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Sample records for telomeric protein htrf1

  1. A C-terminal Myb extension domain defines a novel family of double-strand telomeric DNA-binding proteins in Arabidopsis.

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    Karamysheva, Zemfira N; Surovtseva, Yulia V; Vespa, Laurent; Shakirov, Eugene V; Shippen, Dorothy E

    2004-11-12

    Little is known about the protein composition of plant telomeres. We queried the Arabidopsis thaliana genome data base in search of genes with similarity to the human telomere proteins hTRF1 and hTRF2. hTRF1/hTRF2 are distinguished by the presence of a single Myb-like domain in their C terminus that is required for telomeric DNA binding in vitro. Twelve Arabidopsis genes fitting this criterion, dubbed TRF-like (TRFL), fell into two distinct gene families. Notably, TRFL family 1 possessed a highly conserved region C-terminal to the Myb domain called Myb-extension (Myb-ext) that is absent in TRFL family 2 and hTRF1/hTRF2. Immunoprecipitation experiments revealed that recombinant proteins from TRFL family 1, but not those from family 2, formed homodimers and heterodimers in vitro. DNA binding studies with isolated C-terminal fragments from TRFL family 1 proteins, but not family 2, showed specific binding to double-stranded plant telomeric DNA in vitro. Removal of the Myb-ext domain from TRFL1, a family 1 member, abolished DNA binding. However, when the Myb-ext domain was introduced into the corresponding region in TRFL3, a family 2 member, telomeric DNA binding was observed. Thus, Myb-ext is required for binding plant telomeric DNA and defines a novel class of proteins in Arabidopsis.

  2. Dynamics of protein binding to telomeres in living cells: implications for telomere structure and function.

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    K.A. Mattern (Karin); S.J. Swiggers (Susan); A.L. Nigg (Alex); B. Löwenberg (Bob); A.B. Houtsmuller (Adriaan); J.M. Zijlmans (Mark)

    2004-01-01

    textabstractTelomeric proteins have an essential role in the regulation of the length of the telomeric DNA tract and in protection against end-to-end chromosome fusion. Telomere organization and how individual proteins are involved in different telomere functions in living cells is

  3. Telomere-binding proteins of Arabidopsis thaliana.

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    Zentgraf, U

    1995-02-01

    The nucleoprotein structure of Arabidopsis thaliana telomeres was investigated. A protein specifically binding to telomeric sequences was characterized by gel mobility shift assays with synthetic oligonucleotides consisting of four 7 bp telomeric repeats of Arabidopsis (TTTAGGG) and crude nuclear protein extracts of Arabidopsis leaves. These DNA-protein binding studies revealed that the binding affinity of this telomere-binding protein to the G-rich single-strand as well as to the double-stranded telomeric DNA is much higher than to the C-rich single-strand. The molecular mass of the protein was identified by SDS-PAGE to be 67 kDa. The isoelectric points were determined to be 5.0, 4.85 and 4.7, respectively, indicating that either one protein with different modifications or three slightly different proteins have been isolated. An RNA component, possibly serving as a template for reverse transcription of a plant telomerase, does not mediate the DNA-protein contact because the DNA-protein interactions were not RNAse-sensitive.

  4. Solution structure of the Arabidopsis thaliana telomeric repeat-binding protein DNA binding domain: a new fold with an additional C-terminal helix.

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    Sue, Shih-Che; Hsiao, Hsin-Hao; Chung, Ben C-P; Cheng, Ying-Hsien; Hsueh, Kuang-Lung; Chen, Chung Mong; Ho, Chia Hsing; Huang, Tai-Huang

