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Sample records for add telomeric repeats

  1. Swi1Timeless Prevents Repeat Instability at Fission Yeast Telomeres.

    Gadaleta, Mariana C; Das, Mukund M; Tanizawa, Hideki; Chang, Ya-Ting; Noma, Ken-ichi; Nakamura, Toru M; Noguchi, Eishi

    2016-03-01

    Genomic instability associated with DNA replication stress is linked to cancer and genetic pathologies in humans. If not properly regulated, replication stress, such as fork stalling and collapse, can be induced at natural replication impediments present throughout the genome. The fork protection complex (FPC) is thought to play a critical role in stabilizing stalled replication forks at several known replication barriers including eukaryotic rDNA genes and the fission yeast mating-type locus. However, little is known about the role of the FPC at other natural impediments including telomeres. Telomeres are considered to be difficult to replicate due to the presence of repetitive GT-rich sequences and telomere-binding proteins. However, the regulatory mechanism that ensures telomere replication is not fully understood. Here, we report the role of the fission yeast Swi1(Timeless), a subunit of the FPC, in telomere replication. Loss of Swi1 causes telomere shortening in a telomerase-independent manner. Our epistasis analyses suggest that heterochromatin and telomere-binding proteins are not major impediments for telomere replication in the absence of Swi1. Instead, repetitive DNA sequences impair telomere integrity in swi1Δ mutant cells, leading to the loss of repeat DNA. In the absence of Swi1, telomere shortening is accompanied with an increased recruitment of Rad52 recombinase and more frequent amplification of telomere/subtelomeres, reminiscent of tumor cells that utilize the alternative lengthening of telomeres pathway (ALT) to maintain telomeres. These results suggest that Swi1 ensures telomere replication by suppressing recombination and repeat instability at telomeres. Our studies may also be relevant in understanding the potential role of Swi1(Timeless) in regulation of telomere stability in cancer cells. PMID:26990647

  2. Swi1Timeless Prevents Repeat Instability at Fission Yeast Telomeres.

    Mariana C Gadaleta

    2016-03-01

    Full Text Available Genomic instability associated with DNA replication stress is linked to cancer and genetic pathologies in humans. If not properly regulated, replication stress, such as fork stalling and collapse, can be induced at natural replication impediments present throughout the genome. The fork protection complex (FPC is thought to play a critical role in stabilizing stalled replication forks at several known replication barriers including eukaryotic rDNA genes and the fission yeast mating-type locus. However, little is known about the role of the FPC at other natural impediments including telomeres. Telomeres are considered to be difficult to replicate due to the presence of repetitive GT-rich sequences and telomere-binding proteins. However, the regulatory mechanism that ensures telomere replication is not fully understood. Here, we report the role of the fission yeast Swi1(Timeless, a subunit of the FPC, in telomere replication. Loss of Swi1 causes telomere shortening in a telomerase-independent manner. Our epistasis analyses suggest that heterochromatin and telomere-binding proteins are not major impediments for telomere replication in the absence of Swi1. Instead, repetitive DNA sequences impair telomere integrity in swi1Δ mutant cells, leading to the loss of repeat DNA. In the absence of Swi1, telomere shortening is accompanied with an increased recruitment of Rad52 recombinase and more frequent amplification of telomere/subtelomeres, reminiscent of tumor cells that utilize the alternative lengthening of telomeres pathway (ALT to maintain telomeres. These results suggest that Swi1 ensures telomere replication by suppressing recombination and repeat instability at telomeres. Our studies may also be relevant in understanding the potential role of Swi1(Timeless in regulation of telomere stability in cancer cells.

  3. Telomere repeat binding proteins are functional components of Arabidopsis telomeres and interact with telomerase

    Schrumpfová, P.; Vychodilová, I.; Dvořáčková, Martina; Majerská, J.; Dokládal, Ladislav; Schorová, Š.; Fajkus, Jiří

    2014-01-01

    Roč. 77, č. 5 (2014), s. 770-781. ISSN 0960-7412 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA ČR(CZ) GA13-06943S Institutional support: RVO:68081707 Keywords : telomere protein interaction * telomere repeat binding * Arabidopsis thaliana Subject RIV: BO - Biophysics Impact factor: 5.972, year: 2014

  4. Telomeric repeats facilitate CENP-A(Cnp1) incorporation via telomere binding proteins.

    Castillo, Araceli G; Pidoux, Alison L; Catania, Sandra; Durand-Dubief, Mickaël; Choi, Eun Shik; Hamilton, Georgina; Ekwall, Karl; Allshire, Robin C

    2013-01-01

    The histone H3 variant, CENP-A, is normally assembled upon canonical centromeric sequences, but there is no apparent obligate coupling of sequence and assembly, suggesting that centromere location can be epigenetically determined. To explore the tolerances and constraints on CENP-A deposition we investigated whether certain locations are favoured when additional CENP-A(Cnp1) is present in fission yeast cells. Our analyses show that additional CENP-A(Cnp1) accumulates within and close to heterochromatic centromeric outer repeats, and over regions adjacent to rDNA and telomeres. The use of minichromosome derivatives with unique DNA sequences internal to chromosome ends shows that telomeres are sufficient to direct CENP-A(Cnp1) deposition. However, chromosome ends are not required as CENP-A(Cnp1) deposition also occurs at telomere repeats inserted at an internal locus and correlates with the presence of H3K9 methylation near these repeats. The Ccq1 protein, which is known to bind telomere repeats and recruit telomerase, was found to be required to induce H3K9 methylation and thus promote the incorporation of CENP-A(Cnp1) near telomere repeats. These analyses demonstrate that at non-centromeric chromosomal locations the presence of heterochromatin influences the sites at which CENP-A is incorporated into chromatin and, thus, potentially the location of centromeres. PMID:23936074

  5. Telomeric repeats facilitate CENP-A(Cnp1 incorporation via telomere binding proteins.

    Araceli G Castillo

    Full Text Available The histone H3 variant, CENP-A, is normally assembled upon canonical centromeric sequences, but there is no apparent obligate coupling of sequence and assembly, suggesting that centromere location can be epigenetically determined. To explore the tolerances and constraints on CENP-A deposition we investigated whether certain locations are favoured when additional CENP-A(Cnp1 is present in fission yeast cells. Our analyses show that additional CENP-A(Cnp1 accumulates within and close to heterochromatic centromeric outer repeats, and over regions adjacent to rDNA and telomeres. The use of minichromosome derivatives with unique DNA sequences internal to chromosome ends shows that telomeres are sufficient to direct CENP-A(Cnp1 deposition. However, chromosome ends are not required as CENP-A(Cnp1 deposition also occurs at telomere repeats inserted at an internal locus and correlates with the presence of H3K9 methylation near these repeats. The Ccq1 protein, which is known to bind telomere repeats and recruit telomerase, was found to be required to induce H3K9 methylation and thus promote the incorporation of CENP-A(Cnp1 near telomere repeats. These analyses demonstrate that at non-centromeric chromosomal locations the presence of heterochromatin influences the sites at which CENP-A is incorporated into chromatin and, thus, potentially the location of centromeres.

  6. Variant repeats are interspersed throughout the telomeres and recruit nuclear receptors in ALT cells

    Conomos, Dimitri; Stutz, Michael D.; Hills, Mark; Neumann, Axel A.; Bryan, Tracy M.; Reddel, Roger R; Hilda A Pickett

    2012-01-01

    Telomeres in cells that use the recombination-mediated alternative lengthening of telomeres (ALT) pathway elicit a DNA damage response that is partly independent of telomere length. We therefore investigated whether ALT telomeres contain structural abnormalities that contribute to ALT activity. Here we used next generation sequencing to analyze the DNA content of ALT telomeres. We discovered that variant repeats were interspersed throughout the telomeres of ALT cells. We found that the C-type...

  7. Presence of alternative lengthening of telomeres associated circular extrachromosome telomere repeats in primary leukemia cells of chronic myeloid leukemia

    Samassekou, Oumar; Malina, Abba; Hébert, Josée; Yan, Ju

    2013-01-01

    Background The predominant mechanism by which human tumors maintain telomere length is via telomerase. In ~10% of tumor samples, however, telomere length is conserved, despite no detectable telomerase activity, in part through activation of the alternative lengthening of telomeres (ALT) pathway. Methods We studied the circular extra-chromosomal telomeric repeat (ECTR), an ALT hallmark, and telomerase activity in 24 chronic myeloid leukemia (CML) patients in chronic phase (CP). Results We iden...

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

    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

  9. Two tandemly repeated telomere-associated sequences in Nicotiana plumbaginifolia.

    Chen, C M; Wang, C T; Wang, C J; Ho, C H; Kao, Y Y; Chen, C C

    1997-12-01

    Two tandemly repeated telomere-associated sequences, NP3R and NP4R, have been isolated from Nicotiana plumbaginifolia. The length of a repeating unit for NP3R and NP4R is 165 and 180 nucleotides respectively. The abundance of NP3R, NP4R and telomeric repeats is, respectively, 8.4 x 10(4), 6 x 10(3) and 1.5 x 10(6) copies per haploid genome of N. plumbaginifolia. Fluorescence in situ hybridization revealed that NP3R is located at the ends and/or in interstitial regions of all 10 chromosomes and NP4R on the terminal regions of three chromosomes in the haploid genome of N. plumbaginifolia. Sequence homology search revealed that not only are NP3R and NP4R homologous to HRS60 and GRS, respectively, two tandem repeats isolated from N. tabacum, but that NP3R and NP4R are also related to each other, suggesting that they originated from a common ancestral sequence. The role of these repeated sequences in chromosome healing is discussed based on the observation that two to three copies of a telomere-similar sequence were present in each repeating unit of NP3R and NP4R. PMID:9451957

  10. Telomere extension by telomerase and ALT generates variant repeats by mechanistically distinct processes

    Lee, Michael; Hills, Mark; Conomos, Dimitri; Stutz, Michael D.; Dagg, Rebecca A.; Lau, Loretta M. S.; Reddel, Roger R; Hilda A Pickett

    2013-01-01

    Telomeres are terminal repetitive DNA sequences on chromosomes, and are considered to comprise almost exclusively hexameric TTAGGG repeats. We have evaluated telomere sequence content in human cells using whole-genome sequencing followed by telomere read extraction in a panel of mortal cell strains and immortal cell lines. We identified a wide range of telomere variant repeats in human cells, and found evidence that variant repeats are generated by mechanistically distinct processes during te...

  11. TTAGG-repeat telomeres and characterization of telomerase in the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae).

    Gong, H; Zhu, W; Zhang, J; Li, X; Meng, Q; Zhou, G; Wang, M; Wang, H; Miao, L; Qin, Q; Zhang, H

    2015-06-01

    Telomeres are maintained usually by telomerase, a specialized reverse transcriptase that adds this sequence to chromosome ends. In this study, telomerase activity was detected in the in different somatic tissues, such as midgut and fat bodies, by the telomeric repeat amplification protocol (TRAP) in Spodoptera exigua. The structure of the telomeres of S. exigua was evaluated by sequence analysis of the TRAP products, revealing that the telomerase synthesized a (TTAGG)n repeat. The presence of a telomerase reverse transcriptase (TERT) subunit coding gene has been cloned, sequenced and expressed in vitro successively. Notably, the S. exigua telomerase (SpexTERT) gene structure lacks the N-terminal GQ motif. Telomerase contains a large RNA subunit, TER, and a protein catalytic subunit, TERT. Here we report an in vitro system that was reconstructed by all components of the telomerase complex, a purified recombinant SpexTERT without a N-terminal GQ motif and a mutant human telomerase RNA (TER), showed telomerase activity. Together, these results suggest the GQ motif is not essential for telomerase catalysis. PMID:25689229

  12. Spectroscopic investigation on the telomeric DNA base sequence repeat

    2002-01-01

    Telomeres are protein-DNA complexes at the terminals of linear chromosomes, which protect chromosomal integrity and maintain cellular replicative capacity.From single-cell organisms to advanced animals and plants,structures and functions of telomeres are both very conservative. In cells of human and vertebral animals, telomeric DNA base sequences all are (TTAGGG)n. In the present work, we have obtained absorption and fluorescence spectra measured from seven synthesized oligonucleotides to simulate the telomeric DNA system and calculated their relative fluorescence quantum yields on which not only telomeric DNA characteristics are predicted but also possibly the shortened telomeric sequences during cell division are imrelative fluorescence quantum yield and remarkable excitation energy innerconversion, which tallies with the telomeric sequence of (TTAGGG)n. This result shows that telomeric DNA has a strong non-radiative or innerconvertible capability.``

  13. Chlamydomonas reinhardtii telomere repeats form unstable structures involving guanine-guanine base pairs.

    Petracek, M E; Berman, J.

    1992-01-01

    Unusual DNA structures involving four guanines in a planar formation (guanine tetrads) are formed by guanine-rich (G-rich) telomere DNA and other G-rich sequences (reviewed in (1)) and may be important in the structure and function of telomeres. These structures result from intrastrand and/or interstrand Hoogsteen base pairs between the guanines. We used the telomeric repeat of Chlamydomonas reinhardtii, TTTTAGGG, which contains 3 guanines and has a long interguanine A + T tract, to determine...

  14. The number of vertebrate repeats can be regulated at yeast telomeres by Rap1-independent mechanisms.

    Brevet, Vanessa; Berthiau, Anne-Sophie; Civitelli, Livia; Donini, Pierluigi; Schramke, Vera; Géli, Vincent; Ascenzioni, Fiorentina; Gilson, Eric

    2003-04-01

    The number of telomeric DNA repeats at chromosome ends is maintained around a mean value by a dynamic balance between elongation and shortening. In particular, proteins binding along the duplex part of telomeric DNA set the number of repeats by progressively limiting telomere growth. The paradigm of this counting mechanism is the Rap1 protein in Saccharomyces cerevisiae. We demonstrate here that a Rap1-independent mechanism regulates the number of yeast telomeric repeats (TG(1-3)) and of vertebrate repeats (T(2)AG(3)) when TEL1, a yeast ortholog of the human gene encoding the ATM kinase, is inactivated. In addition, we show that a T(2)AG(3)-only telomere can be formed and maintained in humanized yeast cells carrying a template mutation of the gene encoding the telomerase RNA, which leads to the synthesis of vertebrate instead of yeast repeats. Genetic and biochemical evidences indicate that this telomere is regulated in a Rap1-independent manner, both in TEL1 and in tel1Delta humanized yeast cells. Altogether, these findings shed light on multiple repeat-counting mechanisms, which may share critical features between lower and higher eukaryotes. PMID:12660175

  15. DNA-directed Polymerase Subunits Play a Vital Role in Human Telomeric Overhang Processing

    Diotti, Raffaella; Kalan, Sampada; Matveyenko, Anastasiya; Loayza, Diego

    2014-01-01

    Telomeres consist of TTAGGG repeats bound by the shelterin complex and end with a 3' overhang. In humans, telomeres shorten at each cell division, unless telomerase (TERT) is expressed and able to add telomeric repeats. For effective telomere maintenance, the DNA strand complementary to that made by telomerase must be synthesized. Recent studies have discovered a link between different activities necessary to process telomeres in the S-phase of the cell cycle in order to ref...

  16. hnRNP A2/B1 binds specifically to single stranded vertebrate telomeric repeat TTAGGGn.

    McKay, S.J.; Cooke, H

    1992-01-01

    We have previously isolated a protein from mouse liver nuclei that specifically binds to single stranded (TTAGGG)n repeats. TTAGGG is the telomeric repeats of mammals and we therefore named the new protein single stranded telomere binding protein (sTBP). Further studies now identify sTBP as heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 on the basis of amino acid sequence determination and antibody reactivity. A2 and B1 form a major part of the protein component of hnRNP particles and ...

  17. Mutant Telomeric Repeats in Yeast Can Disrupt the Negative Regulation of Recombination-Mediated Telomere Maintenance and Create an Alternative Lengthening of Telomeres-Like Phenotype▿

    Bechard, Laura H.; Butuner, Bilge D.; Peterson, George J.; McRae, Will; Topcu, Zeki; McEachern, Michael J.

    2008-01-01

    Some human cancers maintain telomeres using alternative lengthening of telomeres (ALT), a process thought to be due to recombination. In Kluyveromyces lactis mutants lacking telomerase, recombinational telomere elongation (RTE) is induced at short telomeres but is suppressed once telomeres are moderately elongated by RTE. Recent work has shown that certain telomere capping defects can trigger a different type of RTE that results in much more extensive telomere elongation that is reminiscent o...

  18. The human TTAGGG repeat factors 1 and 2 bind to a subset of interstitial telomeric sequences and satellite repeats

    Thomas Simonet; Elena Giulotto; Frederique Magdinier; Béatrice Horard; Pascal Barbry; Rainer Waldmann; Eric Gison; Laure-Emmanuelle Zaragosi; Claude Philippe; Kevin Lebrigand; Clémentine Schouteden; Adeline Augereau; Serge Bauwens; Jing Ye; Marco Santagostino

    2011-01-01

    The study of the proteins that bind to telomeric DNA in mammals has provided a deep understanding of the mech anisms involved in chromosome-end protection. However, very little is known on the binding of these proteins to nontelomeric DNA sequences. The TTAGGG DNA repeat proteins 1 and 2 (TRF1 and TRF2) bind to mammalian telomeres as part of the shelterin complex and are essential for maintaining chromosome end stability. In this study, we combined chromatin immunoprecipitation with high-throughput sequencing to map at high sensitivity and resolution the human chromosomal sites to which TRF1 and TRF2 bind. While most of the identified sequences correspond to telomeric regions, we showed that these two proteins also bind to extratelomeric sites. The vast majority of these extratelomeric sites contains interstitial telomeric sequences (or ITSs). However, we also identified non-iTS sites, which correspond to centromeric and pericentromeric satellite DNA. Interestingly, the TRF-binding sites are often located in the proximity of genes or within introns. We propose that TRF1 and TRF2 couple the functional state of telomeres to the long-range organization of chromosomes and gene regulation networks by binding to extratelomeric sequences.

  19. The Telomeric Repeats of Human Herpesvirus 6A (HHV-6A) Are Required for Efficient Virus Integration.

    Nina Wallaschek; Anirban Sanyal; Fabian Pirzer; Annie Gravel; Yasuko Mori; Louis Flamand; Kaufer, Benedikt B

    2016-01-01

    Human herpesvirus 6A (HHV-6A) and 6B (HHV-6B) are ubiquitous betaherpesviruses that infects humans within the first years of life and establishes latency in various cell types. Both viruses can integrate their genomes into telomeres of host chromosomes in latently infected cells. The molecular mechanism of viral integration remains elusive. Intriguingly, HHV-6A, HHV-6B and several other herpesviruses harbor arrays of telomeric repeats (TMR) identical to human telomere sequences at the ends of...

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

    Richard J Giannone

    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.

  1. Telomeric repeat-containing RNA (TERRA) constitutes a nucleoprotein component of extracellular inflammatory exosomes

    Wang, Zhuo; Deng, Zhong; Dahmane, Nadia; Tsai, Kevin; Wang, Pu; Williams, Dewight R.; Kossenkov, Andrew V.; Showe, Louise C.; Zhang, Rugang; Huang, Qihong; Conejo-Garcia, José R.; Lieberman, Paul M.

    2015-01-01

    Telomeric repeat-containing RNA (TERRA) has been identified as a telomere-associated regulator of chromosome end protection. Here, we report that TERRA can also be found in extracellular fractions that stimulate innate immune signaling. We identified extracellular forms of TERRA in mouse tumor and embryonic brain tissue, as well as in human tissue culture cell lines using RNA in situ hybridization. RNA-seq analyses revealed TERRA to be among the most highly represented transcripts in extracellular fractions derived from both normal and cancer patient blood plasma. Cell-free TERRA (cfTERRA) could be isolated from the exosome fractions derived from human lymphoblastoid cell line (LCL) culture media. cfTERRA is a shorter form (∼200 nt) of cellular TERRA and copurifies with CD63- and CD83-positive exosome vesicles that could be visualized by cyro-electron microscopy. These fractions were also enriched for histone proteins that physically associate with TERRA in extracellular ChIP assays. Incubation of cfTERRA-containing exosomes with peripheral blood mononuclear cells stimulated transcription of several inflammatory cytokine genes, including TNFα, IL6, and C-X-C chemokine 10 (CXCL10) Exosomes engineered with elevated TERRA or liposomes with synthetic TERRA further stimulated inflammatory cytokines, suggesting that exosome-associated TERRA augments innate immune signaling. These findings imply a previously unidentified extrinsic function for TERRA and a mechanism of communication between telomeres and innate immune signals in tissue and tumor microenvironments. PMID:26578789

  2. Telomeric repeat-containing RNA (TERRA) constitutes a nucleoprotein component of extracellular inflammatory exosomes.

    Wang, Zhuo; Deng, Zhong; Dahmane, Nadia; Tsai, Kevin; Wang, Pu; Williams, Dewight R; Kossenkov, Andrew V; Showe, Louise C; Zhang, Rugang; Huang, Qihong; Conejo-Garcia, José R; Lieberman, Paul M

    2015-11-17

    Telomeric repeat-containing RNA (TERRA) has been identified as a telomere-associated regulator of chromosome end protection. Here, we report that TERRA can also be found in extracellular fractions that stimulate innate immune signaling. We identified extracellular forms of TERRA in mouse tumor and embryonic brain tissue, as well as in human tissue culture cell lines using RNA in situ hybridization. RNA-seq analyses revealed TERRA to be among the most highly represented transcripts in extracellular fractions derived from both normal and cancer patient blood plasma. Cell-free TERRA (cfTERRA) could be isolated from the exosome fractions derived from human lymphoblastoid cell line (LCL) culture media. cfTERRA is a shorter form (∼200 nt) of cellular TERRA and copurifies with CD63- and CD83-positive exosome vesicles that could be visualized by cyro-electron microscopy. These fractions were also enriched for histone proteins that physically associate with TERRA in extracellular ChIP assays. Incubation of cfTERRA-containing exosomes with peripheral blood mononuclear cells stimulated transcription of several inflammatory cytokine genes, including TNFα, IL6, and C-X-C chemokine 10 (CXCL10) Exosomes engineered with elevated TERRA or liposomes with synthetic TERRA further stimulated inflammatory cytokines, suggesting that exosome-associated TERRA augments innate immune signaling. These findings imply a previously unidentified extrinsic function for TERRA and a mechanism of communication between telomeres and innate immune signals in tissue and tumor microenvironments. PMID:26578789

  3. NMR observation of T-tetrads in a parallel stranded DNA quadruplex formed by Saccharomyces cerevisiae telomere repeats.

    P.K. Patel; Hosur, R V

    1999-01-01

    We report here the NMR structure of the DNA sequence d-TGGTGGC containing two repeats of Saccharomyces cerevisiae telomere DNA which is unique in that it has a single thymine in the repeat sequence and the number of Gs can vary from one to three. The structure is a novel quadruplex incor-porating T-tetrads formed by symmetrical pairing of four Ts via O4-H3 H-bonds in a plane. This is in contrast to the previous results on other telomeric sequences which contained more than one T in the repeat...

  4. Visualization and quantitative analysis of extrachromosomal telomere-repeat DNA in individual human cells by Halo-FISH.

    Komosa, Martin; Root, Heather; Meyn, M Stephen

    2015-02-27

    Current methods for characterizing extrachromosomal nuclear DNA in mammalian cells do not permit single-cell analysis, are often semi-quantitative and frequently biased toward the detection of circular species. To overcome these limitations, we developed Halo-FISH to visualize and quantitatively analyze extrachromosomal DNA in single cells. We demonstrate Halo-FISH by using it to analyze extrachromosomal telomere-repeat (ECTR) in human cells that use the Alternative Lengthening of Telomeres (ALT) pathway(s) to maintain telomere lengths. We find that GM847 and VA13 ALT cells average ∼80 detectable G/C-strand ECTR DNA molecules/nucleus, while U2OS ALT cells average ∼18 molecules/nucleus. In comparison, human primary and telomerase-positive cells contain 300), range widely in length (200 kb) and are composed of primarily G- or C-strand telomere-repeat DNA. Halo-FISH enables, for the first time, the simultaneous analysis of ECTR DNA and chromosomal telomeres in a single cell. We find that ECTR DNA comprises ∼15% of telomere-repeat DNA in GM847 and VA13 cells, but <4% in U2OS cells. In addition to its use in ALT cell analysis, Halo-FISH can facilitate the study of a wide variety of extrachromosomal DNA in mammalian cells. PMID:25662602

  5. Detection of telomerase activity by combination of telomeric repeat amplification protocol and electrochemiluminescence assay

    Xiao Ming Zhou; Li Jia

    2008-01-01

    A highly sensitive telomerase detection method that combines telomeric repeat amplification protocol (TRAP) and magnetic beads based electrochemiluminescence (ECL) assay has been developed. Briefly, telomerase recognizes biotinylated telomerase synthesis primer (B-TS) and synthesizes extension products, which then serve as the templates for PCR amplification using B-TS as the forward primer and Iris-(2'2'-bipyridyl) ruthenium (TBR) labeled ACX (TBR-ACX) as the reversed primer. The amplified product is captured on streptavidin-coated paramagnetic beads and detected by ECL. Telomerase positive HeLa cells were used to validate the feasibility of the method. The experimental results showed down to 10 cancer cells can be detected easily. The method is a useful tool for telomerase activity analysis due to its sensitivity, rapidity, safety, high throughput, and low cost. It can be used for screening a large amount of clinical samples.

  6. Recombination-mediated lengthening of terminal telomeric repeats requires the Sgs1 DNA helicase

    Cohen, Haim; Sinclair, David A.

    2001-01-01

    The Saccharomyces cerevisiae SGS1 gene encodes a RecQ-like DNA helicase, human homologues of which are implicated in the genetic instability disorders, Bloom syndrome (BS), Rothmund-Thomson syndrome (RTS), and Werner syndrome (WS). Telomerase-negative yeast cells can recover from senescence via two recombinational telomere elongation pathways. The “type I” pathway generates telomeres with large blocks of telomeric and subtelomeric sequences and short terminal repea...

  7. Telomeric circles: universal players in telomere maintenance?

    Tomaska, Lubomir; Nosek, Jozef; Kramara, Juraj; Griffith, Jack D.

    2009-01-01

    To maintain linear DNA genomes, organisms have evolved numerous means of solving problems associated with DNA ends (telomeres), including telomere-associated retrotransposons, palindromes, hairpins, covalently bound proteins and the addition of arrays of simple DNA repeats. Telomeric arrays can be maintained through various mechanisms such as telomerase activity or recombination. The recombination-dependent maintenance pathways may include telomeric loops (t-loops) and telomeric circles (t-ci...

  8. Copy Numbers of Telomeric Repeat Sequences of Human Herpesvirus 6B in Clinical Isolates: Possibility of Mixed Infections

    KATO, Yuri; Ihira, Masaru; Umeda, Mami; Higashimoto, Yuki; Kawamura, Yoshiki; Ohashi, Masahiro; Ishi, Junichi; Yoshikawa, Tetsushi

    2014-01-01

    In order to determine whether mixed infections of human herpesvirus 6B (HHV-6B) occur in immunocompetent and immunocompromised individuals, we examined the copy numbers of telomeric repeat sequences (TRS) of clinical isolates. In clinical isolates obtained from patients with exanthem subitum caused by primary HHV-6B infection, PCR products with HHV-6B TRS ranging between 400 and 800 bp were amplified. PCR products of various sizes were amplified in four clinical isolates from drug-induced hyp...

