA damage response at telomeres during mitosis as well as induction of fragile telomeres. Taken together, our results indicate that DNA-PKcs-dependent hnRNP-A1 phosphorylation is critical for capping of the newly replicated telomeres and prevention of telomeric aberrations. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  5. Hypomethylating drugs efficiently decrease cytosine methylation in telomeric DNA and activate telomerase without affecting telomere lengths in tobacco cells

    Czech Academy of Sciences Publication Activity Database

    Majerová, E.; Fojtová, M.; Mozgová, I.; Bittová, M.; Fajkus, Jiří

    2011-01-01

    Roč. 77, 4-5 (2011), s. 371-380 ISSN 0167-4412 Institutional support: RVO:68081707 Keywords : Nicotiana tabacum * Cell culture * Telomere Subject RIV: BO - Biophysics Impact factor: 4.150, year: 2011

  6. Stability of Human Telomere Quadruplexes at High DNA Concentrations

    Czech Academy of Sciences Publication Activity Database

    Kejnovská, Iva; Vorlíčková, Michaela; Brázdová, Marie; Sagi, J.

    2014-01-01

    Roč. 101, č. 4 (2014), s. 428-438 ISSN 0006-3525 R&D Projects: GA ČR(CZ) GAP205/12/0466 Institutional support: RVO:68081707 Keywords : quadruplex * DNA concentration * folding topology Subject RIV: BO - Biophysics Impact factor: 2.385, year: 2014

  7. Intrauterine Exposure to Maternal Stress Alters Bdnf IV DNA Methylation and Telomere Length in the Brain of Adult Rat Offspring

    Science.gov (United States)

    Blaze, Jennifer; Asok, Arun; Borrelli, Kristyn; Tulbert, Christine; Bollinger, Justin; Ronca Finco, April E.; Roth, Tania L.

    2017-01-01

    DNA methylation (addition of methyl groups to cytosines which normally represses gene transcription) and changes in telomere length (TTAGGG repeats on the ends of chromosomes) are two molecular modifications that result from stress and could contribute to the long-term effects of intrauterine exposure to maternal stress on offspring behavioral outcomes. Here, we measured methylation of Brain-derived neurotrophic factor (Bdnf), a gene important in development and plasticity, and telomere length in the brains of adult rat male and female offspring whose mothers were exposed to unpredictable and variable stressors throughout gestation. Males exposed to prenatal stress had greater methylation (Bdnf IV) in the medial prefrontal cortex (mPFC) compared to non-stressed controls. Further, prenatally-stressed males had shorter telomeres than controls in the mPFC. This study provides the first evidence in a rodent model of an association between prenatal stress exposure and subsequent shorter brain telomere length. Together findings indicate a long-term impact of prenatal stress on DNA methylation and telomere biology with relevance for behavioral and health outcomes, and contribute to a growing literature linking stress to intergenerational epigenetic alterations and changes in telomere length.

  8. cDNA Library Screening Identifies Protein Interactors Potentially Involved in Non-telomeric Roles of Arabidopsis Telomerase

    Directory of Open Access Journals (Sweden)

    Ladislav eDokládal

    2015-11-01

    Full Text Available Telomerase-reverse transcriptase (TERT plays an essential catalytic role in maintaining telomeres. However, in animal systems telomerase plays additional non-telomeric functional roles. We previously screened an Arabidopsis cDNA library for proteins that interact with the C-terminal extension (CTE TERT domain and identified a nuclear-localized protein that contains a RNA recognition motif (RRM. This RRM-protein forms homodimers in both plants and yeast. Mutation of the gene encoding the RRM-protein had no detectable effect on plant growth and development, nor did it affect telomerase activity or telomere length in vivo, suggesting a non-telomeric role for TERT/RRM-protein complexes. The gene encoding the RRM-protein is highly expressed in leaf and reproductive tissues. We further screened an Arabidopsis cDNA library for proteins that interact with the RRM-protein and identified five interactors. These proteins are involved in numerous non-telomere-associated cellular activities. In plants, the RRM-protein, both alone and in a complex with its interactors, localizes to nuclear speckles. Transcriptional analyses in wild-type and rrm mutant plants, as well as transcriptional co-analyses, suggest that TERT, the RRM-protein, and the RRM-protein interactors may play important roles in non-telomeric cellular functions.

  9. Multifunctional Role of ATM/Tel1 Kinase in Genome Stability: From the DNA Damage Response to Telomere Maintenance

    Science.gov (United States)

    2014-01-01

    The mammalian protein kinase ataxia telangiectasia mutated (ATM) is a key regulator of the DNA double-strand-break response and belongs to the evolutionary conserved phosphatidylinositol-3-kinase-related protein kinases. ATM deficiency causes ataxia telangiectasia (AT), a genetic disorder that is characterized by premature aging, cerebellar neuropathy, immunodeficiency, and predisposition to cancer. AT cells show defects in the DNA damage-response pathway, cell-cycle control, and telomere maintenance and length regulation. Likewise, in Saccharomyces cerevisiae, haploid strains defective in the TEL1 gene, the ATM ortholog, show chromosomal aberrations and short telomeres. In this review, we outline the complex role of ATM/Tel1 in maintaining genomic stability through its control of numerous aspects of cellular survival. In particular, we describe how ATM/Tel1 participates in the signal transduction pathways elicited by DNA damage and in telomere homeostasis and its importance as a barrier to cancer development. PMID:25247188

  10. Profiling DNA damage response following mitotic perturbations

    DEFF Research Database (Denmark)

    Pedersen, Ronni Sølvhøi; Karemore, Gopal; Gudjonsson, Thorkell

    2016-01-01

    that a broad spectrum of mitotic errors correlates with increased DNA breakage in daughter cells. Unexpectedly, we find that only a subset of these correlations are functionally linked. We identify the genuine mitosis-born DNA damage events and sub-classify them according to penetrance of the observed...

  11. DNA adducts of antitumor cisplatin preclude telomeric sequences from forming G quadruplexes

    Czech Academy of Sciences Publication Activity Database

    Heringová, Pavla; Kašpárková, Jana; Brabec, Viktor

    2009-01-01

    Roč. 14, č. 6 (2009), s. 959-968 ISSN 0949-8257 R&D Projects: GA MZd(CZ) NR8562; GA MŠk(CZ) LC06030; GA MŠk(CZ) ME08017; GA MŠk(CZ) OC08003; GA AV ČR(CZ) 1QS500040581; GA AV ČR(CZ) KAN200200651; GA AV ČR(CZ) IAA400040803 Grant - others:GA MŠk(CZ) OC09018 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : cisplatin * DNA quadruplex * telomere Subject RIV: BO - Biophysics Impact factor: 3.415, year: 2009

  12. Telomere healing following DNA polymerase arrest-induced breakages is likely the main mechanism generating chromosome 4p terminal deletions.

    Science.gov (United States)

    Hannes, Femke; Van Houdt, Jeroen; Quarrell, Oliver W; Poot, Martin; Hochstenbach, Ron; Fryns, Jean-Pierre; Vermeesch, Joris R

    2010-12-01

    Constitutional developmental disorders are frequently caused by terminal chromosomal deletions. The mechanisms and/or architectural features that might underlie those chromosome breakages remain largely unexplored. Because telomeres are the vital DNA protein complexes stabilizing linear chromosomes against chromosome degradation, fusion, and incomplete replication, those terminal-deleted chromosomes acquired new telomeres either by telomere healing or by telomere capture. To unravel the mechanisms leading to chromosomal breakage and healing, we sequenced nine chromosome 4p terminal deletion boundaries. A computational analysis of the breakpoint flanking region, including 12 previously published pure terminal breakage sites, was performed in order to identify architectural features that might be involved in this process. All terminal 4p truncations were likely stabilized by telomerase-mediated telomere healing. In the majority of breakpoints multiple genetic elements have a potential to induce secondary structures and an enrichment in replication stalling site motifs were identified. These findings suggest DNA replication stalling-induced chromosome breakage during early development is the first mechanistic step leading toward terminal deletion syndromes. © 2010 Wiley-Liss, Inc.

  13. Ligand binding to telomeric G-quadruplex DNA investigated by funnel-metadynamics simulations.

    Science.gov (United States)

    Moraca, Federica; Amato, Jussara; Ortuso, Francesco; Artese, Anna; Pagano, Bruno; Novellino, Ettore; Alcaro, Stefano; Parrinello, Michele; Limongelli, Vittorio

    2017-03-14

    G-quadruplexes (G4s) are higher-order DNA structures typically present at promoter regions of genes and telomeres. Here, the G4 formation decreases the replicative DNA at each cell cycle, finally leading to apoptosis. The ability to control this mitotic clock, particularly in cancer cells, is fascinating and passes through a rational understanding of the ligand/G4 interaction. We demonstrate that an accurate description of the ligand/G4 binding mechanism is possible using an innovative free-energy method called funnel-metadynamics (FM), which we have recently developed to investigate ligand/protein interaction. Using FM simulations, we have elucidated the binding mechanism of the anticancer alkaloid berberine to the human telomeric G4 ( d [AG 3 (T 2 AG 3 ) 3 ]), computing also the binding free-energy landscape. Two ligand binding modes have been identified as the lowest energy states. Furthermore, we have found prebinding sites, which are preparatory to reach the final binding mode. In our simulations, the ions and the water molecules have been explicitly represented and the energetic contribution of the solvent during ligand binding evaluated. Our theoretical results provide an accurate estimate of the absolute ligand/DNA binding free energy ([Formula: see text] = -10.3 ± 0.5 kcal/mol) that we validated through steady-state fluorescence binding assays. The good agreement between the theoretical and experimental value demonstrates that FM is a most powerful method to investigate ligand/DNA interaction and can be a useful tool for the rational design also of G4 ligands.

  14. The telomeric protein TRF2 binds the ATM kinase and can inhibit the ATM-dependent DNA damage response.

    Directory of Open Access Journals (Sweden)

    Jan Karlseder

    2004-08-01

    Full Text Available The telomeric protein TRF2 is required to prevent mammalian telomeres from activating DNA damage checkpoints. Here we show that overexpression of TRF2 affects the response of the ATM kinase to DNA damage. Overexpression of TRF2 abrogated the cell cycle arrest after ionizing radiation and diminished several other readouts of the DNA damage response, including phosphorylation of Nbs1, induction of p53, and upregulation of p53 targets. TRF2 inhibited autophosphorylation of ATM on S1981, an early step in the activation of this kinase. A region of ATM containing S1981 was found to directly interact with TRF2 in vitro, and ATM immunoprecipitates contained TRF2. We propose that TRF2 has the ability to inhibit ATM activation at telomeres. Because TRF2 is abundant at chromosome ends but not elsewhere in the nucleus, this mechanism of checkpoint control could specifically block a DNA damage response at telomeres without affecting the surveillance of chromosome internal damage.

  15. Rif1 Binding and Control of Chromosome-Internal DNA Replication Origins Is Limited by Telomere Sequestration.

    Science.gov (United States)

    Hafner, Lukas; Lezaja, Aleksandra; Zhang, Xu; Lemmens, Laure; Shyian, Maksym; Albert, Benjamin; Follonier, Cindy; Nunes, Jose Manuel; Lopes, Massimo; Shore, David; Mattarocci, Stefano

    2018-04-24

    The Saccharomyces cerevisiae telomere-binding protein Rif1 plays an evolutionarily conserved role in control of DNA replication timing by promoting PP1-dependent dephosphorylation of replication initiation factors. However, ScRif1 binding outside of telomeres has never been detected, and it has thus been unclear whether Rif1 acts directly on the replication origins that it controls. Here, we show that, in unperturbed yeast cells, Rif1 primarily regulates late-replicating origins within 100 kb of a telomere. Using the chromatin endogenous cleavage ChEC-seq technique, we robustly detect Rif1 at late-replicating origins that we show are targets of its inhibitory action. Interestingly, abrogation of Rif1 telomere association by mutation of its Rap1-binding module increases Rif1 binding and origin inhibition elsewhere in the genome. Our results indicate that Rif1 inhibits replication initiation by interacting directly with origins and suggest that Rap1-dependent sequestration of Rif1 increases its effective concentration near telomeres, while limiting its action at chromosome-internal sites. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  16. DNA breaks and repair in interstitial telomere sequences: Influence of chromatin structure

    International Nuclear Information System (INIS)

    Revaud, D.

    2009-06-01

    Interstitial Telomeric Sequences (ITS) are over-involved in spontaneous and radiationinduced chromosome aberrations in chinese hamster cells. We have performed a study to investigate the origin of their instability, spontaneously or after low doses irradiation. Our results demonstrate that ITS have a particular chromatin structure: short nucleotide repeat length, less compaction of the 30 nm chromatin fiber, presence of G-quadruplex structures. These features would modulate breaks production and would favour the recruitment of alternative DNA repair mechanisms, which are prone to produce chromosome aberrations. These pathways could be at the origin of chromosome aberrations in ITS whereas NHEJ and HR Double Strand Break repair pathways are rather required for a correct repair in these regions. (author)

  17. Low-Energy Electron-Induced Strand Breaks in Telomere-Derived DNA Sequences-Influence of DNA Sequence and Topology.

    Science.gov (United States)

    Rackwitz, Jenny; Bald, Ilko

    2018-03-26

    During cancer radiation therapy high-energy radiation is used to reduce tumour tissue. The irradiation produces a shower of secondary low-energy (DNA very efficiently by dissociative electron attachment. Recently, it was suggested that low-energy electron-induced DNA strand breaks strongly depend on the specific DNA sequence with a high sensitivity of G-rich sequences. Here, we use DNA origami platforms to expose G-rich telomere sequences to low-energy (8.8 eV) electrons to determine absolute cross sections for strand breakage and to study the influence of sequence modifications and topology of telomeric DNA on the strand breakage. We find that the telomeric DNA 5'-(TTA GGG) 2 is more sensitive to low-energy electrons than an intermixed sequence 5'-(TGT GTG A) 2 confirming the unique electronic properties resulting from G-stacking. With increasing length of the oligonucleotide (i.e., going from 5'-(GGG ATT) 2 to 5'-(GGG ATT) 4 ), both the variety of topology and the electron-induced strand break cross sections increase. Addition of K + ions decreases the strand break cross section for all sequences that are able to fold G-quadruplexes or G-intermediates, whereas the strand break cross section for the intermixed sequence remains unchanged. These results indicate that telomeric DNA is rather sensitive towards low-energy electron-induced strand breakage suggesting significant telomere shortening that can also occur during cancer radiation therapy. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Oxidative stress, telomere shortening, and DNA methylation in relation to low-to-moderate occupational exposure to welding fumes.

    Science.gov (United States)

    Li, Huiqi; Hedmer, Maria; Wojdacz, Tomasz; Hossain, Mohammad Bakhtiar; Lindh, Christian H; Tinnerberg, Håkan; Albin, Maria; Broberg, Karin

    2015-10-01

    Evidence suggests that exposure to welding fumes is a risk factor for lung cancer. We examined relationships between low-to-moderate occupational exposure to particles from welding fumes and cancer-related biomarkers for oxidative stress, changes in telomere length, and alterations in DNA methylation. We enrolled 101 welders and 127 controls (all currently nonsmoking men) from southern Sweden. We performed personal sampling of respirable dust and measured 8-oxodG concentrations in urine using a simplified liquid chromatography tandem mass spectrometry method. Telomere length in peripheral blood was measured by quantitative polymerase chain reaction. Methylation status of 10 tumor suppressor genes was determined by methylation-sensitive high-resolution melting analysis. All analyses were adjusted for age, body mass index, previous smoking, passive smoking, current residence, and wood burning stove/boiler at home. Welders were exposed to respirable dust at 1.2 mg/m(3) (standard deviation, 3.3 mg/m(3); range, 0.1-19.3), whereas control exposures did not exceed 0.1 mg/m(3) (P < 0.001). Welders and controls did not differ in 8-oxodG levels (β = 1.2, P = 0.17) or relative telomere length (β = -0.053, P = 0.083) in adjusted models. Welders showed higher probability of adenomatous polyposis coli (APC) methylation in the unadjusted model (odds ratio = 14, P = 0.014), but this was not significant in the fully adjusted model (P = 0.052). Every working year as a welder was associated with 0.0066 units shorter telomeres (95% confidence interval -0.013 to -0.00053, P = 0.033). Although there were no clear associations between concentrations of respirable dust and the biomarkers, there were modest signs of associations between oxidative stress, telomere alterations, DNA methylation, and occupational exposure to low-to-moderate levels of particles. © 2015 Wiley Periodicals, Inc.

  19. Effects of Unpredictable Variable Prenatal Stress (UVPS) on Bdnf DNA Methylation and Telomere Length in the Adult Rat Brain

    Science.gov (United States)

    Blaze, Jennifer; Asok, A.; Moyer, E. L.; Roth, T. L.; Ronca, A. E.

    2015-01-01

    In utero exposure to stress can shape neurobiological and behavioral outcomes in offspring, producing vulnerability to psychopathology later in life. Animal models of prenatal stress likewise have demonstrated long-­-term alterations in brain function and behavioral deficits in offspring. For example, using a rodent model of unpredictable variable prenatal stress (UVPS), in which dams are exposed to unpredictable, variable stress across pregnancy, we have found increased body weight and anxiety-­-like behavior in adult male, but not female, offspring. DNA methylation (addition of methyl groups to cytosines which normally represses gene transcription) and changes in telomere length (TTAGGG repeats on the ends of chromosomes) are two molecular modifications that result from stress and could be responsible for the long-­-term effects of UVPS. Here, we measured methylation of brain-­-derived neurotrophic factor (bdnf), a gene important in development and plasticity, and telomere length in the brains of adult offspring from the UVPS model. Results indicate that prenatally stressed adult males have greater methylation in the medial prefrontal cortex (mPFC) compared to non-­-stressed controls, while females have greater methylation in the ventral hippocampus compared to controls. Further, prenatally stressed males had shorter telomeres than controls in the mPFC. These findings demonstrate the ability of UVPS to produce epigenetic alterations and changes in telomere length across behaviorally-­-relevant brain regions, which may have linkages to the phenotypic outcomes.

  20. Exploring the Dynamics of Propeller Loops in Human Telomeric DNA Quadruplexes Using Atomistic Simulations

    Science.gov (United States)

    2017-01-01

    We have carried out a series of extended unbiased molecular dynamics (MD) simulations (up to 10 μs long, ∼162 μs in total) complemented by replica-exchange with the collective variable tempering (RECT) approach for several human telomeric DNA G-quadruplex (GQ) topologies with TTA propeller loops. We used different AMBER DNA force-field variants and also processed simulations by Markov State Model (MSM) analysis. The slow conformational transitions in the propeller loops took place on a scale of a few μs, emphasizing the need for long simulations in studies of GQ dynamics. The propeller loops sampled similar ensembles for all GQ topologies and for all force-field dihedral-potential variants. The outcomes of standard and RECT simulations were consistent and captured similar spectrum of loop conformations. However, the most common crystallographic loop conformation was very unstable with all force-field versions. Although the loss of canonical γ-trans state of the first propeller loop nucleotide could be related to the indispensable bsc0 α/γ dihedral potential, even supporting this particular dihedral by a bias was insufficient to populate the experimentally dominant loop conformation. In conclusion, while our simulations were capable of providing a reasonable albeit not converged sampling of the TTA propeller loop conformational space, the force-field description still remained far from satisfactory. PMID:28475322

  1. Shelterin Protects Chromosome Ends by Compacting Telomeric Chromatin

    Science.gov (United States)

    Bandaria, Jigar N.; Qin, Peiwu; Berk, Veysel; Chu, Steven; Yildiz, Ahmet

    2016-01-01

    SUMMARY Telomeres, repetitive DNA sequences at chromosome ends, are shielded against the DNA damage response (DDR) by the shelterin complex. To understand how shelterin protects telomere ends, we investigated the structural organization of telomeric chromatin in human cells using super-resolution microscopy. We found that telomeres form compact globular structures through a complex network of interactions between shelterin subunits and telomeric DNA, and not by DNA methylation, histone deacetylation or histone trimethylation at telomeres and subtelomeric regions. Mutations that abrogate shelterin assembly or removal of individual subunits from telomeres cause up to a 10-fold increase in telomere volume. Decompacted telomeres become more accessible to telomere-associated proteins and accumulate DDR signals. Recompaction of telomeric chromatin using an orthogonal method displaces DDR signals from telomeres. These results reveal the chromatin remodeling activity of shelterin and demonstrate that shelterin-mediated compaction of telomeric chromatin provides robust protection of chromosome ends against the DDR machinery. PMID:26871633

  2. Telomere lengthening early in development.

    Science.gov (United States)

    Liu, Lin; Bailey, Susan M; Okuka, Maja; Muñoz, Purificación; Li, Chao; Zhou, Lingjun; Wu, Chao; Czerwiec, Eva; Sandler, Laurel; Seyfang, Andreas; Blasco, Maria A; Keefe, David L

    2007-12-01

    Stem cells and cancer cells maintain telomere length mostly through telomerase. Telomerase activity is high in male germ line and stem cells, but is low or absent in mature oocytes and cleavage stage embryos, and then high again in blastocysts. How early embryos reset telomere length remains poorly understood. Here, we show that oocytes actually have shorter telomeres than somatic cells, but their telomeres lengthen remarkably during early cleavage development. Moreover, parthenogenetically activated oocytes also lengthen their telomeres, thus the capacity to elongate telomeres must reside within oocytes themselves. Notably, telomeres also elongate in the early cleavage embryos of telomerase-null mice, demonstrating that telomerase is unlikely to be responsible for the abrupt lengthening of telomeres in these cells. Coincident with telomere lengthening, extensive telomere sister-chromatid exchange (T-SCE) and colocalization of the DNA recombination proteins Rad50 and TRF1 were observed in early cleavage embryos. Both T-SCE and DNA recombination proteins decrease in blastocyst stage embryos, whereas telomerase activity increases and telomeres elongate only slowly. We suggest that telomeres lengthen during the early cleavage cycles following fertilization through a recombination-based mechanism, and that from the blastocyst stage onwards, telomerase only maintains the telomere length established by this alternative mechanism.

  3. Telomere Restriction Fragment (TRF) Analysis.

    Science.gov (United States)

    Mender, Ilgen; Shay, Jerry W

    2015-11-20

    restriction enzyme recognition sites within TTAGGG tandem telomeric repeats, therefore digestion of genomic DNA, not telomeric DNA, with a combination of 6 base restriction endonucleases reduces genomic DNA size to less than 800 bp.

  4. Exposure to inorganic arsenic is associated with increased mitochondrial DNA copy number and longer telomere length in peripheral blood.

    Directory of Open Access Journals (Sweden)

    Syeda Shegufta Ameer

    2016-08-01

    Full Text Available Background: Exposure to inorganic arsenic (iAs through drinking water causes cancer. Alterations in mitochondrial DNA copy number (mtDNAcn and telomere length in blood have been associated with cancer risk. We elucidated if arsenic exposure alters mtDNAcn and telomere length in individuals with different arsenic metabolizing capacity.Methods: We studied two groups in the Salta province, Argentina, one in the Puna area of the Andes (N=264, 89% females and one in Chaco (N=169, 75% females. We assessed arsenic exposure as the sum of arsenic metabolites [iAs, methylarsonic acid (MMA, dimethylarsinic acid (DMA] in urine (U-As using high-performance liquid chromatography coupled with hydride generation and inductively coupled plasma mass spectrometry. Efficiency of arsenic metabolism was expressed as percentage of urinary metabolites. MtDNAcn and telomere length were determined in blood by real-time PCR. Results: Median U-As was 196 (5 - 95 percentile: 21 - 537 µg/L in Andes and 80 (5 - 95 percentile: 15 - 1637 µg/L in Chaco. The latter study group had less-efficient metabolism, with higher %iAs and %MMA in urine compared with the Andean group. U-As was significantly associated with increased mtDNAcn (log2 transformed to improve linearity in Chaco (β=0.027 per 100 µg/L, p=0.0085; adjusted for age and sex, but not in Andes (β=0.025, p=0.24. U-As was also associated with longer telomere length in Chaco (β=0.016, p=0.0066 and Andes (β=0.0075, p=0.029. In both populations, individuals with above median %iAs showed significantly higher mtDNAcn and telomere length compared with individuals with below median %iAs. Conclusions: Arsenic was associated with increased mtDNAcn and telomere length, particularly in individuals with less-efficient arsenic metabolism, a group who may have increased risk for arsenic-related cancer.

  5. DNA Amplification by Breakage/Fusion/Bridge Cycles Initiated by Spontaneous Telomere Loss in a Human Cancer Cell Line

    Directory of Open Access Journals (Sweden)

    Anthony W.l. Lo

    2002-01-01

    Full Text Available The development of genomic instability is an important step in generatingthe multiple genetic changes required for cancer. One consequence of genomic instability is the overexpression of oncogenes due to gene amplification. One mechanism for gene amplification is the breakagelfusionlbridge (B/F/Bcyclethatinvolvesthe repeated fusion and breakage of chromosomes following the loss of a telomere. B/F/B cycles have been associated with low-copy gene amplification in human cancer cells, and have been proposed to be an initiating event in high-copy gene amplification. We have found that spontaneous telomere loss on a marker chromosome 16 in a human tumor cell line results in sister chromatid fusion and prolonged periods of chromosome instability. The high rate of anaphase bridges involving chromosome 16 demonstrates that this instability results from B/F/B cycles. The amplification of subtelomeric DNA on the marker chromosome provides conclusive evidence that B/F/B cycles initiated by spontaneous telomere loss are a mechanism for gene amplification in human cancer cells.

  6. Lead Exposure Induces Telomere Instability in Human Cells.

    Directory of Open Access Journals (Sweden)

    Géraldine Pottier

    Full Text Available Lead (Pb is an important environmental contaminant due to its widespread use over many centuries. While it affects primarily every organ system of the body, the most pernicious effects of Pb are on the central nervous system leading to cognitive and behavioral modification. Despite decades of research, the mechanisms responsible for Pb toxicity remain poorly understood. Recent work has suggested that Pb exposure may have consequences on chromosomal integrity as it was shown that Pb exposure leads to the generation of γH2Ax foci, a well-established biomarker for DNA double stranded break (DSB formation. As the chromosomal localization of γH2Ax foci plays an important role in determining the molecular mechanism responsible for their formation, we examined the localization of Pb-induced foci with respect to telomeres. Indeed, short or dysfunctional telomeres (uncapped or damaged telomeres may be recognized as DSB by the DNA repair machinery, leading to "telomere-Induced Foci" (TIFs. In the current study, we show that while Pb exposure did not increase intra-chromosomal foci, it significantly induced TIFs, leading in some cases, to chromosomal abnormalities including telomere loss. The evidence suggests that these chromosomal abnormalities are likely due to perturbation of telomere replication, in particular on the lagging DNA strand. We propose a mechanism by which Pb exposure leads to the loss of telomere maintenance. As numerous studies have demonstrated a role for telomere maintenance in brain development and tissue homeostasis, our results suggest a possible mechanism for lead-induced neurotoxicity.

  7. Telomeres: Implications for Cancer Development

    Directory of Open Access Journals (Sweden)

    Aina Bernal

    2018-01-01

    Full Text Available Telomeres facilitate the protection of natural ends of chromosomes from constitutive exposure to the DNA damage response (DDR. This is most likely achieved by a lariat structure that hides the linear telomeric DNA through protein-protein and protein-DNA interactions. The telomere shortening associated with DNA replication in the absence of a compensatory mechanism culminates in unmasked telomeres. Then, the subsequent activation of the DDR will define the fate of cells according to the functionality of cell cycle checkpoints. Dysfunctional telomeres can suppress cancer development by engaging replicative senescence or apoptotic pathways, but they can also promote tumour initiation. Studies in telomere dynamics and karyotype analysis underpin telomere crisis as a key event driving genomic instability. Significant attainment of telomerase or alternative lengthening of telomeres (ALT-pathway to maintain telomere length may be permissive and required for clonal evolution of genomically-unstable cells during progression to malignancy. We summarise current knowledge of the role of telomeres in the maintenance of chromosomal stability and carcinogenesis.

  8. Fanconi anemia proteins in telomere maintenance.

    Science.gov (United States)

    Sarkar, Jaya; Liu, Yie

    2016-07-01

    Mammalian chromosome ends are protected by nucleoprotein structures called telomeres. Telomeres ensure genome stability by preventing chromosome termini from being recognized as DNA damage. Telomere length homeostasis is inevitable for telomere maintenance because critical shortening or over-lengthening of telomeres may lead to DNA damage response or delay in DNA replication, and hence genome instability. Due to their repetitive DNA sequence, unique architecture, bound shelterin proteins, and high propensity to form alternate/secondary DNA structures, telomeres are like common fragile sites and pose an inherent challenge to the progression of DNA replication, repair, and recombination apparatus. It is conceivable that longer the telomeres are, greater is the severity of such challenges. Recent studies have linked excessively long telomeres with increased tumorigenesis. Here we discuss telomere abnormalities in a rare recessive chromosomal instability disorder called Fanconi Anemia and the role of the Fanconi Anemia pathway in telomere biology. Reports suggest that Fanconi Anemia proteins play a role in maintaining long telomeres, including processing telomeric joint molecule intermediates. We speculate that ablation of the Fanconi Anemia pathway would lead to inadequate aberrant structural barrier resolution at excessively long telomeres, thereby causing replicative burden on the cell. Published by Elsevier B.V.

  9. Relationship between protein and mitochondrial DNA oxidative injury and telomere length and muscle loss in healthy elderly subjects.

    Science.gov (United States)

    Bunout, Daniel; Backhouse, Claudia; Leiva, Laura; Barrera, Gladys; Sierralta, Walter; de la Maza, María Pía; Hirsch, Sandra

    2009-01-01

    A blood sample and muscle biopsies were obtained from 54 elderly subjects. Twenty-seven subjects aged 77+/-3 years, had experienced a change in fat free mass (FFM) of +194+/-282g/year (lean body mass maintainers) and 27 subjects aged 78+/-3 years, had a change in FFM of -487+/-209g/year (lean body mass losers). Muscle biopsies were also obtained from 10 healthy subjects aged 34+/-4 years. In muscle, the ratio of mitochondrial DNA (mtDNA) to nuclear DNA (nDNA) and telomere length were assessed and deposition of 4-hydroxy-2-nonenal adducts (4HNE) was visualized by electron microscopy. In FFM maintainers, losers and young controls, the ratio of mtDNA to nDNA was 2.1 (95% confidence intervals (CI), 0.1-31.7), 1.5 (95% CI, 0.2-15.7) and 18.6 (95% CI, 2.8-46.2), respectively. 4HNE deposition was 5.9 (95% CI, 1.5-28), 4.9 (95% CI, 0.9-13) and 3.4 (95% CI, 1.1-4.6) gold particles/microm(2), respectively. Telomere length, expressed as T/S ratio, was 0.06 (95% CI, 0.01-0.16), 0.06 (95% CI, 0.03-0.27) and 0.34 (95% CI, 0.1-1.34), respectively (p<0.02 or less for all comparisons between elderly and young subjects).

  10. Stwl modifies chromatin compaction and is required to maintain DNA integrity in the presence of perturbed DNA replication

    NARCIS (Netherlands)

    Yi, X.; Vries, de H.I.; Siudeja, K.; Rana, A.; Lemstra, W.; Brunsting, J.F.; Kok, R.J.M.; Smulders, Y.M.; Schaefer, M.; Dijk, F.; Shang, Y.F.; Eggen, B.J.L.; Kampinga, H.H.; Sibon, O.C.M.

    2009-01-01

    Hydroxyurea, a well-known DNA replication inhibitor, induces cell cycle arrest and intact checkpoint functions are required to survive DNA replication stress induced by this genotoxic agent. Perturbed DNA synthesis also results in elevated levels of DNA damage. It is unclear how organisms prevent

  11. Stwl Modifies Chromatin Compaction and Is Required to Maintain DNA Integrity in the Presence of Perturbed DNA Replication

    NARCIS (Netherlands)

    Yi, Xia; Vries, Hilda I. de; Siudeja, Katarzyna; Rana, Anil; Lemstra, Willy; Brunsting, Jeanette F.; Kok, Rob M.; Smulders, Yvo M.; Schaefer, Matthias; Dijk, Freark; Shang, Yongfeng; Eggen, Bart J.L.; Kampinga, Harm H.; Sibon, Ody C.M.

    Hydroxyurea, a well-known DNA replication inhibitor, induces cell cycle arrest and intact checkpoint functions are required to survive DNA replication stress induced by this genotoxic agent. Perturbed DNA synthesis also results in elevated levels of DNA damage. It is unclear how organisms prevent

  12. Diet, nutrition and telomere length.

    Science.gov (United States)

    Paul, Ligi

    2011-10-01

    The ends of human chromosomes are protected by DNA-protein complexes termed telomeres, which prevent the chromosomes from fusing with each other and from being recognized as a double-strand break by DNA repair proteins. Due to the incomplete replication of linear chromosomes by DNA polymerase, telomeric DNA shortens with repeated cell divisions until the telomeres reach a critical length, at which point the cells enter senescence. Telomere length is an indicator of biological aging, and dysfunction of telomeres is linked to age-related pathologies like cardiovascular disease, Parkinson disease, Alzheimer disease and cancer. Telomere length has been shown to be positively associated with nutritional status in human and animal studies. Various nutrients influence telomere length potentially through mechanisms that reflect their role in cellular functions including inflammation, oxidative stress, DNA integrity, DNA methylation and activity of telomerase, the enzyme that adds the telomeric repeats to the ends of the newly synthesized DNA. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. Comparative analysis of chromosomal localization of ribosomal and telomeric DNA markers in three species of Pyrgomorphidae grasshoppers

    Directory of Open Access Journals (Sweden)

    Olesya G. Buleu

    2017-09-01

    Full Text Available The karyotypes of three species of Pyrgomorphidae grasshoppers were studied: Zonocerus elegans (Thunberg, 1815, Pyrgomorpha guentheri (Burr, 1899 and Atractomorpha lata (Mochulsky, 1866. Data on karyotypes of P. guentheri and Z. elegans are reported here for the first time. All species have karyotypes consisting of 19 acrocentric chromosomes in males and 20 acrocentric chromosomes in females (2n♂=19, NF=19; 2n♀=20, NF=20 and X0/XX sex determination system. A comparative analysis of the localization of C-heterochromatin, clusters of ribosomal DNA, and telomere repeats revealed inter-species diversity in these cytogenetic markers. These differences indicate that the karyotype divergence in the species studied is not associated with structural chromosome rearrangements, but with the evolution of repeated DNA sequences.

  14. Dynamic DNA binding, junction recognition and G4 melting activity underlie the telomeric and genome-wide roles of human CST.

    Science.gov (United States)

    Bhattacharjee, Anukana; Wang, Yongyao; Diao, Jiajie; Price, Carolyn M

    2017-12-01

    Human CST (CTC1-STN1-TEN1) is a ssDNA-binding complex that helps resolve replication problems both at telomeres and genome-wide. CST resembles Replication Protein A (RPA) in that the two complexes harbor comparable arrays of OB-folds and have structurally similar small subunits. However, the overall architecture and functions of CST and RPA are distinct. Currently, the mechanism underlying CST action at diverse replication issues remains unclear. To clarify CST mechanism, we examined the capacity of CST to bind and resolve DNA structures found at sites of CST activity. We show that CST binds preferentially to ss-dsDNA junctions, an activity that can explain the incremental nature of telomeric C-strand synthesis following telomerase action. We also show that CST unfolds G-quadruplex structures, thus providing a mechanism for CST to facilitate replication through telomeres and other GC-rich regions. Finally, smFRET analysis indicates that CST binding to ssDNA is dynamic with CST complexes undergoing concentration-dependent self-displacement. These findings support an RPA-based model where dissociation and re-association of individual OB-folds allow CST to mediate loading and unloading of partner proteins to facilitate various aspects of telomere replication and genome-wide resolution of replication stress. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  15. Structural anatomy of telomere OB proteins.

    Science.gov (United States)

    Horvath, Martin P

    2011-10-01

    Telomere DNA-binding proteins protect the ends of chromosomes in eukaryotes. A subset of these proteins are constructed with one or more OB folds and bind with G+T-rich single-stranded DNA found at the extreme termini. The resulting DNA-OB protein complex interacts with other telomere components to coordinate critical telomere functions of DNA protection and DNA synthesis. While the first crystal and NMR structures readily explained protection of telomere ends, the picture of how single-stranded DNA becomes available to serve as primer and template for synthesis of new telomere DNA is only recently coming into focus. New structures of telomere OB fold proteins alongside insights from genetic and biochemical experiments have made significant contributions towards understanding how protein-binding OB proteins collaborate with DNA-binding OB proteins to recruit telomerase and DNA polymerase for telomere homeostasis. This review surveys telomere OB protein structures alongside highly comparable structures derived from replication protein A (RPA) components, with the goal of providing a molecular context for understanding telomere OB protein evolution and mechanism of action in protection and synthesis of telomere DNA.

  16. Intramolecular telomeric G-quadruplexes dramatically inhibit DNA synthesis by replicative and translesion polymerases, revealing their potential to lead to genetic change.

    Directory of Open Access Journals (Sweden)

    Deanna N Edwards

    Full Text Available Recent research indicates that hundreds of thousands of G-rich sequences within the human genome have the potential to form secondary structures known as G-quadruplexes. Telomeric regions, consisting of long arrays of TTAGGG/AATCCC repeats, are among the most likely areas in which these structures might form. Since G-quadruplexes assemble from certain G-rich single-stranded sequences, they might arise when duplex DNA is unwound such as during replication. Coincidentally, these bulky structures when present in the DNA template might also hinder the action of DNA polymerases. In this study, single-stranded telomeric templates with the potential to form G-quadruplexes were examined for their effects on a variety of replicative and translesion DNA polymerases from humans and lower organisms. Our results demonstrate that single-stranded templates containing four telomeric GGG runs fold into intramolecular G-quadruplex structures. These intramolecular G quadruplexes are somewhat dynamic in nature and stabilized by increasing KCl concentrations and decreasing temperatures. Furthermore, the presence of these intramolecular G-quadruplexes in the template dramatically inhibits DNA synthesis by various DNA polymerases, including the human polymerase δ employed during lagging strand replication of G-rich telomeric strands and several human translesion DNA polymerases potentially recruited to sites of replication blockage. Notably, misincorporation of nucleotides is observed when certain translesion polymerases are employed on substrates containing intramolecular G-quadruplexes, as is extension of the resulting mismatched base pairs upon dynamic unfolding of this secondary structure. These findings reveal the potential for blockage of DNA replication and genetic changes related to sequences capable of forming intramolecular G-quadruplexes.

  17. Drosophila atm/telomere fusion is required for telomeric localization of HP1 and telomere position effect

    OpenAIRE

    Oikemus, Sarah R.; McGinnis, Nadine; Queiroz-Machado, Joana; Tukachinsky, Hanna; Takada, Saeko; Sunkel, Claudio E.; Brodsky, Michael H.

    2004-01-01

    Terminal deletions of Drosophila chromosomes can be stably protected from end-to-end fusion despite the absence of all telomere-associated sequences. The sequence-independent protection of these telomeres suggests that recognition of chromosome ends might contribute to the epigenetic protection of telomeres. In mammals, Ataxia Telangiectasia Mutated (ATM) is activated by DNA damage and acts through an unknown, telomerase-independent mechanism to regulate telomere length and protection. We dem...

  18. Higher-order human telomeric G-quadruplex DNA metalloenzymes enhance enantioselectivity in the Diels-Alder reaction.

    Science.gov (United States)

    Li, Yinghao; Jia, Guoqing; Wang, Changhao; Cheng, Mingpan; Li, Can

    2015-03-02

    Short human telomeric (HT) DNA sequences form single G-quadruplex (G4 ) units and exhibit structure-based stereocontrol for a series of reactions. However, for more biologically relevant higher-order HT G4 -DNAs (beyond a single G4 unit), the catalytic performances are unknown. Here, we found that higher-order HT G4 -DNA copper metalloenzymes (two or three G4 units) afford remarkably higher enantioselectivity (>90 % ee) and a five- to sixfold rate increase, compared to a single G4 unit, for the Diels-Alder reaction. Electron paramagnetic resonance (EPR) and enzymatic kinetic studies revealed that the distinct catalytic function between single and higher-order G4 -DNA copper metalloenzymes can be attributed to different Cu(II) coordination environments and substrate specificity. Our finding suggests that, like protein enzymes and ribozymes, higher-order structural organization is crucial for G4 -DNA-based catalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. A stochastic model of cell replicative senescence based on telomere shortening, oxidative stress, and somatic mutations in nuclear and mitochondrial DNA.

    Science.gov (United States)

    Sozou, P D; Kirkwood, T B

    2001-12-21

    Human diploid fibroblast cells can divide for only a limited number of times in vitro, a phenomenon known as replicative senescence or the Hayflick limit. Variability in doubling potential is observed within a clone of cells, and between two sister cells arising from a single mitotic division. This strongly suggests that the process by which cells become senescent is intrinsically stochastic. Among the various biochemical mechanisms that have been proposed to explain replicative senescence, particular interest has been focussed on the role of telomere reduction. In the absence of telomerase--an enzyme switched off in normal diploid fibro-blasts-cells lose telomeric DNA at each cell division. According to the telomere hypothesis of cell senescence, cells eventually reach a critically short telomere length and cell cycle arrest follows. In support of this concept, forced expression of telomerase in normal fibroblasts appears to prevent cell senescence. Nevertheless, the telomere hypothesis in its basic form has some difficulty in explaining the marked stochastic variations seen in the replicative lifespans of individual cells within a culture, and there is strong empirical and theoretical support for the concept that other kinds of damage may contribute to cellular ageing. We describe a stochastic network model of cell senescence in which a primary role is played by telomere reduction but in which other mechanisms (oxidative stress linked particularly to mitochondrial damage, and nuclear somatic mutations) also contribute. The model gives simulation results that are in good agreement with published data on intra-clonal variability in cell doubling potential and permits an analysis of how the various elements of the stochastic network interact. Such integrative models may aid in developing new experimental approaches aimed at unravelling the intrinsic complexity of the mechanisms contributing to human cell ageing. Copyright 2001 Academic Press.

  20. Shedding lights on the flexible-armed porphyrins: Human telomeric G4 DNA interaction and cell photocytotoxicity research.

    Science.gov (United States)

    Sun, Xiang-Yu; Zhao, Ping; Jin, Shu-Fang; Liu, Min-Chao; Wang, Xia-Hong; Huang, Yu-Min; Cheng, Zhen-Feng; Yan, Si-Qi; Li, Yan-Yu; Chen, Ya-Qing; Zhong, Yan-Mei

    2017-08-01

    DNA polymorphism exerts a fascination on a large scientific community. Without crystallographic structural data, clarification of the binding modes between G-quadruplex (G4) and ligand (complex) is a challenging job. In the present work, three porphyrin compounds with different flexible carbon chains (arms) were designed, synthesized and characterized. Their binding, folding and stabilizing abilities to human telomeric G4 DNA structures were comparatively researched. Positive charges at the end of the flexible carbon chains seem to be favorable for the DNA-porphyrin interactions, which were evidenced by the spectral results and further confirmed by the molecular docking calculations. Biological function analysis demonstrated that these porphyrins show no substantial inhibition to Hela, A549 and BEL 7402 cancer cell lines under dark while exhibit broad inhibition under visible light. This significantly enhanced photocytotoxicity relative to the dark control is an essential property of photochemotherapeutic agents. The feature of the flexible arms emerges as critical influencing factors in the cell photocytotoxicity. Moreover, an ROS-mediated mitochondrial dysfunction pathway was suggested for the cell apoptosis induced by these flexible-armed porphyrins. It is found that the porphyrins with positive charges located at the end of the flexible arms represent an exciting opportunity for photochemotherapeutic anti-cancer drug design. Copyright © 2017. Published by Elsevier B.V.

  1. Drosophila atm/telomere fusion is required for telomeric localization of HP1 and telomere position effect.

    Science.gov (United States)

    Oikemus, Sarah R; McGinnis, Nadine; Queiroz-Machado, Joana; Tukachinsky, Hanna; Takada, Saeko; Sunkel, Claudio E; Brodsky, Michael H

    2004-08-01

    Terminal deletions of Drosophila chromosomes can be stably protected from end-to-end fusion despite the absence of all telomere-associated sequences. The sequence-independent protection of these telomeres suggests that recognition of chromosome ends might contribute to the epigenetic protection of telomeres. In mammals, Ataxia Telangiectasia Mutated (ATM) is activated by DNA damage and acts through an unknown, telomerase-independent mechanism to regulate telomere length and protection. We demonstrate that the Drosophila homolog of ATM is encoded by the telomere fusion (tefu) gene. In the absence of ATM, telomere fusions occur even though telomere-specific Het-A sequences are still present. High levels of spontaneous apoptosis are observed in ATM-deficient tissues, indicating that telomere dysfunction induces apoptosis in Drosophila. Suppression of this apoptosis by p53 mutations suggests that loss of ATM activates apoptosis through a DNA damage-response mechanism. Loss of ATM reduces the levels of heterochromatin protein 1 (HP1) at telomeres and suppresses telomere position effect. We propose that recognition of chromosome ends by ATM prevents telomere fusion and apoptosis by recruiting chromatin-modifying complexes to telomeres.

  2. Co-located hAT transposable element and 5S rDNA in an interstitial telomeric sequence suggest the formation of Robertsonian fusion in armored catfish.

    Science.gov (United States)

    Glugoski, Larissa; Giuliano-Caetano, Lucia; Moreira-Filho, Orlando; Vicari, Marcelo R; Nogaroto, Viviane

    2018-04-15

    Co-located 5S rDNA genes and interstitial telomeric sites (ITS) revealed the involvement of multiple 5S rDNA clusters in chromosome rearrangements of Loricariidae. Interstitial (TTAGGG)n vestiges, in addition to telomeric sites, can coincide with locations of chromosomal rearrangements, and they are considered to be hotspots for chromosome breaks. This study aimed the molecular characterization of 5S rDNA in two Rineloricaria latirostris populations and examination of roles of 5S rDNA in breakpoint sites and its in situ localization. Rineloricaria latirostris from Brazil's Das Pedras river (2n = 46 chromosomes) presented five pairs identified using a 5S rDNA probe, in addition to a pair bearing a co-located ITS/5S rDNA. Rineloricaria latirostris from the Piumhi river (2n = 48 chromosomes) revealed two pairs containing 5S rDNA, without ITS. A 702-bp amplified sequence, using 5S rDNA primers, revealed an insertion of the hAT transposable element (TE), referred to as a degenerate 5S rDNA. Double-FISH (fluorescence in situ hybridization) demonstrated co-localization of 5S rDNA/degenerate 5S rDNA, 5S rDNA/hAT and ITS/5S rDNA from the Das Pedras river population. Piumhi river isolates possessed only 5S rDNA sites. We suggest that the degenerate 5S rDNA was generated by unequal crossing over, which was driven by invasion of hAT, establishing a breakpoint region susceptible to chromosome breakage, non-homologous recombination and Robertsonian (Rb) fusion. Furthermore, the presence of clusters of 5S rDNA at fusion points in other armored catfish species suggests its re-use and that these regions represent hotspots for evolutionary rearrangements within Loricariidae genomes. Copyright © 2018 Elsevier B.V. All rights reserved.

  3. Telomere dysfunction and chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331 (United States)

    2012-02-01

    The ends of chromosomes are composed of a short repeat sequence and associated proteins that together form a cap, called a telomere, that keeps the ends from appearing as double-strand breaks (DSBs) and prevents chromosome fusion. The loss of telomeric repeat sequences or deficiencies in telomeric proteins can result in chromosome fusion and lead to chromosome instability. The similarity between chromosome rearrangements resulting from telomere loss and those found in cancer cells implicates telomere loss as an important mechanism for the chromosome instability contributing to human cancer. Telomere loss in cancer cells can occur through gradual shortening due to insufficient telomerase, the protein that maintains telomeres. However, cancer cells often have a high rate of spontaneous telomere loss despite the expression of telomerase, which has been proposed to result from a combination of oncogene-mediated replication stress and a deficiency in DSB repair in telomeric regions. Chromosome fusion in mammalian cells primarily involves nonhomologous end joining (NHEJ), which is the major form of DSB repair. Chromosome fusion initiates chromosome instability involving breakage-fusion-bridge (B/F/B) cycles, in which dicentric chromosomes form bridges and break as the cell attempts to divide, repeating the process in subsequent cell cycles. Fusion between sister chromatids results in large inverted repeats on the end of the chromosome, which amplify further following additional B/F/B cycles. B/F/B cycles continue until the chromosome acquires a new telomere, most often by translocation of the end of another chromosome. The instability is not confined to a chromosome that loses its telomere, because the instability is transferred to the chromosome donating a translocation. Moreover, the amplified regions are unstable and form extrachromosomal DNA that can reintegrate at new locations. Knowledge concerning the factors promoting telomere loss and its consequences is

  4. Binding modes and pathway of RHPS4 to human telomeric G-quadruplex and duplex DNA probed by all-atom molecular dynamics simulations with explicit solvent.

    Science.gov (United States)

    Mulholland, Kelly; Siddiquei, Farzana; Wu, Chun

    2017-07-19

    RHPS4, a potent binder to human telomeric DNA G-quadruplex, shows high efficacy in tumor cell growth inhibition. However, it's preferential binding to DNA G-quadruplex over DNA duplex (about 10 fold) remains to be improved toward its clinical application. A high resolution structure of the single-stranded telomeric DNA G-quadruplexes, or B-DNA duplex, in complex with RHPS4 is not available yet, and the binding nature of this ligand to these DNA forms remains to be elusive. In this study, we carried out 40 μs molecular dynamics binding simulations with a free ligand to decipher the binding pathway of RHPS4 to a DNA duplex and three G-quadruplex folders (parallel, antiparallel and hybrid) of the human telomeric DNA sequence. The most stable binding mode identified for the duplex, parallel, antiparallel and hybrid G-quadruplexes is an intercalation, bottom stacking, top intercalation and bottom intercalation mode, respectively. The intercalation mode with similar binding strength to both the duplex and the G-quadruplexes, explains the lack of binding selectivity of RHPS4 to the G-quadruplex form. Therefore, a ligand modification that destabilizes the duplex intercalation mode but stabilizes the G-quadruplex intercalation mode will improve the binding selectivity toward G-quadruplex. The intercalation mode of RHPS4 to both the duplex and the antiparallel and the hybrid G-quadruplex follows a base flipping-insertion mechanism rather than an open-insertion mechanism. The groove binding, the side binding and the intercalation with flipping out of base were observed to be intermediate states before the full intercalation state with paired bases.

  5. Karyotypes, male meiosis and comparative FISH mapping of 18S ribosomal DNA and telomeric (TTAGGn repeat in eight species of true bugs (Hemiptera, Heteroptera

    Directory of Open Access Journals (Sweden)

    Snejana Grozeva

    2011-11-01

    Full Text Available Eight species belonging to five true bug families were analyzed using DAPI/CMA3-staining and fluorescence in situ hybridization (FISH with telomeric (TTAGGn and 18S rDNA probes. Standard chromosomal complements are reported for the first time for Deraeocoris rutilus (Herrich-Schäffer, 1838 (2n=30+2m+XY and D. ruber (Linnaeus, 1758 (2n=30+2m+XY from the family Miridae. Using FISH, the location of a 18S rDNA cluster was detected in these species and in five more species: Megaloceroea recticornis (Geoffroy, 1785 (2n=30+XY from the Miridae; Oxycarenus lavaterae (Fabricius, 1787 (2n=14+2m+XY from the Lygaeidae s.l.; Pyrrhocoris apterus (Linnaeus, 1758 (2n=22+X from the Pyrrhocoridae; Eurydema oleracea (Linnaeus, 1758 (2n=12+XY and Graphosoma lineatum (Linnaeus, 1758 (2n=12+XY from the Pentatomidae. The species were found to differ with respect to location of a 18S rRNA gene cluster which resides on autosomes in O. lavaterae and P. apterus, whereas it locates on sex chromosomes in other five species. The 18S rDNA location provides the first physical landmark of the genomes of the species studied. The insect consensus telomeric pentanucleotide (TTAGGn was demonstrated to be absent in all the species studied in this respect, D. rutilus, M. recticornis, Cimex lectularius Linnaeus, 1758 (Cimicidae, E. oleracea, and G. lineatum, supporting the hypothesis that this motif was lost in early evolution of the Heteroptera and secondarily replaced with another motif (yet unknown or the alternative telomerase-independent mechanisms of telomere maintenance. Dot-blot hybridization analysis of the genomic DNA from C. lectularius, Nabis sp. and O. lavaterae with (TTAGGn and six other telomeric probes likewise provided a negative result.

  6. Telomere Length Reprogramming in Embryos and Stem Cells

    Directory of Open Access Journals (Sweden)

    Keri Kalmbach

    2014-01-01

    Full Text Available Telomeres protect and cap linear chromosome ends, yet these genomic buffers erode over an organism’s lifespan. Short telomeres have been associated with many age-related conditions in humans, and genetic mutations resulting in short telomeres in humans manifest as syndromes of precocious aging. In women, telomere length limits a fertilized egg’s capacity to develop into a healthy embryo. Thus, telomere length must be reset with each subsequent generation. Although telomerase is purportedly responsible for restoring telomere DNA, recent studies have elucidated the role of alternative telomeres lengthening mechanisms in the reprogramming of early embryos and stem cells, which we review here.

  7. Atomistic picture for the folding pathway of a hybrid-1 type human telomeric DNA G-quadruplex.

    Directory of Open Access Journals (Sweden)

    Yunqiang Bian

    2014-04-01

    Full Text Available In this work we studied the folding process of the hybrid-1 type human telomeric DNA G-quadruplex with solvent and K(+ ions explicitly modeled. Enabled by the powerful bias-exchange metadynamics and large-scale conventional molecular dynamic simulations, the free energy landscape of this G-DNA was obtained for the first time and four folding intermediates were identified, including a triplex and a basically formed quadruplex. The simulations also provided atomistic pictures for the structures and cation binding patterns of the intermediates. The results showed that the structure formation and cation binding are cooperative and mutually supporting each other. The syn/anti reorientation dynamics of the intermediates was also investigated. It was found that the nucleotides usually take correct syn/anti configurations when they form native and stable hydrogen bonds with the others, while fluctuating between two configurations when they do not. Misfolded intermediates with wrong syn/anti configurations were observed in the early intermediates but not in the later ones. Based on the simulations, we also discussed the roles of the non-native interactions. Besides, the formation process of the parallel conformation in the first two G-repeats and the associated reversal loop were studied. Based on the above results, we proposed a folding pathway for the hybrid-1 type G-quadruplex with atomistic details, which is new and more complete compared with previous ones. The knowledge gained for this type of G-DNA may provide a general insight for the folding of the other G-quadruplexes.

  8. RPA-1 from Leishmania amazonensis (LaRPA-1) structurally differs from other eukaryote RPA-1 and interacts with telomeric DNA via its N-terminal OB-fold domain.

    Science.gov (United States)

    Pavani, R S; Fernandes, C; Perez, A M; Vasconcelos, E J R; Siqueira-Neto, J L; Fontes, M R; Cano, M I N

    2014-12-20

    Replication protein A-1 (RPA-1) is a single-stranded DNA-binding protein involved in DNA metabolism. We previously demonstrated the interaction between LaRPA-1 and telomeric DNA. Here, we expressed and purified truncated mutants of LaRPA-1 and used circular dichroism measurements and molecular dynamics simulations to demonstrate that the tertiary structure of LaRPA-1 differs from human and yeast RPA-1. LaRPA-1 interacts with telomeric ssDNA via its N-terminal OB-fold domain, whereas RPA from higher eukaryotes show different binding modes to ssDNA. Our results show that LaRPA-1 is evolutionary distinct from other RPA-1 proteins and can potentially be used for targeting trypanosomatid telomeres. Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  9. Local stability perturbation in DNA structure induced by chain discontinuities

    International Nuclear Information System (INIS)

    Jorcano, J.L.; Mingot, F.; Davila, C.A.

    1976-01-01

    The thermal dependence of parameter ''h'' (number of base pairs broken near to internucleotide breaks) is studied. At 25degC, 0,2 M Na + and pH 7, the ''h'' value is about 12. Far from DNA melting temperature, ''h'' is not dependent upon ionic strength and it depends very little on temperature. This behavior suggests a non cooperative, entropically driven chain unzipping from terminals. Near melting temperature, ''h'' shows a thermal dependence asymptotic to Tm, and correlated with DNA composition. It seems to correspond to the cooperative denaturation. ''h'' values have been calculated from double and single break probabilities evaluated from hydrodynamically determined molecular weight distributions. (author)

  10. Telomere Length and Mortality

    DEFF Research Database (Denmark)

    Kimura, Masayuki; Hjelmborg, Jacob V B; Gardner, Jeffrey P

    2008-01-01

    Leukocyte telomere length, representing the mean length of all telomeres in leukocytes, is ostensibly a bioindicator of human aging. The authors hypothesized that shorter telomeres might forecast imminent mortality in elderly people better than leukocyte telomere length. They performed mortality...

  11. Repair activity of oxidatively damaged DNA and telomere length in human lung epithelial cells after exposure to multi-walled carbon nanotubes

    DEFF Research Database (Denmark)

    Borghini, Andrea; Roursgaard, Martin; Andreassi, Maria Grazia

    2017-01-01

    One type of carbon nanotubes (CNTs) (MWCNT-7, from Mitsui) has been classified as probably carcinogenic to humans, however insufficient data does not warrant the same classification for other types of CNTs. Experimental data indicate that CNT exposure can result in oxidative stress and DNA damage...... the cells toward replicative senescence, assessed by attrition of telomeres. To investigate this, H2O2 and KBrO3 were used to induce DNA damage in the cells and the effect of pre-exposure to MWCNT tested for a change in repair activity inside the cells or in the extract of treated cells. The effect of MWCNT...... in cultured cells, whereas these materials appear to induce low or no mutagenicity. Therefore, the present study aimed to investigate whether in vitro exposure of cultured airway epithelial cells (A549) to multi-walled CNTs (MWCNTs) could increase the DNA repair activity of oxidatively damaged DNA and drive...

  12. A Novel Drug Delivery System for Preventing the Extension of the Telomeric Ends of DNA and Preventing the Unlimited Proliferation of Cancer Cells

    International Nuclear Information System (INIS)

    Laster, Brenda; Issacson, Carol; Msamra, Maha; Perez, Ekterina; Kost, Jospeh

    2014-01-01

    Telomerase is an enzyme present in the majority of malignant tumors. It is well-documented that radiotherapy and chemotherapy activate the enzyme telomerase that immortalizes cancer cells . Telomerase prevents the shortening of the telomeric ends of DNA that is required for cell lethality; therefore, inhibiting its activation would be a useful approach to cancer treatment. However, inhibiting telomerase activation (TA) is no easy task. Despite the plethora of new drugs synthesized as potential clinical candidates for telomerase inhibition, their success or failure in the medical clinic will probably be more a function of their mode of administration once they have demonstrated TI in the research laboratory. A major physiological barrier to TI is the absolute requirement for the inhibitor to remain continuously present in the tumor throughout the long term treatment period. This is due to both the reactivation of telomerase that occurs upon the removal of the inhibitor, and the re-lengthening of the telomeres in the absence of the inhibitor. Because the systemic i.v. administration of drugs is associated with their rapid clearance from the body, the effectiveness of the inhibitor drug would be dramatically reduced due to telomerase re-activation. Under normal conditions, when telomerase is inactive, the telomeres shorten with each cell division until such time as the cell reaches its normal life expectancy. The unrestricted proliferation of cancer cells, after treatments that activate telomerase, poses a risk for local recurrence, invasion, metastases, or even second primaries and present an issue that must be addressed. Therefore, critical for clinical success is the identification of an agent whose mechanism of action has been proven to inhibit TA and whose toxicity is negligible. Equally important is the development of a drug delivery system that assures the continuous long-term presence of the drug in the tumor. The latter criterion is required to compensate for

  13. Within the genome, long telomeres are more informative than short telomeres with respect to fitness components in a long-lived seabird

    NARCIS (Netherlands)

    Bauch, Christina; Becker, Peter H.; Verhulst, Simon

    Telomeres, DNA-protein structures at chromosome ends, shorten with age, and telomere length has been linked to age-related diseases and survival. In vitro studies revealed that the shortest telomeres trigger cell senescence, but whether the shortest telomeres are also the best biomarker of ageing is

  14. i-Motif of cytosine-rich human telomere DNA fragments containing natural base lesions

    Czech Academy of Sciences Publication Activity Database

    Dvořáková, Zuzana; Renčiuk, Daniel; Kejnovská, Iva; Školáková, Petra; Bednářová, Klára; Sagi, J.; Vorlíčková, Michaela

    2018-01-01

    Roč. 46, č. 4 (2018), s. 1624-1634 ISSN 1362-4962 R&D Projects: GA ČR(CZ) GA15-06785S; GA ČR GA17-12075S; GA ČR(CZ) GJ17-19170Y; GA MŠk EF15_003/0000477 Institutional support: RVO:68081707 Keywords : pair opening kinetics * g-quadruplex dna Subject RIV: CE - Biochemistry OBOR OECD: Biochemistry and molecular biology

  15. Conformational dynamics of the human propeller telomeric DNA quadruplex on a microsecond time scale

    Czech Academy of Sciences Publication Activity Database

    Islam, B.; Sgobba, M.; Laughton, C.; Orozco, M.; Šponer, Jiří; Neidle, S.; Haider, S.

    2013-01-01

    Roč. 41, č. 4 (2013), s. 2723-2735 ISSN 0305-1048 R&D Projects: GA ČR(CZ) GAP208/11/1822 Grant - others:GA ČR(CZ) ED1.1.00/02.0068 Program:ED Institutional support: RVO:68081707 Keywords : MOLECULAR-DYNAMICS * CRYSTAL-STRUCTURE * B-DNA Subject RIV: BO - Biophysics Impact factor: 8.808, year: 2013

  16. The association of telomere length and genetic variation in telomere biology genes.

    Science.gov (United States)

    Mirabello, Lisa; Yu, Kai; Kraft, Peter; De Vivo, Immaculata; Hunter, David J; Prescott, Jennifer; Wong, Jason Y Y; Chatterjee, Nilanjan; Hayes, Richard B; Savage, Sharon A

    2010-09-01

    Telomeres cap chromosome ends and are critical for genomic stability. Many telomere-associated proteins are important for telomere length maintenance. Recent genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) in genes encoding telomere-associated proteins (RTEL1 and TERT-CLPTM1) as markers of cancer risk. We conducted an association study of telomere length and 743 SNPs in 43 telomere biology genes. Telomere length in peripheral blood DNA was determined by Q-PCR in 3,646 participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and Nurses' Health Study. We investigated associations by SNP, gene, and pathway (functional group). We found no associations between telomere length and SNPs in TERT-CLPTM1L or RTEL1. Telomere length was not significantly associated with specific functional groups. Thirteen SNPs from four genes (MEN1, MRE11A, RECQL5, and TNKS) were significantly associated with telomere length. The strongest findings were in MEN1 (gene-based P=0.006), menin, which associates with the telomerase promoter and may negatively regulate telomerase. This large association study did not find strong associations with telomere length. The combination of limited diversity and evolutionary conservation suggest that these genes may be under selective pressure. More work is needed to explore the role of genetic variants in telomere length regulation. Published 2010 Wiley-Liss, Inc.

  17. Telomeres, telomerase and premature ovarian failure

    Directory of Open Access Journals (Sweden)

    Renata Košir Pogačnik

    2011-11-01

    Full Text Available Telomeres are specialized structures at the ends of chromosomes, consisting of six repeated nucleotides in TTAGGG sequence. Genome stability is partly maintained by the architecture of telomeres and is gradually lost as telomeres progressively shorten with each cell replication. Critically shortened telomeres are recognized by DNA repair mechanisms as DNA damage and the cell replication cycle stops. The cell eventually dies or undergoes cell apoptosis. Telomere represents a cellular marker of biological age and are therefore also called cell mitotic clock. The enzyme that counteracts telomere shortening by adding nucleotides to the 3’ end of DNA strand is called telomerase. It is composed of the RNA subunit (TR, which is special type of messenger RNA (mRNA, the catalytic protein subunit (TERT, which works as a reverse transcriptase and numerous additional proteins. Telomerase is active in some germline, epithelial and haemopoietic cells, but in most somatic cells the activity is undetectable. In literature, the length of telomeres is closely connected with premature ovarian failure (POF. POF is generally defined as the onset of menopause before the age of 40. The causes of disease are genetical, autoimmune, iatrogenic or if we cannot establish the cause – idiopathic. A lot of studies examined correlation between idiopathic POF, length of telomeres and telomerase activity. The studies mostly show that women with POF have shortened telomeres and decreased activity of telomerase as compared to healthy women.

  18. Characterization of oxidative guanine damage and repair in mammalian telomeres.

    Directory of Open Access Journals (Sweden)

    Zhilong Wang

    2010-05-01

    Full Text Available 8-oxo-7,8-dihydroguanine (8-oxoG and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG are among the most common oxidative DNA lesions and are substrates for 8-oxoguanine DNA glycosylase (OGG1-initiated DNA base excision repair (BER. Mammalian telomeres consist of triple guanine repeats and are subject to oxidative guanine damage. Here, we investigated the impact of oxidative guanine damage and its repair by OGG1 on telomere integrity in mice. The mouse cells were analyzed for telomere integrity by telomere quantitative fluorescence in situ hybridization (telomere-FISH, by chromosome orientation-FISH (CO-FISH, and by indirect immunofluorescence in combination with telomere-FISH and for oxidative base lesions by Fpg-incision/Southern blot assay. In comparison to the wild type, telomere lengthening was observed in Ogg1 null (Ogg1(-/- mouse tissues and primary embryonic fibroblasts (MEFs cultivated in hypoxia condition (3% oxygen, whereas telomere shortening was detected in Ogg1(-/- mouse hematopoietic cells and primary MEFs cultivated in normoxia condition (20% oxygen or in the presence of an oxidant. In addition, telomere length abnormalities were accompanied by altered telomere sister chromatid exchanges, increased telomere single- and double-strand breaks, and preferential telomere lagging- or G-strand losses in Ogg1(-/- mouse cells. Oxidative guanine lesions were increased in telomeres in Ogg1(-/- mice with aging and primary MEFs cultivated in 20% oxygen. Furthermore, oxidative guanine lesions persisted at high level in Ogg1(-/- MEFs after acute exposure to hydrogen peroxide, while they rapidly returned to basal level in wild-type MEFs. These findings indicate that oxidative guanine damage can arise in telomeres where it affects length homeostasis, recombination, DNA replication, and DNA breakage repair. Our studies demonstrate that BER pathway is required in repairing oxidative guanine damage in telomeres and maintaining telomere integrity

  19. Human telomere sequence DNA in water-free and high-viscosity solvents: G-quadruplex folding governed by Kramers rate theory.