    2006-02-10

    The double-stranded telomeric repeat-binding protein (TRP) AtTRP1 is isolated from Arabidopsis thaliana. Using gel retardation assays, we defined the C-terminal 97 amino acid residues, Gln464 to Val560 (AtTRP1(464-560)), as the minimal structured telomeric repeat-binding domain. This region contains a typical Myb DNA-binding motif and a C-terminal extension of 40 amino acid residues. The monomeric AtTRP1(464-560) binds to a 13-mer DNA duplex containing a single repeat of an A.thaliana telomeric DNA sequence (GGTTTAG) in a 1:1 complex, with a K(D) approximately 10(-6)-10(-7) M. Nuclear magnetic resonance (NMR) examination revealed that the solution structure of AtTRP1(464-560) is a novel four-helix tetrahedron rather than the three-helix bundle structure found in typical Myb motifs and other TRPs. Binding of the 13-mer DNA duplex to AtTRP1(464-560) induced significant chemical shift perturbations of protein amide resonances, which suggests that helix 3 (H3) and the flexible loop connecting H3 and H4 are essential for telomeric DNA sequence recognition. Furthermore, similar to that in hTRF1, the N-terminal arm likely contributes to or stabilizes DNA binding. Sequence comparisons suggested that the four-helix structure and the involvement of the loop residues in DNA binding may be features unique to plant TRPs.

  5. The Drosophila HOAP protein is required for telomere capping.

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    Cenci, Giovanni; Siriaco, Giorgia; Raffa, Grazia D; Kellum, Rebecca; Gatti, Maurizio

    2003-01-01

    HOAP (HP1/ORC-associated protein) has recently been isolated from Drosophila melanogaster embryos as part of a cytoplasmic complex that contains heterochromatin protein 1 (HP1) and the origin recognition complex subunit 2 (ORC2). Here, we show that caravaggio, a mutation in the HOAP-encoding gene, causes extensive telomere-telomere fusions in larval brain cells, indicating that HOAP is required for telomere capping. Our analyses indicate that HOAP is specifically enriched at mitotic chromosome telomeres, and strongly suggest that HP1 and HOAP form a telomere-capping complex that does not contain ORC2.

  6. Telomere Capping Proteins are Structurally Related to RPA with an additional Telomere-Specific Domain

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    Gelinas, A.; Paschini, M; Reyes, F; Heroux, A; Batey, R; Lundblad, V; Wuttke, D

    2009-01-01

    Telomeres must be capped to preserve chromosomal stability. The conserved Stn1 and Ten1 proteins are required for proper capping of the telomere, although the mechanistic details of how they contribute to telomere maintenance are unclear. Here, we report the crystal structures of the C-terminal domain of the Saccharomyces cerevisiae Stn1 and the Schizosaccharomyces pombe Ten1 proteins. These structures reveal striking similarities to corresponding subunits in the replication protein A complex, further supporting an evolutionary link between telomere maintenance proteins and DNA repair complexes. Our structural and in vivo data of Stn1 identify a new domain that has evolved to support a telomere-specific role in chromosome maintenance. These findings endorse a model of an evolutionarily conserved mechanism of DNA maintenance that has developed as a result of increased chromosomal structural complexity.

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

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    Miłosz Wieczór

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

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

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

    2017-11-13

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

  9. Telomeric protein TRF2 protects Holliday junctions with telomeric arms from displacement by the Werner syndrome helicase.

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    Nora, Gerald J; Buncher, Noah A; Opresko, Patricia L

    2010-07-01

    WRN protein loss causes Werner syndrome (WS), which is characterized by premature aging as well as genomic and telomeric instability. WRN prevents telomere loss, but the telomeric protein complex must regulate WRN activities to prevent aberrant telomere processing. Telomere-binding TRF2 protein inhibits telomere t-loop deletion by blocking Holliday junction (HJ) resolvase cleavage activity, but whether TRF2 also modulates HJ displacement at t-loops is unknown. In this study, we used multiplex fluorophore imaging to track the fate of individual strands of HJ substrates. We report the novel finding that TRF2 inhibits WRN helicase strand displacement of HJs with telomeric repeats in duplex arms, but unwinding of HJs with a telomeric center or lacking telomeric sequence is unaffected. These data, together with results using TRF2 fragments and TRF2 HJ binding assays, indicate that both the TRF2 B- and Myb domains are required to inhibit WRN HJ activity. We propose a novel model whereby simultaneous binding of the TRF2 B-domain to the HJ core and the Myb domain to telomeric arms promote and stabilize HJs in a stacked arm conformation that is unfavorable for unwinding. Our biochemical study provides a mechanistic basis for the cellular findings that TRF2 regulates WRN activity at telomeres.