  9. Reduction of telomeric repeats as a possible predictor for development of hepatocellular carcinoma: convenient evaluation by slot-blot analysis.

    Isokawa, O; Suda, T; Aoyagi, Y; Kawai, H; Yokota, T; Takahashi, T; Tsukada, K; Shimizu, T; Mori, S; Abe, Y; Suzuki, Y; Nomoto, M; Mita, Y; Yanagi, M; Igarashi, H; Asakura, H

    1999-08-01

    Hepatocellular carcinoma (HCC) mainly arises from the liver with chronic inflammation. Because telomere reduction reflects replicative history in somatic cells, we analyzed the possibility that liver tissues surrounding HCC consist of the cells carrying substantial reduction of telomere. We studied 20 HCC and surrounding noncancerous liver tissues (SL) obtained by surgical resection, and 10 laparoscopically obtained needle biopsy specimens of the liver with chronic inflammation including no overt HCC (CI). Five liver tissues without chronic liver diseases (ND) were also examined. Extracted genomic DNAs were blotted on a nylon membrane, and probed at first with radio-labeled d(TTAGGG)(3) and reprobed with radio-labeled d(CCT)(7). The intensity caused by d(TTAGGG)(3) was divided by that of d(CCT)(7). The ratio was defined as telomeric repeats content (TC). Dilution experiments reproducibly revealed almost the same TC. The reduction rate of telomere length through aging estimated by regression analysis of TC was 0.62% per year. Concomitant analyses of TC and average telomere length revealed that both values were significantly correlated (r =.45; P =.009). To compare TC in the liver with respect to chronic inflammation, the value was divided by TC in peripheral blood leukocytes (PBL) from the same donor. The ratio was defined as relative TC (RTC). There was a statistically significant decrease of RTC in CI compared with that in ND (P =.03). Furthermore, RTC in SL was significantly lower than that in CI (P =.0001). These observations suggest that RTC value in liver tissues may digitally indicate a replicative history of hepatocytes under chronic inflammation, and a risk of HCC development. PMID:10421648

  10. Telomere repeat DNA forms a large non-covalent complex with unique cohesive properties which is dissociated by Werner syndrome DNA helicase in the presence of replication protein A

    Ohsugi, Itaru; Tokutake, Yoshiki; Suzuki, Noriyuki; IDE, TOSHINORI; Sugimoto, Masanobu; Furuichi, Yasuhiro

    2000-01-01

    We describe the unique structural features of a large telomere repeat DNA complex (TRDC) of >20 kb generated by a simple PCR using (TTAGGG)4 and (CCCTAA)4 as both primers and templates. Although large, as determined by conventional agarose gel electrophoresis, the TRDC was found to consist of short single-stranded DNA telomere repeat units of between several hundred and 3000 bases, indicating that it is a non-covalent complex comprising short cohesive telomere repeat units. S1 nuclease digest...

  11. Characterization of telomeric repeats in metaphase chromosomes and interphase nuclei of Syrian Hamster Fibroblasts

    Solovjeva Liudmila V

    2012-09-01

    Full Text Available Abstract Background Rodents have been reported to contain large arrays of interstitial telomeric sequences (TTAGGGn (ITS located in pericentromeric heterochromatin. The relative sizes of telomeric sequences at the ends of chromosomes (TS and ITS in Syrian hamster (Mesocricetus auratus cells have not been evaluated yet, as well as their structural organization in interphase nuclei. Results FISH signal distribution analysis was performed on DAPI-banded metaphase chromosomes of Syrian hamster fibroblasts, and relative lengths of telomere signals were estimated. Besides well-distinguished FISH signals from ITS located on chromosomes ##2, 4, 14, 20 and X that we reported earlier, low-intensity FISH signals were visualized with different frequency of detection on all other metacentric chromosomes excluding chromosome #21. The analysis of 3D-distribution of TS in interphase nuclei demonstrated that some TS foci formed clearly distinguished associations (2–3 foci in a cluster in the nuclei of cells subjected to FISH or transfected with the plasmid expressing telomeric protein TRF1 fused with GFP. In G0 and G1/early S-phase, the average total number of GFP-TRF1 foci per nucleus was less than that of PNA FISH foci in the corresponding cell cycle phases suggesting that TRF1 overexpression might contribute to the fusion of neighboring telomeres. The mean total number of GFP-TRF1 and FISH foci per nucleus was increased during the transition from G0 to G1/early S-phase that might be the consequence of duplication of some TS. Conclusions The relative lengths of TS in Syrian hamster cells were found to be moderately variable. All but one metacentric chromosomes contain ITS in pericentromeric heterochromatin indicating that significant rearrangements of ancestral genome occurred in evolution. Visualization of GFP-TRF1 fibrils that formed bridges between distinct telomeric foci allowed suggesting that telomere associations observed in interphase cells are

  12. Guanine tetraplex topology of human telomere DNA is governed by the number of (TTAGGG) repeats

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

    2005-01-01

    Roč. 33, č. 18 (2005), s. 5851-5860. ISSN 0305-1048 R&D Projects: GA AV ČR(CZ) IAA4004201; GA MZd(CZ) NM7634 Institutional research plan: CEZ:AV0Z50040507 Keywords : quadruplexes * human telomere * DNA conformational properties Subject RIV: BO - Biophysics Impact factor: 7.552, year: 2005

  13. Novel Luminex Assay for Telomere Repeat Mass Does Not Show Well Position Effects Like qPCR.

    Muhammad G Kibriya

    Full Text Available Telomere length is a potential biomarker of aging and risk for age-related diseases. For measurement of relative telomere repeat mass (TRM, qPCR is typically used primarily due to its low cost and low DNA input. But the position of the sample on a plate often impacts the qPCR-based TRM measurement. Recently we developed a novel, probe-based Luminex assay for TRM that requires ~50ng DNA and involves no DNA amplification. Here we report, for the first time, a comparison among TRM measurements obtained from (a two singleplex qPCR assays (using two different primer sets, (b a multiplex qPCR assay, and (c our novel Luminex assay. Our comparison is focused on characterizing the effects of sample positioning on TRM measurement. For qPCR, DNA samples from two individuals (K and F were placed in 48 wells of a 96-well plate. For each singleplex qPCR assay, we used two plates (one for Telomere and one for Reference gene. For the multiplex qPCR and the Luminex assay, the telomere and the reference genes were assayed from the same well. The coefficient of variation (CV of the TRM for Luminex (7.2 to 8.4% was consistently lower than singleplex qPCR (11.4 to 14.9% and multiplex qPCR (19.7 to 24.3%. In all three qPCR assays the DNA samples in the left- and right-most columns showed significantly lower TRM than the samples towards the center, which was not the case for the Luminex assay (p = 0.83. For singleplex qPCR, 30.5% of the variation in TL was explained by column-to-column variation and 0.82 to 27.9% was explained by sample-to-sample variation. In contrast, only 5.8% of the variation in TRM for the Luminex assay was explained by column-to column variation and 50.4% was explained by sample-to-sample variation. Our novel Luminex assay for TRM had good precision and did not show the well position effects of the sample that were seen in all three of the qPCR assays that were tested.

  14. Telomeres and reproductive aging.

    Keefe, David L; Liu, Lin

    2009-01-01

    Infertility, miscarriage and aneuploid offspring increase with age in women, and meiotic dysfunction underlies reproductive aging. How aging disrupts meiotic function in women remains unclear, but as women increasingly delay having children, solving this problem becomes an urgent priority. Telomeres consist of a (TTAGGG)(n) repeated sequence and associated proteins at chromosome ends, mediate aging in mitotic cells and may also mediate aging during meiosis. Telomeres shorten both during DNA replication and from the response to oxidative DNA damage. Oocytes do not divide in adult mammals, but their precursors do replicate during fetal oogenesis; eggs ovulated from older females have traversed more mitotic cell cycles before entering meiosis during fetal oogenesis than eggs ovulated from younger females. Telomeres also would be expected to shorten from inefficient DNA repair of oxidative damage, because the interval between fetal oogenesis and ovulation is exceptionally prolonged in women. We have tested the hypothesis that telomere shortening disrupts meiosis by shortening telomeres experimentally in mice, which normally do not exhibit age-related meiotic dysfunction. Interestingly, mouse telomeres are much longer than human telomeres, but genetic or pharmacological shortening of mouse telomeres recapitulates in mice the human reproductive aging phenotype as the mouse telomeres reach the length of telomeres from older women. These observations led us to propose a telomere theory of reproductive aging. Moreover, chronological oxidative stress increases with reproductive aging, leading to DNA damage preferentially at (TTAGGG)(n) repeats. Finally, if telomeres shorten with aging, how do they reset across generations? Telomerase could not play a significant role in telomere elongation during early development, because this enzyme is not active until the blastocyst stage, well after the stage when telomere elongation takes place. Rather, telomeres lengthen during the

  15. Genetic Dissection of the Kluyveromyces lactis Telomere and Evidence for Telomere Capping Defects in TER1 Mutants with Long Telomeres

    Underwood, Dana H.; Carroll, Coleen; McEachern, Michael J.

    2004-01-01

    In the yeast Kluyveromyces lactis, the telomeres are composed of perfect 25-bp repeats copied from a 30-nucleotide RNA template defined by 5-nucleotide terminal repeats. A genetic dissection of the K. lactis telomere was performed by using mutant telomerase RNA (TER1) alleles to incorporate mutated telomeric repeats. This analysis has shown that each telomeric repeat contains several functional regions, some of which may physically overlap. Mutations in the terminal repeats of the template RN...

  16. Polychlorinated Biphenyls and Leukocyte Telomere Length: An Analysis of NHANES 1999–2002

    Franco Scinicariello; Buser, Melanie C.

    2015-01-01

    Polychlorinated biphenyls (PCBs) induce the expression of the proto-oncogene c-myc which has a role in cellular growth and proliferation programs. The c-myc up-regulates the telomerase reverse transcriptase which adds the telomeres repeating sequences to the chromosomal ends to compensate for the progressive loss of telomeric sequence. We performed multivariate linear regression to analyze the association of PCBs, polychlorinated dibenzo-p-dioxins, and 1,2,3,4,6,7,8-heptachlorodibenzofuran wi...

  17. G-Tetraplex-Induced FRET within Telomeric Repeat Sequences Using (Py) A-(Per) A as Energy Donor-Acceptor Pair.

    Kundu, Rajen

    2016-01-01

    G-tetraplex induced fluorescence resonance energy transfer (FRET) within telomeric repeat sequences has been studied using a nucleoside-tethered FRET pair embedded in the human telomeric G-quadruplex forming sequence (5'-A GGG TT(Py) A GGG TT(Per) A GGG TTA GGG-3', Py=pyrene, Per=perylene). Conformational change from a single strand to an anti-parallel G-quadruplex leads to FRET from energy donor ((Py) A) to acceptor ((Per) A). The distance between the FRET donor/acceptor partners was controlled by changing the number of G-quartet spacer units. The FRET efficiency decreases with increase in G-quartet units. Overall findings indicate that this could be further used for the development of FRET-based sensing and measurement techniques. PMID:26490798

  18. Telomere elongation chooses TERRA ALTernatives

    Arora, Rajika; Azzalin, Claus M.

    2015-01-01

    Alternative Lengthening of Telomeres (ALT) mechanisms allow telomerase-negative immortal cells to buffer replicative telomere shortening. ALT is naturally active in a number of human cancers and might be selected upon telomerase inactivation. ALT is thought to operate through homologous recombination (HR) occurring between telomeric repeats from independent chromosome ends. Indeed, suppression of a number of HR factors impairs ALT cell proliferation. Yet, how HR is initiated at ALT telomeres ...

  19. Telomere Restriction Fragment (TRF) Analysis

    Mender, Ilgen; Shay, Jerry W.

    2016-01-01

    While telomerase is expressed in ~90% of primary human tumors, most somatic tissue cells except transiently proliferating stem-like cells do not have detectable telomerase activity (Shay and Wright, 1996; Shay and Wright, 2001). Telomeres progressively shorten with each cell division in normal cells, including proliferating stem-like cells, due to the end replication (lagging strand synthesis) problem and other causes such as oxidative damage, therefore all somatic cells have limited cell proliferation capacity (Hayflick limit) (Hayflick and Moorhead, 1961; Olovnikov, 1973). The progressive telomere shortening eventually leads to growth arrest in normal cells, which is known as replicative senescence (Shay et al., 1991). Once telomerase is activated in cancer cells, telomere length is stabilized by the addition of TTAGGG repeats to the end of chromosomes, thus enabling the limitless continuation of cell division (Shay and Wright, 1996; Shay and Wright, 2001). Therefore, the link between aging and cancer can be partially explained by telomere biology. There are many rapid and convenient methods to study telomere biology such as Telomere Restriction Fragment (TRF), Telomere Repeat Amplification Protocol (TRAP) (Mender and Shay, 2015b) and Telomere dysfunction Induced Foci (TIF) analysis (Mender and Shay, 2015a). In this protocol paper we describe Telomere Restriction Fragment (TRF) analysis to determine average telomeric length of cells. Telomeric length can be indirectly measured by a technique called Telomere Restriction Fragment analysis (TRF). This technique is a modified Southern blot, which measures the heterogeneous range of telomere lengths in a cell population using the length distribution of the terminal restriction fragments (Harley et al., 1990; Ouellette et al., 2000). This method can be used in eukaryotic cells. The description below focuses on the measurement of human cancer cells telomere length. The principle of this method relies on the lack of

  20. Caenorhabditis elegans POT-2 telomere protein represses a mode of alternative lengthening of telomeres with normal telomere lengths

    Cheng, Chen; Shtessel, Ludmila; Brady, Megan M.; Ahmed, Shawn

    2012-01-01

    Canonical telomere repeats at chromosome termini can be maintained by a telomerase-independent pathway termed alternative lengthening of telomeres (ALT). Human cancers that survive via ALT can exhibit long and heterogeneous telomeres, although many telomerase-negative tumors possess telomeres of normal length. Here, we report that Caenorhabditis elegans telomerase mutants that survived via ALT possessed either long or normal telomere lengths. Most ALT strains displayed end-to-end chromosome f...

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

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

    1995-01-01

    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 line...

  2. Telomere Length Correlates with Life Span of Dog Breeds

    Laura J. Fick; Gordon H. Fick; Zichen Li; Eric Cao; Bo Bao; Doug Heffelfinger; Heidi G. Parker; Elaine A. Ostrander; Karl Riabowol

    2012-01-01

    Telomeric DNA repeats are lost as normal somatic cells replicate. When telomeres reach a critically short length, a DNA damage signal is initiated, inducing cell senescence. Some studies have indicated that telomere length correlates with mortality, suggesting that telomere length contributes to human life span; however, other studies report no correlation, and thus the issue remains controversial. Domestic dogs show parallels in telomere biology to humans, with similar telomere length, telom...

  3. Telomere dysfunction and chromosome instability

    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. Recombinogenic Telomeres in Diploid Sorex granarius (Soricidae, Eulipotyphla) Fibroblast Cells

    Zhdanova, N. S.; Draskovic, I.; Minina, J. M.; Karamysheva, T. V.; Novo, C. L.; Liu, W.-Y.; Porreca, R. M.; Gibaud, A.; Zvereva, M.E.; Skvortsov, D. A.; Rubtsov, N.B.; Londoño-Vallejo, A

    2014-01-01

    The telomere structure in the Iberian shrew Sorex granarius is characterized by unique, striking features, with short arms of acrocentric chromosomes carrying extremely long telomeres (up to 300 kb) with interspersed ribosomal DNA (rDNA) repeat blocks. In this work, we investigated the telomere physiology of S. granarius fibroblast cells and found that telomere repeats are transcribed on both strands and that there is no telomere-dependent senescence mechanism. Although telomerase activit...

  5. Diminished telomeric 3' overhangs are associated with telomere dysfunction in Hoyeraal-Hreidarsson syndrome.

    Noa Lamm

    Full Text Available BACKGROUND: Eukaryotic chromosomes end with telomeres, which in most organisms are composed of tandem DNA repeats associated with telomeric proteins. These DNA repeats are synthesized by the enzyme telomerase, whose activity in most human tissues is tightly regulated, leading to gradual telomere shortening with cell divisions. Shortening beyond a critical length causes telomere uncapping, manifested by the activation of a DNA damage response (DDR and consequently cell cycle arrest. Thus, telomere length limits the number of cell divisions and provides a tumor-suppressing mechanism. However, not only telomere shortening, but also damaged telomere structure, can cause telomere uncapping. Dyskeratosis Congenita (DC and its severe form Hoyeraal-Hreidarsson Syndrome (HHS are genetic disorders mainly characterized by telomerase deficiency, accelerated telomere shortening, impaired cell proliferation, bone marrow failure, and immunodeficiency. METHODOLOGY/PRINCIPAL FINDINGS: We studied the telomere phenotypes in a family affected with HHS, in which the genes implicated in other cases of DC and HHS have been excluded, and telomerase expression and activity appears to be normal. Telomeres in blood leukocytes derived from the patients were severely short, but in primary fibroblasts they were normal in length. Nevertheless, a significant fraction of telomeres in these fibroblasts activated DDR, an indication of their uncapped state. In addition, the telomeric 3' overhangs are diminished in blood cells and fibroblasts derived from the patients, consistent with a defect in telomere structure common to both cell types. CONCLUSIONS/SIGNIFICANCE: Altogether, these results suggest that the primary defect in these patients lies in the telomere structure, rather than length. We postulate that this defect hinders the access of telomerase to telomeres, thus causing accelerated telomere shortening in blood cells that rely on telomerase to replenish their telomeres

  6. The nature of telomere fusion and a definition of the critical telomere length in human cells

    Capper, Rebecca; Britt-Compton, Bethan; Tankimanova, Maira; Rowson, Jan; Letsolo, Boitelo; Man, Stephen; Haughton, Michele; Baird, Duncan M.

    2007-01-01

    The loss of telomere function can result in telomeric fusion events that lead to the types of genomic rearrangements, such as nonreciprocal translocations, that typify early-stage carcinogenesis. By using single-molecule approaches to characterize fusion events, we provide a functional definition of fusogenic telomeres in human cells. We show that approximately half of the fusion events contained no canonical telomere repeats at the fusion point; of those that did, the longest was 12.8 repeat...

  7. ATM Kinase Is Required for Telomere Elongation in Mouse and Human Cells

    Stella Suyong Lee

    2015-11-01

    Full Text Available Short telomeres induce a DNA damage response, senescence, and apoptosis, thus maintaining telomere length equilibrium is essential for cell viability. Telomerase addition of telomere repeats is tightly regulated in cells. To probe pathways that regulate telomere addition, we developed the ADDIT assay to measure new telomere addition at a single telomere in vivo. Sequence analysis showed telomerase-specific addition of repeats onto a new telomere occurred in just 48 hr. Using the ADDIT assay, we found that ATM is required for addition of new repeats onto telomeres in mouse cells. Evaluation of bulk telomeres, in both human and mouse cells, showed that blocking ATM inhibited telomere elongation. Finally, the activation of ATM through the inhibition of PARP1 resulted in increased telomere elongation, supporting the central role of the ATM pathway in regulating telomere addition. Understanding this role of ATM may yield new areas for possible therapeutic intervention in telomere-mediated disease.

  8. Progressive telomere shortening and telomerase reactivation during hepatocellular carcinogenesis.

    Miura, N; Horikawa, I; Nishimoto, A; Ohmura, H; Ito, H; Hirohashi, S; Shay, J W; Oshimura, M

    1997-01-01

    Telomeres shorten progressively with age in normal somatic cells in culture and in vivo. The maintenance of telomere length is assumed to be an obligatory step in the progression and immortalization of most human tumor cells. To understand the role of telomere dynamics in the development of hepatocellular carcinoma (HCC), we examined the length of terminal restriction fragment (TRF), as an indicator for telomere length, in HCC and surrounding tissues with chronic active hepatitis (CAH) or liver cirrhosis (LC). The study was performed in 12 hepatitis C virus (HCV) antibody-positive, 12 hepatitis B virus (HBV) antigen-positive tissues, and 4 tissue samples from virus-negative patients with HCC. The peak TRFs in all 3 types of HCC were significantly shorter than those of the surrounding tissues (i.e., LC or CAH). TRFs examined in one patient with atypical adenomatous hyperplasia (AAH) also was shortened. Thus, progressive TRF shortening occurs from normal to CAH to LC to HCC(AAH). Telomerase, an enzyme that adds repeated telomere sequences onto the chromosome ends and stabilizes telomere length in immortal cells, also was examined in tissues and detected in high levels almost exclusively in HCCs. Interestingly, the intensity of telomerase activity in the AAH case was similar to that of HCC. In addition, the telomerase activity of biopsy samples with a fine 21-gauge needle also was examined in 10 HCCs, 2 adenomatous hyperplasias (AHs), 2 LCs, and 2 CAHs. We found strong telomerase activity in all the HCCs and surprisingly in the 2 cases that were pathologically diagnosed as AH. Thus, the findings strongly suggest that persistent cell proliferation or rapid cell turnover through damage of hepatic cells result in a process of multistep hepatocellular carcinogenesis. Thus, progressive shortening of telomeres and the activation of telomerase may be a useful marker for the early detection of malignant progression in liver disease. PMID:9062581

  9. TERRA-reinforced association of LSD1 with MRE11 promotes processing of uncapped telomeres

    Antonio Porro; Sascha Feuerhahn; Joachim Lingner

    2014-01-01

    Telomeres protect chromosome ends from being recognized as sites of DNA damage. Upon telomere shortening or telomere uncapping induced by loss of telomeric repeat-binding factor 2 (TRF2), telomeres elicit a DNA-damage response leading to cellular senescence. Here, we show that following TRF2 depletion, the levels of the long noncoding RNA TERRA increase and LSD1, which binds TERRA, is recruited to telomeres. At uncapped telomeres, LSD1 associates with MRE11, one of the nucleases implicated in...

  10. Counting of Rif1p and Rif2p on Saccharomyces cerevisiae Telomeres Regulates Telomere Length†

    Levy, Daniel L.; Blackburn, Elizabeth H.

    2004-01-01

    Telomere length is negatively regulated by proteins of the telomeric DNA-protein complex. Rap1p in Saccharomyces cerevisiae binds the telomeric TG1-3 repeat DNA, and the Rap1p C terminus interacts with Rif1p and Rif2p. We investigated how these three proteins negatively regulate telomere length. We show that direct tethering of each Rif protein to a telomere shortens that telomere proportionally to the number of tethered molecules, similar to previously reported counting of Rap1p. Surprisingl...

  11. Telomere length correlates with life span of dog breeds.

    Fick, Laura J; Fick, Gordon H; Li, Zichen; Cao, Eric; Bao, Bo; Heffelfinger, Doug; Parker, Heidi G; Ostrander, Elaine A; Riabowol, Karl

    2012-12-27

    Telomeric DNA repeats are lost as normal somatic cells replicate. When telomeres reach a critically short length, a DNA damage signal is initiated, inducing cell senescence. Some studies have indicated that telomere length correlates with mortality, suggesting that telomere length contributes to human life span; however, other studies report no correlation, and thus the issue remains controversial. Domestic dogs show parallels in telomere biology to humans, with similar telomere length, telomere attrition, and absence of somatic cell telomerase activity. Using this model, we find that peripheral blood mononuclear cell (PBMC) telomere length is a strong predictor of average life span among 15 different breeds (p Dogs lose telomeric DNA ~10-fold faster than humans, which is similar to the ratio of average life spans between these species. Breeds with shorter mean telomere lengths show an increased probability of death from cardiovascular disease, which was previously correlated with short telomere length in humans. PMID:23260664

  12. Telomere and Telomerase Therapeutics in Cancer

    Xu, Yucheng; Goldkorn, Amir

    2016-01-01

    Telomerase is a reverse transcriptase capable of utilizing an integrated RNA component as a template to add protective tandem telomeric single strand DNA repeats, TTAGGG, to the ends of chromosomes. Telomere dysfunction and telomerase reactivation are observed in approximately 90% of human cancers; hence, telomerase activation plays a unique role as a nearly universal step on the path to malignancy. In the past two decades, multiple telomerase targeting therapeutic strategies have been pursued, including direct telomerase inhibition, telomerase interference, hTERT or hTERC promoter driven therapy, telomere-based approaches, and telomerase vaccines. Many of these strategies have entered clinical development, and some have now advanced to phase III clinical trials. In the coming years, one or more of these new telomerase-targeting drugs may be expected to enter the pharmacopeia of standard care. Here, we briefly review the molecular functions of telomerase in cancer and provide an update about the preclinical and clinical development of telomerase targeting therapeutics. PMID:27240403

  13. Telomere and Telomerase Therapeutics in Cancer

    Yucheng Xu

    2016-05-01

    Full Text Available Telomerase is a reverse transcriptase capable of utilizing an integrated RNA component as a template to add protective tandem telomeric single strand DNA repeats, TTAGGG, to the ends of chromosomes. Telomere dysfunction and telomerase reactivation are observed in approximately 90% of human cancers; hence, telomerase activation plays a unique role as a nearly universal step on the path to malignancy. In the past two decades, multiple telomerase targeting therapeutic strategies have been pursued, including direct telomerase inhibition, telomerase interference, hTERT or hTERC promoter driven therapy, telomere-based approaches, and telomerase vaccines. Many of these strategies have entered clinical development, and some have now advanced to phase III clinical trials. In the coming years, one or more of these new telomerase-targeting drugs may be expected to enter the pharmacopeia of standard care. Here, we briefly review the molecular functions of telomerase in cancer and provide an update about the preclinical and clinical development of telomerase targeting therapeutics.

  14. Telomere and Telomerase Therapeutics in Cancer.

    Xu, Yucheng; Goldkorn, Amir

    2016-01-01

    Telomerase is a reverse transcriptase capable of utilizing an integrated RNA component as a template to add protective tandem telomeric single strand DNA repeats, TTAGGG, to the ends of chromosomes. Telomere dysfunction and telomerase reactivation are observed in approximately 90% of human cancers; hence, telomerase activation plays a unique role as a nearly universal step on the path to malignancy. In the past two decades, multiple telomerase targeting therapeutic strategies have been pursued, including direct telomerase inhibition, telomerase interference, hTERT or hTERC promoter driven therapy, telomere-based approaches, and telomerase vaccines. Many of these strategies have entered clinical development, and some have now advanced to phase III clinical trials. In the coming years, one or more of these new telomerase-targeting drugs may be expected to enter the pharmacopeia of standard care. Here, we briefly review the molecular functions of telomerase in cancer and provide an update about the preclinical and clinical development of telomerase targeting therapeutics. PMID:27240403

  15. Telomeres and human health

    Bojesen, S E

    2013-01-01

    marginally-independently associated with risk of common disorders such as cardiovascular, pulmonary and neoplastic diseases. However, in sufficiently powered studies, short telomeres are repeatedly and independently found to be associated with increased risk of early death in the general population or in...

  16. Long telomeres produced by telomerase-resistant recombination are established from a single source and are subject to extreme sequence scrambling.