    Science.gov (United States)

    Lannan, Ford M; Mamajanov, Irena; Hud, Nicholas V

    2012-09-19

    Structures formed by human telomere sequence (HTS) DNA are of interest due to the implication of telomeres in the aging process and cancer. We present studies of HTS DNA folding in an anhydrous, high viscosity deep eutectic solvent (DES) comprised of choline choride and urea. In this solvent, the HTS DNA forms a G-quadruplex with the parallel-stranded ("propeller") fold, consistent with observations that reduced water activity favors the parallel fold, whereas alternative folds are favored at high water activity. Surprisingly, adoption of the parallel structure by HTS DNA in the DES, after thermal denaturation and quick cooling to room temperature, requires several months, as opposed to less than 2 min in an aqueous solution. This extended folding time in the DES is, in part, due to HTS DNA becoming kinetically trapped in a folded state that is apparently not accessed in lower viscosity solvents. A comparison of times required for the G-quadruplex to convert from its aqueous-preferred folded state to its parallel fold also reveals a dependence on solvent viscosity that is consistent with Kramers rate theory, which predicts that diffusion-controlled transitions will slow proportionally with solvent friction. These results provide an enhanced view of a G-quadruplex folding funnel and highlight the necessity to consider solvent viscosity in studies of G-quadruplex formation in vitro and in vivo. Additionally, the solvents and analyses presented here should prove valuable for understanding the folding of many other nucleic acids and potentially have applications in DNA-based nanotechnology where time-dependent structures are desired.

  20. Telomere length maintenance--an ALTernative mechanism.

    Science.gov (United States)

    Royle, N J; Foxon, J; Jeyapalan, J N; Mendez-Bermudez, A; Novo, C L; Williams, J; Cotton, V E

    2008-01-01

    The Alternative Lengthening of Telomeres (ALT) mechanism is utilised by approximately 10% of human tumours and a higher proportion of some types of sarcomas. ALT+ cell lines and tumours show heterogeneous telomere length, extra-chromosomal circular and linear telomeric DNA, ALT associated promyelocytic bodies (APBs), a high frequency of post-replication exchanges in telomeres (designated as telomere-sister chromatid exchanges, T-SCE) and high instability at a GC-rich minisatellite, MS32 (D1S8). It is clear that there is a link between the minisatellite instability and the mechanism that underpins ALT, however currently the nature of this relationship is uncertain. Single molecule analysis of telomeric DNA from ALT+ cell lines and tumours has revealed complex telomere mutations that have not been seen in cell lines or tumours that express telomerase. These complex telomere mutations cannot be explained by T-SCE but must arise by another inter-molecular process. The break-induced replication (BIR) model that may explain the observed high frequency of T-SCE and the presence of complex telomere mutations is reviewed. Copyright 2008 S. Karger AG, Basel.

  1. HOT1 is a mammalian direct telomere repeat-binding protein contributing to telomerase recruitment

    NARCIS (Netherlands)

    Kappei, D.; Butter, F.; Benda, C.; Scheibe, M.; Draskovic, Irena; Stevense, M.; Novo, C.L.; Basquin, C.; Araki, M.; Araki, K.; Krastev, D.B.; Kittler, R.; Jessberger, R.; Londono-Vallejo, J.A.; Mann, M.; Buchholz, F.

    2013-01-01

    Telomeres are repetitive DNA structures that, together with the shelterin and the CST complex, protect the ends of chromosomes. Telomere shortening is mitigated in stem and cancer cells through the de novo addition of telomeric repeats by telomerase. Telomere elongation requires the delivery of the

  2. Assessing Telomere Length Using Surface Enhanced Raman Scattering

    Science.gov (United States)

    Zong, Shenfei; Wang, Zhuyuan; Chen, Hui; Cui, Yiping

    2014-11-01

    Telomere length can provide valuable insight into telomeres and telomerase related diseases, including cancer. Here, we present a brand-new optical telomere length measurement protocol using surface enhanced Raman scattering (SERS). In this protocol, two single strand DNA are used as SERS probes. They are labeled with two different Raman molecules and can specifically hybridize with telomeres and centromere, respectively. First, genome DNA is extracted from cells. Then the telomere and centromere SERS probes are added into the genome DNA. After hybridization with genome DNA, excess SERS probes are removed by magnetic capturing nanoparticles. Finally, the genome DNA with SERS probes attached is dropped onto a SERS substrate and subjected to SERS measurement. Longer telomeres result in more attached telomere probes, thus a stronger SERS signal. Consequently, SERS signal can be used as an indicator of telomere length. Centromere is used as the inner control. By calibrating the SERS intensity of telomere probe with that of the centromere probe, SERS based telomere measurement is realized. This protocol does not require polymerase chain reaction (PCR) or electrophoresis procedures, which greatly simplifies the detection process. We anticipate that this easy-operation and cost-effective protocol is a fine alternative for the assessment of telomere length.

  3. A Molecular Toolbox to Engineer Site-Specific DNA Replication Perturbation.

    Science.gov (United States)

    Larsen, Nicolai B; Hickson, Ian D; Mankouri, Hocine W

    2018-01-01

    Site-specific arrest of DNA replication is a useful tool for analyzing cellular responses to DNA replication perturbation. The E. coli Tus-Ter replication barrier can be reconstituted in eukaryotic cells as a system to engineer an unscheduled collision between a replication fork and an "alien" impediment to DNA replication. To further develop this system as a versatile tool, we describe a set of reagents and a detailed protocol that can be used to engineer Tus-Ter barriers into any locus in the budding yeast genome. Because the Tus-Ter complex is a bipartite system with intrinsic DNA replication-blocking activity, the reagents and protocols developed and validated in yeast could also be optimized to engineer site-specific replication fork barriers into other eukaryotic cell types.

  4. Tus-Ter as a tool to study site-specific DNA replication perturbation in eukaryotes

    DEFF Research Database (Denmark)

    Larsen, Nicolai B; Hickson, Ian D; Mankouri, Hocine W

    2014-01-01

    The high-affinity binding of the Tus protein to specific 21-bp sequences, called Ter, causes site-specific, and polar, DNA replication fork arrest in E coli. The Tus-Ter complex serves to coordinate DNA replication with chromosome segregation in this organism. A number of recent and ongoing studies...... have demonstrated that Tus-Ter can be used as a heterologous tool to generate site-specific perturbation of DNA replication when reconstituted in eukaryotes. Here, we review these recent findings and explore the molecular mechanism by which Tus-Ter mediates replication fork (RF) arrest in the budding...... yeast, S. cerevisiae. We propose that Tus-Ter is a versatile, genetically tractable, and regulatable RF blocking system that can be utilized for disrupting DNA replication in a diverse range of host cells....

  5. Tus-Ter as a tool to study site-specific DNA replication perturbation in eukaryotes.

    Science.gov (United States)

    Larsen, Nicolai B; Hickson, Ian D; Mankouri, Hocine W

    2014-01-01

    The high-affinity binding of the Tus protein to specific 21-bp sequences, called Ter, causes site-specific, and polar, DNA replication fork arrest in E coli. The Tus-Ter complex serves to coordinate DNA replication with chromosome segregation in this organism. A number of recent and ongoing studies have demonstrated that Tus-Ter can be used as a heterologous tool to generate site-specific perturbation of DNA replication when reconstituted in eukaryotes. Here, we review these recent findings and explore the molecular mechanism by which Tus-Ter mediates replication fork (RF) arrest in the budding yeast, S. cerevisiae. We propose that Tus-Ter is a versatile, genetically tractable, and regulatable RF blocking system that can be utilized for disrupting DNA replication in a diverse range of host cells.

  6. A Molecular Toolbox to Engineer Site-Specific DNA Replication Perturbation

    DEFF Research Database (Denmark)

    Larsen, Nicolai B; Hickson, Ian D; Mankouri, Hocine W

    2018-01-01

    " impediment to DNA replication. To further develop this system as a versatile tool, we describe a set of reagents and a detailed protocol that can be used to engineer Tus-Ter barriers into any locus in the budding yeast genome. Because the Tus-Ter complex is a bipartite system with intrinsic DNA replication......Site-specific arrest of DNA replication is a useful tool for analyzing cellular responses to DNA replication perturbation. The E. coli Tus-Ter replication barrier can be reconstituted in eukaryotic cells as a system to engineer an unscheduled collision between a replication fork and an "alien......-blocking activity, the reagents and protocols developed and validated in yeast could also be optimized to engineer site-specific replication fork barriers into other eukaryotic cell types....

  7. Drosophila cell cycle under arrest: uncapped telomeres plead guilty.

    Science.gov (United States)

    Cenci, Giovanni

    2009-04-01

    Telomeres are specialized structures that protect chromosome ends from degradation and fusion events. In most organisms, telomeres consist of short, repetitive G-rich sequences added to chromosome ends by a reverse transcriptase with an internal RNA template, called telomerase. Specific DNA-binding protein complexes associate with telomeric sequences preventing chromosome ends from being recognized as DNA double strand breaks (DSBs). Telomeres that lose their cap activate the DNA damage response (DDR) likewise DSBs and, if inappropriately repaired, generate telomeric fusions, which eventually lead to genome instability. In Drosophila there is not telomerase, and telomere length is maintained by transposition of three specialized retroelements. However, fly telomeres are protected by multi protein complexes like their yeast and vertebrate counterparts; these complexes bind chromosome ends in a sequence-independent fashion and are required to prevent checkpoint activation and end-to-end fusion. Uncapped Drosophila telomeres elicit a DDR just as dysfunctional human telomeres. Most interestingly, uncapped Drosophila telomeres also activate the spindle assembly checkpoint (SAC) by recruiting the SAC kinase BubR1. BubR1 accumulations at chromosome ends trigger the SAC that inhibits the metaphase-to-anaphase transition. These findings, reviewed here, highlight an intriguing and unsuspected connection between telomeres and cell cycle regulation, providing a clue to understand human telomere function.

  8. Detection of perturbation phases and developmental stages in organisms from DNA microarray time series data.

    Directory of Open Access Journals (Sweden)

    Marianne Rooman

    Full Text Available Available DNA microarray time series that record gene expression along the developmental stages of multicellular eukaryotes, or in unicellular organisms subject to external perturbations such as stress and diauxie, are analyzed. By pairwise comparison of the gene expression profiles on the basis of a translation-invariant and scale-invariant distance measure corresponding to least-rectangle regression, it is shown that peaks in the average distance values are noticeable and are localized around specific time points. These points systematically coincide with the transition points between developmental phases or just follow the external perturbations. This approach can thus be used to identify automatically, from microarray time series alone, the presence of external perturbations or the succession of developmental stages in arbitrary cell systems. Moreover, our results show that there is a striking similarity between the gene expression responses to these a priori very different phenomena. In contrast, the cell cycle does not involve a perturbation-like phase, but rather continuous gene expression remodeling. Similar analyses were conducted using three other standard distance measures, showing that the one we introduced was superior. Based on these findings, we set up an adapted clustering method that uses this distance measure and classifies the genes on the basis of their expression profiles within each developmental stage or between perturbation phases.

  9. The Escherichia coli Tus-Ter replication fork barrier causes site-specific DNA replication perturbation in yeast

    DEFF Research Database (Denmark)

    Larsen, Nicolai B; Sass, Ehud; Suski, Catherine

    2014-01-01

    Replication fork (RF) pausing occurs at both 'programmed' sites and non-physiological barriers (for example, DNA adducts). Programmed RF pausing is required for site-specific DNA replication termination in Escherichia coli, and this process requires the binding of the polar terminator protein, Tus...... as a versatile, site-specific, heterologous DNA replication-perturbing system, with a variety of potential applications....

  10. Expression of Telomere-Associated Proteins is Interdependent to Stabilize Native Telomere Structure and Telomere Dysfunction by G-Quadruplex Ligand Causes TERRA Upregulation.

    Science.gov (United States)

    Sadhukhan, Ratan; Chowdhury, Priyanka; Ghosh, Sourav; Ghosh, Utpal

    2018-06-01

    Telomere DNA can form specialized nucleoprotein structure with telomere-associated proteins to hide free DNA ends or G-quadruplex structures under certain conditions especially in presence of G-quadruplex ligand. Telomere DNA is transcribed to form non-coding telomere repeat-containing RNA (TERRA) whose biogenesis and function is poorly understood. Our aim was to find the role of telomere-associated proteins and telomere structures in TERRA transcription. We silenced four [two shelterin (TRF1, TRF2) and two non-shelterin (PARP-1, SLX4)] telomere-associated genes using siRNA and verified depletion in protein level. Knocking down of one gene modulated expression of other telomere-associated genes and increased TERRA from 10q, 15q, XpYp and XqYq chromosomes in A549 cells. Telomere was destabilized or damaged by G-quadruplex ligand pyridostatin (PDS) and bleomycin. Telomere dysfunction-induced foci (TIFs) were observed for each case of depletion of proteins, treatment with PDS or bleomycin. TERRA level was elevated by PDS and bleomycin treatment alone or in combination with depletion of telomere-associated proteins.

  11. Mice with Pulmonary Fibrosis Driven by Telomere Dysfunction

    Directory of Open Access Journals (Sweden)

    Juan M. Povedano

    2015-07-01

    Full Text Available Idiopathic pulmonary fibrosis (IPF is a degenerative disease of the lungs with an average survival post-diagnosis of 2–3 years. New therapeutic targets and treatments are necessary. Mutations in components of the telomere-maintenance enzyme telomerase or in proteins important for telomere protection are found in both familial and sporadic IPF cases. However, the lack of mouse models that faithfully recapitulate the human disease has hampered new advances. Here, we generate two independent mouse models that develop IPF owing to either critically short telomeres (telomerase-deficient mice or severe telomere dysfunction in the absence of telomere shortening (mice with Trf1 deletion in type II alveolar cells. We show that both mouse models develop pulmonary fibrosis through induction of telomere damage, thus providing proof of principle of the causal role of DNA damage stemming from dysfunctional telomeres in IPF development and identifying telomeres as promising targets for new treatments.

  12. Analysis of α-particle induced incomplete chromosome aberrations, using pan-centro metric and pan-telomeric DNA probes

    International Nuclear Information System (INIS)

    Mestres, M.; Schmid, E.; Stephan, G.; Barrios, L.; Caballin, M. R.; Barquinero, J. F.

    2004-01-01

    The aim of the present study has been the evaluation of the incompleteness of α-particle induced chromosome aberrations by the simultaneous detection of all centromeres and telomeres present in human lymphocytes. For this purpose attached lymphocytes were irradiated at doses of 0.2, 0.5,0.7 and 1 Gy in a ''241Am source. FISH techniques were applied using pan-centromeric and pan-telomeric probes. All abnormal cells were digitalised and analysed using a Cytovision FISH workstation. A total of 378 incomplete chromosomes plus incomplete acentrics was found. Cases with more than 92 telomeres were not detected. The ratio between total incomplete elements and multicentrics was 1.00. The total number of acentric fragments was 822; 57% of then were complete fragments ace (+.+), 26% incomplete fragments ace (+,-), and 17% interstitial fragment ace (-.-). The percentage of incomplete aberrations is higher after high-LET than described for low-LET exposure. The results seem to indicate that compared to low-LET. after α-particle exposure it is more likely to repair the centromere-containing elements. (Author) 30 refs

  13. RPA and POT1: friends or foes at telomeres?

    Science.gov (United States)

    Flynn, Rachel Litman; Chang, Sandy; Zou, Lee

    2012-02-15

    Telomere maintenance in cycling cells relies on both DNA replication and capping by the protein complex shelterin. Two single-stranded DNA (ssDNA)-binding proteins, replication protein A (RPA) and protection of telomere 1 (POT1) play critical roles in DNA replication and telomere capping, respectively. While RPA binds to ssDNA in a non-sequence-specific manner, POT1 specifically recognizes singlestranded TTAGGG telomeric repeats. Loss of POT1 leads to aberrant accumulation of RPA at telomeres and activation of the ataxia telangiectasia and Rad3-related kinase (ATR)-mediated checkpoint response, suggesting that POT1 antagonizes RPA binding to telomeric ssDNA. The requirement for both POT1 and RPA in telomere maintenance and the antagonism between the two proteins raises the important question of how they function in concert on telomeric ssDNA. Two interesting models were proposed by recent studies to explain the regulation of POT1 and RPA at telomeres. Here, we discuss how these models help unravel the coordination, and also the antagonism, between POT1 and RPA during the cell cycle.

  14. Effect of Wortmannin on the repair profiles of DNA double-strand breaks in the whole genome and in interstitial telomeric sequences of Chinese hamster cells

    International Nuclear Information System (INIS)

    Losada, Raquel; Rivero, Maria Teresa; Slijepcevic, Predrag; Goyanes, Vicente; Fernandez, Jose Luis

    2005-01-01

    The DNA breakage detection-fluorescence in situ hybridization (DBD-FISH) procedure was applied to analyze the effect of Wortmannin (WM) in the rejoining kinetics of ionizing radiation-induced DNA double-strand breaks (DSBs) in the whole genome and in the long interstitial telomeric repeat sequence (ITRS) blocks from Chinese hamster cell lines. The results indicate that the ITRS blocks from wild-type Chinese hamster cell lines, CHO9 and V79B, exhibit a slower initial rejoining rate of ionizing radiation-induced DSBs than the genome overall. Neither Rad51C nor the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) activities, involved in homologous recombination (HR) and in non-homologous end-joining (NHEJ) pathways of DSB repair respectively, influenced the rejoining kinetics within ITRS in contrast to DNA sequences in the whole genome. Nevertheless, DSB removal rate within ITRS was decreased in the absence of Ku86 activity, though at a lower affectation level than in the whole genome, thus homogenizing both rejoining kinetics rates. WM treatment slowed down the DSB rejoining kinetics rate in ITRS, this effect being more pronounced in the whole genome, resulting in a similar pattern to that of the Ku86 deficient cells. In fact, no WM effect was detected in the Ku86 deficient Chinese hamster cells, so probably WM does not add further impairment in DSB rejoining than that resulted as a consequence of absence of Ku activity. The same slowing effect was also observed after treatment of Rad51C and DNA-PKcs defective hamster cells by WM, suggesting that: (1) there is no potentiation of the HR when the NHEJ is impaired by WM, either in the whole genome or in the ITRS, and (2) that this impairment may probably involve more targets than DNA-PKcs. These results suggest that there is an intragenomic heterogeneity in DSB repair, as well as in the effect of WM on this process

  15. Disordering of human telomeric G-quadruplex with novel antiproliferative anthrathiophenedione.

    Directory of Open Access Journals (Sweden)

    Dmitry Kaluzhny

    Full Text Available Linear heteroareneanthracenediones have been shown to interfere with DNA functions, thereby causing death of human tumor cells and their drug resistant counterparts. Here we report the interaction of our novel antiproliferative agent 4,11-bis[(2-{[acetimido]amino}ethylamino]anthra[2,3-b]thiophene-5,10-dione with telomeric DNA structures studied by isothermal titration calorimetry, circular dichroism and UV absorption spectroscopy. New compound demonstrated a high affinity (K(ass∼10⁶ M⁻¹ for human telomeric antiparallel quadruplex d(TTAGGG₄ and duplex d(TTAGGG₄∶d(CCCTAA₄. Importantly, a ∼100-fold higher affinity was determined for the ligand binding to an unordered oligonucleotide d(TTAGGG TTAGAG TTAGGG TTAGGG unable to form quadruplex structures. Moreover, in the presence of Na+ the compound caused dramatic conformational perturbation of the telomeric G-quadruplex, namely, almost complete disordering of G-quartets. Disorganization of a portion of G-quartets in the presence of K+ was also detected. Molecular dynamics simulations were performed to illustrate how the binding of one molecule of the ligand might disrupt the G-quartet adjacent to the diagonal loop of telomeric G-quadruplex. Our results provide evidence for a non-trivial mode of alteration of G-quadruplex structure by tentative antiproliferative drugs.

  16. Mutant p53 perturbs DNA replication checkpoint control through TopBP1 and Treslin.

    Science.gov (United States)

    Liu, Kang; Lin, Fang-Tsyr; Graves, Joshua D; Lee, Yu-Ju; Lin, Weei-Chin

    2017-05-09

    Accumulating evidence supports the gain-of-function of mutant forms of p53 (mutp53s). However, whether mutp53 directly perturbs the DNA replication checkpoint remains unclear. Previously, we have demonstrated that TopBP1 forms a complex with mutp53s and mediates their gain-of-function through NF-Y and p63/p73. Akt phosphorylates TopBP1 and induces its oligomerization, which inhibits its ATR-activating function. Here we show that various contact and conformational mutp53s bypass Akt to induce TopBP1 oligomerization and attenuate ATR checkpoint response during replication stress. The effect on ATR response caused by mutp53 can be exploited in a synthetic lethality strategy, as depletion of another ATR activator, DNA2, in mutp53-R273H-expressing cancer cells renders cells hypersensitive to cisplatin. Expression of mutp53-R273H also makes cancer cells more sensitive to DNA2 depletion or DNA2 inhibitors. In addition to ATR-activating function during replication stress, TopBP1 interacts with Treslin in a Cdk-dependent manner to initiate DNA replication during normal growth. We find that mutp53 also interferes with TopBP1 replication function. Several contact, but not conformational, mutp53s enhance the interaction between TopBP1 and Treslin and promote DNA replication despite the presence of a Cdk2 inhibitor. Together, these data uncover two distinct mechanisms by which mutp53 enhances DNA replication: ( i ) Both contact and conformational mutp53s can bind TopBP1 and attenuate the checkpoint response to replication stress, and ( ii ) during normal growth, contact (but not conformational) mutp53s can override the Cdk2 requirement to promote replication by facilitating the TopBP1/Treslin interaction.

  17. Male and female meiosis in the mountain scorpion Zabius fuscus (Scorpiones, Buthidae): heterochromatin, rDNA and TTAGG telomeric repeats.

    Science.gov (United States)

    Adilardi, Renzo Sebastián; Ojanguren-Affilastro, Andrés Alejandro; Mattoni, Camilo Iván; Mola, Liliana María

    2015-08-01

    All cytogenetically studied scorpions present male achiasmatic meiosis and lack heteromorphic sex chromosomes. In contrast, information about female meiosis in scorpions is scarce due to the difficulty of finding meiotic cells. The genus Zabius includes three described species and no chromosome studies have been performed on it until now. We analyzed the constitutive heterochromatin distribution, NORs and telomeric sequences in mitosis and meiosis of males and females of different populations of Zabius fuscus. All specimens presented 2n = 18 holokinetic chromosomes that gradually decreased in size. Male meiosis presented nine bivalents and a polymorphism for one reciprocal translocation in one population. Telomeric signals were detected at every terminal region, confirming also the presence of a (TTAGG) n motif in Buthidae. Constitutive heterochromatin was found in three chromosome pairs at a terminal region; moreover, NORs were embedded in the heterochromatic region of the largest pair. Chromosome size and landmarks allowed us to propose the chromosomes involved in the rearrangement. In four females, cells at different prophase I stages were analyzed. We describe a diffuse stage and the presence of ring-shaped bivalents. We discuss the possible origin of these bivalents in the framework of chiasmatic or achiasmatic female meiosis. These results contribute to increase the scarce evidence of female meiosis in scorpions and raise new questions about its mechanism.

  18. Determinants for Tight and Selective Binding of a Medicinal Dicarbene Gold(I) Complex to a Telomeric DNA G-Quadruplex: a Joint ESI MS and XRD Investigation.

    Science.gov (United States)

    Bazzicalupi, Carla; Ferraroni, Marta; Papi, Francesco; Massai, Lara; Bertrand, Benoît; Messori, Luigi; Gratteri, Paola; Casini, Angela

    2016-03-18

    The dicarbene gold(I) complex [Au(9-methylcaffein-8-ylidene)2 ]BF4 is an exceptional organometallic compound of profound interest as a prospective anticancer agent. This gold(I) complex was previously reported to be highly cytotoxic toward various cancer cell lines in vitro and behaves as a selective G-quadruplex stabilizer. Interactions of the gold complex with various telomeric DNA models have been analyzed by a combined ESI MS and X-ray diffraction (XRD) approach. ESI MS measurements confirmed formation of stable adducts between the intact gold(I) complex and Tel 23 DNA sequence. The crystal structure of the adduct formed between [Au(9-methylcaffein-8-ylidene)2 ](+) and Tel 23 DNA G-quadruplex was solved. Tel 23 maintains a characteristic propeller conformation while binding three gold(I) dicarbene moieties at two distinct sites. Stacking interactions appear to drive noncovalent binding of the gold(I) complex. The structural basis for tight gold(I) complex/G-quadruplex recognition and its selectivity are described. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Measurement of Telomere Length in Colorectal Cancers for Improved Molecular Diagnosis

    Directory of Open Access Journals (Sweden)

    Eric Le Balc’h

    2017-08-01

    Full Text Available All tumors have in common to reactivate a telomere maintenance mechanism to allow for unlimited proliferation. On the other hand, genetic instability found in some tumors can result from the loss of telomeres. Here, we measured telomere length in colorectal cancers (CRCs using TRF (Telomere Restriction Fragment analysis. Telomeric DNA content was also quantified as the ratio of total telomeric (TTAGGG sequences over that of the invariable Alu sequences. In most of the 125 CRCs analyzed, there was a significant diminution in telomere length compared with that in control healthy tissue. Only 34 tumors exhibited no telomere erosion and, in some cases, a slight telomere lengthening. Telomere length did not correlate with age, gender, tumor stage, tumor localization or stage of tumor differentiation. In addition, while telomere length did not correlate with the presence of a mutation in BRAF (V-raf murine sarcoma viral oncogene homolog B, PIK3CA (phosphatidylinositol 3-kinase catalytic subunit, or MSI status, it was significantly associated with the occurrence of a mutation in KRAS. Interestingly, we found that the shorter the telomeres in healthy tissue of a patient, the larger an increase in telomere length in the tumor. Our study points to the existence of two types of CRCs based on telomere length and reveals that telomere length in healthy tissue might influence telomere maintenance mechanisms in the tumor.

  20. Short telomeres: from dyskeratosis congenita to sporadic aplastic anemia and malignancy.

    Science.gov (United States)

    Gramatges, Maria M; Bertuch, Alison A

    2013-12-01

    Telomeres are DNA-protein structures that form a protective cap on chromosome ends. As such, they prevent the natural ends of linear chromosomes from being subjected to DNA repair activities that would result in telomere fusion, degradation, or recombination. Both the DNA and protein components of the telomere are required for this essential function, because insufficient telomeric DNA length, loss of the terminal telomeric DNA structure, or deficiency of key telomere-associated factors may elicit a DNA damage response and result in cellular senescence or apoptosis. In the setting of failed checkpoint mechanisms, such DNA-protein defects can also lead to genomic instability through telomere fusions or recombination. Thus, as shown in both model systems and in humans, defects in telomere biology are implicated in cellular and organismal aging as well as in tumorigenesis. Bone marrow failure and malignancy are 2 life-threatening disease manifestations in the inherited telomere biology disorder dyskeratosis congenita. We provide an overview of basic telomere structure and maintenance. We outline the telomere biology defects observed in dyskeratosis congenita, focusing on recent discoveries in this field. Last, we review the evidence of how telomere biology may impact sporadic aplastic anemia and the risk for various cancers. Copyright © 2013 Mosby, Inc. All rights reserved.

  1. Elucidate the Mechanism of Telomere Maintenance in STAG2 Mutated Tumor Cells

    Science.gov (United States)

    2017-12-01

    normal human cells.; Cancer Research; 2017. Nothing to report. Tumor and Stem Cell Biology Loss of Tumor Suppressor STAG2 Promotes Telomere...total G- strand telomeric DNA. Themean telomere lengthwas determinedusing Telometric (Fox Chase Cancer Center). C-circle assay The C-circle assay was...bodies (APB; ref. 36) and partially single- stranded telomeric extrachromosomal (CCCTAA) DNA circles (C-circles; ref. 27), and the absence of telomerase

  2. RTEL1: an essential helicase for telomere maintenance and the regulation of homologous recombination

    OpenAIRE

    Uringa, Evert-Jan; Youds, Jillian L.; Lisaingo, Kathleen; Lansdorp, Peter M.; Boulton, Simon J.

    2010-01-01

    Telomere maintenance and DNA repair are crucial processes that protect the genome against instability. RTEL1, an essential iron–sulfur cluster-containing helicase, is a dominant factor that controls telomere length in mice and is required for telomere integrity. In addition, RTEL1 promotes synthesis-dependent strand annealing to direct DNA double-strand breaks into non-crossover outcomes during mitotic repair and in meiosis. Here, we review the role of RTEL1 in telomere maintenance and homolo...

  3. Telomere Length Dynamics and the Evolution of Cancer Genome Architecture

    Directory of Open Access Journals (Sweden)

    Kez Cleal

    2018-02-01

    Full Text Available Telomeres are progressively eroded during repeated rounds of cell division due to the end replication problem but also undergo additional more substantial stochastic shortening events. In most cases, shortened telomeres induce a cell-cycle arrest or trigger apoptosis, although for those cells that bypass such signals during tumour progression, a critical length threshold is reached at which telomere dysfunction may ensue. Dysfunction of the telomere nucleoprotein complex can expose free chromosome ends to the DNA double-strand break (DSB repair machinery, leading to telomere fusion with both telomeric and non-telomeric loci. The consequences of telomere fusions in promoting genome instability have long been appreciated through the breakage–fusion–bridge (BFB cycle mechanism, although recent studies using high-throughput sequencing technologies have uncovered evidence of involvement in a wider spectrum of genomic rearrangements including chromothripsis. A critical step in cancer progression is the transition of a clone to immortality, through the stabilisation of the telomere repeat array. This can be achieved via the reactivation of telomerase, or the induction of the alternative lengthening of telomeres (ALT pathway. Whilst telomere dysfunction may promote genome instability and tumour progression, by limiting the replicative potential of a cell and enforcing senescence, telomere shortening can act as a tumour suppressor mechanism. However, the burden of senescent cells has also been implicated as a driver of ageing and age-related pathology, and in the promotion of cancer through inflammatory signalling. Considering the critical role of telomere length in governing cancer biology, we review questions related to the prognostic value of studying the dynamics of telomere shortening and fusion, and discuss mechanisms and consequences of telomere-induced genome rearrangements.

  4. Molecular recognition of naphthalene diimide ligands by telomeric quadruplex-DNA: the importance of the protonation state and mediated hydrogen bonds.

    Science.gov (United States)

    Spinello, A; Barone, G; Grunenberg, J

    2016-01-28

    In depth Monte Carlo conformational scans in combination with molecular dynamics (MD) simulations and electronic structure calculations were applied in order to study the molecular recognition process between tetrasubstituted naphthalene diimide (ND) guests and G-quadruplex (G4) DNA receptors. ND guests are a promising class of telomere stabilizers due to which they are used in novel anticancer therapeutics. Though several ND guests have been studied experimentally in the past, the protonation state under physiological conditions is still unclear. Based on chemical intuition, in the case of N-methyl-piperazine substitution, different protonation states are possible and might play a crucial role in the molecular recognition process by G4-DNA. Depending on the proton concentration, different nitrogen atoms of the N-methyl-piperazine might (or might not) be protonated. This fact was considered in our simulation in terms of a case by case analysis, since the process of molecular recognition is determined by possible donor or acceptor positions. The results of our simulations show that the electrostatic interactions between the ND ligands and the G4 receptor are maximized in the case of the protonation of the terminal nitrogen atoms, forming compact ND G4 complexes inside the grooves. The influence of different protonation states in terms of the ability to form hydrogen bonds with the sugar-phosphate backbone, as well as the importance of mediated vs. direct hydrogen bonding, was analyzed in detail by MD and relaxed force constant (compliance constant) simulations.

  5. Telomerers rolle i cancer

    DEFF Research Database (Denmark)

    Bendix, Laila; Kølvraa, Steen

    2010-01-01

    Telomeres are a double-edged sword when it comes to cancer. On one hand, telomeres limit the cells' ability to divide and thereby restrict the uninhibited growth seen in cancer. On the other hand, short telomeres can initiate the chromosome instability that characterizes cancer. Diseases...... with the combination of short telomeres and high cancer risk are seen, but until now the use of telomeres as predictors of cancer has, in general, been unsuccessful. Telomeres and telomerase play an important role in further cancer development. Researchers are trying to exploit this in the development of new cancer...

  6. RTEL1: an essential helicase for telomere maintenance and the regulation of homologous recombination.

    Science.gov (United States)

    Uringa, Evert-Jan; Youds, Jillian L; Lisaingo, Kathleen; Lansdorp, Peter M; Boulton, Simon J

    2011-03-01

    Telomere maintenance and DNA repair are crucial processes that protect the genome against instability. RTEL1, an essential iron-sulfur cluster-containing helicase, is a dominant factor that controls telomere length in mice and is required for telomere integrity. In addition, RTEL1 promotes synthesis-dependent strand annealing to direct DNA double-strand breaks into non-crossover outcomes during mitotic repair and in meiosis. Here, we review the role of RTEL1 in telomere maintenance and homologous recombination and discuss models linking RTEL1's enzymatic activity to its function in telomere maintenance and DNA repair.

  7. The human CTC1/STN1/TEN1 complex regulates telomere maintenance in ALT cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Chenhui; Jia, Pingping; Chastain, Megan; Shiva, Olga; Chai, Weihang, E-mail: wchai@wsu.edu

    2017-06-15

    Maintaining functional telomeres is important for long-term proliferation of cells. About 15% of cancer cells are telomerase-negative and activate the alternative-lengthening of telomeres (ALT) pathway to maintain their telomeres. Recent studies have shown that the human CTC1/STN1/TEN1 complex (CST) plays a multi-faceted role in telomere maintenance in telomerase-expressing cancer cells. However, the role of CST in telomere maintenance in ALT cells is unclear. Here, we report that human CST forms a functional complex localizing in the ALT-associated PML bodies (APBs) in ALT cells throughout the cell cycle. Suppression of CST induces telomere instabilities including telomere fragility and elevates telomeric DNA recombination, leading to telomere dysfunction. In addition, CST deficiency significantly diminishes the abundance of extrachromosomal circular telomere DNA known as C-circles and t-circles. Suppression of CST also results in multinucleation in ALT cells and impairs cell proliferation. Our findings imply that the CST complex plays an important role in regulating telomere maintenance in ALT cells. - Highlights: • CST localizes at telomeres and ALT-associated PML bodies in ALT cells throughout the cell cycle. • CST is important for promoting telomeric DNA replication in ALT cells. • CST deficiency decreases ECTR formation and increases T-SCE. • CST deficiency impairs ALT cell proliferation and results in multinucleation.

  8. Telomere length analysis.

    Science.gov (United States)

    Canela, Andrés; Klatt, Peter; Blasco, María A

    2007-01-01

    Most somatic cells of long-lived species undergo telomere shortening throughout life. Critically short telomeres trigger loss of cell viability in tissues, which has been related to alteration of tissue function and loss of regenerative capabilities in aging and aging-related diseases. Hence, telomere length is an important biomarker for aging and can be used in the prognosis of aging diseases. These facts highlight the importance of developing methods for telomere length determination that can be employed to evaluate telomere length during the human aging process. Telomere length quantification methods have improved greatly in accuracy and sensitivity since the development of the conventional telomeric Southern blot. Here, we describe the different methodologies recently developed for telomere length quantification, as well as their potential applications for human aging studies.

  9. Gender and telomere length

    DEFF Research Database (Denmark)

    Gardner, Michael; Bann, David; Wiley, Laura

    2014-01-01

    It is widely believed that females have longer telomeres than males, although results from studies have been contradictory.......It is widely believed that females have longer telomeres than males, although results from studies have been contradictory....

  10. HSV-1 Remodels Host Telomeres to Facilitate Viral Replication

    Directory of Open Access Journals (Sweden)

    Zhong Deng

    2014-12-01

    Full Text Available Telomeres protect the ends of cellular chromosomes. We show here that infection with herpes simplex virus 1 (HSV-1 results in chromosomal structural aberrations at telomeres and the accumulation of telomere dysfunction-induced DNA damage foci (TIFs. At the molecular level, HSV-1 induces transcription of telomere repeat-containing RNA (TERRA, followed by the proteolytic degradation of the telomere protein TPP1 and loss of the telomere repeat DNA signal. The HSV-1-encoded E3 ubiquitin ligase ICP0 is required for TERRA transcription and facilitates TPP1 degradation. Small hairpin RNA (shRNA depletion of TPP1 increases viral replication, indicating that TPP1 inhibits viral replication. Viral replication protein ICP8 forms foci that coincide with telomeric proteins, and ICP8-null virus failed to degrade telomere DNA signal. These findings suggest that HSV-1 reorganizes telomeres to form ICP8-associated prereplication foci and to promote viral genomic replication.

  11. Investigation of hyperfine interactions in DNA nitrogenous bases using perturbed angular correlation spectroscopy

    International Nuclear Information System (INIS)

    Silva, Andreia dos Santos; Carbonari, Artur Wilson; Lapolli, Andre Luis; Saxena, Rajendra Narain; Saitovitch, Henrique

    2013-01-01

    Perturbed γγ angular correlations (PAC) spectroscopy has been used to study the DNA nitrogenous bases (adenine, cytosine, guanine, thymine), using 111 In→ 111 Cd and 111m Cd→ 111 Cd probe nuclei. One of the advantages of applying PAC technique to biological molecules is that the experiments can be carried out on molecules in aqueous solution [1], approaching the function of molecules under conditions that are close to in vivo conditions. The measurements were carried out for DNA nitrogenous bases molecules at 295 K and 77 K in order to investigate dynamic and static hyperfine interactions, respectively. The interpretation of the results was based on the measurements of dynamic interaction characterized by the decay constant from which valuable information on the macroscopic behavior of the molecules was obtained [2; 3]. On the other hand, PAC measurements at low temperature showed interaction frequency (ν Q ), asymmetry parameter (η) and the distribution of the quadrupole frequency (δ). These parameters provide a local microscopic description of the chemical environment in the neighborhood of the probe nuclei. Results showed differences in the hyperfine interactions of probe nuclei bound to the studied biomolecules. Such differences were observed by variations in the hyperfine parameters, which depended on the type of biomolecule and the results also showed that the probe nuclei bounded at the molecules in some cases and at others did not. (author)

  12. Telomerase activity, telomere length and hTERT DNA methylation in peripheral blood mononuclear cells from monozygotic twins with discordant smoking habits.

    Science.gov (United States)

    Marcon, Francesca; Siniscalchi, Ester; Andreoli, Cristina; Allione, Alessandra; Fiorito, Giovanni; Medda, Emanuela; Guarrera, Simonetta; Matullo, Giuseppe; Crebelli, Riccardo

    2017-10-01

    Increased telomerase expression has been implicated in the pathogenesis of lung cancer and, since the primary cause of lung cancer is smoking, an association between telomerase reactivation and tobacco smoke has been proposed. In this work an investigation has been performed to assess the relationship between tobacco smoke exposure and telomerase activity (TA) in peripheral blood mononuclear cells of healthy smokers. The methylation status of the catalytic subunit of telomerase hTERT was concurrently investigated to assess the possible association between epigenetic modifications of hTERT and TA. Besides, the association between smoke and telomere length (TL) has been evaluated. Healthy monozygotic twins with discordant smoking habits were selected as study population to minimize inter-individual differences because of demographic characteristics and genetic heterogeneity. Statistically significant higher values of TA and TL were observed in smokers compared to nonsmoker co-twins. The multivariate analysis of data showed, besides smoking habits (P = 0.02), an influence of gender (P = 0.006) and BMI (P = 0.001) on TA and a borderline effect of gender (P = 0.05) on TL. DNA methylation analysis, focused on 100 CpG sites mapping in hTERT, highlighted nine CpG sites differentially methylated in smokers. When co-twins were contrasted, selecting as variables the intra-twin difference in TA and hTERT DNA methylation, a statistically significant inverse correlation (P = 0.003) was observed between TA and DNA methylation at the cg05521538 site. In conclusion, these results indicate an association of tobacco smoke with TA and TL and suggest a possible association between smoke-induced epigenetic effects and TA in healthy smokers. Environ. Mol. Mutagen. 58:551-559, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  13. Perturbation of DNA replication and cell cycle progression by commonly used [3H]thymidine labeling protocols

    International Nuclear Information System (INIS)

    Hoy, C.A.; Lewis, E.D.; Schimke, R.T.

    1990-01-01

    The effect of tritiated thymidine incorporation on DNA replication was studied in Chinese hamster ovary cells. Rapidly eluting (small) DNA from cells labeled with 2 microCi of [ 3 H]thymidine per ml (200 microCi/mmol) for 60 min matured to a large nonelutable size within approximately 2 to 4 h, as measured by the alkaline elution technique. However, DNA from cells exposed to 10 microCi of [ 3 H]thymidine per ml (66 microCi/mmol) was more rapidly eluting initially and did not mature to a nonelutable size during subsequent incubation. Semiconservative DNA replication measured by cesium chloride gradient analysis of bromodeoxyuridine-substituted DNA was also found to be affected by the final specific activity of the [ 3 H]thymidine used in the labeling protocol. Dramatic cell cycle perturbations accompanied these effects on DNA replication, suggesting that labeling protocols commonly used to study DNA metabolism produce aberrant DNA replication and subsequent cell cycle perturbations

  14. Telomere length and age in humpback whales (Megaptera novaeangliae)

    NARCIS (Netherlands)

    Olsen, Morten Tange; Bérubé, Martine; Robbins, Jooke; Rew, Mary Beth; Palsboll, Per

    2009-01-01

    Telomeres are DNA sequences situated at the end of chromosomes that play a key role in maintaining chromosome integrity and are crucial for normal cell function. In vertebrates, telomeres tend to shorten with age, ultimately reaching a threshold believed to trigger cellular and organismal

  15. Dysfunctional telomeres in human BRCA2 mutated breast tumors and cell lines

    Energy Technology Data Exchange (ETDEWEB)

    Bodvarsdottir, Sigridur K., E-mail: skb@hi.is [Cancer Research Laboratory, BioMedical Centre, Faculty of Medicine, University of Iceland, Vatnsmyrarvegi 16, 101 Reykjavik (Iceland); Steinarsdottir, Margret [Chromosome Laboratory, Department of Genetics and Molecular Medicine, Landspitali University Hospital, Reykjavik (Iceland); Bjarnason, Hordur; Eyfjord, Jorunn E. [Cancer Research Laboratory, BioMedical Centre, Faculty of Medicine, University of Iceland, Vatnsmyrarvegi 16, 101 Reykjavik (Iceland)

    2012-01-03

    In the present study the possible involvement of telomeres in chromosomal instability of breast tumors and cell lines from BRCA2 mutation carriers was examined. Breast tumors from BRCA2 mutation carriers showed significantly higher frequency of chromosome end-to-end fusions (CEFs) than tumors from non-carriers despite normal telomere DNA content. Frequent CEFs were also found in four different BRCA2 heterozygous breast epithelial cell lines, occasionally with telomere signal at the fusion point, indicating telomere capping defects. Extrachromosomal telomeric repeat (ECTR) DNA was frequently found scattered around metaphase chromosomes and interstitial telomere sequences (ITSs) were also common. Telomere sister chromatid exchanges (T-SCEs), characteristic of cells using alternative lengthening of telomeres (ALT), were frequently detected in all heterozygous BRCA2 cell lines as well as the two ALT positive cell lines tested. Even though T-SCE frequency was similar in BRCA2 heterozygous and ALT positive cell lines they differed in single telomere signal loss and ITSs. Chromatid type alterations were more prominent in the BRCA2 heterozygous cell lines that may have propensity for telomere based chromosome healing. Telomere dysfunction-induced foci (TIFs) formation, identified by co-localization of telomeres and {gamma}-H2AX, supported telomere associated DNA damage response in BRCA2 heterozygous cell lines. TIFs were found in interphase nuclei, at chromosome ends, ITSs and ECTR DNA. In conclusion, our results suggest that BRCA2 has an important role in telomere stabilization by repressing CEFs through telomere capping and the prevention of telomere loss by replication stabilization.

  16. Dysfunctional telomeres in human BRCA2 mutated breast tumors and cell lines

    International Nuclear Information System (INIS)

    Bodvarsdottir, Sigridur K.; Steinarsdottir, Margret; Bjarnason, Hordur; Eyfjord, Jorunn E.

    2012-01-01

    In the present study the possible involvement of telomeres in chromosomal instability of breast tumors and cell lines from BRCA2 mutation carriers was examined. Breast tumors from BRCA2 mutation carriers showed significantly higher frequency of chromosome end-to-end fusions (CEFs) than tumors from non-carriers despite normal telomere DNA content. Frequent CEFs were also found in four different BRCA2 heterozygous breast epithelial cell lines, occasionally with telomere signal at the fusion point, indicating telomere capping defects. Extrachromosomal telomeric repeat (ECTR) DNA was frequently found scattered around metaphase chromosomes and interstitial telomere sequences (ITSs) were also common. Telomere sister chromatid exchanges (T-SCEs), characteristic of cells using alternative lengthening of telomeres (ALT), were frequently detected in all heterozygous BRCA2 cell lines as well as the two ALT positive cell lines tested. Even though T-SCE frequency was similar in BRCA2 heterozygous and ALT positive cell lines they differed in single telomere signal loss and ITSs. Chromatid type alterations were more prominent in the BRCA2 heterozygous cell lines that may have propensity for telomere based chromosome healing. Telomere dysfunction-induced foci (TIFs) formation, identified by co-localization of telomeres and γ-H2AX, supported telomere associated DNA damage response in BRCA2 heterozygous cell lines. TIFs were found in interphase nuclei, at chromosome ends, ITSs and ECTR DNA. In conclusion, our results suggest that BRCA2 has an important role in telomere stabilization by repressing CEFs through telomere capping and the prevention of telomere loss by replication stabilization.

  17. Telomere maintenance through recruitment of internal genomic regions.

    Science.gov (United States)

    Seo, Beomseok; Kim, Chuna; Hills, Mark; Sung, Sanghyun; Kim, Hyesook; Kim, Eunkyeong; Lim, Daisy S; Oh, Hyun-Seok; Choi, Rachael Mi Jung; Chun, Jongsik; Shim, Jaegal; Lee, Junho

    2015-09-18

    Cells surviving crisis are often tumorigenic and their telomeres are commonly maintained through the reactivation of telomerase. However, surviving cells occasionally activate a recombination-based mechanism called alternative lengthening of telomeres (ALT). Here we establish stably maintained survivors in telomerase-deleted Caenorhabditis elegans that escape from sterility by activating ALT. ALT survivors trans-duplicate an internal genomic region, which is already cis-duplicated to chromosome ends, across the telomeres of all chromosomes. These 'Template for ALT' (TALT) regions consist of a block of genomic DNA flanked by telomere-like sequences, and are different between two genetic background. We establish a model that an ancestral duplication of a donor TALT region to a proximal telomere region forms a genomic reservoir ready to be incorporated into telomeres on ALT activation.

  18. [Telomere lengthening by trichostatin A treatment in cloned pigs].

    Science.gov (United States)

    Xie, Bing-Teng; Ji, Guang-Zhen; Kong, Qing-Ran; Mao, Jian; Shi, Yong-Qian; Liu, Shi-Chao; Wu, Mei-Ling; Wang, Juan; Liu, Lin; Liu, Zhong-Hua

    2012-12-01

    Telomeres are repeated GC rich sequences at the end of chromosomes, and shorten with each cell division due to DNA end replication problem. Previously, reprogrammed somatic cells of cloned animals display variable telomere elongation. However, it was reported that the cloned animals including Dolly do not reset telomeres and show premature aging. In this study, we investigated telomere function in cloned or transgenic cloned pigs, including the cloned Northeast Min pigs, eGFP, Mx, and PGC1α transgenic cloned pigs, and found that the telomere lengths of cloned pigs were significantly shorter than the nuclear donor adult fibroblasts and age-matched noncloned pigs (Pstage for 24 h. Consistent with previous reports, the developmental rate of SCNT embryos to the blastocyst stage was significantly increased compared with those of the control group (16.35% vs. 27.09%, 21.60% vs. 34.90%, Plengthen the telomere lengths of cloned pigs.

  19. The Effect of Physical Activity agains the Telomere Length in the Leukocytes Cells of KONI Athletes

    Directory of Open Access Journals (Sweden)

    Endang Purwaningsih

    2017-07-01

    Full Text Available Telomeres are strands of non coding DNA at the ends of chromosomes that have the primary function to protect DNA from damage and maintain chromosomal stability. Physical exercise will increase the antioxidant activity can increase telomere proteins, lengthen telomeres and or protein networks associated with telomere so that the telomere remains long, or stopping telomere shortening. Telomere length was also associated with age. The purpose of the research was to determine telomere length of leukocyte cells in the KONI (Indonesian National Sports Committee athletes in Jakarta. The research method is descriptive, by measuring telomere length using quantitative PCR on leukocyte cells. Samples are KONI athletes from several sports, including men and women athletes, with ages between 15-20 years. Used a control group (not athletes is students of the Faculty of Medicine, University of YARSI. The results showed that there was no significant difference (p> 0.05 between telomere length group of athletes with the control group in both sexes. Similarly, telomere length between athlete male with female athletes also showed no significant difference (p> 0.05. It was concluded that physical exercise in athletes KONI at the age of 15- 20 years had no effect on telomere length in leukocytes. The results of this study provide information about the telomere length in Indonesian athletes at an early age.

  20. Placental telomere shortening in stillbirth: a sign of premature senescence?

    Science.gov (United States)

    Ferrari, Francesca; Facchinetti, Fabio; Saade, George; Menon, Ramkumar

    2016-01-01

    The objective of this study is to investigate placental telomere shortening in unexplained stillbirths (SBs) as an indication of premature senescence. Placentas were collected from 42 unexplained SB (>22 weeks), 43 term and 15 preterm live births, at the Policlinico Hospital of Modena (Italy). DNA extracted from placentae was studied for telomere length by real time PCR. Standard curves were generated for telomere lengths from single copy gene amplifications using a reference DNA. The telomere length for each sample was derived based on the ratio of telomere length between the sample and single copy gene standard (T/S ratio). The mean ratio of placental telomere in term live births was 5.181 ± 3.841. A twofold decrease in telomere length was seen in SBs (over all 2.455 ± 1.239; p PTBs) (6.382 ± 5.525; p < 0.01), whereas SBs telomere length were similar to those of preterm premature rupture of membranes (pPROM) (3.296 ± 3.599; p = ns). Substantial reduction in telomere length in SBs is indicative of placental senescence. These data provide mechanistic insights that premature aging may lead to placental dysfunction as an initiator of fetal demise in unexplained SBs.

  1. Telomere length modulation in human astroglial brain tumors.

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    Domenico La Torre

    Full Text Available BACKGROUND: Telomeres alteration during carcinogenesis and tumor progression has been described in several cancer types. Telomeres length is stabilized by telomerase (h-TERT and controlled by several proteins that protect telomere integrity, such as the Telomere Repeat-binding Factor (TRF 1 and 2 and the tankyrase-poli-ADP-ribose polymerase (TANKs-PARP complex. OBJECTIVE: To investigate telomere dysfunction in astroglial brain tumors we analyzed telomeres length, telomerase activity and the expression of a panel of genes controlling the length and structure of telomeres in tissue samples obtained in vivo from astroglial brain tumors with different grade of malignancy. MATERIALS AND METHODS: Eight Low Grade Astrocytomas (LGA, 11 Anaplastic Astrocytomas (AA and 11 Glioblastoma Multiforme (GBM samples were analyzed. Three samples of normal brain tissue (NBT were used as controls. Telomeres length was assessed through Southern Blotting. Telomerase activity was evaluated by a telomere repeat amplification protocol (TRAP assay. The expression levels of TRF1, TRF2, h-TERT and TANKs-PARP complex were determined through Immunoblotting and RT-PCR. RESULTS: LGA were featured by an up-regulation of TRF1 and 2 and by shorter telomeres. Conversely, AA and GBM were featured by a down-regulation of TRF1 and 2 and an up-regulation of both telomerase and TANKs-PARP complex. CONCLUSIONS: In human astroglial brain tumours, up-regulation of TRF1 and TRF2 occurs in the early stages of carcinogenesis determining telomeres shortening and genomic instability. In a later stage, up-regulation of PARP-TANKs and telomerase activation may occur together with an ADP-ribosylation of TRF1, causing a reduced ability to bind telomeric DNA, telomeres elongation and tumor malignant progression.

  2. Correlation of chromosomal instability, telomere length and telomere maintenance in microsatellite stable rectal cancer: a molecular subclass of rectal cancer.

    Directory of Open Access Journals (Sweden)

    Lisa A Boardman

    Full Text Available Colorectal cancer (CRC tumor DNA is characterized by chromosomal damage termed chromosomal instability (CIN and excessively shortened telomeres. Up to 80% of CRC is microsatellite stable (MSS and is historically considered to be chromosomally unstable (CIN+. However, tumor phenotyping depicts some MSS CRC with little or no genetic changes, thus being chromosomally stable (CIN-. MSS CIN- tumors have not been assessed for telomere attrition.MSS rectal cancers from patients ≤50 years old with Stage II (B2 or higher or Stage III disease were assessed for CIN, telomere length and telomere maintenance mechanism (telomerase activation [TA]; alternative lengthening of telomeres [ALT]. Relative telomere length was measured by qPCR in somatic epithelial and cancer DNA. TA was measured with the TRAPeze assay, and tumors were evaluated for the presence of C-circles indicative of ALT. p53 mutation status was assessed in all available samples. DNA copy number changes were evaluated with Spectral Genomics aCGH.Tumors were classified as chromosomally stable (CIN- and chromosomally instable (CIN+ by degree of DNA copy number changes. CIN- tumors (35%; n=6 had fewer copy number changes (<17% of their clones with DNA copy number changes than CIN+ tumors (65%; n=13 which had high levels of copy number changes in 20% to 49% of clones. Telomere lengths were longer in CIN- compared to CIN+ tumors (p=0.0066 and in those in which telomerase was not activated (p=0.004. Tumors exhibiting activation of telomerase had shorter tumor telomeres (p=0.0040; and tended to be CIN+ (p=0.0949.MSS rectal cancer appears to represent a heterogeneous group of tumors that may be categorized both on the basis of CIN status and telomere maintenance mechanism. MSS CIN- rectal cancers appear to have longer telomeres than those of MSS CIN+ rectal cancers and to utilize ALT rather than activation of telomerase.

  3. AKTIP/Ft1, a New Shelterin-Interacting Factor Required for Telomere Maintenance.

    KAUST Repository

    Burla, Romina; Carcuro, Mariateresa; Raffa, Grazia D; Galati, Alessandra; Raimondo, Domenico; Rizzo, Angela; La Torre, Mattia; Micheli, Emanuela; Ciapponi, Laura; Cenci, Giovanni; Cundari, Enrico; Musio, Antonio; Biroccio, Annamaria; Cacchione, Stefano; Gatti, Maurizio; Saggio, Isabella

    2015-01-01

    Telomeres are nucleoprotein complexes that protect the ends of linear chromosomes from incomplete replication, degradation and detection as DNA breaks. Mammalian telomeres are protected by shelterin, a multiprotein complex that binds the TTAGGG telomeric repeats and recruits a series of additional factors that are essential for telomere function. Although many shelterin-associated proteins have been so far identified, the inventory of shelterin-interacting factors required for telomere maintenance is still largely incomplete. Here, we characterize AKTIP/Ft1 (human AKTIP and mouse Ft1 are orthologous), a novel mammalian shelterin-bound factor identified on the basis of its homology with the Drosophila telomere protein Pendolino. AKTIP/Ft1 shares homology with the E2 variant ubiquitin-conjugating (UEV) enzymes and has been previously implicated in the control of apoptosis and in vesicle trafficking. RNAi-mediated depletion of AKTIP results in formation of telomere dysfunction foci (TIFs). Consistent with these results, AKTIP interacts with telomeric DNA and binds the shelterin components TRF1 and TRF2 both in vivo and in vitro. Analysis of AKTIP- depleted human primary fibroblasts showed that they are defective in PCNA recruiting and arrest in the S phase due to the activation of the intra S checkpoint. Accordingly, AKTIP physically interacts with PCNA and the RPA70 DNA replication factor. Ft1-depleted p53-/- MEFs did not arrest in the S phase but displayed significant increases in multiple telomeric signals (MTS) and sister telomere associations (STAs), two hallmarks of defective telomere replication. In addition, we found an epistatic relation for MST formation between Ft1 and TRF1, which has been previously shown to be required for replication fork progression through telomeric DNA. Ch-IP experiments further suggested that in AKTIP-depleted cells undergoing the S phase, TRF1 is less tightly bound to telomeric DNA than in controls. Thus, our results collectively

  4. AKTIP/Ft1, a New Shelterin-Interacting Factor Required for Telomere Maintenance.

    KAUST Repository

    Burla, Romina

    2015-06-25

    Telomeres are nucleoprotein complexes that protect the ends of linear chromosomes from incomplete replication, degradation and detection as DNA breaks. Mammalian telomeres are protected by shelterin, a multiprotein complex that binds the TTAGGG telomeric repeats and recruits a series of additional factors that are essential for telomere function. Although many shelterin-associated proteins have been so far identified, the inventory of shelterin-interacting factors required for telomere maintenance is still largely incomplete. Here, we characterize AKTIP/Ft1 (human AKTIP and mouse Ft1 are orthologous), a novel mammalian shelterin-bound factor identified on the basis of its homology with the Drosophila telomere protein Pendolino. AKTIP/Ft1 shares homology with the E2 variant ubiquitin-conjugating (UEV) enzymes and has been previously implicated in the control of apoptosis and in vesicle trafficking. RNAi-mediated depletion of AKTIP results in formation of telomere dysfunction foci (TIFs). Consistent with these results, AKTIP interacts with telomeric DNA and binds the shelterin components TRF1 and TRF2 both in vivo and in vitro. Analysis of AKTIP- depleted human primary fibroblasts showed that they are defective in PCNA recruiting and arrest in the S phase due to the activation of the intra S checkpoint. Accordingly, AKTIP physically interacts with PCNA and the RPA70 DNA replication factor. Ft1-depleted p53-/- MEFs did not arrest in the S phase but displayed significant increases in multiple telomeric signals (MTS) and sister telomere associations (STAs), two hallmarks of defective telomere replication. In addition, we found an epistatic relation for MST formation between Ft1 and TRF1, which has been previously shown to be required for replication fork progression through telomeric DNA. Ch-IP experiments further suggested that in AKTIP-depleted cells undergoing the S phase, TRF1 is less tightly bound to telomeric DNA than in controls. Thus, our results collectively

  5. Tiptoeing to chromosome tips: facts, promises and perils of today's human telomere biology.

    Science.gov (United States)

    Fajkus, J; Simícková, M; Maláska, J

    2002-04-29

    The past decade has witnessed an explosion of knowledge concerning the structure and function of chromosome terminal structures-telomeres. Today's telomere research has advanced from a pure descriptive approach of DNA and protein components to an elementary understanding of telomere metabolism, and now to promising applications in medicine. These applications include 'passive' ones, among which the use of analysis of telomeres and telomerase (a cellular reverse transcriptase that synthesizes telomeres) for cancer diagnostics is the best known. The 'active' applications involve targeted downregulation or upregulation of telomere synthesis, either to mortalize immortal cancer cells, or to rejuvenate mortal somatic cells and tissues for cellular transplantations, respectively. This article reviews the basic data on structure and function of human telomeres and telomerase, as well as both passive and active applications of human telomere biology.

  6. Social isolation shortens telomeres in African Grey parrots (Psittacus erithacus erithacus.

    Directory of Open Access Journals (Sweden)

    Denise Aydinonat

    Full Text Available Telomeres, the caps of eukaryotic chromosomes, control chromosome stability and cellular senescence, but aging and exposure to chronic stress are suspected to cause attrition of telomere length. We investigated the effect of social isolation on telomere length in the highly social and intelligent African Grey parrot (Psittacus erithacus erithacus. Our study population consisted of single-housed (n = 26 and pair-housed (n = 19 captive individuals between 0.75 to 45 years of age. Relative telomere length of erythrocyte DNA was measured by quantitative real-time PCR. We found that telomere length declined with age (p<0.001, and socially isolated parrots had significantly shorter telomeres compared to pair-housed birds (p<0.001 - even among birds of similar ages. Our findings provide the first evidence that social isolation affects telomere length, which supports the hypothesis that telomeres provide a biomarker indicating exposure to chronic stress.

  7. Acacetin and Chrysin, Two Polyphenolic Compounds, Alleviate Telomeric Position Effect in Human Cells

    Directory of Open Access Journals (Sweden)

    Amina Boussouar

    2013-01-01

    Full Text Available We took advantage of the ability of human telomeres to silence neighboring genes (telomere position effect or TPE to design a high-throughput screening assay for drugs altering telomeres. We identified, for the first time, that two dietary flavones, acacetin and chrysin, are able to specifically alleviate TPE in human cells. We further investigated their influence on telomere integrity and showed that both drugs drastically deprotect telomeres against DNA damage response. However, telomere deprotection triggered by shelterin dysfunction does not affect TPE, indicating that acacetin and chrysin target several functions of telomeres. These results show that TPE-based screening assays represent valuable methods to discover new compounds targeting telomeres.

  8. Stabilization of Reversed Replication Forks by Telomerase Drives Telomere Catastrophe.

    Science.gov (United States)

    Margalef, Pol; Kotsantis, Panagiotis; Borel, Valerie; Bellelli, Roberto; Panier, Stephanie; Boulton, Simon J

    2018-01-25

    Telomere maintenance critically depends on the distinct activities of telomerase, which adds telomeric repeats to solve the end replication problem, and RTEL1, which dismantles DNA secondary structures at telomeres to facilitate replisome progression. Here, we establish that reversed replication forks are a pathological substrate for telomerase and the source of telomere catastrophe in Rtel1 -/- cells. Inhibiting telomerase recruitment to telomeres, but not its activity, or blocking replication fork reversal through PARP1 inhibition or depleting UBC13 or ZRANB3 prevents the rapid accumulation of dysfunctional telomeres in RTEL1-deficient cells. In this context, we establish that telomerase binding to reversed replication forks inhibits telomere replication, which can be mimicked by preventing replication fork restart through depletion of RECQ1 or PARG. Our results lead us to propose that telomerase inappropriately binds to and inhibits restart of reversed replication forks within telomeres, which compromises replication and leads to critically short telomeres. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  9. Genomic instability and telomere fusion of canine osteosarcoma cells.

    Directory of Open Access Journals (Sweden)

    Junko Maeda

    Full Text Available Canine osteosarcoma (OSA is known to present with highly variable and chaotic karyotypes, including hypodiploidy, hyperdiploidy, and increased numbers of metacentric chromosomes. The spectrum of genomic instabilities in canine OSA has significantly augmented the difficulty in clearly defining the biological and clinical significance of the observed cytogenetic abnormalities. In this study, eight canine OSA cell lines were used to investigate telomere fusions by fluorescence in situ hybridization (FISH using a peptide nucleotide acid probe. We characterized each cell line by classical cytogenetic studies and cellular phenotypes including telomere associated factors and then evaluated correlations from this data. All eight canine OSA cell lines displayed increased abnormal metacentric chromosomes and exhibited numerous telomere fusions and interstitial telomeric signals. Also, as evidence of unstable telomeres, colocalization of γ-H2AX and telomere signals in interphase cells was observed. Each cell line was characterized by a combination of data representing cellular doubling time, DNA content, chromosome number, metacentric chromosome frequency, telomere signal level, cellular radiosensitivity, and DNA-PKcs protein expression level. We have also studied primary cultures from 10 spontaneous canine OSAs. Based on the observation of telomere aberrations in those primary cell cultures, we are reasonably certain that our observations in cell lines are not an artifact of prolonged culture. A correlation between telomere fusions and the other characteristics analyzed in our study could not be identified. However, it is important to note that all of the canine OSA samples exhibiting telomere fusion utilized in our study were telomerase positive. Pending further research regarding telomerase negative canine OSA cell lines, our findings may suggest telomere fusions can potentially serve as a novel marker for canine OSA.

  10. Telomeres and genomic damage repair. Their implication in human pathology

    International Nuclear Information System (INIS)

    Perez, Maria del R.; Dubner, Diana; Michelin, Severino; Gisone, Pablo; Carosella, Edgardo D.

    2002-01-01

    Telomeres, functional complexed that protect eukaryotic chromosome ends, participate in the regulation of cell proliferation and could play a role in the stabilization of genomic regions in response to genotoxic stress. Their significance in human pathology becomes evident in several diseases sharing genomic instability as a common trait, in which alterations of the telomere metabolism have been demonstrated. Many of them are also associated with hypersensitivity to ionizing radiation and cancer susceptibility. Besides the specific proteins belonging to the telomeric complex, other proteins involved in the DNA repair machinery, such as ATM, BRCA1, BRCA2, PARP/tankyrase system, DNA-PK and RAD50-MRE11-NBS1 complexes, are closely related with the telomere. This suggests that the telomere sequesters DNA repair proteins for its own structure maintenance, with could also be released toward damaged sites in the genomic DNA. This communication describes essential aspects of telomere structure and function and their links with homologous recombination, non-homologous end-joining (NHEJ), V(D)J system and mismatch-repair (MMR). Several pathological conditions exhibiting alterations in some of these mechanisms are also considered. The cell response to ionizing radiation and its relationship with the telomeric metabolism is particularly taken into account as a model for studying genotoxicity. (author)

  11. The role of telomeres in Etoposide induced tumor cell death.

    Science.gov (United States)

    Jeyapalan, Jessie; Leake, Alan; Ahmed, Shaheda; Saretzki, Gabriele; Tilby, Michael; von Zglinicki, Thomas

    2004-09-01

    Etoposide, a topoisomerase II poison is used in the treatment of a number of solid tumors. Contradictory data exist on the role of the telomere/telomerase complex in etoposide induced apoptosis. Therefore we examined the effects of etoposide treatment in the neuroblastoma cell line SHSY5Y, with very short telomeres and the acute lymphoblastic T cell line 1301, which displays extremely long telomeres. Both short-term and continuous exposure to the drug were examined. Etoposide induced widespread DNA damage followed by DNA damage foci formation and ultimately growth arrest and apoptosis in a concentration-dependent manner. However, length of telomeres and of single stranded telomeric G rich overhangs did not change significantly under the treatments in any cell line. There was no significant induction of single-strand breaks in the G-rich strand of telomeres. Telomerase activity was transiently upregulated under low concentrations of etoposide, while high concentrations resulted in decreased telomerase activity only after onset of apoptosis. Telomerase overexpression protected against etoposide induced apoptosis in fibroblasts. The data suggest that telomeres are not major signal transducers towards growth arrest or apoptosis after etoposide treatment. However, upregulation of telomerase might be part of an attempted adaptative response, which protects cells by a mechanism that might be independent of telomere length maintenance.