  10. Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins.

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    Sepsiova, Regina; Necasova, Ivona; Willcox, Smaranda; Prochazkova, Katarina; Gorilak, Peter; Nosek, Jozef; Hofr, Ctirad; Griffith, Jack D; Tomaska, Lubomir

    2016-01-01

    Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast.

  11. Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins.

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    Regina Sepsiova

    Full Text Available Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs. Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast.

  12. The telomere binding protein TRF2 induces chromatin compaction.

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    Baker, Asmaa M; Fu, Qiang; Hayward, William; Victoria, Samuel; Pedroso, Ilene M; Lindsay, Stuart M; Fletcher, Terace M

    2011-04-19

    Mammalian telomeres are specialized chromatin structures that require the telomere binding protein, TRF2, for maintaining chromosome stability. In addition to its ability to modulate DNA repair activities, TRF2 also has direct effects on DNA structure and topology. Given that mammalian telomeric chromatin includes nucleosomes, we investigated the effect of this protein on chromatin structure. TRF2 bound to reconstituted telomeric nucleosomal fibers through both its basic N-terminus and its C-terminal DNA binding domain. Analytical agarose gel electrophoresis (AAGE) studies showed that TRF2 promoted the folding of nucleosomal arrays into more compact structures by neutralizing negative surface charge. A construct containing the N-terminal and TRFH domains together altered the charge and radius of nucleosomal arrays similarly to full-length TRF2 suggesting that TRF2-driven changes in global chromatin structure were largely due to these regions. However, the most compact chromatin structures were induced by the isolated basic N-terminal region, as judged by both AAGE and atomic force microscopy. Although the N-terminal region condensed nucleosomal array fibers, the TRFH domain, known to alter DNA topology, was required for stimulation of a strand invasion-like reaction with nucleosomal arrays. Optimal strand invasion also required the C-terminal DNA binding domain. Furthermore, the reaction was not stimulated on linear histone-free DNA. Our data suggest that nucleosomal chromatin has the ability to facilitate this activity of TRF2 which is thought to be involved in stabilizing looped telomere structures.

  13. Mouse CCDC79 (TERB1) is a meiosis-specific telomere associated protein.

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    Daniel, Katrin; Tränkner, Daniel; Wojtasz, Lukasz; Shibuya, Hiroki; Watanabe, Yoshinori; Alsheimer, Manfred; Tóth, Attila

    2014-05-22

    Telomeres have crucial meiosis-specific roles in the orderly reduction of chromosome numbers and in ensuring the integrity of the genome during meiosis. One such role is the attachment of telomeres to trans-nuclear envelope protein complexes that connect telomeres to motor proteins in the cytoplasm. These trans-nuclear envelope connections between telomeres and cytoplasmic motor proteins permit the active movement of telomeres and chromosomes during the first meiotic prophase. Movements of chromosomes/telomeres facilitate the meiotic recombination process, and allow high fidelity pairing of homologous chromosomes. Pairing of homologous chromosomes is a prerequisite for their correct segregation during the first meiotic division. Although inner-nuclear envelope proteins, such as SUN1 and potentially SUN2, are known to bind and recruit meiotic telomeres, these proteins are not meiosis-specific, therefore cannot solely account for telomere-nuclear envelope attachment and/or for other meiosis-specific characteristics of telomeres in mammals. We identify CCDC79, alternatively named TERB1, as a meiosis-specific protein that localizes to telomeres from leptotene to diplotene stages of the first meiotic prophase. CCDC79 and SUN1 associate with telomeres almost concurrently at the onset of prophase, indicating a possible role for CCDC79 in telomere-nuclear envelope interactions and/or telomere movements. Consistent with this scenario, CCDC79 is missing from most telomeres that fail to connect to SUN1 protein in spermatocytes lacking the meiosis-specific cohesin SMC1B. SMC1B-deficient spermatocytes display both reduced efficiency in telomere-nuclear envelope attachment and reduced stability of telomeres specifically during meiotic prophase. Importantly, CCDC79 associates with telomeres in SUN1-deficient spermatocytes, which strongly indicates that localization of CCDC79 to telomeres does not require telomere-nuclear envelope attachment. CCDC79 is a meiosis-specific telomere