    Jianing Xu

    Full Text Available Considerable evidence now supports the idea that the moderate telomere lengthening produced by recombinational telomere elongation (RTE in a Kluyveromyces lactis telomerase deletion mutant occurs through a roll-and-spread mechanism. However, it is unclear whether this mechanism can account for other forms of RTE that produce much longer telomeres such as are seen in human alternative lengthening of telomere (ALT cells or in the telomerase-resistant type IIR "runaway" RTE such as occurs in the K. lactis stn1-M1 mutant. In this study we have used mutationally tagged telomeres to examine the mechanism of RTE in an stn1-M1 mutant both with and without telomerase. Our results suggest that the establishment stage of the mutant state in newly generated stn1-M1 ter1-Δ mutants surprisingly involves a first stage of sudden telomere shortening. Our data also show that, as predicted by the roll-and-spread mechanism, all lengthened telomeres in a newly established mutant cell commonly emerge from a single telomere source. However, in sharp contrast to the RTE of telomerase deletion survivors, we show that the RTE of stn1-M1 ter1-Δ cells produces telomeres whose sequences undergo continuous intense scrambling via recombination. While telomerase was not necessary for the long telomeres in stn1-M1 cells, its presence during their establishment was seen to interfere with the amplification of repeats via recombination, a result consistent with telomerase retaining its ability to add repeats during active RTE. Finally, we observed that the presence of active mismatch repair or telomerase had important influences on telomeric amplification and/or instability.

  17. Modulation of Telomeres in Alternative Lengthening of Telomeres Type I Like Human Cells by the Expression of Werner Protein and Telomerase

    Aisha Siddiqa; David Cavazos; Jeffery Chavez; Linda Long; Marciniak, Robert A.

    2012-01-01

    The alternative lengthening of telomeres (ALT) is a recombination-based mechanism of telomere maintenance activated in 5–20% of human cancers. In Saccharomyces cerevisiae, survivors that arise after inactivation of telomerase can be classified as type I or type II ALT. In type I, telomeres have a tandem array structure, with each subunit consisting of a subtelomeric Y′ element and short telomere sequence. Telomeres in type II have only long telomere repeats and require Sgs1, the S. cerevisiae...

  18. At Short Telomeres Tel1 Directs Early Replication and Phosphorylates Rif1

    Sridhar, Akila; Kedziora, Sylwia; Donaldson, Anne D.

    2014-01-01

    The replication time of Saccharomyces cerevisiae telomeres responds to TG1–3 repeat length, with telomeres of normal length replicating late during S phase and short telomeres replicating early. Here we show that Tel1 kinase, which is recruited to short telomeres, specifies their early replication, because we find a tel1Δ mutant has short telomeres that nonetheless replicate late. Consistent with a role for Tel1 in driving early telomere replication, initiation at a replication origin close t...

  19. Deletion of the major peroxiredoxin Tsa1 alters telomere length homeostasis

    LU, Jian; Vallabhaneni, Haritha; Yin, Jinhu; Liu, Yie

    2013-01-01

    Reactive oxygen species (ROS) are proposed to play a major role in telomere length alterations during aging. The mechanisms by which ROS disrupt telomeres remain unclear. In Saccharomyces cerevisiae, telomere DNA consists of TG(1-3) repeats, which are maintained primarily by telomerase. Telomere length maintenance can be modulated by the expression level of telomerase subunits and telomerase activity. Additionally, telomerase-mediated telomere repeat addition is negatively modulated by the le...

  20. Relative Telomere Length and Cognitive Decline in the Nurses’ Health Study

    Devore, Elizabeth E.; Prescott, Jennifer; De Vivo, Immaculata; Grodstein, Francine

    2011-01-01

    Telomeres are short DNA repeats on the ends of mammalian chromosomes, which can undergo incomplete replication leading to gradual shortening with each cell cycle. Age and oxidative stress are contributors to telomere shortening; thus, telomere length may be a composite measure of biologic aging, and a potential predictor of health status in older adults. We evaluated whether relative telomere length (the proportion of telomere repeat copy number to single gene copy number, using a real-time P...

  1. WRN loss induces switching of telomerase-independent mechanisms of telomere elongation.

    April Renee Sandy Gocha

    Full Text Available Telomere maintenance can occur in the presence of telomerase or in its absence, termed alternative lengthening of telomeres (ALT. ALT adds telomere repeats using recombination-based processes and DNA repair proteins that function in homologous recombination. Our previous work reported that the RecQ-like BLM helicase is required for ALT and that it unwinds telomeric substrates in vitro. WRN is also a RecQ-like helicase that shares many biochemical functions with BLM. WRN interacts with BLM, unwinds telomeric substrates, and co-localizes to ALT-associated PML bodies (APBs, suggesting that it may also be required for ALT processes. Using long-term siRNA knockdown of WRN in three ALT cell lines, we show that some, but not all, cell lines require WRN for telomere maintenance. VA-13 cells require WRN to prevent telomere loss and for the formation of APBs; Saos-2 cells do not. A third ALT cell line, U-2 OS, requires WRN for APB formation, however WRN loss results in p53-mediated apoptosis. In the absence of WRN and p53, U-2 OS cells undergo telomere loss for an intermediate number of population doublings (50-70, at which point they maintain telomere length even with the continued loss of WRN. WRN and the tumor suppressor BRCA1 co-localize to APBs in VA-13 and U-2 OS, but not in Saos-2 cells. WRN loss in U-2 OS is associated with a loss of BRCA1 from APBs. While the loss of WRN significantly increases telomere sister chromatid exchanges (T-SCE in these three ALT cell lines, loss of both BRCA1 and WRN does not significantly alter T-SCE. This work demonstrates that ALT cell lines use different telomerase-independent maintenance mechanisms that variably require the WRN helicase and that some cells can switch from one mechanism to another that permits telomere elongation in the absence of WRN. Our data suggest that BRCA1 localization may define these mechanisms.

  2. Telomeres, Early-Life Stress and Mental Illness

    Ridout, Samuel J.; Ridout, Kathryn K.; Kao, Hung-Teh; Carpenter, Linda L.; Philip, Noah S.; Tyrka, Audrey R.; Price, Lawrence H.

    2015-01-01

    Telomeres are structures of tandem TTAGGG repeats at the ends of chromosomes which preserve the encoding DNA by serving as a disposable brake to terminate DNA duplication during chromosome replication. In this process, the telomere itself shortens with each cell division, and can consequently be thought of as a cellular “clock” reflecting the age of a cell and the time until senescence. Telomere shortening, and changes in levels of telomerase, the enzyme that maintains telomeres, occur in the...

  3. Telomere lengthening to antagonize myocardial aging

    Cottage, Christopher Travis

    2012-01-01

    Aging is associated with onset and progression of cardiovascular disease resulting from changes at both cellular and molecular levels. Accumulation of senescent cells in the myocardium has been implicated in deterioration of hemodynamic performance and impaired reparative processes. Cellular senescence can be linked to oxidative stress and repeated cellular divisions, both of which lead to telomeric shortening. Telomeres are the distal ends of chromosomes that consist of nucleotide repeats th...

  4. Dynamics of Telomeres and Promyelocytic Leukemia Nuclear Bodies in a Telomerase-negative Human Cell Line

    Jegou, Thibaud; Chung, Inn; Heuvelman, Gerrit; Wachsmuth, Malte; Görisch, Sabine M.; Greulich-Bode, Karin M.; Boukamp, Petra; Lichter, Peter; Rippe, Karsten

    2009-01-01

    Telomerase-negative tumor cells maintain their telomeres via an alternative lengthening of telomeres (ALT) mechanism. This process involves the association of telomeres with promyelocytic leukemia nuclear bodies (PML-NBs). Here, the mobility of both telomeres and PML-NBs as well as their interactions were studied in human U2OS osteosarcoma cells, in which the ALT pathway is active. A U2OS cell line was constructed that had lac operator repeats stably integrated adjacent to the telomeres of ch...

  5. Control of telomere length by a trimming mechanism that involves generation of t-circles

    Hilda A Pickett; Cesare, Anthony J.; Johnston, Rebecca L; Neumann, Axel A.; Reddel, Roger R

    2009-01-01

    Telomere lengths are maintained in many cancer cells by the ribonucleoprotein enzyme telomerase but can be further elongated by increasing telomerase activity through the overexpression of telomerase components. We report here that increased telomerase activity results in increased telomere length that eventually reaches a plateau, accompanied by the generation of telomere length heterogeneity and the accumulation of extrachromosomal telomeric repeat DNA, principally in the form of telomeric ...

  6. TEL2, an essential gene required for telomere length regulation and telomere position effect in Saccharomyces cerevisiae.

    Runge, K W; Zakian, V A

    1996-01-01

    The DNA-protein complexes at the ends of linear eukaryotic chromosomes are called the telomeres. In Saccharomyces cerevisiae, telomeric DNA consists of a variable length of the short repeated sequence C1-3A. The length of yeast telomeres can be altered by mutation, by changing the levels of telomere binding proteins, or by increasing the amount of C1-3A DNA sequences. Cells bearing the tel1-1 or tel2-1 mutations, known previously to have short telomeres, did not respond to perturbations that ...

  7. In vitro generated antibodies specific for telomeric guanine-quadruplex DNA react with Stylonychia lemnae macronuclei

    Schaffitzel, Christiane; Berger, Imre; Postberg, Jan; Hanes, Jozef; Lipps, Hans J; Plückthun, Andreas

    2001-01-01

    Most eukaryotic telomeres contain a repeating motif with stretches of guanine residues that form a 3′-terminal overhang extending beyond the telomeric duplex region. The telomeric repeat of hypotrichous ciliates, d(T4G4), forms a 16-nucleotide 3′-overhang. Such sequences can adopt parallel-stranded as well as antiparallel-stranded quadruplex conformations in vitro. Although it has been proposed that guanine-quadruplex conformations may have important cellular roles including telomere function...

  8. Telomere Length Correlates with Life Span of Dog Breeds

    Laura J. Fick

    2012-12-01

    Full Text Available Telomeric DNA repeats are lost as normal somatic cells replicate. When telomeres reach a critically short length, a DNA damage signal is initiated, inducing cell senescence. Some studies have indicated that telomere length correlates with mortality, suggesting that telomere length contributes to human life span; however, other studies report no correlation, and thus the issue remains controversial. Domestic dogs show parallels in telomere biology to humans, with similar telomere length, telomere attrition, and absence of somatic cell telomerase activity. Using this model, we find that peripheral blood mononuclear cell (PBMC telomere length is a strong predictor of average life span among 15 different breeds (p < 0.0001, consistent with telomeres playing a role in life span determination. Dogs lose telomeric DNA ∼10-fold faster than humans, which is similar to the ratio of average life spans between these species. Breeds with shorter mean telomere lengths show an increased probability of death from cardiovascular disease, which was previously correlated with short telomere length in humans.

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

    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

  10. Telomere recombination and alternative telomere lengthening mechanisms

    Draskovic, I.; Londono Vallejo, A.

    2013-01-01

    Telomeres are nucleoprotein structures at the ends of linear chromosomes that protect them from being recognized as DNA double stranded breaks. Telomeres shorten with every cell division and in the absence of the checkpoint mechanisms critical telomere shortening leads to chromosome end fusions and

  11. Up-Regulation of Telomere-Binding Proteins, TRF1, TRF2, and TIN2 Is Related to Telomere Shortening during Human Multistep Hepatocarcinogenesis

    Oh, Bong-Kyeong; Kim, Young-Joo; Park, Chanil; Park, Young Nyun

    2005-01-01

    The telomeric repeat-binding factor 1 (TRF1), TRF2, and the TRF1-interacting nuclear protein 2 (TIN2) are involved in telomere maintenance. We describe the regulation of expression of these genes along with their relationship to telomere length in hepatocarcinogenesis. The transcriptional expression of these genes, TRF1 protein, and telomere length was examined in 9 normal livers, 14 chronic hepatitis, 24 liver cirrhosis, 5 large regenerative nodules, 14 low-grade dysplastic nodules (DNs), 7 ...

  12. Telomere attrition and Chk2 activation in human heart failure

    Oh, Hidemasa; Wang, Sam C.; Prahash, Arun; Sano, Motoaki; Moravec, Christine S.; Taffet, George E.; Michael, Lloyd H.; Youker, Keith A.; Entman, Mark L.; Schneider, Michael D.

    2003-01-01

    The “postmitotic” phenotype in adult cardiac muscle exhibits similarities to replicative senescence more generally and constitutes a barrier to effective restorative growth in heart disease. Telomere dysfunction is implicated in senescence and apoptotic signaling but its potential role in heart disorders is unknown. Here, we report that cardiac apoptosis in human heart failure is associated specifically with defective expression of the telomere repeat- binding factor TRF2, telomere shortening...

  13. Telomere-Mediated Plasmid Segregation in Saccharomyces Cerevisiae Involves Gene Products Required for Transcriptional Repression at Silencers and Telomeres

    Longtine, M. S.; Enomoto, S.; Finstad, S L; Berman, J

    1993-01-01

    Plasmids that contain Saccharomyces cerevisiae TG(1-3) telomere repeat sequences (TRS plasmids) segregate efficiently during mitosis. Mutations in histone H4 reduce the efficiency of TRS-mediated plasmid segregation, suggesting that chromatin structure is involved in this process. Sir2, Sir3 and Sir4 are required for the transcriptional repression of genes located at the silent mating type loci (HML and HMR) and at telomeres (telomere position effect) and are also involved in the segregation ...

  14. Factors that influence telomeric oxidative base damage and repair by DNA glycosylase OGG1

    Rhee, David B; Ghosh, Avik; Lu, Jian; Bohr, Vilhelm A; Liu, Yie

    2011-01-01

    -telomeric double-stranded substrates. In addition, telomere repeat binding factors TRF1 and TRF2 do not impair OGG1 incision activity. Yet, 8-oxodG in some telomere structures (e.g., fork-opening, 3'-overhang, and D-loop) were less effectively excised by OGG1, depending upon its position in these substrates...

  15. Telomerers rolle i cancer

    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...

  16. Defective repair of uracil causes telomere defects in mouse hematopoietic cells.

    Vallabhaneni, Haritha; Zhou, Fang; Maul, Robert W; Sarkar, Jaya; Yin, Jinhu; Lei, Ming; Harrington, Lea; Gearhart, Patricia J; Liu, Yie

    2015-02-27

    Uracil in the genome can result from misincorporation of dUTP instead of dTTP during DNA synthesis, and is primarily removed by uracil DNA glycosylase (UNG) during base excision repair. Telomeres contain long arrays of TTAGGG repeats and may be susceptible to uracil misincorporation. Using model telomeric DNA substrates, we showed that the position and number of uracil substitutions of thymine in telomeric DNA decreased recognition by the telomere single-strand binding protein, POT1. In primary mouse hematopoietic cells, uracil was detectable at telomeres, and UNG deficiency further increased uracil loads and led to abnormal telomere lengthening. In UNG-deficient cells, the frequencies of sister chromatid exchange and fragility in telomeres also significantly increased in the absence of telomerase. Thus, accumulation of uracil and/or UNG deficiency interferes with telomere maintenance, thereby underscoring the necessity of UNG-initiated base excision repair for the preservation of telomere integrity. PMID:25572391

  17. Mec1p associates with functionally compromised telomeres

    Hector, Ronald E; Ray, Alo; Chen, Bo-Ruei; Shtofman, Rebecca; Berkner, Kathleen L.; Runge, Kurt W.

    2012-01-01

    In many organisms, telomere DNA consists of simple sequence repeat tracts that are required to protect the chromosome end. In the yeast Saccharomyces cerevisiae, tract maintenance requires two checkpoint kinases of the ATM family, Tel1p and Mec1p. Previous work has shown that Tel1p is recruited to functional telomeres with shorter repeat tracts to promote telomerase-mediated repeat addition, but the role of Mec1p is unknown. We found that Mec1p telomere association was detected as cells senes...

  18. The human telomere

    Moyzis, R.K.

    1989-01-01

    An ultimate goal of human genetics is the generation of a complete physical and ''functional'' map of the human genome. Twenty-five percent of human DNA, however, consists of repetitive DNA sequences. These repetitive DNA sequences are thought to arise by many mechanisms, from direct sequence amplification by the unequal recombination of homologous DNA regions to the reverse flow of genetic information. A general outline of the chromosomal organization of these repetitive sequences will be discussed. Our working hypothesis is that certain classes of human repetitive DNA sequences ''encode'' the information necessary for defining long-range genomic structure. Evidence will be presented that the first goal of this research, the identification and cloning of the human telomere, has been achieved. A human repetitive DNA library was constructed from randomly sheared, reassociated, and oligo(G/center dot/C)-tailed DNA, a method that minimizes the potential loss of sequences devoid of a given restriction enzyme site. Sequences too large to clone efficiently in cosmid or /lambda/ vectors, such as centromeric repeats, or telomeric sequences with an end incompatible for cloning, should be present in this library. In order to isolate highly conserved repetitive DNA sequences, this library was screened with radiolabeled hamster Cot50 repetitive DNA. Two clones, containing tandem arrays of the sequence (TTAGGG), were isolated by this method. 30 refs., 1 fig., 2 tabs.

  19. Telomerase and telomeres : From basic biology to cancer treatment

    Helder, MN; Wisman, GBA; van der Zee, AGJ

    2002-01-01

    The limited capacity to divide is one of the major differences between normal somatic cells and cancerous cells. This finite life span' of somatic cells is closely linked to loss of telomeric DNA at telomeres, the 'chromosome caps' consisting of repeated (TTAGGG) sequences. In more than 85% of advan

  20. Functional interaction between telomere protein TPP1 and telomerase

    Zaug, Arthur J.; Podell, Elaine R.; Nandakumar, Jayakrishnan; Cech, Thomas R.

    2010-01-01

    Human chromosome end-capping and telomerase regulation require POT1 (Protection of Telomeres 1) and TPP1 proteins, which bind to the 3′ ssDNA extension of human telomeres. POT1–TPP1 binding to telomeric DNA activates telomerase repeat addition processivity. We now provide evidence that this POT1–TPP1 activation requires specific interactions with telomerase, rather than it being a DNA substrate-specific effect. First, telomerase from the fish medaka, which extends the same telomeric DNA prime...

  1. Telomeric overhang length determines structural dynamics and accessibility to telomerase and ALT associated proteins

    Hwang, Helen; Kreig, Alex; Calvert, Jacob; Lormand, Justin; Kwon, Yongho; Daley, James M.; Sung, Patrick; Opresko, Patricia L.; Myong, Sua

    2014-01-01

    The G-rich single stranded DNA at the 3′ end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single molecule fluorescence spectroscopy we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compa...

  2. Expansion of Interstitial Telomeric Sequences in Yeast.

    Aksenova, Anna Y; Han, Gil; Shishkin, Alexander A; Volkov, Kirill V; Mirkin, Sergei M

    2015-11-24

    Telomeric repeats located within chromosomes are called interstitial telomeric sequences (ITSs). They are polymorphic in length and are likely hotspots for initiation of chromosomal rearrangements that have been linked to human disease. Using our S. cerevisiae system to study repeat-mediated genome instability, we have previously shown that yeast telomeric (Ytel) repeats induce various gross chromosomal rearrangements (GCR) when their G-rich strands serve as the lagging strand template for replication (G orientation). Here, we show that interstitial Ytel repeats in the opposite C orientation prefer to expand rather than cause GCR. A tract of eight Ytel repeats expands at a rate of 4 × 10(-4) per replication, ranking them among the most expansion-prone DNA microsatellites. A candidate-based genetic analysis implicates both post-replication repair and homologous recombination pathways in the expansion process. We propose a model for Ytel repeat expansions and discuss its applications for genome instability and alternative telomere lengthening (ALT). PMID:26586439

  3. Modulation of Telomeres in Alternative Lengthening of Telomeres Type I Like Human Cells by the Expression of Werner Protein and Telomerase

    Aisha Siddiqa

    2012-01-01

    Full Text Available The alternative lengthening of telomeres (ALT is a recombination-based mechanism of telomere maintenance activated in 5–20% of human cancers. In Saccharomyces cerevisiae, survivors that arise after inactivation of telomerase can be classified as type I or type II ALT. In type I, telomeres have a tandem array structure, with each subunit consisting of a subtelomeric Y′ element and short telomere sequence. Telomeres in type II have only long telomere repeats and require Sgs1, the S. cerevisiae RecQ family helicase. We previously described the first human ALT cell line, AG11395, that has a telomere structure similar to type I ALT yeast cells. This cell line lacks the activity of the Werner syndrome protein, a human RecQ helicase. The telomeres in this cell line consist of tandem repeats containing SV40 DNA, including the origin of replication, and telomere sequence. We investigated the role of the SV40 origin of replication and the effects of Werner protein and telomerase on telomere structure and maintenance in AG11395 cells. We report that the expression of Werner protein facilitates the transition in human cells of ALT type I like telomeres to type II like telomeres in some aspects. These findings have implications for the diagnosis and treatment of cancer.

  4. Cohesin SMC1beta protects telomeres in meiocytes.

    Adelfalk, Caroline; Janschek, Johannes; Revenkova, Ekaterina; Blei, Cornelia; Liebe, Bodo; Göb, Eva; Alsheimer, Manfred; Benavente, Ricardo; de Boer, Esther; Novak, Ivana; Höög, Christer; Scherthan, Harry; Jessberger, Rolf

    2009-10-19

    Meiosis-specific mammalian cohesin SMC1beta is required for complete sister chromatid cohesion and proper axes/loop structure of axial elements (AEs) and synaptonemal complexes (SCs). During prophase I, telomeres attach to the nuclear envelope (NE), but in Smc1beta(-/-) meiocytes, one fifth of their telomeres fail to attach. This study reveals that SMC1beta serves a specific role at telomeres, which is independent of its role in determining AE/SC length and loop extension. SMC1beta is necessary to prevent telomere shortening, and SMC3, present in all known cohesin complexes, properly localizes to telomeres only if SMC1beta is present. Very prominently, telomeres in Smc1beta(-/-) spermatocytes and oocytes loose their structural integrity and suffer a range of abnormalities. These include disconnection from SCs and formation of large telomeric protein-DNA extensions, extended telomere bridges between SCs, ring-like chromosomes, intrachromosomal telomeric repeats, and a reduction of SUN1 foci in the NE. We suggest that a telomere structure protected from DNA rearrangements depends on SMC1beta. PMID:19841137

  5. Telomerase activity and telomere length in human hepatocellular carcinoma.

    Huang, G T; Lee, H S; Chen, C H; Chiou, L L; Lin, Y W; Lee, C Z; Chen, D S; Sheu, J C

    1998-11-01

    Telomerase activity is activated and telomere length altered in various types of cancers, including hepatocellular carcinoma (HCC). A total of 39 HCC tissues and the corresponding non-tumour livers were analysed and correlated with clinical parameters. Telomere length was determined by terminal restriction fragment assay, and telomerase activity was assayed by telomeric repeat amplification protocol. Telomerase activity was positive in 24 of the 39 tumour tissues (1.15-285.13 total product generated (TPG) units) and in six of the 39 non-tumour liver tissues (1.05-1.73 TPG units). In the 28 cases analysed for telomere length, telomere length was shortened in 11 cases, lengthened in six cases, and unaltered in 11 cases compared with non-tumour tissues. Neither telomere length nor telomerase activity was correlated to any clinical parameters. PMID:10023320

  6. Activity of telomerase and telomeric length in Apis mellifera.

    Korandová, Michala; Frydrychová, Radmila Čapková

    2016-06-01

    Telomerase is an enzyme that adds repeats of DNA sequences to the ends of chromosomes, thereby preventing their shortening. Telomerase activity is associated with proliferative status of cells, organismal development, and aging. We report an analysis of telomerase activity and telomere length in the honeybee, Apis mellifera. Telomerase activity was found to be regulated in a development and caste-specific manner. During the development of somatic tissues of larval drones and workers, telomerase activity declined to 10 % of its level in embryos and remained low during pupal and adult stages but was upregulated in testes of late pupae, where it reached 70 % of the embryo level. Upregulation of telomerase activity was observed in the ovaries of late pupal queens, reaching 160 % of the level in embryos. Compared to workers and drones, queens displayed higher levels of telomerase activity. In the third larval instar of queens, telomerase activity reached the embryo level, and an enormous increase was observed in adult brains of queens, showing a 70-fold increase compared to a brain of an adult worker. Southern hybridization of terminal TTAGG fragments revealed a high variability of telomeric length between different individuals, although the same pattern of hybridization signals was observed in different tissues of each individual. PMID:26490169

  7. Telomerer og telomerase

    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...

  8. Telomeres: Hallmarks of radiosensitivity

    Ayouaz, A.; Raynaud, C.; Heride, C.; Revaud, D.; Sabatier, L. [CEA, DSV, IRCM/SRO, F-92265 Fontenay Aux Roses (France)

    2008-07-01

    Telomeres are the very ends of the chromosomes. They can be seen as natural double-strand breaks (DSB), specialized structures which prevent DSB repair and activation of DNA damage checkpoints. In somatic cells, attrition of telomeres occurs after each cell division until replicative senescence. In the absence of telomerase, telomeres shorten due to incomplete replication of the lagging strand at the very end of chromosome termini. Moreover, oxidative stress and accumulating reactive oxygen species (ROS) lead to an increased telomere shortening due to a less efficient repair of SSB in telomeres. The specialized structures at telomeres include proteins involved in both telomere maintenance and DNA repair. However when a telomere is damaged and has to be repaired, those proteins might fail to perform an accurate repair of the damage.This is the starting point of this article in which we first summarize the well-established relationships between DNA repair processes and maintenance of functional telomeres. We then examine how damaged telomeres would be processed, and show that irradiation alters telomere maintenance leading to possibly dramatic consequences. Our point is to suggest that those consequences are not restricted to the short term effects such as increased radiation-induced cell death. On the contrary, we postulate that the major impact of the loss of telomere integrity might occur in the long term, during multistep carcinogenesis. Its major role would be to act as an amplifying event unmasking in one single step recessive radiation-induced mutations among thousands of genes and providing cellular proliferative advantage. Moreover, the chromosomal instability generated by damaged telomeres will favour each step of the transformation from normal to fully transformed cells. (authors)

  9. Telomeric RNAs are essential to maintain telomeres.

    Montero, Juan José; López de Silanes, Isabel; Graña, Osvaldo; Blasco, Maria A

    2016-01-01

    Telomeres are transcribed generating long non-coding RNAs known as TERRA. Deciphering the role of TERRA has been one of the unsolved issues of telomere biology in the past decade. This has been, in part, due to lack of knowledge on the TERRA loci, thus preventing functional genetic studies. Here, we describe that long non-coding RNAs with TERRA features are transcribed from the human 20q and Xp subtelomeres. Deletion of the 20q locus by using the CRISPR-Cas9 technology causes a dramatic decrease in TERRA levels, while deletion of the Xp locus does not result in decreased TERRA levels. Strikingly, 20q-TERRA ablation leads to dramatic loss of telomere sequences and the induction of a massive DNA damage response. These findings identify chromosome 20q as a main TERRA locus in human cells and represent the first demonstration in any organism of the essential role of TERRA in the maintenance of telomeres. PMID:27531349

  10. Telomere dysfunction and chromothripsis.

    Ernst, Aurélie; Jones, David T W; Maass, Kendra K; Rode, Agata; Deeg, Katharina I; Jebaraj, Billy Michael Chelliah; Korshunov, Andrey; Hovestadt, Volker; Tainsky, Michael A; Pajtler, Kristian W; Bender, Sebastian; Brabetz, Sebastian; Gröbner, Susanne; Kool, Marcel; Devens, Frauke; Edelmann, Jennifer; Zhang, Cindy; Castelo-Branco, Pedro; Tabori, Uri; Malkin, David; Rippe, Karsten; Stilgenbauer, Stephan; Pfister, Stefan M; Zapatka, Marc; Lichter, Peter

    2016-06-15

    Chromothripsis is a recently discovered form of genomic instability, characterized by tens to hundreds of clustered DNA rearrangements resulting from a single dramatic event. Telomere dysfunction has been suggested to play a role in the initiation of this phenomenon, which occurs in a large number of tumor entities. Here, we show that telomere attrition can indeed lead to catastrophic genomic events, and that telomere patterns differ between cells analyzed before and after such genomic catastrophes. Telomere length and telomere stabilization mechanisms diverge between samples with and without chromothripsis in a given tumor subtype. Longitudinal analyses of the evolution of chromothriptic patterns identify either stable patterns between matched primary and relapsed tumors, or loss of the chromothriptic clone in the relapsed specimen. The absence of additional chromothriptic events occurring between the initial tumor and the relapsed tumor sample points to telomere stabilization after the initial chromothriptic event which prevents further shattering of the genome. PMID:26856307

  11. PML body meets telomere

    Chung, Inn; Osterwald, Sarah; Deeg, Katharina I.; Rippe, Karsten

    2012-01-01

    The unlimited proliferation potential of cancer cells requires the maintenance of their telomeres. This is frequently accomplished by reactivation of telomerase. However, in a significant fraction of tumors an alternative lengthening of telomeres (ALT) mechanism is active. The molecular mechanism of the ALT pathway remains elusive. In particular, the role of characteristic complexes of promyelocytic leukemia nuclear bodies (PML-NBs) with telomeres, the ALT-associated PML-NBs (APBs), is curren...