  12. L-Carnosine reduces telomere damage and shortening rate in cultured normal fibroblasts

    International Nuclear Information System (INIS)

    Shao Lan; Li Qinghuan; Tan Zheng

    2004-01-01

    Telomere is the repetitive DNA sequence at the end of chromosomes, which shortens progressively with cell division and limits the replicative potential of normal human somatic cells. L-Carnosine, a naturally occurring dipeptide, has been reported to delay the replicative senescence, and extend the lifespan of cultured human diploid fibroblasts. In this work, we studied the effect of carnosine on the telomeric DNA of cultured human fetal lung fibroblast cells. Cells continuously grown in 20 mM carnosine exhibited a slower telomere shortening rate and extended lifespan in population doublings. When kept in a long-term nonproliferating state, they accumulated much less damages in the telomeric DNA when cultured in the presence of carnosine. We suggest that the reduction in telomere shortening rate and damages in telomeric DNA made an important contribution to the life-extension effect of carnosine

  13. Human RTEL1 deficiency causes Hoyeraal-Hreidarsson syndrome with short telomeres and genome instability.

    Science.gov (United States)

    Le Guen, Tangui; Jullien, Laurent; Touzot, Fabien; Schertzer, Michael; Gaillard, Laetitia; Perderiset, Mylène; Carpentier, Wassila; Nitschke, Patrick; Picard, Capucine; Couillault, Gérard; Soulier, Jean; Fischer, Alain; Callebaut, Isabelle; Jabado, Nada; Londono-Vallejo, Arturo; de Villartay, Jean-Pierre; Revy, Patrick

    2013-08-15

    Hoyeraal-Hreidarsson syndrome (HHS), a severe variant of dyskeratosis congenita (DC), is characterized by early onset bone marrow failure, immunodeficiency and developmental defects. Several factors involved in telomere length maintenance and/or protection are defective in HHS/DC, underlining the relationship between telomere dysfunction and these diseases. By combining whole-genome linkage analysis and exome sequencing, we identified compound heterozygous RTEL1 (regulator of telomere elongation helicase 1) mutations in three patients with HHS from two unrelated families. RTEL1 is a DNA helicase that participates in DNA replication, DNA repair and telomere integrity. We show that, in addition to short telomeres, RTEL1-deficient cells from patients exhibit hallmarks of genome instability, including spontaneous DNA damage, anaphase bridges and telomeric aberrations. Collectively, these results identify RTEL1 as a novel HHS-causing gene and highlight its role as a genomic caretaker in humans.

  14. Ku must load directly onto the chromosome end in order to mediate its telomeric functions.

    Directory of Open Access Journals (Sweden)

    Christopher R Lopez

    2011-08-01

    Full Text Available The Ku heterodimer associates with the Saccharomyces cerevisiae telomere, where it impacts several aspects of telomere structure and function. Although Ku avidly binds DNA ends via a preformed channel, its ability to associate with telomeres via this mechanism could be challenged by factors known to bind directly to the chromosome terminus. This has led to uncertainty as to whether Ku itself binds directly to telomeric ends and whether end association is crucial for Ku's telomeric functions. To address these questions, we constructed DNA end binding-defective Ku heterodimers by altering amino acid residues in Ku70 and Ku80 that were predicted to contact DNA. These mutants continued to associate with their known telomere-related partners, such as Sir4, a factor required for telomeric silencing, and TLC1, the RNA component of telomerase. Despite these interactions, we found that the Ku mutants had markedly reduced association with telomeric chromatin and null-like deficiencies for telomere end protection, length regulation, and silencing functions. In contrast to Ku null strains, the DNA end binding defective Ku mutants resulted in increased, rather than markedly decreased, imprecise end-joining proficiency at an induced double-strand break. This result further supports that it was the specific loss of Ku's telomere end binding that resulted in telomeric defects rather than global loss of Ku's functions. The extensive telomere defects observed in these mutants lead us to propose that Ku is an integral component of the terminal telomeric cap, where it promotes a specific architecture that is central to telomere function and maintenance.

  15. Ku must load directly onto the chromosome end in order to mediate its telomeric functions.

    Science.gov (United States)

    Lopez, Christopher R; Ribes-Zamora, Albert; Indiviglio, Sandra M; Williams, Christopher L; Haricharan, Svasti; Bertuch, Alison A

    2011-08-01

    The Ku heterodimer associates with the Saccharomyces cerevisiae telomere, where it impacts several aspects of telomere structure and function. Although Ku avidly binds DNA ends via a preformed channel, its ability to associate with telomeres via this mechanism could be challenged by factors known to bind directly to the chromosome terminus. This has led to uncertainty as to whether Ku itself binds directly to telomeric ends and whether end association is crucial for Ku's telomeric functions. To address these questions, we constructed DNA end binding-defective Ku heterodimers by altering amino acid residues in Ku70 and Ku80 that were predicted to contact DNA. These mutants continued to associate with their known telomere-related partners, such as Sir4, a factor required for telomeric silencing, and TLC1, the RNA component of telomerase. Despite these interactions, we found that the Ku mutants had markedly reduced association with telomeric chromatin and null-like deficiencies for telomere end protection, length regulation, and silencing functions. In contrast to Ku null strains, the DNA end binding defective Ku mutants resulted in increased, rather than markedly decreased, imprecise end-joining proficiency at an induced double-strand break. This result further supports that it was the specific loss of Ku's telomere end binding that resulted in telomeric defects rather than global loss of Ku's functions. The extensive telomere defects observed in these mutants lead us to propose that Ku is an integral component of the terminal telomeric cap, where it promotes a specific architecture that is central to telomere function and maintenance.

  16. Telomeres and human health

    DEFF Research Database (Denmark)

    Bojesen, S E

    2013-01-01

    will be reviewed. In addition, technical difficulties and the reasons why measurement of telomeres has still not been introduced into routine clinical practice will be discussed. Findings from recent studies conducted in many thousands of individuals indicate that telomere length is not-or at best only marginally...

  17. When Telomerase Causes Telomere Loss.

    Science.gov (United States)

    Glousker, Galina; Lingner, Joachim

    2018-02-05

    Telomerase counteracts telomere shortening, preventing cellular senescence. Telomerase deficiency causes telomere syndromes because of premature telomere exhaustion in highly proliferative cells. Paradoxically, in a recent issue of Cell, Margalef et al. (2018) demonstrate that telomerase causes telomere loss in cells lacking the RTEL1 helicase, which is defective in Hoyeraal-Hreidarsson syndrome (HHS). Copyright © 2018 Elsevier Inc. All rights reserved.

  18. Telomere length and depression

    DEFF Research Database (Denmark)

    Wium-Andersen, Marie Kim; Ørsted, David Dynnes; Rode, Line

    2017-01-01

    BACKGROUND: Depression has been cross-sectionally associated with short telomeres as a measure of biological age. However, the direction and nature of the association is currently unclear. AIMS: We examined whether short telomere length is associated with depression cross-sectionally as well...... as prospectively and genetically. METHOD: Telomere length and three polymorphisms, TERT, TERC and OBFC1, were measured in 67 306 individuals aged 20-100 years from the Danish general population and associated with register-based attendance at hospital for depression and purchase of antidepressant medication....... RESULTS: Attendance at hospital for depression was associated with short telomere length cross-sectionally, but not prospectively. Further, purchase of antidepressant medication was not associated with short telomere length cross-sectionally or prospectively. Mean follow-up was 7.6 years (range 0...

  19. Rif1 acts through Protein Phosphatase 1 but independent of replication timing to suppress telomere extension in budding yeast.

    Science.gov (United States)

    Kedziora, Sylwia; Gali, Vamsi K; Wilson, Rosemary H C; Clark, Kate R M; Nieduszynski, Conrad A; Hiraga, Shin-Ichiro; Donaldson, Anne D

    2018-05-04

    The Rif1 protein negatively regulates telomeric TG repeat length in the budding yeast Saccharomyces cerevisiae, but how it prevents telomere over-extension is unknown. Rif1 was recently shown to control DNA replication by acting as a Protein Phosphatase 1 (PP1)-targeting subunit. Therefore, we investigated whether Rif1 controls telomere length by targeting PP1 activity. We find that a Rif1 mutant defective for PP1 interaction causes a long-telomere phenotype, similar to that of rif1Δ cells. Tethering PP1 at a specific telomere partially substitutes for Rif1 in limiting TG repeat length, confirming the importance of PP1 in telomere length control. Ablating Rif1-PP1 interaction is known to cause precocious activation of telomere-proximal replication origins and aberrantly early telomere replication. However, we find that Rif1 still limits telomere length even if late replication is forced through deletion of nearby replication origins, indicating that Rif1 can control telomere length independent of replication timing. Moreover we find that, even at a de novo telomere created after DNA synthesis during a mitotic block, Rif1-PP1 interaction is required to suppress telomere lengthening and prevent inappropriate recruitment of Tel1 kinase. Overall, our results show that Rif1 controls telomere length by recruiting PP1 to directly suppress telomerase-mediated TG repeat lengthening.

  20. Tumour-cell apoptosis after cisplatin treatment is not telomere dependent.

    Science.gov (United States)

    Jeyapalan, Jessie C; Saretzki, Gabriele; Leake, Alan; Tilby, Michael J; von Zglinicki, Thomas

    2006-06-01

    Cisplatin is a major chemotherapeutic agent, especially for the treatment of neuroblastoma. Telomeres with their sequence (TTAGGG)n are probable targets for cisplatin intrastrand cross-linking, but the role of telomeres in mediating cisplatin cytotoxicity is not clear. After exposure to cisplatin as single dose or continuous treatment, we found no loss of telomeres in either SHSY5Y neuroblastoma cells (telomere length, approximately 4 kbp), HeLa 229 cells (telomere length, 20 kbp) or in the acute lymphoblastic T cell line 1301 (telomere length, approximately 80 kbp). There was no induction of telomeric single strand breaks, telomeric overhangs were not degraded and telomerase activity was down-regulated only after massive onset of apoptosis. In contrast, cisplatin induced a delayed formation of DNA strand breaks and induced DNA damage foci containing gamma-H2A.X at nontelomeric sites. Interstitial DNA damage appears to be more important than telomere loss or telomeric damage as inducer of the signal pathway towards apoptosis and/or growth arrest in cisplatin-treated tumour cells.

  1. Sulforaphane enhances irradiation effects in terms of perturbed cell cycle progression and increased DNA damage in pancreatic cancer cells.

    Directory of Open Access Journals (Sweden)

    Patrick Naumann

    Full Text Available Sulforaphane (SFN, an herbal isothiocyanate enriched in cruciferous vegetables like broccoli and cauliflower, has gained popularity for its antitumor effects in cell lines such as pancreatic cancer. Antiproliferative as well as radiosensitizing properties were reported for head and neck cancer but little is known about its effects in pancreatic cancer cells in combination with irradiation (RT.In four established pancreatic cancer cell lines we investigated clonogenic survival, analyzed cell cycle distribution and compared DNA damage via flow cytometry and western blot after treatment with SFN and RT.Both SFN and RT show a strong and dose dependent survival reduction in clonogenic assays, an induction of a G2/M cell cycle arrest and an increase in γH2AX protein level indicating DNA damage. Effects were more pronounced in combined treatment and both cell cycle perturbation and DNA damage persisted for a longer period than after SFN or RT alone. Moreover, SFN induced a loss of DNA repair proteins Ku 70, Ku 80 and XRCC4.Our results suggest that combination of SFN and RT exerts a more distinct DNA damage and growth inhibition than each treatment alone. SFN seems to be a viable option to improve treatment efficacy of chemoradiation with hopefully higher rates of secondary resectability after neoadjuvant treatment for pancreatic cancer.

  2. Nature vs nurture: interplay between the genetic control of telomere length and environmental factors.

    Science.gov (United States)

    Harari, Yaniv; Romano, Gal-Hagit; Ungar, Lior; Kupiec, Martin

    2013-11-15

    Telomeres are nucleoprotein structures that cap the ends of the linear eukaryotic chromosomes, thus protecting their stability and integrity. They play important roles in DNA replication and repair and are central to our understanding of aging and cancer development. In rapidly dividing cells, telomere length is maintained by the activity of telomerase. About 400 TLM (telomere length maintenance) genes have been identified in yeast, as participants of an intricate homeostasis network that keeps telomere length constant. Two papers have recently shown that despite this extremely complex control, telomere length can be manipulated by external stimuli. These results have profound implications for our understanding of cellular homeostatic systems in general and of telomere length maintenance in particular. In addition, they point to the possibility of developing aging and cancer therapies based on telomere length manipulation.

  3. RTEL1 is a replisome-associated helicase that promotes telomere and genome-wide replication.

    Science.gov (United States)

    Vannier, Jean-Baptiste; Sandhu, Sumit; Petalcorin, Mark I R; Wu, Xiaoli; Nabi, Zinnatun; Ding, Hao; Boulton, Simon J

    2013-10-11

    Regulator of telomere length 1 (RTEL1) is an essential DNA helicase that disassembles telomere loops (T loops) and suppresses telomere fragility to maintain the integrity of chromosome ends. We established that RTEL1 also associates with the replisome through binding to proliferating cell nuclear antigen (PCNA). Mouse cells disrupted for the RTEL1-PCNA interaction (PIP mutant) exhibited accelerated senescence, replication fork instability, reduced replication fork extension rates, and increased origin usage. Although T-loop disassembly at telomeres was unaffected in the mutant cells, telomere replication was compromised, leading to fragile sites at telomeres. RTEL1-PIP mutant mice were viable, but loss of the RTEL1-PCNA interaction accelerated the onset of tumorigenesis in p53-deficient mice. We propose that RTEL1 plays a critical role in both telomere and genome-wide replication, which is crucial for genetic stability and tumor avoidance.

  4. Solution structure of telomere binding domain of AtTRB2 derived from Arabidopsis thaliana

    International Nuclear Information System (INIS)

    Yun, Ji-Hye; Lee, Won Kyung; Kim, Heeyoun; Kim, Eunhee; Cheong, Chaejoon; Cho, Myeon Haeng; Lee, Weontae

    2014-01-01

    Highlights: • We have determined solution structure of Myb domain of AtTRB2. • The Myb domain of AtTRB2 is located in the N-terminal region. • The Myb domain of AtTRB2 binds to plant telomeric DNA without fourth helix. • Helix 2 and 3 of the Myb domain of AtTRB2 are involved in DNA recognition. • AtTRB2 is a novel protein distinguished from other known plant TBP. - Abstract: Telomere homeostasis is regulated by telomere-associated proteins, and the Myb domain is well conserved for telomere binding. AtTRB2 is a member of the SMH (Single-Myb-Histone)-like family in Arabidopsis thaliana, having an N-terminal Myb domain, which is responsible for DNA binding. The Myb domain of AtTRB2 contains three α-helices and loops for DNA binding, which is unusual given that other plant telomere-binding proteins have an additional fourth helix that is essential for DNA binding. To understand the structural role for telomeric DNA binding of AtTRB2, we determined the solution structure of the Myb domain of AtTRB2 (AtTRB2 1–64 ) using nuclear magnetic resonance (NMR) spectroscopy. In addition, the inter-molecular interaction between AtTRB2 1–64 and telomeric DNA has been characterized by the electrophoretic mobility shift assay (EMSA) and NMR titration analyses for both plant (TTTAGGG)n and human (TTAGGG)n telomere sequences. Data revealed that Trp28, Arg29, and Val47 residues located in Helix 2 and Helix 3 are crucial for DNA binding, which are well conserved among other plant telomere binding proteins. We concluded that although AtTRB2 is devoid of the additional fourth helix in the Myb-extension domain, it is able to bind to plant telomeric repeat sequences as well as human telomeric repeat sequences

  5. Solution structure of telomere binding domain of AtTRB2 derived from Arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Ji-Hye [Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Won Kyung [Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Heeyoun [Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Eunhee; Cheong, Chaejoon [Magnetic Resonance Team, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 363-883 (Korea, Republic of); Cho, Myeon Haeng [Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Weontae, E-mail: wlee@spin.yonsei.ac.kr [Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2014-09-26

    Highlights: • We have determined solution structure of Myb domain of AtTRB2. • The Myb domain of AtTRB2 is located in the N-terminal region. • The Myb domain of AtTRB2 binds to plant telomeric DNA without fourth helix. • Helix 2 and 3 of the Myb domain of AtTRB2 are involved in DNA recognition. • AtTRB2 is a novel protein distinguished from other known plant TBP. - Abstract: Telomere homeostasis is regulated by telomere-associated proteins, and the Myb domain is well conserved for telomere binding. AtTRB2 is a member of the SMH (Single-Myb-Histone)-like family in Arabidopsis thaliana, having an N-terminal Myb domain, which is responsible for DNA binding. The Myb domain of AtTRB2 contains three α-helices and loops for DNA binding, which is unusual given that other plant telomere-binding proteins have an additional fourth helix that is essential for DNA binding. To understand the structural role for telomeric DNA binding of AtTRB2, we determined the solution structure of the Myb domain of AtTRB2 (AtTRB2{sub 1–64}) using nuclear magnetic resonance (NMR) spectroscopy. In addition, the inter-molecular interaction between AtTRB2{sub 1–64} and telomeric DNA has been characterized by the electrophoretic mobility shift assay (EMSA) and NMR titration analyses for both plant (TTTAGGG)n and human (TTAGGG)n telomere sequences. Data revealed that Trp28, Arg29, and Val47 residues located in Helix 2 and Helix 3 are crucial for DNA binding, which are well conserved among other plant telomere binding proteins. We concluded that although AtTRB2 is devoid of the additional fourth helix in the Myb-extension domain, it is able to bind to plant telomeric repeat sequences as well as human telomeric repeat sequences.

  6. Flap Endonuclease 1 Limits Telomere Fragility on the Leading Strand*

    Science.gov (United States)

    Teasley, Daniel C.; Parajuli, Shankar; Nguyen, Mai; Moore, Hayley R.; Alspach, Elise; Lock, Ying Jie; Honaker, Yuchi; Saharia, Abhishek; Piwnica-Worms, Helen; Stewart, Sheila A.

    2015-01-01

    The existence of redundant replication and repair systems that ensure genome stability underscores the importance of faithful DNA replication. Nowhere is this complexity more evident than in challenging DNA templates, including highly repetitive or transcribed sequences. Here, we demonstrate that flap endonuclease 1 (FEN1), a canonical lagging strand DNA replication protein, is required for normal, complete leading strand replication at telomeres. We find that the loss of FEN1 nuclease activity, but not DNA repair activities, results in leading strand-specific telomere fragility. Furthermore, we show that FEN1 depletion-induced telomere fragility is increased by RNA polymerase II inhibition and is rescued by ectopic RNase H1 expression. These data suggest that FEN1 limits leading strand-specific telomere fragility by processing RNA:DNA hybrid/flap intermediates that arise from co-directional collisions occurring between the replisome and RNA polymerase. Our data reveal the first molecular mechanism for leading strand-specific telomere fragility and the first known role for FEN1 in leading strand DNA replication. Because FEN1 mutations have been identified in human cancers, our findings raise the possibility that unresolved RNA:DNA hybrid structures contribute to the genomic instability associated with cancer. PMID:25922071

  7. Flap Endonuclease 1 Limits Telomere Fragility on the Leading Strand.

    Science.gov (United States)

    Teasley, Daniel C; Parajuli, Shankar; Nguyen, Mai; Moore, Hayley R; Alspach, Elise; Lock, Ying Jie; Honaker, Yuchi; Saharia, Abhishek; Piwnica-Worms, Helen; Stewart, Sheila A

    2015-06-12

    The existence of redundant replication and repair systems that ensure genome stability underscores the importance of faithful DNA replication. Nowhere is this complexity more evident than in challenging DNA templates, including highly repetitive or transcribed sequences. Here, we demonstrate that flap endonuclease 1 (FEN1), a canonical lagging strand DNA replication protein, is required for normal, complete leading strand replication at telomeres. We find that the loss of FEN1 nuclease activity, but not DNA repair activities, results in leading strand-specific telomere fragility. Furthermore, we show that FEN1 depletion-induced telomere fragility is increased by RNA polymerase II inhibition and is rescued by ectopic RNase H1 expression. These data suggest that FEN1 limits leading strand-specific telomere fragility by processing RNA:DNA hybrid/flap intermediates that arise from co-directional collisions occurring between the replisome and RNA polymerase. Our data reveal the first molecular mechanism for leading strand-specific telomere fragility and the first known role for FEN1 in leading strand DNA replication. Because FEN1 mutations have been identified in human cancers, our findings raise the possibility that unresolved RNA:DNA hybrid structures contribute to the genomic instability associated with cancer. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Identification of the functional domains of the telomere protein Rap1 in Schizosaccharomyces pombe.

    Directory of Open Access Journals (Sweden)

    Ikumi Fujita

    Full Text Available The telomere at the end of a linear chromosome plays crucial roles in genome stability. In the fission yeast Schizosaccharomyces pombe, the Rap1 protein, one of the central players at the telomeres, associates with multiple proteins to regulate various telomere functions, such as the maintenance of telomere DNA length, telomere end protection, maintenance of telomere heterochromatin, and telomere clustering in meiosis. The molecular bases of the interactions between Rap1 and its partners, however, remain largely unknown. Here, we describe the identification of the interaction domains of Rap1 with its partners. The Bqt1/Bqt2 complex, which is required for normal meiotic progression, Poz1, which is required for telomere length control, and Taz1, which is required for the recruitment of Rap1 to telomeres, bind to distinct domains in the C-terminal half of Rap1. Intriguingly, analyses of a series of deletion mutants for rap1(+ have revealed that the long N-terminal region (1-456 a.a. [amino acids] of Rap1 (full length: 693 a.a. is not required for telomere DNA length control, telomere end protection, and telomere gene silencing, whereas the C-terminal region (457-693 a.a. containing Poz1- and Taz1-binding domains plays important roles in those functions. Furthermore, the Bqt1/Bqt2- and Taz1-binding domains are essential for normal spore formation after meiosis. Our results suggest that the C-terminal half of Rap1 is critical for the primary telomere functions, whereas the N-terminal region containing the BRCT (BRCA1 C-terminus and Myb domains, which are evolutionally conserved among the Rap1 family proteins, does not play a major role at the telomeres.

  9. The Escherichia coli Tus-Ter replication fork barrier causes site-specific DNA replication perturbation in yeast.

    Science.gov (United States)

    Larsen, Nicolai B; Sass, Ehud; Suski, Catherine; Mankouri, Hocine W; Hickson, Ian D

    2014-04-07

    Replication fork (RF) pausing occurs at both 'programmed' sites and non-physiological barriers (for example, DNA adducts). Programmed RF pausing is required for site-specific DNA replication termination in Escherichia coli, and this process requires the binding of the polar terminator protein, Tus, to specific DNA sequences called Ter. Here, we demonstrate that Tus-Ter modules also induce polar RF pausing when engineered into the Saccharomyces cerevisiae genome. This heterologous RF barrier is distinct from a number of previously characterized, protein-mediated, RF pause sites in yeast, as it is neither Tof1-dependent nor counteracted by the Rrm3 helicase. Although the yeast replisome can overcome RF pausing at Tus-Ter modules, this event triggers site-specific homologous recombination that requires the RecQ helicase, Sgs1, for its timely resolution. We propose that Tus-Ter can be utilized as a versatile, site-specific, heterologous DNA replication-perturbing system, with a variety of potential applications.

  10. Selaginella moellendoffii telomeres: conserved and unique features in an ancient land plant lineage

    Directory of Open Access Journals (Sweden)

    Eugene V Shakirov

    2012-07-01

    Full Text Available Telomeres, the essential terminal regions of linear eukaryotic chromosomes, consist of G-rich DNA repeats bound by a plethora of associated proteins. While the general pathways of telomere maintenance are evolutionarily conserved, individual telomere complex components show remarkable variation between eukaryotic lineages and even within closely related species. The recent genome sequencing of the lycophyte Selaginella moellendoffii and the availability of an ever-increasing number of flowering plant genomes provides a unique opportunity to evaluate the molecular and functional evolution of telomere components from the early evolving non-seed plants to the more developmentally advanced angiosperms. Here we analyzed telomere sequence in S. moellendorffii and found it to consist of TTTAGGG repeats, typical of most plants. Telomere tracts in S. moellendorffii range from 1-5.5 kb, closely resembling Arabidopsis thaliana. We identified several S. moellendorffii genes encoding sequence homologues of proteins involved in telomere maintenance in other organisms, including CST complex components and the telomere-binding proteins POT1 and TRFL. Notable sequence similarities and differences were uncovered among the telomere-related genes in some of the plant lineages. Taken together, the data indicate that comparative analysis of the telomere complex in early diverging land plants such as S. moellendorffii and green algae will yield important insights into the evolution of telomeres and their protein constituents.

  11. Inherited mutations in the helicase RTEL1 cause telomere dysfunction and Hoyeraal-Hreidarsson syndrome.

    Science.gov (United States)

    Deng, Zhong; Glousker, Galina; Molczan, Aliah; Fox, Alan J; Lamm, Noa; Dheekollu, Jayaraju; Weizman, Orr-El; Schertzer, Michael; Wang, Zhuo; Vladimirova, Olga; Schug, Jonathan; Aker, Memet; Londoño-Vallejo, Arturo; Kaestner, Klaus H; Lieberman, Paul M; Tzfati, Yehuda

    2013-09-03

    Telomeres repress the DNA damage response at the natural chromosome ends to prevent cell-cycle arrest and maintain genome stability. Telomeres are elongated by telomerase in a tightly regulated manner to ensure a sufficient number of cell divisions throughout life, yet prevent unlimited cell division and cancer development. Hoyeraal-Hreidarsson syndrome (HHS) is characterized by accelerated telomere shortening and a broad range of pathologies, including bone marrow failure, immunodeficiency, and developmental defects. HHS-causing mutations have previously been found in telomerase and the shelterin component telomeric repeat binding factor 1 (TRF1)-interacting nuclear factor 2 (TIN2). We identified by whole-genome exome sequencing compound heterozygous mutations in four siblings affected with HHS, in the gene encoding the regulator of telomere elongation helicase 1 (RTEL1). Rtel1 was identified in mouse by its genetic association with telomere length. However, its mechanism of action and whether it regulates telomere length in human remained unknown. Lymphoblastoid cell lines obtained from a patient and from the healthy parents carrying heterozygous RTEL1 mutations displayed telomere shortening, fragility and fusion, and growth defects in culture. Ectopic expression of WT RTEL1 suppressed the telomere shortening and growth defect, confirming the causal role of the RTEL1 mutations in HHS and demonstrating the essential function of human RTEL1 in telomere protection and elongation. Finally, we show that human RTEL1 interacts with the shelterin protein TRF1, providing a potential recruitment mechanism of RTEL1 to telomeres.

  12. Inherited mutations in the helicase RTEL1 cause telomere dysfunction and Hoyeraal–Hreidarsson syndrome

    Science.gov (United States)

    Deng, Zhong; Glousker, Galina; Molczan, Aliah; Fox, Alan J.; Lamm, Noa; Dheekollu, Jayaraju; Weizman, Orr-El; Schertzer, Michael; Wang, Zhuo; Vladimirova, Olga; Schug, Jonathan; Aker, Memet; Londoño-Vallejo, Arturo; Kaestner, Klaus H.; Lieberman, Paul M.; Tzfati, Yehuda

    2013-01-01

    Telomeres repress the DNA damage response at the natural chromosome ends to prevent cell-cycle arrest and maintain genome stability. Telomeres are elongated by telomerase in a tightly regulated manner to ensure a sufficient number of cell divisions throughout life, yet prevent unlimited cell division and cancer development. Hoyeraal–Hreidarsson syndrome (HHS) is characterized by accelerated telomere shortening and a broad range of pathologies, including bone marrow failure, immunodeficiency, and developmental defects. HHS-causing mutations have previously been found in telomerase and the shelterin component telomeric repeat binding factor 1 (TRF1)-interacting nuclear factor 2 (TIN2). We identified by whole-genome exome sequencing compound heterozygous mutations in four siblings affected with HHS, in the gene encoding the regulator of telomere elongation helicase 1 (RTEL1). Rtel1 was identified in mouse by its genetic association with telomere length. However, its mechanism of action and whether it regulates telomere length in human remained unknown. Lymphoblastoid cell lines obtained from a patient and from the healthy parents carrying heterozygous RTEL1 mutations displayed telomere shortening, fragility and fusion, and growth defects in culture. Ectopic expression of WT RTEL1 suppressed the telomere shortening and growth defect, confirming the causal role of the RTEL1 mutations in HHS and demonstrating the essential function of human RTEL1 in telomere protection and elongation. Finally, we show that human RTEL1 interacts with the shelterin protein TRF1, providing a potential recruitment mechanism of RTEL1 to telomeres. PMID:23959892

  13. Modulation of telomere binding proteins: a future area of research for skin protection and anti-aging target.

    Science.gov (United States)

    Imbert, Isabelle; Botto, Jean-Marie; Farra, Claude D; Domloge, Nouha

    2012-06-01

    Telomere shortening is considered as one of the main characteristics of cellular aging by limiting cellular division. Besides the fundamental advances through the discoveries of telomere and telomerase, which were recognized by a Nobel Prize, telomere protection remains an essential area of research. Recently, it was evidenced that studying the cross-talks between the proteins associated with telomere should provide a better understanding of the mechanistic basis for telomere-associated aging phenotypes. In this review, we discuss the current knowledge on telomere shortening, telomerase activity, and the essential role of telomere binding proteins in telomere stabilization and telomere-end protection. This review highlights the capacity of telomere binding proteins to limit cellular senescence and to maintain skin tissue homeostasis, which is of key importance to reduce accelerated tissue aging. Future studies addressing telomere protection and limitation of DNA damage response in human skin should include investigations on telomere binding proteins. As little is known about the expression of telomere binding proteins in human skin and modulation of their expression with aging, it remains an interesting field of skin research and a key area for future skin protection and anti-aging developments. © 2012 Wiley Periodicals, Inc.

  14. The influence of the telomere-telomerase system on diabetes mellitus and its vascular complications.

    Science.gov (United States)

    Qi Nan, Wu; Ling, Zhang; Bing, Chen

    2015-06-01

    The telomere-telomerase system plays an important role in the pathogenesis and disease progression of diabetes mellitus as well as in its vascular complications. Recent studies suggest that telomere shortening and abnormal telomerase activity occur in patients with diabetes mellitus, and targeting the telomere-telomerase system has become a prospective treatment for diabetes mellitus and its vascular complications. This review highlights the significance of the telomere-telomerase system and supports its role as a possible therapeutic target for patients with diabetes mellitus and its vascular complications Areas covered: This review covers the advances in understanding the telomere-telomerase system over the last 30 years and its significance in diabetes mellitus. In addition, it provides knowledge regarding the significance of the telomere-telomerase system in diabetes mellitus and its vascular complications as well as its role and mechanisms in oxidative stress, cell therapy and antioxidant activity Expert opinion: The telomere-telomerase system may be a potential therapeutic target that can protect against DNA damage and apoptosis in patients with diabetes mellitus and its vascular complications. DNA damage and apoptosis are associated with oxidative stress and are involved in the dysfunction of pancreatic β cells, insulin resistance, and its vascular complications. Abnormalities in the telomere-telomerase system may be associated with diabetes mellitus and its vascular complications. Therapies targeting telomere-telomerase system, telomerase reverse transcriptase transfection and alterative telomere lengthening must be identified before gene therapy can commence.

  15. High plasma folate is negatively associated with leukocyte telomere length in Framingham Offspring cohort.

    Science.gov (United States)

    Paul, Ligi; Jacques, Paul F; Aviv, Abraham; Vasan, Ramachandran S; D'Agostino, Ralph B; Levy, Daniel; Selhub, Jacob

    2015-03-01

    Shortening of telomeres, the protective structures at the ends of eukaryotic chromosomes, is associated with age-related pathologies. Telomere length is influenced by DNA integrity and DNA and histone methylation. Folate plays a role in providing precursors for nucleotides and methyl groups for methylation reactions and has the potential to influence telomere length. We determined the association between leukocyte telomere length and long-term plasma folate status (mean of 4 years) in Framingham Offspring Study (n = 1,044, females = 52.1 %, mean age 59 years) using data from samples collected before and after folic acid fortification. Leukocyte telomere length was determined by Southern analysis and fasting plasma folate concentration using microbiological assay. There was no significant positive association between long-term plasma folate and leukocyte telomere length among the Framingham Offspring Study participants perhaps due to their adequate folate status. While the leukocyte telomere length in the second quintile of plasma folate was longer than that in the first quintile, the difference was not statistically significant. The leukocyte telomere length of the individuals in the fifth quintile of plasma folate was shorter than that of those in the second quintile by 180 bp (P folate concentrations in the upper four quintiles of plasma folate (P for trend = 0.001). Multivitamin use was associated with shorter telomeres in this cohort (P = 0.015). High plasma folate status possibly resulting from high folic acid intake may interfere with the role of folate in maintaining telomere integrity.

  16. DNA breaks and repair in interstitial telomere sequences: Influence of chromatin structure; Etude des cassures de l'ADN et des mecanismes de reparation dans les sequences telomeriques interstitielles: Influence de la structure chromatinienne

    Energy Technology Data Exchange (ETDEWEB)

    Revaud, D.

    2009-06-15

    Interstitial Telomeric Sequences (ITS) are over-involved in spontaneous and radiationinduced chromosome aberrations in chinese hamster cells. We have performed a study to investigate the origin of their instability, spontaneously or after low doses irradiation. Our results demonstrate that ITS have a particular chromatin structure: short nucleotide repeat length, less compaction of the 30 nm chromatin fiber, presence of G-quadruplex structures. These features would modulate breaks production and would favour the recruitment of alternative DNA repair mechanisms, which are prone to produce chromosome aberrations. These pathways could be at the origin of chromosome aberrations in ITS whereas NHEJ and HR Double Strand Break repair pathways are rather required for a correct repair in these regions. (author)

  17. Perturbations in DNA structure upon interaction with porphyrins revealed by chemical probes, DNA footprinting and molecular modelling.

    Science.gov (United States)

    Ford, K G; Neidle, S

    1995-06-01

    The interactions of several porphyrins with a 74 base-pair DNA sequence have been examined by footprinting and chemical protection methods. Tetra-(4-N-methyl-(pyridyl)) porphyrin (TMPy), two of its metal complexes and tetra-(4-trimethylanilinium) porphyrin (TMAP) bind to closely similar AT-rich sequences. The three TMPy ligands produce modest changes in DNA structure and base accessibility on binding, in contrast to the large-scale conformational changes observed with TMAP. Molecular modelling studies have been performed on TMPy and TMAP bound in the AT-rich minor groove of an oligonucleotide. These have shown that significant structural change is needed to accommodate the bulky trimethyl substituent groups of TMAP, in contrast to the facile minor groove fit of TMPy.

  18. Telomeres, Nutrition, and Longevity: Can We Really Navigate Our Aging?

    Science.gov (United States)

    Vidacek, Nikolina Škrobot; Nanic, Lucia; Ravlic, Sanda; Sopta, Mary; Geric, Marko; Gajski, Goran; Garaj-Vrhovac, Vera; Rubelj, Ivica

    2017-12-12

    Telomeres are dynamic chromosome-end structures that serve as guardians of genome stability. They are known to be one of the major determinants of aging and longevity in higher mammals. Studies have demonstrated a direct correlation between telomere length and life expectancy, stress, DNA damage, and onset of aging-related diseases. This review discusses the most important factors that influence our telomeres. Various genetic and environmental factors such as diet, physical activity, obesity, and stress are known to influence health and longevity as well as telomere dynamics. Individuals currently have the opportunity to modulate the dynamics of their aging and health span, monitor these processes, and even make future projections by following their telomere dynamics. As telomeres react to positive as well as negative health factors, we should be able to directly influence our telomere metabolism, slow their deterioration, and diminish our aging and perhaps extend our life and health span. © The Author(s) 2017. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  19. Telomere Maintenance Mechanisms in Cancer

    OpenAIRE

    Tiago Bordeira Gaspar; Ana Sá; José Manuel Lopes; Manuel Sobrinho-Simões; Paula Soares; João Vinagre

    2018-01-01

    Tumour cells can adopt telomere maintenance mechanisms (TMMs) to avoid telomere shortening, an inevitable process due to successive cell divisions. In most tumour cells, telomere length (TL) is maintained by reactivation of telomerase, while a small part acquires immortality through the telomerase-independent alternative lengthening of telomeres (ALT) mechanism. In the last years, a great amount of data was generated, and different TMMs were reported and explained in detail, benefiting from g...

  20. The Role of the Telomere End Protection Complex in Telomere Main

    Science.gov (United States)

    2003-06-01

    identification of putative substrates of ATM kinase family members. J Biol Chem, 1999. 274(53): p. 37538-43. 9. Lei, M., E.R. Podell , P. Baumann, and T.R. Cech...DNA self-recognition in the structure of Pot1 bound to telomeric single-stranded DNA. Nature, 2003. 426(6963): p. 198-203. 10. Lei, M., E.R. Podell

  1. Silica inhalation altered telomere length and gene expression of telomere regulatory proteins in lung tissue of rats.

    Science.gov (United States)

    Shoeb, Mohammad; Joseph, Pius; Kodali, Vamsi; Mustafa, Gul; Farris, Breanne Y; Umbright, Christina; Roberts, Jenny R; Erdely, Aaron; Antonini, James M

    2017-12-11

    Exposure to silica can cause lung fibrosis and cancer. Identification of molecular targets is important for the intervention and/or prevention of silica-induced lung diseases. Telomeres consist of tandem repeats of DNA sequences at the end of chromosomes, preventing chromosomal fusion and degradation. Regulator of telomere length-1 (RTEL1) and telomerase reverse transcriptase (TERT), genes involved in telomere regulation and function, play important roles in maintaining telomere integrity and length. The goal of this study was to assess the effect of silica inhalation on telomere length and the regulation of RTEL1 and TERT. Lung tissues and blood samples were collected from rats at 4, 32, and 44 wk after exposure to 15 mg/m 3 of silica × 6 h/d × 5 d. Controls were exposed to air. At all-time points, RTEL1 expression was significantly decreased in lung tissue of the silica-exposed animals compared to controls. Also, significant increases in telomere length and TERT were observed in the silica group at 4 and 32 wk. Telomere length, RTEL1 and TERT expression may serve as potential biomarkers related to silica exposure and may offer insight into the molecular mechanism of silica-induced lung disease and tumorigeneses.

  2. Does oxidative stress shorten telomeres?

    NARCIS (Netherlands)

    Boonekamp, Jelle J.; Bauch, Christina; Mulder, Ellis; Verhulst, Simon

    Oxidative stress shortens telomeres in cell culture, but whether oxidative stress explains variation in telomere shortening in vivo at physiological oxidative stress levels is not well known. We therefore tested for correlations between six oxidative stress markers and telomere attrition in nestling

  3. Role of arterial telomere dysfunction in hypertension: relative contributions of telomere shortening and telomere uncapping.

    Science.gov (United States)

    Morgan, R Garrett; Ives, Stephen J; Walker, Ashley E; Cawthon, Richard M; Andtbacka, Robert H I; Noyes, Dirk; Lesniewski, Lisa A; Richardson, Russell S; Donato, Anthony J

    2014-06-01

    Telomere shortening in arteries could lead to telomere uncapping and cellular senescence, which in turn could promote the development of hypertension. To assess the novel role of arterial telomere dysfunction in hypertension, we compared mean telomere length (qPCR), telomere uncapping (serine 139 phosphorylated histone γ-H2A.X (γ-H2) localized to telomeres: ChIP), and tumor suppressor protein p53 (P53)/cyclin-dependent kinase inhibitor 1A (P21)-induced senescence (P53 bound to P21 gene promoter: ChIP) in arteries from 55 age-matched hypertensive and nonhypertensive individuals. Arterial mean telomere length was not different in hypertensive patients compared with nonhypertensive individuals (P = 0.29). Arterial telomere uncapping and P53/P21-induced senescence were two-fold greater in hypertensive patients compared with nonhypertensive individuals (P = 0.04 and P = 0.02, respectively). Arterial mean telomere length was not associated with telomere uncapping or P53/P21-induced senescence (r = -0.02, P = 0.44 and r = 0.01, P = 0.50, respectively), but telomere uncapping was a highly influential covariate for the hypertension group difference in P53/P21-induced senescence (r = 0.62, P hypertension status (P = 0.03), whereas mean telomere length was not (P = 0.68). Collectively, these findings demonstrate that arterial telomere uncapping and P53/P21-induced senescence are linked to hypertension independently of mean telomere length, and telomere uncapping influences hypertension status more than mean telomere length.

  4. N-Methyl-N'-nitro-N-nitrosoguanidine-induced senescence-like growth arrest in colon cancer cells is associated with loss of adenomatous polyposis coli protein, microtubule organization, and telomeric DNA

    Directory of Open Access Journals (Sweden)

    Narayan Satya

    2004-01-01

    Full Text Available Abstract Background Cellular senescence is a state in which mammalian cells enter into an irreversible growth arrest and altered biological functions. The senescence response in mammalian cells can be elicited by DNA-damaging agents. In the present study we report that the DNA-damaging agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG is able to induce senescence in the HCT-116 colon cancer cell line. Results Cells treated with lower concentrations of MNNG (0–25 microM for 50 h showed a dose-dependent increase in G2/M phase arrest and apoptosis; however, cells treated with higher concentrations of MNNG (50–100 microM showed a senescence-like G0/G1 phase arrest which was confirmed by increased expression of β-galactosidase, a senescence induced marker. The G2/M phase arrest and apoptosis were found to be associated with increased levels of p53 protein, but the senescence-like G0/G1 phase arrest was dissociated with p53 protein levels, since the p53 protein levels decreased in senescence-like arrested cells. We further, determined whether the decreased level of p53 was a transcriptional or a translational phenomenon. The results revealed that the decreased level of p53 protein in senescence-like arrested cells was a transcriptional phenomenon since p53 mRNA levels simultaneously decreased after treatment with higher concentrations of MNNG. We also examined the effect of MNNG treatment on other cell cycle-related proteins such as p21, p27, cyclin B1, Cdc2, c-Myc and max. The expression levels of these proteins were increased in cells treated with lower concentrations of MNNG, which supported the G2/M phase arrest. However, cells treated with higher concentrations of MNNG showed decreased levels of these proteins, and hence, may not play a role in cell cycle arrest. We then examined a possible association of the expression of APC protein and telomeric DNA signals with cellular senescence in MNNG-treated cells. We found that protein and m

  5. The effect of regular strength training on telomere length in human skeletal muscle

    DEFF Research Database (Denmark)

    Kadi, F.; Ponsot, Elodie; Piehl-Aulin, Karin

    2008-01-01

    PURPOSE: The length of DNA telomeres is an important parameter of the proliferative potential of tissues. A recent study has reported abnormally short telomeres in skeletal muscle of athletes with exercise-associated fatigue. This important report raises the question of whether long-term practice...... of sports might have deleterious effects on muscle telomeres. Therefore, we aimed to compare telomere length of a group of power lifters (PL; N = 7) who trained for 8 +/- 3 yr against that of a group of healthy, active subjects (C; N = 7) with no history of strength training. METHODS: Muscle biopsies were...

  6. NEIL3 Repairs Telomere Damage during S Phase to Secure Chromosome Segregation at Mitosis

    Directory of Open Access Journals (Sweden)

    Jia Zhou

    2017-08-01

    Full Text Available Oxidative damage to telomere DNA compromises telomere integrity. We recently reported that the DNA glycosylase NEIL3 preferentially repairs oxidative lesions in telomere sequences in vitro. Here, we show that loss of NEIL3 causes anaphase DNA bridging because of telomere dysfunction. NEIL3 expression increases during S phase and reaches maximal levels in late S/G2. NEIL3 co-localizes with TRF2 and associates with telomeres during S phase, and this association increases upon oxidative stress. Mechanistic studies reveal that NEIL3 binds to single-stranded DNA via its intrinsically disordered C terminus in a telomere-sequence-independent manner. Moreover, NEIL3 is recruited to telomeres through its interaction with TRF1, and this interaction enhances the enzymatic activity of purified NEIL3. Finally, we show that NEIL3 interacts with AP Endonuclease 1 (APE1 and the long-patch base excision repair proteins PCNA and FEN1. Taken together, we propose that NEIL3 protects genome stability through targeted repair of oxidative damage in telomeres during S/G2 phase.

  7. E-type cyclins modulate telomere integrity in mammalian male meiosis.

    Science.gov (United States)

    Manterola, Marcia; Sicinski, Piotr; Wolgemuth, Debra J

    2016-06-01

    We have shown that E-type cyclins are key regulators of mammalian male meiosis. Depletion of cyclin E2 reduced fertility in male mice due to meiotic defects, involving abnormal pairing and synapsis, unrepaired DNA, and loss of telomere structure. These defects were exacerbated by additional loss of cyclin E1, and complete absence of both E-type cyclins produces a meiotic catastrophe. Here, we investigated the involvement of E-type cyclins in maintaining telomere integrity in male meiosis. Spermatocytes lacking cyclin E2 and one E1 allele (E1+/-E2-/-) displayed a high rate of telomere abnormalities but can progress to pachytene and diplotene stages. We show that their telomeres exhibited an aberrant DNA damage repair response during pachynema and that the shelterin complex proteins TRF2 and RAP2 were significantly decreased in the proximal telomeres. Moreover, the insufficient level of these proteins correlated with an increase of γ-H2AX foci in the affected telomeres and resulted in telomere associations involving TRF1 and telomere detachment in later prophase-I stages. These results suggest that E-type cyclins are key modulators of telomere integrity during meiosis by, at least in part, maintaining the balance of shelterin complex proteins, and uncover a novel role of E-type cyclins in regulating chromosome structure during male meiosis.

  8. Cells with dysfunctional telomeres are susceptible to reactive oxygen species hydrogen peroxide via generation of multichromosomal fusions and chromosomal fragments bearing telomeres

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Seon Rang [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Department of Biochemistry, College of Medicine, Korea University, Seoul 136-705 (Korea, Republic of); Park, Jeong-Eun; Juhn, Kyoung-Mi; Ju, Yeun-Jin; Jeong, Jaemin [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Kang, Chang-Mo; Yun, Hyun Jin [Division of Radiation Effect, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Yun, Mi Yong; Shin, Hyun-Jin; Joo, Hyun-Yoo; Park, Eun-Ran; Park, In-Chul; Hong, Sung Hee; Hwang, Sang-Gu [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Kim, Haekwon [Department of Biotechnology, Seoul Woman' s University, Seoul 139-774 (Korea, Republic of); Cho, Myung-Haing [Laboratory of Toxicology, College of Veterinary Medicine, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, Sang Hoon [Department of Biology, Kyung Hee University, Seoul 130-701 (Korea, Republic of); Park, Gil Hong [Department of Biochemistry, College of Medicine, Korea University, Seoul 136-705 (Korea, Republic of); Lee, Kee-Ho, E-mail: khlee@kirams.re.kr [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of)

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer Under conditions of telomere erosion, cells become extremely sensitive to H{sub 2}O{sub 2}. Black-Right-Pointing-Pointer Chromosomal regions adjacent to telomeres are cleaved by H{sub 2}O{sub 2} under such conditions. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} thus causes multichromosomal fusions and generation of small chromosomal fragments. Black-Right-Pointing-Pointer N-acetylcysteine prevents H{sub 2}O{sub 2}-induced chromosomal aberrations. -- Abstract: During genotoxic stress, reactive oxygen species hydrogen peroxide (H{sub 2}O{sub 2}) is a prime mediator of the DNA damage response. Telomeres function both to assist in DNA damage repair and to inhibit chromosomal end-to-end fusion. Here, we show that telomere dysfunction renders cells susceptible to H{sub 2}O{sub 2}, via generation of multichromosomal fusion and chromosomal fragments. H{sub 2}O{sub 2} caused formation of multichromosomal end-to-end fusions involving more than three chromosomes, preferentially when telomeres were erosive. Interestingly, extensive chromosomal fragmentation (yielding small-sized fragments) occurred only in cells exhibiting such multichromosomal fusions. Telomeres were absent from fusion points, being rather present in the small fragments, indicating that H{sub 2}O{sub 2} cleaves chromosomal regions adjacent to telomeres. Restoration of telomere function or addition of the antioxidant N-acetylcysteine prevented development of chromosomal aberrations and rescued the observed hypersensitivity to H{sub 2}O{sub 2}. Thus, chromosomal regions adjacent to telomeres become sensitive to reactive oxygen species hydrogen peroxide when telomeres are dysfunctional, and are cleaved to produce multichromosomal fusions and small chromosomal fragments bearing the telomeres.

  9. Organization and evolution of Drosophila terminin: similarities and differences between Drosophila and human telomeres

    Directory of Open Access Journals (Sweden)

    Grazia Daniela Raffa

    2013-05-01

    Full Text Available Drosophila lacks telomerase and fly telomeres are elongated by occasional transposition of three specialized retroelements. Drosophila telomeres do not terminate with GC-rich repeats and are assembled independently of the sequence of chromosome ends. Recent work has shown that Drosophila telomeres are capped by the terminin complex, which includes the fast-evolving proteins HOAP, HipHop, Moi and Ver. These proteins are not conserves outside Drosophilidae and localize and function exclusively at telomeres, protecting them from fusion events. Other proteins required to prevent end-to-end fusion in flies include HP1, Eff/UbcD1, ATM, the components of the Mre11-Rad50-Nbs (MRN complex, and the Woc transcription factor. These proteins do not share the terminin properties; they are evolutionarily conserved non-fast-evolving proteins that do not accumulate only telomeres and do not serve telomere-specific functions. We propose that following telomerase loss, Drosophila rapidly evolved terminin to bind chromosome ends in a sequence-independent manner. This hypothesis suggests that terminin is the functional analog of the shelterin complex that protects human telomeres. The non-terminin proteins are instead likely to correspond to ancestral telomere-associated proteins that did not evolve as rapidly as terminin because of the functional constraints imposed by their involvement in diverse cellular processes. Thus, it appears that the main difference between Drosophila and human telomeres is in the protective complexes that specifically associate with the DNA termini. We believe that Drosophila telomeres offer excellent opportunities for investigations on human telomere biology. The identification of additional Drosophila genes encoding non-terminin proteins involved in telomere protection might lead to the discovery of novel components of human telomeres.

  10. Donor Telomere Length SAA

    Science.gov (United States)

    A new NCI study has found that, among patients with severe aplastic anemia who received a hematopoietic cell transplant from an unrelated donor, those whose donor white blood cells had longer telomeres had higher survival rates five-years after transplant

  11. Growing old, yet staying young: The role of telomeres in bats' exceptional longevity.

    Science.gov (United States)

    Foley, Nicole M; Hughes, Graham M; Huang, Zixia; Clarke, Michael; Jebb, David; Whelan, Conor V; Petit, Eric J; Touzalin, Frédéric; Farcy, Olivier; Jones, Gareth; Ransome, Roger D; Kacprzyk, Joanna; O'Connell, Mary J; Kerth, Gerald; Rebelo, Hugo; Rodrigues, Luísa; Puechmaille, Sébastien J; Teeling, Emma C

    2018-02-01

    Understanding aging is a grand challenge in biology. Exceptionally long-lived animals have mechanisms that underpin extreme longevity. Telomeres are protective nucleotide repeats on chromosome tips that shorten with cell division, potentially limiting life span. Bats are the longest-lived mammals for their size, but it is unknown whether their telomeres shorten. Using >60 years of cumulative mark-recapture field data, we show that telomeres shorten with age in Rhinolophus ferrumequinum and Miniopterus schreibersii , but not in the bat genus with greatest longevity, Myotis . As in humans, telomerase is not expressed in Myotis myotis blood or fibroblasts. Selection tests on telomere maintenance genes show that ATM and SETX , which repair and prevent DNA damage, potentially mediate telomere dynamics in Myotis bats. Twenty-one telomere maintenance genes are differentially expressed in Myotis , of which 14 are enriched for DNA repair, and 5 for alternative telomere-lengthening mechanisms. We demonstrate how telomeres, telomerase, and DNA repair genes have contributed to the evolution of exceptional longevity in Myotis bats, advancing our understanding of healthy aging.

  12. Getting in (and out of) the loop: regulating higher order telomere structures.

    Science.gov (United States)

    Luke-Glaser, Sarah; Poschke, Heiko; Luke, Brian

    2012-01-01

    The DNA at the ends of linear chromosomes (the telomere) folds back onto itself and forms an intramolecular lariat-like structure. Although the telomere loop has been implicated in the protection of chromosome ends from nuclease-mediated resection and unscheduled DNA repair activities, it potentially poses an obstacle to the DNA replication machinery during S-phase. Therefore, the coordinated regulation of telomere loop formation, maintenance, and resolution is required in order to establish a balance between protecting the chromosome ends and promoting their duplication prior to cell division. Until recently, the only factor known to influence telomere looping in human cells was TRF2, a component of the shelterin complex. Recent work in yeast and mouse cells has uncovered additional regulatory factors that affect the loop structure at telomeres. In the following "perspective" we outline what is known about telomere looping and highlight the latest results regarding the regulation of this chromosome end structure. We speculate about how the manipulation of the telomere loop may have therapeutic implications in terms of diseases associated with telomere dysfunction and uncontrolled proliferation.

  13. Getting in (and out of the loop: regulating higher order telomere structures

    Directory of Open Access Journals (Sweden)

    Sarah eLuke-Glaser

    2012-11-01

    Full Text Available The DNA at the ends of linear chromosomes (the telomere folds back onto itself and forms an intramolecular lariat-like structure. Although the telomere loop has been implicated in the protection of chromosome ends from nuclease-mediated resection and unscheduled DNA repair activities, it potentially poses an obstacle to the DNA replication machinery during S phase. Therefore, the coordinated regulation of telomere loop formation, maintenance and resolution is required in order to establish a balance between protecting the chromosome ends and promoting their duplication prior to cell division. Until recently, the only factor know to influence telomere looping in human cells was TRF2, a component of the shelterin complex. Recent work in yeast and mouse cells has uncovered additional regulatory factors that affect the loop structure at telomeres. In the following perspective we will outline what is known about telomere looping and highlight the latest results regarding the regulation of this chromosome end structure. We will speculate about how the manipulation of the telomere loop may have therapeutic implications in terms of diseases associated with telomere dysfunction and uncontrolled proliferation.

  14. Telomeres, telomerase and oral cancer (Review).

    Science.gov (United States)

    Sebastian, Sinto; Grammatica, Luciano; Paradiso, Angelo

    2005-12-01

    Oral squamous cell carcinoma (oral cancer) and many squamous cell carcinomas of the head and neck arise as a consequence of multiple molecular events induced by the effects of various carcinogens related to tobacco use, environmental factors, and viruses in some instances (e.g., mucosal oncogenic human papillomaviruses), against a background of inheritable resistance or susceptibility. Consequent genetic damage affects many chromosomes and genes, and it is the accumulation of these changes that appears to lead to carcinoma. Telomere maintenance by telomerase or, in its absence, alternative lengthening of telomeres protect this acquired altered genetic information ensuring immortality without losing eukaryotic linear DNA; when this does not occur DNA is lost and end-replication problems arise. Telomerase is reactivated in 80-90% of cancers thus attracting the attention of pathologists and clinicians who have explored its use as a target for anticancer therapy and to develop better diagnostic and prognostic markers. In the last few years, valuable research from various laboratories has provided major insights into telomerase and telomeres leading to their use as diagnostic and prognostic markers in several types of cancer. Moreover, many strategies have emerged which inhibit this complex enzyme for anticancer therapy and are one step ahead of clinical trials. This review explains the basic biology and the clinical implications of telomerase-based diagnosis and prognosis, the prospects for its use in anticancer therapy, and the limitations it presents in the context of oral cancer.

  15. Early-Life Telomere Dynamics Differ between the Sexes and Predict Growth in the Barn Swallow (Hirundo rustica.

    Directory of Open Access Journals (Sweden)

    Marco Parolini

    Full Text Available Telomeres are conserved DNA-protein structures at the termini of eukaryotic chromosomes which contribute to maintenance of genome integrity, and their shortening leads to cell senescence, with negative consequences for organismal functions. Because telomere erosion is influenced by extrinsic and endogenous factors, telomere dynamics may provide a mechanistic basis for evolutionary and physiological trade-offs. Yet, knowledge of fundamental aspects of telomere biology under natural selection regimes, including sex- and context-dependent variation in early-life, and the covariation between telomere dynamics and growth, is scant. In this study of barn swallows (Hirundo rustica we investigated the sex-dependent telomere erosion during nestling period, and the covariation between relative telomere length and body and plumage growth. Finally, we tested whether any covariation between growth traits and relative telomere length depends on the social environment, as influenced by sibling sex ratio. Relative telomere length declined on average over the period of nestling maximal growth rate (between 7 and 16 days of age and differently covaried with initial relative telomere length in either sex. The frequency distribution of changes in relative telomere length was bimodal, with most nestlings decreasing and some increasing relative telomere length, but none of the offspring traits predicted the a posteriori identified group to which individual nestlings belonged. Tail and wing length increased with relative telomere length, but more steeply in males than females, and this relationship held both at the within- and among-broods levels. Moreover, the increase in plumage phenotypic values was steeper when the sex ratio of an individual's siblings was female-biased. Our study provides evidence for telomere shortening during early life according to subtly different dynamics in either sex. Furthermore, it shows that the positive covariation between growth and

  16. Correlating telomere length and radiosensitivity in cancer patients

    International Nuclear Information System (INIS)

    Sprung, C.N.; Davey, D.S.P.; McKay, M.J.

    2003-01-01

    Approximately three percent of cancer patients suffer from significant side effects in normal tissue exposed to ionising radiation during radiotherapy (RT). Although RT is an effective therapy for cancer treatment, the treatment dose intensity is generally restricted to minimize the incidence of these severe reactions. This imposes tumour control limitations on most patients. A major goal of radiation biology research is to develop efficient predictive assays that could identify these hyper-radiosensitive (hRS) individuals prior to treatment. This predictive ability would enable the individualisation of RT doses, which should result in improvement of tumour control rates and a reduction in the incidence of RT side effects. Recent studies have reported a correlation between cellular and organismal RS and shortened telomeres. Interestingly, a number of DNA repair proteins have been found to be associated with telomeres. Additionally, individuals with cancer-proneness and RS syndromes, such as ataxia telangiectasia and Fanconi anemia, have shortened telomeres. In animal models, mutations in DNA repair genes such as Ku, has resulted in shortened telomeres. We have a unique bank of blood samples and lymphoblastoid cell lines (LCLs) from over 50 hRS patients. We have used traditional methods of telomere length assessment and a clinically relevant method, flow cytometry fluorescence in situ hybridisation (flow-FISH) to determine the telomere length in both LCLs and peripheral blood mononuclear cells from the hRS patients. Results from the screening of these samples will be presented. If clinical hRS can be correlated with shortened telomeres in some patients, flow-FISH may have utility as part of a pre-treatment hRS assay for use in the clinic

  17. Re: Role of Telomeres and Telomerase in Cancer

    Directory of Open Access Journals (Sweden)

    Shay JW

    2016-03-01

    Full Text Available The most important difference between cancer and normall cells is the ability to continuous proliferation. This activation works due to telomeres and telomerase enzyme. Fifty years ago, Leonard Hayflick discovered that cultured normal humans cells have a limited capacity to divide. Today, this withdrawal from the cell cycle after a certain number of cellular divisions (replicative senescence is known to be triggered as a result of shortened telomeres. Studies on telomeres and telomerase have begun to provide additional information about aging and cancer development and have created new opportunities in the field of regenerative medicine for telomeropathies. Progressive telomere shortening from cell division (replicative aging provides a barrier for tumor progression. Continuous cell growth in malignancy correlates with the reactivation of telomerase. Telomerase is a cellular reverse transcriptase that adds new deoxyribonucleic acid (DNA onto the telomeres that are located at the ends of chromosomes. Telomeres consist of many kilobases of TTAGGG nucleotide repeats. The telomeric nucleotide repeats shorten with each cell division due to replication problems (DNA repair and oxidative damage. Quiescent/senescent state of the cell bypass can be accomplished by abrogating cell cycle checkpoint genes (such as TP53, p16INK4a, pRb. Telomerase is detected in approximately 90% of all malignant tumors. This telomerase activation has emerged as a target for cancer treatment. Telomerase therapeutics are classified as gene therapy (hTERT-telomerase catalytic protein component, hTR-telomerase functional, immunotherapy (Imetalstat-telomerase template antagonist, and small molecule inhibitors. In the near future, more specific researches on telomers and telomerase will contribute to aging/immortality studies (as stem cells and to discover new biomarkers for malignant tissue or anticancer therapeutics.

  18. Short fetal leukocyte telomere length and preterm prelabor rupture of the membranes.

    Directory of Open Access Journals (Sweden)

    Ramkumar Menon

    Full Text Available BACKGROUND: Rupture of the fetal membranes is a common harbinger of imminent labor and delivery. Telomere shortening is a surrogate for oxidative stress (OS and senescence. Fetal leukocyte and placental membrane DNA telomere lengths were evaluated to determine their association with preterm prelabor rupture of the membranes (pPROM or spontaneous preterm births with intact membranes (PTB, compared to term birth. METHODS: Telomere lengths were quantified in cord blood leukocytes (n = 133 from three major groups: 1 pPROM (n = 28, 2 PTB (n = 69 and 3 uncomplicated full term births (controls, n = 35, using real-time quantitative PCR. Placental membrane specimens (n = 18 were used to correlate fetal leukocyte and placental telomere lengths. Telomere length differences among the groups were analyzed by ANOVA. Pearson correlation coefficients determined relationships between leukocyte and placental membrane telomere lengths. RESULTS: In pregnancies with intact membranes, fetal leukocyte telomere length was inversely proportional to gestational age. The mean telomere length decreased as gestation progressed, with the shortest at term. pPROM had telomere lengths (9962 ± 3124 bp that were significantly shorter than gestational age-matched PTB (11546 ± 4348 bp, p = 0.04, but comparable to term births (9011 ± 2497 bp, p = 0.31. Secondary analyses revealed no effects of race (African American vs. Caucasian or intraamniotic infection on telomere length. A strong Pearson's correlation was noted between fetal leukocyte and placental membrane telomere lengths (ρ = 0.77; p<0.01. CONCLUSIONS: Fetal leukocyte telomere length is reduced in pPROM compared to PTB but is similar to term births. pPROM represents a placental membrane disease likely mediated by OS-induced senescence.

  19. Prognostic Significance of Telomere Attrition in Ductal Carcinoma in Situ of the Breast

    National Research Council Canada - National Science Library

    Griffith, Jeffrey K

    2008-01-01

    We are using an innovative, quantitative assay for telomere DNA content (TC) developed and characterized by the PI, to test the hypothesis that TC predicts the likelihood of disease recurrence in women with ductal carcinoma in situ (DCIS...

  20. CTC1-STN1 coordinates G- and C-strand synthesis to regulate telomere length.

    Science.gov (United States)

    Gu, Peili; Jia, Shuting; Takasugi, Taylor; Smith, Eric; Nandakumar, Jayakrishnan; Hendrickson, Eric; Chang, Sandy

    2018-05-17

    Coats plus (CP) is a rare autosomal recessive disorder caused by mutations in CTC1, a component of the CST (CTC1, STN1, and TEN1) complex important for telomere length maintenance. The molecular basis of how CP mutations impact upon telomere length remains unclear. The CP CTC1 L1142H mutation has been previously shown to disrupt telomere maintenance. In this study, we used CRISPR/Cas9 to engineer this mutation into both alleles of HCT116 and RPE cells to demonstrate that CTC1:STN1 interaction is required to repress telomerase activity. CTC1 L1142H interacts poorly with STN1, leading to telomerase-mediated telomere elongation. Impaired interaction between CTC1 L1142H :STN1 and DNA Pol-α results in increased telomerase recruitment to telomeres and further telomere elongation, revealing that C:S binding to DNA Pol-α is required to fully repress telomerase activity. CP CTC1 mutants that fail to interact with DNA Pol-α resulted in loss of C-strand maintenance and catastrophic telomere shortening. Our findings place the CST complex as an important regulator of both G-strand extensions by telomerase and C-strand synthesis by DNA Pol-α. © 2018 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  1. NBS1 plays a synergistic role with telomerase in the maintenance of telomeres in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Najdekrova Lucie

    2012-09-01

    Full Text Available Abstract Background Telomeres, as elaborate nucleo-protein complexes, ensure chromosomal stability. When impaired, the ends of linear chromosomes can be recognised by cellular repair mechanisms as double-strand DNA breaks and can be healed by non-homologous-end-joining activities to produce dicentric chromosomes. During cell divisions, particularly during anaphase, dicentrics can break, thus producing naked chromosome tips susceptible to additional unwanted chromosome fusion. Many telomere-building protein complexes are associated with telomeres to ensure their proper capping function. It has been found however, that a number of repair complexes also contribute to telomere stability. Results We used Arabidopsis thaliana to study the possible functions of the DNA repair subunit, NBS1, in telomere homeostasis using knockout nbs1 mutants. The results showed that although NBS1-deficient plants were viable, lacked any sign of developmental aberration and produced fertile seeds through many generations upon self-fertilisation, plants also missing the functional telomerase (double mutants, rapidly, within three generations, displayed severe developmental defects. Cytogenetic inspection of cycling somatic cells revealed a very early onset of massive genome instability. Molecular methods used for examining the length of telomeres in double homozygous mutants detected much faster telomere shortening than in plants deficient in telomerase gene alone. Conclusions Our findings suggest that NBS1 acts in concert with telomerase and plays a profound role in plant telomere renewal.

  2. NBS1 plays a synergistic role with telomerase in the maintenance of telomeres in Arabidopsis thaliana.

    Science.gov (United States)

    Najdekrova, Lucie; Siroky, Jiri

    2012-09-17

    Telomeres, as elaborate nucleo-protein complexes, ensure chromosomal stability. When impaired, the ends of linear chromosomes can be recognised by cellular repair mechanisms as double-strand DNA breaks and can be healed by non-homologous-end-joining activities to produce dicentric chromosomes. During cell divisions, particularly during anaphase, dicentrics can break, thus producing naked chromosome tips susceptible to additional unwanted chromosome fusion. Many telomere-building protein complexes are associated with telomeres to ensure their proper capping function. It has been found however, that a number of repair complexes also contribute to telomere stability. We used Arabidopsis thaliana to study the possible functions of the DNA repair subunit, NBS1, in telomere homeostasis using knockout nbs1 mutants. The results showed that although NBS1-deficient plants were viable, lacked any sign of developmental aberration and produced fertile seeds through many generations upon self-fertilisation, plants also missing the functional telomerase (double mutants), rapidly, within three generations, displayed severe developmental defects. Cytogenetic inspection of cycling somatic cells revealed a very early onset of massive genome instability. Molecular methods used for examining the length of telomeres in double homozygous mutants detected much faster telomere shortening than in plants deficient in telomerase gene alone. Our findings suggest that NBS1 acts in concert with telomerase and plays a profound role in plant telomere renewal.