  14. Cockayne Syndrome group B protein interacts with TRF2 and regulates telomere length and stability.

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    Batenburg, Nicole L; Mitchell, Taylor R H; Leach, Derrik M; Rainbow, Andrew J; Zhu, Xu-Dong

    2012-10-01

    The majority of Cockayne syndrome (CS) patients carry a mutation in Cockayne Syndrome group B (CSB), a large nuclear protein implicated in DNA repair, transcription and chromatin remodeling. However, whether CSB may play a role in telomere metabolism has not yet been characterized. Here, we report that CSB physically interacts with TRF2, a duplex telomeric DNA binding protein essential for telomere protection. We find that CSB localizes at a small subset of human telomeres and that it is required for preventing the formation of telomere dysfunction-induced foci (TIF) in CS cells. We find that CS cells or CSB knockdown cells accumulate telomere doublets, the suppression of which requires CSB. We find that overexpression of CSB in CS cells promotes telomerase-dependent telomere lengthening, a phenotype that is associated with a decrease in the amount of telomere-bound TRF1, a negative mediator of telomere length maintenance. Furthermore, we show that CS cells or CSB knockdown cells exhibit misregulation of TERRA, a large non-coding telomere repeat-containing RNA important for telomere maintenance. Taken together, these results suggest that CSB is required for maintaining the homeostatic level of TERRA, telomere length and integrity. These results further imply that CS patients carrying CSB mutations may be defective in telomere maintenance.

  15. The telomere binding protein TRF2 induces chromatin compaction.

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    Asmaa M Baker

    2011-04-01

    Full Text Available Mammalian telomeres are specialized chromatin structures that require the telomere binding protein, TRF2, for maintaining chromosome stability. In addition to its ability to modulate DNA repair activities, TRF2 also has direct effects on DNA structure and topology. Given that mammalian telomeric chromatin includes nucleosomes, we investigated the effect of this protein on chromatin structure. TRF2 bound to reconstituted telomeric nucleosomal fibers through both its basic N-terminus and its C-terminal DNA binding domain. Analytical agarose gel electrophoresis (AAGE studies showed that TRF2 promoted the folding of nucleosomal arrays into more compact structures by neutralizing negative surface charge. A construct containing the N-terminal and TRFH domains together altered the charge and radius of nucleosomal arrays similarly to full-length TRF2 suggesting that TRF2-driven changes in global chromatin structure were largely due to these regions. However, the most compact chromatin structures were induced by the isolated basic N-terminal region, as judged by both AAGE and atomic force microscopy. Although the N-terminal region condensed nucleosomal array fibers, the TRFH domain, known to alter DNA topology, was required for stimulation of a strand invasion-like reaction with nucleosomal arrays. Optimal strand invasion also required the C-terminal DNA binding domain. Furthermore, the reaction was not stimulated on linear histone-free DNA. Our data suggest that nucleosomal chromatin has the ability to facilitate this activity of TRF2 which is thought to be involved in stabilizing looped telomere structures.

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

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    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.

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

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    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.

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

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    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.

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

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    Ikumi Fujita

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

  20. The fission yeast heterochromatin protein Rik1 is required for telomere clustering during meiosis

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    Tuzon, Creighton T; Borgstrøm, Britta; Weilguny, Dietmar

    2004-01-01

    Telomeres share the ability to silence nearby transcription with heterochromatin, but the requirement of heterochromatin proteins for most telomere functions is unknown. The fission yeast Rik1 protein is required for heterochromatin formation at centromeres and the mating-type locus, as it recrui...... meiosis. However, Rik1 is dispensable for the protective roles of telomeres in preventing chromosome end-fusion. Thus, a Swi6-independent heterochromatin function distinct from that at centromeres and the mating-type locus operates at telomeres during sexual differentiation....