  12. Single Molecule Studies of Physiologically Relevant Telomeric Tails Reveal POT1 Mechanism for Promoting G-quadruplex Unfolding*

    Wang, Hong; Nora, Gerald J.; Ghodke, Harshad; Opresko, Patricia L.

    2010-01-01

    Human telomeres are composed of duplex TTAGGG repeats and a 3′ single-stranded DNA tail. The telomeric DNA is protected and regulated by the shelterin proteins, including the protection of telomeres 1 (POT1) protein that binds telomeric single-stranded DNA. The single-stranded tail can fold into G-quadruplex (G4) DNA. Both POT1 and G4 DNA play important roles in regulating telomere length homeostasis. To date, most studies have focused on individual quadruplexes formed by four TTAGGG repeats....

  13. Direct Single-Stranded DNA Binding by Teb1 Mediates the Recruitment of Tetrahymena thermophila Telomerase to Telomeres

    Upton, Heather E.; Hong, Kyungah; Collins, Kathleen

    2014-01-01

    The eukaryotic reverse transcriptase telomerase copies its internal RNA template to synthesize telomeric DNA repeats at chromosome ends in balance with sequence loss during cell proliferation. Previous work has established several factors involved in telomerase recruitment to telomeres in yeast and mammalian cells; however, it remains unclear what determines the association of telomerase with telomeres in other organisms. Here we investigate the cell cycle dependence of telomere binding by ea...

  14. Sde2: A novel nuclear protein essential for telomeric silencing and genomic stability in Schizosaccharomyces pombe

    Sugioka-Sugiyama, Rie [Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Initiative for the Promotion of Young Scientists' Independent Research, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Sugiyama, Tomoyasu, E-mail: sugiyamt@biol.tsukuba.ac.jp [Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Initiative for the Promotion of Young Scientists' Independent Research, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012 (Japan)

    2011-03-18

    Research highlights: {yields} Sde2 is essential for telomere silencing. {yields} Sde2 is involved in the maintenance of genomic stability. {yields} Sde2 promotes the recruitment of SHREC, a histone deacetylase complex, to telomeres. -- Abstract: Telomeres, specialized domains assembled at the ends of linear chromosomes, are essential for genomic stability in eukaryotes. The formation and maintenance of telomeres are governed by numerous factors such as telomeric repeats, telomere-binding proteins, heterochromatin proteins, and telomerase. Here, we report Sde2, a novel nuclear protein essential for telomeric silencing and genomic stability in the fission yeast Schizosaccharomyces pombe. A deficiency in sde2 results in the derepression of the ura4{sup +} gene inserted near telomeric repeats, and the noncoding transcripts from telomeric regions accumulate in sde2{Delta} cells. The loss of Sde2 function compromises transcriptional silencing at telomeres, and this silencing defect is accompanied by increased levels of acetylated histone H3K14 and RNA polymerase II occupancy at telomeres as well as reduced recruitment of the SNF2 ATPase/histone deacetylase-containing complex SHREC to telomeres. Deletion of sde2 also leads to a higher frequency of mitotic minichromosome loss, and sde2{Delta} cells often form asci that contain spores in abnormal numbers, shapes, or both. In addition, sde2{Delta} cells are highly sensitive to several stresses, including high/low temperatures, bleomycin, which induces DNA damage, and thiabendazole, a microtubule-destabilizing agent. Furthermore, Sde2 genetically interacts with the telomere regulators Taz1, Pof3, and Ccq1. These findings demonstrate that Sde2 cooperates with other telomere regulators to maintain functional telomeres, thereby preventing genomic instability.

  15. Sde2: A novel nuclear protein essential for telomeric silencing and genomic stability in Schizosaccharomyces pombe

    Research highlights: → Sde2 is essential for telomere silencing. → Sde2 is involved in the maintenance of genomic stability. → Sde2 promotes the recruitment of SHREC, a histone deacetylase complex, to telomeres. -- Abstract: Telomeres, specialized domains assembled at the ends of linear chromosomes, are essential for genomic stability in eukaryotes. The formation and maintenance of telomeres are governed by numerous factors such as telomeric repeats, telomere-binding proteins, heterochromatin proteins, and telomerase. Here, we report Sde2, a novel nuclear protein essential for telomeric silencing and genomic stability in the fission yeast Schizosaccharomyces pombe. A deficiency in sde2 results in the derepression of the ura4+ gene inserted near telomeric repeats, and the noncoding transcripts from telomeric regions accumulate in sde2Δ cells. The loss of Sde2 function compromises transcriptional silencing at telomeres, and this silencing defect is accompanied by increased levels of acetylated histone H3K14 and RNA polymerase II occupancy at telomeres as well as reduced recruitment of the SNF2 ATPase/histone deacetylase-containing complex SHREC to telomeres. Deletion of sde2 also leads to a higher frequency of mitotic minichromosome loss, and sde2Δ cells often form asci that contain spores in abnormal numbers, shapes, or both. In addition, sde2Δ cells are highly sensitive to several stresses, including high/low temperatures, bleomycin, which induces DNA damage, and thiabendazole, a microtubule-destabilizing agent. Furthermore, Sde2 genetically interacts with the telomere regulators Taz1, Pof3, and Ccq1. These findings demonstrate that Sde2 cooperates with other telomere regulators to maintain functional telomeres, thereby preventing genomic instability.

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

    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.

  17. A high rate of telomeric sister chromatid exchange occurs in chronic lymphocytic leukaemia B-cells.

    Medves, Sandrine; Auchter, Morgan; Chambeau, Laetitia; Gazzo, Sophie; Poncet, Delphine; Grangier, Blandine; Verney, Aurélie; Moussay, Etienne; Ammerlaan, Wim; Brisou, Gabriel; Morjani, Hamid; Géli, Vincent; Palissot, Valérie; Berchem, Guy; Salles, Gilles; Wenner, Thomas

    2016-07-01

    Cancer cells protect their telomere ends from erosion through reactivation of telomerase or by using the Alternative Lengthening of Telomere (ALT) mechanism that depends on homologous recombination. Chronic lymphocytic leukaemia (CLL) B cells are characterized by almost no telomerase activity, shelterin deregulation and telomere fusions. To characterize telomeric maintenance mechanisms in B-CLL patients, we measured their telomere length, telomerase expression and the main hallmarks of the ALT activity i.e. C-circle concentration, an extra-chromosomal telomere repeat (ECTR), and the level of telomeric sister chromatid exchange (T-SCE) rate. Patients showed relative homogenous telomere length although almost no TERT transcript and nearly no C-circle were evidenced. Nevertheless, compared with normal B cells, B-CLL cells showed an increase in T-SCE rate that was correlated with a strong down-regulation of the topoisomerase III alpha (TOP3A) expression, involved in the dissolution of Holliday Junctions (HJ), together with an increased expression of SLX1A, SLX4, MUS81 and GEN1, involved in the resolution of HJ. Altogether, our results suggest that the telomere maintenance mechanism of B-CLL cells do not preferentially use telomerase or ALT. Rather, the rupture of the dissolvasome/resolvasome balance may increase telomere shuffling that could homogenize telomere length, slowing telomere erosion in this disease. PMID:26970083

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

    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.

  19. Alternative lengthening of telomeres: recurrent cytogenetic aberrations and chromosome stability under extreme telomere dysfunction.

    Sakellariou, Despoina; Chiourea, Maria; Raftopoulou, Christina; Gagos, Sarantis

    2013-11-01

    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. PMID:24339742

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

    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.

  1. Short Telomeres Initiate Telomere Recombination in Primary and Tumor Cells

    Morrish, Tammy A.; Greider, Carol W

    2009-01-01

    Human tumors that lack telomerase maintain telomeres by alternative lengthening mechanisms. Tumors can also form in telomerase-deficient mice; however, the genetic mechanism responsible for tumor growth without telomerase is unknown. In yeast, several different recombination pathways maintain telomeres in the absence of telomerase-some result in telomere maintenance with minimal effects on telomere length. To examine non-telomerase mechanisms for telomere maintenance in mammalian cells, we us...

  2. Telomere Maintenance through Spatial Control of Telomeric Proteins▿

    Chen, Liuh-Yow; Liu, Dan; Songyang, Zhou

    2007-01-01

    The six human telomeric proteins TRF1, TRF2, RAP1, TIN2, POT1, and TPP1 can form a complex called the telosome/shelterin, which is required for telomere protection and length control. TPP1 has been shown to regulate both POT1 telomere localization and telosome assembly through its binding to TIN2. It remains to be determined where such interactions take place and whether cellular compartmentalization of telomeric proteins is important for telomere maintenance. We systematically investigated h...

  3. Human Rap1 modulates TRF2 attraction to telomeric DNA

    Janoušková Eliška; Nečasová Ivona; Pavloušková Jana; Zimmermann Michal; Hluchý Milan; Marini Palomeque María Victoria; Nováková Monika; Hofr Ctirad

    2015-01-01

    More than two decades of genetic research have identified and assigned main biological functions of shelterin proteins that safeguard telomeres. However, a molecular mechanism of how each protein subunit contributes to the protecting function of the whole shelterin complex remains elusive. Human Repressor activator protein 1 (Rap1) forms a multifunctional complex with Telomeric Repeat binding Factor 2 (TRF2). Rap1-TRF2 complex is a critical part of shelterin as it suppresses homology-directed...

  4. P53与端粒重复序列结合蛋白质1的体外相互作用%The molecular interaction between P53 and telomeric repeat binding protein 1 in vitro

    李玲; 张波; 邹万忠; 郑杰

    2004-01-01

    目的:通过分析端粒主要结合蛋白中端粒重复序列结合蛋白质1(Telomeric repeat binding protein 1,TRBP1)与P53的体外结合,探讨P53通过端粒途径调节细胞增殖、衰老和凋亡的分子机制.方法:谷胱甘肽S转移酶(glutathione S-transferase,GST)和人P53-GST融合蛋白经大肠杆菌表达、谷胱甘肽-SepharoseTM4B纯化后,和人乳腺癌细胞MCF-7细胞蛋白进行体外结合反应(pull down),Western blot检测反应物中P53和TRBP1的结合.融合蛋白中人P53包括野生型(1~393)、C端缺失体P53 N5(2~293)、N端缺失体P53 2C(95~393)、175单个氨基酸突变体P53 R175H(R→H).结果:聚丙烯酰胺凝胶电泳和考马斯亮蓝R250染色显示,纯化的GST和4种P53-GST蛋白纯度在90%以上,且分子量与预计的完全一致.TRBP1的Western blot显示,野生型P53和P53-R175H均能沉淀MCF-7中的TRBP1,且结合力相似,而单独的GST则无沉淀TRBP1的作用.与野生型P53和P53 R175H相比,P53 2C与TRBP1的结合力明显增加,P53 N5与TRBP1的结合力明显减弱.结论:P53和TRBP1可以直接体外结合,P53的C端(293~393)是与TRBP1结合的结构域.P53和TRBP1结构域依赖性的结合可能与端粒动态变化所诱导的细胞活动有关.

  5. Short telomeres initiate telomere recombination in primary and tumor cells.

    Tammy A Morrish

    2009-01-01

    Full Text Available Human tumors that lack telomerase maintain telomeres by alternative lengthening mechanisms. Tumors can also form in telomerase-deficient mice; however, the genetic mechanism responsible for tumor growth without telomerase is unknown. In yeast, several different recombination pathways maintain telomeres in the absence of telomerase-some result in telomere maintenance with minimal effects on telomere length. To examine non-telomerase mechanisms for telomere maintenance in mammalian cells, we used primary cells and lymphomas from telomerase-deficient mice (mTR-/- and Emumyc+mTR-/- and CAST/EiJ mouse embryonic fibroblast cells. These cells were analyzed using pq-ratio analysis, telomere length distribution outliers, CO-FISH, Q-FISH, and multicolor FISH to detect subtelomeric recombination. Telomere length was maintained during long-term growth in vivo and in vitro. Long telomeres, characteristic of human ALT cells, were not observed in either late passage or mTR-/- tumor cells; instead, we observed only minimal changes in telomere length. Telomere length variation and subtelomeric recombination were frequent in cells with short telomeres, indicating that length maintenance is due to telomeric recombination. We also detected telomere length changes in primary mTR-/- cells that had short telomeres. Using mouse mTR+/- and human hTERT+/- primary cells with short telomeres, we found frequent length changes indicative of recombination. We conclude that telomere maintenance by non-telomerase mechanisms, including recombination, occurs in primary cells and is initiated by short telomeres, even in the presence of telomerase. Most intriguing, our data indicate that some non-telomerase telomere maintenance mechanisms occur without a significant increase in telomere length.

  6. Phylogeny of TTAGG telomeric repeats in insects

    Marec, František; Vítková, Magda; Grossmann, Petr; Trubač, Pavel; Frydrychová, Radmila

    2001-01-01

    Roč. 9, č. 1 (2001), s. 113. ISSN 0967-3849. [International Chromosome Conference /14./. 04.09.2001-08.09.2001, Wurburg] Institutional research plan: CEZ:AV0Z5007907 Keywords : sequence Subject RIV: EB - Genetics ; Molecular Biology

  7. Telomerase Repeated Amplification Protocol (TRAP)

    Mender, Ilgen; Shay, Jerry W.

    2016-01-01

    Telomeres are found at the end of eukaryotic linear chromosomes, and proteins that bind to telomeres protect DNA from being recognized as double-strand breaks thus preventing end-to-end fusions (Griffith et al., 1999). However, due to the end replication problem and other factors such as oxidative damage, the limited life span of cultured cells (Hayflick limit) results in progressive shortening of these protective structures (Hayflick and Moorhead, 1961; Olovnikov, 1973). The ribonucleoprotein enzyme complex telomerase-consisting of a protein catalytic component hTERT and a functional RNA component hTR or hTERC- counteracts telomere shortening by adding telomeric repeats to the end of chromosomes in ~90% of primary human tumors and in some transiently proliferating stem-like cells (Shay and Wright, 1996; Shay and Wright, 2001). This results in continuous proliferation of cells which is a hallmark of cancer. Therefore, telomere biology has a central role in aging, cancer progression/metastasis as well as targeted cancer therapies. There are commonly used methods in telomere biology such as Telomere Restriction Fragment (TRF) (Mender and Shay, 2015b), Telomere Repeat Amplification Protocol (TRAP) and Telomere dysfunction Induced Foci (TIF) analysis (Mender and Shay, 2015a). In this detailed protocol we describe Telomere Repeat Amplification Protocol (TRAP). The TRAP assay is a popular method to determine telomerase activity in mammalian cells and tissue samples (Kim et al., 1994). The TRAP assay includes three steps: extension, amplification, and detection of telomerase products. In the extension step, telomeric repeats are added to the telomerase substrate (which is actually a non telomeric oligonucleotide, TS) by telomerase. In the amplification step, the extension products are amplified by the polymerase chain reaction (PCR) using specific primers (TS upstream primer and ACX downstream primer) and in the detection step, the presence or absence of telomerase is

  8. Visualization of Telomere Integrity and Function In Vitro and In Vivo Using Immunofluorescence Techniques

    Cesare, Anthony J.; Heaphy, Christopher M.; O’Sullivan, Roderick J.

    2015-01-01

    In cancer cells, telomere length maintenance occurs largely via the direct synthesis of TTAGGG repeats at chromosome ends by telomerase, or less frequently by the recombination-dependent alternative lengthening of telomeres (ALT) pathway. The latter is characterized by the atypical clustering of telomeres within promyelocytic leukemia (PML) nuclear bodies, which harbor proteins that are linked with DNA repair and recombination activity. For this reason, it is speculated that these associated ...

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

    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

  10. Telomere Transcripts Target Telomerase in Human Cancer Cells.

    Kreilmeier, Theresa; Mejri, Doris; Hauck, Marlene; Kleiter, Miriam; Holzmann, Klaus

    2016-01-01

    Long non-coding transcripts from telomeres, called telomeric repeat-containing RNA (TERRA), were identified as blocking telomerase activity (TA), a telomere maintenance mechanism (TMM), in tumors. We expressed recombinant TERRA transcripts in tumor cell lines with TA and with alternative lengthening of telomeres (ALT) to study effects on TMM and cell growth. Adeno- and lentivirus constructs (AV and LV) were established for transient and stable expression of approximately 130 units of telomere hexanucleotide repeats under control of cytomegalovirus (CMV) and human RNase P RNA H1 (hH1) promoters with and without polyadenylation, respectively. Six human tumor cell lines either using telomerase or ALT were infected and analyzed for TA levels. Pre-infection cells using telomerase had 1%-3% of the TERRA expression levels of ALT cells. AV and LV expression of recombinant TERRA in telomerase positive cells showed a 1.3-2.6 fold increase in TERRA levels, and a decrease in TA of 25%-58%. Dominant-negative or small hairpin RNA (shRNA) viral expression against human telomerase reverse transcriptase (hTERT) results in senescence, not induced by TERRA expression. Population doubling time, cell viability and TL (telomere length) were not impacted by ectopic TERRA expression. Clonal growth was reduced by TERRA expression in TA but not ALT cell lines. ALT cells were not affected by treatments applied. Established cell models and tools may be used to better understand the role of TERRA in the cell, especially for targeting telomerase. PMID:27537914

  11. Telomere Rapid Deletion Regulates Telomere Length in Arabidopsis thaliana▿

    Watson, J. Matthew; Dorothy E Shippen

    2006-01-01

    Telomere length is maintained in species-specific equilibrium primarily through a competition between telomerase-mediated elongation and the loss of terminal DNA through the end-replication problem. Recombinational activities are also capable of both lengthening and shortening telomeres. Here we demonstrate that elongated telomeres in Arabidopsis Ku70 mutants reach a new length set point after three generations. Restoration of wild-type Ku70 in these mutants leads to discrete telomere-shorten...

  12. Mathematical model of alternative mechanism of telomere length maintenance

    Kollár, Richard; Bod'ová, Katarína; Nosek, Jozef; Tomáška, L'ubomír

    2014-03-01

    Biopolymer length regulation is a complex process that involves a large number of biological, chemical, and physical subprocesses acting simultaneously across multiple spatial and temporal scales. An illustrative example important for genomic stability is the length regulation of telomeres—nucleoprotein structures at the ends of linear chromosomes consisting of tandemly repeated DNA sequences and a specialized set of proteins. Maintenance of telomeres is often facilitated by the enzyme telomerase but, particularly in telomerase-free systems, the maintenance of chromosomal termini depends on alternative lengthening of telomeres (ALT) mechanisms mediated by recombination. Various linear and circular DNA structures were identified to participate in ALT, however, dynamics of the whole process is still poorly understood. We propose a chemical kinetics model of ALT with kinetic rates systematically derived from the biophysics of DNA diffusion and looping. The reaction system is reduced to a coagulation-fragmentation system by quasi-steady-state approximation. The detailed treatment of kinetic rates yields explicit formulas for expected size distributions of telomeres that demonstrate the key role played by the J factor, a quantitative measure of bending of polymers. The results are in agreement with experimental data and point out interesting phenomena: an appearance of very long telomeric circles if the total telomere density exceeds a critical value (excess mass) and a nonlinear response of the telomere size distributions to the amount of telomeric DNA in the system. The results can be of general importance for understanding dynamics of telomeres in telomerase-independent systems as this mode of telomere maintenance is similar to the situation in tumor cells lacking telomerase activity. Furthermore, due to its universality, the model may also serve as a prototype of an interaction between linear and circular DNA structures in various settings.

  13. Childhood Physical and Sexual Abuse History and Leukocyte Telomere Length among Women in Middle Adulthood.

    Susan M Mason

    Full Text Available Abuse victimization in childhood is associated with a variety of age-related cardiometabolic diseases, but the mechanisms remain unknown. Telomeres, which form the protective caps at the ends of chromosomes, have been proposed as measures of biological age, and a growing body of research suggests that telomere attrition may help to explain relationships between stress and cardiometabolic degradation. We examined the association between childhood abuse victimization and leukocyte telomere length among 1,135 participants in the Nurses' Health Study II (NHSII.The NHSII ascertained physical and sexual child abuse histories in 2001. Telomere length was measured in genomic DNA extracted from peripheral blood leukocytes collected between 1996 and 1999. The ratio of telomere repeat copy number to a single gene copy number (T/S was determined by a modified version of the quantitative real-time PCR telomere assay. Telomere length was log-transformed and corrected for assay variation across batch. We regressed telomere length on childhood abuse exposure variables and covariates using linear regression.We observed a reduction in telomere length associated with moderate physical abuse versus no physical abuse, but there was no evidence of a dose-response relationship for increased severity of physical abuse. No associations were noted for sexual abuse.We found no evidence of an association between severity of childhood physical or sexual abuse and leukocyte telomere length in the NHSII.

  14. TERRA-Reinforced Association of LSD1 with MRE11 Promotes Processing of Uncapped Telomeres

    Antonio Porro

    2014-02-01

    Full Text Available Telomeres protect chromosome ends from being recognized as sites of DNA damage. Upon telomere shortening or telomere uncapping induced by loss of telomeric repeat-binding factor 2 (TRF2, telomeres elicit a DNA-damage response leading to cellular senescence. Here, we show that following TRF2 depletion, the levels of the long noncoding RNA TERRA increase and LSD1, which binds TERRA, is recruited to telomeres. At uncapped telomeres, LSD1 associates with MRE11, one of the nucleases implicated in the processing of 3′ telomeric G overhangs, and we show that LSD1 is required for efficient removal of these structures. The LSD1-MRE11 interaction is reinforced in vivo following TERRA upregulation in TRF2-deficient cells and in vitro by TERRA-mimicking RNA oligonucleotides. Furthermore, LSD1 enhances the nuclease activity of MRE11 in vitro. Our data indicate that recruitment of LSD1 to deprotected telomeres requires MRE11 and is promoted by TERRA. LSD1 stimulates MRE11 catalytic activity and nucleolytic processing of uncapped telomeres.

  15. Visualization of Telomere Integrity and Function In Vitro and In Vivo Using Immunofluorescence Techniques.

    Cesare, Anthony J; Heaphy, Christopher M; O'Sullivan, Roderick J

    2015-01-01

    In cancer cells, telomere length maintenance occurs largely via the direct synthesis of TTAGGG repeats at chromosome ends by telomerase, or less frequently by the recombination-dependent alternative lengthening of telomeres (ALT) pathway. The latter is characterized by the atypical clustering of telomeres within promyelocytic leukemia (PML) nuclear bodies, which harbor proteins that are linked with DNA repair and recombination activity. For this reason, it is speculated that these associated PML bodies represent the sites of the recombination that maintains telomere length. The protocols described here can be employed for the routine investigation of the structural integrity of telomeres and the association of proteins at telomeres in normal cells, challenged cells, and archived formalin-fixed paraffin-embedded clinical tissue specimens that may have activated the ALT pathway. PMID:26132175

  16. Primary Studies on Cotton Telomere

    2008-01-01

    The Arabidopsis-type telomere sequence was amplified and cloned using the primers designed from the fragment which contained the telomere sequence in an Arabidopsis BAC.In situ hybridizations with cotton metaphase chromosomes,using the telomere as probe,it indicated that the signals

  17. Telomerers rolle ved aldersbetingede sygdomme

    Bendix, Laila; Kølvraa, Steen

    2010-01-01

    Telomeres are specialized DNA structures, protecting the ends of linear chromosomes. The association between telomeres and cellular aging is well-established, and it has been shown that there is a negative correlation between telomere length and chronological age for many types of human tissue. O...

  18. Ticking Telomeres/Telltale Telomerase.

    Biermann, Carol A.

    1997-01-01

    Discusses telomeres, complexes of DNA and protein that form the chromatin at the ends of chromosomes. Highlights telomeres as controllers of chromosome integrity, expendable telomeres, DNA replication requirements and their consequences, protection of structural genes, telomerase as indicators of immortality, cancer cells and other immortals, and…

  19. ALT Telomeres borrow from meiosis

    Arnoult, Nausica; Karlseder, Jan

    2014-01-01

    The clustering of telomeres is required for the homologous recombination events that maintain chromosome ends in cells relying on alternative lengthening of telomeres (ALT). New data emerged to demonstrate that damage signaling at telomeres induces directional movement and synapsis, driven by the machinery responsible for recombination in meiosis.

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

    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.

  1. Delayed paternal age of reproduction in humans is associated with longer telomeres across two generations of descendants

    Eisenberg, Dan T. A.; Hayes, M. Geoffrey; Kuzawa, Christopher W.

    2012-01-01

    Telomeres are repeating DNA sequences at the ends of chromosomes that protect and buffer genes from nucleotide loss as cells divide. Telomere length (TL) shortens with age in most proliferating tissues, limiting cell division and thereby contributing to senescence. However, TL increases with age in sperm, and, correspondingly, offspring of older fathers inherit longer telomeres. Using data and samples from a longitudinal study from the Philippines, we first replicate the finding that paternal...

  2. Telomere-Associated Protein TIN2 Is Essential for Early Embryonic Development through a Telomerase-Independent Pathway

    Chiang, Y. Jeffrey; Kim, Sahn-Ho; Tessarollo, Lino; Campisi, Judith; Hodes, Richard J.

    2004-01-01

    TIN2 is a negative regulator of telomere elongation that interacts with telomeric DNA repeat binding factor 1 (TRF1) and affects telomere length by a telomerase-dependent mechanism. Here we show that inactivation of the mouse TRF1-interacting protein 2 (TIN2) gene results in early embryonic lethality. We further observed that the embryonic lethality of TIN2 mutant mice was not affected by inactivation of the telomerase reverse transcriptase gene, indicating that embryonic lethality is not the...