  3. Drosophila: Retrotransposons Making up Telomeres.

    Science.gov (United States)

    Casacuberta, Elena

    2017-07-19

    Drosophila and extant species are the best-studied telomerase exception. In this organism, telomere elongation is coupled with targeted retrotransposition of Healing Transposon (HeT-A) and Telomere Associated Retrotransposon (TART) with sporadic additions of Telomere Associated and HeT-A Related (TAHRE), all three specialized non-Long Terminal Repeat (non-LTR) retrotransposons. These three very special retroelements transpose in head to tail arrays, always in the same orientation at the end of the chromosomes but never in interior locations. Apparently, retrotransposon and telomerase telomeres might seem very different, but a detailed view of their mechanisms reveals similarities explaining how the loss of telomerase in a Drosophila ancestor could successfully have been replaced by the telomere retrotransposons. In this review, we will discover that although HeT-A, TART, and TAHRE are still the only examples to date where their targeted transposition is perfectly tamed into the telomere biology of Drosophila, there are other examples of retrotransposons that manage to successfully integrate inside and at the end of telomeres. Because the aim of this special issue is viral integration at telomeres, understanding the base of the telomerase exceptions will help to obtain clues on similar strategies that mobile elements and viruses could have acquired in order to ensure their survival in the host genome.

  4. Regulation of Telomere Homeostasis during Epstein-Barr virus Infection and Immortalization.

    Science.gov (United States)

    Kamranvar, Siamak A; Masucci, Maria G

    2017-08-09

    The acquisition of unlimited proliferative potential is dependent on the activation of mechanisms for telomere maintenance, which counteracts telomere shortening and the consequent triggering of the DNA damage response, cell cycle arrest, and apoptosis. The capacity of Epstein Barr virus (EBV) to infect B-lymphocytes in vitro and transform the infected cells into autonomously proliferating immortal cell lines underlies the association of this human gamma-herpesvirus with a broad variety of lymphoid and epithelial cell malignancies. Current evidence suggests that both telomerase-dependent and -independent pathways of telomere elongation are activated in the infected cells during the early and late phases of virus-induced immortalization. Here we review the interaction of EBV with different components of the telomere maintenance machinery and the mechanisms by which the virus regulates telomere homeostasis in proliferating cells. We also discuss how these viral strategies may contribute to malignant transformation.

  5. Different requirements of functional telomeres in neural stem cells and terminally differentiated neurons.

    Science.gov (United States)

    Lobanova, Anastasia; She, Robert; Pieraut, Simon; Clapp, Charlie; Maximov, Anton; Denchi, Eros Lazzerini

    2017-04-01

    Telomeres have been studied extensively in peripheral tissues, but their relevance in the nervous system remains poorly understood. Here, we examine the roles of telomeres at distinct stages of murine brain development by using lineage-specific genetic ablation of TRF2, an essential component of the shelterin complex that protects chromosome ends from the DNA damage response machinery. We found that functional telomeres are required for embryonic and adult neurogenesis, but their uncapping has surprisingly no detectable consequences on terminally differentiated neurons. Conditional knockout of TRF2 in post-mitotic immature neurons had virtually no detectable effect on circuit assembly, neuronal gene expression, and the behavior of adult animals despite triggering massive end-to-end chromosome fusions across the brain. These results suggest that telomeres are dispensable in terminally differentiated neurons and provide mechanistic insight into cognitive abnormalities associated with aberrant telomere length in humans. © 2017 Lobanova et al.; Published by Cold Spring Harbor Laboratory Press.

  6. Telomere Homeostasis: Interplay with Magnesium

    Directory of Open Access Journals (Sweden)

    Donogh Maguire

    2018-01-01

    Full Text Available Telomere biology, a key component of the hallmarks of ageing, offers insight into dysregulation of normative ageing processes that accompany age-related diseases such as cancer. Telomere homeostasis is tightly linked to cellular metabolism, and in particular with mitochondrial physiology, which is also diminished during cellular senescence and normative physiological ageing. Inherent in the biochemistry of these processes is the role of magnesium, one of the main cellular ions and an essential cofactor in all reactions that use ATP. Magnesium plays an important role in many of the processes involved in regulating telomere structure, integrity and function. This review explores the mechanisms that maintain telomere structure and function, their influence on circadian rhythms and their impact on health and age-related disease. The pervasive role of magnesium in telomere homeostasis is also highlighted.

  7. Telomeres and Telomerase in the Radiation Response: implications for instability, reprogramming, and carcinogenesis

    Directory of Open Access Journals (Sweden)

    Brock James Sishc

    2015-11-01

    Full Text Available Telomeres are nucleoprotein complexes comprised of tandem arrays of repetitive DNA sequence that serve to protect chromosomal termini from inappropriate degradation, as well as to prevent these natural DNA ends from being recognized as broken DNA (double-strand breaks; DSBs and triggering of inappropriate DNA damage responses. Preservation of telomere length requires telomerase, the specialized reverse transcriptase capable of maintaining telomere length via template-mediated addition of telomeric repeats onto the ends of newly synthesized chromosomes. Loss of either end-capping function or telomere length maintenance has been associated with genomic instability or senescence in a variety of settings; therefore telomeres and telomerase have well-established connections to cancer and aging. It has long been recognized that oxidative stress promotes shortening of telomeres, and that telomerase activity is a radiation-inducible function. However, the effects of ionizing radiation (IR exposure on telomeres per se are much less well understood and appreciated. To gain a deeper understanding of the roles telomeres and telomerase play in the response of human cells to ionizing radiations of different qualities, we tracked changes in telomeric end-capping function, telomere length, and telomerase activity in panels of mammary epithelial and hematopoietic cell lines exposed to low linear energy transfer (LET gamma(γ-rays or high LET high charge, high energy (HZE particles, delivered either acutely or at low dose rates (LDR. In addition to demonstrating that dysfunctional telomeres contribute to IR-induced mutation frequencies and genome instability, we reveal non-canonical roles for telomerase, in that telomerase activity was required for IR-induced enrichment of mammary epithelial putative stem/progenitor cell populations, a finding also suggestive of cellular reprogramming. Taken together, the results reported here establish the critical importance of

  8. Influence of exposure to pesticides on telomere length in tobacco farmers: A biology system approach

    Energy Technology Data Exchange (ETDEWEB)

    Kahl, Vivian Francília Silva [Laboratory of Genetic Toxicology, PPGBioSaúde and PPGGTA, Lutheran University of Brazil (ULBRA), Canoas, RS (Brazil); Silva, Juliana da, E-mail: juliana.silva@ulbra.br [Laboratory of Genetic Toxicology, PPGBioSaúde and PPGGTA, Lutheran University of Brazil (ULBRA), Canoas, RS (Brazil); Rabaioli da Silva, Fernanda, E-mail: fernanda.silva@unilasalle.edu.br [Master’s Degree in Environmental Impact Evaluation, Centro Universitário La Salle, Canoas, RS (Brazil)

    2016-09-15

    Highlights: • Exposure to pesticides in tobacco fields is related to shorten telomere length. • The molecular mechanism of pesticide on telomere length is not fully understood. • Pesticides inhibit ubiquitin proteasome system. • Nicotine activates ubiquitin proteasome system. • Pesticides and nicotine regulate telomere length. - Abstract: Various pesticides in the form of mixtures must be used to keep tobacco crops pest-free. Recent studies have shown a link between occupational exposure to pesticides in tobacco crops and increased damage to the DNA, mononuclei, nuclear buds and binucleated cells in buccal cells as well as micronuclei in lymphocytes. Furthermore, pesticides used specifically for tobacco crops shorten telomere length (TL) significantly. However, the molecular mechanism of pesticide action on telomere length is not fully understood. Our study evaluated the interaction between a complex mixture of chemical compounds (tobacco cultivation pesticides plus nicotine) and proteins associated with maintaining TL, as well as the biological processes involved in this exposure by System Biology tools to provide insight regarding the influence of pesticide exposure on TL maintenance in tobacco farmers. Our analysis showed that one cluster was associated with TL proteins that act in bioprocesses such as (i) telomere maintenance via telomere lengthening; (ii) senescence; (iii) age-dependent telomere shortening; (iv) DNA repair (v) cellular response to stress and (vi) regulation of proteasome ubiquitin-dependent protein catabolic process. We also describe how pesticides and nicotine regulate telomere length. In addition, pesticides inhibit the ubiquitin proteasome system (UPS) and consequently increase proteins of the shelterin complex, avoiding the access of telomerase in telomere and, nicotine activates UPS mechanisms and promotes the degradation of human telomerase reverse transcriptase (hTERT), decreasing telomerase activity.

  9. Influence of exposure to pesticides on telomere length in tobacco farmers: A biology system approach

    International Nuclear Information System (INIS)

    Kahl, Vivian Francília Silva; Silva, Juliana da; Rabaioli da Silva, Fernanda

    2016-01-01

    Highlights: • Exposure to pesticides in tobacco fields is related to shorten telomere length. • The molecular mechanism of pesticide on telomere length is not fully understood. • Pesticides inhibit ubiquitin proteasome system. • Nicotine activates ubiquitin proteasome system. • Pesticides and nicotine regulate telomere length. - Abstract: Various pesticides in the form of mixtures must be used to keep tobacco crops pest-free. Recent studies have shown a link between occupational exposure to pesticides in tobacco crops and increased damage to the DNA, mononuclei, nuclear buds and binucleated cells in buccal cells as well as micronuclei in lymphocytes. Furthermore, pesticides used specifically for tobacco crops shorten telomere length (TL) significantly. However, the molecular mechanism of pesticide action on telomere length is not fully understood. Our study evaluated the interaction between a complex mixture of chemical compounds (tobacco cultivation pesticides plus nicotine) and proteins associated with maintaining TL, as well as the biological processes involved in this exposure by System Biology tools to provide insight regarding the influence of pesticide exposure on TL maintenance in tobacco farmers. Our analysis showed that one cluster was associated with TL proteins that act in bioprocesses such as (i) telomere maintenance via telomere lengthening; (ii) senescence; (iii) age-dependent telomere shortening; (iv) DNA repair (v) cellular response to stress and (vi) regulation of proteasome ubiquitin-dependent protein catabolic process. We also describe how pesticides and nicotine regulate telomere length. In addition, pesticides inhibit the ubiquitin proteasome system (UPS) and consequently increase proteins of the shelterin complex, avoiding the access of telomerase in telomere and, nicotine activates UPS mechanisms and promotes the degradation of human telomerase reverse transcriptase (hTERT), decreasing telomerase activity.

  10. The protein network surrounding the human telomere repeat binding factors TRF1, TRF2, and POT1.

    Directory of Open Access Journals (Sweden)

    Richard J Giannone

    2010-08-01

    Full Text Available Telomere integrity (including telomere length and capping is critical in overall genomic stability. Telomere repeat binding factors and their associated proteins play vital roles in telomere length regulation and end protection. In this study, we explore the protein network surrounding telomere repeat binding factors, TRF1, TRF2, and POT1 using dual-tag affinity purification in combination with multidimensional protein identification technology liquid chromatography--tandem mass spectrometry (MudPIT LC-MS/MS. After control subtraction and data filtering, we found that TRF2 and POT1 co-purified all six members of the telomere protein complex, while TRF1 identified five of six components at frequencies that lend evidence towards the currently accepted telomere architecture. Many of the known TRF1 or TRF2 interacting proteins were also identified. Moreover, putative associating partners identified for each of the three core components fell into functional categories such as DNA damage repair, ubiquitination, chromosome cohesion, chromatin modification/remodeling, DNA replication, cell cycle and transcription regulation, nucleotide metabolism, RNA processing, and nuclear transport. These putative protein-protein associations may participate in different biological processes at telomeres or, intriguingly, outside telomeres.

  11. Caspase-Dependent Apoptosis Induced by Telomere Cleavage and TRF2 Loss

    Directory of Open Access Journals (Sweden)

    Asha S. Multani

    2000-07-01

    Full Text Available Chromosomal abnormalities involving telomeric associations (TAs often precede replicative senescence and abnormal chromosome configurations. We report here that telomere cleavage following exposure to proapoptotic agents is an early event in apoptosis. Exposure of human and murine cancer cells to a variety of pro-apoptotic stimuli (staurosporine, thapsigargin, anti-Fas antibody, cancer chemotherapeutic agents resulted in telomere cleavage and aggregation, finally their extrusion from the nuclei. Telomere loss was associated with arrest of cells in G2/M phase and preceded DNA fragmentation. Telomere erosion and subsequent large-scale chromatin cleavage were inhibited by overexpression of the anti -apoptotic protein, bcl-2, two peptide caspase inhibitors (BACMK and zVADfmk, indicating that both events are regulated by caspase activation. The results demonstrate that telomere cleavage is an early chromatin alteration detected in various cancer cell lines leading to drug-induced apoptosis, suggest that this event contributes to mitotic catastrophe and induction of cell death. Results also suggest that the decrease of telomeric-repeat binding factor 2 (TRF2 may be the earliest event in the ara-C-induced telomere shortening, induction of endoreduplication and chromosomal fragmentation leading to cell death.

  12. Blood and dried blood spot telomere length measurement by qPCR: assay considerations.

    Directory of Open Access Journals (Sweden)

    DeAnna L Zanet

    Full Text Available Measurement of telomere length is crucial for the study of telomere maintenance and its role in molecular pathophysiology of diseases and in aging. Several methods are used to measure telomere length, the choice of which usually depends on the type and size of sample to be assayed, as well as cost and throughput considerations. The goal of this study was to investigate the factors that may influence the reliability of qPCR-based relative telomere length measurements in whole blood. Day to day intra-individual variability, types of blood anticoagulant, sample storage conditions, processing and site of blood draw were investigated. Two qPCR-based methods to measure telomere length (monoplex vs. multiplex were also investigated and showed a strong correlation between them. Freezing and thawing of the blood and storage of the blood at 4°C for up to 4 days did not affect telomere length values. Telomere lengths in dried blood spots were significantly higher than both whole blood and peripheral mononuclear blood cells, and were highly correlated with both. We found that telomere length measurements were significantly higher in dried blood spots collected directly from fingertip prick compared to dried blood spots prepared with anticoagulated whole blood collected from the finger, and non-blotted whole blood taken from both finger and arm venipuncture. This suggests that DNA from cells blotted on paper is not equivalent to that collected from venipuncture whole blood, and caution should be taken when comparing between blood sample types.

  13. Telomerase and Tel1p Preferentially Associate with Short Telomeres in S. cerevisiae

    Science.gov (United States)

    Sabourin, Michelle; Tuzon, Creighton T.; Zakian, Virginia A.

    2009-01-01

    SUMMARY In diverse organisms, telomerase preferentially elongates short telomeres. We generated a single short telomere in otherwise wild-type (WT) S. cerevisiae cells. The binding of the positive regulators Ku and Cdc13p was similar at short and WT-length telomeres. The negative regulators Rif1p and Rif2p were present at the short telomere, although Rif2p levels were reduced. Two telomerase holoenzyme components, Est1p and Est2p, were preferentially enriched at short telomeres in late S/G2 phase, the time of telomerase action. Tel1p, the yeast ATM-like checkpoint kinase, was highly enriched at short telomeres from early S through G2 phase and even into the next cell cycle. Nonetheless, induction of a single short telomere did not elicit a cell-cycle arrest. Tel1p binding was dependent on Xrs2p and required for preferential binding of telomerase to short telomeres. These data suggest that Tel1p targets telomerase to the DNA ends most in need of extension. PMID:17656141

  14. Solid-state NMR chemical-shift perturbations indicate domain reorientation of the DnaG primase in the primosome of Helicobacter pylori

    Energy Technology Data Exchange (ETDEWEB)

    Gardiennet, Carole [Université de Lorraine, CNRS, CRM2, UMR 7036 (France); Wiegand, Thomas [ETH Zurich, Physical Chemistry (Switzerland); Bazin, Alexandre [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Cadalbert, Riccardo [ETH Zurich, Physical Chemistry (Switzerland); Kunert, Britta; Lacabanne, Denis [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Gutsche, Irina [Université Grenoble Alpes, Institut de Biologie Structurale (IBS), CNRS, IBS, CEA, IBS (France); Terradot, Laurent, E-mail: l.terradot@ibcp.fr [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Meier, Beat H., E-mail: beme@ethz.ch [ETH Zurich, Physical Chemistry (Switzerland); Böckmann, Anja, E-mail: a.bockmann@ibcp.fr [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France)

    2016-03-15

    We here investigate the interactions between the DnaB helicase and the C-terminal domain of the corresponding DnaG primase of Helicobacter pylori using solid-state NMR. The difficult crystallization of this 387 kDa complex, where the two proteins interact in a six to three ratio, is circumvented by simple co-sedimentation of the two proteins directly into the MAS-NMR rotor. While the amount of information that can be extracted from such a large protein is still limited, we can assign a number of amino-acid residues experiencing significant chemical-shift perturbations upon helicase-primase complex formation. The location of these residues is used as a guide to model the interaction interface between the two proteins in the complex. Chemical-shift perturbations also reveal changes at the interaction interfaces of the hexameric HpDnaB assembly on HpDnaG binding. A structural model of the complex that explains the experimental findings is obtained.

  15. Influence of exposure to pesticides on telomere length in tobacco farmers: A biology system approach.

    Science.gov (United States)

    Kahl, Vivian Francília Silva; da Silva, Juliana; da Silva, Fernanda Rabaioli

    Various pesticides in the form of mixtures must be used to keep tobacco crops pest-free. Recent studies have shown a link between occupational exposure to pesticides in tobacco crops and increased damage to the DNA, mononuclei, nuclear buds and binucleated cells in buccal cells as well as micronuclei in lymphocytes. Furthermore, pesticides used specifically for tobacco crops shorten telomere length (TL) significantly. However, the molecular mechanism of pesticide action on telomere length is not fully understood. Our study evaluated the interaction between a complex mixture of chemical compounds (tobacco cultivation pesticides plus nicotine) and proteins associated with maintaining TL, as well as the biological processes involved in this exposure by System Biology tools to provide insight regarding the influence of pesticide exposure on TL maintenance in tobacco farmers. Our analysis showed that one cluster was associated with TL proteins that act in bioprocesses such as (i) telomere maintenance via telomere lengthening; (ii) senescence; (iii) age-dependent telomere shortening; (iv) DNA repair (v) cellular response to stress and (vi) regulation of proteasome ubiquitin-dependent protein catabolic process. We also describe how pesticides and nicotine regulate telomere length. In addition, pesticides inhibit the ubiquitin proteasome system (UPS) and consequently increase proteins of the shelterin complex, avoiding the access of telomerase in telomere and, nicotine activates UPS mechanisms and promotes the degradation of human telomerase reverse transcriptase (hTERT), decreasing telomerase activity. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Hybrid ligand-alkylating agents targeting telomeric G-quadruplex structures.

    Science.gov (United States)

    Doria, Filippo; Nadai, Matteo; Folini, Marco; Di Antonio, Marco; Germani, Luca; Percivalle, Claudia; Sissi, Claudia; Zaffaroni, Nadia; Alcaro, Stefano; Artese, Anna; Richter, Sara N; Freccero, Mauro

    2012-04-14

    The synthesis, physico-chemical properties and biological effects of a new class of naphthalene diimides (NDIs) capable of reversibly binding telomeric DNA and alkylate it through an electrophilic quinone methide moiety (QM), are reported. FRET and circular dichroism assays showed a marked stabilization and selectivity towards telomeric G4 DNA folded in a hybrid topology. NDI-QMs' alkylating properties revealed a good reactivity on single nucleosides and selectivity towards telomeric G4. A selected NDI was able to significantly impair the growth of melanoma cells by causing telomere dysfunction and down-regulation of telomerase expression. These findings points to our hybrid ligand-alkylating NDIs as possible tools for the development of novel targeted anticancer therapies. This journal is © The Royal Society of Chemistry 2012

  17. Leukocyte Telomere Length and Cognitive Function in Older Adults

    Directory of Open Access Journals (Sweden)

    Emily Frith

    2018-04-01

    Full Text Available We evaluated the specific association between leukocyte telomere length and cognitive function among a national sample of the broader U.S. older adult population. Data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES were used to identify 1,722 adults, between 60-85 years, with complete data on selected study variables. DNA was extracted from whole blood via the LTL assay, which is administered using quantitative polymerase chain reaction to measure telomere length relative to standard reference DNA (T/S ratio. Average telomere length was recorded, with two to three assays performed to control for individual variability. The DSST (Digit Symbol Substitution Test was used to assess participant executive cognitive functioning tasks of pairing and free recall. Individuals were excluded if they had been diagnosed with coronary artery disease, congestive heart failure, heart attack or stroke at the baseline assessment. Leukocyte telomere length was associated with higher cognitive performance, independent of gender, race-ethnicity, physical activity status, body mass index and other covariates. In this sample, there was a strong association between LTL and cognition; for every 1 T/S ratio increase in LTL, there was a corresponding 9.9 unit increase in the DSST (β = 9.9; 95% CI: 5.6-14.2; P [JCBPR 2018; 7(1.000: 14-18

  18. n-3 Fatty Acid Supplementation and Leukocyte Telomere Length in Patients with Chronic Kidney Disease

    Directory of Open Access Journals (Sweden)

    Anne Barden

    2016-03-01

    Full Text Available DNA telomere shortening associates with the age-related increase cardiovascular disease (CVD risk. Reducing oxidative stress, could modify telomere erosion during cell replication, and CVD risk in patients with chronic kidney disease (CKD. The effect of n-3 fatty acids and coenzyme Q10 (CoQ on telomere length was studied in a double-blind placebo-controlled trial in CKD. Eighty-five CKD patients were randomized to: n-3 fatty acids (4 g; CoQ (200 mg; both supplements; or control (4 g olive oil, daily for 8 weeks. Telomere length was measured in neutrophils and peripheral blood mononuclear cells (PBMC at baseline and 8 weeks, with and without correction for cell counts. Main and interactive effects of n-3 fatty acids and CoQ on telomere length were assessed adjusting for baseline values. F2-isoprostanes were measured as markers of oxidative stress. There was no effect of n-3 fatty acids or CoQ on neutrophil or PBMC telomere length. However, telomere length corrected for neutrophil count was increased after n-3 fatty acids (p = 0.015. Post-intervention plasma F2-isoprostanes were negative predictors of post-intervention telomere length corrected for neutrophil count (p = 0.025.The effect of n-3 fatty acids to increased telomere length corrected for neutrophil count may relate to reduced oxidative stress and increased clearance of neutrophils with shorter telomeres from the circulation. This may be a novel mechanism of modifying CVD risk in CKD patients.

  19. The long and the short of telomeres in bone marrow recipient SCID patients

    OpenAIRE

    Sarzotti-Kelsoe, Marcella; Daniell, Xiaoju G.; Whitesides, John F.; Buckley, Rebecca H.

    2011-01-01

    Telomeres are noncoding DNA regions at the end of the chromosomes that are crucial for genome stability. Since telomere length decreases with cell division, they can be used as a signature of cell proliferation history. T-cell reconstitution in severe combined immunodeficiency (SCID) subjects, recipients of T-cell-depleted, allogeneic-related bone marrow cells, is due to the development and maturation of donor T-cell precursors in the infant’s vestigial thymus and to homeostatic proliferation...

  20. Binding polarity of RPA to telomeric sequences and influence of G-quadruplex stability.

    Science.gov (United States)

    Safa, Layal; Delagoutte, Emmanuelle; Petruseva, Irina; Alberti, Patrizia; Lavrik, Olga; Riou, Jean-François; Saintomé, Carole

    2014-08-01

    Replication protein A (RPA) is a single-stranded DNA binding protein that plays an essential role in telomere maintenance. RPA binds to and unfolds G-quadruplex (G4) structures formed in telomeric DNA, thus facilitating lagging strand DNA replication and telomerase activity. To investigate the effect of G4 stability on the interactions with human RPA (hRPA), we used a combination of biochemical and biophysical approaches. Our data revealed an inverse relationship between G4 stability and ability of hRPA to bind to telomeric DNA; notably small G4 ligands that enhance G4 stability strongly impaired G4 unfolding by hRPA. To gain more insight into the mechanism of binding and unfolding of telomeric G4 structures by RPA, we carried out photo-crosslinking experiments to elucidate the spatial arrangement of the RPA subunits along the DNA strands. Our results showed that RPA1 and RPA2 are arranged from 5' to 3' along the unfolded telomeric G4, as already described for unstructured single-stranded DNA, while no contact is possible with RPA3 on this short oligonucleotide. In addition, these data are compatible with a 5' to 3' directionality in G4 unfolding by hRPA. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  1. Is telomere erosion a mechanism of species extinction?

    Science.gov (United States)

    Stindl, Reinhard

    2004-03-15

    According to the fossil record, 99.9% of all species that have ever lived on Earth have disappeared. However, only about 4% died out during the five mass extinction events, whereas it seems that the majority of species vanished without any signs of significant earthbound or extraterrestrial physical threats. Clearly, biological extinction mechanisms are by far the most important, but they are subject to serious limitations concerning the worldwide disappearance of species. In view of that, species-inherent mechanisms, which could lead to the worldwide destabilization of a population, might be worth reconsideration. Telomeres, the protective caps of chromosome ends, and the enzyme telomerase have been well preserved in plants and animals during evolution. In the absence of telomerase activity, telomeric DNA has been shown to shorten every time a cell divides. The concept of a mitotic clock based on the gradual erosion of telomeres is now generally accepted and has been confirmed in numerous plants and animals. Chromosomal rearrangements are the hallmarks of two completely different biological phenomena, cancer and speciation. In premalignant cells, gradual telomere erosion beyond a critical threshold is a well-known inducer of chromosomal instability. The species clock hypothesis, as presented here, is based on the idea of a tiny loss of mean telomere length per generation. This mechanism would not rapidly endanger the survival of a particular species. Yet, after many thousands of generations, critically short telomeres could lead to the weakening and even the extinction of old species and would simultaneously create the unstable chromosomal environment that might result in the origination of new species. Copyright 2004 Wiley-Liss, Inc.

  2. Chemosensitivity of human small cell carcinoma of the lung detected by flow cytometric DNA analysis of drug-induced cell cycle perturbations in vitro

    DEFF Research Database (Denmark)

    Engelholm, S A; Spang-Thomsen, M; Vindeløv, L L

    1986-01-01

    A method based on detection of drug-induced cell cycle perturbation by flow cytometric DNA analysis has previously been described in Ehrlich ascites tumors as a way to estimate chemosensitivity. The method is extended to test human small-cell carcinoma of the lung. Three tumors with different...... sensitivities to melphalan in nude mice were used. Tumors were disaggregated by a combined mechanical and enzymatic method and thereafter have incubated with different doses of melphalan. After incubation the cells were plated in vitro on agar, and drug induced cell cycle changes were monitored by flow...

  3. Telomere Length Polymorphisms: A Potential Factor Underlying Increased Risk of Prostate Cancer in African American Men and Familial Prostate Cancer

    National Research Council Canada - National Science Library

    Meeker, Alan K

    2007-01-01

    .... To test this hypothesis, telomere content in genomic DNA isolated from blood samples of relevant cohorts will be determined and assessed for associations with either racial background or prostate...

  4. Distinct Responses of Stem Cells to Telomere Uncapping-A Potential Strategy to Improve the Safety of Cell Therapy.

    Science.gov (United States)

    Liu, Chang Ching; Ma, Dong Liang; Yan, Ting-Dong; Fan, XiuBo; Poon, Zhiyong; Poon, Lai-Fong; Goh, Su-Ann; Rozen, Steve G; Hwang, William Ying Khee; Tergaonkar, Vinay; Tan, Patrick; Ghosh, Sujoy; Virshup, David M; Goh, Eyleen L K; Li, Shang

    2016-10-01

    In most human somatic cells, the lack of telomerase activity results in progressive telomere shortening during each cell division. Eventually, DNA damage responses triggered by critically short telomeres induce an irreversible cell cycle arrest termed replicative senescence. However, the cellular responses of human pluripotent stem cells to telomere uncapping remain unknown. We generated telomerase knockout human embryonic stem (ES) cells through gene targeting. Telomerase inactivation in ES cells results in progressive telomere shortening. Telomere DNA damage in ES cells and neural progenitor cells induces rapid apoptosis when telomeres are uncapped, in contrast to fibroblast cells that enter a state of replicative senescence. Significantly, telomerase inactivation limits the proliferation capacity of human ES cells without affecting their pluripotency. By targeting telomerase activity, we can functionally separate the two unique properties of human pluripotent stem cells, namely unlimited self-renewal and pluripotency. We show that the potential of ES cells to form teratomas in vivo is dictated by their telomere length. By controlling telomere length of ES cells through telomerase inactivation, we can inhibit teratoma formation and potentially improve the safety of cell therapies involving terminally differentiated cells as well as specific progenitor cells that do not require sustained cellular proliferation in vivo, and thus sustained telomerase activity. Stem Cells 2016;34:2471-2484. © 2016 AlphaMed Press.

  5. Analysis of poly(ADP-Ribose polymerases in Arabidopsis telomere biology.

    Directory of Open Access Journals (Sweden)

    Kara A Boltz

    Full Text Available Maintaining the length of the telomere tract at chromosome ends is a complex process vital to normal cell division. Telomere length is controlled through the action of telomerase as well as a cadre of telomere-associated proteins that facilitate replication of the chromosome end and protect it from eliciting a DNA damage response. In vertebrates, multiple poly(ADP-ribose polymerases (PARPs have been implicated in the regulation of telomere length, telomerase activity and chromosome end protection. Here we investigate the role of PARPs in plant telomere biology. We analyzed Arabidopsis thaliana mutants null for PARP1 and PARP2 as well as plants treated with the PARP competitive inhibitor 3-AB. Plants deficient in PARP were hypersensitive to genotoxic stress, and expression of PARP1 and PARP2 mRNA was elevated in response to MMS or zeocin treatment or by the loss of telomerase. Additionally, PARP1 mRNA was induced in parp2 mutants, and conversely, PARP2 mRNA was induced in parp1 mutants. PARP3 mRNA, by contrast, was elevated in both parp1 and parp2 mutants, but not in seedlings treated with 3-AB or zeocin. PARP mutants and 3-AB treated plants displayed robust telomerase activity, no significant changes in telomere length, and no end-to-end chromosome fusions. Although there remains a possibility that PARPs play a role in Arabidopsis telomere biology, these findings argue that the contribution is a minor one.

  6. Analysis of Poly(ADP-Ribose) Polymerases in Arabidopsis Telomere Biology

    Science.gov (United States)

    Townley, Jennifer M.; Shippen, Dorothy E.

    2014-01-01

    Maintaining the length of the telomere tract at chromosome ends is a complex process vital to normal cell division. Telomere length is controlled through the action of telomerase as well as a cadre of telomere-associated proteins that facilitate replication of the chromosome end and protect it from eliciting a DNA damage response. In vertebrates, multiple poly(ADP-ribose) polymerases (PARPs) have been implicated in the regulation of telomere length, telomerase activity and chromosome end protection. Here we investigate the role of PARPs in plant telomere biology. We analyzed Arabidopsis thaliana mutants null for PARP1 and PARP2 as well as plants treated with the PARP competitive inhibitor 3-AB. Plants deficient in PARP were hypersensitive to genotoxic stress, and expression of PARP1 and PARP2 mRNA was elevated in response to MMS or zeocin treatment or by the loss of telomerase. Additionally, PARP1 mRNA was induced in parp2 mutants, and conversely, PARP2 mRNA was induced in parp1 mutants. PARP3 mRNA, by contrast, was elevated in both parp1 and parp2 mutants, but not in seedlings treated with 3-AB or zeocin. PARP mutants and 3-AB treated plants displayed robust telomerase activity, no significant changes in telomere length, and no end-to-end chromosome fusions. Although there remains a possibility that PARPs play a role in Arabidopsis telomere biology, these findings argue that the contribution is a minor one. PMID:24551184

  7. Relationship between leukocyte telomere length and personality traits in healthy subjects.

    Science.gov (United States)

    Sadahiro, R; Suzuki, A; Enokido, M; Matsumoto, Y; Shibuya, N; Kamata, M; Goto, K; Otani, K

    2015-02-01

    It has been shown that certain personality traits are related to mortality and disease morbidity, but the biological mechanism linking them remains unclear. Telomeres are tandem repeat DNA sequences located at the ends of chromosomes, and shorter telomere length is a predictor of mortality and late-life disease morbidity. Thus, it is possible that personality traits influence telomere length. In the present study, we examined the relationship of leukocyte telomere length with personality traits in healthy subjects. The subjects were 209 unrelated healthy Japanese who were recruited from medical students at 4th-5th grade. Assessment of personality traits was performed by the Revised NEO Personality Inventory (NEO-PI-R) and the Temperament and Character Inventory (TCI). Leukocyte relative telomere length was determined by a quantitative real-time PCR method for a ratio of telomere/single copy gene. In the stepwise multiple regression analysis, shorter telomere length was related to lower scores of neuroticism (Ppersonality traits, and this association may be implicated in the relationship between personality traits and mortality. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  8. A calmodulin-like protein (LCALA) is a new Leishmania amazonensis candidate for telomere end-binding protein.

    Science.gov (United States)

    Morea, Edna G O; Viviescas, Maria Alejandra; Fernandes, Carlos A H; Matioli, Fabio F; Lira, Cristina B B; Fernandez, Maribel F; Moraes, Barbara S; da Silva, Marcelo S; Storti, Camila B; Fontes, Marcos R M; Cano, Maria Isabel N

    2017-11-01

    Leishmania spp. telomeres are composed of 5'-TTAGGG-3' repeats associated with proteins. We have previously identified LaRbp38 and LaRPA-1 as proteins that bind the G-rich telomeric strand. At that time, we had also partially characterized a protein: DNA complex, named LaGT1, but we could not identify its protein component. Using protein-DNA interaction and competition assays, we confirmed that LaGT1 is highly specific to the G-rich telomeric single-stranded DNA. Three protein bands, with LaGT1 activity, were isolated from affinity-purified protein extracts in-gel digested, and sequenced de novo using mass spectrometry analysis. In silico analysis of the digested peptide identified them as a putative calmodulin with sequences identical to the T. cruzi calmodulin. In the Leishmania genome, the calmodulin ortholog is present in three identical copies. We cloned and sequenced one of the gene copies, named it LCalA, and obtained the recombinant protein. Multiple sequence alignment and molecular modeling showed that LCalA shares homology to most eukaryotes calmodulin. In addition, we demonstrated that LCalA is nuclear, partially co-localizes with telomeres and binds in vivo the G-rich telomeric strand. Recombinant LCalA can bind specifically and with relative affinity to the G-rich telomeric single-strand and to a 3'G-overhang, and DNA binding is calcium dependent. We have described a novel candidate component of Leishmania telomeres, LCalA, a nuclear calmodulin that binds the G-rich telomeric strand with high specificity and relative affinity, in a calcium-dependent manner. LCalA is the first reported calmodulin that binds in vivo telomeric DNA. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Association of cadmium and arsenic exposure with salivary telomere length in adolescents in Terai, Nepal

    International Nuclear Information System (INIS)

    Fillman, Toki; Shimizu-Furusawa, Hana; Ng, Chris Fook Sheng; Parajuli, Rajendra Prasad; Watanabe, Chiho

    2016-01-01

    Background: Cadmium and arsenic are ubiquitous metals commonly found in the environment which can harm human health. A growing body of research shows telomere length as a potential biomarker of future disease risk. Few studies have examined the effects of metals on telomere length and none have focused on adolescents. Objectives: In this study, the impact of cadmium and arsenic on salivary telomere length was studied in adolescents in Terai, Nepal. Methods: Adolescents aged 12–16 years old (n=351)were recruited where questionnaire interviews and both saliva and urine collection took place. Telomere length was determined by quantitative polymerase chain reaction using DNA extracted from saliva. Urinary cadmium and arsenic concentration were measured by inductively coupled plasma mass spectrometry. Multivariable linear regression was used to examine associations between urinary metals and salivary telomere length. Results: The geometric means and standard deviations of cadmium and arsenic were 0.33±0.33 μg/g creatinine and 196.0±301.1 μg/g creatinine, respectively. Urinary cadmium concentration was negatively associated with salivary telomere length after adjustment for confounders (β=−0.24, 95% CI −0.42,−0.07). Arsenic showed positive associations with telomere length but did not reach statistical significance. Conclusions: This is the first study to demonstrate that cadmium may shorten adolescent telomeres, even at exposure levels that may be considered low. These results agree with prior experimental and adult epidemiological studies, and also help identify the mechanism of DNA damage by cadmium. This study expanded current evidence on the harmful effects of cadmium exposure on telomere length even to adolescents. - Highlights: • This is the first study examining metal exposure on telomere length in adolescents. • Urinary cadmium levels were similar to non-industrially polluted levels in Asia. • Urinary arsenic levels were as high as groundwater

  10. Association of cadmium and arsenic exposure with salivary telomere length in adolescents in Terai, Nepal

    Energy Technology Data Exchange (ETDEWEB)

    Fillman, Toki, E-mail: tokif@humeco.m.u-tokyo.ac.jp [Department of Human Ecology, School of International Health, Graduate School of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-Ku, Tokyo, 113-0033 (Japan); Shimizu-Furusawa, Hana, E-mail: hana-shimizu@umin.ac.jp [Department of Human Ecology, School of International Health, Graduate School of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-Ku, Tokyo, 113-0033 (Japan); Ng, Chris Fook Sheng, E-mail: chrisng-tky@umin.ac.jp [Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki (Japan); Parajuli, Rajendra Prasad, E-mail: rp.parajuli@mcgill.ca [Basu Laboratory, CINE Building, Macdonald Campus, Faculty of Agricultural and Environmental Sciences, McGill University, Montreal, Quebec (Canada); Watanabe, Chiho, E-mail: chiho@humeco.m.u-tokyo.ac.jp [Department of Human Ecology, School of International Health, Graduate School of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-Ku, Tokyo, 113-0033 (Japan)

    2016-08-15

    Background: Cadmium and arsenic are ubiquitous metals commonly found in the environment which can harm human health. A growing body of research shows telomere length as a potential biomarker of future disease risk. Few studies have examined the effects of metals on telomere length and none have focused on adolescents. Objectives: In this study, the impact of cadmium and arsenic on salivary telomere length was studied in adolescents in Terai, Nepal. Methods: Adolescents aged 12–16 years old (n=351)were recruited where questionnaire interviews and both saliva and urine collection took place. Telomere length was determined by quantitative polymerase chain reaction using DNA extracted from saliva. Urinary cadmium and arsenic concentration were measured by inductively coupled plasma mass spectrometry. Multivariable linear regression was used to examine associations between urinary metals and salivary telomere length. Results: The geometric means and standard deviations of cadmium and arsenic were 0.33±0.33 μg/g creatinine and 196.0±301.1 μg/g creatinine, respectively. Urinary cadmium concentration was negatively associated with salivary telomere length after adjustment for confounders (β=−0.24, 95% CI −0.42,−0.07). Arsenic showed positive associations with telomere length but did not reach statistical significance. Conclusions: This is the first study to demonstrate that cadmium may shorten adolescent telomeres, even at exposure levels that may be considered low. These results agree with prior experimental and adult epidemiological studies, and also help identify the mechanism of DNA damage by cadmium. This study expanded current evidence on the harmful effects of cadmium exposure on telomere length even to adolescents. - Highlights: • This is the first study examining metal exposure on telomere length in adolescents. • Urinary cadmium levels were similar to non-industrially polluted levels in Asia. • Urinary arsenic levels were as high as groundwater

  11. The Association of Telomere Length With Family Violence and Disruption

    Science.gov (United States)

    Mabile, Emily; Brett, Zoë H.; Esteves, Kyle; Jones, Edward; Shirtcliff, Elizabeth A.; Theall, Katherine P.

    2014-01-01

    BACKGROUND: To enhance the understanding of biological mechanisms connecting early adversity and negative health, we examine the association between family interpersonal violence and disruption and telomere length in youth. These specific exposures were selected because of their established links with negative health consequences across the life-course. METHODS: Children, age 5 to 15, were recruited from the greater New Orleans area, and exposure to family disruption and violence was assessed through caregiver report. Telomere length, from buccal cell DNA (buccal telomere length [bTL]), was determined by using monochrome multiplex quantitative real-time polymerase chain reaction. The association between bTL and adversity exposure was tested (n = 80). RESULTS: Cumulative exposure to interpersonal violence and family disruption was correlated with bTL. Controlling for other sociodemographic factors, bTL was significantly shorter in children with higher exposure to family violence and disruption. Witnessing family violence exerted a particularly potent impact. A significant gender interaction was found (β = −0.0086, SE = 0.0031, z test= −2.79, P = .0053) and analysis revealed the effect only in girls. CONCLUSIONS: bTL is a molecular biomarker of adversity and allostatic load that is detectable in childhood. The present results extend previous studies by demonstrating that telomeres are sensitive to adversity within the overarching family domain. These findings suggest that the family ecology may be an important target for interventions to reduce the biological impact of adversity in the lives of children. PMID:24936002

  12. The association of telomere length with family violence and disruption.

    Science.gov (United States)

    Drury, Stacy S; Mabile, Emily; Brett, Zoë H; Esteves, Kyle; Jones, Edward; Shirtcliff, Elizabeth A; Theall, Katherine P

    2014-07-01

    To enhance the understanding of biological mechanisms connecting early adversity and negative health, we examine the association between family interpersonal violence and disruption and telomere length in youth. These specific exposures were selected because of their established links with negative health consequences across the life-course. Children, age 5 to 15, were recruited from the greater New Orleans area, and exposure to family disruption and violence was assessed through caregiver report. Telomere length, from buccal cell DNA (buccal telomere length [bTL]), was determined by using monochrome multiplex quantitative real-time polymerase chain reaction. The association between bTL and adversity exposure was tested (n = 80). Cumulative exposure to interpersonal violence and family disruption was correlated with bTL. Controlling for other sociodemographic factors, bTL was significantly shorter in children with higher exposure to family violence and disruption. Witnessing family violence exerted a particularly potent impact. A significant gender interaction was found (β = -0.0086, SE = 0.0031, z test= -2.79, P = .0053) and analysis revealed the effect only in girls. bTL is a molecular biomarker of adversity and allostatic load that is detectable in childhood. The present results extend previous studies by demonstrating that telomeres are sensitive to adversity within the overarching family domain. These findings suggest that the family ecology may be an important target for interventions to reduce the biological impact of adversity in the lives of children. Copyright © 2014 by the American Academy of Pediatrics.

  13. Telomere elongation in immortal human cells without detectable telomerase activity.

    Science.gov (United States)

    Bryan, T M; Englezou, A; Gupta, J; Bacchetti, S; Reddel, R R

    1995-09-01

    Immortalization of human cells is often associated with reactivation of telomerase, a ribonucleoprotein enzyme that adds TTAGGG repeats onto telomeres and compensates for their shortening. We examined whether telomerase activation is necessary for immortalization. All normal human fibroblasts tested were negative for telomerase activity. Thirteen out of 13 DNA tumor virus-transformed cell cultures were also negative in the pre-crisis (i.e. non-immortalized) stage. Of 35 immortalized cell lines, 20 had telomerase activity as expected, but 15 had no detectable telomerase. The 15 telomerase-negative immortalized cell lines all had very long and heterogeneous telomeres of up to 50 kb. Hybrids between telomerase-negative and telomerase-positive cells senesced. Two senescent hybrids demonstrated telomerase activity, indicating that activation of telomerase is not sufficient for immortalization. Some hybrid clones subsequently recommenced proliferation and became immortalized either with or without telomerase activity. Those without telomerase activity also had very long and heterogeneous telomeres. Taken together, these data suggest that the presence of lengthened or stabilized telomeres is necessary for immortalization, and that this may be achieved either by the reactivation of telomerase or by a novel and as yet unidentified mechanism.

  14. Compromised telomere maintenance in hypomethylated Arabidopsis thaliana plants

    Czech Academy of Sciences Publication Activity Database

    Ogrocká, A.; Polanská, P.; Majerová, E.; Janeba, Zlatko; Fajkus, Jiří; Fojtová, M.

    2014-01-01

    Roč. 42, č. 5 (2014), s. 2919-2931 ISSN 0305-1048 Grant - others:GA ČR(CZ) GAP501/11/0596; GA MŠk(CZ) ED1.1.00/02.0068 Program:ED Institutional support: RVO:61388963 ; RVO:68081707 Keywords : DNA methylation * cytosine methylation * mammalian telomeres Subject RIV: CE - Biochemistry; BO - Biophysics (BFU-R) Impact factor: 9.112, year: 2014

  15. Stabilization of Telomere G-Quadruplexes Interferes with Human Herpesvirus 6A Chromosomal Integration.

    Science.gov (United States)

    Gilbert-Girard, Shella; Gravel, Annie; Artusi, Sara; Richter, Sara N; Wallaschek, Nina; Kaufer, Benedikt B; Flamand, Louis

    2017-07-15

    Human herpesviruses 6A and 6B (HHV-6A/B) can integrate their genomes into the telomeres of human chromosomes using a mechanism that remains poorly understood. To achieve a better understanding of the HHV-6A/B integration mechanism, we made use of BRACO-19, a compound that stabilizes G-quadruplex secondary structures and prevents telomere elongation by the telomerase complex. First, we analyzed the folding of telomeric sequences into G-quadruplex structures and their binding to BRACO-19 using G-quadruplex-specific antibodies and surface plasmon resonance. Circular dichroism studies indicate that BRACO-19 modifies the conformation and greatly stabilizes the G-quadruplexes formed in G-rich telomeric DNA. Subsequently we assessed the effects of BRACO-19 on the HHV-6A initial phase of infection. Our results indicate that BRACO-19 does not affect entry of HHV-6A DNA into cells. We next investigated if stabilization of G-quadruplexes by BRACO-19 affected HHV-6A's ability to integrate its genome into host chromosomes. Incubation of telomerase-expressing cells with BRACO-19, such as HeLa and MCF-7, caused a significant reduction in the HHV-6A integration frequency ( P integration frequency in U2OS cells that lack telomerase activity and elongate their telomeres through alternative lengthening mechanisms. Our data suggest that the fluidity of telomeres is important for efficient chromosomal integration of HHV-6A and that interference with telomerase activity negatively affects the generation of cellular clones containing integrated HHV-6A. IMPORTANCE HHV-6A/B can integrate their genomes into the telomeres of infected cells. Telomeres consist of repeated hexanucleotides (TTAGGG) of various lengths (up to several kilobases) and end with a single-stranded 3' extension. To avoid recognition and induce a DNA damage response, the single-stranded overhang folds back on itself and forms a telomeric loop (T-loop) or adopts a tertiary structure, referred to as a G-quadruplex. In the

  16. Zen meditation, Length of Telomeres, and the Role of Experiential Avoidance and Compassion.

    Science.gov (United States)

    Alda, Marta; Puebla-Guedea, Marta; Rodero, Baltasar; Demarzo, Marcelo; Montero-Marin, Jesus; Roca, Miquel; Garcia-Campayo, Javier

    Mindfulness refers to an awareness that emerges by intentionally focusing on the present experience in a nonjudgmental or evaluative manner. Evidence regarding its efficacy has been increasing exponentially, and recent research suggests that the practice of meditation is associated with longer leukocyte telomere length. However, the psychological mechanisms underlying this potential relationship are unknown. We examined the telomere lengths of a group of 20 Zen meditation experts and another 20 healthy matched comparison participants who had not previously meditated. We also measured multiple psychological variables related to meditation practice. Genomic DNA was extracted for telomere measurement using a Life Length proprietary program. High-throughput quantitative fluorescence in situ hybridization (HT-Q-FISH) was used to measure the telomere length distribution and the median telomere length (MTL). The meditators group had a longer MTL ( p  = 0.005) and a lower percentage of short telomeres in individual cells ( p  = 0.007) than those in the comparison group. To determine which of the psychological variables contributed more to telomere maintenance, two regression analyses were conducted. In the first model, which applied to the MTL, the following three factors were significant: age, absence of experiential avoidance, and Common Humanity subscale of the Self Compassion Scale. Similarly, in the model that examined the percentage of short telomeres, the same factors were significant: age, absence of experiential avoidance, and Common Humanity subscale of the Self Compassion Scale. Although limited by a small sample size, these results suggest that the absence of experiential avoidance of negative emotions and thoughts is integral to the connection between meditation and telomeres.

  17. The long and the short of telomeres in bone marrow recipient SCID patients.

    Science.gov (United States)

    Sarzotti-Kelsoe, Marcella; Daniell, Xiaoju G; Whitesides, John F; Buckley, Rebecca H

    2011-04-01

    Telomeres are noncoding DNA regions at the end of the chromosomes that are crucial for genome stability. Since telomere length decreases with cell division, they can be used as a signature of cell proliferation history. T-cell reconstitution in severe combined immunodeficiency (SCID) subjects, recipients of T-cell-depleted, allogeneic-related bone marrow cells, is due to the development and maturation of donor T-cell precursors in the infant's vestigial thymus and to homeostatic proliferation of mature T cells in the peripheral organs. Since T-cell function, thymic output, and T-cell clonal diversity are maintained long term in these patients, we investigated whether donor T-cell engraftment resulted in increased telomere shortening. Our study of seven SCID patients, following successful bone marrow transplantation, demonstrates that the patients' peripheral T cells did not exhibit greater than normal telomere shortening.

  18. G-quadruplex formation in telomeres enhances POT1/TPP1 protection against RPA binding

    Science.gov (United States)

    Ray, Sujay; Bandaria, Jigar N.; Qureshi, Mohammad H.; Yildiz, Ahmet; Balci, Hamza

    2014-01-01

    Human telomeres terminate with a single-stranded 3′ G overhang, which can be recognized as a DNA damage site by replication protein A (RPA). The protection of telomeres (POT1)/POT1-interacting protein 1 (TPP1) heterodimer binds specifically to single-stranded telomeric DNA (ssTEL) and protects G overhangs against RPA binding. The G overhang spontaneously folds into various G-quadruplex (GQ) conformations. It remains unclear whether GQ formation affects the ability of POT1/TPP1 to compete against RPA to access ssTEL. Using single-molecule Förster resonance energy transfer, we showed that POT1 stably loads to a minimal DNA sequence adjacent to a folded GQ. At 150 mM K+, POT1 loading unfolds the antiparallel GQ, as the parallel conformation remains folded. POT1/TPP1 loading blocks RPA’s access to both folded and unfolded telomeres by two orders of magnitude. This protection is not observed at 150 mM Na+, in which ssTEL forms only a less-stable antiparallel GQ. These results suggest that GQ formation of telomeric overhangs may contribute to suppression of DNA damage signals. PMID:24516170

  19. Cancer telomeres and white crows.

    Science.gov (United States)

    Meeker, Alan K

    2018-01-01

    This mini-review article discusses past and present prostate-focused research on telomere and telomerase biology conducted at Johns Hopkins, through the eyes of a Donald S Coffey trainee. Included are past discoveries of abnormalities in telomere biology in the context of prostate cancer and its pre-malignant precursor prostatic intraepithelial neoplasia (PIN); the finding that telomerase activity is androgen-regulated in the prostate, and the potential role of telomerase in prostate epithelial stem cells. Also reviewed are more recent results showing that in situ telomere length measurements in patient tissue specimens may have utility in risk assessment and as a prognostic biomarker. Highlighted throughout the article are some of the training and mentorship approaches employed by the late Dr. Coffey, former Director of Urologic Research at the Brady Urological Research Institute, which inspired new research ideas, team science, and discovery.

  20. Isolation of Chromatin from Dysfunctional Telomeres Reveals an Important Role for Ring1b in NHEJ-Mediated Chromosome Fusions

    Directory of Open Access Journals (Sweden)

    Cristina Bartocci

    2014-05-01

    Full Text Available When telomeres become critically short, DNA damage response factors are recruited at chromosome ends, initiating a cellular response to DNA damage. We performed proteomic isolation of chromatin fragments (PICh in order to define changes in chromatin composition that occur upon onset of acute telomere dysfunction triggered by depletion of the telomere-associated factor TRF2. This unbiased purification of telomere-associated proteins in functional or dysfunctional conditions revealed the dynamic changes in chromatin composition that take place at telomeres upon DNA damage induction. On the basis of our results, we describe a critical role for the polycomb group protein Ring1b in nonhomologous end-joining (NHEJ-mediated end-to-end chromosome fusions. We show that cells with reduced levels of Ring1b have a reduced ability to repair uncapped telomeric chromatin. Our data represent an unbiased isolation of chromatin undergoing DNA damage and are a valuable resource to map the changes in chromatin composition in response to DNA damage activation.

  1. Development of software and modification of Q-FISH protocol for estimation of individual telomere length in immunopathology.

    Science.gov (United States)

    Barkovskaya, M Sh; Bogomolov, A G; Knauer, N Yu; Rubtsov, N B; Kozlov, V A

    2017-04-01

    Telomere length is an important indicator of proliferative cell history and potential. Decreasing telomere length in the cells of an immune system can indicate immune aging in immune-mediated and chronic inflammatory diseases. Quantitative fluorescent in situ hybridization (Q-FISH) of a labeled (C 3 TA[Formula: see text] peptide nucleic acid probe onto fixed metaphase cells followed by digital image microscopy allows the evaluation of telomere length in the arms of individual chromosomes. Computer-assisted analysis of microscopic images can provide quantitative information on the number of telomeric repeats in individual telomeres. We developed new software to estimate telomere length. The MeTeLen software contains new options that can be used to solve some Q-FISH and microscopy problems, including correction of irregular light effects and elimination of background fluorescence. The identification and description of chromosomes and chromosome regions are essential to the Q-FISH technique. To improve the quality of cytogenetic analysis after Q-FISH, we optimized the temperature and time of DNA-denaturation to get better DAPI-banding of metaphase chromosomes. MeTeLen was tested by comparing telomere length estimations for sister chromatids, background fluorescence estimations, and correction of nonuniform light effects. The application of the developed software for analysis of telomere length in patients with rheumatoid arthritis was demonstrated.

  2. Reliability and short-term intra-individual variability of telomere length measurement using monochrome multiplexing quantitative PCR.

    Directory of Open Access Journals (Sweden)

    Sangmi Kim

    Full Text Available Studies examining the association between telomere length and cancer risk have often relied on measurement of telomere length from a single blood draw using a real-time PCR technique. We examined the reliability of telomere length measurement using sequential samples collected over a 9-month period.Relative telomere length in peripheral blood was estimated using a single tube monochrome multiplex quantitative PCR assay in blood DNA samples from 27 non-pregnant adult women (aged 35 to 74 years collected in 7 visits over a 9-month period. A linear mixed model was used to estimate the components of variance for telomere length measurements attributed to variation among women and variation between time points within women. Mean telomere length measurement at any single visit was not significantly different from the average of 7 visits. Plates had a significant systematic influence on telomere length measurements, although measurements between different plates were highly correlated. After controlling for plate effects, 64% of the remaining variance was estimated to be accounted for by variance due to subject. Variance explained by time of visit within a subject was minor, contributing 5% of the remaining variance.Our data demonstrate good short-term reliability of telomere length measurement using blood from a single draw. However, the existence of technical variability, particularly plate effects, reinforces the need for technical replicates and balancing of case and control samples across plates.

  3. Telomere 1 (POT1) gene expression and its association with telomerase activity in colorectal tumor samples with different pathological features.

    Science.gov (United States)

    Izgi, Ahu; Gunal, Armagan; Yalcin, Serap; Gunduz, Ufuk

    2014-09-01

    The ends of chromosoms, telomeres are bound with a number of proteins which protect and stabilize telomeres against degredation, end to end fusion and aberrant recombinations. Telomeric DNA is bound of two groups of proteins, which are double-stranded telomeric DNA bindings proteins, and single stranded telomeric binding proteins. Among telomere binding proteins, protections of telomere 1 protein is a single stranded telomere binding proteins and suggested to be a significant player for telomere elongation and has an association with an enzyme called as telomerase which is an intrinsic reverse transcriptase. Telomerase synthesizes hexameric telomeric repeats onto the chromosomes thereby compansating telomere loss in immortal cells, such as tumor cells, whereas telomeres are shorthened with each division in normal cells. PCR-based TRAP (telomeric repeat amplification protocol) assay is a very sensitive assay for the detection of enzymatic activity of telomerase even if a few numbers of cancerous cells are available. The association between telomerase activity and hPOT1 expression in colorectal cancer is still unclear. Protein extraction was performed from specimens of matched normal and colorectal cancer specimens. Protein concentrations were determined by Bradford assay. Optimized protein concentrations were used for TRAP Assay. TRAP products were seperated by vertical gel electrophoresis on 12.5% polyacrylamide gels and visualized by silver staining. Gene expression of hPOT1 was determined by qPCR analysis. The results demonstrated that all tumor tissues were telomerase positive whereas all corresponding normal tissue was telomerase negative. Among clinicopathological findings, telomerase activity was found to be associated with stage, histology, localization, distant metastasis and lymph node metastasis of tumor in the current study. Although all of the clinicopathological findings differed in the expression of hPOT1 compared to normal tissues, they did not

  4. Telomere length in normal and neoplastic canine tissues.

    Science.gov (United States)

    Cadile, Casey D; Kitchell, Barbara E; Newman, Rebecca G; Biller, Barbara J; Hetler, Elizabeth R

    2007-12-01

    To determine the mean telomere restriction fragment (TRF) length in normal and neoplastic canine tissues. 57 solid-tissue tumor specimens collected from client-owned dogs, 40 samples of normal tissue collected from 12 clinically normal dogs, and blood samples collected from 4 healthy blood donor dogs. Tumor specimens were collected from client-owned dogs during diagnostic or therapeutic procedures at the University of Illinois Veterinary Medical Teaching Hospital, whereas 40 normal tissue samples were collected from 12 control dogs. Telomere restriction fragment length was determined by use of an assay kit. A histologic diagnosis was provided for each tumor by personnel at the Veterinary Diagnostic Laboratory at the University of Illinois. Mean of the mean TRF length for 44 normal samples was 19.0 kilobases (kb; range, 15.4 to 21.4 kb), and the mean of the mean TRF length for 57 malignant tumors was 19.0 kb (range, 12.9 to 23.5 kb). Although the mean of the mean TRF length for tumors and normal tissues was identical, tumor samples had more variability in TRF length. Telomerase, which represents the main mechanism by which cancer cells achieve immortality, is an attractive therapeutic target. The ability to measure telomere length is crucial to monitoring the efficacy of telomerase inhibition. In contrast to many other mammalian species, the length of canine telomeres and the rate of telomeric DNA loss are similar to those reported in humans, making dogs a compelling choice for use in the study of human anti-telomerase strategies.

  5. DNA methylation perturbations in genes involved in polyunsaturated Fatty Acid biosynthesis associated with depression and suicide risk.

    Science.gov (United States)

    Haghighi, Fatemeh; Galfalvy, Hanga; Chen, Sean; Huang, Yung-Yu; Cooper, Thomas B; Burke, Ainsley K; Oquendo, Maria A; Mann, J John; Sublette, M Elizabeth

    2015-01-01

    Polyunsaturated fatty acid (PUFA) status has been associated with neuropsychiatric disorders, including depression and risk of suicide. Long-chain PUFAs (LC-PUFAs) are obtained in the diet or produced by sequential desaturation and elongation of shorter-chain precursor fatty acids linoleic acid (LA, 18:2n-6) and α-linolenic acid (ALA, 18:3n-3). We compared DNA methylation patterns in genes involved in LC-PUFA biosynthesis in major depressive disorder (MDD) with (n = 22) and without (n = 39) history of suicide attempt, and age- and sex-matched healthy volunteers (n = 59). Plasma levels of selected PUFAs along the LC-PUFA biosynthesis pathway were determined by transesterification and gas chromatography. CpG methylation levels for the main human LC-PUFA biosynthetic genes, fatty acid desaturases 1 (Fads1) and 2 (Fads2), and elongation of very long-chain fatty acids protein 5 (Elovl5), were assayed by bisulfite pyrosequencing. Associations between PUFA levels and diagnosis or suicide attempt status did not survive correction for multiple testing. However, MDD diagnosis and suicide attempts were significantly associated with DNA methylation in Elovl5 gene regulatory regions. Also the relative roles of PUFA levels and DNA methylation with respect to diagnostic and suicide attempt status were determined by least absolute shrinkage and selection operator logistic regression analyses. We found that PUFA associations with suicide attempt status were explained by effects of Elovl5 DNA methylation within the regulatory regions. The observed link between plasma PUFA levels, DNA methylation, and suicide risk may have implications for modulation of disease-associated epigenetic marks by nutritional intervention.

  6. DNA methylation perturbations in genes involved in polyunsaturated fatty acid biosynthesis associated with depression and suicide risk

    Directory of Open Access Journals (Sweden)

    Fatemeh eHaghighi

    2015-04-01

    Full Text Available Polyunsaturated fatty acid (PUFA status has been associated with neuropsychiatric disorders, including depression and risk of suicide. Long-chain PUFAs (LC-PUFAs are obtained in the diet or produced by sequential desaturation and elongation of shorter-chain precursor fatty acids linoleic acid (LA, 18:2n-6 and α-linolenic acid (ALA, 18:3n-3. We compared DNA methylation patterns in genes involved in LC-PUFA biosynthesis in major depressive disorder (MDD with (n=22 and without (n=39 history of suicide attempt, and age- and sex-matched healthy volunteers (n=59. Plasma levels of selected PUFAs along the LC-PUFA biosynthesis pathway were determined by transesterification and gas chromatography. CpG methylation levels for the main human LC-PUFA biosynthetic genes, fatty acid desaturases 1 (Fads1 and 2 (Fads2, and elongation of very long chain fatty acids protein 5 (Elovl5, were assayed by bisulfite pyrosequencing. Associations between PUFA levels and diagnosis or suicide attempt status did not survive correction for multiple testing. However, MDD diagnosis and suicide attempts were significantly associated with DNA methylation in Elovl5 gene regulatory regions. Also the relative roles of PUFA levels and DNA methylation with respect to diagnostic and suicide attempt status were determined by least absolute shrinkage and selection operator (LASSO logistic regression analyses. We found that PUFA associations with suicide attempt status were explained by effects of Elovl5 DNA methylation within the regulatory regions. The observed link between plasma PUFA levels, DNA methylation, and suicide risk may have implications for modulation of disease-associated epigenetic marks by nutritional intervention.

  7. Binding of Multiple Rap1 Proteins Stimulates Chromosome Breakage Induction during DNA Replication.

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    Greicy H Goto

    2015-08-01

    Full Text Available Telomeres, the ends of linear eukaryotic chromosomes, have a specialized chromatin structure that provides a stable chromosomal terminus. In budding yeast Rap1 protein binds to telomeric TG repeat and negatively regulates telomere length. Here we show that binding of multiple Rap1 proteins stimulates DNA double-stranded break (DSB induction at both telomeric and non-telomeric regions. Consistent with the role of DSB induction, Rap1 stimulates nearby recombination events in a dosage-dependent manner. Rap1 recruits Rif1 and Rif2 to telomeres, but neither Rif1 nor Rif2 is required for DSB induction. Rap1-mediated DSB induction involves replication fork progression but inactivation of checkpoint kinase Mec1 does not affect DSB induction. Rap1 tethering shortens artificially elongated telomeres in parallel with telomerase inhibition, and this telomere shortening does not require homologous recombination. These results suggest that Rap1 contributes to telomere homeostasis by promoting chromosome breakage.

  8. Phenolic promiscuity in the cell nucleus--epigallocatechingallate (EGCG) and theaflavin-3,3'-digallate from green and black tea bind to model cell nuclear structures including histone proteins, double stranded DNA and telomeric quadruplex DNA.

    Science.gov (United States)

    Mikutis, Gediminas; Karaköse, Hande; Jaiswal, Rakesh; LeGresley, Adam; Islam, Tuhidul; Fernandez-Lahore, Marcelo; Kuhnert, Nikolai

    2013-02-01

    Flavanols from tea have been reported to accumulate in the cell nucleus in considerable concentrations. The nature of this phenomenon, which could provide novel approaches in understanding the well-known beneficial health effects of tea phenols, is investigated in this contribution. The interaction between epigallocatechin gallate (EGCG) from green tea and a selection of theaflavins from black tea with selected cell nuclear structures such as model histone proteins, double stranded DNA and quadruplex DNA was investigated using mass spectrometry, Circular Dichroism spectroscopy and fluorescent assays. The selected polyphenols were shown to display affinity to all of the selected cell nuclear structures, thereby demonstrating a degree of unexpected molecular promiscuity. Most interestingly theaflavin-digallate was shown to display the highest affinity to quadruplex DNA reported for any naturally occurring molecule reported so far. This finding has immediate implications in rationalising the chemopreventive effect of the tea beverage against cancer and possibly the role of tea phenolics as "life span essentials".

  9. Dual Recognition of Human Telomeric G-quadruplex by Neomycin-anthraquinone Conjugate

    Science.gov (United States)

    Ranjan, Nihar; Davis, Erik; Xue, Liang

    2013-01-01

    The authors report the recognition of a G-quadruplex formed by four repeat human telomeric DNA with aminosugar intercalator conjugates. The recognition of G-quadruplex through dual binding mode ligands significantly increased the affinity of ligands for G-quadruplex. One such example is a neomycin-anthraquinone 2 which exhibited nanomolar affinity for the quadruplex, and the affinity of 2 is nearly 1000 fold higher for human telomeric G-quadruplex DNA than its constituent units, neomycin and anthraquinone. PMID:23698792

  10. Large-scale symmetry-adapted perturbation theory computations via density fitting and Laplace transformation techniques: investigating the fundamental forces of DNA-intercalator interactions.

    Science.gov (United States)

    Hohenstein, Edward G; Parrish, Robert M; Sherrill, C David; Turney, Justin M; Schaefer, Henry F

    2011-11-07

    Symmetry-adapted perturbation theory (SAPT) provides a means of probing the fundamental nature of intermolecular interactions. Low-orders of SAPT (here, SAPT0) are especially attractive since they provide qualitative (sometimes quantitative) results while remaining tractable for large systems. The application of density fitting and Laplace transformation techniques to SAPT0 can significantly reduce the expense associated with these computations and make even larger systems accessible. We present new factorizations of the SAPT0 equations with density-fitted two-electron integrals and the first application of Laplace transformations of energy denominators to SAPT. The improved scalability of the DF-SAPT0 implementation allows it to be applied to systems with more than 200 atoms and 2800 basis functions. The Laplace-transformed energy denominators are compared to analogous partial Cholesky decompositions of the energy denominator tensor. Application of our new DF-SAPT0 program to the intercalation of DNA by proflavine has allowed us to determine the nature of the proflavine-DNA interaction. Overall, the proflavine-DNA interaction contains important contributions from both electrostatics and dispersion. The energetics of the intercalator interaction are are dominated by the stacking interactions (two-thirds of the total), but contain important contributions from the intercalator-backbone interactions. It is hypothesized that the geometry of the complex will be determined by the interactions of the intercalator with the backbone, because by shifting toward one side of the backbone, the intercalator can form two long hydrogen-bonding type interactions. The long-range interactions between the intercalator and the next-nearest base pairs appear to be negligible, justifying the use of truncated DNA models in computational studies of intercalation interaction energies.