  1. Zebrafish as a model system to study the physiological function of telomeric protein TPP1.

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    Yiying Xie

    Full Text Available Telomeres are specialized chromatin structures at the end of chromosomes. Telomere dysfunction can lead to chromosomal abnormalities, DNA damage responses, and even cancer. In mammalian cells, a six-protein complex (telosome/shelterin is assembled on the telomeres through the interactions between various domain structures of the six telomere proteins (POT1, TPP1, TIN2, TRF1, TRF2 and RAP1, and functions in telomere maintenance and protection. Within the telosome, TPP1 interacts directly with POT1 and TIN2 and help to mediate telosome assembly. Mechanisms of telomere regulation have been extensively studied in a variety of model organisms. For example, the physiological roles of telomere-targeted proteins have been assessed in mice through homozygous inactivation. In these cases, early embryonic lethality has prevented further studies of these proteins in embryogenesis and development. As a model system, zebrafish offers unique advantages such as genetic similarities with human, rapid developmental cycles, and ease of manipulation of its embryos. In this report, we detailed the identification of zebrafish homologues of TPP1, POT1, and TIN2, and showed that the domain structures and interactions of these telosome components appeared intact in zebrafish. Importantly, knocking down TPP1 led to multiple abnormalities in zebrafish embryogenesis, including neural death, heart malformation, and caudal defect. And these embryos displayed extensive apoptosis. These results underline the importance of TPP1 in zebrafish embryogenesis, and highlight the feasibility and advantages of investigating the signaling pathways and physiological function of telomere proteins in zebrafish.

  2. Telomere- and Telomerase-Associated Proteins and Their Functions in the Plant Cell

    Czech Academy of Sciences Publication Activity Database

    Schrumpfová, P.; Schorová, Š.; Fajkus, Jiří

    2016-01-01

    Roč. 7, č. 851 (2016) ISSN 1664-462X R&D Projects: GA ČR(CZ) GA13-06943S Institutional support: RVO:68081707 Keywords : telomere * telomerase * telomeric proteins Subject RIV: BO - Biophysics Impact factor: 4.298, year: 2016

  3. Brh2 and Rad51 promote telomere maintenance in Ustilago maydis, a new model system of DNA repair proteins at telomeres.

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    Yu, Eun Young; Kojic, Milorad; Holloman, William K; Lue, Neal F

    2013-07-01

    Recent studies implicate a number of DNA repair proteins in mammalian telomere maintenance. However, because several key repair proteins in mammals are missing from the well-studied budding and fission yeast, their roles at telomeres cannot be modeled in standard fungi. In this report, we explored the dimorphic fungus Ustilago maydis as an alternative model for telomere research. This fungus, which belongs to the phylum Basidiomycota, has a telomere repeat unit that is identical to the mammalian repeat, as well as a constellation of DNA repair proteins that more closely mimic the mammalian collection. We showed that the two core components of homology-directed repair (HDR) in U. maydis, namely Brh2 and Rad51, both promote telomere maintenance in telomerase positive cells, just like in mammals. In addition, we found that Brh2 is localized to telomeres in vivo, suggesting that it acts directly at chromosome ends. We surveyed a series of mutants with DNA repair defects, and found many of them to have short telomeres. Our results indicate that factors involved in DNA repair are probably also needed for optimal telomere maintenance in U. maydis, and that this fungus is a useful alternative model system for telomere research. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. TRF2 functions as a protein hub and regulates telomere maintenance by recognizing specific peptide motifs.