  3. Chromosomal mapping of chicken mega-telomere arrays to GGA9, 16, 28 and W using a cytogenomic approach.

    Delany, M E; Gessaro, T M; Rodrigue, K L; Daniels, L M

    2007-01-01

    Four mega-telomere loci were mapped to chicken chromosomes 9, 16, 28, and the W sex chromosome by dual-color fluorescence in situ hybridization using a telomeric sequence probe and BAC clones previously assigned to chicken chromosomes. The in-common features of the mega-telomere chromosomes are that microchromosomes are involved rather than macrochromosomes; in three cases (9, 16, 28) acrocentrics are involved with the mega-telomeres mapping to the p arms. Three of the four chromosomes (9, 16, W) encode tandem repeats which in two cases (9 and 16) involve the ribosomal DNA arrays (the 5S and 18S-5.8S-28S gene repeats, respectively). All involved chromosomes have a typical-sized telomere on the opposite terminus. Intra- and interindividual variation for mega-telomere distribution are discussed in terms of karyotype abnormalities and the potential for mitotic instability of some telomeres. The diversity and distribution of telomere array quantity in the chicken genome should be useful in contributing to research related to telomere length regulation - how and by what mechanism genomes and individual chromosomes establish and maintain distinct sets of telomere array sizes, as well as for future studies related to stability of the chicken genome affecting development, growth, cellular lifespan and disease. An additional impact of this study includes the listing of BAC clones (26 autosomal and six W BACs tested) that were cytogenetically verified; this set of BACs provide a useful tool for future cytogenetic analyses of the microchromosomes. PMID:17675845

  4. PARP1 Is a TRF2-associated Poly(ADP-Ribose)Polymerase and Protects Eroded Telomeres

    Liu, Yie [ORNL; Wu, Jun [ORNL; Schreiber, Valerie [Universite Louis Pasteur, France; Dunlap, John [University of Tennessee, Knoxville (UTK); Dantzer, Francoise [Universite Louis Pasteur, France; Wang, Yisong [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)

    2006-01-01

    Poly(ADP-ribose)polymerase 1 (PARP1) is well characterized for its role in base excision repair (BER), where it is activated by and binds to DNA breaks and catalyzes the poly(ADP-ribosyl)ation of several substrates involved in DNA damage repair. Here we demonstrate that PARP1 associates with telomere repeat binding factor 2 (TRF2) and is capable of poly(ADP-ribosyl)ation of TRF2, which affects binding of TRF2 to telomeric DNA. Immunostaining of interphase cells or metaphase spreads shows that PARP1 is detected sporadically at normal telomeres, but it appears preferentially at eroded telomeres caused by telomerase deficiency or damaged telomeres induced by DNA-damaging reagents. Although PARP1 is dispensable in the capping of normal telomeres, Parp1 deficiency leads to an increase in chromosome end-to-end fusions or chromosome ends without detectable telomeric DNA in primary murine cells after induction of DNA damage. Our results suggest that upon DNA damage, PARP1 is recruited to damaged telomeres, where it can help protect telomeres against chromosome end-to-end fusions and genomic instability.

  5. PARP1 is a TRF2-associated poly(ADP-ribose) polymerase and protects eroded telomeres

    Gomez, Marla V [ORNL; Wu, Jun [ORNL; Wang, Yisong [ORNL; Liu, Yie [ORNL

    2006-01-01

    Poly(ADP-ribose)polymerase 1 (PARP1) is well characterized for its role in base excision repair (BER), where it is activated by and binds to DNA breaks and catalyzes the poly(ADP-ribosyl)ation of several substrates involved in DNA damage repair. Here we demonstrate that PARP1 associates with telomere repeat binding factor 2 (TRF2) and is capable of poly(ADP-ribosyl)ation of TRF2, which affects binding of TRF2 to telomeric DNA. Immunostaining of interphase cells or metaphase spreads shows that PARP1 is detected sporadically at normal telomeres, but it appears preferentially at eroded telomeres caused by telomerase deficiency or damaged telomeres induced by DNA-damaging reagents. Although PARP1 is dispensable in the capping of normal telomeres, Parp1 deficiency leads to an increase in chromosome end-to-end fusions or chromosome ends without detectable telomeric DNA in primary murine cells after induction of DNA damage. Our results suggest that upon DNA damage, PARP1 is recruited to damaged telomeres, where it can help protect telomeres against chromosome end-to-end fusions and genomic instability.

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

    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 (AtTRB21–64) using nuclear magnetic resonance (NMR) spectroscopy. In addition, the inter-molecular interaction between AtTRB21–64 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

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

    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.

  8. Leukocyte telomere length in major depression: correlations with chronicity, inflammation and oxidative stress--preliminary findings.

    Owen M Wolkowitz

    Full Text Available BACKGROUND: 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. METHODOLOGY: 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. PRINCIPAL FINDINGS: 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. CONCLUSIONS: 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

  9. Alternative lengthening of telomeres: remodeling the telomere architecture

    Conomos, Dimitri; Hilda A Pickett; Reddel, Roger R

    2013-01-01

    To escape from the normal limits on proliferative potential, cancer cells must employ a means to counteract the gradual telomere attrition that accompanies semi-conservative DNA replication. While the majority of human cancers do this by up-regulating telomerase enzyme activity, most of the remainder use a homologous recombination-mediated mechanism of telomere elongation known as alternative lengthening of telomeres (ALT). Many molecular details of the ALT pathway are unknown, and even less ...

  10. Detection of alternative lengthening of telomeres by telomere quantitative PCR

    Lau, Loretta M. S.; Dagg, Rebecca A.; Henson, Jeremy D.; Au, Amy Y.M.; Royds, Janice A; Reddel, Roger R

    2012-01-01

    Alternative lengthening of telomeres (ALT) is one of the two known telomere length maintenance mechanisms that are essential for the unlimited proliferation potential of cancer cells. Existing methods for detecting ALT in tumors require substantial amounts of tumor material and are labor intensive, making it difficult to study prevalence and prognostic significance of ALT in large tumor cohorts. Here, we present a novel strategy utilizing telomere quantitative PCR to diagnose ALT. The protoco...

  11. Up-regulation of telomere-binding proteins, TRF1, TRF2, and TIN2 is related to telomere shortening during human multistep hepatocarcinogenesis.

    Oh, Bong-Kyeong; Kim, Young-Joo; Park, Chanil; Park, Young Nyun

    2005-01-01

    The telomeric repeat-binding factor 1 (TRF1), TRF2, and the TRF1-interacting nuclear protein 2 (TIN2) are involved in telomere maintenance. We describe the regulation of expression of these genes along with their relationship to telomere length in hepatocarcinogenesis. The transcriptional expression of these genes, TRF1 protein, and telomere length was examined in 9 normal livers, 14 chronic hepatitis, 24 liver cirrhosis, 5 large regenerative nodules, 14 low-grade dysplastic nodules (DNs), 7 high-grade DNs, 10 DNs with hepatocellular carcinoma (HCC) foci, and 31 HCCs. The expression of TRF1, TRF2, TIN2 mRNA, and TRF1 protein was gradually increased according to the progression of hepatocarcinogenesis with a marked increase in high-grade DNs and DNs with HCC foci and a further increase in HCCs. There was a gradual shortening of telomere during hepatocarcinogenesis with a significant reduction in length in DNs. Most nodular lesions (52 of 67) had shorter telomeres than their adjacent chronic hepatitis or liver cirrhosis, and the telomere lengths were inversely correlated with the mRNA level of these genes (P HCC foci. In conclusion, TRF1, TRF2, and TIN2 might be involved in multistep hepatocarcinogenesis by playing crucial roles in telomere shortening. PMID:15632001

  12. Evolution of species-specific promoter-associated mechanisms for protecting chromosome ends by Drosophila Het-A telomeric transposons

    Traverse, Karen L.; George, Janet A.; DeBaryshe, P. G.; Pardue, Mary-Lou

    2010-01-01

    The non-LTR retrotransposons forming Drosophila telomeres constitute a robust mechanism for telomere maintenance, one which has persisted since before separation of the extant Drosophila species. These elements in D. melanogaster differ from nontelomeric retrotransposons in ways that give insight into general telomere biology. Here, we analyze telomere-specific retrotransposons from D. virilis, separated from D. melanogaster by 40 to 60 million years, to evaluate the evolutionary divergence of their telomeric traits. The telomeric retrotransposon HeT-A from D. melanogaster has an unusual promoter near its 3′ terminus that drives not the element in which it resides, but the adjacent downstream element in a head-to-tail array. An obvious benefit of this promoter is that it adds nonessential sequence to the 5′ end of each transcript, which is reverse transcribed and added to the chromosome. Because the 5′ end of each newly transposed element forms the end of the chromosome until another element transposes onto it, this nonessential sequence can buffer erosion of sequence essential for HeT-A. Surprisingly, we have now found that HeT-A in D. virilis has a promoter typical of non-LTR retrotransposons. This promoter adds no buffering sequence; nevertheless, the complete 5′ end of the element persists in telomere arrays, necessitating a more precise processing of the extreme end of the telomere in D. virilis. PMID:20194755

  13. Telomeres in Alliaceae

    Sýkorová, Eva; Fajkus, Jiří; Skleničková, Marie; Lim, K.Y.; Neplechová, Kamila; Blattner, F.R.; Chase, M.W.; Leitch, Andrew R.

    Venice, 2006. P 3.50-P 3.50. [5th Plant Genomics, European Meetings. 11.10.2006-14.10.2006, Venice] R&D Projects: GA ČR(CZ) GP204/04/P105; GA ČR(CZ) GA521/05/0055; GA AV ČR(CZ) IAA600040505 Institutional research plan: CEZ:AV0Z50040507 Keywords : telomere * evolution * Alliaceae Subject RIV: BO - Biophysics

  14. Alternative lengthening of telomeres: remodeling the telomere architecture

    Dimitri eConomos

    2013-02-01

    Full Text Available To escape from the normal limits on proliferative potential, cancer cells must employ a means to counteract the gradual telomere attrition that accompanies semi-conservative DNA replication. While the majority of human cancers do this by up-regulating telomerase enzyme activity, most of the remainder use a homologous recombination-mediated mechanism of telomere elongation known as alternative lengthening of telomeres (ALT. Many molecular details of the ALT pathway are unknown, and even less is known regarding the mechanisms by which this pathway is activated. Here, we review current findings about telomere structure in ALT cells, including DNA sequence, shelterin content, and heterochromatic state. We speculate that remodeling of the telomere architecture may contribute to the emergence and maintenance of the ALT phenotype.

  15. Telomere Transcripts Target Telomerase in Human Cancer Cells

    Theresa Kreilmeier

    2016-08-01

    Full Text Available Long non-coding transcripts from telomeres, called telomeric repeat-containing RNA (TERRA, were identified as blocking telomerase activity (TA, a telomere maintenance mechanism (TMM, in tumors. We expressed recombinant TERRA transcripts in tumor cell lines with TA and with alternative lengthening of telomeres (ALT to study effects on TMM and cell growth. Adeno- and lentivirus constructs (AV and LV were established for transient and stable expression of approximately 130 units of telomere hexanucleotide repeats under control of cytomegalovirus (CMV and human RNase P RNA H1 (hH1 promoters with and without polyadenylation, respectively. Six human tumor cell lines either using telomerase or ALT were infected and analyzed for TA levels. Pre-infection cells using telomerase had 1%–3% of the TERRA expression levels of ALT cells. AV and LV expression of recombinant TERRA in telomerase positive cells showed a 1.3–2.6 fold increase in TERRA levels, and a decrease in TA of 25%–58%. Dominant-negative or small hairpin RNA (shRNA viral expression against human telomerase reverse transcriptase (hTERT results in senescence, not induced by TERRA expression. Population doubling time, cell viability and TL (telomere length were not impacted by ectopic TERRA expression. Clonal growth was reduced by TERRA expression in TA but not ALT cell lines. ALT cells were not affected by treatments applied. Established cell models and tools may be used to better understand the role of TERRA in the cell, especially for targeting telomerase.

  16. Interactions of TRF2 with model telomeric ends

    Telomeres are DNA-protein complexes at the ends of eukaryotic chromosomes, the integrity of which is essential for chromosome stability. An important telomere binding protein, TTAGGG repeat factor 2 (TRF2), is thought to protect telomere ends by remodeling them into T-loops. We show that TRF2 specifically interacts with telomeric ss/ds DNA junctions and binding is sensitive to the sequence of the 3', guanine-strand (G-strand) overhang and double-stranded DNA sequence at the junction. Association of TRF2 with DNA junctions hinders cleavage by exonuclease T. TRF2 interactions with the G-strand overhang do not involve the TRF2 DNA binding domain or the linker region. However, mobility shifts and atomic force microscopy show that the previously uncharacterized linker region is involved in DNA-specific, TRF2 oligomerization. We suggest that T-loop formation at telomere ends involves TRF2 binding to the G-strand overhang and oligomerization through both the known TRFH domain and the linker region

  17. Rad59-facilitated acquisition of Y' elements by short telomeres delays the onset of senescence.

    Dmitri Churikov

    2014-11-01

    Full Text Available Telomerase-negative yeasts survive via one of the two Rad52-dependent recombination pathways, which have distinct genetic requirements. Although the telomere pattern of type I and type II survivors is well characterized, the mechanistic details of short telomere rearrangement into highly evolved pattern observed in survivors are still missing. Here, we analyze immediate events taking place at the abruptly shortened VII-L and native telomeres. We show that short telomeres engage in pairing with internal Rap1-bound TG1-3-like tracts present between subtelomeric X and Y' elements, which is followed by BIR-mediated non-reciprocal translocation of Y' element and terminal TG1-3 repeats from the donor end onto the shortened telomere. We found that choice of the Y' donor was not random, since both engineered telomere VII-L and native VI-R acquired Y' elements from partially overlapping sets of specific chromosome ends. Although short telomere repair was associated with transient delay in cell divisions, Y' translocation on native telomeres did not require Mec1-dependent checkpoint. Furthermore, the homeologous pairing between the terminal TG1-3 repeats at VII-L and internal repeats on other chromosome ends was largely independent of Rad51, but instead it was facilitated by Rad59 that stimulates Rad52 strand annealing activity. Therefore, Y' translocation events taking place during presenescence are genetically separable from Rad51-dependent Y' amplification process that occurs later during type I survivor formation. We show that Rad59-facilitated Y' translocations on X-only telomeres delay the onset of senescence while preparing ground for type I survivor formation.

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

    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.

  19. ALT telomeres get together with nuclear receptors.

    Aeby, Eric; Lingner, Joachim

    2015-02-26

    Nuclear receptors bind chromosome ends in "alternative lengthening of telomeres" (ALT) cancer cells that maintain their ends by homologous recombination instead of telomerase. Marzec et al. now demonstrate that, in ALT cells, nuclear receptors not only trigger distal chromatin associations to mediate telomere-telomere recombination events, but also drive chromosome-internal targeted telomere insertions (TTI). PMID:25723159

  20. The TEL patch of telomere protein TPP1 mediates telomerase recruitment and processivity

    Nandakumar, Jayakrishnan; Bell, Caitlin F.; Weidenfeld, Ina; Zaug, Arthur J.; Leinwand, Leslie A.; Cech, Thomas R.

    2012-01-01

    Human chromosome ends are capped by shelterin, a protein complex that protects the natural ends from being recognized as sites of DNA damage and also regulates the telomere-replicating enzyme, telomerase 1–3 . Shelterin includes the heterodimeric POT1-TPP1 protein, which binds the telomeric single-stranded DNA tail 4–9 . TPP1 has been implicated both in recruiting telomerase to telomeres and in stimulating telomerase processivity (the addition of multiple DNA repeats after a single primer-bin...

  1. Deletion of Ogg1 DNA glycosylase results in telomere base damage and length alteration in yeast

    LU, Jian; Liu, Yie

    2009-01-01

    Telomeres consist of short guanine-rich repeats. Guanine can be oxidized to 8-oxo-7,8-dihydroguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG). 8-oxoguanine DNA glycosylase (Ogg1) repairs these oxidative guanine lesions through the base excision repair (BER) pathway. Here we show that in Saccharomyces cerevisiae ablation of Ogg1p leads to an increase in oxidized guanine level in telomeric DNA. The ogg1 deletion (ogg1Δ) strain shows telomere lengthening that is dependent...

  2. Unwinding Protein Complexes in ALTernative Telomere Maintenance

    Bhattacharyya, Saumitri; Sandy, April; Groden, Joanna

    2010-01-01

    Telomeres are composed of specialized chromatin that includes DNA repair/recombination proteins, telomere DNA-binding proteins and a number of three dimensional nucleic acid structures including G-quartets and D-loops. A number of studies suggest that the BLM and WRN recQ-like helicases play important roles in recombination-mediated mechanisms of telomere elongation or Alternative Lengthening of Telomeres (ALT), processes that maintain/elongate telomeres in the absence of telomerase. BLM and ...

  3. Long Telomeres Bypass the Requirement for Telomere Maintenance in Human Tumorigenesis

    Taboski, Michael A. S.; Sealey, David C.F.; Dorrens, Jennifer; Tayade, Chandrakant; Dean H Betts; Harrington, Lea

    2012-01-01

    Despite the importance of telomere maintenance in cancer cell survival via the elongation of telomeres by telomerase reverse transcriptase (TERT) or alternativelengthening of telomeres (ALT), it had not been tested directly whether telomere maintenance is dispensable for human tumorigenesis. We engineered human tumor cells containing loxP-flanked hTERT to enable extensive telomere elongation prior to complete hTERT excision. Despite unabated telomere erosion, hTERT-excised cells formed tumors...

  4. Telomere elongation involves intra-molecular DNA replication in cells utilizing alternative lengthening of telomeres

    Muntoni, Alessandra; Neumann, Axel A.; Hills, Mark; Reddel, Roger R

    2008-01-01

    Alternative lengthening of telomeres (ALT) is a telomere length maintenance mechanism based on recombination, where telomeres use other telomeric DNA as a template for DNA synthesis. About 10% of all human tumors depend on ALT for their continued growth, and understanding its molecular details is critically important for the development of cancer treatments that target this mechanism. We have previously shown that telomeres of ALT-positive human cells can become lengthened via inter-telomeric...

  5. An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres

    Wang, Yisong; Erdmann, Natalie; Giannone, Richard J.; Wu, Jun; Gomez, Marla; Liu, Yie

    2005-01-01

    Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient...

  6. Association of BLM and BRCA1 during Telomere Maintenance in ALT Cells.

    Samir Acharya

    Full Text Available Fifteen percent of tumors utilize recombination-based alternative lengthening of telomeres (ALT to maintain telomeres. The mechanisms underlying ALT are unclear but involve several proteins involved in homologous recombination including the BLM helicase, mutated in Bloom's syndrome, and the BRCA1 tumor suppressor. Cells deficient in either BLM or BRCA1 have phenotypes consistent with telomere dysfunction. Although BLM associates with numerous DNA damage repair proteins including BRCA1 during DNA repair, the functional consequences of BLM-BRCA1 association in telomere maintenance are not completely understood. Our earlier work showed the involvement of BRCA1 in different mechanisms of ALT, and telomere shortening upon loss of BLM in ALT cells. In order to delineate their roles in telomere maintenance, we studied their association in telomere metabolism in cells using ALT. This work shows that BLM and BRCA1 co-localize with RAD50 at telomeres during S- and G2-phases of the cell cycle in immortalized human cells using ALT but not in cells using telomerase to maintain telomeres. Co-immunoprecipitation of BRCA1 and BLM is enhanced in ALT cells at G2. Furthermore, BRCA1 and BLM interact with RAD50 predominantly in S- and G2-phases, respectively. Biochemical assays demonstrate that full-length BRCA1 increases the unwinding rate of BLM three-fold in assays using a DNA substrate that models a forked structure composed of telomeric repeats. Our results suggest that BRCA1 participates in ALT through its interactions with RAD50 and BLM.

  7. Primary Studies on Cotton Telomere

    LING Jian; PENG Ren-hai; WANG Kun-bo; WANG Chun-ying; SONG Guo-li; LIU Fang; LI Shao-hui; ZHANG Xiang-di; WANG Yu-hong

    2008-01-01

    @@ The Arabidopsis -type telomere sequence was amplified and cloned using the primers designed from the fragment which contained the telomere sequence in an Arabidopsis BAC.In situ hybridizations with cotton metaphase chromosomes,using the telomere as probe,it indicated that the signals were located at all chromosome ends of 7 diploid and 2 tetraploid cotton species.To identify the signals of FISH,the genome DNA of Xinhai 7,digested by Bal31 kinetics,was used in this study.

  8. Long Telomeres Bypass the Requirement for Telomere Maintenance in Human Tumorigenesis

    Michael A.S. Taboski

    2012-02-01

    Full Text Available Despite the importance of telomere maintenance in cancer cell survival via the elongation of telomeres by telomerase reverse transcriptase (TERT or alternative lengthening of telomeres (ALT, it had not been tested directly whether telomere maintenance is dispensable for human tumorigenesis. We engineered human tumor cells containing loxP-flanked hTERT to enable extensive telomere elongation prior to complete hTERT excision. Despite unabated telomere erosion, hTERT-excised cells formed tumors in mice and proliferated in vitro for up to 1 year. Telomerase reactivation or ALT was not observed, and the eventual loss of telomeric signal coincided with loss of tumorigenic potential and cell viability. Crisis was averted via the reintroduction of active but not inactive hTERT. Thus, telomere maintenance is dispensable for human tumorigenesis when telomere reserves are long. Yet, despite telomere instability and the presence of oncogenic RAS, human tumors remain susceptible to crisis induced by critically short telomeres.

  9. Telomeric Heterochromatin in Plasmodium falciparum

    Rosaura Hernandez-Rivas

    2010-01-01

    Full Text Available Until very recently, little was known about the chromatin structure of the telomeres and subtelomeric regions in Plasmodium falciparum. In yeast and Drosophila melanogaster, chromatin structure has long been known to be an important aspect in the regulation and functioning of these regions. Telomeres and subtelomeric regions are enriched in epigenetic marks that are specific to heterochromatin, such as methylation of lysine 9 of histone H3 and lysine 20 of histone H4. In P. falciparum, histone modifications and the presence of both the heterochromatin “writing” (PfSir2, PKMT and “reading” (PfHP1 machinery at telomeric and subtelomeric regions indicate that these regions are likely to have heterochromatic structure that is epigenetically regulated. This structure may be important for telomere functions such as the silencing of the var gene family implicated in the cytoadherence and antigenic variation of these parasites.

  10. Telomere-independent cellular senescence in human fetal cardiomyocytes

    Ball, Andrew J.; Levine, F

    2005-01-01

    Fetal cardiomyocytes have been proposed as a potential source of cell-based therapy for heart failure. This study examined cellular senescence in cultured human fetal ventricular cardiomyocytes (HFCs). HFCs were isolated and identified by immunocytochemistry and RT-PCR. Cells were found to senesce after 20-25 population doublings, as determined by growth arrest, morphological changes and senescence-associated beta-galactosidase activity. Using the telomeric repeat amplification protocol assay...

  11. miR-155 drives telomere fragility in human breast cancer by targeting TRF1.

    Dinami, Roberto; Ercolani, Cristiana; Petti, Eleonora; Piazza, Silvano; Ciani, Yari; Sestito, Rosanna; Sacconi, Andrea; Biagioni, Francesca; le Sage, Carlos; Agami, Reuven; Benetti, Roberta; Mottolese, Marcella; Schneider, Claudio; Blandino, Giovanni; Schoeftner, Stefan

    2014-08-01

    Telomeres consist of DNA tandem repeats that recruit the multiprotein complex shelterin to build a chromatin structure that protects chromosome ends. Although cancer formation is linked to alterations in telomere homeostasis, there is little understanding of how shelterin function is limited in cancer cells. Using a small-scale screening approach, we identified miR-155 as a key regulator in breast cancer cell expression of the shelterin component TERF1 (TRF1). miR-155 targeted a conserved sequence motif in the 3'UTR of TRF1, resulting in its translational repression. miR-155 was upregulated commonly in breast cancer specimens, as associated with reduced TRF1 protein expression, metastasis-free survival, and relapse-free survival in estrogen receptor-positive cases. Modulating miR-155 expression in cells altered TRF1 levels and TRF1 abundance at telomeres. Compromising TRF1 expression by elevating miR-155 increased telomere fragility and altered the structure of metaphase chromosomes. In contrast, reducing miR-155 levels improved telomere function and genomic stability. These results implied that miR-155 upregulation antagonizes telomere integrity in breast cancer cells, increasing genomic instability linked to poor clinical outcome in estrogen receptor-positive disease. Our work argued that miRNA-dependent regulation of shelterin function has a clinically significant impact on telomere function, suggesting the existence of "telo-miRNAs" that have an impact on cancer and aging. PMID:24876105

  12. Switch telomerase to ALT mechanism by inducing telomeric DNA damages and dysfunction of ATRX and DAXX.

    Hu, Yang; Shi, Guang; Zhang, Laichen; Li, Feng; Jiang, Yuanling; Jiang, Shuai; Ma, Wenbin; Zhao, Yong; Songyang, Zhou; Huang, Junjiu

    2016-01-01

    Activation of telomerase or alternative lengthening of telomeres (ALT) is necessary for tumours to escape from dysfunctional telomere-mediated senescence. Anti-telomerase drugs might be effective in suppressing tumour growth in approximately 85-90% of telomerase-positive cancer cells. However, there are still chances for these cells to bypass drug treatment after switching to the ALT mechanism to maintain their telomere integrity. But the mechanism underlying this switch is unknown. In this study, we used telomerase-positive cancer cells (HTC75) to discover the mechanism of the telomerase-ALT switch by inducing telomere-specific DNA damage, alpha-thalassemia X-linked syndrome protein (ATRX) knockdown and deletion of death associated protein (DAXX). Surprisingly, two important ALT hallmarks in the ALT-like HTC75 cells were observed after treatments: ALT-associated promyelocytic leukaemia bodies (APBs) and extrachromosomal circular DNA of telomeric repeats. Moreover, knocking out hTERT by utilizing the CRISPR/Cas9 technique led to telomere elongation in a telomerase-independent manner in ALT-like HTC75 cells. In summary, this is the first report to show that inducing telomeric DNA damage, disrupting the ATRX/DAXX complex and inhibiting telomerase activity in telomerase-positive cancer cells lead to the ALT switch. PMID:27578458

  13. The Relationship Between Spontaneous Telomere Loss and Chromosome Instability in a Human Tumor Cell Line

    Bijan Fouladi

    2000-01-01

    Full Text Available Chromosome instability plays an important role in cancer by promoting the alterations in the genome required for tumor cell progression. The loss of telomeres that protect the ends of chromosomes and prevent chromosome fusion has been proposed as one mechanism for chromosome instability in cancer cells, however, there is little direct evidence to support this hypothesis. To investigate the relationship between spontaneous telomere loss and chromosome instability in human cancer cells, clones of the EJ-30 tumor cell line were isolated in which a herpes simplex virus thymidine kinase (HSV-tk gene was integrated immediately adjacent to a telomere. Selection for HSV-tkdeficient cells with ganciclovir demonstrated a high rate of loss of the end these "marked" chromosomes (10-4 events/cell per generation. DNA sequence and cytogenetic analysis suggests that the loss of function of the HSV-tk gene most often involves telomere loss, sister chromatid fusion, and prolonged periods of chromosome instability. In some HSV-tk-deficient cells, telomeric repeat sequences were added on to the end of the truncated HSV-tk gene at a new location, whereas in others, no telomere was detected on the end of the marked chromosome. These results suggest that spontaneous telomere loss is a mechanism for chromosome instability in human cancer cells.