  11. If the cap fits, wear it: an overview of telomeric structures over evolution.

    Science.gov (United States)

    Fulcher, Nick; Derboven, Elisa; Valuchova, Sona; Riha, Karel

    2014-03-01

    Genome organization into linear chromosomes likely represents an important evolutionary innovation that has permitted the development of the sexual life cycle; this process has consequently advanced nuclear expansion and increased complexity of eukaryotic genomes. Chromosome linearity, however, poses a major challenge to the internal cellular machinery. The need to efficiently recognize and repair DNA double-strand breaks that occur as a consequence of DNA damage presents a constant threat to native chromosome ends known as telomeres. In this review, we present a comparative survey of various solutions to the end protection problem, maintaining an emphasis on DNA structure. This begins with telomeric structures derived from a subset of prokaryotes, mitochondria, and viruses, and will progress into the typical telomere structure exhibited by higher organisms containing TTAGG-like tandem sequences. We next examine non-canonical telomeres from Drosophila melanogaster, which comprise arrays of retrotransposons. Finally, we discuss telomeric structures in evolution and possible switches between canonical and non-canonical solutions to chromosome end protection.

  12. Telomere Maintenance Mechanisms in Cancer

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    Tiago Bordeira Gaspar

    2018-05-01

    Full Text Available Tumour cells can adopt telomere maintenance mechanisms (TMMs to avoid telomere shortening, an inevitable process due to successive cell divisions. In most tumour cells, telomere length (TL is maintained by reactivation of telomerase, while a small part acquires immortality through the telomerase-independent alternative lengthening of telomeres (ALT mechanism. In the last years, a great amount of data was generated, and different TMMs were reported and explained in detail, benefiting from genome-scale studies of major importance. In this review, we address seven different TMMs in tumour cells: mutations of the TERT promoter (TERTp, amplification of the genes TERT and TERC, polymorphic variants of the TERT gene and of its promoter, rearrangements of the TERT gene, epigenetic changes, ALT, and non-defined TMM (NDTMM. We gathered information from over fifty thousand patients reported in 288 papers in the last years. This wide data collection enabled us to portray, by organ/system and histotypes, the prevalence of TERTp mutations, TERT and TERC amplifications, and ALT in human tumours. Based on this information, we discuss the putative future clinical impact of the aforementioned mechanisms on the malignant transformation process in different setups, and provide insights for screening, prognosis, and patient management stratification.

  13. [Telomere length and phylogenetic relationship of Baikal and Siberian planarians (Turbellaria, Tricladida)].

    Science.gov (United States)

    Koroleva, A G; Evtushenko, E V; Timoshkin, O A; Vershinin, A V; Kiril'chik, S V

    2013-01-01

    Dynamics of the telomeric DNA (tDNA) and the phylogeny of the Baikal and Siberian planarians have been studied based on the analysis of the 18S rDNA and beta-actin gene fragments. A relationship between tDNA and the planarians size has been demonstrated. Giant planarians with a minor exception have longer tDNA than little planarians. Phylogenetic affinity between the species that have the stretched tracks of tDNA, big size and similar habitats may indicate possible role of tDNA in the development of the indefinite regenerative capacity of planarians.

  14. Endogenous and ectopic expression of telomere regulating genes in chicken embryonic fibroblasts

    International Nuclear Information System (INIS)

    Michailidis, Georgios; Saretzki, Gabriele; Hall, Judith

    2005-01-01

    In this study, we compared the endogenous expression of genes encoding telomere regulating proteins in cultured chicken embryonic fibroblasts (CEFs) and 10-day-old chicken embryos. CEFs maintained in vitro senesced and senescence was accompanied by reduced telomere length, telomerase activity, and expression of the chicken (c) TRF1 gene. There was no change in TRF2 gene expression although the major TRF2 transcript identified in 10-day-old chicken embryos encoded a truncated TRF2 protein (TRF2'), containing an N-terminal dimerisation domain but lacking a myb-related DNA binding domain and nuclear localisation signal. Senescence of the CEFs in vitro was associated with the loss of the TRF2' transcript, indicative of a novel function for the encoded protein. Senescence was also coupled with decreased expression of RAD51, but increased RAD52 expression. These data support that RAD51 independent recombination mechanisms do not function in vitro to maintain chicken telomeres. To attempt to rescue the CEFs from replicative senescence, we stably transfected passage 3 CEFs with the human telomerase reverse transcriptase (hTERT) catalytic subunit. While hTERT expression was detected in the stable transfectants neither telomerase activity nor the stabilisation of telomere length was observed, and the transfectant cells senesced at the same passage number as the untransfected cells. These data indicate that the human TERT is incompatible with the avian telomere maintenance apparatus and suggest the functioning of a species specific telomere system in the avian

  15. Accelerated telomere shortening: Tracking the lasting impact of early institutional care at the cellular level.

    Science.gov (United States)

    Humphreys, Kathryn L; Esteves, Kyle; Zeanah, Charles H; Fox, Nathan A; Nelson, Charles A; Drury, Stacy S

    2016-12-30

    Studies examining the association between early adversity and longitudinal changes in telomere length within the same individual are rare, yet are likely to provide novel insight into the subsequent lasting effects of negative early experiences. We sought to examine the association between institutional care history and telomere shortening longitudinally across middle childhood and into adolescence. Buccal DNA was collected 2-4 times, between the ages of 6 and 15 years, in 79 children enrolled in the Bucharest Early Intervention Project (BEIP), a longitudinal study exploring the impact of early institutional rearing on child health and development. Children with a history of early institutional care (n=50) demonstrated significantly greater telomere shortening across middle childhood and adolescence compared to never institutionalized children (n=29). Among children with a history of institutional care, randomization to high quality foster care was not associated with differential telomere attrition across development. Cross-sectional analysis of children randomized to the care as usual group indicated shorter telomere length was associated with greater percent of the child's life spent in institutional care up to age 8. These results suggest that early adverse care from severe psychosocial deprivation may be embedded at the molecular genetic level through accelerated telomere shortening. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  16. Measuring telomere length for the early detection of precursor lesions of esophageal squamous cell carcinoma

    International Nuclear Information System (INIS)

    Lin, Shih-Wen; Wang, Guo-Qing; Wei, Wen-Qiang; Lu, Ning; Taylor, Philip R; Qiao, You-Lin; Dawsey, Sanford M; Abnet, Christian C; Freedman, Neal D; Murphy, Gwen; Risques, Rosana; Prunkard, Donna; Rabinovitch, Peter; Pan, Qin-Jing; Roth, Mark J

    2013-01-01

    Esophageal cancer is the sixth leading cause of cancer death worldwide; current early detection screening tests are inadequate. Esophageal balloon cytology successfully retrieves exfoliated and scraped superficial esophageal epithelial cells, but cytologic reading of these cells has poor sensitivity and specificity for detecting esophageal squamous dysplasia (ESD), the precursor lesion of esophageal squamous cell carcinoma (ESCC). Measuring telomere length, a marker for chromosomal instability, may improve the utility of balloon cytology for detecting ESD and early ESCC. We examined balloon cytology specimens from 89 asymptomatic cases of ESD (37 low-grade and 52 high-grade) and 92 age- and sex-matched normal controls from an esophageal cancer early detection screening study. All subjects also underwent endoscopy and biopsy, and ESD was diagnosed histopathologically. DNA was extracted from the balloon cytology cells, and telomere length was measured by quantitative PCR. A receiver operating characteristic (ROC) curve was plotted for telomere length as a diagnostic marker for high-grade dysplasia. Telomere lengths were comparable among the low- and high-grade dysplasia cases and controls, with means of 0.96, 0.96, and 0.92, respectively. The area under the ROC curve was 0.55 for telomere length as a diagnostic marker for high-grade dysplasia. Further adjustment for subject characteristics, including sex, age, smoking, drinking, hypertension, and body mass index did not improve the use of telomere length as a marker for ESD. Telomere length of esophageal balloon cytology cells was not associated with ESCC precursor lesions. Therefore, telomere length shows little promise as an early detection marker for ESCC in esophageal balloon samples

  17. Telomere length in Chernobyl accident recovery workers in the late period after the disaster.

    Science.gov (United States)

    Reste, Jelena; Zvigule, Gunda; Zvagule, Tija; Kurjane, Natalja; Eglite, Maija; Gabruseva, Natalija; Berzina, Dace; Plonis, Juris; Miklasevics, Edvins

    2014-11-01

    The outcome of the Chernobyl nuclear power plant (CNPP) accident was that a huge number of people were exposed to ionizing radiation. Previous studies of CNPP clean-up workers from Latvia revealed a high occurrence of age-associated degenerative diseases and cancer in young adults, as well as a high mortality as a result of cardiovascular disorders at age 45-54 years. DNA tandem repeats that cap chromosome ends, known as telomeres, are sensitive to oxidative damage and exposure to ionizing radiation. Telomeres are important in aging processes and carcinogenesis. The aim of this study was to investigate the long-term effect of protracted ionizing radiation exposure on telomere length in CNPP clean-up workers. Relative telomere length (RTL) was measured in peripheral blood leukocytes of 595 CNPP clean-up workers and 236 gender- and age-matched controls using real-time quantitative polymerase chain reaction (q-PCR). Close attention was paid to participation year and tasks performed during the worker's stay in Chernobyl, health status, and RTL differences between subgroups. Telomere shortening was not found in CNPP clean-up workers; on the contrary, their RTL was slightly greater than in controls (P = 0.001). Longer telomeres were found in people who worked during 1986, in those undertaking 'dirty' tasks (digging and deactivation), and in people with cancer. Shorter telomeres appeared frequently in those with cataract, osteoporosis, atherosclerosis, or coronary heart disease. We conclude that the longer telomeres revealed in people more heavily exposed to ionizing radiation probably indicate activation of telomerase as a chromosome healing mechanism following damage, and reflect defects in telomerase regulation that could potentiate carcinogenesis. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  18. Marital disruption is associated with shorter salivary telomere length in a probability sample of older adults.

    Science.gov (United States)

    Whisman, Mark A; Robustelli, Briana L; Sbarra, David A

    2016-05-01

    Marital disruption (i.e., marital separation, divorce) is associated with a wide range of poor mental and physical health outcomes, including increased risk for all-cause mortality. One biological intermediary that may help explain the association between marital disruption and poor health is accelerated cellular aging. This study examines the association between marital disruption and salivary telomere length in a United States probability sample of adults ≥50 years of age. Participants were 3526 individuals who participated in the 2008 wave of the Health and Retirement Study. Telomere length assays were performed using quantitative real-time polymerase chain reaction (qPCR) on DNA extracted from saliva samples. Health and lifestyle factors, traumatic and stressful life events, and neuroticism were assessed via self-report. Linear regression analyses were conducted to examine the associations between predictor variables and salivary telomere length. Based on their marital status data in the 2006 wave, people who were separated or divorced had shorter salivary telomeres than people who were continuously married or had never been married, and the association between marital disruption and salivary telomere length was not moderated by gender or neuroticism. Furthermore, the association between marital disruption and salivary telomere length remained statistically significant after adjusting for demographic and socioeconomic variables, neuroticism, cigarette use, body mass, traumatic life events, and other stressful life events. Additionally, results revealed that currently married adults with a history of divorce evidenced shorter salivary telomeres than people who were continuously married or never married. Accelerated cellular aging, as indexed by telomere shortening, may be one pathway through which marital disruption is associated with morbidity and mortality. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Telomere length in Chernobyl accident recovery workers in the late period after the disaster

    International Nuclear Information System (INIS)

    Reste, Jelena; Zvagule, Tija; Kurjane, Natalja; Eglite, Maija; Zvigule, Gunda; Berzina, Dace; Plonis, Juris; Miklasevics, Edvins; Gabruseva, Natalija

    2014-01-01

    The outcome of the Chernobyl nuclear power plant (CNPP) accident was that a huge number of people were exposed to ionizing radiation. Previous studies of CNPP clean-up workers from Latvia revealed a high occurrence of age-associated degenerative diseases and cancer in young adults, as well as a high mortality as a result of cardiovascular disorders at age 45–54 years. DNA tandem repeats that cap chromosome ends, known as telomeres, are sensitive to oxidative damage and exposure to ionizing radiation. Telomeres are important in aging processes and carcinogenesis. The aim of this study was to investigate the long-term effect of protracted ionizing radiation exposure on telomere length in CNPP clean-up workers. Relative telomere length (RTL) was measured in peripheral blood leukocytes of 595 CNPP clean-up workers and 236 gender- and age-matched controls using real-time quantitative polymerase chain reaction (q-PCR). Close attention was paid to participation year and tasks performed during the worker's stay in Chernobyl, health status, and RTL differences between subgroups. Telomere shortening was not found in CNPP clean-up workers; on the contrary, their RTL was slightly greater than in controls (P = 0.001). Longer telomeres were found in people who worked during 1986, in those undertaking 'dirty' tasks (digging and deactivation), and in people with cancer. Shorter telomeres appeared frequently in those with cataract, osteoporosis, atherosclerosis, or coronary heart disease. We conclude that the longer telomeres revealed in people more heavily exposed to ionizing radiation probably indicate activation of telomerase as a chromosome healing mechanism following damage, and reflect defects in telomerase regulation that could potentiate carcinogenesis. (author)

  20. Telomere biology and telomerase mutations in cirrhotic patients with hepatocellular carcinoma.

    Directory of Open Access Journals (Sweden)

    Flávia S Donaires

    Full Text Available Telomeres are repetitive DNA sequences at linear chromosome termini, protecting chromosomes against end-to-end fusion and damage, providing chromosomal stability. Telomeres shorten with mitotic cellular division, but are maintained in cells with high proliferative capacity by telomerase. Loss-of-function mutations in telomere-maintenance genes are genetic risk factors for cirrhosis development in humans and murine models. Telomerase deficiency provokes accelerated telomere shortening and dysfunction, facilitating genomic instability and oncogenesis. Here we examined whether telomerase mutations and telomere shortening were associated with hepatocellular carcinoma (HCC secondary to cirrhosis. Telomere length of peripheral blood leukocytes was measured by Southern blot and qPCR in 120 patients with HCC associated with cirrhosis and 261 healthy subjects. HCC patients were screened for telomerase gene variants (in TERT and TERC by Sanger sequencing. Age-adjusted telomere length was comparable between HCC patients and healthy subjects by both Southern blot and qPCR. Four non-synonymous TERT heterozygous variants were identified in four unrelated patients, resulting in a significantly higher mutation carrier frequency (3.3% in patients as compared to controls (p = 0.02. Three of the four variants (T726M, A1062T, and V1090M were previously observed in patients with other telomere diseases (severe aplastic anemia, acute myeloid leukemia, and cirrhosis. A novel TERT variant, A243V, was identified in a 65-year-old male with advanced HCC and cirrhosis secondary to chronic hepatitis C virus (HCV and alcohol ingestion, but direct assay measurements in vitro did not detect modulation of telomerase enzymatic activity or processivity. In summary, constitutional variants resulting in amino acid changes in the telomerase reverse transcriptase were found in a small proportion of patients with cirrhosis-associated HCC.

  1. Development and characterization of polyclonal antibodies against the linker region of the telomere-binding protein TRF2

    Directory of Open Access Journals (Sweden)

    Nadya V. Ilicheva

    2018-03-01

    Full Text Available Background: TRF2 (telomeric repeat binding factor 2 is an essential component of the telomere-binding protein complex shelterin. TRF2 induces the formation of a special structure of telomeric DNA and counteracts activation of DNA damage-response pathways telomeres. TRF2 has a poorly characterized linker region (udTRF2 between its homodimerization and DNA-binding domains. Some lines of evidence have shown that this region could be involved in TRF2 interaction with nuclear lamina. Results: In this study, the fragment of the TERF2 gene encoding udTRF2 domain of telomere-binding protein TRF2 was produced by PCR and cloned into the pET32a vector. The resulting plasmid pET32a-udTRF2 was used for the expression of the recombinant udTRF2 in E. coli RosettaBlue (DE3. The protein was isolated and purified using ammonium sulfate precipitation followed by ion-exchange chromatography. The purified recombinant protein udTRF2 was injected into guinea pigs to generate polyclonal antibodies. The ability of anti-udTRF2 antibodies to bind endogenous TRF2 in human skin fibroblasts was tested by western blotting and immunofluorescent staining. Conclusions: In this study, the recombinant protein udTRF2 and antibodies to it were generated. Both protein and antibodies will provide a useful tool for investigation of the functions of the udTRF2 domain and its role in the interaction between TRF2 and nuclear lamina. Keywords: Chromosomes, Molecular cloning, Nuclear lamina, Nucleoprotein complexes, Polyclonal antibodies, Recombinant polypeptide, Shelterin, Telomere-binding protein TRF2, Telomeres, Telomeric DNA, TTAGGG repeats

  2. Thermodynamic fingerprints of ligand binding to human telomeric G-quadruplexes

    OpenAIRE

    Bon?ina, Matja?; Podlipnik, ?rtomir; Piantanida, Ivo; Eilmes, Julita; Teulade-Fichou, Marie-Paule; Vesnaver, Gorazd; Lah, Jurij

    2015-01-01

    Thermodynamic studies of ligand binding to human telomere (ht) DNA quadruplexes, as a rule, neglect the involvement of various ht-DNA conformations in the binding process. Therefore, the thermodynamic driving forces and the mechanisms of ht-DNA G-quadruplex-ligand recognition remain poorly understood. In this work we characterize thermodynamically and structurally binding of netropsin (Net), dibenzotetraaza[14]annulene derivatives (DP77, DP78), cationic porphyrin (TMPyP4) and two bisquinolini...

  3. Do Telomeres Adapt to Physiological Stress? Exploring the Effect of Exercise on Telomere Length and Telomere-Related Proteins

    Directory of Open Access Journals (Sweden)

    Andrew T. Ludlow

    2013-01-01

    Full Text Available Aging is associated with a tissue degeneration phenotype marked by a loss of tissue regenerative capacity. Regenerative capacity is dictated by environmental and genetic factors that govern the balance between damage and repair. The age-associated changes in the ability of tissues to replace lost or damaged cells is partly the cause of many age-related diseases such as Alzheimer's disease, cardiovascular disease, type II diabetes, and sarcopenia. A well-established marker of the aging process is the length of the protective cap at the ends of chromosomes, called telomeres. Telomeres shorten with each cell division and with increasing chronological age and short telomeres have been associated with a range of age-related diseases. Several studies have shown that chronic exposure to exercise (i.e., exercise training is associated with telomere length maintenance; however, recent evidence points out several controversial issues concerning tissue-specific telomere length responses. The goals of the review are to familiarize the reader with the current telomere dogma, review the literature exploring the interactions of exercise with telomere phenotypes, discuss the mechanistic research relating telomere dynamics to exercise stimuli, and finally propose future directions for work related to telomeres and physiological stress.

  4. RPA prevents G-rich structure formation at lagging-strand telomeres to allow maintenance of chromosome ends.

    Science.gov (United States)

    Audry, Julien; Maestroni, Laetitia; Delagoutte, Emmanuelle; Gauthier, Tiphaine; Nakamura, Toru M; Gachet, Yannick; Saintomé, Carole; Géli, Vincent; Coulon, Stéphane

    2015-07-14

    Replication protein A (RPA) is a highly conserved heterotrimeric single-stranded DNA-binding protein involved in DNA replication, recombination, and repair. In fission yeast, the Rpa1-D223Y mutation provokes telomere shortening. Here, we show that this mutation impairs lagging-strand telomere replication and leads to the accumulation of secondary structures and recruitment of the homologous recombination factor Rad52. The presence of these secondary DNA structures correlates with reduced association of shelterin subunits Pot1 and Ccq1 at telomeres. Strikingly, heterologous expression of the budding yeast Pif1 known to efficiently unwind G-quadruplex rescues all the telomeric defects of the D223Y cells. Furthermore, in vitro data show that the identical D to Y mutation in human RPA specifically affects its ability to bind G-quadruplex. We propose that RPA prevents the formation of G-quadruplex structures at lagging-strand telomeres to promote shelterin association and facilitate telomerase action at telomeres. © 2015 The Authors.

  5. Breaking an epigenetic chromatin switch: curious features of hysteresis in Saccharomyces cerevisiae telomeric silencing.

    Directory of Open Access Journals (Sweden)

    Vijayalakshmi H Nagaraj

    Full Text Available In addition to gene network switches, local epigenetic modifications to DNA and histones play an important role in all-or-none cellular decision-making. Here, we study the dynamical design of a well-characterized epigenetic chromatin switch: the yeast SIR system, in order to understand the origin of the stability of epigenetic states. We study hysteresis in this system by perturbing it with a histone deacetylase inhibitor. We find that SIR silencing has many characteristics of a non-linear bistable system, as observed in conventional genetic switches, which are based on activities of a few promoters affecting each other through the abundance of their gene products. Quite remarkably, our experiments in yeast telomeric silencing show a very distinctive pattern when it comes to the transition from bistability to monostability. In particular, the loss of the stable silenced state, upon increasing the inhibitor concentration, does not seem to show the expected saddle node behavior, instead looking like a supercritical pitchfork bifurcation. In other words, the 'off' state merges with the 'on' state at a threshold concentration leading to a single state, as opposed to the two states remaining distinct up to the threshold and exhibiting a discontinuous jump from the 'off' to the 'on' state. We argue that this is an inevitable consequence of silenced and active regions coexisting with dynamic domain boundaries. The experimental observations in our study therefore have broad implications for the understanding of chromatin silencing in yeast and beyond.

  6. Telomere-independent functions of telomerase in nuclei, cytoplasm, and mitochondria

    Energy Technology Data Exchange (ETDEWEB)

    Chiodi, Ilaria; Mondello, Chiara, E-mail: mondello@igm.cnr.it [Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, Pavia (Italy)

    2012-09-28

    Telomerase canonical activity at telomeres prevents telomere shortening, allowing chromosome stability and cellular proliferation. To perform this task, the catalytic subunit (telomerase reverse transcriptase, TERT) of the enzyme works as a reverse transcriptase together with the telomerase RNA component (TERC), adding telomeric repeats to DNA molecule ends. Growing evidence indicates that, besides the telomeric-DNA synthesis activity, TERT has additional functions in tumor development and is involved in many different biological processes, among which cellular proliferation, gene expression regulation, and mitochondrial functionality. TERT has been shown to act independently of TERC in the Wnt-β-catenin signaling pathway, regulating the expression of Wnt target genes, which play a role in development and tumorigenesis. Moreover, TERT RNA-dependent RNA polymerase activity has been found, leading to the genesis of double-stranded RNAs that act as precursor of silencing RNAs. In mitochondria, a TERT TERC-independent reverse transcriptase activity has been described that could play a role in the protection of mitochondrial integrity. In this review, we will discuss some of the extra-telomeric functions of telomerase.

  7. Reversibility of Defective Hematopoiesis Caused by Telomere Shortening in Telomerase Knockout Mice.

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    Aparna Raval

    Full Text Available Telomere shortening is common in bone marrow failure syndromes such as dyskeratosis congenita (DC, aplastic anemia (AA and myelodysplastic syndromes (MDS. However, improved knowledge of the lineage-specific consequences of telomere erosion and restoration of telomere length in hematopoietic progenitors is required to advance therapeutic approaches. We have employed a reversible murine model of telomerase deficiency to compare the dependence of erythroid and myeloid lineage differentiation on telomerase activity. Fifth generation Tert-/- (G5 Tert-/- mice with shortened telomeres have significant anemia, decreased erythroblasts and reduced hematopoietic stem cell (HSC populations associated with neutrophilia and increased myelopoiesis. Intracellular multiparameter analysis by mass cytometry showed significantly reduced cell proliferation and increased sensitivity to activation of DNA damage checkpoints in erythroid progenitors and in erythroid-biased CD150hi HSC, but not in myeloid progenitors. Strikingly, Cre-inducible reactivation of telomerase activity restored hematopoietic stem and progenitor cell (HSPC proliferation, normalized the DNA damage response, and improved red cell production and hemoglobin levels. These data establish a direct link between the loss of TERT activity, telomere shortening and defective erythropoiesis and suggest that novel strategies to restore telomerase function may have an important role in the treatment of the resulting anemia.

  8. Perturbation theory

    International Nuclear Information System (INIS)

    Bartlett, R.; Kirtman, B.; Davidson, E.R.

    1978-01-01

    After noting some advantages of using perturbation theory some of the various types are related on a chart and described, including many-body nonlinear summations, quartic force-field fit for geometry, fourth-order correlation approximations, and a survey of some recent work. Alternative initial approximations in perturbation theory are also discussed. 25 references

  9. BAL31-NGS approach for identification of telomeres de novo in large genomes

    Czech Academy of Sciences Publication Activity Database

    Peška, Vratislav; Sitová, Z.; Fajkus, Petr; Fajkus, Jiří

    2017-01-01

    Roč. 114, FEB2017 (2017), s. 16-27 ISSN 1046-2023 Institutional support: RVO:68081707 Keywords : alga cyanidioschyzon-merolae * macronuclear dna * (tttaggg)(n) telomeres Subject RIV: CE - Biochemistry OBOR OECD: Biochemistry and molecular biology Impact factor: 3.802, year: 2016

  10. Investigation of hyperfine interactions in DNA and antibody of different lineages of mice infected by T. cruzi by perturbed gamma-gamma angular correlation spectroscopy

    International Nuclear Information System (INIS)

    Silva, Andreia dos Santos

    2012-01-01

    In the present work perturbed angular correlation (PAC) spectroscopy was used to measured electric quadrupole interactions in DNA biomolecules of different mice lineages (A/J, C57BL/6, B6AF1, BXA1 e BXA2), samples of different isotypes of immunoglobulin G (IgG1, IgG2a e IgG2b) and active portions of complete and fragmented immunoglobulin responsible by the immune response. Electric quadrupole interactions were also measured in DNA nitrogenous bases (adenine, cytosine, guanine, thymine). PAC measurements were performed using 111 In → 111C d; 111mC d → 111 Cd; 111 Ag → 111 Cd; e 181 Hf → 181 Ta as probe nuclei, and carried out at room temperature and liquid nitrogen temperature, in order to investigate dynamic and static hyperfine interactions, respectively. The biomolecule samples were directly marked with the radioactive parent nuclei, whose atom link to a certain site in the biomolecules. The biological materials as well as the probe nuclei were chosen to investigate the possibility to use PAC spectroscopy to measure hyperfine parameters at nuclei from metallic elements bound to biomolecules (including the use of different probe nuclei produced in the decay of parent nuclei of four different metals) and also to study the behavior of different biomolecules by means of the measured hyperfine parameters. Results show differences in the hyperfine interactions of probe nuclei bound to the studied biomolecules. Such differences were observed by variations in the hyperfine parameters, which depend on the type of biomolecule and the results also show that the probe nuclei atom bound to the molecule in some cases and in others do not. (author)

  11. Loss of loop adenines alters human telomere d[AG3(TTAG3)3] quadruplex folding

    Czech Academy of Sciences Publication Activity Database

    Babinský, M.; Fiala, R.; Kejnovská, Iva; Bednářová, Klára; Marek, R.; Sagi, J.; Sklenář, V.; Vorlíčková, Michaela

    2014-01-01

    Roč. 42, č. 22 (2014), s. 14031-14041 ISSN 0305-1048 R&D Projects: GA ČR(CZ) GAP205/12/0466 Institutional support: RVO:68081707 Keywords : human telomere * DNA quadruplex * cellular DNA Subject RIV: BO - Biophysics Impact factor: 9.112, year: 2014

  12. Telomere biology in healthy aging and disease

    NARCIS (Netherlands)

    Oeseburg, Hisko; de Boer, Rudolf A.; van Gilst, Wiek H.; van der Harst, Pim

    Aging is a biological process that affects most cells, organisms and species. Telomeres have been postulated as a universal biological clock that shortens in parallel with aging in cells. Telomeres are located at the end of the chromosomes and consist of an evolutionary conserved repetitive

  13. Leukocyte telomere dynamics in the elderly

    DEFF Research Database (Denmark)

    Steenstrup, Troels; Hjelmborg, Jacob V B; Mortensen, Laust H

    2013-01-01

    Limited data suggest that leukocytes of the elderly display ultra-short telomeres. It was reported that in some elderly persons leukocyte telomere length (LTL) shows age-dependent elongation. Using cross-sectional and longitudinal models, we characterized LTL dynamics in participants...

  14. The Long and Short of It: The Role of Telomeres in Fetal Origins of Adult Disease

    Directory of Open Access Journals (Sweden)

    Stephanie E. Hallows

    2012-01-01

    Full Text Available Placental insufficiency, maternal malnutrition, and other causes of intrauterine growth restriction (IUGR can significantly affect short-term growth and long-term health. Following IUGR, there is an increased risk for cardiovascular disease and Type 2 Diabetes. The etiology of these diseases is beginning to be elucidated, and premature aging or cellular senescence through increased oxidative stress and DNA damage to telomeric ends may be initiators of these disease processes. This paper will explore the areas where telomere and telomerase biology can have significant effects on various tissues in the body in IUGR outcomes.

  15. Systemic lupus erythematosus and vitamin D deficiency are associated with shorter telomere length among African Americans: a case-control study.

    Directory of Open Access Journals (Sweden)

    Brett M Hoffecker

    Full Text Available Systemic lupus erythematosus (SLE is a chronic systemic autoimmune disease that disproportionately affects African American females. The causes of SLE are unknown but postulated to be a combination of genetic predisposition and environmental triggers. Vitamin D deficiency is one of the possible environmental triggers. In this study we evaluated relationships between vitamin D status, cellular aging (telomere length and anti-telomere antibodies among African American Gullah women with SLE. The study population included African American female SLE patients and unaffected controls from the Sea Island region of South Carolina. Serum 25-hydroxyvitamin D levels were measured using a nonchromatographic radioimmunoassay. Telomere length was measured in genomic DNA of peripheral blood mononuclear cells (PBMCs by monochrome multiplex quantitative PCR. Anti-telomere antibody levels were measured by enzyme-linked immunosorbent assay (ELISA. Patients with SLE had significantly shorter telomeres and higher anti-telomere antibody titers compared to age- and gender-matched unaffected controls. There was a positive correlation between anti-telomere antibody levels and disease activity among patients and a significant correlation of shorter telomeres with lower 25-hydroxyvitamin D levels in both patients and controls. In follow-up examination of a subset of the patients, the patients who remained vitamin D deficient tended to have shorter telomeres than those patients whose 25-hydroxyvitamin D levels were repleted. Increasing 25-hydroxyvitamin D levels in African American patients with SLE may be beneficial in maintaining telomere length and preventing cellular aging. Moreover, anti-telomere antibody levels may be a promising biomarker of SLE status and disease activity.

  16. Survival and growth of yeast without telomere capping by Cdc13 in the absence of Sgs1, Exo1, and Rad9.

    Directory of Open Access Journals (Sweden)

    Hien-Ping Ngo

    2010-08-01

    Full Text Available Maintenance of telomere capping is absolutely essential to the survival of eukaryotic cells. Telomere capping proteins, such as Cdc13 and POT1, are essential for the viability of budding yeast and mammalian cells, respectively. Here we identify, for the first time, three genetic modifications that allow budding yeast cells to survive without telomere capping by Cdc13. We found that simultaneous inactivation of Sgs1, Exo1, and Rad9, three DNA damage response (DDR proteins, is sufficient to allow cell division in the absence of Cdc13. Quantitative amplification of ssDNA (QAOS was used to show that the RecQ helicase Sgs1 plays an important role in the resection of uncapped telomeres, especially in the absence of checkpoint protein Rad9. Strikingly, simultaneous deletion of SGS1 and the nuclease EXO1, further reduces resection at uncapped telomeres and together with deletion of RAD9 permits cell survival without CDC13. Pulsed-field gel electrophoresis studies show that cdc13-1 rad9Delta sgs1Delta exo1Delta strains can maintain linear chromosomes despite the absence of telomere capping by Cdc13. However, with continued passage, the telomeres of such strains eventually become short and are maintained by recombination-based mechanisms. Remarkably, cdc13Delta rad9Delta sgs1Delta exo1Delta strains, lacking any Cdc13 gene product, are viable and can grow indefinitely. Our work has uncovered a critical role for RecQ helicases in limiting the division of cells with uncapped telomeres, and this may provide one explanation for increased tumorigenesis in human diseases associated with mutations of RecQ helicases. Our results reveal the plasticity of the telomere cap and indicate that the essential role of telomere capping is to counteract specific aspects of the DDR.

  17. Processing of semen by density gradient centrifugation selects spermatozoa with longer telomeres for assisted reproduction techniques.

    Science.gov (United States)

    Yang, Qingling; Zhang, Nan; Zhao, Feifei; Zhao, Wanli; Dai, Shanjun; Liu, Jinhao; Bukhari, Ihtisham; Xin, Hang; Niu, Wenbing; Sun, Yingpu

    2015-07-01

    The ends of eukaryotic chromosomes contain specialized chromatin structures called telomeres, the length of which plays a key role in early human embryonic development. Although the effect of sperm preparation techniques on major sperm characteristics, such as concentration, motility and morphology have been previously documented, the possible status of telomere length and its relation with sperm preparation techniques is not well-known for humans. The aim of this study was to investigate the role of density gradient centrifugation in the selection of spermatozoa with longer telomeres for use in assisted reproduction techniques in 105 samples before and after sperm processing. After density gradient centrifugation, the average telomere length of the sperm was significantly longer (6.51 ± 2.54 versus 5.16 ± 2.29, P average motile sperm rate was significantly higher (77.9 ± 11.8 versus 44.6 ± 11.2, P average DNA fragmentation rate was significantly lower (11.1 ± 5.9 versus 25.9 ± 12.9, P sperm count (rs = 0.58; P sperm with longer telomeres. Copyright © 2015 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  18. Systematic and Cell Type-Specific Telomere Length Changes in Subsets of Lymphocytes

    Directory of Open Access Journals (Sweden)

    Jue Lin

    2016-01-01

    Full Text Available Telomeres, the protective DNA-protein complexes at the ends of linear chromosomes, are important for genome stability. Leukocyte or peripheral blood mononuclear cell (PBMC telomere length is a potential biomarker for human aging that integrates genetic, environmental, and lifestyle factors and is associated with mortality and risks for major diseases. However, only a limited number of studies have examined longitudinal changes of telomere length and few have reported data on sorted circulating immune cells. We examined the average telomere length (TL in CD4+, CD8+CD28+, and CD8+CD28− T cells, B cells, and PBMCs, cross-sectionally and longitudinally, in a cohort of premenopausal women. We report that TL changes over 18 months were correlated among these three T cell types within the same participant. Additionally, PBMC TL change was also correlated with those of all three T cell types, and B cells. The rate of shortening for B cells was significantly greater than for the three T cell types. CD8+CD28− cells, despite having the shortest TL, showed significantly more rapid attrition when compared to CD8+CD28+ T cells. These results suggest systematically coordinated, yet cell type-specific responses to factors and pathways contribute to telomere length regulation.

  19. Telomere dysfunction and cell survival: roles for distinctTIN2-containing complexes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sahn-Ho; Davalos, Albert R.; Heo, Seok-Jin; Rodier, Francis; Beausejour, Christian; Kaminker, Patrick; Campisi, Judith

    2006-11-07

    Telomeres are maintained by three DNA binding proteins, TRF1, TRF2 and POT1, and several associated factors. One factor, TIN2, binds TRF1 and TRF2 directly and POT1 indirectly. These and two other proteins form a soluble complex that may be the core telomere-maintenance complex. It is not clear whether subcomplexes exist or function in vivo. Here, we provide evidence for two TIN2 subcomplexes with distinct functions in human cells. TIN2 ablation by RNA interference caused telomere uncapping and p53-independent cell death in all cells tested. However, we isolated two TIN2 complexes from cell lysates, each selectively sensitive to a TIN2 mutant (TIN2-13, TIN2-15C). In cells with wild-type p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere uncapping and eventual growth arrest. In cells lacking p53 function, TIN215C more than TIN2-13 caused genomic instability and cell death. Thus, TIN2 subcomplexes likely have distinct functions in telomere maintenance, and may provide selective targets for eliminating cells with mutant p53.

  20. Distinct functions for the Drosophila piRNA pathway in genome maintenance and telomere protection.

    Directory of Open Access Journals (Sweden)

    Jaspreet S Khurana

    2010-12-01

    Full Text Available Transposons and other selfish DNA elements can be found in all phyla, and mobilization of these elements can compromise genome integrity. The piRNA (PIWI-interacting RNA pathway silences transposons in the germline, but it is unclear if this pathway has additional functions during development. Here we show that mutations in the Drosophila piRNA pathway genes, armi, aub, ago3, and rhi, lead to extensive fragmentation of the zygotic genome during the cleavage stage of embryonic divisions. Additionally, aub and armi show defects in telomere resolution during meiosis and the cleavage divisions; and mutations in lig-IV, which disrupt non-homologous end joining, suppress these fusions. By contrast, lig-IV mutations enhance chromosome fragmentation. Chromatin immunoprecipitation studies show that aub and armi mutations disrupt telomere binding of HOAP, which is a component of the telomere protection complex, and reduce expression of a subpopulation of 19- to 22-nt telomere-specific piRNAs. Mutations in rhi and ago3, by contrast, do not block HOAP binding or production of these piRNAs. These findings uncover genetically separable functions for the Drosophila piRNA pathway. The aub, armi, rhi, and ago3 genes silence transposons and maintain chromosome integrity during cleavage-stage embryonic divisions. However, the aub and armi genes have an additional function in assembly of the telomere protection complex.

  1. Work-related exhaustion and telomere length: a population-based study.

    Directory of Open Access Journals (Sweden)

    Kirsi Ahola

    Full Text Available Psychological stress is suggested to accelerate the rate of biological aging. We investigated whether work-related exhaustion, an indicator of prolonged work stress, is associated with accelerated biological aging, as indicated by shorter leukocyte telomeres, that is, the DNA-protein complexes that cap chromosomal ends in cells.We used data from a representative sample of the Finnish working-age population, the Health 2000 Study. Our sample consisted of 2911 men and women aged 30-64. Work-related exhaustion was assessed using the Maslach Burnout Inventory--General Survey. We determined relative leukocyte telomere length using a quantitative real-time polymerase chain reaction (PCR -based method.After adjustment for age and sex, individuals with severe exhaustion had leukocyte telomeres on average 0.043 relative units shorter (standard error of the mean 0.016 than those with no exhaustion (p = 0.009. The association between exhaustion and relative telomere length remained significant after additional adjustment for marital and socioeconomic status, smoking, body mass index, and morbidities (adjusted difference 0.044 relative units, standard error of the mean 0.017, p = 0.008.These data suggest that work-related exhaustion is related to the acceleration of the rate of biological aging. This hypothesis awaits confirmation in a prospective study measuring changes in relative telomere length over time.

  2. Regulation of homologous recombination at telomeres in budding yeast

    DEFF Research Database (Denmark)

    Eckert-Boulet, Nadine; Lisby, Michael

    2010-01-01

    Homologous recombination is suppressed at normal length telomere sequences. In contrast, telomere recombination is allowed when telomeres erode in the absence of telomerase activity or as a consequence of nucleolytic degradation or incomplete replication. Here, we review the mechanisms that contr...... that contribute to regulating mitotic homologous recombination at telomeres and the role of these mechanisms in signalling short telomeres in the budding yeast Saccharomyces cerevisiae....

  3. Telomere lengthening and other functions of telomerase.

    Science.gov (United States)

    Rubtsova, M P; Vasilkova, D P; Malyavko, A N; Naraikina, Yu V; Zvereva, M I; Dontsova, O A

    2012-04-01

    Telomerase is an enzyme that maintains the length of the telomere. The telomere length specifies the number of divisions a cell can undergo before it finally dies (i.e. the proliferative potential of cells). For example, telomerase is activated in embryonic cell lines and the telomere length is maintained at a constant level; therefore, these cells have an unlimited fission potential. Stem cells are characterized by a lower telomerase activity, which enables only partial compensation for the shortening of telomeres. Somatic cells are usually characterized by the absence of telomerase activity. Telomere shortening leads to the attainment of the Hayflick limit, the transition of cells to a state of senescence. The cells subsequently enter a state of crisis, accompanied by massive cell death. The surviving cells become cancer cells, which are capable both of dividing indefinitely and maintaining telomere length (usually with the aid of telomerase). Telomerase is a reverse transcriptase. It consists of two major components: telomerase RNA (TER) and reverse transcriptase (TERT). TER is a non-coding RNA, and it contains the region which serves as a template for telomere synthesis. An increasing number of articles focussing on the alternative functions of telomerase components have recently started appearing. The present review summarizes data on the structure, biogenesis, and functions of telomerase.

  4. A Shld1-controlled POT1a provides support for repression of ATR signaling at telomeres through RPA exclusion.

    Science.gov (United States)

    Gong, Yi; de Lange, Titia

    2010-11-12

    We previously proposed that POT1 prevents ATR signaling at telomeres by excluding RPA from the single-stranded TTAGGG repeats. Here, we use a Shld1-stabilized degron-POT1a fusion (DD-POT1a) to study the telomeric ATR kinase response. In the absence of Shld1, DD-POT1a degradation resulted in rapid and reversible activation of the ATR pathway in G1 and S/G2. ATR signaling was abrogated by shRNAs to ATR and TopBP1, but shRNAs to the ATM kinase or DNA-PKcs did not affect the telomere damage response. Importantly, ATR signaling in G1 and S/G2 was reduced by shRNAs to RPA. In S/G2, RPA was readily detectable at dysfunctional telomeres, and both POT1a and POT1b were required to exclude RPA and prevent ATR activation. In G1, the accumulation of RPA at dysfunctional telomeres was strikingly less, and POT1a was sufficient to repress ATR signaling. These results support an RPA exclusion model for the repression of ATR signaling at telomeres. Copyright © 2010 Elsevier Inc. All rights reserved.

  5. End-joining inhibition at telomeres requires the translocase and polySUMO-dependent ubiquitin ligase Uls1.

    Science.gov (United States)

    Lescasse, Rachel; Pobiega, Sabrina; Callebaut, Isabelle; Marcand, Stéphane

    2013-03-20

    In eukaryotes, permanent inhibition of the non-homologous end joining (NHEJ) repair pathway at telomeres ensures that chromosome ends do not fuse. In budding yeast, binding of Rap1 to telomere repeats establishes NHEJ inhibition. Here, we show that the Uls1 protein is required for the maintenance of NHEJ inhibition at telomeres. Uls1 protein is a non-essential Swi2/Snf2-related translocase and a Small Ubiquitin-related Modifier (SUMO)-Targeted Ubiquitin Ligase (STUbL) with unknown targets. Loss of Uls1 results in telomere-telomere fusions. Uls1 requirement is alleviated by the absence of poly-SUMO chains and by rap1 alleles lacking SUMOylation sites. Furthermore, Uls1 limits the accumulation of Rap1 poly-SUMO conjugates. We propose that one of Uls1 functions is to clear non-functional poly-SUMOylated Rap1 molecules from telomeres to ensure the continuous efficiency of NHEJ inhibition. Since Uls1 is the only known STUbL with a translocase activity, it can be the general molecular sweeper for the clearance of poly-SUMOylated proteins on DNA in eukaryotes.

  6. Single molecule localization imaging of telomeres and centromeres using fluorescence in situ hybridization and semiconductor quantum dots.

    Science.gov (United States)

    Wang, Le; Zong, Shenfei; Wang, Zhuyuan; Lu, Ju; Chen, Chen; Zhang, Ruohu; Cui, Yiping

    2018-07-13

    Single molecule localization microscopy (SMLM) is a powerful tool for imaging biological targets at the nanoscale. In this report, we present SMLM imaging of telomeres and centromeres using fluorescence in situ hybridization (FISH). The FISH probes were fabricated by decorating CdSSe/ZnS quantum dots (QDs) with telomere or centromere complementary DNA strands. SMLM imaging experiments using commercially available peptide nucleic acid (PNA) probes labeled with organic fluorophores were also conducted to demonstrate the advantages of using QDs FISH probes. Compared with the PNA probes, the QDs probes have the following merits. First, the fluorescence blinking of QDs can be realized in aqueous solution or PBS buffer without thiol, which is a key buffer component for organic fluorophores' blinking. Second, fluorescence blinking of the QDs probe needs only one excitation light (i.e. 405 nm). While fluorescence blinking of the organic fluorophores usually requires two illumination lights, that is, the activation light (i.e. 405 nm) and the imaging light. Third, the high quantum yield, multiple switching times and a good optical stability make the QDs more suitable for long-term imaging. The localization precision achieved in telomeres and centromeres imaging experiments is about 30 nm, which is far beyond the diffraction limit. SMLM has enabled new insights into telomeres or centromeres on the molecular level, and it is even possible to determine the length of telomere and become a potential technique for telomere-related investigation.

  7. Maternal telomere length inheritance in the king penguin.

    Science.gov (United States)

    Reichert, S; Rojas, E R; Zahn, S; Robin, J-P; Criscuolo, F; Massemin, S

    2015-01-01

    Telomeres are emerging as a biomarker for ageing and survival, and are likely important in shaping life-history trade-offs. In particular, telomere length with which one starts in life has been linked to lifelong survival, suggesting that early telomere dynamics are somehow related to life-history trajectories. This result highlights the importance of determining the extent to which telomere length is inherited, as a crucial factor determining early life telomere length. Given the scarcity of species for which telomere length inheritance has been studied, it is pressing to assess the generality of telomere length inheritance patterns. Further, information on how this pattern changes over the course of growth in individuals living under natural conditions should provide some insight on the extent to which environmental constraints also shape telomere dynamics. To fill this gap partly, we followed telomere inheritance in a population of king penguins (Aptenodytes patagonicus). We tested for paternal and maternal influence on chick initial telomere length (10 days old after hatching), and how these relationships changed with chick age (at 70, 200 and 300 days old). Based on a correlative approach, offspring telomere length was positively associated with maternal telomere length early in life (at 10 days old). However, this relationship was not significant at older ages. These data suggest that telomere length in birds is maternally inherited. Nonetheless, the influence of environmental conditions during growth remained an important factor shaping telomere length, as the maternal link disappeared with chicks' age.

  8. Traffic Perturbation

    CERN Multimedia

    C. Colloca TS/FM

    2004-01-01

    TS/FM group informs you that, for the progress of the works at the Prévessin site entrance, some perturbation of the traffic may occur during the week between the 14th and 18th of June for a short duration. Access will be assured at any time. For more information, please contact 160239. C. Colloca TS/FM

  9. Mre11 and Blm-Dependent Formation of ALT-Like Telomeres in Ku-Deficient Ustilago maydis.

    Directory of Open Access Journals (Sweden)

    Eun Young Yu

    2015-10-01

    Full Text Available A subset of human cancer cells uses a specialized, aberrant recombination pathway known as ALT to maintain telomeres, which in these cells are characterized by complex aberrations including length heterogeneity, high levels of unpaired C-strand, and accumulation of extra-chromosomal telomere repeats (ECTR. These phenotypes have not been recapitulated in any standard budding or fission yeast mutant. We found that eliminating Ku70 or Ku80 in the yeast-like fungus Ustilago maydis results initially in all the characteristic telomere aberrations of ALT cancer cells, including C-circles, a highly specific marker of ALT. Subsequently the ku mutants experience permanent G2 cell cycle arrest, accompanied by loss of telomere repeats from chromosome ends and even more drastic accumulation of very short ECTRs (vsECTRs. The deletion of atr1 or chk1 rescued the lethality of the ku mutant, and "trapped" the telomere aberrations in the early ALT-like stage. Telomere abnormalities are telomerase-independent, but dramatically suppressed by deletion of mre11 or blm, suggesting major roles for these factors in the induction of the ALT pathway. In contrast, removal of other DNA damage response and repair factors such as Rad51 has disparate effects on the ALT phenotypes, suggesting that these factors process ALT intermediates or products. Notably, the antagonism of Ku and Mre11 in the induction of ALT is reminiscent of their roles in DSB resection, in which Blm is also known to play a key role. We suggest that an aberrant resection reaction may constitute an early trigger for ALT telomeres, and that the outcomes of ALT are distinct from DSB because of the unique telomere nucleoprotein structure.

  10. Telomeres and the ethics of human cloning.

    Science.gov (United States)

    Allhoff, Fritz

    2004-01-01

    In search of a potential problem with cloning, I investigate the phenomenon of telomere shortening which is caused by cell replication; clones created from somatic cells will have shortened telomeres and therefore reach a state of senescence more rapidly. While genetic intervention might fix this problem at some point in the future, I ask whether, absent technological advances, this biological phenomenon undermines the moral permissibility of cloning.

  11. Acculturation Predicts Negative Affect and Shortened Telomere Length.

    Science.gov (United States)

    Ruiz, R Jeanne; Trzeciakowski, Jerome; Moore, Tiffany; Ayers, Kimberly S; Pickler, Rita H

    2016-10-12

    Chronic stress may accelerate cellular aging. Telomeres, protective "caps" at the end of chromosomes, modulate cellular aging and may be good biomarkers for the effects of chronic stress, including that associated with acculturation. The purpose of this analysis was to examine telomere length (TL) in acculturating Hispanic Mexican American women and to determine the associations among TL, acculturation, and psychological factors. As part of a larger cross-sectional study of 516 pregnant Hispanic Mexican American women, we analyzed DNA in blood samples (N = 56) collected at 22-24 weeks gestation for TL as an exploratory measure using monochrome multiplex quantitative telomere polymerase chain reaction (PCR). We measured acculturation with the Acculturation Rating Scale for Mexican Americans, depression with the Beck Depression Inventory, discrimination with the Experiences of Discrimination Scale, and stress with the Perceived Stress Scale. TL was negatively moderately correlated with two variables of acculturation: Anglo orientation and greater acculturation-level scores. We combined these scores for a latent variable, acculturation, and we combined depression, stress, and discrimination scores in another latent variable, "negative affectivity." Acculturation and negative affectivity were bidirectionally correlated. Acculturation significantly negatively predicted TL. Using structural equation modeling, we found the model had an excellent fit with the root mean square error of approximation estimate = .0001, comparative fit index = 1.0, Tucker-Lewis index = 1.0, and standardized root mean square residual = .05. The negative effects of acculturation on the health of Hispanic women have been previously demonstrated. Findings from this analysis suggest a link between acculturation and TL, which may indicate accelerated cellular aging associated with overall poor health outcomes. © The Author(s) 2016.

  12. Inhibition of the mitotic exit network in response to damaged telomeres.

    Directory of Open Access Journals (Sweden)

    Mauricio Valerio-Santiago

    Full Text Available When chromosomal DNA is damaged, progression through the cell cycle is halted to provide the cells with time to repair the genetic material before it is distributed between the mother and daughter cells. In Saccharomyces cerevisiae, this cell cycle arrest occurs at the G2/M transition. However, it is also necessary to restrain exit from mitosis by maintaining Bfa1-Bub2, the inhibitor of the Mitotic Exit Network (MEN, in an active state. While the role of Bfa1 and Bub2 in the inhibition of mitotic exit when the spindle is not properly aligned and the spindle position checkpoint is activated has been extensively studied, the mechanism by which these proteins prevent MEN function after DNA damage is still unclear. Here, we propose that the inhibition of the MEN is specifically required when telomeres are damaged but it is not necessary to face all types of chromosomal DNA damage, which is in agreement with previous data in mammals suggesting the existence of a putative telomere-specific DNA damage response that inhibits mitotic exit. Furthermore, we demonstrate that the mechanism of MEN inhibition when telomeres are damaged relies on the Rad53-dependent inhibition of Bfa1 phosphorylation by the Polo-like kinase Cdc5, establishing a new key role of this kinase in regulating cell cycle progression.

  13. The binding efficiency of RPA to telomeric G-strands folded into contiguous G-quadruplexes is independent of the number of G4 units.

    Science.gov (United States)

    Lancrey, Astrid; Safa, Layal; Chatain, Jean; Delagoutte, Emmanuelle; Riou, Jean-François; Alberti, Patrizia; Saintomé, Carole

    2018-03-01

    Replication protein A (RPA) is a single-stranded DNA binding protein involved in replication and in telomere maintenance. During telomere replication, G-quadruplexes (G4) can accumulate on the lagging strand template and need to be resolved. It has been shown that human RPA is able to unfold a single G4. Nevertheless, the G-strand of human telomeres is prone to fold into higher-order structures formed by contiguous G-quadruplexes. To understand how RPA deals with these structures, we studied its interaction with telomeric G-strands folding into an increasing number of contiguous G4s. The aim of this study was to determine whether the efficiency of binding/unfolding of hRPA to telomeric G-strands depends on the number of G4 units. Our data show that the number n of contiguous G4 units (n ≥ 2) does not affect the efficiency of hRPA to coat transiently exposed single-stranded telomeric G-strands. This feature may be essential in preventing instability due to G4 structures during telomere replication. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  14. Extreme telomere length dimorphism in the Tasmanian devil and related marsupials suggests parental control of telomere length.

    Directory of Open Access Journals (Sweden)

    Hannah S Bender

    Full Text Available Telomeres, specialised structures that protect chromosome ends, play a critical role in preserving chromosome integrity. Telomere dynamics in the Tasmanian devil (Sarcophilus harrisii are of particular interest in light of the emergence of devil facial tumour disease (DFTD, a transmissible malignancy that causes rapid mortality and threatens the species with extinction. We used fluorescent in situ hybridisation to investigate telomere length in DFTD cells, in healthy Tasmanian devils and in four closely related marsupial species. Here we report that animals in the Order Dasyuromorphia have chromosomes characterised by striking telomere length dimorphism between homologues. Findings in sex chromosomes suggest that telomere length dimorphism may be regulated by events in the parental germlines. Long telomeres on the Y chromosome imply that telomere lengthening occurs during spermatogenesis, whereas telomere diminution occurs during oogenesis. Although found in several somatic cell tissue types, telomere length dimorphism was not found in DFTD cancer cells, which are characterised by uniformly short telomeres. This is, to our knowledge, the first report of naturally occurring telomere length dimorphism in any species and suggests a novel strategy of telomere length control. Comparative studies in five distantly related marsupials and a monotreme indicate that telomere dimorphism evolved at least 50 million years ago.

  15. Telomere stability and telomerase in mesenchymal stem cells

    DEFF Research Database (Denmark)

    Serakinci, Nedime; Graakjaer, Jesper; Kølvrå, Steen

    2008-01-01

    Telomeres are repetitive genetic material that cap and thereby protect the ends of chromosomes. Each time a cell divides, telomeres get shorter. Telomere length is mainly maintained by telomerase. This enzyme is present in high concentrations in the embryonic stem cells and in fast growing...... embryonic cells, and declines with age. It is still unclear to what extent there is telomerase in adult stem cells, but since these are the founder cells of cells of all the tissues in the body, understanding the telomere dynamics and expression of telomerase in adult stem cells is very important....... In the present communication we focus on telomere expression and telomere length in stem cells, with a special focus on mesenchymal stem cells. We consider different mechanisms by which stem cells can maintain telomeres and also focus on the dynamics of telomere length in mesenchymal stem cells, both the overall...

  16. Targeting telomerase and DNA repair in human cancers

    International Nuclear Information System (INIS)

    Prakash Hande, M.

    2014-01-01

    Telomerase reactivation is essential for telomere maintenance in human cancer cells ensuring indefinite proliferation. Targeting telomere homeostasis has become one of the promising strategies in the therapeutic management of tumours. One major potential drawback, however, is the time lag between telomerase inhibition and critically shortened telomeres triggering cell death, allowing cancer cells to acquire drug resistance. Numerous studies over the last decade have highlighted the role of DNA repair proteins such as Poly (ADP-Ribose) Polymerase-1 (PARP-1), and DNA-dependent protein kinase (DNA-PKcs) in the maintenance of telomere homoeostasis. Dysfunctional telomeres, resulting from the loss of telomeric DNA repeats or the loss of function of telomere-associated proteins trigger DNA damage responses similar to that observed for double strand breaks. We have been working on unravelling such synthetic lethality in cancer cells and this talk would be on one such recently concluded study that demonstrates that inhibition of DNA repair pathways, i.e., NHEJ pathway and that of telomerase could be an alternative strategy to enhance anti-tumour effects and circumvent the possibility of drug resistance. (author)

  17. Mechanisms of telomere loss and their consequences for chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

    Muraki, Keiko; Nyhan, Kristine; Han, Limei; Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California at San Francisco, San Francisco, CA (United States)

    2012-10-04

    The ends of chromosomes in mammals, called telomeres, are composed of a 6-bp repeat sequence, TTAGGG, which is added on by the enzyme telomerase. In combination with a protein complex called shelterin, these telomeric repeat sequences form a cap that protects the ends of chromosomes. Due to insufficient telomerase expression, telomeres shorten gradually with each cell division in human somatic cells, which limits the number of times they can divide. The extensive cell division involved in cancer cell progression therefore requires that cancer cells must acquire the ability to maintain telomeres, either through expression of telomerase, or through an alternative mechanism involving recombination. It is commonly thought that the source of many chromosome rearrangements in cancer cells is a result of the extensive telomere shortening that occurs prior to the expression of telomerase. However, despite the expression of telomerase, tumor cells can continue to show chromosome instability due to telomere loss. Dysfunctional telomeres in cancer cells can result from oncogene-induced replication stress, which results in double-strand breaks (DSBs) at fragile sites, including telomeres. DSBs near telomeres are especially prone to chromosome rearrangements, because telomeric regions are deficient in DSB repair. The deficiency in DSB repair near telomeres is also an important mechanism for ionizing radiation-induced replicative senescence in normal human cells. In addition, DSBs near telomeres can result in chromosome instability in mouse embryonic stem cells, suggesting that telomere loss can contribute to heritable chromosome rearrangements. Consistent with this possibility, telomeric regions in humans are highly heterogeneous, and chromosome rearrangements near telomeres are commonly involved in human genetic disease. Understanding the mechanisms of telomere loss will therefore provide important insights into both human cancer and genetic disease.

  18. Mechanisms of telomere loss and their consequences for chromosome instability

    International Nuclear Information System (INIS)

    Muraki, Keiko; Nyhan, Kristine; Han, Limei; Murnane, John P.

    2012-01-01

    The ends of chromosomes in mammals, called telomeres, are composed of a 6-bp repeat sequence, TTAGGG, which is added on by the enzyme telomerase. In combination with a protein complex called shelterin, these telomeric repeat sequences form a cap that protects the ends of chromosomes. Due to insufficient telomerase expression, telomeres shorten gradually with each cell division in human somatic cells, which limits the number of times they can divide. The extensive cell division involved in cancer cell progression therefore requires that cancer cells must acquire the ability to maintain telomeres, either through expression of telomerase, or through an alternative mechanism involving recombination. It is commonly thought that the source of many chromosome rearrangements in cancer cells is a result of the extensive telomere shortening that occurs prior to the expression of telomerase. However, despite the expression of telomerase, tumor cells can continue to show chromosome instability due to telomere loss. Dysfunctional telomeres in cancer cells can result from oncogene-induced replication stress, which results in double-strand breaks (DSBs) at fragile sites, including telomeres. DSBs near telomeres are especially prone to chromosome rearrangements, because telomeric regions are deficient in DSB repair. The deficiency in DSB repair near telomeres is also an important mechanism for ionizing radiation-induced replicative senescence in normal human cells. In addition, DSBs near telomeres can result in chromosome instability in mouse embryonic stem cells, suggesting that telomere loss can contribute to heritable chromosome rearrangements. Consistent with this possibility, telomeric regions in humans are highly heterogeneous, and chromosome rearrangements near telomeres are commonly involved in human genetic disease. Understanding the mechanisms of telomere loss will therefore provide important insights into both human cancer and genetic disease.

  19. Mechanisms of telomere loss and their consequences for chromosome instability

    Directory of Open Access Journals (Sweden)

    Keiko eMuraki

    2012-10-01

    Full Text Available The ends of chromosomes in mammals, called telomeres, are composed of a 6 base pair repeat sequence, TTAGGG, which is added on by the enzyme telomerase. In combination with a protein complex called shelterin, these telomeric repeat sequences form a cap that protects the ends of chromosomes. Due to insufficient telomerase expression, telomeres shorten gradually with each cell division in human somatic cells, which limits the number of times they can divide. The extensive cell division involved in cancer cell progression therefore requires that cancer cells must acquire the ability to maintain telomeres, either through expression of telomerase, or through an alternative mechanism involving recombination. It is commonly thought that the source of many chromosome rearrangements in cancer cells is a result of the extensive telomere shortening that occurs prior to the expression of telomerase. However, despite the expression of telomerase, tumor cells can continue to show chromosome instability due to telomere loss. Dysfunctional telomeres in cancer cells can result from oncogene-induced replication stress, which results in double-strand breaks (DSBs at fragile sites, including telomeres. DSBs near telomeres are especially prone to chromosome rearrangements, because telomeric regions are deficient in DSB repair. The deficiency in DSB repair near telomeres is also an important mechanism for ionizing radiation-induced replicative senescence in normal human cells. In addition, DSBs near telomeres can result in chromosome instability in mouse embryonic stem cells, suggesting that telomere loss can contribute to heritable chromosome rearrangements. Consistent with this possibility, telomeric regions in humans are highly heterogeneous, and chromosome rearrangements near telomeres are commonly involved in human genetic disease. Understanding the mechanisms of telomere loss will therefore provide important insights into both human cancer and genetic disease.

  20. Setting the Trajectory: Racial Disparities in Newborn Telomere Length

    Science.gov (United States)

    Drury, Stacy S.; Esteves, Kyle; Hatch, Virginia; Woodbury, Margaret; Borne, Sophie; Adamski, Alys; Theall, Katherine P.

    2015-01-01

    Objective To explore racial differences in newborn telomere length (TL) and the effect moderation of the sex of the infant while establishing the methodology for the use of newborn blood spots for telomere length analyses. Study design Pregnant mothers were recruited from the Greater New Orleans area. TL was determined using MMQ-PCR on DNA extracted from infant blood spots. Demographic data and other covariates were obtained via maternal report prior to infant birth. Birth outcome data were obtained from medical records and maternal report. Results Black infants weighed significantly less than white infants at birth, and had significantly longer TL than White infants (p=0.0134), with the strongest effect observed in Black female infants. No significant differences in gestational age were present. Conclusions Significant racial differences in TL were present at birth in this sample, even after controlling for a range of birth outcomes and demographic factors. As longer initial TL is predictive of more rapid TL attrition across the life course, these findings provide evidence that, even at birth, biological vulnerability to early life stress may differ by race and sex. PMID:25681203

  1. Telomere shortening and survival in free-living corvids

    NARCIS (Netherlands)

    Salomons, H.M.; Mulder, G.A.; Zande, L. van de; Haussmann, M.F.; Linskens, M.H.K.; Verhulst, S.

    2009-01-01

    Evidence accumulates that telomere shortening reflects lifestyle and predicts remaining lifespan, but little is known of telomere dynamics and their relation to survival under natural conditions. We present longitudinal telomere data in free-living jackdaws (Corvus monedula) and test hypotheses on

  2. The telomere length dynamic and methods of its assessment.

    Science.gov (United States)

    Lin, Kah-Wai; Yan, Ju

    2005-01-01

    Human telomeres are composed of long repeating sequences of TTAGGG, associated with a variety of telomere-binding proteins. Its function as an end-protector of chromosomes prevents the chromosome from end-to-end fusion, recombination and degradation. Telomerase acts as reverse transcriptase in the elongation of telomeres, which prevent the loss of telomeres due to the end replication problems. However, telomerase activity is detected at low level in somatic cells and high level in embryonic stem cells and tumor cells. It confers immortality to embryonic stem cells and tumor cells. In most tumor cells, telomeres are extremely short and stable. Telomere length is an important indicator of the telomerase activity in tumor cells and it may be used in the prognosis of malignancy. Thus, the assessment of telomeres length is of great experimental and clinical significance. This review describes the role of telomere and telomerase in cancer pathogenesis and the dynamics of the telomeres length in different cell types. The various methods of measurement of telomeres length, i.e. southern blot, hybridization protection assay, fluorescence in situ hybridization, primed in situ, quantitative PCR and single telomere length analysis are discussed. The principle and comparative evaluation of these methods are reviewed. The detection of G-strand overhang by telomeric-oligonucleotide ligation assay, primer extension/nick translation assay and electron microscopy are briefly discussed.

  3. Reactivation of chromosomally integrated human herpesvirus-6 by telomeric circle formation.

    Directory of Open Access Journals (Sweden)

    Bhupesh K Prusty

    Full Text Available More than 95% of the human population is infected with human herpesvirus-6 (HHV-6 during early childhood and maintains latent HHV-6 genomes either in an extra-chromosomal form or as a chromosomally integrated HHV-6 (ciHHV-6. In addition, approximately 1% of humans are born with an inheritable form of ciHHV-6 integrated into the telomeres of chromosomes. Immunosuppression and stress conditions can reactivate latent HHV-6 replication, which is associated with clinical complications and even death. We have previously shown that Chlamydia trachomatis infection reactivates ciHHV-6 and induces the formation of extra-chromosomal viral DNA in ciHHV-6 cells. Here, we propose a model and provide experimental evidence for the mechanism of ciHHV-6 reactivation. Infection with Chlamydia induced a transient shortening of telomeric ends, which subsequently led to increased telomeric circle (t-circle formation and incomplete reconstitution of circular viral genomes containing single viral direct repeat (DR. Correspondingly, short t-circles containing parts of the HHV-6 DR were detected in cells from individuals with genetically inherited ciHHV-6. Furthermore, telomere shortening induced in the absence of Chlamydia infection also caused circularization of ciHHV-6, supporting a t-circle based mechanism for ciHHV-6 reactivation.