  14. Telomere profiles and tumor-associated macrophages with different immune signatures affect prognosis in glioblastoma.

    Hung, Noelyn A; Eiholzer, Ramona A; Kirs, Stenar; Zhou, Jean; Ward-Hartstonge, Kirsten; Wiles, Anna K; Frampton, Chris M; Taha, Ahmad; Royds, Janice A; Slatter, Tania L

    2016-03-01

    Telomere maintenance is a hallmark of cancer and likely to be targeted in future treatments. In glioblastoma established methods of identifying telomerase and alternative lengthening of telomeres leave a significant proportion of tumors with no defined telomere maintenance mechanism. This study investigated the composition of these tumors using RNA-Seq. Glioblastomas with an indeterminate telomere maintenance mechanism had an increased immune signature compared with alternative lengthening of telomeres and telomerase-positive tumors. Immunohistochemistry for CD163 confirmed that the majority (80%) of tumors with an indeterminate telomere maintenance mechanism had a high presence of tumor-associated macrophages. The RNA-Seq and immunostaining data separated tumors with no defined telomere maintenance mechanism into three subgroups: alternative lengthening of telomeres like tumors with a high presence of tumor-associated macrophages and telomerase like tumors with a high presence of tumor-associated macrophages. The third subgroup had no increase in tumor-associated macrophages and may represent a distinct category. The presence of tumor-associated macrophages conferred a worse prognosis with reduced patient survival times (alternative lengthening of telomeres with and without macrophages P=0.0004, and telomerase with and without macrophages P=0.013). The immune signatures obtained from RNA-Seq were significantly different between telomere maintenance mechanisms. Alternative lengthening of telomeres like tumors with macrophages had increased expression of interferon-induced proteins with tetratricopeptide repeats (IFIT1-3). Telomerase-positive tumors with macrophages had increased expression of macrophage receptor with collagenous structure (MARCO), CXCL12 and sushi-repeat containing protein x-linked 2 (SRPX2). Telomerase-positive tumors with macrophages were also associated with a reduced frequency of total/near total resections (44% vs >76% for all other subtypes

  15. Fanconi anemia proteins in telomere maintenance.

    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. PMID:27118469

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

    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

  17. Increased chemosensitivity of paclitaxel by telomeric fusion-induced genomic instability

    Woo, Seon Rang; Juhn, Kyoung Mi; Park, Jeong Eun; Ju, Yeun Jin; Yun, Mi Yong; Lee, Kee Ho [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Park, Gil Hong; Kim, Joon [College of Medicine, Korea University, Seoul (Korea, Republic of)

    2009-05-15

    A telomere is a region of repetitive DNA at the end of chromosomes. They protect a cell's chromosomes from fusing with each other or rearranging and so cells are normally destroyed when their telomeres are consumed. Most normal somatic cells lose telomeric repeats after each cell division. Telomeric shortening in humans can induce replicative senescence which blocks cell division. This mechanism appears to prevent genomic instability by limiting the number of cell divisions. Telomerase is an attractive molecular target, since its activity has been found in more than 85% of human cancers. Combination therapy with chemotherapeutic agent is superior to single in overall response rate and progression free survival. In this study, we showed that telomerase null cells are more hypersensitive by paclitaxel treatment than at wild type cells.

  18. Cloning and Analysis of Telomere-associated Sequences of Ginkgo biloba L.

    Liu Di; Lu Hai; Ji Fei-teng; Li Feng-lan; Guo Hui-hong

    2005-01-01

    Total genomic DNA was extracted from leaves of Ginkgo biloba L. by the method of hot CTAB. After determining quantification of DNA sample by microclorimetric spectrophotography, Arabidopsis-type telomere primer and Sau3A I cassette primer were used to isolate telomere-associated sequences from G. biloba L. by the method of cassette-ligation-mediated polymerase chain reaction (PCR). Using this method, two telomere-associated sequences, TAS 1 and TAS2, were isolated. The authors preformed Southern hybridization ofEcoR I -treated G. biloba genomic DNA with each clone. The hybridization pattern showed that the clones obtained were derived from G. biloba genomic DNA. There are the Arabidopsis-type TTTAGGG tandem repeats in telomeres of G.biloba.

  19. Dual roles of telomere dysfunction in initiation and suppression of tumorigenesis

    Human carcinomas arise through the acquisition of genetic changes that endow precursor cancer cells with a critical threshold of cancer-relevant genetic lesions. This complex genomic alterations confer upon precursor cancer cells the ability to grow indefinitely and to metastasize to distant sites. One important mechanism underlying a cell's tumorigenic potential is the status of its telomere. Telomeres are G-rich simple repeat sequences that serve to prevent chromosomal ends from being recognized as DNA double-strand breaks (DSBs). Dysfunctional telomeres resemble DSBs, leading to the formation of dicentric chromosomes that fuel high degrees of genomic instability. In the setting of an intact p53 pathway, this instability promotes cellular senescence, a potent tumor suppressor mechanism. However, rare cells that stochastically lose p53 function emerge from this sea of genomic instability and progress towards cancer. In this review, we describe the use of mouse models to probe the impact of dysfunctional telomeres on tumor initiation and suppression

  20. Base J glucosyltransferase does not regulate the sequence specificity of J synthesis in trypanosomatid telomeric DNA.

    Bullard, Whitney; Cliffe, Laura; Wang, Pengcheng; Wang, Yinsheng; Sabatini, Robert

    2015-12-01

    Telomeric DNA of trypanosomatids possesses a modified thymine base, called base J, that is synthesized in a two-step process; the base is hydroxylated by a thymidine hydroxylase forming hydroxymethyluracil (hmU) and a glucose moiety is then attached by the J-associated glucosyltransferase (JGT). To examine the importance of JGT in modifiying specific thymine in DNA, we used a Leishmania episome system to demonstrate that the telomeric repeat (GGGTTA) stimulates J synthesis in vivo while mutant telomeric sequences (GGGTTT, GGGATT, and GGGAAA) do not. Utilizing an in vitro GT assay we find that JGT can glycosylate hmU within any sequence with no significant change in Km or kcat, even mutant telomeric sequences that are unable to be J-modified in vivo. The data suggests that JGT possesses no DNA sequence specificity in vitro, lending support to the hypothesis that the specificity of base J synthesis is not at the level of the JGT reaction. PMID:26815240

  1. Molecular architecture of classical cytological landmarks: Centromeres and telomeres

    Meyne, J.

    1994-11-01

    Both the human telomere repeat and the pericentromeric repeat sequence (GGAAT)n were isolated based on evolutionary conservation. Their isolation was based on the premise that chromosomal features as structurally and functionally important as telomeres and centromeres should be highly conserved. Both sequences were isolated by high stringency screening of a human repetitive DNA library with rodent repetitive DNA. The pHuR library (plasmid Human Repeat) used for this project was enriched for repetitive DNA by using a modification of the standard DNA library preparation method. Usually DNA for a library is cut with restriction enzymes, packaged, infected, and the library is screened. A problem with this approach is that many tandem repeats don`t have any (or many) common restriction sites. Therefore, many of the repeat sequences will not be represented in the library because they are not restricted to a viable length for the vector used. To prepare the pHuR library, human DNA was mechanically sheared to a small size. These relatively short DNA fragments were denatured and then renatured to C{sub o}t 50. Theoretically only repetitive DNA sequences should renature under C{sub o}t 50 conditions. The single-stranded regions were digested using S1 nuclease, leaving the double-stranded, renatured repeat sequences.

  2. Nutrients, foods, dietary patterns and telomere length: Update of epidemiological studies and randomized trials.

    Freitas-Simoes, Tania-Marisa; Ros, Emilio; Sala-Vila, Aleix

    2016-04-01

    Identifying simple strategies to prevent or delay age-associated pathologies is a major public health concern. Attrition of telomeres, chromatin structures that help maintain genome stability, leads to cell death or senescence. Thus telomere length is a reliable hallmark of biological aging and the risk of developing age-related chronic diseases through common oxidation and inflammation mechanisms. Variability in telomere shortening that is independent of chronological age suggests that it is a modifiable factor, which may be explained in part by lifestyle variables such as smoking, adiposity, physical exercise, and diet. Here we summarize data from published studies focused on nutrition (nutrients, foods, and dietary patterns) and telomere length. Research on the topic is incipient and most data comes from epidemiologic studies, often cross-sectional in design. Consistent with well-known evidence of benefit or harm for chronic age-related diseases, dietary antioxidants and consumption of antioxidant-rich, plant-derived foods help maintain telomere length. In contrast, total and saturated fat intake and consumption of refined flour cereals, meat and meat products, and sugar-sweetened beverages relate to shorter telomeres. Data on alcohol and dairy products is controversial. There is evidence that adherence to the Mediterranean diet is associated with longer telomeres. Randomized clinical trials are limited to seafood-derived long-chain n-3 polyunsaturated fatty acids, with promising results. To fill the many gaps in our knowledge of the aging process and confirm nutrition as a useful tool to counteract biological aging more research is warranted, particularly observational studies using repeated measurements of telomere length and randomized trials of foods and dietary patterns with sequential telomere analyses. PMID:26975532

  3. Maintenance of Very Long Telomeres by Recombination in the Kluyveromyces lactis stn1-M1 Mutant Involves Extreme Telomeric Turnover, Telomeric Circles, and Concerted Telomeric Amplification

    Xu, Jianing; McEachern, Michael J.

    2012-01-01

    Some cancers utilize the recombination-dependent process of alternative lengthening of telomeres (ALT) to maintain long heterogeneous telomeres. Here, we studied the recombinational telomere elongation (RTE) of the Kluyveromyces lactis stn1-M1 mutant. We found that the total amount of the abundant telomeric DNA in stn1-M1 cells is subject to rapid variation and that it is likely to be primarily extrachromosomal. Rad50 and Rad51, known to be required for different RTE pathways in Saccharomyces...

  4. SUMO-Dependent Relocalization of Eroded Telomeres to Nuclear Pore Complexes Controls Telomere Recombination

    Dmitri Churikov; Ferose Charifi; Nadine Eckert-Boulet; Sonia Silva; Marie-Noelle Simon; Michael Lisby; Vincent Géli

    2016-01-01

    In budding yeast, inactivation of telomerase and ensuing telomere erosion cause relocalization of telomeres to nuclear pore complexes (NPCs). However, neither the mechanism of such relocalization nor its significance are understood. We report that proteins bound to eroded telomeres are recognized by the SUMO (small ubiquitin-like modifier)-targeted ubiquitin ligase (STUbL) Slx5-Slx8 and become increasingly SUMOylated. Recruitment of Slx5-Slx8 to eroded telomeres facilitates telomere relocaliz...

  5. Recombination at Long Mutant Telomeres Produces Tiny Single- and Double-Stranded Telomeric Circles

    Groff-Vindman, Cindy; Cesare, Anthony J.; Natarajan, Shobhana; Griffith, Jack D.; McEachern, Michael J.

    2005-01-01

    Recombinational telomere elongation (RTE) known as alternate lengthening of telomeres is the mechanism of telomere maintenance in up to 5 to 10% of human cancers. The telomeres of yeast mutants lacking telomerase can also be maintained by recombination. Previously, we proposed the roll-and-spread model to explain this elongation in the yeast Kluveromyces lactis. This model suggests that a very small (∼100-bp) circular molecule of telomeric DNA is copied by a rolling circle event to generate a...

  6. Alternative Lengthening of Telomeres is characterized by reduced compaction of telomeric chromatin.

    Episkopou, Charikleia; Draskovic, Irena; Van Beneden, Amandine; Tilman, Gaëlle; Mattiussi, Marina; Gobin, Matthieu; Arnoult, Nausica; Londoño-Vallejo, Arturo; Decottignies, Anabelle

    2014-01-01

    International audience Proper telomeric chromatin configuration is thought to be essential for telomere homeostasis and stability. Previous studies in mouse suggested that loss of heterochromatin marks at telomeres might favor onset of Alternative Lengthening of Telomeres (ALT) pathway, by promoting homologous recombination. However, analysis of chromatin status at human ALT telomeres has never been reported. Here, using isogenic human cell lines and cellular hybrids, which rely either on ...

  7. Topoisomerase IIIα is required for normal proliferation and telomere stability in alternative lengthening of telomeres

    Temime-Smaali, Nassima; Guittat, Lionel; Wenner, Thomas; Bayart, Emilie; Douarre, Céline; Gomez, Dennis; Giraud-Panis, Marie-Josèphe; Londono-Vallejo, Arturo; Gilson, Eric; Amor-Guéret, Mounira; Riou, Jean-François

    2008-01-01

    Topoisomerase (Topo) IIIα associates with BLM helicase, which is proposed to be important in the alternative lengthening of telomeres (ALT) pathway that allows telomere recombination in the absence of telomerase. Here, we show that human Topo IIIα colocalizes with telomeric proteins at ALT-associated promyelocytic bodies from ALT cells. In these cells, Topo IIIα immunoprecipitated with telomere binding protein (TRF) 2 and BLM and was shown to be associated with telomeric DNA by chromatin immu...

  8. Pilocytic Astrocytomas Have Telomere-Associated Promyelocytic Leukemia Bodies without Alternatively Lengthened Telomeres

    Slatter, Tania; Gifford-Garner, Jennifer; Wiles, Anna; Tan, Xin; Chen, Yu-Jen; MacFarlane, Martin; Sullivan, Michael; Royds, Janice; Hung, Noelyn

    2010-01-01

    Telomere maintenance by either telomerase activity or the recombination-mediated alternative lengthening of telomeres (ALT) mechanism is a hallmark of cancer. Tumors that use ALT as their telomere maintenance mechanism are characterized by long telomeres of great heterogeneity in length and by specific nuclear structures of co-localized promyelocytic leukemia protein and telomere DNA, called ALT-associated promyelocytic leukemia bodies (APBs). Recent advances have revealed a direct role for A...

  9. Telomere Length in Aged Mayak PA Nuclear Workers Chronically Exposed to Internal Alpha and External Gamma Radiation.

    Scherthan, Harry; Sotnik, Natalia; Peper, Michel; Schrock, Gerrit; Azizova, Tamara; Abend, Michael

    2016-06-01

    Telomeres consist of GC-rich DNA repeats and the "shelterin" protein complex that together protect chromosome ends from fusion and degradation. Telomeres shorten with age due to incomplete end replication and upon exposure to environmental and intrinsic stressors. Exposure to ionizing radiation is known to modulate telomere length. However, the response of telomere length in humans chronically exposed to radiation is poorly understood. Here, we studied relative telomere length (RTL) by IQ-FISH to leukocyte nuclei in a group of 100 workers from the plutonium production facility at the Mayak Production Association (PA) who were chronically exposed to alpha-emitting ((239)Pu) radiation and/or gamma (photon) radiation, and 51 local residents serving as controls, with a similar mean age of about 80 years. We applied generalized linear statistical models adjusted for age at biosampling and the second exposure type on a linear scale and observed an age-dependent telomere length reduction. In those individuals with the lowest exposure, a significant reduction of about 20% RTL was observed, both for external gamma radiation (≤1 Gy) and internal alpha radiation (≤0.05-0.1 Gy to the red bone marrow). In highly exposed individuals (>0.1 Gy alpha, 1-1.5 Gy gamma), the RTL was similar to control. Stratification by gender revealed a significant (∼30%) telomere reduction in low-dose-exposed males, which was absent in females. While the gender differences in RTL may reflect different working conditions, lifestyle and/or telomere biology, absence of a dose response in the highly exposed individuals may reflect selection against cells with short telomeres or induction of telomere-protective effects. Our observations suggest that chronic systemic exposure to radiation leads to variable dose-dependent effects on telomere length. PMID:27340887

  10. Novel telomere-anchored PCR approach for studying sexual stage telomeres in Aspergillus nidulans.

    Wang, Nengding; Rizvydeen, Saajidha; Vahedi, Mithaq; Vargas Gonzalez, Daysi M; Allred, Amanda L; Perry, Dustin W; Mirabito, Peter M; Kirk, Karen E

    2014-01-01

    Telomere length varies between germline and somatic cells of the same organism, leading to the hypothesis that telomeres are lengthened during meiosis. However, little is known about the meiotic telomere length in many organisms. In the filamentous fungus Aspergillus nidulans, the telomere lengths in hyphae and asexual spores are invariant. No study using existing techniques has determined the telomere length of the sexual ascospores due to the relatively low abundance of pure meiotic cells in A. nidulans and the small quantity of DNA present. To address this, we developed a simple and sensitive PCR strategy to measure the telomere length of A. nidulans meiotic cells. This novel technique, termed "telomere-anchored PCR," measures the length of the telomere on chromosome II-L using a small fraction of the DNA required for the traditional terminal restriction fragment (TRF) Southern analysis. Using this approach, we determined that the A. nidulans ascospore telomere length is virtually identical to telomeres of other cell types from this organism, approximately 110 bp, indicating that a surprisingly strict telomere length regulation exists in the major cell types of A. nidulans. When the hyphal telomeres were measured in a telomerase reverse transcriptase (TERT) knockout strain, small decreases in length were readily detected. Thus, this technique can detect telomeres in relatively rare cell types and is particularly sensitive in measuring exceptionally short telomeres. This rapid and inexpensive telomere-anchored PCR method potentially can be utilized in other filamentous fungi and types of organisms. PMID:24927411

  11. Spermatozoa telomeres determine telomere length in early embryos and offspring.

    de Frutos, C; López-Cardona, A P; Fonseca Balvís, N; Laguna-Barraza, R; Rizos, D; Gutierrez-Adán, A; Bermejo-Álvarez, P

    2016-01-01

    Offspring telomere length (TL) has been correlated with paternal TL, but the mechanism for this parent of origin-specific inheritance remains unclear. The objective of this study has been to determine the role of spermatozoa TL in embryonic telomere lengthening by using two mouse models showing dimorphism in their spermatozoa TL: Mus musculus vs Mus spretus and old vs young Mus musculus. Mus spretus spermatozoa displayed a shorter TL than Mus musculus. Hybrid offspring exhibited lower TL compared with Mus musculus starting at the two-cell stage, before the onset of telomerase expression. To analyze the role of spermatozoa telomeres in early telomere lengthening, we compared the TL in oocytes, zygotes, two-cell embryos and blastocysts produced by parthenogenesis or by fertilization with Mus musculus or Mus spretus spermatozoa. TL was significantly higher in spermatozoa compared with oocytes, and it increased significantly from the oocyte to the zygote stage in those embryos fertilized with Mus musculus spermatozoa, but not in those fertilized with Mus spretus spermatozoa or produced by parthenogenesis. A further increase was noted from the zygote to the two-cell stage in fertilized Mus musculus embryos, whereas hybrid embryos maintained the oocyte TL. Spermatozoa TL shortened with age in Mus musculus and the offspring from young males showed a significantly higher TL compared with that fathered by old males. These significant differences were already noticeable at the two-cell stage. These results suggest that spermatozoa telomeres act as a guide for telomerase-independent telomere lengthening resulting in differences in TL that persist after birth. PMID:26475708

  12. PML induces compaction, TRF2 depletion and DNA damage signaling at telomeres and promotes their alternative lengthening.

    Osterwald, Sarah; Deeg, Katharina I; Chung, Inn; Parisotto, Daniel; Wörz, Stefan; Rohr, Karl; Erfle, Holger; Rippe, Karsten

    2015-05-15

    The alternative lengthening of telomeres (ALT) mechanism allows cancer cells to escape senescence and apoptosis in the absence of active telomerase. A characteristic feature of this pathway is the assembly of ALT-associated promyelocytic leukemia (PML) nuclear bodies (APBs) at telomeres. Here, we dissected the role of APBs in a human ALT cell line by performing an RNA interference screen using an automated 3D fluorescence microscopy platform and advanced 3D image analysis. We identified 29 proteins that affected APB formation, which included proteins involved in telomere and chromatin organization, protein sumoylation and DNA repair. By integrating and extending these findings, we found that APB formation induced clustering of telomere repeats, telomere compaction and concomitant depletion of the shelterin protein TRF2 (also known as TERF2). These APB-dependent changes correlated with the induction of a DNA damage response at telomeres in APBs as evident by a strong enrichment of the phosphorylated form of the ataxia telangiectasia mutated (ATM) kinase. Accordingly, we propose that APBs promote telomere maintenance by inducing a DNA damage response in ALT-positive tumor cells through changing the telomeric chromatin state to trigger ATM phosphorylation. PMID:25908860

  13. Telomere-associated proteins of typical and alternative telomeres

    Sýkorová, Eva; Rotková, Gabriela; Fajkus, Jiří

    Villars-sur-Ollon, 2006. s. 19-19. [Telomeres and Genome Stability 2006. 30.08.2006-03.09.2006, Villars-sur-Ollon] R&D Projects: GA ČR(CZ) GP204/04/P105; GA ČR(CZ) GA521/05/0055; GA AV ČR(CZ) IAA600040505; GA MŠk(CZ) LC06004 Institutional research plan: CEZ:AV0Z50040507 Keywords : alternative telomeres * DNA-protein interaction Subject RIV: BO - Biophysics

  14. Telomere loss, not average telomere length, confers radiosensitivity to TK6-irradiated cells

    Berardinelli, F.; Nieri, D.; Sgura, A.; Tanzarella, C. [Dip. Di Biologia, Università “Roma Tre”, Rome (Italy); INFN – “Roma Tre”, Rome (Italy); Antoccia, A., E-mail: antoccia@uniroma3.it [Dip. Di Biologia, Università “Roma Tre”, Rome (Italy); INFN – “Roma Tre”, Rome (Italy)

    2012-12-15

    Highlights: ► Ionizing radiation induced telomere lengthening in TK6 clones from a single cell. ► Telomerase is not involved in the telomere lengthening observed. ► TK6 cells display very heterogeneous values in telomere length and telomere loss. ► A selective process account for telomere lengthening in irradiated cells. ► Telomere loss, not mean telomere length, is predictive of radiosensitivity. - Abstract: Many and varied are the proposed mechanisms that lead to resistance to ionizing radiation treatment. Among them, an inverse relationship between telomere length and radioresistance has been recently advanced. Investigating such a relationship in TK6 lymphoblasts, we found that clones originating from cells survived to 4 Gy of X-rays showed a significantly higher telomere length when compared with clones grown from untreated cells. The lengthening observed was not attributable to a radiation-induced increase in telomerase activity, as demonstrated by TRAP assay performed in the dose range of 1–10 Gy. Given the evidence that TK6 whole population was characterized by heterogeneity in cellular mean telomere length and telomere loss, we tested the hypothesis that a process of selection may favour cells with longer telomeres (more radioresistant cells) following exposure to irradiation. In order to do this 15 independent TK6 clones were selected and characterized for telomere length and loss on the basis of q-FISH and flow-FISH analysis. Among the screened clones four characterized by long telomeres and four characterized by short telomeres were tested for their radiosensitivity by means of clonogenic assay. The results obtained showed that, in our experimental conditions (cellular model, radiation doses) no significant correlation was observed between radiosensitivity and mean telomere lengths, whereas a positive correlation was observed with respect to telomere loss. Overall, these results indicate that telomere loss and not mean telomere length plays

  15. Telomere and telomerase in oncology

    2002-01-01

    Shortening of the telomeric DNA at the chromosome ends is presumed to limit the lifespan of human cells and elicit a signal for the onset of cellular senescence. To continually proliferate across the senescent checkpoint, cells must restore and preserve telomere length. This can be achieved by telomerase, which has the reverse transcriptase activity. Telomerase activity is negative in human normal somatic cells but can be detected in most tumor cells. The enzyme is proposed to be an essential factor in cell immortalization and cancer progression. In this review we discuss the structure and function of telomere and telomerase and thefr roles in cell immortalization and oncogenesis. Simultaneously the experimental studies of telomerase assays for cancer detection and diagnosis are reviewed. Finally, we discuss the potential use of inhibitors of telomerase in anti-cancer therapy.

  16. Analysis and location of a rice BAC clone containing telomeric DNA sequences

    翟文学; 陈浩; 颜辉煌; 严长杰; 王国梁; 朱立煌

    1999-01-01

    BAC2, a rice BAC clone containing (TTTAGGG)n homologous sequences, was analyzed by Southern hybridization and DNA sequencing of its subclones. It was disclosed that there were many tandem repeated satellite DNA sequences, called TA352, as well as simple tandem repeats consisting of TTTAGGG or its variant within the BAC2 insert. A 0. 8 kb (TTTAGGG) n-containing fragment in BAC2 was mapped in the telomere regions of at least 5 pairs of rice chromosomes by using fluorescence in situ hybridization (FISH). By RFLP analysis of low copy sequences the BAC2 clone was localized in one terminal region of chromosome 6. All the results strongly suggest that the telomeric DNA sequences of rice are TTTAGGG or its variant, and the linked satellite DNA TA352 sequences belong to telomere-associated sequences.

  17. Individual Telomere Lengths in Chronic Myeloid Leukemia

    Oumar Samassekou

    2009-11-01

    Full Text Available Chronic myeloid leukemia (CML is a neoplasia characterized by proliferation of a myeloid cell lineage and chromosome translocation t(9;22 (q34;q11.2. As in the case of most cancers, the average telomere length in CML cells is shorter than that in normal blood cells. However, there are currently no data available concerning specific individual telomere length in CML. Here, we studied telomere length on each chromosome arm of CML cells. In situ hybridization with peptide nucleic acid probes was performed on CML cells in metaphase. The fluorescence intensity of each specific telomere was converted into kilobases according to the telomere restriction fragment results for each sample. We found differences in telomere length between short arm ends and long arm ends. We observed recurrent telomere length changes as well as telomere length maintenance and elongation in some individual telomeres. We propose a possible involvement of individual telomere length changes to some chromosomal abnormalities in CML. We suggest that individual telomere length maintenance is chromosome arm-specific associated with leukemia cells.

  18. Environmental stresses disrupt telomere length homeostasis.

    Gal Hagit Romano

    Full Text Available Telomeres protect the chromosome ends from degradation and play crucial roles in cellular aging and disease. Recent studies have additionally found a correlation between psychological stress, telomere length, and health outcome in humans. However, studies have not yet explored the causal relationship between stress and telomere length, or the molecular mechanisms underlying that relationship. Using yeast as a model organism, we show that stresses may have very different outcomes: alcohol and acetic acid elongate telomeres, whereas caffeine and high temperatures shorten telomeres. Additional treatments, such as oxidative stress, show no effect. By combining genome-wide expression measurements with a systematic genetic screen, we identify the Rap1/Rif1 pathway as the central mediator of the telomeric response to environmental signals. These results demonstrate that telomere length can be manipulated, and that a carefully regulated homeostasis may become markedly deregulated in opposing directions in response to different environmental cues.

  19. Shelterin Protects Chromosome Ends by Compacting Telomeric Chromatin.

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

    2016-02-11

    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, but 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 accumulate DDR signals and become more accessible to telomere-associated proteins. 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

  20. Characterization and rescue of telomeric abnormalities in ICF syndrome type I fibroblasts.

    Shiran eYehezkel

    2013-02-01

    Full Text Available Mutations in the human DNA methyltransferase 3B (DNMT3B gene lead to ICF (immunodeficiency, centromeric region instability, facial anomalies syndrome type I. We have previously described a telomere-related phenotype in cells from these patients, involving severe hypomethylation of subtelomeric regions, abnormally short telomeres and high levels of telomeric-repeat-containing RNA (TERRA. Here we demonstrate that ICF-patient fibroblasts carry abnormally short telomeres at a low population doubling and enter senescence prematurely. Accordingly, we attempted to rescue the senescence phenotype by ectopic expression of human telomerase, which led to elongated telomeres with hypomethylated subtelomeres. The senescence phenotype was overcome under these conditions, thus dissociating subtelomeric-DNA hypomethylation per se from the senescence phenotype. In addition, we examined whether the subtelomeric methylation could be restored by expression of a normal copy of full length DNMT3B1 in ICF fibroblasts. Ectopic expression of DNMT3B1 failed to rescue the abnormal hypomethylation at subtelomeres. However, partial rescue of subtelomeric-hypomethylation was achieved by co-expression of DNMT3B1 together with DNA methyltransferase 3-like (DNMT3L, encoding a protein that functions as a stimulator of DNMT3A and DNMT3B. DNMT3B1 and DNMT3L are predominantly expressed during early embryonic development, suggesting that de novo subtelomeric DNA methylation during crucial stages of human embryonic development may be necessary for setting and maintaining normal telomere length.

  1. Karyotype rearrangements and telomere analysis in Myzus persicae (Hemiptera, Aphididae strains collected on Lavandula sp. plants

    Mauro Mandrioli

    2014-10-01

    Full Text Available Karyotype analysis of nine strains of the peach-potato aphid Myzus persicae (Sulzer, 1776, collected on Lavandula sp. plants, evidenced showed that five of them had a standard 2n = 12 karyotype, one possessed a fragmentation of the X chromosome occurring at the telomere opposite to the NOR-bearing one and three strains had a chromosome number 2n = 11 due to a non-reciprocal translocation of an autosome A3 onto an A1 chromosome. Interestingly, the terminal portion of the autosome A1 involved in the translocation was the same in all the three strains, as evidenced by FISH with the histone cluster as a probe. The study of telomeres in the M. persicae strain with the X fission evidenced that telomerase synthesised de novo telomeres at the breakpoints resulting in the stabilization of the chromosomal fragments. Lastly, despite the presence of a conserved telomerase, aphid genome is devoid of genes coding for shelterin, a complex of proteins involved in telomere functioning frequently reported as conserved in eukaryotes. The absence of this complex, also confirmed in the genome of other arthropods, suggests that the shift in the sequence of the telomeric repeats has been accompanied by other changes in the telomere components in arthropods in respect to other metazoans.

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

    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)

  3. Nucleolar organization, ribosomal DNA array stability, and acrocentric chromosome integrity are linked to telomere function.

    Kaitlin M Stimpson

    Full Text Available The short arms of the ten acrocentric human chromosomes share several repetitive DNAs, including ribosomal RNA genes (rDNA. The rDNA arrays correspond to nucleolar organizing regions that coalesce each cell cycle to form the nucleolus. Telomere disruption by expressing a mutant version of telomere binding protein TRF2 (dnTRF2 causes non-random acrocentric fusions, as well as large-scale nucleolar defects. The mechanisms responsible for acrocentric chromosome sensitivity to dysfunctional telomeres are unclear. In this study, we show that TRF2 normally associates with the nucleolus and rDNA. However, when telomeres are crippled by dnTRF2 or RNAi knockdown of TRF2, gross nucleolar and chromosomal changes occur. We used the controllable dnTRF2 system to precisely dissect the timing and progression of nucleolar and chromosomal instability induced by telomere dysfunction, demonstrating that nucleolar changes precede the DNA damage and morphological changes that occur at acrocentric short arms. The rDNA repeat arrays on the short arms decondense, and are coated by RNA polymerase I transcription binding factor UBF, physically linking acrocentrics to one another as they become fusogenic. These results highlight the importance of telomere function in nucleolar stability and structural integrity of acrocentric chromosomes, particularly the rDNA arrays. Telomeric stress is widely accepted to cause DNA damage at chromosome ends, but our findings suggest that it also disrupts chromosome structure beyond the telomere region, specifically within the rDNA arrays located on acrocentric chromosomes. These results have relevance for Robertsonian translocation formation in humans and mechanisms by which acrocentric-acrocentric fusions are promoted by DNA damage and repair.

  4. Evolutionary switchpoints in plant telomeres

    Sýkorová, Eva; Lim, K. Y.; Kunická, Zuzana; Chase, M. W.; Bennet, M. D.; Leitch, A. R.; Fajkus, Jiří

    London: Biochemical Society, 2004. s. 28-. [EMBO Workshop / Harden Conference /58./ - Telemeres and Genome Stability . 03.04.2004-07.04.2004, Cambridge] R&D Projects: GA ČR GA204/02/0027; GA ČR GP204/04/P105 Keywords : alternative telomeres in plants * molecular evolution Subject RIV: BO - Biophysics

  5. Telomeres: Their structure and maintenance

    Čapková Frydrychová, Radmila; Mason, J. M.

    Rijeka: InTech, Open Access Publisher, 2013 - (Stuart, D.), s. 423-443 ISBN 978-953-51-0991-4 R&D Projects: GA ČR GAP501/10/1215 Institutional support: RVO:60077344 Keywords : telomeric DNA Subject RIV: EB - Genetics ; Molecular Biology

  6. Telomere dynamics in dyskeratosis congenita: the long and the short of iPS

    Suneet Agarwal; George Q Daley

    2011-01-01

    Seminal experiments by Hayflick in the 1960s demonstrated that normal human diploid cells have a finite replicative life span in culture [1].The Hayflick "limit" is explained at least in part by the decay in telomeres, repeat sequences that cap the ends of chromosomes [2].

  7. Telomere binding protein TRB1 is associated with promoters of translation machinery genes in vivo

    Schrumpfová, P.; Vychodilová, I.; Hapala, J.; Schorová, Š.; Dvořáček, Vojtěch; Fajkus, Jiří

    2016-01-01

    Roč. 90, 1-2 (2016), s. 189-206. ISSN 0167-4412 R&D Projects: GA ČR(CZ) GA13-06943S Institutional support: RVO:68081707 Keywords : Telomere repeat binding * ChIP-seq * Arabidopsis thaliana Subject RIV: BO - Biophysics Impact factor: 4.257, year: 2014

  8. Regulation of homologous recombination at telomeres in budding yeast

    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...

  9. Alternative lengthening of telomeres pathway: recombination-mediated telomere maintenance mechanism in human cells.

    Nabetani, Akira; Ishikawa, Fuyuki

    2011-01-01

    Unlimitedly proliferating cells need to acquire the telomere DNA maintenance mechanism, to counteract possible shortening through multiple rounds of replication and segregation of linear chromosomes. Most human cancer cells express telomerase whereas the other cells utilize the alternative lengthening of telomeres (ALT) pathway to elongate telomere DNA. It is suggested that ALT depends on the recombination between telomere repetitive DNAs. However, the molecular details remain unknown. Recent...

  10. Telomere length is inherited with resetting of the telomere set-point

    Chiang, Y. Jeffrey; Calado, Rodrigo T.; Karen S Hathcock; Lansdorp, Peter M.; Young, Neal S; Richard J Hodes

    2010-01-01

    We have studied models of telomerase haploinsufficiency in humans and mice to analyze regulation of telomere length and the significance of “set points” in inheritance of telomere length. In three families with clinical syndromes associated with short telomeres resulting from haploinsufficient mutations in TERT, the gene encoding telomerase reverse transcriptase, we asked whether restoration of normal genotypes in offspring of affected individuals would elongate inherited short telomeres. Tel...

  11. Nature of telomere dimers and chromosome looping in human spermatozoa

    Solov'eva, Lyudmila; Svetlova, Maria; Bodinski, Dawn; Zalensky, Andrei O.

    2004-01-01

    Specific and well-organized chromosome architecture in human sperm cells is supported by the prominent interactions between centromeres and between telomeres. The telomere-telomere interactions result in telomere dimers that are positioned at the nuclear periphery. It is unknown whether composition of sperm telomere dimers is random or specific. We now report that telomere dimers result from specific interactions between the two ends of each chromosome. FISH using pairs of subtelomeric DNA pr...

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

    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.

  13. Swi1Timeless Prevents Repeat Instability at Fission Yeast Telomeres

    Gadaleta, Mariana C.; Das, Mukund M.; Hideki Tanizawa; Ya-Ting Chang; Ken-ichi Noma; Nakamura, Toru M.; Eishi Noguchi

    2016-01-01

    Genomic instability associated with DNA replication stress is linked to cancer and genetic pathologies in humans. If not properly regulated, replication stress, such as fork stalling and collapse, can be induced at natural replication impediments present throughout the genome. The fork protection complex (FPC) is thought to play a critical role in stabilizing stalled replication forks at several known replication barriers including eukaryotic rDNA genes and the fission yeast mating-type locus...

  14. The evolutionary origin of insect telomeric repeats, (TTAGG)(n)

    Vítková, Magda; Král, J.; Traut, W.; Zrzavý, Jan; Marec, František

    2005-01-01

    Roč. 13, č. 2 (2005), s. 145-156. ISSN 0967-3849 R&D Projects: GA ČR(CZ) GA206/00/0750; GA AV ČR(CZ) KSK5052113 Institutional research plan: CEZ:AV0Z50070508 Keywords : Arthropoda * chromosomes * Onychophora Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.007, year: 2005

  15. Phylogenetic distribution of TTAGG telomeric repeats in insects

    Frydrychová, Radmila; Grossmann, P.; Trubač, P.; Vítková, Magda; Marec, František

    2004-01-01

    Roč. 47, - (2004), s. 163-178. ISSN 0831-2796 R&D Projects: GA AV ČR KSK5052113; GA ČR GA206/00/0750 Institutional research plan: CEZ:AV0Z5007907 Keywords : chromosomes * fluorescence in situ hybridization * FISH Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.100, year: 2004

  16. ATRX represses alternative lengthening of telomeres

    Napier, Christine E.; Huschtscha, Lily I.; Harvey, Adam; Bower, Kylie; Noble, Jane R.; Hendrickson, Eric A.; Reddel, Roger R

    2015-01-01

    The unlimited proliferation of cancer cells requires a mechanism to prevent telomere shortening. Alternative Lengthening of Telomeres (ALT) is an homologous recombination-mediated mechanism of telomere elongation used in tumors, including osteosarcomas, soft tissue sarcoma subtypes, and glial brain tumors. Mutations in the ATRX/DAXX chromatin remodeling complex have been reported in tumors and cell lines that use the ALT mechanism, suggesting that ATRX may be an ALT repressor. We show here th...

  17. Identification of telomere dysfunction in Friedreich ataxia

    Anjomani Virmouni, Sara; Al-Mahdawi, Sahar; Sandi, Chiranjeevi; Yasaei, Hemad; Giunti, Paola; Slijepcevic, Predrag; Mark A. Pook

    2015-01-01

    Background Friedreich ataxia (FRDA) is a progressive inherited neurodegenerative disorder caused by mutation of the FXN gene, resulting in decreased frataxin expression, mitochondrial dysfunction and oxidative stress. A recent study has identified shorter telomeres in FRDA patient leukocytes as a possible disease biomarker. Results Here we aimed to investigate both telomere structure and function in FRDA cells. Our results confirmed telomere shortening in FRDA patient leukocytes and identifie...

  18. Stress and Telomere Biology: A Lifespan Perspective

    Shalev, Idan; Entringer, Sonja; Pathik D Wadhwa; Wolkowitz, Owen M.; Puterman, Eli; Lin, Jue; Epel, Elissa S.

    2013-01-01

    In the past decade, the growing field of telomere science has opened exciting new avenues for understanding the cellular and molecular substrates of stress and stress-related aging processes ver the lifespan. Shorter telomere length is associated with advancing chronological age and also increased disease morbidity and mortality. Emerging studies suggest that stress accelerates the erosion of telomeres from very early in life and possibly even influences the initial (newborn) setting of telom...

  19. Telomere behavior in a hybrid yeast

    Ona C Martin; Christopher G De Sevo; Benjamin Z Guo; Douglas E Koshland; Maiterya J Dunham; Yixian Zheng

    2009-01-01

    @@ Dear Editor, Telomeres and the protein/RNA complexes involved in maintaining them are rapidly evolving systems across eukaryotes.Using two Saccharomyces species, among S.cerevisiae and S.bayanus, we provide evidence that the telomere systems of these two closely related yeasts have evolved significantly apart and that the gene in one spe-cies cannot maintain the set-point of telomere length of the other soecies in the hybrid.

  20. Telomeric circles are abundant in the stn1-M1 mutant that maintains its telomeres through recombination

    Evelina Y Basenko; Cesare, Anthony J.; Iyer, Shilpa; Griffith, Jack D.; McEachern, Michael J.

    2009-01-01

    Some human cancers maintain their telomeres using the alternative lengthening of telomeres (ALT) mechanism; a process thought to involve recombination. Different types of recombinational telomere elongation pathways have been identified in yeasts. In senescing yeast telomerase deletion (ter1-Δ) mutants with very short telomeres, it has been hypothesized that copying a tiny telomeric circle (t-circle) by a rolling circle mechanism is the key event in telomere elongation. In other cases more cl...

  1. Paternal age and telomere length in twins

    Hjelmborg, Jacob B; Dalgård, Christine; Mangino, Massimo; Spector, Tim D; Halekoh, Ulrich; Möller, Sören; Kimura, Masayuki; Horvath, Kent; Kark, Jeremy D; Christensen, Kaare; Kyvik, Kirsten O; Aviv, Abraham

    2015-01-01

    Telomere length, a highly heritable trait, is longer in offspring of older fathers. This perplexing feature has been attributed to the longer telomeres in sperm of older men and it might be an 'epigenetic' mechanism through which paternal age plays a role in telomere length regulation in humans....... Based on two independent (discovery and replication) twin studies, comprising 889 twin pairs, we show an increase in the resemblance of leukocyte telomere length between dizygotic twins of older fathers, which is not seen in monozygotic twins. This phenomenon might result from a paternal age...

  2. Leukocyte telomere dynamics in the elderly

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

    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 of the...... years, assuming a 340 bp attrition during this period. This was not significantly different from the empirical observation of 7.5 % of individuals showing LTL elongation. We conclude that accumulation of ultra-short telomeres in leukocytes of the elderly reflects a shift toward shorter telomeres in the...

  3. Origin and Evolution of Telomeres

    Fajkus, Jiří; Leitch, A.R.; Chester, M.; Sýkorová, Eva

    Austin : Landes Bioscience, 2008 - (Nosek, J.; Tomáška, L.), s. 114-127 ISBN 978-1-58706-309-1 R&D Projects: GA ČR(CZ) GA521/05/0055; GA AV ČR(CZ) IAA600040505; GA MŠk(CZ) LC06004 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : evolution * telomere * plant Subject RIV: BO - Biophysics

  4. Quadruplexes of human telomere DNA

    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

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

    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.

  6. Exposure to violence during childhood is associated with telomere erosion from 5 to 10 years of age: a longitudinal study.

    Shalev, I; Moffitt, T E; Sugden, K; Williams, B; Houts, R M; Danese, A; Mill, J; Arseneault, L; Caspi, A

    2013-05-01

    There is increasing interest in discovering mechanisms that mediate the effects of childhood stress on late-life disease morbidity and mortality. Previous studies have suggested one potential mechanism linking stress to cellular aging, disease and mortality in humans: telomere erosion. We examined telomere erosion in relation to children's exposure to violence, a salient early-life stressor, which has known long-term consequences for well-being and is a major public-health and social-welfare problem. In the first prospective-longitudinal study with repeated telomere measurements in children while they experienced stress, we tested the hypothesis that childhood violence exposure would accelerate telomere erosion from age 5 to age 10 years. Violence was assessed as exposure to maternal domestic violence, frequent bullying victimization and physical maltreatment by an adult. Participants were 236 children (49% females; 42% with one or more violence exposures) recruited from the Environmental-Risk Longitudinal Twin Study, a nationally representative 1994-1995 birth cohort. Each child's mean relative telomere length was measured simultaneously in baseline and follow-up DNA samples, using the quantitative PCR method for T/S ratio (the ratio of telomere repeat copy numbers to single-copy gene numbers). Compared with their counterparts, the children who experienced two or more kinds of violence exposure showed significantly more telomere erosion between age-5 baseline and age-10 follow-up measurements, even after adjusting for sex, socioeconomic status and body mass index (B=-0.052, s.e.=0.021, P=0.015). This finding provides support for a mechanism linking cumulative childhood stress to telomere maintenance, observed already at a young age, with potential impact for life-long health. PMID:22525489

  7. SUMO-Dependent Relocalization of Eroded Telomeres to Nuclear Pore Complexes Controls Telomere Recombination

    Dmitri Churikov

    2016-05-01

    Full Text Available In budding yeast, inactivation of telomerase and ensuing telomere erosion cause relocalization of telomeres to nuclear pore complexes (NPCs. However, neither the mechanism of such relocalization nor its significance are understood. We report that proteins bound to eroded telomeres are recognized by the SUMO (small ubiquitin-like modifier-targeted ubiquitin ligase (STUbL Slx5-Slx8 and become increasingly SUMOylated. Recruitment of Slx5-Slx8 to eroded telomeres facilitates telomere relocalization to NPCs and type II telomere recombination, a counterpart of mammalian alternative lengthening of telomeres (ALT. Moreover, artificial tethering of a telomere to a NPC promotes type II telomere recombination but cannot bypass the lack of Slx5-Slx8 in this process. Together, our results indicate that SUMOylation positively contributes to telomere relocalization to the NPC, where poly-SUMOylated proteins that accumulated over time have to be removed. We propose that STUbL-dependent relocalization of telomeres to NPCs constitutes a pathway in which excessively SUMOylated proteins are removed from “congested” intermediates to ensure unconventional recombination.

  8. SUMO-Dependent Relocalization of Eroded Telomeres to Nuclear Pore Complexes Controls Telomere Recombination.

    Churikov, Dmitri; Charifi, Ferose; Eckert-Boulet, Nadine; Silva, Sonia; Simon, Marie-Noelle; Lisby, Michael; Géli, Vincent

    2016-05-10

    In budding yeast, inactivation of telomerase and ensuing telomere erosion cause relocalization of telomeres to nuclear pore complexes (NPCs). However, neither the mechanism of such relocalization nor its significance are understood. We report that proteins bound to eroded telomeres are recognized by the SUMO (small ubiquitin-like modifier)-targeted ubiquitin ligase (STUbL) Slx5-Slx8 and become increasingly SUMOylated. Recruitment of Slx5-Slx8 to eroded telomeres facilitates telomere relocalization to NPCs and type II telomere recombination, a counterpart of mammalian alternative lengthening of telomeres (ALT). Moreover, artificial tethering of a telomere to a NPC promotes type II telomere recombination but cannot bypass the lack of Slx5-Slx8 in this process. Together, our results indicate that SUMOylation positively contributes to telomere relocalization to the NPC, where poly-SUMOylated proteins that accumulated over time have to be removed. We propose that STUbL-dependent relocalization of telomeres to NPCs constitutes a pathway in which excessively SUMOylated proteins are removed from "congested" intermediates to ensure unconventional recombination. PMID:27134164

  9. Stable expression of promyelocytic leukaemia (PML protein in telomerase positive MCF7 cells results in alternative lengthening of telomeres phenotype

    Yong Jacklyn W Y

    2012-08-01

    Full Text Available Abstract Background Cancer cells can employ telomerase or the alternative lengthening of telomeres (ALT pathway for telomere maintenance. Cancer cells that use the ALT pathway exhibit distinct phenotypes such as heterogeneous telomeres and specialised Promyelocytic leukaemia (PML nuclear foci called APBs. In our study, we used wild-type PML and a PML mutant, in which the coiled-coil domain is deleted (PML C/C-, to investigate how these proteins can affect telomere maintenance pathways in cancer cells that use either the telomerase or ALT pathway. Results Stable over-expression of both types of PML does not affect the telomere maintenance in the ALT cells. We report novel observations in PML over-expressed telomerase-positive MCF7 cells: 1 APBs are detected in telomerase-positive MCF7 cells following over-expression of wild-type PML and 2 rapid telomere elongation is observed in MCF7 cells that stably express either wild-type PML or PML C/C-. We also show that the telomerase activity in MCF7 cells can be affected depending on the type of PML protein over-expressed. Conclusion Our data suggests that APBs might not be essential for the ALT pathway as MCF7 cells that do not contain APBs exhibit long telomeres. We propose that wild-type PML can either definitively dominate over telomerase or enhance the activity of telomerase, and PML C/C- can allow for the co-existence of both telomerase and ALT pathways. Our findings add another dimension in the study of telomere maintenance as the expression of PML alone (wild-type or otherwise is able to change the dynamics of the telomerase pathway.

  10. Single-Cell Telomere-Length Quantification Couples Telomere Length to Meristem Activity and Stem Cell Development in Arabidopsis

    Mary-Paz González-García

    2015-05-01

    Full Text Available 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.

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

    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. PMID:25937286

  12. Is telomere length a biomarker for aging: cross-sectional evidence from the west of Scotland?

    Geoff Der

    Full Text Available BACKGROUND: The search for biomarkers of aging (BoAs has been largely unsuccessful to-date and there is widespread skepticism about the prospects of finding any that satisfy the criteria developed by the American Federation of Aging Research. This may be because the criteria are too strict or because a composite measure might be more appropriate. Telomere length has attracted a great deal of attention as a candidate BoA. We investigate whether it meets the criteria to be considered as a single biomarker of aging, and whether it makes a useful contribution to a composite measure. METHODOLOGY/PRINCIPAL FINDINGS: Using data from a large population based study, we show that telomere length is associated with age, with several measures of physical and cognitive functioning that are related to normal aging, and with three measures of overall health. In the majority of cases, telomere length adds predictive power to that of age, although it was not nearly as good a predictor overall. We used principal components analysis to form two composites from the measures of functioning, one including telomere length and the other not including it. These composite BoAs were better predictors of the health outcomes than chronological age. There was little difference between the two composites. CONCLUSIONS: Telomere length does not satisfy the strict criteria for a BoA, but does add predictive power to that of chronological age. Equivocal results from previous studies might be due to lack of power or the choice of measures examined together with a focus on single biomarkers. Composite biomarkers of aging have the potential to outperform age and should be considered for future research in this area.

  13. Distribution of Telomeric Sequences (TTAGGG)n in Rearranged Chromosomes of Phyllotine Rodents (Cricetidae, Sigmodontinae).

    Lanzone, Cecilia; Labaroni, Carolina; Suárez, Natalia; Rodríguez, Daniela; Herrera, Macarena L; Bolzán, Alejandro D

    2015-01-01

    Phyllotines are sigmodontine rodents endemic to South America with broad genetic variability, Robertsonian polymorphisms being the most frequent. Moreover, this taxon includes a species with multiple sex chromosomes, which is infrequent in mammals. However, molecular cytogenetic techniques have never been applied to phyllotines to elucidate their karyotypic evolution. We studied the chromosomes of 4 phyllotine species using FISH with a pantelomeric probe (TTAGGG)n. Graomys griseoflavus, Eligmodontia puerulus, and E. morgani are polymorphic for Robertsonian translocations, whereas Salinomys delicatus possesses XX/ XY1Y2 sex chromosomes. Telomeric signals were detected at both ends of all chromosomes of the studied species. In S. delicatus interstitial telomeric sequences (ITS) were observed in the 3 major chromosome pairs, which are equidistant from one of the telomeres in these chromosomes. These results suggest that ITS are important in the reshuffling of the highly derived karyotype of S. delicatus. Considering the phylogeny of phyllotines, the Robertsonian rearrangements of G. griseoflavus, E. puerulus, and E. morgani possibly represent chromosome fusions which have occurred independently. The pericentromeric regions of the biarmed chromosomes of these species do not contain telomeric sequences characteristic for strict fusions of recent origin, suggesting a common pattern of telomeric repeat loss during chromosomal evolution of these rodents. PMID:27035350

  14. Telomere biology in healthy aging and disease

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

    2010-01-01

    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 nucleoti

  15. Long telomeres: too much of a good thing

    Chang, Michael

    2012-01-01

    Telomeres, the physical ends of linear eukaryotic chromosomes, protect chromosome ends from end fusions and degradation. Telomere length is tightly regulated to ensure that telomeres are neither too short nor too long. Short telomeres are preferentially elongated by the enzyme telomerase. In the abs

  16. Are Drosophila telomeres an exception or the rule?

    Louis, Edward J.

    2002-01-01

    At the ends of eukaryotic chromosomes are telomeres, specialized structures with unusual properties. The repetitive structure of telomere regions makes them difficult to deal with in general genome-sequencing projects. Specific efforts to compare sequences and properties of telomeres across species can reveal the generalities of telomere properties.

  17. Telomere Length Reprogramming in Embryos and Stem Cells

    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.

  18. An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres

    Wang, Yisong [ORNL; Giannone, Richard J [ORNL; Wu, Jun [ORNL; Gomez, Marla V [ORNL; Liu, Yie [ORNL

    2005-01-01

    Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient (mTert -/-) splenocytes and ES cells. Because telomerase deficiency leads to gradual loss of telomeric DNA in mTert -/- splenocytes and ES cells and eventually to chromosomes with telomere signal-free ends (SFEs), we examined these cell types for evidence of sister chromatid exchange at telomeres, and observed an increase in T-SCEs only in a subset of mTert -/- splenocytes or ES cells that possessed multiple SFEs. Furthermore, T-SCEs were more often detected in ES cells than in splenocytes that harbored a similar frequency of SFEs. In mTert heterozygous (mTert +/-) ES cells or splenocytes, which are known to exhibit a decrease in average telomere length but no SFEs, no increase in T-SCE was observed. In addition to T-SCE, other genomic rearrangements (i.e., SCE) were also significantly increased in mTert -/- ES cells possessing critically short telomeres, but not in splenocytes. Our results suggest that animals and cell culture differ in their ability to carry out genomic rearrangements as a means of maintaining telomere integrity when telomeres become critically shortened.

  19. The proper connection between shelterin components is required for telomeric heterochromatin assembly.

    Wang, Jiyong; Cohen, Allison L; Letian, Anudari; Tadeo, Xavier; Moresco, James J; Liu, Jinqiang; Yates, John R; Qiao, Feng; Jia, Songtao

    2016-04-01

    Telomeric regions contain prominent sites of heterochromatin, which is associated with unique histone modification profiles such as the methylation of histone H3 at Lys9 (H3K9me). In fission yeast, the conserved telomeric shelterin complex recruits the histone H3K9 methyltransferase complex CLRC to establish subtelomeric heterochromatin. Although many shelterin mutations affect subtelomeric heterochromatin assembly, the mechanism remains elusive due to the diverse functions of shelterin. Through affinity purification, we found that shelterin directly associates with CLRC through the Ccq1 subunit. Surprisingly, mutations that disrupt interactions between shelterin subunits compromise subtelomeric heterochromatin without affecting CLRC interaction with shelterin component Pot1, located at chromosome ends. We further discovered that telomeric repeats are refractory to heterochromatin spreading and that artificial restoration of shelterin connections or increased heterochromatin spreading rescued heterochromatin defects in these shelterin mutants. Thus, subtelomeric heterochromatin assembly requires both the recruitment of CLRC by shelterin to chromosome ends and the proper connection of shelterin components, which allows CLRC to skip telomeric repeats to internal regions. PMID:26988418

  20. Alternative lengthening of telomeres in normal mammalian somatic cells

    Neumann, Axel A.; Watson, Catherine M.; Noble, Jane R.; Hilda A Pickett; Tam, Patrick P.L.; Reddel, Roger R

    2013-01-01

    Alternative lengthening of telomeres (ALT), a mechanism involving the replication of new telomeric DNA from a DNA template, is used by some cancer cells to lengthen their telomeres. Reddel and colleagues now show that ALT activity exists in normal somatic tissues as well. A telomere with a DNA tag is found to be intertelomerically copied in normal somatic cells but not germline cells, providing important implications for understanding telomere maintenance and its evolution.