  4. Telomere dysfunction and cell survival: Roles for distinct TIN2-containing complexes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sahn-ho; Davalos, Albert R.; Heo, Seok-Jin; Rodier, Francis; Zou, Ying; Beausejour, Christian; Kaminker, Patrick; Yannone, Steven M.; Campisi, Judith

    2007-10-02

    Telomeres are maintained by three DNA binding proteins (TRF1, TRF2 and POT1), and several associated factors. One factor, TIN2, binds TRF1 and TRF2 directly and POT1 indirectly. Along with two other proteins, TPP1 and hRap1, these form a soluble complex that may be the core telomere maintenance complex. It is not clear whether sub-complexes also exist in vivo. We provide evidence for two TIN2 sub-complexes with distinct functions in human cells. We isolated these two TIN2 sub-complexes from nuclear lysates of unperturbed cells and cells expressing TIN2 mutants TIN2-13, TIN2-15C, which cannot bind TRF2 or TRF1, respectively. In cells with wild-type p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere uncapping and eventual growth arrest. In cells lacking p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere dysfunction and cell death. Our findings suggest that distinct TIN2 complexes exist, and that TIN2-15C-sensitive subcomplexes are particularly important for cell survival in the absence of functional p53.

  5. Structural Insight into the interaction of Flavonoids with Human Telomeric Sequence

    Science.gov (United States)

    Tawani, Arpita; Kumar, Amit

    2015-01-01

    Flavonoids are a group of naturally available compounds that are an attractive source for drug discovery. Their potential to act as anti-tumourigenic and anti-proliferative agents has been reported previously but is not yet fully understood. Targeting human telomeric G-quadruplex DNA could be one of the mechanisms by which these flavonoids exert anticancer activity. We have performed detailed biophysical studies for the interaction of four representative flavonoids, Luteolin, Quercetin, Rutin and Genistein, with the human telomeric G-quadruplex sequence tetramolecular d-(T2AG3T) (Tel7). In addition, we used NMR spectroscopy to derive the first model for the complex formed between Quercetin and G-quadruplex sequence. The model showed that Quercetin stabilises the G-quadruplex structure and does not open the G-tetrad. It interacts with the telomeric sequence through π-stacking at two sites: between T1pT2 and between G6pT7. Based on our findings, we suggest that Quercetin could be a potent candidate for targeting the telomere and thus, act as a potent anti-cancer agent. PMID:26627543

  6. Association between maternal symptoms of sleep disordered breathing and fetal telomere length.

    Science.gov (United States)

    Salihu, Hamisu M; King, Lindsey; Patel, Priyanshi; Paothong, Arnut; Pradhan, Anupam; Louis, Judette; Naik, Eknath; Marty, Phillip J; Whiteman, Valerie

    2015-04-01

    Our investigation aims to assess the impact of symptoms of maternal sleep-disordered breathing, specifically sleep apnea risk and daytime sleepiness, on fetal leukocyte telomere length. Pregnant women were recruited upon hospital delivery admission. Sleep exposure outcomes were measured using the Berlin Questionnaire to quantify sleep apnea and the Epworth Sleepiness Scale to measure daytime sleepiness. Participants were classified as "High Risk" or "Low Risk" for sleep apnea based on responses to the Berlin, while "Normal" or "Abnormal" daytime sleepiness was determined based on responses to the Epworth. Neonatal umbilical cord blood samples (N = 67) were collected and genomic DNA was isolated from cord blood leukocytes using Quantitative PCR. A ratio of relative telomere length was derived by telomere repeat copy number and single copy gene copy number (T/S ratio) and used to compare telomere lengths. Bootstrap and ANOVA statistical procedures were employed. On the Berlin, 68.7% of participants were classified as Low Risk while 31.3% were classified as High Risk for sleep apnea. According to the Epworth scale, 80.6% were determined to have Normal daytime sleepiness, and 19.4% were found to have Abnormal daytime sleepiness. The T/S ratio among pregnant women at High Risk for sleep apnea was significantly shorter than for those at Low Risk (P value sleep disordered breathing during pregnancy, and suggest sleep disordered breathing as a possible mechanism of accelerated chromosomal aging. © 2015 Associated Professional Sleep Societies, LLC.

  7. Telomere length shortening is associated with treatment-free remission in chronic myeloid leukemia patients

    Directory of Open Access Journals (Sweden)

    Giovanni Caocci

    2016-07-01

    Full Text Available Abstract We studied telomere length in 32 CML patients who discontinued imatinib after achieving complete molecular remission and 32 age-sex-matched controls. The relative telomere length (RTL was determined by q-PCR as the telomere to single copy gene (36B4 ratio normalized to a reference sample (K-562 DNA. Age-corrected RTL (acRTL was also obtained. The 36-month probability of treatment-free remission (TFR was 59.4 %. TFR patients showed shorter acRTL compared to relapsed (mean ± SD = 0.01 ± 0.14 vs 0.20 ± 0.21; p = 0.01. TFR was significantly higher in CML patients with acRTL ≤0.09 (78.9 vs 30.8 %, p = 0.002. CML stem cells harboring longer telomeres possibly maintain a proliferative potential after treatment discontinuation.

  8. Accelerated Telomere Shortening in Acromegaly; IGF-I Induces Telomere Shortening and Cellular Senescence.

    Science.gov (United States)

    Matsumoto, Ryusaku; Fukuoka, Hidenori; Iguchi, Genzo; Odake, Yukiko; Yoshida, Kenichi; Bando, Hironori; Suda, Kentaro; Nishizawa, Hitoshi; Takahashi, Michiko; Yamada, Shozo; Ogawa, Wataru; Takahashi, Yutaka

    2015-01-01

    Patients with acromegaly exhibit reduced life expectancy and increased prevalence of age-related diseases, such as diabetes, hypertension, and cardiovascular disease. However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases. We measured telomere length in patients with acromegaly using quantitative PCR method. The effect of GH and IGF-I on telomere length and cellular senescence was examined in human skin fibroblasts. Patients with acromegaly exhibited shorter telomere length than age-, sex-, smoking-, and diabetes-matched control patients with non-functioning pituitary adenoma (0.62 ± 0.23 vs. 0.75 ± 0.35, respectively, P = 0.047). In addition, telomere length in acromegaly was negatively correlated with the disease duration (R2 = 0.210, P = 0.003). In vitro analysis revealed that not GH but IGF-I induced telomere shortening in human skin fibroblasts. Furthermore, IGF-I-treated cells showed increased senescence-associated β-galactosidase activity and expression of p53 and p21 protein. IGF-I-treated cells reached the Hayflick limit earlier than GH- or vehicle-treated cells, indicating that IGF-I induces cellular senescence. Shortened telomeres in acromegaly and cellular senescence induced by IGF-I can explain, in part, the underlying mechanisms by which acromegaly exhibits an increased morbidity and mortality in association with the excess secretion of IGF-I.

  9. Early Hits and Long-Term Consequences: Tracking the Lasting Impact of Prenatal Smoke Exposure on Telomere Length in Children

    Science.gov (United States)

    McKasson, Sarah; Mabile, Emily; Dunaway, Lauren F.; Drury, Stacy S.

    2013-01-01

    We examined the association between telomere length and prenatal tobacco exposure (PTE) in 104 children aged 4 to 14 years. Salivary telomere length (STL) was determined from salivary DNA using quantitative polymerase chain reaction. Of the children, 18% had maternal reported PTE. Mean STL was significantly lower among children with PTE (6.4 vs 7.5, P < .05). Findings extend the literature demonstrating the negative long-term effects of PTE to include a cellular marker of aging linked to multiple negative health outcomes. PMID:23927510

  10. Telomere biology in aging and cancer: early history and perspectives.

    Science.gov (United States)

    Hayashi, Makoto T

    2018-01-20

    The ends of eukaryotic linear chromosomes are protected from undesired enzymatic activities by a nucleoprotein complex called the telomere. Expanding evidence indicates that telomeres have central functions in human aging and tumorigenesis. While it is undoubtedly important to follow current advances in telomere biology, it is also fruitful to be well informed in seminal historical studies for a comprehensive understanding of telomere biology, and for the anticipation of future directions. With this in mind, I here summarize the early history of telomere biology and current advances in the field, mostly focusing on mammalian studies relevant to aging and cancer.

  11. Telomeres and the natural lifespan limit in humans

    DEFF Research Database (Denmark)

    Steenstrup, Troels; Kark, Jeremy D; Verhulst, Simon

    2017-01-01

    An ongoing debate in demography has focused on whether the human lifespan has a maximal natural limit. Taking a mechanistic perspective, and knowing that short telomeres are associated with diminished longevity, we examined whether telomere length dynamics during adult life could set a maximal...... natural lifespan limit. We define leukocyte telomere length of 5 kb as the 'telomeric brink', which denotes a high risk of imminent death. We show that a subset of adults may reach the telomeric brink within the current life expectancy and more so for a 100-year life expectancy. Thus, secular trends...

  12. Telomere in Aging and Age-Related Diseases

    Directory of Open Access Journals (Sweden)

    Anna Meiliana

    2017-12-01

    Full Text Available BACKGROUND: The number of elderly population in the world keep increasing. In their advanced ages, many elderly face years of disability because of multiple chronic diseases, frailty, making them lost their independence. Consequently, this could have impacts on social and economic stability. A huge challenge has been sent for biomedical researchers to compress or at least eliminate this period of disability and increase the health span. CONTENT: Over the past decades, many studies of telomere biology have demonstrated that telomeres and telomere-associated proteins are implicated in human diseases. Accelerated telomere erosion was clearly correlated with a pack of metabolic and inflammatory diseases. Critically short telomeres or the unprotected end, are likely to form telomeric fusion, generating genomic instability, the cornerstone for carcinogenesis. Enlightening how telomeres involved in the mechanisms underlying the diseases’ pathogenesis was expected to uncover new molecular targets for any important diagnosis or therapeutic implications. SUMMARY: Telomere shortening was foreseen as an imporant mechanism to supress tumor by limiting cellular proliferative capacity by regulating senescence check point activation. Many human diseases and carcinogenesis are causally related to defective telomeres, asserting the importance of telomeres sustainment. Thus, telomere length assessment might serve as an important tool for clinical prognostic, diagnostic, monitoring and management. KEYWORDS: telomerase, cellular senescence, aging, cancer

  13. Telomeres and replicative senescence: Is it only length that counts?

    Science.gov (United States)

    von Zglinicki, T

    2001-07-26

    Telomeres are well established as a major 'replicometer', counting the population doublings in primary human cell cultures and ultimately triggering replicative senescence. However, neither is the pace of this biological clock inert, nor is there a fixed threshold telomere length acting as the universal trigger of replicative senescence. The available data suggest that opening of the telomeric loop and unscheduled exposure of the single-stranded G-rich telomeric overhang might act like a semaphore to signal senescent cell cycle arrest. Short telomere length, telomeric single-strand breaks, low levels of loop-stabilizing proteins, or other factors may trigger this opening of the loop. Thus, both telomere shortening and the ultimate signalling into senescence are able to integrate different environmental and genetic factors, especially oxidative stress-mediated damage, which might otherwise become a thread to genomic stability.

  14. Does Reproductive Investment Decrease Telomere Length in Menidia menidia?

    Directory of Open Access Journals (Sweden)

    Jin Gao

    Full Text Available Given finite resources, intense investment in one life history trait is expected to reduce investment in others. Although telomere length appears to be strongly tied to age in many taxa, telomere maintenance requires energy. We therefore hypothesize that telomere maintenance may trade off against other life history characters. We used natural variation in laboratory populations of Atlantic silversides (Menidia menidia to study the relationship between growth, fecundity, life expectancy, and relative telomere length. In keeping with several other studies on fishes, we found no clear dependence of telomere length on age. However, we did find that more fecund fish tended to have both reduced life expectancy and shorter telomeres. This result is consistent with the hypothesis that there is a trade-off between telomere maintenance and reproductive output.

  15. Aphidicolin synchronization of mouse L cells perturbs the relationship between cell killing and DNA double-strand breakage after X-irradiation

    International Nuclear Information System (INIS)

    Radford, I.R.; Broadhurst, S.

    1988-01-01

    The relationship between X-ray-induced cell killing and DNA double-strand breakage was examined for synchronized mouse L cells that had entered S-phase, G2-phase, mitosis, and G1-phase following release from aphidicolin and compared to asynchronous culture response. Aphidicolin-synchronized cells showed cycle phase-dependent changes in dose-responses for both killing and DNA dsb. However, on the basis of DNA dsb per unit length of DNA required to produce a lethal lesion, aphidicolin-synchronized cells were more sensitive to X-rays than asynchronous cultures. This sensitivity peaked 2 h after release from aphidicolin treatment, and then progressively declined towards the asynchronous culture value. It is argued that results are due to deregulation of the temporal order of DNA replication following aphidicolin treatment, and can be incorporated into the critical DNA target size model by postulating that the targets for radiation action in mammalian cells are DNA-associated with potentially transcriptionally active proto-oncogenes or constitutive fragile sites. (author)

  16. Identification of TTAGGG-binding proteins in Neurospora crassa, a fungus with vertebrate-like telomere repeats.

    Science.gov (United States)

    Casas-Vila, Núria; Scheibe, Marion; Freiwald, Anja; Kappei, Dennis; Butter, Falk

    2015-11-17

    To date, telomere research in fungi has mainly focused on Saccharomyces cerevisiae and Schizosaccharomyces pombe, despite the fact that both yeasts have degenerated telomeric repeats in contrast to the canonical TTAGGG motif found in vertebrates and also several other fungi. Using label-free quantitative proteomics, we here investigate the telosome of Neurospora crassa, a fungus with canonical telomeric repeats. We show that at least six of the candidates detected in our screen are direct TTAGGG-repeat binding proteins. While three of the direct interactors (NCU03416 [ncTbf1], NCU01991 [ncTbf2] and NCU02182 [ncTay1]) feature the known myb/homeobox DNA interaction domain also found in the vertebrate telomeric factors, we additionally show that a zinc-finger protein (NCU07846) and two proteins without any annotated DNA-binding domain (NCU02644 and NCU05718) are also direct double-strand TTAGGG binders. We further find two single-strand binders (NCU02404 [ncGbp2] and NCU07735 [ncTcg1]). By quantitative label-free interactomics we identify TTAGGG-binding proteins in Neurospora crassa, suggesting candidates for telomeric factors that are supported by phylogenomic comparison with yeast species. Intriguingly, homologs in yeast species with degenerated telomeric repeats are also TTAGGG-binding proteins, e.g. in S. cerevisiae Tbf1 recognizes the TTAGGG motif found in its subtelomeres. However, there is also a subset of proteins that is not conserved. While a rudimentary core TTAGGG-recognition machinery may be conserved across yeast species, our data suggests Neurospora as an emerging model organism with unique features.

  17. Long G2 accumulates recombination intermediates and disturbs chromosome segregation at dysfunction telomere in Schizosaccharomyces pombe

    Energy Technology Data Exchange (ETDEWEB)

    Habib, Ahmed G.K.; Masuda, Kenta; Yukawa, Masashi; Tsuchiya, Eiko [Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Ueno, Masaru, E-mail: scmueno@hiroshima-u.ac.jp [Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Research Center for the Mathematics on Chromatin Live Dynamics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan)

    2015-08-14

    Protection of telomere (Pot1) is a single-stranded telomere binding protein which is essential for chromosome ends protection. Fission yeast Rqh1 is a member of RecQ helicases family which has essential roles in the maintenance of genomic stability and regulation of homologous recombination. Double mutant between fission yeast pot1Δ and rqh1 helicase dead (rqh1-hd) maintains telomere by homologous recombination. In pot1Δ rqh1-hd double mutant, recombination intermediates accumulate near telomere which disturb chromosome segregation and make cells sensitive to microtubule inhibitors thiabendazole (TBZ). Deletion of chk1{sup +} or mutation of its kinase domain shortens the G2 of pot1Δ rqh1-hd double mutant and suppresses both the accumulation of recombination intermediates and the TBZ sensitivity of that double mutant. In this study, we asked whether the long G2 is the reason for the TBZ sensitivity of pot1Δ rqh1-hd double mutant. We found that shortening the G2 of pot1Δ rqh1-hd double mutant by additional mutations of wee1 and mik1 or gain of function mutation of Cdc2 suppresses both the accumulation of recombination intermediates and the TBZ sensitivity of pot1Δ rqh1-hd double mutant. Our results suggest that long G2 of pot1Δ rqh1-hd double mutant may allow time for the accumulation of recombination intermediates which disturb chromosome segregation and make cells sensitive to TBZ. - Ηighlights: • We show link between long G2 and accumulation of toxic recombination intermediates. • Accumulation of recombination intermediates at telomere results in TBZ sensitivity. • Activation of DNA damage checkpoint worsens cells' viability in presence of TBZ.

  18. Single-cell telomere-length quantification couples telomere length to meristem activity and stem cell development in Arabidopsis.

    Science.gov (United States)

    González-García, Mary-Paz; Pavelescu, Irina; Canela, Andrés; Sevillano, Xavier; Leehy, Katherine A; Nelson, Andrew D L; Ibañes, Marta; Shippen, Dorothy E; Blasco, Maria A; Caño-Delgado, Ana I

    2015-05-12

    Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Selenium nanoparticles synthesized in aqueous extract of Allium sativum perturbs the structural integrity of Calf thymus DNA through intercalation and groove binding

    International Nuclear Information System (INIS)

    Ezhuthupurakkal, Preedia Babu; Polaki, Lokeswara Rao; Suyavaran, Arumugam; Subastri, Ariraman; Sujatha, Venugopal; Thirunavukkarasu, Chinnasamy

    2017-01-01

    Biomedical application of selenium nanoparticles (SeNPs) demands the eco-friendly composite for synthesis of SeNPs. The present study reports an aqueous extract of Allium sativum (AqEAS) plug-up the current need. Modern spectroscopic, microscopic and gravimetric techniques were employed to characterize the synthesized nanoparticles. Characterization studies revealed the formation of crystalline spherical shaped SeNPs. FTIR spectrum brings out the presence of different functional groups in AqEAS, which influence the SeNPs formation and stabilization. Furthermore the different aspects of the interaction between SeNPs and CT-DNA were scrutinized by various spectroscopic and cyclic voltametric studies. The results reveals the intercalation and groove binding mode of interaction of SeNPs with stacked base pair of CT-DNA. The Stern–Volmer quenching constant (K SV ) were found to be 7.02 × 10 6 Mˉ 1 (ethidium bromide), 4.22 × 10 6 Mˉ 1 (acridine orange) and 7.6 × 10 6 Mˉ 1 (Hoechst) indicating strong binding of SeNPs with CT–DNA. The SeNPs - CT-DNA interactions were directly visualized by atomic force microscopy. The present study unveils the cost effective, innocuous, highly stable SeNPs intricate mechanism of DNA interaction, which will be a milestone in DNA targeted chemotherapy. - Graphical abstract: Highly stable, innocuous, biocompatible SeNPs nanoparticle has been synthesized using Allium sativum (garlic) extract as reductant. The purity and crystallinity were characterized, further divulge the base pare interaction with Calf –Thymus DNA through various spectroscopic methods and atomic force microscopy. Display Omitted - Highlights: • Synthesis of SeNPs in aqueous extract of Allium sativum. • Characterization of synthesized SeNPs using high throughput techniques. • SeNPs directly interact with CT-DNA through intercalation and groove binding.

  20. Selenium nanoparticles synthesized in aqueous extract of Allium sativum perturbs the structural integrity of Calf thymus DNA through intercalation and groove binding

    Energy Technology Data Exchange (ETDEWEB)

    Ezhuthupurakkal, Preedia Babu; Polaki, Lokeswara Rao; Suyavaran, Arumugam; Subastri, Ariraman [Department of Biochemistry and Molecular Biology, Pondicherry University, Puducherry 605 014 (India); Sujatha, Venugopal [Department of Chemistry, Periyar University, Salem 636011 (India); Thirunavukkarasu, Chinnasamy, E-mail: tchinnasamy@hotmail.com [Department of Biochemistry and Molecular Biology, Pondicherry University, Puducherry 605 014 (India)

    2017-05-01

    Biomedical application of selenium nanoparticles (SeNPs) demands the eco-friendly composite for synthesis of SeNPs. The present study reports an aqueous extract of Allium sativum (AqEAS) plug-up the current need. Modern spectroscopic, microscopic and gravimetric techniques were employed to characterize the synthesized nanoparticles. Characterization studies revealed the formation of crystalline spherical shaped SeNPs. FTIR spectrum brings out the presence of different functional groups in AqEAS, which influence the SeNPs formation and stabilization. Furthermore the different aspects of the interaction between SeNPs and CT-DNA were scrutinized by various spectroscopic and cyclic voltametric studies. The results reveals the intercalation and groove binding mode of interaction of SeNPs with stacked base pair of CT-DNA. The Stern–Volmer quenching constant (K{sub SV}) were found to be 7.02 × 10{sup 6} Mˉ{sup 1} (ethidium bromide), 4.22 × 10{sup 6} Mˉ{sup 1} (acridine orange) and 7.6 × 10{sup 6} Mˉ{sup 1} (Hoechst) indicating strong binding of SeNPs with CT–DNA. The SeNPs - CT-DNA interactions were directly visualized by atomic force microscopy. The present study unveils the cost effective, innocuous, highly stable SeNPs intricate mechanism of DNA interaction, which will be a milestone in DNA targeted chemotherapy. - Graphical abstract: Highly stable, innocuous, biocompatible SeNPs nanoparticle has been synthesized using Allium sativum (garlic) extract as reductant. The purity and crystallinity were characterized, further divulge the base pare interaction with Calf –Thymus DNA through various spectroscopic methods and atomic force microscopy. Display Omitted - Highlights: • Synthesis of SeNPs in aqueous extract of Allium sativum. • Characterization of synthesized SeNPs using high throughput techniques. • SeNPs directly interact with CT-DNA through intercalation and groove binding.

  1. Alternative Lengthening of Telomeres: Recurrent Cytogenetic Aberrations and Chromosome Stability under Extreme Telomere Dysfunction

    Directory of Open Access Journals (Sweden)

    Despoina Sakellariou

    2013-11-01

    Full Text Available Human tumors using the alternative lengthening of telomeres (ALT exert high rates of telomere dysfunction. Numerical chromosomal aberrations are very frequent, and structural rearrangements are widely scattered among the genome. This challenging context allows the study of telomere dysfunction-driven chromosomal instability in neoplasia (CIN in a massive scale. We used molecular cytogenetics to achieve detailed karyotyping in 10 human ALT neoplastic cell lines.We identified 518 clonal recombinant chromosomes affected by 649 structural rearrangements. While all human chromosomes were involved in random or clonal, terminal, or pericentromeric rearrangements and were capable to undergo telomere healing at broken ends, a differential recombinatorial propensity of specific genomic regions was noted.We show that ALT cells undergo epigenetic modifications rendering polycentric chromosomes functionally monocentric, and because of increased terminal recombinogenicity, they generate clonal recombinant chromosomes with interstitial telomeric repeats. Losses of chromosomes 13, X, and 22, gains of 2, 3, 5, and 20, and translocation/deletion events involving several common chromosomal fragile sites (CFSs were recurrent. Long-term reconstitution of telomerase activity in ALT cells reduced significantly the rates of random ongoing telomeric and pericentromeric CIN. However, the contribution of CFS in overall CIN remained unaffected, suggesting that in ALT cells whole-genome replication stress is not suppressed by telomerase activation. Our results provide novel insights into ALT-driven CIN, unveiling in parallel specific genomic sites that may harbor genes critical for ALT cancerous cell growth.

  2. Selenium nanoparticles synthesized in aqueous extract of Allium sativum perturbs the structural integrity of Calf thymus DNA through intercalation and groove binding.

    Science.gov (United States)

    Ezhuthupurakkal, Preedia Babu; Polaki, Lokeswara Rao; Suyavaran, Arumugam; Subastri, Ariraman; Sujatha, Venugopal; Thirunavukkarasu, Chinnasamy

    2017-05-01

    Biomedical application of selenium nanoparticles (SeNPs) demands the eco-friendly composite for synthesis of SeNPs. The present study reports an aqueous extract of Allium sativum (AqEAS) plug-up the current need. Modern spectroscopic, microscopic and gravimetric techniques were employed to characterize the synthesized nanoparticles. Characterization studies revealed the formation of crystalline spherical shaped SeNPs. FTIR spectrum brings out the presence of different functional groups in AqEAS, which influence the SeNPs formation and stabilization. Furthermore the different aspects of the interaction between SeNPs and CT-DNA were scrutinized by various spectroscopic and cyclic voltametric studies. The results reveals the intercalation and groove binding mode of interaction of SeNPs with stacked base pair of CT-DNA. The Stern-Volmer quenching constant (K SV ) were found to be 7.02×10 6 M- 1 (ethidium bromide), 4.22×10 6 M- 1 (acridine orange) and 7.6×10 6 M- 1 (Hoechst) indicating strong binding of SeNPs with CT-DNA. The SeNPs - CT-DNA interactions were directly visualized by atomic force microscopy. The present study unveils the cost effective, innocuous, highly stable SeNPs intricate mechanism of DNA interaction, which will be a milestone in DNA targeted chemotherapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Epigenetic Regulation of Telomere Maintenance

    Czech Academy of Sciences Publication Activity Database

    Fojtová, M.; Fajkus, Jiří

    2014-01-01

    Roč. 143, 1-3 (2014), s. 125-135 ISSN 1424-8581 Institutional support: RVO:68081707 Keywords : Chromatin * DNA methylation * Epigenetic s Subject RIV: BO - Biophysics Impact factor: 1.561, year: 2014

  4. The telomere repeat motif of basal Metazoa

    Czech Academy of Sciences Publication Activity Database

    Traut, W.; Szczepanowski, M.; Vítková, Magda; Opitz, Ch.; Marec, František; Zrzavý, Jan

    2007-01-01

    Roč. 15, č. 3, (2007), s. 371-382 ISSN 0967-3849 R&D Projects: GA ČR GA206/06/1860 Institutional research plan: CEZ:AV0Z50070508 Keywords : ancestral telomere * Choanozoa * Cnidaria Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.469, year: 2007

  5. FTO associations with obesity and telomere length.

    Science.gov (United States)

    Zhou, Yuling; Hambly, Brett D; McLachlan, Craig S

    2017-09-01

    This review examines the biology of the Fat mass- and obesity-associated gene (FTO), and the implications of genetic association of FTO SNPs with obesity and genetic aging. Notably, we focus on the role of FTO in the regulation of methylation status as possible regulators of weight gain and genetic aging. We present a theoretical review of the FTO gene with a particular emphasis on associations with UCP2, AMPK, RBL2, IRX3, CUX1, mTORC1 and hormones involved in hunger regulation. These associations are important for dietary behavior regulation and cellular nutrient sensing via amino acids. We suggest that these pathways may also influence telomere regulation. Telomere length (TL) attrition may be influenced by obesity-related inflammation and oxidative stress, and FTO gene-involved pathways. There is additional emerging evidence to suggest that telomere length and obesity are bi-directionally associated. However, the role of obesity risk-related genotypes and associations with TL are not well understood. The FTO gene may influence pathways implicated in regulation of TL, which could help to explain some of the non-consistent relationship between weight phenotype and telomere length that is observed in population studies investigating obesity.

  6. Role of chromatin structure in telomere maintenance

    Czech Academy of Sciences Publication Activity Database

    Kunická, Zuzana; Muselíková Polanská, Eva; Dvořáčková, Martina; Štros, Michal; Fajkus, Jiří

    2008-01-01

    Roč. 28, 5C (2008), s. 193 ISSN 0250-7005. [Eighth International Conference of Anticancer Research. 17.10.2008-22.10.2008, Kos] R&D Projects: GA ČR(CZ) GA204/08/1530 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : telomeres * epigenetics * heterochromatin Subject RIV: BO - Biophysics

  7. Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

    Directory of Open Access Journals (Sweden)

    Igor V. Alabugin

    2011-06-01

    Full Text Available Hybrid molecules combining photoactivated aryl acetylenes and a dicationic lysine moiety cause the most efficient double-strand (ds DNA cleavage known to date for a small molecule. In order to test the connection between the alkylating ability and the DNA-damaging properties of these compounds, we investigated the photoreactivity of three isomeric aryl–tetrafluoropyridinyl (TFP alkynes with amide substituents in different positions (o-, m-, and p- toward a model π-system. Reactions with 1,4-cyclohexadiene (1,4-CHD were used to probe the alkylating properties of the triplet excited states in these three isomers whilst Stern–Volmer quenching experiments were used to investigate the kinetics of photoinduced electron transfer (PET. The three analogous isomeric lysine conjugates cleaved DNA with different efficiencies (34, 15, and 0% of ds DNA cleavage for p-, m-, and o-substituted lysine conjugates, respectively consistent with the alkylating ability of the respective acetamides. The significant protecting effect of the hydroxyl radical and singlet oxygen scavengers to DNA cleavage was shown only with m-lysine conjugate. All three isomeric lysine conjugates inhibited human melanoma cell growth under photoactivation: The p-conjugate had the lowest CC50 (50% cell cytotoxicity value of 1.49 × 10−7 M.

  8. Supersingular quantum perturbations

    International Nuclear Information System (INIS)

    Detwiler, L.C.; Klauder, J.R.

    1975-01-01

    A perturbation potential is called supersingular whenever generally every matrix element of the perturbation in the unperturbed eigenstates is infinite. It follows that supersingular perturbations do not have conventional perturbation expansions, say for energy eigenvalues. By invoking variational arguments, we determine the asymptotic behavior of the energy eigenvalues for asymptotically small values of the coupling constant of the supersingular perturbation

  9. Telomeres, age and reproduction in a long-lived reptile.

    Directory of Open Access Journals (Sweden)

    Virginie Plot

    Full Text Available A major interest has recently emerged in understanding how telomere shortening, mechanism triggering cell senescence, is linked to organism ageing and life history traits in wild species. However, the links between telomere length and key history traits such as reproductive performances have received little attention and remain unclear to date. The leatherback turtle Dermochelys coriacea is a long-lived species showing rapid growth at early stages of life, one of the highest reproductive outputs observed in vertebrates and a dichotomised reproductive pattern related to migrations lasting 2 or 3 years, supposedly associated with different environmental conditions. Here we tested the prediction of blood telomere shortening with age in this species and investigated the relationship between blood telomere length and reproductive performances in leatherback turtles nesting in French Guiana. We found that blood telomere length did not differ between hatchlings and adults. The absence of blood telomere shortening with age may be related to an early high telomerase activity. This telomere-restoring enzyme was formerly suggested to be involved in preventing early telomere attrition in early fast-growing and long-lived species, including squamate reptiles. We found that within one nesting cycle, adult females having performed shorter migrations prior to the considered nesting season had shorter blood telomeres and lower reproductive output. We propose that shorter blood telomeres may result from higher oxidative stress in individuals breeding more frequently (i.e., higher costs of reproduction and/or restoring more quickly their body reserves in cooler feeding areas during preceding migration (i.e., higher foraging costs. This first study on telomeres in the giant leatherback turtle suggests that blood telomere length predicts not only survival chances, but also reproductive performances. Telomeres may therefore be a promising new tool to evaluate

  10. A recessive founder mutation in regulator of telomere elongation helicase 1, RTEL1, underlies severe immunodeficiency and features of Hoyeraal Hreidarsson syndrome.

    Science.gov (United States)

    Ballew, Bari J; Joseph, Vijai; De, Saurav; Sarek, Grzegorz; Vannier, Jean-Baptiste; Stracker, Travis; Schrader, Kasmintan A; Small, Trudy N; O'Reilly, Richard; Manschreck, Chris; Harlan Fleischut, Megan M; Zhang, Liying; Sullivan, John; Stratton, Kelly; Yeager, Meredith; Jacobs, Kevin; Giri, Neelam; Alter, Blanche P; Boland, Joseph; Burdett, Laurie; Offit, Kenneth; Boulton, Simon J; Savage, Sharon A; Petrini, John H J

    2013-08-01

    Dyskeratosis congenita (DC) is a heterogeneous inherited bone marrow failure and cancer predisposition syndrome in which germline mutations in telomere biology genes account for approximately one-half of known families. Hoyeraal Hreidarsson syndrome (HH) is a clinically severe variant of DC in which patients also have cerebellar hypoplasia and may present with severe immunodeficiency and enteropathy. We discovered a germline autosomal recessive mutation in RTEL1, a helicase with critical telomeric functions, in two unrelated families of Ashkenazi Jewish (AJ) ancestry. The affected individuals in these families are homozygous for the same mutation, R1264H, which affects three isoforms of RTEL1. Each parent was a heterozygous carrier of one mutant allele. Patient-derived cell lines revealed evidence of telomere dysfunction, including significantly decreased telomere length, telomere length heterogeneity, and the presence of extra-chromosomal circular telomeric DNA. In addition, RTEL1 mutant cells exhibited enhanced sensitivity to the interstrand cross-linking agent mitomycin C. The molecular data and the patterns of inheritance are consistent with a hypomorphic mutation in RTEL1 as the underlying basis of the clinical and cellular phenotypes. This study further implicates RTEL1 in the etiology of DC/HH and immunodeficiency, and identifies the first known homozygous autosomal recessive disease-associated mutation in RTEL1.

  11. A recessive founder mutation in regulator of telomere elongation helicase 1, RTEL1, underlies severe immunodeficiency and features of Hoyeraal Hreidarsson syndrome.

    Directory of Open Access Journals (Sweden)

    Bari J Ballew

    2013-08-01

    Full Text Available Dyskeratosis congenita (DC is a heterogeneous inherited bone marrow failure and cancer predisposition syndrome in which germline mutations in telomere biology genes account for approximately one-half of known families. Hoyeraal Hreidarsson syndrome (HH is a clinically severe variant of DC in which patients also have cerebellar hypoplasia and may present with severe immunodeficiency and enteropathy. We discovered a germline autosomal recessive mutation in RTEL1, a helicase with critical telomeric functions, in two unrelated families of Ashkenazi Jewish (AJ ancestry. The affected individuals in these families are homozygous for the same mutation, R1264H, which affects three isoforms of RTEL1. Each parent was a heterozygous carrier of one mutant allele. Patient-derived cell lines revealed evidence of telomere dysfunction, including significantly decreased telomere length, telomere length heterogeneity, and the presence of extra-chromosomal circular telomeric DNA. In addition, RTEL1 mutant cells exhibited enhanced sensitivity to the interstrand cross-linking agent mitomycin C. The molecular data and the patterns of inheritance are consistent with a hypomorphic mutation in RTEL1 as the underlying basis of the clinical and cellular phenotypes. This study further implicates RTEL1 in the etiology of DC/HH and immunodeficiency, and identifies the first known homozygous autosomal recessive disease-associated mutation in RTEL1.

  12. The MLH1 ATPase domain is needed for suppressing aberrant formation of interstitial telomeric sequences.

    Science.gov (United States)

    Jia, Pingping; Chai, Weihang

    2018-05-01

    Genome instability gives rise to cancer. MLH1, commonly known for its important role in mismatch repair (MMR), DNA damage signaling and double-strand break (DSB) repair, safeguards genome stability. Recently we have reported a novel role of MLH1 in preventing aberrant formation of interstitial telomeric sequences (ITSs) at intra-chromosomal regions. Deficiency in MLH1, in particular its N-terminus, leads to an increase of ITSs. Here, we identify that the ATPase activity in the MLH1 N-terminal domain is important for suppressing the formation of ITSs. The ATPase activity is also needed for recruiting MLH1 to DSBs. Moreover, defective ATPase activity of MLH1 causes an increase in micronuclei formation. Our results highlight the crucial role of MLH1's ATPase domain in preventing the aberrant formation of telomeric sequences at the intra-chromosomal regions and preserving genome stability. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. The Role of ATRX in the Alternative Lengthening of Telomeres (ALT Phenotype

    Directory of Open Access Journals (Sweden)

    João P. Amorim

    2016-09-01

    Full Text Available Telomeres are responsible for protecting chromosome ends in order to prevent the loss of coding DNA. Their maintenance is required for achieving immortality by neoplastic cells and can occur by upregulation of the telomerase enzyme or through a homologous recombination-associated process, the alternative lengthening of telomeres (ALT. The precise mechanisms that govern the activation of ALT or telomerase in tumor cells are not fully understood, although cellular origin may favor one of the other mechanisms that have been found thus far in mutual exclusivity. Specific mutational events influence ALT activation and maintenance: a unifying frequent feature of tumors that acquire this phenotype are the recurrent mutations of the Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX or Death-Domain Associated Protein (DAXX genes. This review summarizes the established criteria about this phenotype: its prevalence, theoretical molecular mechanisms and relation with ATRX, DAXX and other proteins (directly or indirectly interacting and resulting in the ALT phenotype.

  14. Acrolein-exposed normal human lung fibroblasts in vitro: cellular senescence, enhanced telomere erosion, and degradation of Werner's syndrome protein.

    Science.gov (United States)

    Jang, Jun-Ho; Bruse, Shannon; Huneidi, Salam; Schrader, Ronald M; Monick, Martha M; Lin, Yong; Carter, A Brent; Klingelhutz, Aloysius J; Nyunoya, Toru

    2014-09-01

    Acrolein is a ubiquitous environmental hazard to human health. Acrolein has been reported to activate the DNA damage response and induce apoptosis. However, little is known about the effects of acrolein on cellular senescence. We examined whether acrolein induces cellular senescence in cultured normal human lung fibroblasts (NHLF). We cultured NHLF in the presence or absence of acrolein and determined the effects of acrolein on cell proliferative capacity, senescence-associated β-galactosidase activity, the known senescence-inducing pathways (e.g., p53, p21), and telomere length. We found that acrolein induced cellular senescence by increasing both p53 and p21. The knockdown of p53 mediated by small interfering RNA (siRNA) attenuated acrolein-induced cellular senescence. Acrolein decreased Werner's syndrome protein (WRN), a member of the RecQ helicase family involved in DNA repair and telomere maintenance. Acrolein-induced down-regulation of WRN protein was rescued by p53 knockdown or proteasome inhibition. Finally, we found that acrolein accelerated p53-mediated telomere shortening. These results suggest that acrolein induces p53-mediated cellular senescence accompanied by enhanced telomere attrition and WRN protein down-regulation.

  15. Short telomeres in hatchling snakes: erythrocyte telomere dynamics and longevity in tropical pythons.

    Science.gov (United States)

    Ujvari, Beata; Madsen, Thomas

    2009-10-16

    Telomere length (TL) has been found to be associated with life span in birds and humans. However, other studies have demonstrated that TL does not affect survival among old humans. Furthermore, replicative senescence has been shown to be induced by changes in the protected status of the telomeres rather than the loss of TL. In the present study we explore whether age- and sex-specific telomere dynamics affect life span in a long-lived snake, the water python (Liasis fuscus). Erythrocyte TL was measured using the Telo TAGGG TL Assay Kit (Roche). In contrast to other vertebrates, TL of hatchling pythons was significantly shorter than that of older snakes. However, during their first year of life hatchling TL increased substantially. While TL of older snakes decreased with age, we did not observe any correlation between TL and age in cross-sectional sampling. In older snakes, female TL was longer than that of males. When using recapture as a proxy for survival, our results do not support that longer telomeres resulted in an increased water python survival/longevity. In fish high telomerase activity has been observed in somatic cells exhibiting high proliferation rates. Hatchling pythons show similar high somatic cell proliferation rates. Thus, the increase in TL of this group may have been caused by increased telomerase activity. In older humans female TL is longer than that of males. This has been suggested to be caused by high estrogen levels that stimulate increased telomerase activity. Thus, high estrogen levels may also have caused the longer telomeres in female pythons. The lack of correlation between TL and age among old snakes and the fact that longer telomeres did not appear to affect python survival do not support that erythrocyte telomere dynamics has a major impact on water python longevity.

  16. Short telomeres in hatchling snakes: erythrocyte telomere dynamics and longevity in tropical pythons.

    Directory of Open Access Journals (Sweden)

    Beata Ujvari

    Full Text Available BACKGROUND: Telomere length (TL has been found to be associated with life span in birds and humans. However, other studies have demonstrated that TL does not affect survival among old humans. Furthermore, replicative senescence has been shown to be induced by changes in the protected status of the telomeres rather than the loss of TL. In the present study we explore whether age- and sex-specific telomere dynamics affect life span in a long-lived snake, the water python (Liasis fuscus. METHODOLOGY/PRINCIPAL FINDINGS: Erythrocyte TL was measured using the Telo TAGGG TL Assay Kit (Roche. In contrast to other vertebrates, TL of hatchling pythons was significantly shorter than that of older snakes. However, during their first year of life hatchling TL increased substantially. While TL of older snakes decreased with age, we did not observe any correlation between TL and age in cross-sectional sampling. In older snakes, female TL was longer than that of males. When using recapture as a proxy for survival, our results do not support that longer telomeres resulted in an increased water python survival/longevity. CONCLUSIONS/SIGNIFICANCE: In fish high telomerase activity has been observed in somatic cells exhibiting high proliferation rates. Hatchling pythons show similar high somatic cell proliferation rates. Thus, the increase in TL of this group may have been caused by increased telomerase activity. In older humans female TL is longer than that of males. This has been suggested to be caused by high estrogen levels that stimulate increased telomerase activity. Thus, high estrogen levels may also have caused the longer telomeres in female pythons. The lack of correlation between TL and age among old snakes and the fact that longer telomeres did not appear to affect python survival do not support that erythrocyte telomere dynamics has a major impact on water python longevity.

  17. Accelerated Telomere Shortening in Acromegaly; IGF-I Induces Telomere Shortening and Cellular Senescence

    Science.gov (United States)

    Matsumoto, Ryusaku; Fukuoka, Hidenori; Iguchi, Genzo; Odake, Yukiko; Yoshida, Kenichi; Bando, Hironori; Suda, Kentaro; Nishizawa, Hitoshi; Takahashi, Michiko; Yamada, Shozo; Ogawa, Wataru; Takahashi, Yutaka

    2015-01-01

    Objective Patients with acromegaly exhibit reduced life expectancy and increased prevalence of age-related diseases, such as diabetes, hypertension, and cardiovascular disease. However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases. Methods We measured telomere length in patients with acromegaly using quantitative PCR method. The effect of GH and IGF-I on telomere length and cellular senescence was examined in human skin fibroblasts. Results Patients with acromegaly exhibited shorter telomere length than age-, sex-, smoking-, and diabetes-matched control patients with non-functioning pituitary adenoma (0.62 ± 0.23 vs. 0.75 ± 0.35, respectively, P = 0.047). In addition, telomere length in acromegaly was negatively correlated with the disease duration (R 2 = 0.210, P = 0.003). In vitro analysis revealed that not GH but IGF-I induced telomere shortening in human skin fibroblasts. Furthermore, IGF-I-treated cells showed increased senescence-associated β-galactosidase activity and expression of p53 and p21 protein. IGF-I-treated cells reached the Hayflick limit earlier than GH- or vehicle-treated cells, indicating that IGF-I induces cellular senescence. Conclusion Shortened telomeres in acromegaly and cellular senescence induced by IGF-I can explain, in part, the underlying mechanisms by which acromegaly exhibits an increased morbidity and mortality in association with the excess secretion of IGF-I. PMID:26448623

  18. Accelerated Telomere Shortening in Acromegaly; IGF-I Induces Telomere Shortening and Cellular Senescence.

    Directory of Open Access Journals (Sweden)

    Ryusaku Matsumoto

    Full Text Available Patients with acromegaly exhibit reduced life expectancy and increased prevalence of age-related diseases, such as diabetes, hypertension, and cardiovascular disease. However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases.We measured telomere length in patients with acromegaly using quantitative PCR method. The effect of GH and IGF-I on telomere length and cellular senescence was examined in human skin fibroblasts.Patients with acromegaly exhibited shorter telomere length than age-, sex-, smoking-, and diabetes-matched control patients with non-functioning pituitary adenoma (0.62 ± 0.23 vs. 0.75 ± 0.35, respectively, P = 0.047. In addition, telomere length in acromegaly was negatively correlated with the disease duration (R2 = 0.210, P = 0.003. In vitro analysis revealed that not GH but IGF-I induced telomere shortening in human skin fibroblasts. Furthermore, IGF-I-treated cells showed increased senescence-associated β-galactosidase activity and expression of p53 and p21 protein. IGF-I-treated cells reached the Hayflick limit earlier than GH- or vehicle-treated cells, indicating that IGF-I induces cellular senescence.Shortened telomeres in acromegaly and cellular senescence induced by IGF-I can explain, in part, the underlying mechanisms by which acromegaly exhibits an increased morbidity and mortality in association with the excess secretion of IGF-I.

  19. Insights into Cdc13 Dependent Telomere Length Regulation

    Energy Technology Data Exchange (ETDEWEB)

    M Mason; E Skordalakes

    2011-12-31

    Cdc13 is a single stranded telomere binding protein that specifically localizes to the telomere ends of budding yeasts and is essential for cell viability. It caps the ends of chromosomes thus preventing chromosome end-to-end fusions and exonucleolytic degradation, events that could lead to genomic instability and senescence, the hallmark of aging. Cdc13 is also involved in telomere length regulation by recruiting or preventing access of telomerase to the telomeric overhang. Recruitment of telomerase to the telomeres for G-strand extension is required for continuous cell division, while preventing its access to the telomeres through capping the chromosome ends prevents mitotic events that could lead to cell immortality, the hall mark of carcinogenesis. Cdc13 and its putative homologues human CTC1 and POT1 are therefore key to many biological processes directly associated with life extension and cancer prevention and can be viewed as an ideal target for cancer and age related therapies.

  20. Up-regulation of leucocytes genes implicated in telomere dysfunction and cellular senescence correlates with depression and anxiety severity scores.

    Directory of Open Access Journals (Sweden)

    Jean-Raymond Teyssier

    Full Text Available BACKGROUND: Major depressive disorder (MDD is frequently associated with chronic medical illness responsible of increased disability and mortality. Inflammation and oxidative stress are considered to be the major mediators of the allostatic load, and has been shown to correlate with telomere erosion in the leucocytes of MDD patients, leading to the model of accelerated aging. However, the significance of telomere length as an exclusive biomarker of aging has been questioned on both methodological and biological grounds. Furthermore, telomeres significantly shorten only in patients with long lasting MDD. Sensitive and dynamic functional biomarkers of aging would be clinically useful to evaluate the somatic impact of MDD. METHODOLOGY: To address this issue we have measured in the blood leucocytes of MDD patients (N=17 and controls (N=16 the expression of two genes identified as robust biomarkers of human aging and telomere dysfunction: p16(INK4a and STMN1. We have also quantified the transcripts of genes involved in the repair of oxidative DNA damage at telomeres (OGG1, telomere regulation and elongation (TERT, and in the response to biopsychological stress (FOS and DUSP1. RESULTS: The OGG1, p16(INK4a, and STMN1 gene were significantly up-regulated (25 to 100% in the leucocytes of MDD patients. Expression of p16(INK4a and STMN1 was directly correlated with anxiety scores in the depression group, and that of p16(INK4a, STMN and TERT with the depression and anxiety scores in the combined sample (MDD plus controls. Furthermore, we identified a unique correlative pattern of gene expression in the leucocytes of MDD subjects. CONCLUSIONS: Expression of p16(INK4 and STMN1 is a promising biomarker for future epidemiological assessment of the somatic impact of depressive and anxious symptoms, at both clinical and subclinical level in both depressive patients and general population.

  1. Mechanisms of breast cancer risk in shift workers: association of telomere shortening with the duration and intensity of night work.

    Science.gov (United States)

    Samulin Erdem, Johanna; Notø, Heidi Ødegaard; Skare, Øivind; Lie, Jenny-Anne S; Petersen-Øverleir, Marte; Reszka, Edyta; Pepłońska, Beata; Zienolddiny, Shanbeh

    2017-08-01

    Occupational factors such as shiftwork and especially night work that involves disruption of the circadian rhythm may contribute to increased breast cancer risk. Circadian disruption may also affect telomere length (TL). While short TL generally is associated with increased cancer risk, its association with breast cancer risk is inconclusive. We suggest that working schedules might be an important factor in assessment of effects of TL on breast cancer risk. Moreover, telomere shortening might be a potential mechanism for night work-related breast cancer. In this study, effects of shift work on TL and its association with breast cancer risk were investigated in a nested breast cancer case-control study of Norwegian nurses. TL was assessed by qPCR in DNA from 563 breast cancer patients and 619 controls. Here, we demonstrate that TL is affected by intensive night work schedules, as work with six consecutive night for a period of more than 5 years was associated with decreased telomere lengths (-3.18, 95% CI: -6.46 to -0.58, P = 0.016). Furthermore, telomere shortening is associated with increased breast cancer risk in workers with long periods of consecutive night shifts. Thus, nurses with longer telomere lengths had a lower risk for breast cancer if they had worked more than four (OR: 0.37, 95% CI: 0.16-0.79, P = 0.014) or five (OR: 0.31, 95% CI: 0.10-0.83, P = 0.029) consecutive night shifts for a period of 5 years or more. These data suggest that telomere shortening is associated with the duration and intensity of night work and may be a contributing factor for breast cancer risk among female shift workers. © 2017 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

  2. Telomere Shortening in Neurological Disorders: An Abundance of Unanswered Questions

    OpenAIRE

    Eitan, Erez; Hutchison, Emmette R.; Mattson, Mark P.

    2014-01-01

    Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer’s and Parkinson’s patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and indi...

  3. Two faces of Solanaceae telomeres: a comparison between Nicotiana and Cestrum telomeres and telomere-binding proteins

    Czech Academy of Sciences Publication Activity Database

    Peška, Vratislav; Sýkorová, Eva; Fajkus, Jiří

    2008-01-01

    Roč. 122, 3-4 (2008), s. 380-387 ISSN 1424-8581 R&D Projects: GA AV ČR(CZ) IAA600040505; GA AV ČR(CZ) IAA500040801; GA MŠk(CZ) LC06004 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : POT1-like proteins * C-terminal OB domain * telomere-binding protein Subject RIV: BO - Biophysics Impact factor: 1.965, year: 2008

  4. Telomere Q-PNA-FISH--reliable results from stochastic signals.

    Directory of Open Access Journals (Sweden)

    Andrea Cukusic Kalajzic

    Full Text Available Structural and functional analysis of telomeres is very important for understanding basic biological functions such as genome stability, cell growth control, senescence and aging. Recently, serious concerns have been raised regarding the reliability of current telomere measurement methods such as Southern blot and quantitative polymerase chain reaction. Since telomere length is associated with age related pathologies, including cardiovascular disease and cancer, both at the individual and population level, accurate interpretation of measured results is a necessity. The telomere Q-PNA-FISH technique has been widely used in these studies as well as in commercial analysis for the general population. A hallmark of telomere Q-PNA-FISH is the wide variation among telomere signals which has a major impact on obtained results. In the present study we introduce a specific mathematical and statistical analysis of sister telomere signals during cell culture senescence which enabled us to identify high regularity in their variations. This phenomenon explains the reproducibility of results observed in numerous telomere studies when the Q-PNA-FISH technique is used. In addition, we discuss the molecular mechanisms which probably underlie the observed telomere behavior.

  5. Telomere length in non-neoplastic gastric mucosa and its relationship to H. pylori infection, degree of gastritis, and NSAID use.

    Science.gov (United States)

    Tahara, Tomomitsu; Shibata, Tomoyuki; Kawamura, Tomohiko; Ishizuka, Takamitsu; Okubo, Masaaki; Nagasaka, Mitsuo; Nakagawa, Yoshihito; Arisawa, Tomiyasu; Ohmiya, Naoki; Hirata, Ichiro

    2016-02-01

    Telomere shortening occurs with human aging in many organs and tissues and is accelerated by rapid cell turnover and oxidative injury. We measured average telomere length using quantitative real-time PCR in non-neoplastic gastric mucosa and assessed its relationship to H. pylori-related gastritis, DNA methylation, ulcer disease, and nonsteroidal anti-inflammatory drug (NSAID) usage. Gastric biopsies were obtained from 151 cancer-free subjects including 49 chronic NSAID users and 102 nonusers. Relative telomere length in genomic DNA was measured by real-time PCR. H. pylori infection status, histological severity of gastritis, and serum pepsinogens (PGs) were also investigated. E-cadherin (CDH1) methylation status was determined by methylation-specific PCR (MSP). Average relative telomere length of H. pylori-infected subjects was significantly shortened when compared to H. pylori-negative subjects (p = 0.002) and was closely associated with all histological parameter of gastritis (all p values gastritis and CDH1 methylation status. Also, telomere shortening is accelerated by NSAID usage especially in H. pylori-negative subjects.

  6. Heterocyclic Dications as a New Class of Telomeric G-Quadruplex Targeting Agents

    Science.gov (United States)

    Nanjunda, Rupesh; Musetti, Caterina; Kumar, Arvind; Ismail, Mohamed A.; Farahat, Abdelbasset A.; Wang, Siming; Sissi, Claudia; Palumbo, Manlio; Boykin, David W.; Wilson, W. David

    2013-01-01

    Small molecules that can induce and stabilize G-quadruplex DNA structures represent a novel approach for anti-cancer and anti-parasitic therapy and extensive efforts have been directed towards discovering lead compounds that are capable of stabilizing quadruplexes. The purpose of this study is to explore conformational modifications in a series of heterocyclic dications to discover structural motifs that can selectively bind and stabilize specific G-quadruplexes, such as those present in the human telomere. The G-quadruplex has various potential recognition sites for small molecules; however, the primary interaction site of most of these ligands is the terminal tetrads. Similar to duplex-DNA groove recognition, quadruplex groove recognition by small molecules offers the potential for enhanced selectivity that can be developed into a viable therapeutic strategy. The compounds investigated were selected based on preliminary studies with DB832, a bifuryl-phenyl diamidine with a unique telomere interaction. This compound provides a paradigm that can help in understanding the optimum compound-DNA interactions that lead to quadruplex groove recognition. DNA recognition by the DB832 derivatives was investigated by biophysical experiments such as thermal melting, circular dichroism, mass spectrometry and NMR. Biological studies were also performed to complement the biophysical data. The results suggest a complex binding mechanism which involves the recognition of grooves for some ligands as well as stacking at the terminal tetrads of the human telomeric G-quadruplex for most of the ligands. These molecules represent an excellent starting point for further SAR analysis for diverse modes of quadruplex recognition and subsequent structure optimization for drug development. PMID:22380518

  7. Aberrant leukocyte telomere length in Birdshot Uveitis.

    Science.gov (United States)

    Vazirpanah, Nadia; Verhagen, Fleurieke H; Rothova, Anna; Missotten, Tom O A R; van Velthoven, Mirjam; Den Hollander, Anneke I; Hoyng, Carel B; Radstake, Timothy R D J; Broen, Jasper C A; Kuiper, Jonas J W

    2017-01-01

    Birdshot Uveitis (BU) is an archetypical chronic inflammatory eye disease, with poor visual prognosis, that provides an excellent model for studying chronic inflammation. BU typically affects patients in the fifth decade of life. This suggests that it may represent an age-related chronic inflammatory disease, which has been linked to increased erosion of telomere length of leukocytes. To study this in detail, we exploited a sensitive standardized quantitative real-time polymerase chain reaction to determine the peripheral blood leukocyte telomere length (LTL) in 91 genotyped Dutch BU patients and 150 unaffected Dutch controls. Although LTL erosion rates were very similar between BU patients and healthy controls, we observed that BU patients displayed longer LTL, with a median of log (LTL) = 4.87 (= 74131 base pair) compared to 4.31 (= 20417 base pair) in unaffected controls (PRTEL1. These findings suggest that BU is accompanied by significantly longer LTL.

  8. Psychological Profiles in the Prediction of Leukocyte Telomere Length in Healthy Individuals.

    Directory of Open Access Journals (Sweden)

    Louisia Starnino

    Full Text Available Shorter telomere length (TL may signal premature cellular aging and increased risk for disease. While depression and psychosocial stress have been associated with shorter telomeres, other psychological risk factors for cardiovascular disease have received less attention.To evaluate the association between TL and psychological risk factors (symptoms of anxiety and depression, hostility and defensiveness traits for heart disease, and to examine whether chronological age and sex moderate the associations observed.132 healthy men and women (Mage = 45.34 years completed the Marlowe-Crowne Social Desirability Scale, the Beck Depression Inventory II, The Beck Anxiety Inventory and the Cook-Medley Hostility Scale. Relative TL was measured by quantitative polymerase chain reaction (PCR of total genomic DNA samples. A series of hierarchical linear regressions were performed controlling for pertinent covariates.Shorter TL was observed among individuals high in defensiveness (β = -.221 and depressive symptoms (β = -.213, as well as in those with less hostility (β =.256 and anxiety (β =.220(all Ps<.05. Psychological variables explained 19% of the variance over and above that explained by covariates (age, sex, exercise, alcohol consumption, systemic inflammation, and 24-hr mean arterial pressure. Age moderated the relation between TL and defensiveness (β =.179, p =.03. Sex did not influence any of the relations.Telomere length is associated with psychological burden though the direction of effect differs depending on the psychological variables under study. Further research is needed to determine the reasons for and implications of these seemingly contradictory findings.

  9. Live cell CRISPR-imaging in plants reveals dynamic telomere movements

    KAUST Repository

    Dreissig, Steven

    2017-05-16

    Elucidating the spatio-temporal organization of the genome inside the nucleus is imperative to understand the regulation of genes and non-coding sequences during development and environmental changes. Emerging techniques of chromatin imaging promise to bridge the long-standing gap between sequencing studies which reveal genomic information and imaging studies that provide spatial and temporal information of defined genomic regions. Here, we demonstrate such an imaging technique based on two orthologues of the bacterial CRISPR-Cas9 system. By fusing eGFP/mRuby2 to the catalytically inactive version of Streptococcus pyogenes and Staphylococcus aureus Cas9, we show robust visualization of telomere repeats in live leaf cells of Nicotiana benthamiana. By tracking the dynamics of telomeres visualized by CRISPR-dCas9, we reveal dynamic telomere movements of up to 2 μm within 30 minutes during interphase. Furthermore, we show that CRISPR-dCas9 can be combined with fluorescence-labelled proteins to visualize DNA-protein interactions in vivo. By simultaneously using two dCas9 orthologues, we pave the way for imaging of multiple genomic loci in live plants cells. CRISPR-imaging bears the potential to significantly improve our understanding of the dynamics of chromosomes in live plant cells.

  10. The effect of the severity of obstructive sleep apnea syndrome on telomere length.

    Science.gov (United States)

    Tempaku, Priscila Farias; Mazzotti, Diego Robles; Hirotsu, Camila; Andersen, Monica Levy; Xavier, Gabriela; Maurya, Pawan Kumar; Rizzo, Lucas Bortolotto; Brietzke, Elisa; Belangero, Sintia Iole; Bittencourt, Lia; Tufik, Sergio

    2016-10-25

    Aging is associated with an increase in the prevalence of obstructive sleep apnea syndrome (OSAS) as well as the shortening of telomeres. It is known that OSAS-related factors are stimuli that can contribute to the acceleration of cellular senescence. Thus, the present study aimed to compare the leukocyte telomere length (LTL) between OSAS patients and controls, as well as to verify the correlation between LTL and sleep parameters. We used DNA extracted of 928 individuals from EPISONO to measure the LTL by the quantitative real-time polymerase chain reaction. All individuals were subjected to one full-night polysomnography. LTL was significantly shorter in OSAS patients compared to controls. The results showed negative correlations between LTL and the following variables: apnea-hypopnea index, respiratory disturbance index, desaturation index and wake after sleep onset. LTL was positively correlated with sleep efficiency, total sleep time, basal, minimum and maximum oxygen saturation. Lastly, it was observed that OSAS severity was associated with shorter LTL even after adjusting for sex, age, years of schooling, body mass index, diabetes, stroke and heart attack. In conclusion, our study indicates the presence of an association between LTL and OSAS and a significant impact of severity of OSAS in telomeres shortening.

  11. Sexual differences in telomere selection in the wild.

    Science.gov (United States)

    Olsson, Mats; Pauliny, Angela; Wapstra, Erik; Uller, Tobias; Schwartz, Tonia; Miller, Emily; Blomqvist, Donald

    2011-05-01

    Telomere length is restored primarily through the action of the reverse transcriptase telomerase, which may contribute to a prolonged lifespan in some but not all species and may result in longer telomeres in one sex than the other. To what extent this is an effect of proximate mechanisms (e.g. higher stress in males, higher oestradiol/oestrogen levels in females), or is an evolved adaptation (stronger selection for telomere length in one sex), usually remains unknown. Sand lizard (Lacerta agilis) females have longer telomeres than males and better maintain telomere length through life than males do. We also show that telomere length more strongly contributes to life span and lifetime reproductive success in females than males and that telomere length is under sexually diversifying selection in the wild. Finally, we performed a selection analysis with number of recruited offspring into the adult population as a response variable with telomere length, life span and body size as predictor variables. This showed significant differences in selection pressures between the sexes with strong ongoing selection in females, with these three predictors explaining 63% of the variation in recruitment. Thus, the sexually dimorphic telomere dynamics with longer telomeres in females is a result of past and ongoing selection in sand lizards. Finally, we compared the results from our selection analyses based on Telometric-derived data to the results based on data generated by the software ImageJ. ImageJ resulted in shorter average telomere length, but this difference had virtually no qualitative effect on the patterns of ongoing selection. © 2011 Blackwell Publishing Ltd.

  12. Dual inhibition of ATR and ATM potentiates the activity of trabectedin and lurbinectedin by perturbing the DNA damage response and homologous recombination repair.

    Science.gov (United States)

    Lima, Michelle; Bouzid, Hana; Soares, Daniele G; Selle, Frédéric; Morel, Claire; Galmarini, Carlos M; Henriques, João A P; Larsen, Annette K; Escargueil, Alexandre E

    2016-05-03

    Trabectedin (Yondelis®, ecteinascidin-743, ET-743) is a marine-derived natural product approved for treatment of advanced soft tissue sarcoma and relapsed platinum-sensitive ovarian cancer. Lurbinectedin is a novel anticancer agent structurally related to trabectedin. Both ecteinascidins generate DNA double-strand breaks that are processed through homologous recombination repair (HRR), thereby rendering HRR-deficient cells particularly sensitive. We here characterize the DNA damage response (DDR) to trabectedin and lurbinectedin in HeLa cells. Our results show that both compounds activate the ATM/Chk2 (ataxia-telangiectasia mutated/checkpoint kinase 2) and ATR/Chk1 (ATM and RAD3-related/checkpoint kinase 1) pathways. Interestingly, pharmacological inhibition of Chk1/2, ATR or ATM is not accompanied by any significant improvement of the cytotoxic activity of the ecteinascidins while dual inhibition of ATM and ATR strongly potentiates it. Accordingly, concomitant inhibition of both ATR and ATM is an absolute requirement to efficiently block the formation of γ-H2AX, MDC1, BRCA1 and Rad51 foci following exposure to the ecteinascidins. These results are not restricted to HeLa cells, but are shared by cisplatin-sensitive and -resistant ovarian carcinoma cells. Together, our data identify ATR and ATM as central coordinators of the DDR to ecteinascidins and provide a mechanistic rationale for combining these compounds with ATR and ATM inhibitors.

  13. Unique C. elegans telomeric overhang structures reveal the evolutionarily conserved properties of telomeric DNA

    Czech Academy of Sciences Publication Activity Database

    Školáková, Petra; Foldynová-Trantírková, Silvie; Bednářová, Klára; Fiala, R.; Vorlíčková, Michaela; Trantírek, L.

    2015-01-01

    Roč. 43, č. 9 (2015), s. 4733-4745 ISSN 0305-1048 R&D Projects: GA ČR(CZ) GA13-28310S; GA ČR(CZ) GAP205/12/0466 Institutional support: RVO:68081707 ; RVO:60077344 Keywords : NUCLEASE HYPERSENSITIVE ELEMENT * G-QUADRUPLEX STRUCTURES * I-MOTIF Subject RIV: BO - Biophysics Impact factor: 9.202, year: 2015

  14. Physical activity and telomere length in U.S. men and women: An NHANES investigation.

    Science.gov (United States)

    Tucker, Larry A

    2017-07-01

    The principal objective was to determine the extent to which physical activity (PA) accounts for differences in leukocyte telomere length (LTL) in a large random sample of U.S. adults. Another purpose was to assess the extent to which multiple demographic and lifestyle covariates affect the relationship between PA and LTL. A total of 5823 adults from the National Health and Nutrition Examination Survey (NHANES 1999-2002) were studied cross-sectionally. Employing the quantitative polymerase chain reaction method, LTL was compared to standard reference DNA. PA was indexed using MET-minutes using self-reported frequency, intensity, and duration of participation in 62 physical activities. Covariates were controlled statistically. Telomeres were 15.6 base pairs shorter for each year of chronological age (F=723.2, Pactivity and those in the Sedentary, Low, and Moderate groups were 140, 137, and 111, respectively. Adults with High activity were estimated to have a biologic aging advantage of 9years (140 base pairs÷15.6) over Sedentary adults. The difference in cell aging between those with High and Low activity was also significant, 8.8years, as was the difference between those with High and Moderate PA (7.1years). Overall, PA was significantly and meaningfully associated with telomere length in U.S. men and women. Evidently, adults who participate in high levels of PA tend to have longer telomeres, accounting for years of reduced cellular aging compared to their more sedentary counterparts. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Interaction of Berberine derivative with protein POT1 affect telomere function in cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Nannan; Chen, Siqi; Ma, Yan; Qiu, Jun; Tan, Jia-Heng; Ou, Tian-Miao; Gu, Lian-Quan; Huang, Zhi-Shu [School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou University City, Waihuan East Road 132, Guangzhou 510006 (China); Li, Ding, E-mail: liding@mail.sysu.edu.cn [School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou University City, Waihuan East Road 132, Guangzhou 510006 (China)

    2012-03-16

    Highlights: Black-Right-Pointing-Pointer The protein POT1 plays an important role in telomere protection. Black-Right-Pointing-Pointer Functional POT1 was overexpressed in Escherichia coli for the first time, and purified. Black-Right-Pointing-Pointer Compound Sysu-00692 was found to be the first POT1-binding ligand. Black-Right-Pointing-Pointer Sysu-00692 could interfere with the binding activity of POT1 in vivo. Black-Right-Pointing-Pointer Sysu-00692 had inhibition on telomerase and cell proliferation. -- Abstract: The protein POT1 plays an important role in telomere protection, which is related with telomere elongation and cell immortality. The protein has been recognized as a promising drug target for cancer treatment. In the present study, we cloned, overexpressed in Escherichia coli for the first time, and purified recombinant human POT1. The protein was proved to be active through filter binding assay, FRET and CD experiments. In the initial screening for protein binding ligands using SPR, compound Sysu-00692 was found to bind well with the POT1, which was confirmed with EMSA. Its in vivo activity study showed that compound Sysu-00692 could interfere with the binding between human POT1 and the telomeric DNA through chromatin immunoprecipitation. Besides, the compound showed mild inhibition on telomerase and cell proliferation. As we know, compound Sysu-00692 is the first reported POT1-binding ligand, which could serve as a lead compound for further improvement. This work offered a potentially new approach for drug design for the treatment of cancers.

  16. The effects of social status on biological aging as measured by white-blood-cell telomere length.

    Science.gov (United States)

    Cherkas, L F; Aviv, A; Valdes, A M; Hunkin, J L; Gardner, J P; Surdulescu, G L; Kimura, M; Spector, T D

    2006-10-01

    Low socio-economic status (SES) is associated with a shortened life expectancy, but its effect on aging is unknown. The rate of white-blood-cell (WBC) telomere attrition may be a biological indicator of human aging. We tested the hypothesis that SES is associated with telomere attrition independent of known risk factors influencing the aging process. We studied 1552 female twins. A venous blood sample was taken from each twin and isolated WBCs used for extraction of DNA. Terminal restriction fragment length (TRFL) was measured. Questionnaire data were collected on occupation, education, income, smoking, exercise, height and weight. Standard multiple linear regression and multivariate analyses of variance tested for associations between SES and TRFL, adjusting for covariates. A discordant twin analysis was conducted on a subset to verify findings. WBC telomere length was highly variable but significantly shorter in lower SES groups. The mean difference in TRFL between nonmanual and manual SES groups was 163.2 base pairs (bp) of which 22.9 bp (approximately 14%) was accounted for by body mass index, smoking and exercise. Comparison of TRFL in the 17 most discordant SES twin pairs confirmed this difference. Low SES, in addition to the harmful effects of smoking, obesity and lack of exercise, appears to have an impact on telomere length.

  17. Longitudinal changes of telomere length and epigenetic age related to traumatic stress and post-traumatic stress disorder.

    Science.gov (United States)

    Boks, Marco P; van Mierlo, Hans C; Rutten, Bart P F; Radstake, Timothy R D J; De Witte, Lot; Geuze, Elbert; Horvath, Steve; Schalkwyk, Leonard C; Vinkers, Christiaan H; Broen, Jasper C A; Vermetten, Eric

    2015-01-01

    Several studies have reported an association between traumatic stress and telomere length suggesting that traumatic stress has an impact on ageing at the cellular level. A newly derived tool provides an additional means to investigate cellular ageing by estimating epigenetic age based on DNA methylation profiles. We therefore hypothesise that in a longitudinal study of traumatic stress both indicators of cellular ageing will show increased ageing. We expect that particularly in individuals that developed symptoms of post-traumatic stress disorder (PTSD) increases in these ageing parameters would stand out. From an existing longitudinal cohort study, ninety-six male soldiers were selected based on trauma exposure and the presence of symptoms of PTSD. All military personnel were deployed in a combat zone in Afghanistan and assessed before and 6 months after deployment. The Self-Rating Inventory for PTSD was used to measure the presence of PTSD symptoms, while exposure to combat trauma during deployment was measured with a 19-item deployment experiences checklist. These groups did not differ for age, gender, alcohol consumption, cigarette smoking, military rank, length, weight, or medication use. In DNA from whole blood telomere length was measured and DNA methylation levels were assessed using the Illumina 450K DNA methylation arrays. Epigenetic ageing was estimated using the DNAm age estimator procedure. The association of trauma with telomere length was in the expected direction but not significant (B=-10.2, p=0.52). However, contrary to our expectations, development of PTSD symptoms was associated with the reverse process, telomere lengthening (B=1.91, p=0.018). In concordance, trauma significantly accelerated epigenetic ageing (B=1.97, p=0.032) and similar to the findings in telomeres, development of PTSD symptoms was inversely associated with epigenetic ageing (B=-0.10, p=0.044). Blood cell count, medication and premorbid early life trauma exposure did not

  18. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    Energy Technology Data Exchange (ETDEWEB)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel, E-mail: Daniel.Roca@uv.es [Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, 46071 València (Spain)

    2015-12-07

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π{sub 1}{sup −} and π{sub 2}{sup −} states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  19. Systematic Characterization of the Molecular Mechanisms That Regulate and Mediate Alternative Lengthening of Telomeres in Breast Carcinoma

    Science.gov (United States)

    2015-06-01

    lines with a nominal p-value lower than 1%. Several of the enriched gene sets were associated with DNA replication, mitosis , chromosome segregation...of telomeres: models , mechanisms and implications. Nature reviews. Genetics 11, 319-330 (2010); published online EpubMay (10.1038/nrg2763). 4. A. P...Taylor, M. Mitson, C. Z. Bachrati, D. R. Higgs, R. J. Gibbons, ATRX dysfunction induces replication defects in primary mouse cells. PloS one 9, e92915

  20. Telomere Length in Circulating Lymphocytes: Association with Chromosomal Aberrations

    Czech Academy of Sciences Publication Activity Database

    Hemminki, K.; Rachakonda, S.; Musak, L.; Vymetálková, Veronika; Halasová, E.; Forsti,, A.; Vodičková, Ludmila; Buchancová, J.; Vodička, Pavel; Kumar, R.

    2015-01-01

    Roč. 54, č. 3 (2015), s. 194-196 ISSN 1045-2257 Institutional support: RVO:68378041 Keywords : structural chromosome aberrations * healthy subjects * relative telomere length * genotoxicity * telomere biology Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.960, year: 2015

  1. Telomere Length – a New Biomarker in Medicine

    Directory of Open Access Journals (Sweden)

    Agnieszka Kozłowska

    2015-12-01

    Full Text Available A number of xenobiotics in the environment and workplace influences on our health and life. Biomarkers are tools for measuring such exposures and their effects in the organism. Nowadays, telomere length, epigenetic changes, mutations and changes in gene expression pattern have become new molecular biomarkers. Telomeres play the role of molecular clock, which influences on expectancy of cell life and thus aging, the formation of damages, development diseases and carcinogenesis. The telomere length depends on mechanisms of replication and the activity of telomerase. Telomere length is currently used as a biomarker of susceptibility and/or exposure. This paper describes the role of telomere length as a biomarker of aging cells, oxidative stress, a marker of many diseases including cancer, and as a marker of environmental and occupational exposure.

  2. Tocotrienol-Rich Fraction Prevents Cell Cycle Arrest and Elongates Telomere Length in Senescent Human Diploid Fibroblasts

    Directory of Open Access Journals (Sweden)

    Suzana Makpol

    2011-01-01

    Full Text Available This study determined the molecular mechanisms of tocotrienol-rich fraction (TRF in preventing cellular senescence of human diploid fibroblasts (HDFs. Primary culture of HDFs at various passages were incubated with 0.5 mg/mL TRF for 24 h. Telomere shortening with decreased telomerase activity was observed in senescent HDFs while the levels of damaged DNA and number of cells in G0/G1 phase were increased and S phase cells were decreased. Incubation with TRF reversed the morphology of senescent HDFs to resemble that of young cells with decreased activity of SA-β-gal, damaged DNA, and cells in G0/G1 phase while cells in the S phase were increased. Elongated telomere length and restoration of telomerase activity were observed in TRF-treated senescent HDFs. These findings confirmed the ability of tocotrienol-rich fraction in preventing HDFs cellular ageing by restoring telomere length and telomerase activity, reducing damaged DNA, and reversing cell cycle arrest associated with senescence.

  3. High-throughput telomere length quantification by FISH and its application to human population studies.

    Science.gov (United States)

    Canela, Andrés; Vera, Elsa; Klatt, Peter; Blasco, María A

    2007-03-27

    A major limitation of studies of the relevance of telomere length to cancer and age-related diseases in human populations and to the development of telomere-based therapies has been the lack of suitable high-throughput (HT) assays to measure telomere length. We have developed an automated HT quantitative telomere FISH platform, HT quantitative FISH (Q-FISH), which allows the quantification of telomere length as well as percentage of short telomeres in large human sample sets. We show here that this technique provides the accuracy and sensitivity to uncover associations between telomere length and human disease.

  4. A novel, simple and rapid nondenaturing FISH (ND-FISH) technique for the detection of plant telomeres. Potential used and possible target structures detected.

    Science.gov (United States)

    Cuadrado, Angeles; Golczyk, Hieronim; Jouve, Nicolás

    2009-01-01

    We report a new technique-nondenaturing FISH (ND-FISH)-for the rapid detection of plant telomeres without the need for prior denaturation of the chromosomes. In its development, two modified, synthetic oligonucleotides, 21 nt in length, fluorescently labelled at their 5' and 3' ends and complementary to either the cytidine-rich (C(3)TA(3)) or guanosine-rich (T(3)AG(3)) telomeric DNA strands, were used as probes. The high binding affinity of these probes and the short hybridization time required allows the visualization of plant telomeres in less than an hour. In tests, both probes gave strong signals visualized as double spots at both chromosome ends; this was true of both the mitotic and meiotic chromosomes of barley, wheat, rye, maize, Brachypodium distachyon and Rhoeo spathacea. They were also able to detect telomere motifs at certain intercalary sites in the chromosomes of R. spathacea. To investigate the nature of the target structures detected, the chromosomes were treated with RNase A and single strand-specific nuclease S1 before ND-FISH experiments. Signal formation was resistant to standard enzymatic treatment, but sensitive when much higher enzyme concentrations were used. The results are discussed in relation to current knowledge of telomere structure.

  5. Father Loss and Child Telomere Length.

    Science.gov (United States)

    Mitchell, Colter; McLanahan, Sara; Schneper, Lisa; Garfinkel, Irv; Brooks-Gunn, Jeanne; Notterman, Daniel

    2017-08-01

    Father loss during childhood has negative health and behavioral consequences, but the biological consequences are unknown. Our goal was to examine how father loss (because of separation and/or divorce, death, or incarceration) is associated with cellular function as estimated by telomere length. Data come from the 9-year follow-up of the Fragile Families and Child Wellbeing Study, a birth cohort study of children in 20 large American cities ( N = 2420). Principal measures are as follows: salivary telomere length (sTL), mother reports of father loss, and polymorphisms in genes related to serotonergic and dopaminergic signaling. At 9 years of age, children with father loss have significantly shorter telomeres (14% reduction). Paternal death has the largest association (16%), followed by incarceration (10%), and separation and/or divorce (6%). Changes in income partially mediate these associations (95% mediation for separation and/or divorce, 30% for incarceration, and 25% for death). Effects are 40% greater for boys and 90% greater for children with the most reactive alleles of the serotonin transporter genes when compared with those with the least reactive alleles. No differences were found by age at father loss or a child's race/ethnicity. Father loss has a significant association with children's sTL, with the death of a father showing the largest effect. Income loss explains most of the association between child sTL and separation and/or divorce but much less of the association with incarceration or death. This underscores the important role of fathers in the care and development of children and supplements evidence of the strong negative effects of parental incarceration. Copyright © 2017 by the American Academy of Pediatrics.

  6. Structural Insights into the Quadruplex-Duplex 3' Interface Formed from a Telomeric Repeat: A Potential Molecular Target.

    Science.gov (United States)

    Russo Krauss, Irene; Ramaswamy, Sneha; Neidle, Stephen; Haider, Shozeb; Parkinson, Gary N

    2016-02-03

    We report here on an X-ray crystallographic and molecular modeling investigation into the complex 3' interface formed between putative parallel stranded G-quadruplexes and a duplex DNA sequence constructed from the human telomeric repeat sequence TTAGGG. Our crystallographic approach provides a detailed snapshot of a telomeric 3' quadruplex-duplex junction: a junction that appears to have the potential to form a unique molecular target for small molecule binding and interference with telomere-related functions. This unique target is particularly relevant as current high-affinity compounds that bind putative G-quadruplex forming sequences only rarely have a high degree of selectivity for a particular quadruplex. Here DNA junctions were assembled using different putative quadruplex-forming scaffolds linked at the 3' end to a telomeric duplex sequence and annealed to a complementary strand. We successfully generated a series of G-quadruplex-duplex containing crystals, both alone and in the presence of ligands. The structures demonstrate the formation of a parallel folded G-quadruplex and a B-form duplex DNA stacked coaxially. Most strikingly, structural data reveals the consistent formation of a TAT triad platform between the two motifs. This triad allows for a continuous stack of bases to link the quadruplex motif with the duplex region. For these crystal structures formed in the absence of ligands, the TAT triad interface occludes ligand binding at the 3' quadruplex-duplex interface, in agreement with in silico docking predictions. However, with the rearrangement of a single nucleotide, a stable pocket can be produced, thus providing an opportunity for the binding of selective molecules at the interface.

  7. Developments in perturbation theory

    International Nuclear Information System (INIS)

    Greenspan, E.

    1976-01-01

    Included are sections dealing with perturbation expressions for reactivity, methods for the calculation of perturbed fluxes, integral transport theory formulations for reactivity, generalized perturbation theory, sensitivity and optimization studies, multigroup calculations of bilinear functionals, and solution of inhomogeneous Boltzmann equations with singular operators

  8. Setting the trajectory: racial disparities in newborn telomere length.

    Science.gov (United States)

    Drury, Stacy S; Esteves, Kyle; Hatch, Virginia; Woodbury, Margaret; Borne, Sophie; Adamski, Alys; Theall, Katherine P

    2015-05-01

    To explore racial differences in newborn telomere length (TL) and the effect moderation of the sex of the infant while establishing the methodology for the use of newborn blood spots for TL analyses. Pregnant mothers were recruited from the Greater New Orleans area. TL was determined via monochrome multiplex quantitative real-time polymerase chain reaction on DNA extracted from infant blood spots. Demographic data and other covariates were obtained via maternal report before the infant's birth. Birth outcome data were obtained from medical records and maternal report. Black infants weighed significantly less than white infants at birth and had significantly longer TL than white infants (P=.0134), with the strongest effect observed in black female infants. No significant differences in gestational age were present. Significant racial differences in TL were present at birth in this sample, even after we controlled for a range of birth outcomes and demographic factors. Because longer initial TL is predictive of more rapid TL attrition across the life course, these findings provide evidence that, even at birth, biological vulnerability to early life stress may differ by race and sex. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Telomere Length and the Cancer-Atherosclerosis Trade-Off.

    Directory of Open Access Journals (Sweden)

    Rivka C Stone

    2016-07-01

    Full Text Available Modern humans, the longest-living terrestrial mammals, display short telomeres and repressed telomerase activity in somatic tissues compared with most short-living small mammals. The dual trait of short telomeres and repressed telomerase might render humans relatively resistant to cancer compared with short-living small mammals. However, the trade-off for cancer resistance is ostensibly increased age-related degenerative diseases, principally in the form of atherosclerosis. In this communication, we discuss (a the genetics of human telomere length, a highly heritable complex trait that is influenced by genetic ancestry, sex, and paternal age at conception, (b how cancer might have played a role in the evolution of telomere biology across mammals, (c evidence that in modern humans telomere length is a determinant (rather than only a biomarker of cancer and atherosclerosis, and (d the potential influence of relatively recent evolutionary forces in fashioning the variation in telomere length across and within populations, and their likely lasting impact on major diseases in humans. Finally, we propose venues for future research on human telomere genetics in the context of its potential role in shaping the modern human lifespan.

  10. Ageing and the telomere connection: An intimate relationship with inflammation.

    Science.gov (United States)

    Zhang, Jingwen; Rane, Grishma; Dai, Xiaoyun; Shanmugam, Muthu K; Arfuso, Frank; Samy, Ramar Perumal; Lai, Mitchell Kim Peng; Kappei, Dennis; Kumar, Alan Prem; Sethi, Gautam

    2016-01-01

    Telomeres are the heterochromatic repeat regions at the ends of eukaryotic chromosomes, whose length is considered to be a determinant of biological ageing. Normal ageing itself is associated with telomere shortening. Here, critically short telomeres trigger senescence and eventually cell death. This shortening rate may be further increased by inflammation and oxidative stress and thus affect the ageing process. Apart from shortened or dysfunctional telomeres, cells undergoing senescence are also associated with hyperactivity of the transcription factor NF-κB and overexpression of inflammatory cytokines such as TNF-α, IL-6, and IFN-γ in circulating macrophages. Interestingly, telomerase, a reverse transcriptase that elongates telomeres, is involved in modulating NF-κB activity. Furthermore, inflammation and oxidative stress are implicated as pre-disease mechanisms for chronic diseases of ageing such as neurodegenerative diseases, cardiovascular disease, and cancer. To date, inflammation and telomere shortening have mostly been studied individually in terms of ageing and the associated disease phenotype. However, the interdependent nature of the two demands a more synergistic approach in understanding the ageing process itself and for developing new therapeutic approaches. In this review, we aim to summarize the intricate association between the various inflammatory molecules and telomeres that together contribute to the ageing process and related diseases. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Aberrant leukocyte telomere length in Birdshot Uveitis.

    Directory of Open Access Journals (Sweden)

    Nadia Vazirpanah

    Full Text Available Birdshot Uveitis (BU is an archetypical chronic inflammatory eye disease, with poor visual prognosis, that provides an excellent model for studying chronic inflammation. BU typically affects patients in the fifth decade of life. This suggests that it may represent an age-related chronic inflammatory disease, which has been linked to increased erosion of telomere length of leukocytes.To study this in detail, we exploited a sensitive standardized quantitative real-time polymerase chain reaction to determine the peripheral blood leukocyte telomere length (LTL in 91 genotyped Dutch BU patients and 150 unaffected Dutch controls.Although LTL erosion rates were very similar between BU patients and healthy controls, we observed that BU patients displayed longer LTL, with a median of log (LTL = 4.87 (= 74131 base pair compared to 4.31 (= 20417 base pair in unaffected controls (P<0.0001. The cause underpinning the difference in LTL could not be explained by clinical parameters, immune cell-subtype distribution, nor genetic predisposition based upon the computed weighted genetic risk score of genotyped validated variants in TERC, TERT, NAF1, OBFC1 and RTEL1.These findings suggest that BU is accompanied by significantly longer LTL.

  12. Telomere biology: Rationale for diagnostics and therapeutics in cancer.

    Science.gov (United States)

    Rousseau, Philippe; Autexier, Chantal

    2015-01-01

    The key step of carcinogenesis is the malignant transformation which is fundamentally a telomere biology dysfunction permitting cells to bypass the Hayflick limit and to divide indefinitely and uncontrollably. Thus all partners and structures involved in normal and abnormal telomere maintenance, protection and lengthening can be considered as potential anti-cancer therapeutic targets. In this Point of View we discuss, highlight and provide new perspectives from the current knowledge and understanding to position the different aspects of telomere biology and dysfunction as diagnostic, preventive and curative tools in the field of cancer.

  13. Offspring's Leukocyte Telomere Length, Paternal Age, and Telomere Elongation in Sperm

    DEFF Research Database (Denmark)

    Kimura, Masayuki; Cherkas, Lynn F; Kato, Bernet S

    2008-01-01

    ), the NHLBI Family Heart Study (NHLBI-Heart), the Longitudinal Study of Aging Danish Twins (Danish Twins), and the UK Adult Twin Registry (UK Twins). Using Southern blots, Q-FISH, and flow-FISH, we also measured telomere parameters in sperm from 46 young (50 years) donors. Paternal age...... had an independent effect, expressed by a longer LTL in males of the Framingham Offspring and Danish Twins, males and females of the NHLBI-Heart, and females of UK Twins. For every additional year of paternal age, LTL in offspring increased at a magnitude ranging from half to more than twice......Leukocyte telomere length (LTL) is a complex genetic trait. It shortens with age and is associated with a host of aging-related disorders. Recent studies have observed that offspring of older fathers have longer LTLs. We explored the relation between paternal age and offspring's LTLs in 4 different...

  14. Kaposi's sarcoma herpesvirus C-terminal LANA concentrates at pericentromeric and peri-telomeric regions of a subset of mitotic chromosomes

    International Nuclear Information System (INIS)

    Kelley-Clarke, Brenna; Ballestas, Mary E.; Komatsu, Takashi; Kaye, Kenneth M.

    2007-01-01

    The Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) tethers KSHV terminal repeat (TR) DNA to mitotic chromosomes to efficiently segregate episomes to progeny nuclei. LANA contains N- and C-terminal chromosome binding regions. We now show that C-terminal LANA preferentially concentrates to paired dots at pericentromeric and peri-telomeric regions of a subset of mitotic chromosomes through residues 996-1139. Deletions within C-terminal LANA abolished both self-association and chromosome binding, consistent with a requirement for self-association to bind chromosomes. A deletion abolishing TR DNA binding did not affect chromosome targeting, indicating LANA's localization is not due to binding its recognition sequence in chromosomal DNA. LANA distributed similarly on human and non-human mitotic chromosomes. These results are consistent with C-terminal LANA interacting with a cell factor that concentrates at pericentromeric and peri-telomeric regions of mitotic chromosomes

  15. Impaired Telomere Maintenance and Decreased Canonical WNT Signaling but Normal Ribosome Biogenesis in Induced Pluripotent Stem Cells from X-Linked Dyskeratosis Congenita Patients.

    Directory of Open Access Journals (Sweden)

    Bai-Wei Gu

    Full Text Available Dyskeratosis congenita (DC is an inherited bone marrow failure syndrome characterized by the presence of short telomeres at presentation. Mutations in ten different genes, whose products are involved in the telomere maintenance pathway, have been shown to cause DC. The X-linked form is the most common form of the disease and is caused by mutations in the gene DKC1, encoding the protein dyskerin. Dyskerin is required for the assembly and stability of telomerase and is also involved in ribosomal RNA (rRNA processing where it converts specific uridines to pseudouridine. DC is thought to result from failure to maintain tissues, like blood, that are renewed by stem cell activity, but research into pathogenic mechanisms has been hampered by the difficulty of obtaining stem cells from patients. We reasoned that induced pluripotent stem (iPS cells from X-linked DC patients may provide information about the mechanisms involved. Here we describe the production of iPS cells from DC patients with DKC1 mutations Q31E, A353V and ΔL37. In addition we constructed "corrected" lines with a copy of the wild type dyskerin cDNA expressed from the AAVS1 safe harbor locus. We show that in iPS cells with DKC1 mutations telomere maintenance is compromised with short telomere lengths and decreased telomerase activity. The degree to which telomere lengths are affected by expression of telomerase during reprograming, or with ectopic expression of wild type dyskerin, is variable. The recurrent mutation A353V shows the most severe effect on telomere maintenance. A353V cells but not Q31E or ΔL37 cells, are refractory to correction by expression of wild type DKC1 cDNA. Because dyskerin is involved in both telomere maintenance and ribosome biogenesis it has been postulated that defective ribosome biogenesis and translation may contribute to the disease phenotype. Evidence from mouse and zebra fish models has supported the involvement of ribosome biogenesis but primary cells

  16. Impaired Telomere Maintenance and Decreased Canonical WNT Signaling but Normal Ribosome Biogenesis in Induced Pluripotent Stem Cells from X-Linked Dyskeratosis Congenita Patients.

    Science.gov (United States)

    Gu, Bai-Wei; Apicella, Marisa; Mills, Jason; Fan, Jian-Meng; Reeves, Dara A; French, Deborah; Podsakoff, Gregory M; Bessler, Monica; Mason, Philip J

    2015-01-01

    Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome characterized by the presence of short telomeres at presentation. Mutations in ten different genes, whose products are involved in the telomere maintenance pathway, have been shown to cause DC. The X-linked form is the most common form of the disease and is caused by mutations in the gene DKC1, encoding the protein dyskerin. Dyskerin is required for the assembly and stability of telomerase and is also involved in ribosomal RNA (rRNA) processing where it converts specific uridines to pseudouridine. DC is thought to result from failure to maintain tissues, like blood, that are renewed by stem cell activity, but research into pathogenic mechanisms has been hampered by the difficulty of obtaining stem cells from patients. We reasoned that induced pluripotent stem (iPS) cells from X-linked DC patients may provide information about the mechanisms involved. Here we describe the production of iPS cells from DC patients with DKC1 mutations Q31E, A353V and ΔL37. In addition we constructed "corrected" lines with a copy of the wild type dyskerin cDNA expressed from the AAVS1 safe harbor locus. We show that in iPS cells with DKC1 mutations telomere maintenance is compromised with short telomere lengths and decreased telomerase activity. The degree to which telomere lengths are affected by expression of telomerase during reprograming, or with ectopic expression of wild type dyskerin, is variable. The recurrent mutation A353V shows the most severe effect on telomere maintenance. A353V cells but not Q31E or ΔL37 cells, are refractory to correction by expression of wild type DKC1 cDNA. Because dyskerin is involved in both telomere maintenance and ribosome biogenesis it has been postulated that defective ribosome biogenesis and translation may contribute to the disease phenotype. Evidence from mouse and zebra fish models has supported the involvement of ribosome biogenesis but primary cells from human

  17. The molecular genetics of the telomere biology disorders.

    Science.gov (United States)

    Bertuch, Alison A

    2016-08-02

    The importance of telomere function for human health is exemplified by a collection of Mendelian disorders referred to as the telomere biology disorders (TBDs), telomeropathies, or syndromes of telomere shortening. Collectively, the TBDs cover a spectrum of conditions from multisystem disease presenting in infancy to isolated disease presentations in adulthood, most notably idiopathic pulmonary fibrosis. Eleven genes have been found mutated in the TBDs to date, each of which is linked to some aspect of telomere maintenance. This review summarizes the molecular defects that result from mutations in these genes, highlighting recent advances, including the addition of PARN to the TBD gene family and the discovery of heterozygous mutations in RTEL1 as a cause of familial pulmonary fibrosis.

  18. DNA-dependent protein kinase modulates the anti-cancer properties of silver nanoparticles in human cancer cells.

    Science.gov (United States)

    Lim, Hui Kheng; Gurung, Resham Lal; Hande, M Prakash

    2017-12-01

    Silver nanoparticles (Ag-np) were reported to be toxic to eukaryotic cells. These potentially detrimental effects of Ag-np can be advantageous in experimental therapeutics. They are currently being employed to enhance the therapeutic efficacy of cancer drugs. In this study, we demonstrate that Ag-np treatment trigger the activation of DNA-PKcs and JNK pathway at selected doses, presumably as a physiologic response to DNA damage and repair in normal and malignant cells. Ag-np altered the telomere dynamics by disrupting the shelterin complex located at the telomeres and telomere lengths. The genotoxic effect of Ag-np was not restricted to telomeres but the entire genome as Ag-np induced γ-H2AX foci formation, an indicator of global DNA damage. Inhibition of DNA-PKcs activity sensitised the cancer cells towards the cytotoxicity of Ag-np and substantiated the damaging effect of Ag-np at telomeres in human cancer cells. Abrogation of JNK mediated DNA repair and extensive damage of telomeres led to greater cell death following Ag-np treatment in DNA-PKcs inhibited cancer cells. Collectively, this study suggests that improved anti-proliferative and cytotoxic effects of Ag-np treatment in cancer cells can be achieved by the inhibition of DNA-PKcs. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Childhood adversity, social support, and telomere length among perinatal women.

    Science.gov (United States)

    Mitchell, Amanda M; Kowalsky, Jennifer M; Epel, Elissa S; Lin, Jue; Christian, Lisa M

    2018-01-01

    Adverse perinatal health outcomes are heightened among women with psychosocial risk factors, including childhood adversity and a lack of social support. Biological aging could be one pathway by which such outcomes occur. However, data examining links between psychosocial factors and indicators of biological aging among perinatal women are limited. The current study examined the associations of childhood socioeconomic status (SES), childhood trauma, and current social support with telomere length in peripheral blood mononuclear cells (PBMCs) in a sample of 81 women assessed in early, mid, and late pregnancy as well as 7-11 weeks postpartum. Childhood SES was defined as perceived childhood social class and parental educational attainment. Measures included the Childhood Trauma Questionnaire, Center for Epidemiologic Studies-Depression Scale, Multidimensional Scale of Perceived Social Support, and average telomere length in PBMCs. Per a linear mixed model, telomere length did not change across pregnancy and postpartum visits; thus, subsequent analyses defined telomere length as the average across all available timepoints. ANCOVAs showed group differences by perceived childhood social class, maternal and paternal educational attainment, and current family social support, with lower values corresponding with shorter telomeres, after adjustment for possible confounds. No effects of childhood trauma or social support from significant others or friends on telomere length were observed. Findings demonstrate that while current SES was not related to telomeres, low childhood SES, independent of current SES, and low family social support were distinct risk factors for cellular aging in women. These data have relevance for understanding potential mechanisms by which early life deprivation of socioeconomic and relationship resources affect maternal health. In turn, this has potential significance for intergenerational transmission of telomere length. The predictive value of

  20. Telomere dynamics and homeostasis in a transmissible cancer.

    Science.gov (United States)

    Ujvari, Beata; Pearse, Anne-Maree; Taylor, Robyn; Pyecroft, Stephen; Flanagan, Cassandra; Gombert, Sara; Papenfuss, Anthony T; Madsen, Thomas; Belov, Katherine

    2012-01-01

    Devil Facial Tumour Disease (DFTD) is a unique clonal cancer that threatens the world's largest carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii) with extinction. This transmissible cancer is passed between individual devils by cell implantation during social interactions. The tumour arose in a Schwann cell of a single devil over 15 years ago and since then has expanded clonally, without showing signs of replicative senescence; in stark contrast to a somatic cell that displays a finite capacity for replication, known as the "Hayflick limit". In the present study we investigate the role of telomere length, measured as Telomere Copy Number (TCN), and telomerase and shelterin gene expression, as well as telomerase activity in maintaining hyperproliferation of Devil Facial Tumour (DFT) cells. Our results show that DFT cells have short telomeres. DFTD TCN does not differ between geographic regions or between strains. However, TCN has increased over time. Unlimited cell proliferation is likely to have been achieved through the observed up-regulation of the catalytic subunit of telomerase (TERT) and concomitant activation of telomerase. Up-regulation of the central component of shelterin, the TRF1-intercating nuclear factor 2 (TINF2) provides DFT a mechanism for telomere length homeostasis. The higher expression of both TERT and TINF2 may also protect DFT cells from genomic instability and enhance tumour proliferation. DFT cells appear to monitor and regulate the length of individual telomeres: i.e. shorter telomeres are elongated by up-regulation of telomerase-related genes; longer telomeres are protected from further elongation by members of the shelterin complex, which may explain the lack of spatial and strain variation in DFT telomere copy number. The observed longitudinal increase in gene expression in DFT tissue samples and telomerase activity in DFT cell lines might indicate a selection for more stable tumours with higher proliferative potential.

  1. Telomere dynamics and homeostasis in a transmissible cancer.

    Directory of Open Access Journals (Sweden)

    Beata Ujvari

    Full Text Available Devil Facial Tumour Disease (DFTD is a unique clonal cancer that threatens the world's largest carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii with extinction. This transmissible cancer is passed between individual devils by cell implantation during social interactions. The tumour arose in a Schwann cell of a single devil over 15 years ago and since then has expanded clonally, without showing signs of replicative senescence; in stark contrast to a somatic cell that displays a finite capacity for replication, known as the "Hayflick limit".In the present study we investigate the role of telomere length, measured as Telomere Copy Number (TCN, and telomerase and shelterin gene expression, as well as telomerase activity in maintaining hyperproliferation of Devil Facial Tumour (DFT cells. Our results show that DFT cells have short telomeres. DFTD TCN does not differ between geographic regions or between strains. However, TCN has increased over time. Unlimited cell proliferation is likely to have been achieved through the observed up-regulation of the catalytic subunit of telomerase (TERT and concomitant activation of telomerase. Up-regulation of the central component of shelterin, the TRF1-intercating nuclear factor 2 (TINF2 provides DFT a mechanism for telomere length homeostasis. The higher expression of both TERT and TINF2 may also protect DFT cells from genomic instability and enhance tumour proliferation.DFT cells appear to monitor and regulate the length of individual telomeres: i.e. shorter telomeres are elongated by up-regulation of telomerase-related genes; longer telomeres are protected from further elongation by members of the shelterin complex, which may explain the lack of spatial and strain variation in DFT telomere copy number. The observed longitudinal increase in gene expression in DFT tissue samples and telomerase activity in DFT cell lines might indicate a selection for more stable tumours with higher proliferative

  2. DNA and RNA Quadruplex-Binding Proteins

    Czech Academy of Sciences Publication Activity Database

    Brázda, Václav; Haroniková, Lucia; Liao, J.C.C.; Fojta, Miroslav

    2014-01-01

    Roč. 15, č. 10 (2014), s. 17493-17517 E-ISSN 1422-0067 R&D Projects: GA ČR(CZ) GBP206/12/G151 Institutional support: RVO:68081707 Keywords : DNA quadruplex * RNA quadruplex * telomere Subject RIV: BO - Biophysics Impact factor: 2.862, year: 2014

  3. Direct fluorescence in situ hybridization on human metaphase chromosomes using quantum dot-platinum labeled DNA probes

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Gyoyeon [Chemical Kinomics Research Center, Future Convergence Research Division, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Biological Chemistry, Korea University of Science and Technology, 217, Gajeong-ro, Yuseong-gu, Deajeon (Korea, Republic of); Lee, Hansol [Chemical Kinomics Research Center, Future Convergence Research Division, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Lee, Jiyeon, E-mail: jylee@kist.re.kr [Chemical Kinomics Research Center, Future Convergence Research Division, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Biological Chemistry, Korea University of Science and Technology, 217, Gajeong-ro, Yuseong-gu, Deajeon (Korea, Republic of)

    2015-11-13

    The telomere shortening in chromosomes implies the senescence, apoptosis, or oncogenic transformation of cells. Since detecting telomeres in aging and diseases like cancer, is important, the direct detection of telomeres has been a very useful biomarker. We propose a telomere detection method using a newly synthesized quantum dot (QD) based probe with oligonucleotide conjugation and direct fluorescence in situ hybridization (FISH). QD-oligonucleotides were prepared with metal coordination bonding based on platinum-guanine binding reported in our previous work. The QD-oligonucleotide conjugation method has an advantage where any sequence containing guanine at the end can be easily bound to the starting QD-Pt conjugate. A synthesized telomeric oligonucleotide was bound to the QD-Pt conjugate successfully and this probe hybridized specifically on the telomere of fabricated MV-4-11 and MOLT-4 chromosomes. Additionally, the QD-telomeric oligonucleotide probe successfully detected the telomeres on the CGH metaphase slide. Due to the excellent photostability and high quantum yield of QDs, the QD-oligonucleotide probe has high fluorescence intensity when compared to the organic dye-oligonucleotide probe. Our QD-oligonucleotide probe, conjugation method of this QD probe, and hybridization protocol with the chromosomes can be a useful tool for chromosome painting and FISH. - Highlights: • We prepared a probe linked between QD and telomeric oligonucleotide with platinum-guanine bonding. • Telomeres were detected by our new telomere probes successfully in three different human metaphase chromosomes. • QDPt-DNA probe has high fluorescence intensity in comparison with organic dye-DNA probe.

  4. Radiation chemically induced telomerization of ethylene with selected telogens

    International Nuclear Information System (INIS)

    Wachtendunk, H.J. von.

    1975-01-01

    The suitability of different compounds for the use as telogenes in the telomerization of ethylene has been studied. In all cases the reactions are initiated by the γ-radiation of a 60 Co-source. Temperature programed gas chromatography has proved to be an adequate method of analysis. In the teleomerization process with ethylene also methane tri carboxylic acid tri-ethylene ester (MTE), ortho-formic acid tri-ethylene ester (o-ASE), formic acid, bromium cyane, chlorine cyane and dicyane have been used. The telomerization of MTE and ethylene has been performed successfully with a high yield. The dependence of the reaction on temperature, pressure, radiation dose has been studied as well as the influence of a solvent (acetonitrile). In the attempt to telomerize ortho-formic acid tri-ethylene ester only high molecular weight solid product could be isolated. No interpretable results could be obtained for the telomerization of formic acid with ethylene. In the case of the radiation induced telomerization of chlorine cyane or di-cyane with ethylene in the gas phase, no reaction products could be found. No telomerization between di-cyane and ethylene has been observed even when palladium (II)-cyanide is used as a catalyst of after cocatalys is with triphenyl-phosphile in acetonitrile. (orig./HK) [de

  5. Telomeres and viruses: common themes of genome maintenance

    Science.gov (United States)

    Deng, Zhong; Wang, Zhuo; Lieberman, Paul M.

    2012-01-01

    Genome maintenance mechanisms actively suppress genetic instability associated with cancer and aging. Some viruses provoke genetic instability by subverting the host’s control of genome maintenance. Viruses have their own specialized strategies for genome maintenance, which can mimic and modify host cell processes. Here, we review some of the common features of genome maintenance utilized by viruses and host chromosomes, with a particular focus on terminal repeat (TR) elements. The TRs of cellular chromosomes, better known as telomeres, have well-established roles in cellular chromosome stability. Cellular telomeres are themselves maintained by viral-like mechanisms, including self-propagation by reverse transcription, recombination, and retrotransposition. Viral TR elements, like cellular telomeres, are essential for viral genome stability and propagation. We review the structure and function of viral repeat elements and discuss how they may share telomere-like structures and genome protection functions. We consider how viral infections modulate telomere regulatory factors for viral repurposing and can alter normal host telomere structure and chromosome stability. Understanding the common strategies of viral and cellular genome maintenance may provide new insights into viral–host interactions and the mechanisms driving genetic instability in cancer. PMID:23293769

  6. Television Watching and Telomere Length Among Adults in Southwest China.

    Science.gov (United States)

    Xue, Hong-Mei; Liu, Qian-Qian; Tian, Guo; Quan, Li-Ming; Zhao, Yong; Cheng, Guo

    2017-09-01

    To explore the independent associations of sedentary behavior and physical activity with telomere length among Chinese adults. Data on total time of sedentary behavior, screen-based sedentary behavior (including television watching and computer or phone use), moderate to vigorous physical activity, and dietary intake of 518 adults in Chengdu, Guizhou, and Xiamen in China (54.25% women) aged 20 to 70 years were obtained between 2013 and 2015 through questionnaires. Height, weight, and waist circumference were measured to calculate body mass index and percentage of body fat. Telomere length was measured through Southern blot technique. Television watching was inversely related to adjusted telomere length (-71.75 base pair; SE = 34.40; P  = .04). Furthermore, a similar trend between telomere length and television watching was found in the group aged 20 to 40 years after adjusting for all covariates. Adults aged 20 to 40 years in the highest tertile of daily time spent on watching television had 4.0% shorter telomere length than adults in the lowest tertile (P = .03). Although the association is modest, television watching is inversely related to telomere length among Chinese adults, warranting further investigation in large prospective studies.

  7. Cardiac telomere length in heart development, function, and disease.

    Science.gov (United States)

    Booth, S A; Charchar, F J

    2017-07-01

    Telomeres are repetitive nucleoprotein structures at chromosome ends, and a decrease in the number of these repeats, known as a reduction in telomere length (TL), triggers cellular senescence and apoptosis. Heart disease, the worldwide leading cause of death, often results from the loss of cardiac cells, which could be explained by decreases in TL. Due to the cell-specific regulation of TL, this review focuses on studies that have measured telomeres in heart cells and critically assesses the relationship between cardiac TL and heart function. There are several lines of evidence that have identified rapid changes in cardiac TL during the onset and progression of heart disease as well as at critical stages of development. There are also many factors, such as the loss of telomeric proteins, oxidative stress, and hypoxia, that decrease cardiac TL and heart function. In contrast, antioxidants, calorie restriction, and exercise can prevent both cardiac telomere attrition and the progression of heart disease. TL in the heart is also indicative of proliferative potential and could facilitate the identification of cells suitable for cardiac rejuvenation. Although these findings highlight the involvement of TL in heart function, there are important questions regarding the validity of animal models, as well as several confounding factors, that need to be considered when interpreting results and planning future research. With these in mind, elucidating the telomeric mechanisms involved in heart development and the transition to disease holds promise to prevent cardiac dysfunction and potentiate regeneration after injury. Copyright © 2017 the American Physiological Society.

  8. Rolle der Helikase RTEL1 in DNA-Reparatur, Rekombination sowie in der Telomerstabilität in Arabidopsis thaliana

    OpenAIRE

    Recker, Julia

    2014-01-01

    In Arabidopsis thaliana, the DNA helicase RTEL1 plays multiple roles in preserving genome stability. RTEL1 suppresses homologous recombination and is involved in interstrand and intrastrand DNA cross-link repair. RTEL1 contributes to telomere homeostasis. The concurrent loss of RTEL1 and the telomerase TERT leads to rapid, severe telomere shortening, which occurs much more rapidly than it does in the single-mutant line tert, resulting in developmental arrest after four generations.

  9. The roles of WRN and BLM RecQ helicases in the Alternative Lengthening of Telomeres.

    Science.gov (United States)

    Mendez-Bermudez, Aaron; Hidalgo-Bravo, Alberto; Cotton, Victoria E; Gravani, Athanasia; Jeyapalan, Jennie N; Royle, Nicola J

    2012-11-01

    Approximately 10% of all cancers, but a higher proportion of sarcomas, use the recombination-based alternative lengthening of telomeres (ALT) to maintain telomeres. Two RecQ helicase genes, BLM and WRN, play important roles in homologous recombination repair and they have been implicated in telomeric recombination activity, but their precise roles in ALT are unclear. Using analysis of sequence variation present in human telomeres, we found that a WRN- ALT+ cell line lacks the class of complex telomere mutations attributed to inter-telomeric recombination in other ALT+ cell lines. This suggests that WRN facilitates inter-telomeric recombination when there are sequence differences between the donor and recipient molecules or that sister-telomere interactions are suppressed in the presence of WRN and this promotes inter-telomeric recombination. Depleting BLM in the WRN- ALT+ cell line increased the mutation frequency at telomeres and at the MS32 minisatellite, which is a marker of ALT. The absence of complex telomere mutations persisted in BLM-depleted clones, and there was a clear increase in sequence homogenization across the telomere and MS32 repeat arrays. These data indicate that BLM suppresses unequal sister chromatid interactions that result in excessive homogenization at MS32 and at telomeres in ALT+ cells.

  10. Segregating YKU80 and TLC1 alleles underlying natural variation in telomere properties in wild yeast.

    Directory of Open Access Journals (Sweden)

    Gianni Liti

    2009-09-01

    Full Text Available In yeast, as in humans, telomere length varies among individuals and is controlled by multiple loci. In a quest to define the extent of variation in telomere length, we screened 112 wild-type Saccharomyces sensu stricto isolates. We found extensive telomere length variation in S. paradoxus isolates. This phenotype correlated with their geographic origin: European strains were observed to have extremely short telomeres (400 bp. Insertions of a URA3 gene near telomeres allowed accurate analysis of individual telomere lengths and telomere position effect (TPE. Crossing the American and European strains resulted in F1 spores with a continuum of telomere lengths consistent with what would be predicted if many quantitative trait loci (QTLs were involved in length maintenance. Variation in TPE is similarly quantitative but only weakly correlated with telomere length. Genotyping F1 segregants indicated several QTLs associated with telomere length and silencing variation. These QTLs include likely candidate genes but also map to regions where there are no known genes involved in telomeric properties. We detected transgressive segregation for both phenotypes. We validated by reciprocal hemizygosity that YKU80 and TLC1 are telomere-length QTLs in the two S. paradoxus subpopulations. Furthermore, we propose that sequence divergence within the Ku heterodimer generates negative epistasis within one of the allelic combinations (American-YKU70 and European-YKU80 resulting in very short telomeres.

  11. Segregating YKU80 and TLC1 alleles underlying natural variation in telomere properties in wild yeast.

    Science.gov (United States)

    Liti, Gianni; Haricharan, Svasti; Cubillos, Francisco A; Tierney, Anna L; Sharp, Sarah; Bertuch, Alison A; Parts, Leopold; Bailes, Elizabeth; Louis, Edward J

    2009-09-01

    In yeast, as in humans, telomere length varies among individuals and is controlled by multiple loci. In a quest to define the extent of variation in telomere length, we screened 112 wild-type Saccharomyces sensu stricto isolates. We found extensive telomere length variation in S. paradoxus isolates. This phenotype correlated with their geographic origin: European strains were observed to have extremely short telomeres (400 bp). Insertions of a URA3 gene near telomeres allowed accurate analysis of individual telomere lengths and telomere position effect (TPE). Crossing the American and European strains resulted in F1 spores with a continuum of telomere lengths consistent with what would be predicted if many quantitative trait loci (QTLs) were involved in length maintenance. Variation in TPE is similarly quantitative but only weakly correlated with telomere length. Genotyping F1 segregants indicated several QTLs associated with telomere length and silencing variation. These QTLs include likely candidate genes but also map to regions where there are no known genes involved in telomeric properties. We detected transgressive segregation for both phenotypes. We validated by reciprocal hemizygosity that YKU80 and TLC1 are telomere-length QTLs in the two S. paradoxus subpopulations. Furthermore, we propose that sequence divergence within the Ku heterodimer generates negative epistasis within one of the allelic combinations (American-YKU70 and European-YKU80) resulting in very short telomeres.

  12. Mouse CCDC79 (TERB1) is a meiosis-specific telomere associated protein.

    Science.gov (United States)

    Daniel, Katrin; Tränkner, Daniel; Wojtasz, Lukasz; Shibuya, Hiroki; Watanabe, Yoshinori; Alsheimer, Manfred; Tóth, Attila

    2014-05-22

    Telomeres have crucial meiosis-specific roles in the orderly reduction of chromosome numbers and in ensuring the integrity of the genome during meiosis. One such role is the attachment of telomeres to trans-nuclear envelope protein complexes that connect telomeres to motor proteins in the cytoplasm. These trans-nuclear envelope connections between telomeres and cytoplasmic motor proteins permit the active movement of telomeres and chromosomes during the first meiotic prophase. Movements of chromosomes/telomeres facilitate the meiotic recombination process, and allow high fidelity pairing of homologous chromosomes. Pairing of homologous chromosomes is a prerequisite for their correct segregation during the first meiotic division. Although inner-nuclear envelope proteins, such as SUN1 and potentially SUN2, are known to bind and recruit meiotic telomeres, these proteins are not meiosis-specific, therefore cannot solely account for telomere-nuclear envelope attachment and/or for other meiosis-specific characteristics of telomeres in mammals. We identify CCDC79, alternatively named TERB1, as a meiosis-specific protein that localizes to telomeres from leptotene to diplotene stages of the first meiotic prophase. CCDC79 and SUN1 associate with telomeres almost concurrently at the onset of prophase, indicating a possible role for CCDC79 in telomere-nuclear envelope interactions and/or telomere movements. Consistent with this scenario, CCDC79 is missing from most telomeres that fail to connect to SUN1 protein in spermatocytes lacking the meiosis-specific cohesin SMC1B. SMC1B-deficient spermatocytes display both reduced efficiency in telomere-nuclear envelope attachment and reduced stability of telomeres specifically during meiotic prophase. Importantly, CCDC79 associates with telomeres in SUN1-deficient spermatocytes, which strongly indicates that localization of CCDC79 to telomeres does not require telomere-nuclear envelope attachment. CCDC79 is a meiosis-specific telomere

  13. Status of perturbative QCD

    International Nuclear Information System (INIS)

    Collins, J.C.

    1985-01-01

    Progress in quantum chromodynamics in the past year is reviewed in these specific areas: proof of factorization for hadron-hadron collisions, fast calculation of higher order graphs, perturbative Monte Carlo calculations for hadron-hadron scattering, applicability of perturbative methods to heavy quark production, and understanding of the small-x problem. 22 refs

  14. Relative Leukocyte Telomere Length, Hematological Parameters and Anemia - Data from the Berlin Aging Study II (BASE-II).

    Science.gov (United States)

    Meyer, Antje; Salewsky, Bastian; Buchmann, Nikolaus; Steinhagen-Thiessen, Elisabeth; Demuth, Ilja

    2016-01-01

    The length of the chromosome ends, telomeres, is widely accepted as a biomarker of aging. However, the dynamic of the relationship between telomere length and hematopoietic parameters in the normal aging process, which is of particular interest with respect to age-related anemia, is not well understood. We have analyzed the relationship between relative leukocyte telomere length (rLTL) and several hematological parameters in the older group of the Berlin Aging Study II (BASE-II) participants. This paper also compares rLTL between both BASE-II age groups (22-37 and 60-83 years). Genomic DNA was extracted from peripheral blood leukocytes of BASE-II participants and used to determine rLTL by a quantitative PCR protocol. Standard methods were used to determine blood parameters, and the WHO criteria were used to identify anemic participants. Telomere length data were available for 444 younger participants (28.4 ± 3.1 years old; 52% women) and 1,460 older participants (68.2 ± 3.7 years old; 49.4% women). rLTL was significantly shorter in BASE-II participants of the older group (p = 3.7 × 10-12) and in women (p = 4.2 × 10-31). rLTL of older men exhibited a statistically significant, positive partial correlation with mean corpuscular hemoglobin (MCH; p = 0.012) and MCH concentration (p = 0.002). While these correlations were only observed in men, the rLTL of older women was negatively correlated with the number of thrombocytes (p = 0.015) in the same type of analysis. Among all older participants, 6% met the criteria to be categorized as 'anemic'; however, there was no association between anemia and rLTL. In the present study, we have detected isolated correlations between rLTL and hematological parameters; however, in all cases, rLTL explained only a small part of the variation of the analyzed parameters. In disagreement with some other studies showing similar data, we interpret the association between rLTL and some of the hematological parameters studied here to be

  15. Perturbative and constructive renormalization

    International Nuclear Information System (INIS)

    Veiga, P.A. Faria da

    2000-01-01

    These notes are a survey of the material treated in a series of lectures delivered at the X Summer School Jorge Andre Swieca. They are concerned with renormalization in Quantum Field Theories. At the level of perturbation series, we review classical results as Feynman graphs, ultraviolet and infrared divergences of Feynman integrals. Weinberg's theorem and Hepp's theorem, the renormalization group and the Callan-Symanzik equation, the large order behavior and the divergence of most perturbation series. Out of the perturbative regime, as an example of a constructive method, we review Borel summability and point out how it is possible to circumvent the perturbation diseases. These lectures are a preparation for the joint course given by professor V. Rivasseau at the same school, where more sophisticated non-perturbative analytical methods based on rigorous renormalization group techniques are presented, aiming at furthering our understanding about the subject and bringing field theoretical models to a satisfactory mathematical level. (author)

  16. Telomere dynamics in human mesenchymal stem cells after exposure to acute oxidative stress

    DEFF Research Database (Denmark)

    Harbo, M.; Koelvraa, S.; Serakinci, N.

    2012-01-01

    mesenchymal stem cells, either primary or hTERT immortalized, were exposed to sub-lethal doses of hydrogen peroxide, and the short term effect on telomere dynamics was monitored by Universal STELA and TRF measurements. Both telomere measures were then correlated with the percentage of senescent cells......A gradual shortening of telomeres due to replication can be measured using the standard telomere restriction fragments (TRF) assay and other methods by measuring the mean length of all the telomeres in a cell. In contrast, stress-induced telomere shortening, which is believed to be just...... estimated by senescence-associated beta-galactosidase staining. The exposure to acute oxidative stress resulted in an increased number of ultra-short telomeres, which correlated strongly with the percentage of senescent cells, whereas a correlation between mean telomere length and the percentage...

  17. The distribution pattern of critically short telomeres in human osteoarthritic knees

    DEFF Research Database (Denmark)

    Harbo, Maria; Bendix, Laila; Bay-Jensen, Anne Christine

    2012-01-01

    ABSTRACT: INTRODUCTION: Telomere shortening is associated with a number of common age-related diseases. A role of telomere shortening in osteoarthritis (OA) has been suggested, mainly based on the assessment of mean telomere length in ex vivo expanded chondrocytes. We addressed this role directly...... in vivo by using a newly developed assay, which measures specifically the load of ultra-short single telomeres (below 1,500 base pairs), that is, the telomere subpopulation believed to promote cellular senescence. METHODS: Samples were obtained from human OA knees at two distances from the central lesion...... site. Each sample was split into three: one was used for quantification of ultra-short single telomeres through the Universal single telomere length assay (STELA), one for histological Mankin grading of OA, and one for mean telomere length measurement through quantitative fluorescence in situ...

  18. Acrolein-Exposed Normal Human Lung Fibroblasts in Vitro: Cellular Senescence, Enhanced Telomere Erosion, and Degradation of Werner’s Syndrome Protein

    Science.gov (United States)

    Jang, Jun-Ho; Bruse, Shannon; Huneidi, Salam; Schrader, Ronald M.; Monick, Martha M.; Lin, Yong; Carter, A. Brent; Klingelhutz, Aloysius J.

    2014-01-01

    Background: Acrolein is a ubiquitous environmental hazard to human health. Acrolein has been reported to activate the DNA damage response and induce apoptosis. However, little is known about the effects of acrolein on cellular senescence. Objectives: We examined whether acrolein induces cellular senescence in cultured normal human lung fibroblasts (NHLF). Methods: We cultured NHLF in the presence or absence of acrolein and determined the effects of acrolein on cell proliferative capacity, senescence-associated β-galactosidase activity, the known senescence-inducing pathways (e.g., p53, p21), and telomere length. Results: We found that acrolein induced cellular senescence by increasing both p53 and p21. The knockdown of p53 mediated by small interfering RNA (siRNA) attenuated acrolein-induced cellular senescence. Acrolein decreased Werner’s syndrome protein (WRN), a member of the RecQ helicase family involved in DNA repair and telomere maintenance. Acrolein-induced down-regulation of WRN protein was rescued by p53 knockdown or proteasome inhibition. Finally, we found that acrolein accelerated p53-mediated telomere shortening. Conclusions: These results suggest that acrolein induces p53-mediated cellular senescence accompanied by enhanced telomere attrition and WRN protein down-regulation. Citation: Jang JH, Bruse S, Huneidi S, Schrader RM, Monick MM, Lin Y, Carter AB, Klingelhutz AJ, Nyunoya T. 2014. Acrolein-exposed normal human lung fibroblasts in vitro: cellular senescence, enhanced telomere erosion, and degradation of Werner’s syndrome protein. Environ Health Perspect 122:955–962; http://dx.doi.org/10.1289/ehp.1306911 PMID:24747221

  19. PIF1 disruption or NBS1 hypomorphism does not affect chromosome healing or fusion resulting from double-strand breaks near telomeres in murine embryonic stem cells.

    Science.gov (United States)

    Reynolds, Gloria E; Gao, Qing; Miller, Douglas; Snow, Bryan E; Harrington, Lea A; Murnane, John P

    2011-11-10

    Telomerase serves to maintain telomeric repeat sequences at the ends of chromosomes. However, telomerase can also add telomeric repeat sequences at DNA double-strand breaks (DSBs), a process called chromosome healing. Here, we employed a method of inducing DSBs near telomeres to query the role of two proteins, PIF1 and NBS1, in chromosome healing in mammalian cells. PIF1 was investigated because the PIF1 homolog in Saccharomyces cerevisiae inhibits chromosome healing, as shown by a 1000-fold increase in chromosome in PIF1-deficient cells. NBS1 was investigated because the functional homolog of NBS1 in S. cerevisiae, Xrs2, is part of the Mre11/Rad50/Xrs2 complex that is required for chromosome healing due to its role in the processing of DSBs and recruitment of telomerase. We found that disruption of mPif1 had no detectable effect on the frequency of chromosome healing at DSBs near telomeres in murine embryonic stem cells. Moreover, the Nbs1(ΔB) hypomorph, which is defective in the processing of DSBs, also had no detectable effect on the frequency of chromosome healing, DNA degradation, or gross chromosome rearrangements (GCRs) that result from telomeric DSBs. Although we cannot rule out small changes in chromosome healing using this system, it is clear from our results that knockout of PIF1 or the Nbs1(ΔB) hypomorph does not result in large differences in chromosome healing in murine cells. These results represent the first genetic assessment of the role of these proteins in chromosome healing in mammals, and suggest that murine cells have evolved mechanisms to ensure the functional redundancy of Pif1 or Nbs1 in the regulation of chromosome healing. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Nuclear alpha spectrin: Critical roles in DNA interstrand cross-link repair and genomic stability

    OpenAIRE

    Lambert, Muriel W

    2016-01-01

    Non-erythroid alpha spectrin (?IISp) is a structural protein which we have shown is present in the nucleus of human cells. It interacts with a number of nuclear proteins such as actin, lamin, emerin, chromatin remodeling factors, and DNA repair proteins. ?IISp?s interaction with DNA repair proteins has been extensively studied. We have demonstrated that nuclear ?IISp is critical in DNA interstrand cross-link (ICL) repair in S phase, in both genomic (non-telomeric) and telomeric DNA, and in ma...

  1. Genetic variants associated with longer telomere length are associated with increased lung cancer risk among never-smoking women in Asia : a report from the female lung cancer consortium in Asia

    NARCIS (Netherlands)

    Machiela, Mitchell J; Hsiung, Chao Agnes; Shu, Xiao-Ou; Seow, Wei Jie; Wang, Zhaoming; Matsuo, Keitaro; Hong, Yun-Chul; Seow, Adeline; Wu, Chen; Hosgood, H Dean; Chen, Kexin; Wang, Jiu-Cun; Wen, Wanqing; Cawthon, Richard; Chatterjee, Nilanjan; Hu, Wei; Caporaso, Neil E; Park, Jae Yong; Chen, Chien-Jen; Kim, Yeul Hong; Kim, Young Tae; Landi, Maria Teresa; Shen, Hongbing; Lawrence, Charles; Burdett, Laurie; Yeager, Meredith; Chang, I-Shou; Mitsudomi, Tetsuya; Kim, Hee Nam; Chang, Gee-Chen; Bassig, Bryan A; Tucker, Margaret; Wei, Fusheng; Yin, Zhihua; An, She-Juan; Qian, Biyun; Lee, Victor Ho Fun; Lu, Daru; Liu, Jianjun; Jeon, Hyo-Sung; Hsiao, Chin-Fu; Sung, Jae Sook; Kim, Jin Hee; Gao, Yu-Tang; Tsai, Ying-Huang; Jung, Yoo Jin; Guo, Huan; Hu, Zhibin; Hutchinson, Amy; Wang, Wen-Chang; Klein, Robert J; Chung, Charles C; Oh, In-Jae; Chen, Kuan-Yu; Berndt, Sonja I; Wu, Wei; Chang, Jiang; Zhang, Xu-Chao; Huang, Ming-Shyan; Zheng, Hong; Wang, Junwen; Zhao, Xueying; Li, Yuqing; Choi, Jin Eun; Su, Wu-Chou; Park, Kyong Hwa; Sung, Sook Whan; Chen, Yuh-Min; Liu, Li; Kang, Chang Hyun; Hu, Lingmin; Chen, Chung-Hsing; Pao, William; Kim, Young-Chul; Yang, Tsung-Ying; Xu, Jun; Guan, Peng; Tan, Wen; Su, Jian; Wang, Chih-Liang; Li, Haixin; Sihoe, Alan Dart Loon; Zhao, Zhenhong; Chen, Ying; Choi, Yi Young; Hung, Jen-Yu; Kim, Jun Suk; Yoon, Ho-Il; Cai, Qiuyin; Lin, Chien-Chung; Park, In Kyu; Xu, Ping; Dong, Jing; Kim, Christopher; He, Qincheng; Perng, Reury-Perng; Kohno, Takashi; Kweon, Sun-Seog; Chen, Chih-Yi; Vermeulen, Roel C H; Wu, Junjie; Lim, Wei-Yen; Chen, Kun-Chieh; Chow, Wong-Ho; Ji, Bu-Tian; Chan, John K C; Chu, Minjie; Li, Yao-Jen; Yokota, Jun; Li, Jihua; Chen, Hongyan; Xiang, Yong-Bing; Yu, Chong-Jen; Kunitoh, Hideo; Wu, Guoping; Jin, Li; Lo, Yen-Li; Shiraishi, Kouya; Chen, Ying-Hsiang; Lin, Hsien-Chih; Wu, Tangchun; Wong, Maria Pik; Wu, Yi-Long; Yang, Pan-Chyr; Zhou, Baosen; Shin, Min-Ho; Fraumeni, Joseph F; Zheng, Wei; Lin, Dongxin; Chanock, Stephen J; Rothman, Nathaniel; Lan, Qing

    2015-01-01

    Recent evidence from several relatively small nested case-control studies in prospective cohorts shows an association between longer telomere length measured phenotypically in peripheral white blood cell (WBC) DNA and increased lung cancer risk. We sought to further explore this relationship by

  2. A computational model for telomere-dependent cell-replicative aging.

    Science.gov (United States)

    Portugal, R D; Land, M G P; Svaiter, B F

    2008-01-01

    Telomere shortening provides a molecular basis for the Hayflick limit. Recent data suggest that telomere shortening also influence mitotic rate. We propose a stochastic growth model of this phenomena, assuming that cell division in each time interval is a random process which probability decreases linearly with telomere shortening. Computer simulations of the proposed stochastic telomere-regulated model provides good approximation of the qualitative growth of cultured human mesenchymal stem cells.

  3. Large-scale parent–child comparison confirms a strong paternal influence on telomere length

    OpenAIRE

    Nordfjäll, Katarina; Svenson, Ulrika; Norrback, Karl-Fredrik; Adolfsson, Rolf; Roos, Göran

    2009-01-01

    Telomere length is documented to have a hereditary component, and both paternal and X-linked inheritance have been proposed. We investigated blood cell telomere length in 962 individuals with an age range between 0 and 102 years. Telomere length correlations were analyzed between parent–child pairs in different age groups and between grandparent–grandchild pairs. A highly significant correlation between the father's and the child's telomere length was observed (r=0.454, P

  4. Tying it all together: telomeres, sexual size dimorphism and the gender gap in life expectancy.

    Science.gov (United States)

    Stindl, Reinhard

    2004-01-01

    The classic explanation that women outlive men solely due to hormonal and lifestyle differences, does not withstand a critical analysis. In developed countries, the average gap in life expectancy between the sexes is 7 years. It has widened over the last decades, despite the trend of women copying the 'unhealthy' lifestyle of men. Estrogen levels in postmenopausal women are virtually identical to estrogen levels in males and can hardly explain the discrepancy. Furthermore, testosterone got its bad reputation from one study on mentally retarded men, which has to be interpreted with caution. However, sexual size dimorphism with men being the larger sex in conjunction with the limited replication potential of human somatic cells might account for higher mortality rates in males, especially at old age. The hypothesis, as presented here, is based on the well-known concept of a cellular mitotic clock, which was discovered by Leonard Hayflick almost half a century ago. The underlying counting mechanism, namely the gradual erosion of chromosome ends (telomeres) due to the end replication problem of linear DNA molecules, was first described by Alexey Olovnikov in 1971 and with minor modifications has become a widely accepted paradigm. In a recent Lancet study, an inverse correlation between mean telomere length and mortality in people has been found. In this and two other studies, it was confirmed that males do have shorter telomeres than females at the same age. This is almost certainly a consequence of men being usually taller than women, although nobody has done an investigation yet. Clearly, a larger body requires more cell doublings, especially due to the ongoing regeneration of tissues over a lifetime. Accordingly, the replicative history of male cells might be longer than that of female cells, resulting in the exhaustion of the regeneration potential and the early onset of age-associated diseases predominantly in large-bodied males. Inherited telomere length

  5. Leukocyte telomere length and mortality among U.S. adults: Effect modification by physical activity behaviour.

    Science.gov (United States)

    Loprinzi, Paul D; Loenneke, Jeremy P

    2018-01-01

    The purpose of this study was to examine the association between leukocyte telomere length (LTL) and mortality (outcome variable), with consideration by physical activity behaviour. Data from the 1999-2002 National Health and Nutrition Examination Survey were employed (N = 6,611; 20-85 yrs), with follow-up mortality assessment through 31 December 2006. DNA was extracted from whole blood to assess LTL via quantitative polymerase chain reaction. Compared to those in the first LTL tertile, the adjusted hazard ratio for all-cause mortality for those in the 2 nd and 3 rd LTL tertiles, respectively, was 0.82 (95% CI: 0.60-1.12; P = .22) and 0.76 (95% CI: 0.50-1.14; P = .18). However, after adjustments, LTL tertile 3 (vs. 1) was associated with all-cause mortality (HR = 0.37; 95% CI: 0.14-0.93; P = .03) for those who engaged in moderate-intensity exercise. Similarly, LTL was associated with CVD-specific mortality for those who engaged in moderate-intensity exercise (HR = 0.17; 95% CI: 0.04-0.73; P = .02). Longer telomeres are associated with increased survival, particularly among men and those who are active, underscoring the importance of promotion of physical activity behaviour.

  6. Vanishing honey bees: Is the dying of adult worker bees a consequence of short telomeres and premature aging?

    Science.gov (United States)

    Stindl, Reinhard; Stindl, Wolfgang

    2010-10-01

    Einstein is often quoted to have said that without the bee, mankind would have but 4years to live. It is highly unlikely that he made this comment, which was even mentioned in a Lancet article on honey bees. However, the current vanishing of the bees can have serious consequences for human health, because 35% of the human diet is thought to benefit from pollination. Colony collapse disorder (CCD) in honey bees is characterized by the rapid decline of the adult bee population, leaving the brood and the queen poorly or completely unattended, with no dead bodies in or around the hive. A large study found no evidence that the presence or amount of any individual pesticide or infectious agent occurred more frequently or abundantly in CCD-affected colonies. The growing consensus is that honey bees are suffering from comprised immune systems, which allow various infectious pathogens to invade. The question remains, what causes immunosuppression in many colonies of Apis mellifera in North America and Europe? Telomeres are protective DNA structures located at eukaryotic chromosome tips that shorten in the somatic tissues of animals with age. Lifelong tissue regeneration takes place in Apis mellifera, and worker bees have been shown to senesce. In humans, a vast amount of literature has accumulated on exhausted telomere reserves causing impaired tissue regeneration and age-associated diseases, specifically cancer and immunosuppression. Therefore, we propose a new causative mechanism for the vanishing of the bees: critically short telomeres in long-lived winter bees. We term this the telomere premature aging syndrome. Copyright 2010 Elsevier Ltd. All rights reserved.

  7. Translating Measures of Biological Aging to Test Effectiveness of Geroprotective Interventions: What Can We Learn from Research on Telomeres?

    Directory of Open Access Journals (Sweden)

    Waylon J. Hastings

    2017-11-01

    Full Text Available Intervention studies in animals suggest molecular changes underlying age-related disease and disability can be slowed or reversed. To speed translation of these so-called “geroprotective” therapies to prevent age-related disease and disability in humans, biomarkers are needed that can track changes in the rate of human aging over the course of intervention trials. Algorithm methods that measure biological processes of aging from combinations of DNA methylation marks or clinical biomarkers show promise. To identify next steps for establishing utility of these algorithm-based measures of biological aging for geroprotector trials, we considered the history a candidate biomarker of aging that has received substantial research attention, telomere length. Although telomere length possesses compelling biology to recommend it as a biomarker of aging, mixed research findings have impeded clinical and epidemiologic translation. Strengths of telomeres that should be established for algorithm biomarkers of aging are correlation with chronological age across the lifespan, prediction of disease, disability, and early death, and responsiveness to risk and protective exposures. Key challenges in telomere research that algorithm biomarkers of aging must address are measurement precision and reliability, establishing links between longitudinal rates of change across repeated measurements and aging outcomes, and clarity over whether the biomarker is a causal mechanism of aging. These strengths and challenges suggest a research agenda to advance translation of algorithm-based aging biomarkers: establish validity in young-adult and midlife individuals; test responsiveness to exposures that shorten or extend healthy lifespan; and conduct repeated-measures longitudinal studies to test differential rates of change.