  1. Interchromosomal Homology Searches Drive Directional ALT Telomere Movement and Synapsis

    Cho, Nam Woo; Dilley, Robert L.; Lampson, Michael A.; Greenberg, Roger A.

    2014-01-01

    Telomere length maintenance is a requisite feature of cellular immortalization and a hallmark of human cancer. While most human cancers express telomerase activity, approximately 10-15% employ a recombination-dependent telomere maintenance pathway known as Alternative Lengthening of Telomeres (ALT) that is characterized by multi-telomere clusters and associated promyelocytic leukemia protein bodies. Here, we show that a DNA double-strand break (DSB) response at ALT telomeres triggers long-ran...

  2. Telomere Length Reprogramming in Embryos and Stem Cells

    Keri Kalmbach; LeRoy G. Robinson; Fang Wang; Lin Liu; David Keefe

    2014-01-01

    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 re...

  3. The association between intelligence and telomere length: a longitudinal population based study.

    Eva M Kingma

    Full Text Available Low intelligence has been associated with poor health and mortality, but underlying mechanisms remain obscure. We hypothesized that low intelligence is associated with accelerated biological ageing as reflected by telomere length; we suggested potential mediation of this association by unhealthy behaviors and low socioeconomic position. The study was performed in a longitudinal population-based cohort study of 895 participants (46.8% males. Intelligence was measured with the Generalized Aptitude-Test Battery at mean age 52.8 years (33-79 years, SD=11.3. Leukocyte telomere length was measured by PCR. Lifestyle and socioeconomic factors were assessed using written self-report measures. Linear regression analyses, adjusted for age, sex, and telomere length measured at the first assessment wave (T1, showed that low intelligence was associated with shorter leukocyte telomere length at approximately 2 years follow-up (beta= .081, t=2.160, p= .031. Nearly 40% of this association was explained by an unhealthy lifestyle, while low socioeconomic position did not add any significant mediation. Low intelligence may be a risk factor for accelerated biological ageing, thereby providing an explanation for its association with poor health and mortality.

  4. First evidence for (TTAGG)n telomeric sequence and sex chromosome post-reduction in Coleorrhyncha (Insecta, Hemiptera)

    Kuznetsova, Valentina G.; Grozeva, Snejana M.; Hartung, Viktor; Anokhin, Boris A.

    2015-01-01

    Abstract Telomeric repeats are general and significant structures of eukaryotic chromosomes. However, nothing is known about the molecular structure of telomeres in the enigmatic hemipteran suborder Coleorrhyncha (moss bugs) commonly considered as the sister group to the suborder Heteroptera (true bugs). The true bugs are known to differ from the rest of the Hemiptera in that they display an inverted sequence of sex chromosome divisions in male meiosis, the so-called sex chromosome post-reduction. To date, there has been no information about meiosis in Coleorrhyncha. Here we report a cytogenetic observation of Peloridium pomponorum, a representative of the single extant coleorrhynchan family Peloridiidae, using the standard chromosome staining and fluorescence in situ hybridization (FISH) with a (TTAGG)n telomeric probe. We show that Peloridium pomponorum displays 2n = 31 (30A + X) in males, the classical insect (TTAGG)n telomere organization and sex chromosome post-reduction during spermatocyte meiosis. The plesiomorphic insect-type (TTAGG)n telomeric sequence is suggested to be preserved in Coleorrhyncha and in a basal heteropteran infraorder Nepomorpha, but absent (lost) in the advanced heteropteran lineages Cimicomorpha and Pentatomomorpha. The telomere structure in other true bug infraorders is currently unknown. We consider here the inverted sequence of sex chromosome divisions as a synapomorphy of the group Coleorrhyncha + Heteroptera. PMID:26753072

  5. RNaseH1 regulates TERRA-telomeric DNA hybrids and telomere maintenance in ALT tumour cells

    Arora, Rajika; Lee, Yongwoo; Wischnewski, Harry; Brun, Catherine M.; Schwarz, Tobias; Azzalin, Claus M.

    2014-01-01

    A fraction of cancer cells maintain telomeres through the telomerase-independent, ‘Alternative Lengthening of Telomeres’ (ALT) pathway. ALT relies on homologous recombination (HR) between telomeric sequences; yet, what makes ALT telomeres recombinogenic remains unclear. Here we show that the RNA endonuclease RNaseH1 regulates the levels of RNA–DNA hybrids between telomeric DNA and the long noncoding RNA TERRA, and is a key mediator of telomere maintenance in ALT cells. RNaseH1 associated to t...

  6. Repeated Miscarriage

    f AQ FREQUENTLY ASKED QUESTIONS FAQ100 PREGNANCY Repeated Miscarriages • What is recurrent pregnancy loss? • What is the likelihood of having repeated miscarriages? • What is the most common cause of miscarriage? • ...

  7. Long Telomeres are Preferentially Extended During Recombination-Mediated Telomere Maintenance

    Chang, Michael; Dittmar, John C; Rothstein, Rodney

    2011-01-01

    Most human somatic cells do not express telomerase. Consequently, with each cell division their telomeres progressively shorten until replicative senescence is induced. Approximately 15% of human cancers maintain their telomeres using telomerase-independent, recombination-based mechanisms collectively termed Alternative Lengthening of Telomeres (ALT). In the yeast Saccharomyces cerevisiae, ALT cells are referred to as “survivors”. One type of survivor (type II) resembles human ALT cells in th...

  8. Reduced Fetal Telomere Length in Gestational Diabetes

    Xu, Jian; Ye, Junyi; Wu, Yanting; Zhang, Hong; Luo, Qiong; Han, Cong; Ye, Xiaoqun; Wang, Hanzhi; Jing HE; Huang, Hefeng; Liu, Yun; Dong, Minyue

    2014-01-01

    Gestational diabetes mellitus (GDM) is an important complication of pregnancy that poses significant threats to women and their offspring. Telomere length shortens as cellular damage increases and is associated with metabolic diseases. Telomere length in fetal leucocytes was determined in 82 infants of women with GDM (N = 82) and 65 normal pregnant women (N = 65). Women with preeclampsia (N = 45) and gestational hypertension (N = 23) were also studied. In the GDM group, telomere length was si...

  9. Add-A-Source technique

    Counting neutrons emitted by spontaneously fissioning plutonium isotopes is a means for determining Plutonium content in samples. Correlations techniques have been developed for separating such neutrons from a background of nonfission neutrons due to (α, n) reactions. Further procedures are then used to correct the effect of neutron-induced fission. In order to perform such a correction the sample's chemical composition (including the presence of moisture) must be a well known parameter. The present paper reports a theoretical formulation of a new approach (add-a-source technique), which could allow to correct the measurement indipendently by the knowledge of the sample's chemical composition

  10. Ataxia telangiectasia mutated (Atm) is not required for telomerase-mediated elongation of short telomeres

    Feldser, David; Strong, Margaret A.; Greider, Carol W

    2006-01-01

    Telomerase-mediated telomere addition counteracts telomere shortening due to incomplete DNA replication. Short telomeres are the preferred substrate for telomere addition by telomerase; however, the mechanism by which telomerase recognizes short telomeres is unclear. In yeast, the Ataxia telangiectasia mutated (Atm) homolog, Tel1, is necessary for normal telomere length regulation likely by altering telomere structure, allowing telomerase recruitment to short telomeres. To examine the role of...

  11. The telomere bouquet regulates meiotic centromere assembly.

    Klutstein, Michael; Fennell, Alex; Fernández-Álvarez, Alfonso; Cooper, Julia Promisel

    2015-04-01

    The role of the conserved meiotic telomere bouquet has been enigmatic for over a century. We showed previously that disruption of the fission yeast bouquet impairs spindle formation in approximately half of meiotic cells. Surprisingly, bouquet-deficient meiocytes with functional spindles harbour chromosomes that fail to achieve spindle attachment. Kinetochore proteins and the centromeric histone H3 variant Cnp1 fail to localize to those centromeres that exhibit spindle attachment defects in the bouquet's absence. The HP1 orthologue Swi6 also fails to bind these centromeres, suggesting that compromised pericentromeric heterochromatin underlies the kinetochore defects. We find that centromeres are prone to disassembly during meiosis, but this is reversed by localization of centromeres to the telomere-proximal microenvironment, which is conducive to heterochromatin formation and centromere reassembly. Accordingly, artificially tethering a centromere to a telomere rescues the tethered centromere but not other centromeres. These results reveal an unanticipated level of control of centromeres by telomeres. PMID:25774833

  12. A human telomerase holoenzyme protein required for Cajal body localization and telomere synthesis

    Venteicher, Andrew S.; Abreu, Eladio B.; Meng, Zhaojing; McCann, Kelly E.; Terns, Rebecca M.; Veenstra, Timothy D.; Terns, Michael P.; Artandi, Steven E.

    2009-01-01

    Telomerase is a ribonucleoprotein (RNP) complex that synthesizes telomere repeats in tissue progenitor cells and cancer cells. Active human telomerase consists of at least three principal subunits, including the telomerase reverse transcriptase (TERT), the telomerase RNA (TERC), and dyskerin. Here, we identify a holoenzyme subunit, TCAB1 (telomerase Cajal body protein1), uniquely enriched in Cajal bodies, nuclear sites of RNP processing important for telomerase function. TCAB1 associates with...

  13. Chromatid interchanges at intrachromosomal telomeric DNA sequences

    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)

  14. [Telomere Recombination in Normal Mammalian Cells].

    Zhdanova, N S; Rubtsov, N B

    2016-01-01

    Two mechanisms of telomere length maintenance are known to date. The first includes the use of a special enzymatic telomerase complex to solve the problems that arise during the replication of linear DNA in a normal diploid and part of tumor cells. Alternative lengthening of telomeres (ALT), which is based on the homologous recombination of telomere DNA, represents the second mechanism. Until recently, ALT was assumed to be expressed only in 15-20% of tumors lacking active telomerase and, together with telomerase reactivation represented one of two possibilities to overcome the replicative senescence observed in somatic mammalian cells due to aging or during cell culturing in vitro. Previously described sporadic cases of combinations of the two mechanisms of telomere length maintenance in several cell lines in vitro were attributed to the experimental design rather than to a real biological phenomenon, since active cellular division without active telomerase was considered to be the "gold standard" of ALT. The present review describes the morphological and functional reorganizations of mammalian telomeres observed with ALT activation, as well as recently observed,and well-documented cases of combinations between ALT-like and telomerase-dependent mechanisms in mammalian cells. The possible role of telomere recombination in telomerase-dependent cells is discussed. PMID:27183789

  15. Conventional anticancer therapeutics and telomere maintenance mechanisms.

    Uziel, Orit; Lahav, Meir

    2014-01-01

    The telomere-telomerase system has a unique role in the biology of cancer. Telomere maintenance, mostly affected by the up regulation of telomerase activity, is a prerequisite for perpetuation of malignant cells. This fundamental biologic feature defines telomere maintenance as an attractive therapeutic target for most types of cancer. This review summarizes some critical aspects of telomere biology with special emphasis on the connection to anticancer therapy. In particular, the effects on the telomere - telomerase system of conventional anticancer treatments, including various cytotoxic drugs, targeted biological agents and radiotherapy, and their possible combination with telomerase-directed therapy are discussed. Several potential problems, including side effects and complications inherent to perturbations of telomere biology in normal cells, are also highlighted. In spite of significant progress in this field, there are still several issues that have to be addressed and ultimately resolved in order to obtain a better characterization of the pros and cons of telomerase-directed therapies and, consequently, their clinical relevance. PMID:24975606

  16. Telomere--the twilight to immortality.

    Shukla, Samarth; Acharya, Sourya; Rajput, Devendra; Vagha, S; Grover, Shobha

    2010-09-01

    Besides forming a very important component of the chromosome, the telomeres have extremely significant modes of action and functions, right from maintaining a basic infrastructure and integrity of the chromosome vis a vis the other chromosomes, telomeres are responsible for the cell divisions and replicative senescence of the cell. The number of mitotic divisions which a cell will go through in its life span while passing through the cell cycle is governed inturn by these telomeres, the crux of the entire functioning of these chromosomal components suggests that they are the ticking clocks of the cell and when they diminish or are worn out so does the cell reach it's senility at the fag end of it's replicative life--resulting fate being--the cell is sent to it's grave yard (the final destination). Clinical implications include--regulation of cell life spans, regulating the cell's replicative behavior and it's utility in forming cells which usually are impossible to divide or replicate, telomeres regulate the cloning process,the telomeres play a major role in predicting the fate of a neoplastic cell and finally enhancing the life span of a single cell, the organ, the body as a whole by enzymes which expand the telomeres--the telomerase. PMID:21391375

  17. Functional diversification of yeast telomere associated protein, Rif1, in higher eukaryotes

    Sreesankar Easwaran

    2012-06-01

    Full Text Available Abstract Background Telomeres are nucleoprotein complexes at the end of linear eukaryotic chromosomes which maintain the genome integrity by regulating telomere length, preventing recombination and end to end fusion events. Multiple proteins associate with telomeres and function in concert to carry out these functions. Rap1 interacting factor 1 (Rif1, was identified as a protein involved in telomere length regulation in yeast. Rif1 is conserved upto mammals but its function has diversified from telomere length regulation to maintenance of genome integrity. Results We have carried out detailed bioinformatic analyses and identified Rif1 homologues in 92 organisms from yeast to human. We identified Rif1 homologues in Drosophila melanogaster, even though fly telomeres are maintained by a telomerase independent pathway. Our analysis shows that Drosophila Rif1 (dRif1 sequence is phylogenetically closer to the one of vertebrates than yeast and has identified a few Rif1 specific motifs conserved through evolution. This includes a Rif1 family specific conserved region within the HEAT repeat domain and a motif involved in protein phosphatase1 docking. We show that dRif1 is nuclear localized with a prominent heterochromatin association and unlike human Rif1, it does not respond to DNA damage by localizing to damaged sites. To test the evolutionary conservation of dRif1 function, we expressed the dRif1 protein in yeast and HeLa cells. In yeast, dRif1 did not perturb yeast Rif1 (yRif1 functions; and in HeLa cells it did not colocalize with DNA damage foci. Conclusions Telomeres are maintained by retrotransposons in all Drosophila species and consequently, telomerase and many of the telomere associated protein homologues are absent, including Rap1, which is the binding partner of Rif1. We found that a homologue of yRif1 protein is present in fly and dRif1 has evolutionarily conserved motifs. Functional studies show that dRif1 responds differently to DNA

  18. Unique C. elegans telomeric overhang structures reveal the evolutionarily conserved properties of telomeric DNA.

    Školáková, Petra; Foldynová-Trantírková, Silvie; Bednářová, Klára; Fiala, Radovan; Vorlíčková, Michaela; Trantírek, Lukáš

    2015-05-19

    There are two basic mechanisms that are associated with the maintenance of the telomere length, which endows cancer cells with unlimited proliferative potential. One mechanism, referred to as alternative lengthening of telomeres (ALT), accounts for approximately 10-15% of all human cancers. Tumours engaged in the ALT pathway are characterised by the presence of the single stranded 5'-C-rich telomeric overhang (C-overhang). This recently identified hallmark of ALT cancers distinguishes them from healthy tissues and renders the C-overhang as a clear target for anticancer therapy. We analysed structures of the 5'-C-rich and 3'-G-rich telomeric overhangs from human and Caenorhabditis elegans, the recently established multicellular in vivo model of ALT tumours. We show that the telomeric DNA from C. elegans and humans forms fundamentally different secondary structures. The unique structural characteristics of C. elegans telomeric DNA that are distinct not only from those of humans but also from those of other multicellular eukaryotes allowed us to identify evolutionarily conserved properties of telomeric DNA. Differences in structural organisation of the telomeric DNA between the C. elegans and human impose limitations on the use of the C. elegans as an ALT tumour model. PMID:25855805

  19. p53 Prevents Entry into Mitosis with Uncapped Telomeres

    Thanasoula, Maria; Escandell, Jose Miguel; Martinez, Paula; Badie, Sophie; Muñoz, Purificacion; Blasco, María A.; Tarsounas, Madalena

    2016-01-01

    Summary Telomeres are protected by capping structures consisting of core protein complexes that bind with sequence specificity to telomeric DNA (reviewed in [1]). In their absence, telomeres trigger a DNA damage response, materialized in accumulation at the telomere of damage response proteins, e.g., phosphorylated histone H2AX (γH2AX), into telomere-dysfunction-induced foci [2, 3]. Telomere uncapping occurs transiently in every cell cycle in G2 [4], following DNA replication, but little is known about how protective structures are reassembled or whether this process is controlled by the cell-cycle surveillance machinery. Here, we report that telomere capping is monitored at the G2/M transition by the p53/p21 damage response pathway. Unlike their wild-type counterparts, human and mouse cells lacking p53 or p21 progress into mitosis prematurely with persisting uncapped telomeres. Furthermore, artificially uncapped telomeres delay mitotic entry in a p53- and p21-dependent manner. Uncapped telomeres that persist in mitotic p53-deficient cells are shorter than average and religate to generate end-to-end fusions. These results suggest that a p53-dependent pathway monitors telomere capping after DNA replication and delays G2/M progression in the presence of unprotected telomeres. This mechanism maintains a cell-cycle stage conducive for capping reactions and prevents progression into stages during which uncapped telomeres are prone to deleterious end fusions. PMID:20226664

  20. Conformational variability of recombination R-triplex formed by the mammalian telomeric sequence.

    Shchyolkina, Anna K; Kaluzhny, Dmitry N; Borisova, Olga F; Arndt-Jovin, Donna J; Jovin, Thomas M; Zhurkin, Victor B

    2016-06-01

    Alignment of three nucleic acids strands, in which the third strand is identical to one of the DNA duplex strands, occurs in various cellular systems. In the case of telomeric t-loops, recognition between the DNA duplex and the homologous single strand is likely to be mediated by proteins through formation of the transient recombination-type R-triplex. Earlier, using 2-aminopurine as a fluorescent reporting base, we evaluated the thermodynamic characteristics of intramolecular R-triplex formed by a mixed nucleotide sequence. Here, we used this approach to explore a propensity of the telomeric TTAGGG repeat to form the R-triplex. The circular dichroism spectral changes detected upon formation of the R-triplex suggest that this process is accompanied by specific conformational changes in DNA, including a local destabilization of the target duplex next to a GGG run revealed by the fluorescence of the reporting 2-aminopurine base. Surprisingly, stability of the R-triplex formed by telomeric sequence depends strikingly on the counter ion, being higher for Na(+) than for Li(+). Taken together these findings indicate a significant conformational variability of telomeric DNA in the context of recombination-type R-triplex, a phenomenon of possible biological relevance. PMID:26308235

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

    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.

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

    Bender, Hannah S; Murchison, Elizabeth P; Pickett, Hilda A; Deakin, Janine E; Strong, Margaret A; Conlan, Carly; McMillan, Daniel A; Neumann, Axel A; Greider, Carol W; Hannon, Gregory J; Reddel, Roger R; Graves, Jennifer A Marshall

    2012-01-01

    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. PMID:23049977

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

    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.

  4. Mice with Pulmonary Fibrosis Driven by Telomere Dysfunction

    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.

  5. SMARCAL1 Resolves Replication Stress at ALT Telomeres.

    Cox, Kelli E; Maréchal, Alexandre; Flynn, Rachel Litman

    2016-02-01

    Cancer cells overcome replicative senescence by exploiting mechanisms of telomere elongation, a process often accomplished by reactivation of the enzyme telomerase. However, a subset of cancer cells lack telomerase activity and rely on the alternative lengthening of telomeres (ALT) pathway, a recombination-based mechanism of telomere elongation. Although the mechanisms regulating ALT are not fully defined, chronic replication stress at telomeres might prime these fragile regions for recombination. Here, we demonstrate that the replication stress response protein SMARCAL1 is a critical regulator of ALT activity. SMARCAL1 associates with ALT telomeres to resolve replication stress and ensure telomere stability. In the absence of SMARCAL1, persistently stalled replication forks at ALT telomeres deteriorate into DNA double-strand breaks promoting the formation of chromosome fusions. Our studies not only define a role for SMARCAL1 in ALT telomere maintenance, but also demonstrate that resolution of replication stress is a crucial step in the ALT mechanism. PMID:26832416

  6. SMARCAL1 Resolves Replication Stress at ALT Telomeres

    Kelli E. Cox

    2016-02-01

    Full Text Available Cancer cells overcome replicative senescence by exploiting mechanisms of telomere elongation, a process often accomplished by reactivation of the enzyme telomerase. However, a subset of cancer cells lack telomerase activity and rely on the alternative lengthening of telomeres (ALT pathway, a recombination-based mechanism of telomere elongation. Although the mechanisms regulating ALT are not fully defined, chronic replication stress at telomeres might prime these fragile regions for recombination. Here, we demonstrate that the replication stress response protein SMARCAL1 is a critical regulator of ALT activity. SMARCAL1 associates with ALT telomeres to resolve replication stress and ensure telomere stability. In the absence of SMARCAL1, persistently stalled replication forks at ALT telomeres deteriorate into DNA double-strand breaks promoting the formation of chromosome fusions. Our studies not only define a role for SMARCAL1 in ALT telomere maintenance, but also demonstrate that resolution of replication stress is a crucial step in the ALT mechanism.

  7. Quantum dots thermal stability improves simultaneous phenotype-specific telomere length measurement by FISH-flow cytometry.

    Kapoor, Veena; Hakim, Fran T; Rehman, Najibah; Gress, Ronald E; Telford, William G

    2009-05-15

    Telomere length analysis has been greatly simplified by the quantitative flow cytometry technique FISH-flow. In this method, a fluorescein-labeled synthetic oligonucleotide complementary to the telomere terminal repeat sequence is hybridized to the telomere sequence and the resulting fluorescence measured by flow cytometry. This technique has supplanted the traditional laborious Southern blot telomere length measurement techniques in many laboratories, and allows single cell analysis of telomere length in high-throughput sample formats. Nevertheless, the harsh conditions required for telomere probe annealing (82 degrees C) has made it difficult to successfully combine this technique with simultaneous immunolabeling. Most traditional organic fluorescent probes (i.e. fluorescein, phycoerythrin, etc.) have limited thermal stability and do not survive the high temperature annealing process, despite efforts to covalently crosslink the antigen-antibody-fluorophore complex. This loss of probe fluorescence has made it difficult to measure FISH-flow in complex lymphocyte populations, and has generally forced investigators to use fluorescent-activated cell sorting to pre-separate their populations, a laborious technique that requires prohibitively large numbers of cells. In this study, we have substituted quantum dots (nanoparticles) for traditional fluorophores in FISH-flow. Quantum dots were demonstrated to possess much greater thermal stability than traditional low molecular weight and phycobiliprotein fluorophores. Quantum dot antibody conjugates directed against monocyte and T cell antigens were found to retain most of their fluorescence following the high temperature annealing step, allowing simultaneous fluorescent immunophenotyping and telomere length measurement. Since quantum dots have very narrow emission bandwidths, we were able to analyze multiple quantum dot antibody conjugates (Qdot 605, 655 and 705) simultaneously with FISH-flow measurement to assess the age

  8. [Telomere length and telomerase activity in hepatocellular carcinoma].

    Nakashio, R; Kitamoto, M; Nakanishi, T; Takaishi, H; Takahashi, S; Kajiyama, G

    1998-05-01

    Telomerase activity and terminal restriction fragment (TRF) length were examined in hepatocellular carcinoma (HCC). Telomerase activity was assayed by telomeric repeat amplification protocol (TRAP) connected with an internal telomerase assay standard (ITAS). The incidence of strong telomerase activity (highly variable level compared with the activity of non-cancerous liver tissue) was 79% in well, 84% in moderately, and 100% in poorly differentiated HCC, while 0% in non-cancerous liver tissues. The incidence of TRF length alteration (reduction or elongation) was 53% in HCC. The incidence of TRF alteration was significantly higher in HCC exceeding 3 cm in diameter, moderately or poorly differentiated in histology. Telomerase activity was not associated with TRF length alteration in HCC. In conclusion, strong telomerase activity and TRF length alteration increased with HCC tumor progressions. PMID:9613130

  9. Five dysfunctional telomeres predict onset of senescence in human cells

    Kaul, Zeenia; Cesare, Anthony J.; Huschtscha, Lily I.; Neumann, Axel A.; Reddel, Roger R

    2011-01-01

    Replicative senescence is accompanied by a telomere-specific DNA damage response (DDR). We found that DDR+ telomeres occur spontaneously in early-passage normal human cells and increase in number with increasing cumulative cell divisions. DDR+ telomeres at replicative senescence retain TRF2 and RAP1 proteins, are not associated with end-to-end fusions and mostly result from strand-independent, postreplicative dysfunction. On the basis of the calculated number of DDR+ telomeres in G1-phase cel...

  10. Telomere reprogramming and maintenance in porcine iPS cells.

    Guangzhen Ji

    Full Text Available Telomere reprogramming and silencing of exogenous genes have been demonstrated in mouse and human induced pluripotent stem cells (iPS cells. Pigs have the potential to provide xenotransplant for humans, and to model and test human diseases. We investigated the telomere length and maintenance in porcine iPS cells generated and cultured under various conditions. Telomere lengths vary among different porcine iPS cell lines, some with telomere elongation and maintenance, and others telomere shortening. Porcine iPS cells with sufficient telomere length maintenance show the ability to differentiate in vivo by teratoma formation test. IPS cells with short or dysfunctional telomeres exhibit reduced ability to form teratomas. Moreover, insufficient telomerase and incomplete telomere reprogramming and/or maintenance link to sustained activation of exogenous genes in porcine iPS cells. In contrast, porcine iPS cells with reduced expression of exogenous genes or partial exogene silencing exhibit insufficient activation of endogenous pluripotent genes and telomerase genes, accompanied by telomere shortening with increasing passages. Moreover, telomere doublets, telomere sister chromatid exchanges and t-circles that presumably are involved in telomere lengthening by recombination also are found in porcine iPS cells. These data suggest that both telomerase-dependent and telomerase-independent mechanisms are involved in telomere reprogramming during induction and passages of porcine iPS cells, but these are insufficient, resulting in increased telomere damage and shortening, and chromosomal instability. Active exogenes might compensate for insufficient activation of endogenous genes and incomplete telomere reprogramming and maintenance of porcine iPS cells. Further understanding of telomere reprogramming and maintenance may help improve the quality of porcine iPS cells.