  8. A different approach to telomere analysis with ddPRINS in chronic lymphocytic leukemia

    DEFF Research Database (Denmark)

    Palanduz, Sukru; Serakinci, Nedime; Cefle, Kivanc

    2006-01-01

    in patients with B-cell CLL in a comparison with the control group by using ddPRINS technique. Twenty patients with CLL and four healthy donors as a control group were included. We found short telomeres and no detectable telomeric repeats at the sites of chromosome fusion. We hypothesise that the telomeric...

  9. Resolution of telomere associations by TRF1 cleavage in mouse embryonic stem cells

    NARCIS (Netherlands)

    Lisaingo, Kathleen; Uringa, Evert-Jan; Lansdorp, Peter M.

    2014-01-01

    Telomere associations have been observed during key cellular processes such as mitosis, meiosis, and carcinogenesis and must be resolved before cell division to prevent genome instability. Here we establish that telomeric repeat-binding factor 1 (TRF1), a core component of the telomere protein

  10. Thermodynamic fingerprints of ligand binding to human telomeric G-quadruplexes.

    Science.gov (United States)

    Bončina, Matjaž; Podlipnik, Črtomir; Piantanida, Ivo; Eilmes, Julita; Teulade-Fichou, Marie-Paule; Vesnaver, Gorazd; Lah, Jurij

    2015-12-02

    Thermodynamic studies of ligand binding to human telomere (ht) DNA quadruplexes, as a rule, neglect the involvement of various ht-DNA conformations in the binding process. Therefore, the thermodynamic driving forces and the mechanisms of ht-DNA G-quadruplex-ligand recognition remain poorly understood. In this work we characterize thermodynamically and structurally binding of netropsin (Net), dibenzotetraaza[14]annulene derivatives (DP77, DP78), cationic porphyrin (TMPyP4) and two bisquinolinium ligands (Phen-DC3, 360A-Br) to the ht-DNA fragment (Tel22) AGGG(TTAGGG)3 using isothermal titration calorimetry, CD and fluorescence spectroscopy, gel electrophoresis and molecular modeling. By global thermodynamic analysis of experimental data we show that the driving forces characterized by contributions of specific interactions, changes in solvation and conformation differ significantly for binding of ligands with low quadruplex selectivity over duplexes (Net, DP77, DP78, TMPyP4; KTel22 ≈ KdsDNA). These contributions are in accordance with the observed structural features (changes) and suggest that upon binding Net, DP77, DP78 and TMPyP4 select hybrid-1 and/or hybrid-2 conformation while Phen-DC3 and 360A-Br induce the transition of hybrid-1 and hybrid-2 to the structure with characteristics of antiparallel or hybrid-3 type conformation. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  11. Therapeutic opportunities: Telomere maintenance in inducible pluripotent stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Gourronc, Francoise A. [Department of Microbiology, University of Iowa (United States); Klingelhutz, Aloysius J., E-mail: al-klingelhutz@uiowa.edu [Department of Microbiology, University of Iowa (United States)

    2012-02-01

    It has been demonstrated that exogenous expression of a combination of transcription factors can reprogram differentiated cells such as fibroblasts and keratinocytes into what have been termed induced pluripotent stem (iPS) cells. These iPS cells are capable of differentiating into all the tissue lineages when placed in the right environment and, in the case of mouse cells, can generate chimeric mice and be transmitted through the germline. Safer and more efficient methods of reprogramming are rapidly being developed. Clearly, iPS cells present a number of exciting possibilities, including disease modeling and therapy. A major question is whether the nuclei of iPS cells are truly rejuvenated or whether they might retain some of the marks of aging from the cells from which they were derived. One measure of cellular aging is the telomere. In this regard, recent studies have demonstrated that telomeres in iPS cells may be rejuvenated. They are not only elongated by reactivated telomerase but they are also epigenetically modified to be similar but not identical to embryonic stem cells. Upon differentiation, the derivative cells turn down telomerase, the telomeres begin to shorten again, and the telomeres and the genome are returned to an epigenetic state that is similar to normal differentiated somatic cells. While these preliminary telomere findings are promising, the overall genomic integrity of reprogrammed cells may still be problematic and further studies are needed to examine the safety and feasibility of using iPS cells in regenerative medicine applications.

  12. Therapeutic opportunities: Telomere maintenance in inducible pluripotent stem cells

    International Nuclear Information System (INIS)

    Gourronc, Francoise A.; Klingelhutz, Aloysius J.

    2012-01-01

    It has been demonstrated that exogenous expression of a combination of transcription factors can reprogram differentiated cells such as fibroblasts and keratinocytes into what have been termed induced pluripotent stem (iPS) cells. These iPS cells are capable of differentiating into all the tissue lineages when placed in the right environment and, in the case of mouse cells, can generate chimeric mice and be transmitted through the germline. Safer and more efficient methods of reprogramming are rapidly being developed. Clearly, iPS cells present a number of exciting possibilities, including disease modeling and therapy. A major question is whether the nuclei of iPS cells are truly rejuvenated or whether they might retain some of the marks of aging from the cells from which they were derived. One measure of cellular aging is the telomere. In this regard, recent studies have demonstrated that telomeres in iPS cells may be rejuvenated. They are not only elongated by reactivated telomerase but they are also epigenetically modified to be similar but not identical to embryonic stem cells. Upon differentiation, the derivative cells turn down telomerase, the telomeres begin to shorten again, and the telomeres and the genome are returned to an epigenetic state that is similar to normal differentiated somatic cells. While these preliminary telomere findings are promising, the overall genomic integrity of reprogrammed cells may still be problematic and further studies are needed to examine the safety and feasibility of using iPS cells in regenerative medicine applications.

  13. Investigation of telomere length and psychological stress in rape victims.

    Science.gov (United States)

    Malan, Stefanie; Hemmings, Sian; Kidd, Martin; Martin, Lindi; Seedat, Soraya

    2011-12-21

    Women are at an increased risk of depression and other mental health problems following rape. Various etiological factors for depression, including predisposing genetic factors, have been identified. Telomeres are repetitive nucleoprotein structures located at chromosomal ends that protect them from premature degradation. Telomeres reduce in length with each cell division, resulting in cellular senescence and apoptosis. Relative quantification of telomeric repeats using qPCR was performed to investigate whether shorter relative leukocyte telomere length (LTL) in a cohort of 64 rape victims was associated with resilience, the development of rape trauma-related major depressive disorder (MDD) or the development of posttraumatic stress disorder (PTSD) after 3 months. Out of the 64 participants, 23 participants were diagnosed with MDD at baseline and 31 after 3 months. Nine participants were diagnosed with PTSD (MDD and PTSD specifically related to the trauma). No significant associations were observed between relative LTL and resilience or the development of MDD at either baseline or after 3 months in this cohort. However, a marginally significant association was evident between relative LTL and PTSD status. The significant association between relative LTL and PTSD suggests that shorter relative LTL might have acted as a predisposing factor in the development of PTSD after a severely traumatic event. The results of this study indicate that telomere shortening may be an important marker of PTSD risk, with implications for early intervention and timely treatment, and as such warrant replication in a larger cohort. © 2011 Wiley Periodicals, Inc.

  14. Perturbative QCD and jets

    International Nuclear Information System (INIS)

    Mueller, A.H.

    1986-03-01

    A brief review of some of the recent progress in perturbative QCD is given (heavy quark production, small-x physics, minijets and related topics, classical simulations in high energy reactions, coherence and the string effect)

  15. Generalized chiral perturbation theory

    International Nuclear Information System (INIS)

    Knecht, M.; Stern, J.

    1994-01-01

    The Generalized Chiral Perturbation Theory enlarges the framework of the standard χPT (Chiral Perturbation Theory), relaxing certain assumptions which do not necessarily follow from QCD or from experiment, and which are crucial for the usual formulation of the low energy expansion. In this way, experimental tests of the foundations of the standard χPT become possible. Emphasis is put on physical aspects rather than on formal developments of GχPT. (author). 31 refs

  16. Test anxiety and telomere length: Academic stress in adolescents may not cause rapid telomere erosion.

    Science.gov (United States)

    Zou, Yaru; Leong, Waiian; Yao, Mingling; Hu, Xuefei; Lu, Sixiao; Zhu, Xiaowei; Chen, Lianxiang; Tong, Jianjing; Shi, Jingyi; Gilson, Eric; Ye, Jing; Lu, Yiming

    2017-02-14

    Academic stress (AS) is one of the most important health problems experienced by students, but no biomarker of the potential psychological or physical problems associated with AS has yet been identified. As several cross-sectional studies have shown that psychiatric conditions accelerate aging and shorten telomere length (TL), we explored whether AS affected TL.Between June 2014 and July 2014, we recruited 200 junior high school students with imminent final examinations for participation in this study. The students were divided into three subgroups (mild, moderate, and severe anxiety) using the Sarason Test Anxiety Scale (TAS). Saliva samples were collected for TL measurement via quantitative polymerase chain reaction (qPCR).Students from both a specialized and a general school suffered from anxiety (p > 0.05). A total 35% had severe anxiety (score: 26.09±3.87), 33% had moderate anxiety (16.98±2.64), and 32% had mild anxiety (7.89±1.92). The TAS values differed significantly (p 0.05): 1.14±0.46 for those with severe anxiety, 1.02±0.40 for those with moderate anxiety, and 1.12±0.45 for those with mild anxiety.Previous reports have found that AS is very common in Asian adolescents. We found no immediate telomere shortening in adolescents with AS. Longitudinal observations are required to determine if TL is affected by AS.

  17. Tired telomeres: Poor global sleep quality, perceived stress, and telomere length in immune cell subsets in obese men and women.

    Science.gov (United States)

    Prather, Aric A; Gurfein, Blake; Moran, Patricia; Daubenmier, Jennifer; Acree, Michael; Bacchetti, Peter; Sinclair, Elizabeth; Lin, Jue; Blackburn, Elizabeth; Hecht, Frederick M; Epel, Elissa S

    2015-07-01

    Poor sleep quality and short sleep duration are associated with increased incidence and progression of a number of chronic health conditions observed at greater frequency among the obese and those experiencing high levels of stress. Accelerated cellular aging, as indexed by telomere attrition in immune cells, is a plausible pathway linking sleep and disease risk. Prior studies linking sleep and telomere length are mixed. One factor may be reliance on leukocytes, which are composed of varied immune cell types, as the sole measure of telomere length. To better clarify these associations, we investigated the relationships of global sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), and diary-reported sleep duration with telomere length in different immune cell subsets, including granulocytes, peripheral blood mononuclear cells (PBMCs), CD8+ and CD4+ T lymphocytes, and B lymphocytes in a sample of 87 obese men and women (BMI mean=35.4, SD=3.6; 81.6% women; 62.8% Caucasian). Multiple linear regression analyses were performed adjusting for age, gender, race, education, BMI, sleep apnea risk, and perceived stress. Poorer PSQI global sleep quality was associated with statistically significantly shorter telomere length in lymphocytes but not granulocytes and in particular CD8+ T cells (b=-56.8 base pairs per one point increase in PSQI, SE=20.4, p=0.007) and CD4+ T cells (b=-37.2, SE=15.9, p=0.022). Among separate aspects of global sleep quality, low perceived sleep quality and decrements in daytime function were most related to shorter telomeres. In addition, perceived stress moderated the sleep-CD8+ telomere association. Poorer global sleep quality predicted shorter telomere length in CD8+ T cells among those with high perceived stress but not in low stress participants. These findings provide preliminary evidence that poorer global sleep quality is related to telomere length in several immune cell types, which may serve as a pathway linking sleep and

  18. Telomere length is longer in women with late maternal age

    DEFF Research Database (Denmark)

    Fagan, Erin; Sun, Fangui; Bae, Harold

    2017-01-01

    OBJECTIVE:: Maternal age at birth of last child has been associated with maternal longevity. The aim of this study was to determine whether older women with a history of late maternal age at last childbirth had a longer leukocyte telomere length than those with maternal age at last childbirth of 29...... died, but were at least 70 years old, were studied. Logistic regression models using generalized estimating equations were used to determine the association between tertiles of telomere length and maternal age at last childbirth, adjusting for covariates. RESULTS:: Age at birth of the last child...... in the first tertile. CONCLUSIONS:: These findings show an association between longer leukocyte telomere length and a later maternal age at birth of last child, suggesting that extended maternal age at last childbirth may be a marker for longevity....

  19. Telomere dynamics and cytogenetic changes in human hematologic neoplasias: a working hypothesis.

    Science.gov (United States)

    Ohyashiki, K; Ohyashiki, J H

    1997-03-01

    Chromosome termini, termed telomeres, provide important protection to avoid loss of master gene(s) that may exist at subtelomeric regions. Moreover, erosion of telomeres by cell division through end-replication problems resulted in telomeric-associated cytogenetic aberrations. To maintain a telomere length related to cell immortality, telomerase activity is upregulated in cancer cells, therefore, telomerase is considered to be a new marker of neoplasias. In this paper, we review and make suggestions regarding key aspects of telomere dynamics in both normal hematopoiesis and in malignant hematologic diseases.

  20. TRF2 Recruits RTEL1 to Telomeres in S Phase to Promote T-Loop Unwinding

    OpenAIRE

    Sarek, Grzegorz; Vannier, Jean-Baptiste; Panier, Stephanie; Petrini, John?H.J.; Boulton, Simon?J.

    2015-01-01

    Summary The helicase RTEL1 promotes t-loop unwinding and suppresses telomere fragility to maintain the integrity of vertebrate telomeres. An interaction between RTEL1 and PCNA is important to prevent telomere fragility, but how RTEL1 engages with the telomere to promote t-loop unwinding is unclear. Here, we establish that the shelterin protein TRF2 recruits RTEL1 to telomeres in S phase, which is required to?prevent catastrophic t-loop processing by structure-specific nucleases. We show that ...

  1. Gender and telomere length: Systematic review and meta-analysis☆

    Science.gov (United States)

    Gardner, Michael; Bann, David; Wiley, Laura; Cooper, Rachel; Hardy, Rebecca; Nitsch, Dorothea; Martin-Ruiz, Carmen; Shiels, Paul; Sayer, Avan Aihie; Barbieri, Michelangela; Bekaert, Sofie; Bischoff, Claus; Brooks-Wilson, Angela; Chen, Wei; Cooper, Cyrus; Christensen, Kaare; De Meyer, Tim; Deary, Ian; Der, Geoff; Roux, Ana Diez; Fitzpatrick, Annette; Hajat, Anjum; Halaschek-Wiener, Julius; Harris, Sarah; Hunt, Steven C.; Jagger, Carol; Jeon, Hyo-Sung; Kaplan, Robert; Kimura, Masayuki; Lansdorp, Peter; Li, Changyong; Maeda, Toyoki; Mangino, Massimo; Nawrot, Tim S.; Nilsson, Peter; Nordfjall, Katarina; Paolisso, Giuseppe; Ren, Fu; Riabowol, Karl; Robertson, Tony; Roos, Goran; Staessen, Jan A.; Spector, Tim; Tang, Nelson; Unryn, Brad; van der Harst, Pim; Woo, Jean; Xing, Chao; Yadegarfar, Mohammad E.; Park, Jae Yong; Young, Neal; Kuh, Diana; von Zglinicki, Thomas; Ben-Shlomo, Yoav

    2015-01-01

    Background It is widely believed that females have longer telomeres than males, although results from studies have been contradictory. Methods We carried out a systematic review and meta-analyses to test the hypothesis that in humans, females have longer telomeres than males and that this association becomes stronger with increasing age. Searches were conducted in EMBASE and MEDLINE (by November 2009) and additional datasets were obtained from study investigators. Eligible observational studies measured telomeres for both females and males of any age, had a minimum sample size of 100 and included participants not part of a diseased group. We calculated summary estimates using random-effects meta-analyses. Heterogeneity between studies was investigated using sub-group analysis and meta-regression. Results Meta-analyses from 36 cohorts (36,230 participants) showed that on average females had longer telomeres than males (standardised difference in telomere length between females and males 0.090, 95% CI 0.015, 0.166; age-adjusted). There was little evidence that these associations varied by age group (p = 1.00) or cell type (p = 0.29). However, the size of this difference did vary by measurement methods, with only Southern blot but neither real-time PCR nor Flow-FISH showing a significant difference. This difference was not associated with random measurement error. Conclusions Telomere length is longer in females than males, although this difference was not universally found in studies that did not use Southern blot methods. Further research on explanations for the methodological differences is required. PMID:24365661

  2. Investigation of hyperfine interactions in DNA and antibody of different lineages of mice infected by T. cruzi by perturbed gamma-gamma angular correlation spectroscopy; Investigacao de interacoes hiperfinas em DNA e anticorpos de diferentes linhagens de camundongos frente a infeccao por T. cruzi pela epectroscopia de correlacao angular gama-gama perturbada

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Andreia dos Santos

    2012-07-01

    In the present work perturbed angular correlation (PAC) spectroscopy was used to measured electric quadrupole interactions in DNA biomolecules of different mice lineages (A/J, C57BL/6, B6AF1, BXA1 e BXA2), samples of different isotypes of immunoglobulin G (IgG1, IgG2a e IgG2b) and active portions of complete and fragmented immunoglobulin responsible by the immune response. Electric quadrupole interactions were also measured in DNA nitrogenous bases (adenine, cytosine, guanine, thymine). PAC measurements were performed using {sup 111}In {yields} {sup 111C}d; {sup 111mC}d {yields} {sup 111}Cd; {sup 111}Ag {yields} {sup 111}Cd; e {sup 181}Hf {yields} {sup 181}Ta as probe nuclei, and carried out at room temperature and liquid nitrogen temperature, in order to investigate dynamic and static hyperfine interactions, respectively. The biomolecule samples were directly marked with the radioactive parent nuclei, whose atom link to a certain site in the biomolecules. The biological materials as well as the probe nuclei were chosen to investigate the possibility to use PAC spectroscopy to measure hyperfine parameters at nuclei from metallic elements bound to biomolecules (including the use of different probe nuclei produced in the decay of parent nuclei of four different metals) and also to study the behavior of different biomolecules by means of the measured hyperfine parameters. Results show differences in the hyperfine interactions of probe nuclei bound to the studied biomolecules. Such differences were observed by variations in the hyperfine parameters, which depend on the type of biomolecule and the results also show that the probe nuclei atom bound to the molecule in some cases and in others do not. (author)

  3. Examining a scaled dynamical system of telomere shortening

    Science.gov (United States)

    Cyrenne, Benoit M.; Gooding, Robert J.

    2015-02-01

    A model of telomere dynamics is proposed and examined. Our model, which extends a previously introduced model that incorporates stem cells as progenitors of new cells, imposes the Hayflick limit, the maximum number of cell divisions that are possible. This new model leads to cell populations for which the average telomere length is not necessarily a monotonically decreasing function of time, in contrast to previously published models. We provide a phase diagram indicating where such results would be expected via the introduction of scaled populations, rate constants and time. The application of this model to available leukocyte baboon data is discussed.

  4. Association of Telomere Length with Breast Cancer Prognostic Factors.

    Directory of Open Access Journals (Sweden)

    Kaoutar Ennour-Idrissi

    Full Text Available Telomere length, a marker of cell aging, seems to be affected by the same factors thought to be associated with breast cancer prognosis.To examine associations of peripheral blood cell-measured telomere length with traditional and potential prognostic factors in breast cancer patients.We conducted a cross-sectional analysis of data collected before surgery from 162 breast cancer patients recruited consecutively between 01/2011 and 05/2012, at a breast cancer reference center. Data on the main lifestyle factors (smoking, alcohol consumption, physical activity were collected using standardized questionnaires. Anthropometric factors were measured. Tumor biological characteristics were extracted from pathology reports. Telomere length was measured using a highly reproducible quantitative PCR method in peripheral white blood cells. Spearman partial rank-order correlations and multivariate general linear models were used to evaluate relationships between telomere length and prognostic factors.Telomere length was positively associated with total physical activity (rs = 0.17, P = 0.033; Ptrend = 0.069, occupational physical activity (rs = 0.15, P = 0.054; Ptrend = 0.054 and transportation-related physical activity (rs = 0.19, P = 0.019; P = 0.005. Among post-menopausal women, telomere length remained positively associated with total physical activity (rs = 0.27, P = 0.016; Ptrend = 0.054 and occupational physical activity (rs = 0.26, P = 0.021; Ptrend = 0.056 and was only associated with transportation-related physical activity among pre-menopausal women (rs = 0.27, P = 0.015; P = 0.004. No association was observed between telomere length and recreational or household activities, other lifestyle factors or traditional prognostic factors.Telomeres are longer in more active breast cancer patients. Since white blood cells are involved in anticancer immune responses, these findings suggest that even regular low-intensity physical activity, such as that

  5. Telomere length and early severe social deprivation: linking early adversity and cellular aging

    Science.gov (United States)

    Drury, SS; Theall, K; Gleason, MM; Smyke, AT; De Vivo, I; Wong, JYY; Fox, NA; Zeanah, CH; Nelson, CA

    2012-01-01

    Accelerated telomere length attrition has been associated with psychological stress and early adversity in adults; however, no studies have examined whether telomere length in childhood is associated with early experiences. The Bucharest Early Intervention Project is a unique randomized controlled trial of foster care placement compared with continued care in institutions. As a result of the study design, participants were exposed to a quantified range of time in institutional care, and represented an ideal population in which to examine the association between a specific early adversity, institutional care and telomere length. We examined the association between average relative telomere length, telomere repeat copy number to single gene copy number (T/S) ratio and exposure to institutional care quantified as the percent of time at baseline (mean age 22 months) and at 54 months of age that each child lived in the institution. A significant negative correlation between T/S ratio and percentage of time was observed. Children with greater exposure to institutional care had significantly shorter relative telomere length in middle childhood. Gender modified this main effect. The percentage of time in institutional care at baseline significantly predicted telomere length in females, whereas the percentage of institutional care at 54 months was strongly predictive of telomere length in males. This is the first study to demonstrate an association between telomere length and institutionalization, the first study to find an association between adversity and telomere length in children, and contributes to the growing literature linking telomere length and early adversity. PMID:21577215

  6. A meta-analysis of the relationship between anxiety and telomere length.

    Science.gov (United States)

    Malouff, John M; Schutte, Nicola S

    2017-05-01

    Telomeres are protective caps at the ends of chromosomes, and shorter telomeres are associated with poor physical health. The present study set out to consolidate the varying effect sizes found so far in studies of anxiety and telomere length. A meta-analytic investigation of the relationship between anxiety and telomere length used information from 17 different samples comprising a total of 19,424 participants. The results showed a small but significant association, r = -.06, between higher anxiety and shorter telomeres. Studies comparing individuals diagnosed with an anxiety disorder with other individuals had a significant effect size, and studies that did not use this comparison threshold did not have a significant effect size. Anxiety is associated with an important biomarker related to health. Future experimental studies that examine the impact of interventions intended to reduce anxiety in conjunction with measurement of telomere length can further clarify the impact of anxiety on telomere length.

  7. Perturbative anyon gas

    International Nuclear Information System (INIS)

    Dasnieres de Veigy, A.; Ouvry, S.; Paris-6 Univ., 75

    1992-06-01

    The problem of the statistical mechanics of an anyon gas is addressed. A perturbative analysis in the anyonic coupling constant α is reviewed, and the thermodynamical potential is computed at first and second order. An adequate second quantized formalism (field theory at finite temperature) is proposed. At first order in perturbation theory, the results are strikingly simple: only the second virial coefficient close to bosonic statistics is corrected. At second order, however, the complexity of the anyon model appears. One can compute exactly the perturbative correction to each cluster coefficient. However, and contrary to first order, a closed expression for the equation of state seems out of reach. As an illustration, the perturbative expressions of a 3 , a 4 , a 5 and a 6 are given at second order. Finally, using the same formalism, the equation of state of an anyon gas in a constant magnetic field is analyzed at first order in perturbation theory. (K.A.) 16 refs.; 3 figs.; 7 tabs

  8. DNA methylation

    DEFF Research Database (Denmark)

    Williams, Kristine; Christensen, Jesper; Helin, Kristian

    2012-01-01

    DNA methylation is involved in key cellular processes, including X-chromosome inactivation, imprinting and transcriptional silencing of specific genes and repetitive elements. DNA methylation patterns are frequently perturbed in human diseases such as imprinting disorders and cancer. The recent...... discovery that the three members of the TET protein family can convert 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) has provided a potential mechanism leading to DNA demethylation. Moreover, the demonstration that TET2 is frequently mutated in haematopoietic tumours suggests that the TET...... proteins are important regulators of cellular identity. Here, we review the current knowledge regarding the function of the TET proteins, and discuss various mechanisms by which they contribute to transcriptional control. We propose that the TET proteins have an important role in regulating DNA methylation...

  9. TERRA mimicking ssRNAs prevail over the DNA substrate for telomerase in vitro due to interactions with the alternative binding site.

    Science.gov (United States)

    Azhibek, Dulat; Skvortsov, Dmitry; Andreeva, Anna; Zatsepin, Timofei; Arutyunyan, Alexandr; Zvereva, Maria; Dontsova, Olga

    2016-06-01

    Telomerase is a key component of the telomere length maintenance system in the majority of eukaryotes. Telomerase displays maximal activity in stem and cancer cells with high proliferative potential. In humans, telomerase activity is regulated by various mechanisms, including the interaction with telomere ssDNA overhangs that contain a repetitive G-rich sequence, and with noncoding RNA, Telomeric repeat-containing RNA (TERRA), that contains the same sequence. So these nucleic acids can compete for telomerase RNA templates in the cell. In this study, we have investigated the ability of different model substrates mimicking telomere DNA overhangs and TERRA RNA to compete for telomerase in vitro through a previously developed telomerase inhibitor assay. We have shown in this study that RNA oligonucleotides are better competitors for telomerase that DNA ones as RNA also use an alternative binding site on telomerase, and the presence of 2'-OH groups is significant in these interactions. In contrast to DNA, the possibility of forming intramolecular G-quadruplex structures has a minor effect for RNA binding to telomerase. Taking together our data, we propose that TERRA RNA binds better to telomerase compared with its native substrate - the 3'-end of telomere DNA overhang. As a result, some specific factor may exist that participates in switching telomerase from TERRA to the 3'-end of DNA for telomere elongation at the distinct period of a cell cycle in vivo. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  10. An in silico investigation into the causes of telomere length heterogeneity and its implications for the Hayflick limit.

    Science.gov (United States)

    Golubev, A; Khrustalev, S; Butov, A

    2003-11-21

    In telomerase-negative cell populations the mean telomere length (TL) decreases with increasing population doubling number (PD). A critically small TL is believed to stop cell proliferation at a cell-, age- and species-specific PD thus defining the Hayflick limit. However, positively skewed TL distributions are broad compared to differences between initial and final mean TL and strongly overlap at middle and late PD, which is inconsistent with a limiting role of TL. We used computer-assisted modelling to define what set of premises may account for the above. Our model incorporates the following concepts. DNA end replication problem: telomeres loose 1 shortening unit (SU) upon each cell division. Free radical-caused TL decrease: telomeres experience random events resulting in the loss of a random SU number within a remaining TL. Stochasticity of gene expression and cell differentiation: cells experience random events inducing mitoses or committing cells to proliferation arrest, the latter option requiring a specified number of mitoses to be passed. Cells whose TL reaches 1SU cannot divide. The proliferation kinetics of such virtual cells conforms to the transition probability model of cell cycle. When no committing events occur and at realistic SU estimates of the initial TL, maximal PD values far exceed the Hayflick limit observed in normal cells and are consistent with the crisis stage entered by transformed cells that have surpassed the Hayflick limit. At intermediate PD, symmetrical TL distributions are yielded. Upon introduction of committing events making the ratio of the rates of proliferating and committing events (P/C) range from 1.10 to 1.25, TL distributions at intermediate PD become positively skewed, and virtual cell clones show bimodal size distributions. At P/C as high as 1.25 the majority of virtual cells at maximal PD contain telomeres with TL>1SU. A 10% increase in P/C within the 1.10-1.25 range produces a two-fold increase in the maximal PD, which

  11. Chiral perturbation theory

    International Nuclear Information System (INIS)

    Ecker, G.

    1996-06-01

    After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In the pion-nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy-nucleon expansion is used to construct the effective pion-nucleon Lagrangian to third order in the low-energy expansion, with applications to nucleon Compton scattering. (author)

  12. Leukocyte telomere length and late-life depression

    NARCIS (Netherlands)

    Schaakxs, R.; Verhoeven, J.E.; Oude Voshaar, R.C.; Comijs, H.C.; Penninx, B.W.

    2015-01-01

    Objective Depressive disorders have been associated with increased risk for aging-related diseases, possibly as a consequence of accelerated cellular aging. Cellular aging, indexed by telomere length (TL) shortening, has been linked to depression in adults younger than 60 years; however, it remains

  13. Telomere shortening reduces Alzheimer's disease amyloid pathology in mice

    NARCIS (Netherlands)

    Rolyan, Harshvardhan; Scheffold, Annika; Heinrich, Annette; Begus-Nahrmann, Yvonne; Langkopf, Britta Heike; Hoelter, Sabine M.; Vogt-Weisenhorn, Daniela M.; Liss, Birgit; Wurst, Wolfgang; Lie, Dieter Chichung; Thal, Dietmar Rudolf; Biber, Knut; Rudolph, Karl Lenhard

    Alzheimer's disease is a neurodegenerative disorder of the elderly and advancing age is the major risk factor for Alzheimer's disease development. Telomere shortening represents one of the molecular causes of ageing that limits the proliferative capacity of cells, including neural stem cells.

  14. Relative telomere length is associated with a functional ...

    Indian Academy of Sciences (India)

    ated with several neuropsychiatric disorders, such as major depression ... with shorter telomeres in white blood cells of healthy indi- viduals (Starkweather et al. 2014). Recently, a systematic review identified a possible association between shorter TL and high levels of ... MAOA protein plays an important role in the regula-.

  15. Sexual intimacy in couples is associated with longer telomere length.

    Science.gov (United States)

    Cabeza de Baca, Tomás; Epel, Elissa S; Robles, Theodore F; Coccia, Michael; Gilbert, Amanda; Puterman, Eli; Prather, Aric A

    2017-07-01

    High-quality relationships have been shown to be beneficial for physical and mental health. This study examined overall relationship satisfaction and perceived stress as well as daily reports of partner support, partner conflict, and physical intimacy obtained over the course of one week in a sample of 129 high and low stress mothers. Telomere length was examined in whole blood, as well as the two cell subpopulations: peripheral blood mononuclear cells (PBMCs) and granulocytes. Telomerase activity was measured in PBMCs. Analyses revealed no statistically significant associations of telomere length with current relationship satisfaction, daily support or conflict, or perceived stress. In contrast, women who reported any sexual intimacy during the course of the week had significantly longer telomeres measured in whole blood and PBMCs, but not in granulocytes. These relationships held covarying for age, body mass index, perceived stress, the relationship indices, and caregiver status. Sexual intimacy was not significantly related to PBMC telomerase activity. These data provide preliminary data that sexual intimacy is associated with longer telomere length. Future studies investigating these associations are warranted. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Cellular Consequences of Telomere Shortening in Histologically Normal Breast Tissues

    Science.gov (United States)

    2011-09-01

    axillary node metastasis, and histopathologic grading. Cancer 1984;54:2237–2242. 26 Anderson WF, Chu KC , Chatterjee N, et al. Tumor variants by hormone...alternatively lengthened telomeres. Am J Pathol 2010, 177:2694–2700 26. Hakin-Smith V, Jellinek DA, Levy D, Carroll T, Teo M, Timperley WR, McKay MJ

  17. Ancestral telomere shortening: a countdown that will increase mean life span?

    Science.gov (United States)

    Hertzog, Radu G

    2006-01-01

    Like cells, all mammals have a limited life span. Among cells there are a few exceptions (e.g., immortal cells), among mammals not, even if some of them live longer. Many in vitro and in vivo studies support the consensus that telomere length is strongly correlated with life span. At the somatic cellular level, long telomeres have been associated with longer life span. A different situation can be seen in immortal cells, such as cancer, germ and stem cells, where telomeres are maintained by telomerase, a specialized reverse transcriptase that is involved in synthesis of telomeres. Irrespective of telomere length, if telomerase is active, telomeres can be maintained at a sufficient length to ensure cell survival. To the contrary, telomeres shorten progressively with each cell division and when a critical telomere length (Hayflick limit) is reached, the cells undergo senescence and subsequently apoptosis. In mammals, those with the longest telomeres (e.g., mice) have the shortest life span. Furthermore, the shorter the mean telomere length, the longer the mean life span, as observed in humans (10-14 kpb) and bowhead-whales (undetermined telomere length), which have the longest mean life span among mammals. Over the past centuries, human average life span has increased. The hypothesis presented here suggests that this continual increase in the mean life span could be due to a decrease of mean telomere length over the last hundreds years. Actually, the life span is not directly influenced by length of telomeres, but rather by telomere length - dependent gene expression pattern. According to Greider, "rather than average telomere length, it is the shortest telomere length that makes the biggest difference to a cell". In the context of fast-growing global elderly population due to increase in life expectancy, it also seem to be an age related increase in cancer incidence. Nevertheless, extending healthy life span could depend on how good cells achieve, during the

  18. Preheating curvaton perturbations

    International Nuclear Information System (INIS)

    Bastero-Gil, M.; Di Clemente, V.; King, S.F.

    2005-01-01

    We discuss the potentially important role played by preheating in certain variants of the curvaton mechanism in which isocurvature perturbations of a D-flat (and F-flat) direction become converted to curvature perturbations during reheating. We discover that parametric resonance of the isocurvature components amplifies the superhorizon fluctuations by a significant amount. As an example of these effects we develop a particle physics motivated model which involves hybrid inflation with the waterfall field N being responsible for generating the μ term, the right-handed neutrino mass scale, and the Peccei-Quinn symmetry breaking scale. The role of the curvaton field can be played either by usual Higgs field, or the lightest right-handed sneutrino. Our new results show that it is possible to achieve the correct curvature perturbations for initial values of the curvaton fields of order the weak scale. In this model we show that the prediction for the spectral index of the final curvature perturbation only depends on the mass of the curvaton during inflation, where consistency with current observational data requires the ratio of this mass to the Hubble constant to be 0.3

  19. String perturbation theory diverges

    International Nuclear Information System (INIS)

    Gross, D.J.; Periwal, V.

    1988-01-01

    We prove that perturbation theory for the bosonic string diverges for arbitrary values of the coupling constant and is not Borel summable. This divergence is independent of the existence of the infinities that occur in the theory due to the presence of tachyons and dilaton tadpoles. We discuss the physical implications of such a divergence

  20. Divergent Perturbation Series

    International Nuclear Information System (INIS)

    Suslov, I.M.

    2005-01-01

    Various perturbation series are factorially divergent. The behavior of their high-order terms can be determined by Lipatov's method, which involves the use of instanton configurations of appropriate functional integrals. When the Lipatov asymptotic form is known and several lowest order terms of the perturbation series are found by direct calculation of diagrams, one can gain insight into the behavior of the remaining terms of the series, which can be resummed to solve various strong-coupling problems in a certain approximation. This approach is demonstrated by determining the Gell-Mann-Low functions in φ 4 theory, QED, and QCD with arbitrary coupling constants. An overview of the mathematical theory of divergent series is presented, and interpretation of perturbation series is discussed. Explicit derivations of the Lipatov asymptotic form are presented for some basic problems in theoretical physics. A solution is proposed to the problem of renormalon contributions, which hampered progress in this field in the late 1970s. Practical perturbation-series summation schemes are described both for a coupling constant of order unity and in the strong-coupling limit. An interpretation of the Borel integral is given for 'non-Borel-summable' series. Higher order corrections to the Lipatov asymptotic form are discussed

  1. Instantaneous stochastic perturbation theory

    International Nuclear Information System (INIS)

    Lüscher, Martin

    2015-01-01

    A form of stochastic perturbation theory is described, where the representative stochastic fields are generated instantaneously rather than through a Markov process. The correctness of the procedure is established to all orders of the expansion and for a wide class of field theories that includes all common formulations of lattice QCD.

  2. Cosmological perturbations in antigravity

    Science.gov (United States)

    Oltean, Marius; Brandenberger, Robert

    2014-10-01

    We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the standard model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity," during each successive transition from a big crunch to a big bang. For simplicity, we consider scalar perturbations in the absence of anisotropies, with potential set to zero and without any radiation. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, these perturbations are neither ghostlike nor tachyonic in the limit of strongly repulsive gravity. On this basis, we argue—pending a future analysis of vector and tensor perturbations—that, with respect to perturbative stability, the cosmological solutions of this theory are viable.

  3. Perturbed Markov chains

    OpenAIRE

    Solan, Eilon; Vieille, Nicolas

    2015-01-01

    We study irreducible time-homogenous Markov chains with finite state space in discrete time. We obtain results on the sensitivity of the stationary distribution and other statistical quantities with respect to perturbations of the transition matrix. We define a new closeness relation between transition matrices, and use graph-theoretic techniques, in contrast with the matrix analysis techniques previously used.

  4. Scalar cosmological perturbations

    International Nuclear Information System (INIS)

    Uggla, Claes; Wainwright, John

    2012-01-01

    Scalar perturbations of Friedmann-Lemaitre cosmologies can be analyzed in a variety of ways using Einstein's field equations, the Ricci and Bianchi identities, or the conservation equations for the stress-energy tensor, and possibly introducing a timelike reference congruence. The common ground is the use of gauge invariants derived from the metric tensor, the stress-energy tensor, or from vectors associated with a reference congruence, as basic variables. Although there is a complication in that there is no unique choice of gauge invariants, we will show that this can be used to advantage. With this in mind our first goal is to present an efficient way of constructing dimensionless gauge invariants associated with the tensors that are involved, and of determining their inter-relationships. Our second goal is to give a unified treatment of the various ways of writing the governing equations in dimensionless form using gauge-invariant variables, showing how simplicity can be achieved by a suitable choice of variables and normalization factors. Our third goal is to elucidate the connection between the metric-based approach and the so-called 1 + 3 gauge-invariant approach to cosmological perturbations. We restrict our considerations to linear perturbations, but our intent is to set the stage for the extension to second-order perturbations. (paper)

  5. Generalized perturbation series

    International Nuclear Information System (INIS)

    Baird, L.C.; Stinchcomb, G.

    1973-01-01

    An approximate solution of the Green's function equation may be used to generate an exact solution of the Schroedinger equation. This is accomplished through an iterative procedure. The procedure is equivalent to a perturbation expansion if the approximate Green's function is exact with respect to some reference potential

  6. Perturbed S3 neutrinos

    DEFF Research Database (Denmark)

    jora, Renata; Schechter, Joseph; Naeem Shahid, M.

    2009-01-01

    We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presenceof an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unper...... at the unperturbed level....

  7. DNA nanotechnology: On-command molecular Trojans

    Science.gov (United States)

    Niemeyer, Christof M.

    2017-12-01

    Lipid-motif-decorated DNA nanocapsules filled with photoresponsive polymers are capable of delivering signalling molecules into target organisms for biological perturbations at high spatiotemporal resolution.

  8. Tet Enzymes Regulate Telomere Maintenance and Chromosomal Stability of Mouse ESCs

    Directory of Open Access Journals (Sweden)

    Jiao Yang

    2016-05-01

    Full Text Available Ten-eleven translocation (Tet family proteins convert 5-methylcytosine to 5-hydroxymethylcytosine. We show that mouse embryonic stem cells (ESCs depleted of Tet1 and/or Tet2 by RNAi exhibit short telomeres and chromosomal instability, concomitant with reduced telomere recombination. Tet1 and Tet2 double-knockout ESCs also display short telomeres but to a lesser extent. Notably, Tet1/2/3 triple-knockout ESCs show heterogeneous telomere lengths and increased frequency of telomere loss and chromosomal fusion. Mechanistically, Tets depletion or deficiency increases Dnmt3b and decreases 5hmC levels, resulting in elevated methylation levels at sub-telomeres. Consistently, knockdown of Dnmt3b or addition of 2i (MAPK and GSK3β inhibitors, which also inhibits Dnmt3b, reduces telomere shortening, partially rescuing Tet1/2 deficiency. Interestingly, Tet1/2 double or Tet1/2/3 triple knockout in ESCs consistently upregulates Zscan4, which may counteract telomere shortening. Together, Tet enzymes play important roles in telomere maintenance and chromosomal stability of ESCs by modulating sub-telomeric methylation levels.

  9. Telomere-Centromere-Driven Genomic Instability Contributes to Karyotype Evolution in a Mouse Model of Melanoma

    Directory of Open Access Journals (Sweden)

    Amanda Gonçalves dos Santos Silva

    2010-01-01

    Full Text Available Aneuploidy and chromosomal instability (CIN are hallmarks of most solid tumors. These alterations may result from inaccurate chromosomal segregation during mitosis, which can occur through several mechanisms including defective telomere metabolism, centrosome amplification, dysfunctional centromeres, and/or defective spindle checkpoint control. In this work, we used an in vitro murine melanoma model that uses a cellular adhesion blockade as a transforming factor to characterize telomeric and centromeric alterations that accompany melanocyte transformation. To study the timing of the occurrence of telomere shortening in this transformation model, we analyzed the profile of telomere length by quantitative fluorescent in situ hybridization and found that telomere length significantly decreased as additional rounds of cell adhesion blockages were performed. Together with it, an increase in telomere-free ends and complex karyotypic aberrations were also found, which include Robertsonian fusions in 100% of metaphases of the metastatic melanoma cells. These findings are in agreement with the idea that telomere length abnormalities seem to be one of the earliest genetic alterations acquired in the multistep process of malignant transformation and that telomere abnormalities result in telomere aggregation, breakage-bridge-fusion cycles, and CIN. Another remarkable feature of this model is the abundance of centromeric instability manifested as centromere fragments and centromeric fusions. Taken together, our results illustrate for this melanoma model CIN with a structural signature of centromere breakage and telomeric loss.

  10. The relationship between telomere length and mortality in chronic obstructive pulmonary disease (COPD.

    Directory of Open Access Journals (Sweden)

    Jee Lee

    Full Text Available Some have suggested that chronic obstructive pulmonary disease (COPD is a disease of accelerated aging. Aging is characterized by shortening of telomeres. The relationship of telomere length to important clinical outcomes such as mortality, disease progression and cancer in COPD is unknown. Using quantitative polymerase chain reaction (qPCR, we measured telomere length of peripheral leukocytes in 4,271 subjects with mild to moderate COPD who participated in the Lung Health Study (LHS. The subjects were followed for approximately 7.5 years during which time their vital status, FEV(1 and smoking status were ascertained. Using multiple regression methods, we determined the relationship of telomere length to cancer and total mortality in these subjects. We also measured telomere length in healthy "mid-life" volunteers and patients with more severe COPD. The LHS subjects had significantly shorter telomeres than those of healthy "mid-life" volunteers (p<.001. Compared to individuals in the 4(th quartile of relative telomere length (i.e. longest telomere group, the remaining participants had significantly higher risk of cancer mortality (Hazard ratio, HR, 1.48; p = 0.0324 and total mortality (HR, 1.29; p = 0.0425. Smoking status did not make a significant difference in peripheral blood cells telomere length. In conclusion, COPD patients have short leukocyte telomeres, which are in turn associated increased risk of total and cancer mortality. Accelerated aging is of particular relevance to cancer mortality in COPD.

  11. Recognition of base J in duplex DNA by J-binding protein

    NARCIS (Netherlands)

    Sabatini, Robert; Meeuwenoord, Nico; van Boom, Jacques H.; Borst, Piet

    2002-01-01

    beta-d-Glucosylhydroxymethyluracil, also called base J, is an unusual modified DNA base conserved among Kinetoplastida. Base J is found predominantly in repetitive DNA and correlates with epigenetic silencing of telomeric variant surface glycoprotein genes. We have previously found a J-binding

  12. Interstitial telomere-like repeats in the Arabidopsis thaliana genome.

    Science.gov (United States)

    Uchida, Wakana; Matsunaga, Sachihiro; Sugiyama, Ryuji; Kawano, Shigeyuki

    2002-02-01

    Eukaryotic chromosomal ends are protected by telomeres, which are thought to play an important role in ensuring the complete replication of chromosomes. On the other hand, non-functional telomere-like repeats in the interchromosomal regions (interstitial telomeric repeats; ITRs) have been reported in several eukaryotes. In this study, we identified eight ITRs in the Arabidopsis thaliana genome, each consisting of complete and degenerate 300- to 1200-bp sequences. The ITRs were grouped into three classes (class IA-B, class II, and class IIIA-E) based on the degeneracy of the telomeric repeats in ITRs. The telomeric repeats of the two ITRs in class I were conserved for the most part, whereas the single ITR in class II, and the five ITRs in class III were relatively degenerated. In addition, degenerate ITRs were surrounded by common sequences that shared 70-100% homology to each other; these are named ITR-adjacent sequences (IAS). Although the genomic regions around ITRs in class I lacked IAS, those around ITRs in class II contained IAS (IASa), and those around five ITRs in class III had nine types of IAS (IASb, c, d, e, f, g, h, i, and j). Ten IAS types in classes II and III showed no significant homology to each other. The chromosomal locations of ITRs and IAS were not category-related, but most of them were adjacent to, or part of, a centromere. These results show that the A. thaliana genome has undergone chromosomal rearrangements, such as end-fusions and segmental duplications.

  13. Early life adversity and telomere length: a meta-analysis.

    Science.gov (United States)

    Ridout, K K; Levandowski, M; Ridout, S J; Gantz, L; Goonan, K; Palermo, D; Price, L H; Tyrka, A R

    2018-04-01

    Early adversity, in the form of abuse, neglect, socioeconomic status and other adverse experiences, is associated with poor physical and mental health outcomes. To understand the biologic mechanisms underlying these associations, studies have evaluated the relationship between early adversity and telomere length, a marker of cellular senescence. Such results have varied in regard to the size and significance of this relationship. Using meta-analytic techniques, we aimed to clarify the relationship between early adversity and telomere length while exploring factors affecting the association, including adversity type, timing and study design. A comprehensive search in July 2016 of PubMed/MEDLINE, PsycINFO and Web of Science identified 2462 studies. Multiple reviewers appraised studies for inclusion or exclusion using a priori criteria; 3.9% met inclusion criteria. Data were extracted into a structured form; the Newcastle-Ottawa Scale assessed study quality, validity and bias. Forty-one studies (N=30 773) met inclusion criteria. Early adversity and telomere length were significantly associated (Cohen's d effect size=-0.35; 95% CI, -0.46 to -0.24; P<0.0001). Sensitivity analyses revealed no outlier effects. Adversity type and timing significantly impacted the association with telomere length (P<0.0001 and P=0.0025, respectively). Subgroup and meta-regression analyses revealed that medication use, medical or psychiatric conditions, case-control vs longitudinal study design, methodological factors, age and smoking significantly affected the relationship. Comprehensive evaluations of adversity demonstrated more extensive telomere length changes. These results suggest that early adversity may have long-lasting physiological consequences contributing to disease risk and biological aging.

  14. Analysis of repetitive DNA in chromosomes by flow cytometry

    NARCIS (Netherlands)

    Brind'Amour, Julie; Lansdorp, Peter M.

    We developed a flow cytometry method, chromosome flow fluorescence in situ hybridization (FISH), called CFF, to analyze repetitive DNA in chromosomes using FISH with directly labeled peptide nucleic acid (PNA) probes. We used CFF to measure the abundance of interstitial telomeric sequences in

  15. Telomere length differences between subcutaneous and visceral adipose tissue in humans

    International Nuclear Information System (INIS)

    Lakowa, Nicole; Trieu, Nhu; Flehmig, Gesine; Lohmann, Tobias; Schön, Michael R.; Dietrich, Arne; Zeplin, Philip Helge; Langer, Stefan; Stumvoll, Michael; Blüher, Matthias; Klöting, Nora

    2015-01-01

    Adipocyte hypertrophy and hyperplasia have been shown to be associated with shorter telomere length, which may reflect aging, altered cell proliferation and adipose tissue (AT) dysfunction. In individuals with obesity, differences in fat distribution and AT cellular composition may contribute to obesity related metabolic diseases. Here, we tested the hypotheses that telomere lengths (TL) are different between: (1) abdominal subcutaneous and omental fat depots, (2) superficial and deep abdominal subcutaneous AT (SAT), and (3) adipocytes and cells of the stromal vascular fraction (SVF). We further asked whether AT TL is related to age, anthropometric and metabolic traits. TL was analyzed by quantitative PCR in total human genomic DNA isolated from paired subcutaneous and visceral AT of 47 lean and 50 obese individuals. In subgroups, we analyzed TL in isolated small and large adipocytes and SVF cells. We find significantly shorter TL in subcutaneous compared to visceral AT (P < 0.001) which is consistent in men and subgroups of lean and obese, and individuals with or without type 2 diabetes (T2D). Shorter TL in SAT is entirely due to shorter TL in the SVF compared to visceral AT (P < 0.01). SAT TL is most strongly correlated with age (r = −0.205, P < 0.05) and independently of age with HbA1c (r = −0.5, P < 0.05). We found significant TL differences between superficial SAT of lean and obese as well as between individuals with our without T2D, but not between the two layers of SAT. Our data indicate that fat depot differences in TL mainly reflect shorter TL of SVF cells. In addition, we found an age and BMI-independent relationship between shorter TL and HbA1c suggesting that chronic hyperglycemia may impair the regenerative capacity of AT more strongly than obesity alone. - Highlights: • Telomere lengths (TL) differ between fat depots mainly due to different lengths in SVF. • TL is not associated with gender, BMI and T2D. • The tendency for

  16. Telomere length differences between subcutaneous and visceral adipose tissue in humans

    Energy Technology Data Exchange (ETDEWEB)

    Lakowa, Nicole; Trieu, Nhu; Flehmig, Gesine [Department of Medicine, University of Leipzig, Leipzig (Germany); Lohmann, Tobias [Municipal Clinic Dresden-Neustadt, Dresden (Germany); Schön, Michael R. [Städtisches Klinikum Karlsruhe, Clinic of Visceral Surgery, Karlsruhe (Germany); Dietrich, Arne [Department of Surgery, University of Leipzig, Leipzig (Germany); IFB AdiposityDiseases, University of Leipzig, Leipzig (Germany); Zeplin, Philip Helge; Langer, Stefan [Department of Orthopaedics, Traumatology and Plastic Surgery, University of Leipzig, Leipzig (Germany); Stumvoll, Michael; Blüher, Matthias [Department of Medicine, University of Leipzig, Leipzig (Germany); Klöting, Nora, E-mail: nora.kloeting@medizin.uni-leipzig.de [IFB AdiposityDiseases, Junior Research Group 2 “Animal Models of Obesity”, University of Leipzig, Leipzig (Germany)

    2015-02-13

    Adipocyte hypertrophy and hyperplasia have been shown to be associated with shorter telomere length, which may reflect aging, altered cell proliferation and adipose tissue (AT) dysfunction. In individuals with obesity, differences in fat distribution and AT cellular composition may contribute to obesity related metabolic diseases. Here, we tested the hypotheses that telomere lengths (TL) are different between: (1) abdominal subcutaneous and omental fat depots, (2) superficial and deep abdominal subcutaneous AT (SAT), and (3) adipocytes and cells of the stromal vascular fraction (SVF). We further asked whether AT TL is related to age, anthropometric and metabolic traits. TL was analyzed by quantitative PCR in total human genomic DNA isolated from paired subcutaneous and visceral AT of 47 lean and 50 obese individuals. In subgroups, we analyzed TL in isolated small and large adipocytes and SVF cells. We find significantly shorter TL in subcutaneous compared to visceral AT (P < 0.001) which is consistent in men and subgroups of lean and obese, and individuals with or without type 2 diabetes (T2D). Shorter TL in SAT is entirely due to shorter TL in the SVF compared to visceral AT (P < 0.01). SAT TL is most strongly correlated with age (r = −0.205, P < 0.05) and independently of age with HbA1c (r = −0.5, P < 0.05). We found significant TL differences between superficial SAT of lean and obese as well as between individuals with our without T2D, but not between the two layers of SAT. Our data indicate that fat depot differences in TL mainly reflect shorter TL of SVF cells. In addition, we found an age and BMI-independent relationship between shorter TL and HbA1c suggesting that chronic hyperglycemia may impair the regenerative capacity of AT more strongly than obesity alone. - Highlights: • Telomere lengths (TL) differ between fat depots mainly due to different lengths in SVF. • TL is not associated with gender, BMI and T2D. • The tendency for

  17. Studying the perturbative Reggeon

    International Nuclear Information System (INIS)

    Griffiths, S.; Ross, D.A.

    2000-01-01

    We consider the flavour non-singlet Reggeon within the context of perturbative QCD. This consists of ladders built out of ''reggeized'' quarks. We propose a method for the numerical solution of the integro-differential equation for the amplitude describing the exchange of such a Reggeon. The solution is known to have a sharp rise at low values of Bjorken-x when applied to non-singlet quantities in deep-inelastic scattering. We show that when the running of the coupling is taken into account this sharp rise is further enhanced, although the Q 2 dependence is suppressed by the introduction of the running coupling. We also investigate the effects of simulating non-perturbative physics by introducing a constituent mass for the soft quarks and an effective mass for the soft gluons exchanged in the t-channel. (orig.)

  18. Renormalized Lie perturbation theory

    International Nuclear Information System (INIS)

    Rosengaus, E.; Dewar, R.L.

    1981-07-01

    A Lie operator method for constructing action-angle transformations continuously connected to the identity is developed for area preserving mappings. By a simple change of variable from action to angular frequency a perturbation expansion is obtained in which the small denominators have been renormalized. The method is shown to lead to the same series as the Lagrangian perturbation method of Greene and Percival, which converges on KAM surfaces. The method is not superconvergent, but yields simple recursion relations which allow automatic algebraic manipulation techniques to be used to develop the series to high order. It is argued that the operator method can be justified by analytically continuing from the complex angular frequency plane onto the real line. The resulting picture is one where preserved primary KAM surfaces are continuously connected to one another

  19. Nonperturbative perturbation theory

    International Nuclear Information System (INIS)

    Bender, C.M.

    1989-01-01

    In this talk we describe a recently proposed graphical perturbative calculational scheme for quantum field theory. The basic idea is to expand in the power of the interaction term. For example, to solve a λφ 4 theory in d-dimensional space-time, we introduce a small parameter δ and consider a λ(φ 2 ) 1+δ field theory. We show how to expand such a theory as a series in powers of δ. The resulting perturbation series appears to have a finite radius of convergence and numerical results for low-dimensional models are good. We have computed the two-point and four-point Green's functions to second order in powers of δ and the 2n-point Green's functions (n>2) to order δ. We explain how to renormalize the theory and show that, to first order in powers of δ, when δ>0 and d≥4 the theory is free. This conclusion remains valid to second order in powers of δ, and we believe that it remains valid to all orders in powers of δ. The new perturbative scheme is consistent with global supersymmetry invariance. We examine a two-dimensional supersymmetric quantum field theory in which we do not know of any other means for doing analytical calculations. We illustrate the power of this new technique by computing the ground-state energy density E to second order in this new perturbation theory. We show that there is a beautiful and delicate cancellation between infinite classes of graphs which leads to the result that E=0. (orig.)

  20. Perturbed asymptotically linear problems

    OpenAIRE

    Bartolo, R.; Candela, A. M.; Salvatore, A.

    2012-01-01

    The aim of this paper is investigating the existence of solutions of some semilinear elliptic problems on open bounded domains when the nonlinearity is subcritical and asymptotically linear at infinity and there is a perturbation term which is just continuous. Also in the case when the problem has not a variational structure, suitable procedures and estimates allow us to prove that the number of distinct crtitical levels of the functional associated to the unperturbed problem is "stable" unde...

  1. Utility of telomere length measurements for age determination of humpback whales

    Directory of Open Access Journals (Sweden)

    Morten Tange Olsen

    2014-12-01

    Full Text Available This study examines the applicability of telomere length measurements by quantitative PCR as a tool for minimally invasive age determination of free-ranging cetaceans. We analysed telomere length in skin samples from 28 North Atlantic humpback whales (Megaptera novaeangliae, ranging from 0 to 26 years of age. The results suggested a significant correlation between telomere length and age in humpback whales. However, telomere length was highly variable among individuals of similar age, suggesting that telomere length measured by quantitative PCR is an imprecise determinant of age in humpback whales. The observed variation in individual telomere length was found to be a function of both experimental and biological variability, with the latter perhaps reflecting patterns of inheritance, resource allocation trade-offs, and stochasticity of the marine environment.

  2. Telomere erosion varies during in vitro aging of normal human fibroblasts from young and adult donors.

    Science.gov (United States)

    Figueroa, R; Lindenmaier, H; Hergenhahn, M; Nielsen, K V; Boukamp, P

    2000-06-01

    The life span of normal fibroblasts in vitro (Hayflick limit) depends on donor age, and telomere shortening has been proposed as a potential mechanism. By quantitative fluorescence in situ hybridization and Southern blot analysis, we show progressive telomere loss to about 5 kb mean telomere restriction fragment length in fibroblasts from two adult donors within 40 population doublings, whereas in fibroblasts from two infant donors, telomere erosion is reduced, leaving a mean telomere restriction fragment length of approximately 7 kb at senescence (after approximately 60 population doublings). Aging of fibroblasts from both infant and adult donors was not accompanied by chromosomal abnormalities but was correlated with increased telomere repeat-binding factor 2 expression at both the protein and transcriptional level.

  3. Longer telomere length in peripheral white blood cells is associated with risk of lung cancer and the rs2736100 (CLPTM1L-TERT polymorphism in a prospective cohort study among women in China.

    Directory of Open Access Journals (Sweden)

    Qing Lan

    Full Text Available A recent genome-wide association study of lung cancer among never-smoking females in Asia demonstrated that the rs2736100 polymorphism in the TERT-CLPTM1L locus on chromosome 5p15.33 was strongly and significantly associated with risk of adenocarcinoma of the lung. The telomerase gene TERT is a reverse transcriptase that is critical for telomere replication and stabilization by controlling telomere length. We previously found that longer telomere length measured in peripheral white blood cell DNA was associated with increased risk of lung cancer in a prospective cohort study of smoking males in Finland. To follow up on this finding, we carried out a nested case-control study of 215 female lung cancer cases and 215 female controls, 94% of whom were never-smokers, in the prospective Shanghai Women's Health Study cohort. There was a dose-response relationship between tertiles of telomere length and risk of lung cancer (odds ratio (OR, 95% confidence interval [CI]: 1.0, 1.4 [0.8-2.5], and 2.2 [1.2-4.0], respectively; P trend = 0.003. Further, the association was unchanged by the length of time from blood collection to case diagnosis. In addition, the rs2736100 G allele, which we previously have shown to be associated with risk of lung cancer in this cohort, was significantly associated with longer telomere length in these same study subjects (P trend = 0.030. Our findings suggest that individuals with longer telomere length in peripheral white blood cells may have an increased risk of lung cancer, but require replication in additional prospective cohorts and populations.

  4. Twisting perturbed parafermions

    Directory of Open Access Journals (Sweden)

    A.V. Belitsky

    2017-07-01

    Full Text Available The near-collinear expansion of scattering amplitudes in maximally supersymmetric Yang–Mills theory at strong coupling is governed by the dynamics of stings propagating on the five sphere. The pentagon transitions in the operator product expansion which systematize the series get reformulated in terms of matrix elements of branch-point twist operators in the two-dimensional O(6 nonlinear sigma model. The facts that the latter is an asymptotically free field theory and that there exists no local realization of twist fields prevents one from explicit calculation of their scaling dimensions and operator product expansion coefficients. This complication is bypassed making use of the equivalence of the sigma model to the infinite-level limit of WZNW models perturbed by current–current interactions, such that one can use conformal symmetry and conformal perturbation theory for systematic calculations. Presently, to set up the formalism, we consider the O(3 sigma model which is reformulated as perturbed parafermions.

  5. The heritability of telomere length among the elderly and oldest-old

    DEFF Research Database (Denmark)

    Bischoff, Claus; Graakjaer, Jesper; Petersen, Hans Christian

    2005-01-01

    . Structural equation models revealed that a model including additive genetic effects and non-shared environment was the best fitting model and that telomere length was moderately heritable, with an estimate that was sensitive to the telomere length standardization procedure. Sex-specific analyses showed lower...... heritability in males, although not statistically significant, which is in line with our earlier finding of a sex difference in telomere dynamics among the elderly and oldest-old....

  6. Leukocyte telomere length in major depression: correlations with chronicity, inflammation and oxidative stress--preliminary findings.

    Directory of Open Access Journals (Sweden)

    Owen M Wolkowitz

    2011-03-01

    Full Text Available Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of "accelerated aging" in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD, whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation.Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio and inflammation (IL-6. Analyses were controlled for age and sex.The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05. Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration was 281 base pairs shorter than that in controls (p<0.05, corresponding to approximately seven years of "accelerated cell aging." Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01 and in the controls (p<0.05 and with inflammation in the depressed subjects (p<0.05.These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression and is not an intrinsic feature. Rather, telomere shortening

  7. Sex-dependent effects of nutrition on telomere dynamics in zebra finches (Taeniopygia guttata)

    OpenAIRE

    Noguera, Jose C.; Metcalfe, Neil B.; Boner, Winnie; Monaghan, Pat

    2015-01-01

    At a cellular level, oxidative stress is known to increase telomere attrition, and hence cellular senescence and risk of disease. It has been proposed that dietary micronutrients play an important role in telomere protection due to their antioxidant properties. We experimentally manipulated dietary micronutrients during early life in zebra finches (Taeniopygia guttata). We found no effects of micronutrient intake on telomere loss during chick growth. However, females given a diet high in micr...

  8. DNA-Mediated Electrochemistry

    Science.gov (United States)

    Gorodetsky, Alon A.; Buzzeo, Marisa C.

    2009-01-01

    The base pair stack of DNA has been demonstrated as a medium for long range charge transport chemistry both in solution and at DNA-modified surfaces. This chemistry is exquisitely sensitive to structural perturbations in the base pair stack as occur with lesions, single base mismatches, and protein binding. We have exploited this sensitivity for the development of reliable electrochemical assays based on DNA charge transport at self-assembled DNA monolayers. Here we discuss the characteristic features, applications, and advantages of DNA-mediated electrochemistry. PMID:18980370

  9. Exonuclease 1 and its versatile roles in DNA repair

    DEFF Research Database (Denmark)

    Keijzers, Guido; Liu, Dekang; Rasmussen, Lene Juel

    2016-01-01

    Exonuclease 1 (EXO1) is a multifunctional 5' → 3' exonuclease and a DNA structure-specific DNA endonuclease. EXO1 plays roles in DNA replication, DNA mismatch repair (MMR) and DNA double-stranded break repair (DSBR) in lower and higher eukaryotes and contributes to meiosis, immunoglobulin...... maturation, and micro-mediated end-joining in higher eukaryotes. In human cells, EXO1 is also thought to play a role in telomere maintenance. Mutations in the human EXO1 gene correlate with increased susceptibility to some cancers. This review summarizes recent studies on the enzymatic functions...

  10. The fission yeast heterochromatin protein Rik1 is required for telomere clustering during meiosis

    DEFF Research Database (Denmark)

    Tuzon, Creighton T; Borgstrøm, Britta; Weilguny, Dietmar

    2004-01-01

    Telomeres share the ability to silence nearby transcription with heterochromatin, but the requirement of heterochromatin proteins for most telomere functions is unknown. The fission yeast Rik1 protein is required for heterochromatin formation at centromeres and the mating-type locus, as it recrui...... meiosis. However, Rik1 is dispensable for the protective roles of telomeres in preventing chromosome end-fusion. Thus, a Swi6-independent heterochromatin function distinct from that at centromeres and the mating-type locus operates at telomeres during sexual differentiation....

  11. Telomere dynamics in a long-lived bird, the barnacle goose

    Directory of Open Access Journals (Sweden)

    Pauliny Angela

    2012-12-01

    Full Text Available Abstract Background Theories of ageing predict a trade-off between metabolism, reproduction, and maintenance. Species with low investment in early reproduction are thus expected to be able to evolve more efficient maintenance and repair mechanisms, allowing for a longer potential life span (intrinsic longevity. The erosion of telomeres, the protective caps at the ends of linear chromosomes, plays an important role in cellular and organismal senescence, signalling the onset of age-related disease due to accumulation of unrepaired somatic damage. Using extensive longitudinal data from a long-term study of a natural population of barnacle geese Branta leucopsis, we investigated individual rates of telomere length changes over two years in 34 birds between 0 and 22 years of age, covering almost 80% of the species’ lifespan. Results We show that telomeres in this long-lived bird are very well maintained, as theoretically expected, with an average loss rate of only 5 base pairs per year among adults. We thus found no significant relationship between change in telomere length and age. However, telomeres tended to shorten at a faster pace in juveniles compared to adults. For the first time, we demonstrate a faster telomere attrition rate in females compared to males. We found no correlation between telomere loss rate and adult survival or change in body mass. Conclusions Our results add further support for a link between longevity and telomere maintenance, and highlight the complexities of telomere dynamics in natural populations.

  12. The longest telomeres: a general signature of adult stem cell compartments

    Science.gov (United States)

    Flores, Ignacio; Canela, Andres; Vera, Elsa; Tejera, Agueda; Cotsarelis, George; Blasco, María A.

    2008-01-01

    Identification of adult stem cells and their location (niches) is of great relevance for regenerative medicine. However, stem cell niches are still poorly defined in most adult tissues. Here, we show that the longest telomeres are a general feature of adult stem cell compartments. Using confocal telomere quantitative fluorescence in situ hybridization (telomapping), we find gradients of telomere length within tissues, with the longest telomeres mapping to the known stem cell compartments. In mouse hair follicles, we show that cells with the longest telomeres map to the known stem cell compartments, colocalize with stem cell markers, and behave as stem cells upon treatment with mitogenic stimuli. Using K15-EGFP reporter mice, which mark hair follicle stem cells, we show that GFP-positive cells have the longest telomeres. The stem cell compartments in small intestine, testis, cornea, and brain of the mouse are also enriched in cells with the longest telomeres. This constitutes the description of a novel general property of adult stem cell compartments. Finally, we make the novel finding that telomeres shorten with age in different mouse stem cell compartments, which parallels a decline in stem cell functionality, suggesting that telomere loss may contribute to stem cell dysfunction with age. PMID:18283121

  13. Telomere shortening in hematopoietic stem cell transplantation: a potential mechanism for late graft failure?