    Science.gov (United States)

    Kim, Hyeung; Lee, Ok-Hee; Xin, Huawei; Chen, Liuh-Yow; Qin, Jun; Chae, Heekyung Kate; Lin, Shiaw-Yih; Safari, Amin; Liu, Dan; Songyang, Zhou

    2009-04-01

    In mammalian cells, the telomeric repeat binding factor (TRF) homology (TRFH) domain-containing telomeric proteins TRF1 and TRF2 associate with a collection of molecules necessary for telomere maintenance and cell-cycle progression. However, the specificity and the mechanisms by which TRF2 communicates with different signaling pathways remain largely unknown. Using oriented peptide libraries, we demonstrate that the TRFH domain of human TRF2 recognizes [Y/F]XL peptides with the consensus motif YYHKYRLSPL. Disrupting the interactions between the TRF2 TRFH domain and its targets resulted in telomeric DNA-damage responses. Furthermore, our genome-wide target analysis revealed phosphatase nuclear targeting subunit (PNUTS) and microcephalin 1 (MCPH1) as previously unreported telomere-associated proteins that directly interact with TRF2 via the [Y/F]XL motif. PNUTS and MCPH1 can regulate telomere length and the telomeric DNA-damage response, respectively. Our findings indicate that an array of TRF2 molecules functions as a protein hub and regulates telomeres by recruiting different signaling molecules via a linear sequence code.

  5. Characterization of two Arabidopsis thaliana myb-like proteins showing affinity to telomeric DNA sequence.

    Science.gov (United States)

    Schrumpfová, Petra; Kuchar, Milan; Miková, Gabriela; Skrísovská, Lenka; Kubicárová, Tatiana; Fajkus, Jirí

    2004-04-01

    Telomere-binding proteins participate in forming a functional nucleoprotein structure at chromosome ends. Using a genomic approach, two Arabidopsis thaliana genes coding for candidate Myb-like telomere binding proteins were cloned and expressed in E. coli. Both proteins, termed AtTBP2 (accession Nos. T46051 (protein database) and GI:638639 (nucleotide database); 295 amino acids, 32 kDa, pI 9.53) and AtTBP3 (BAB08466, GI:9757879; 299 amino acids, 33 kDa, pI 9.88), contain a single Myb-like DNA-binding domain at the N-terminus, and a histone H1/H5-like DNA-binding domain in the middle of the protein sequence. Both proteins are expressed in various A. thaliana tissues. Using the two-hybrid system interaction between the proteins AtTBP2 and AtTBP3 and self interactions of each of the proteins were detected. Gel-retardation assays revealed that each of the two proteins is able to bind the G-rich strand and double-stranded DNA of plant telomeric sequence with an affinity proportional to a number of telomeric repeats. Substrates bearing a non-telomeric DNA sequence positioned between two telomeric repeats were bound with an efficiency depending on the length of interrupting sequence. The ability to bind variant telomere sequences decreased with sequence divergence from the A. thaliana telomeric DNA. None of the proteins alone or their mixture affects telomerase activity in vitro. Correspondingly, no interaction was observed between any of two proteins and the Arabidopsis telomerase reverse transcriptase catalytic subunit TERT (accession No. AF172097) using two-hybrid assay.

  6. CRISPR-Cas9 Mediated Telomere Removal Leads to Mitochondrial Stress and Protein Aggregation

    Directory of Open Access Journals (Sweden)

    Hyojung Kim

    2017-10-01

    Full Text Available Aging is considered the major risk factor for neurodegenerative diseases including Parkinson’s disease (PD. Telomere shortening is associated with cellular senescence. In this regard, pharmacological or genetic inhibition of telomerase activity has been used to model cellular aging. Here, we employed CRISPR-Cas9 technology to instantly remove the telomere to induce aging in a neuroblastoma cell line. Expression of both Cas9 and guide RNA targeting telomere repeats ablated the telomere, leading to retardation of cell proliferation. Instant deletion of telomere in SH-SY5Y cells impaired mitochondrial function with diminished mitochondrial respiration and cell viability. Supporting the pathological relevance of cell aging by CRISPR-Cas9 mediated telomere removal, alterations were observed in the levels of PD-associated proteins including PTEN-induced putative kinase 1, peroxisome proliferator-activated receptor γ coactivator 1-α, nuclear respiratory factor 1, parkin, and aminoacyl tRNA synthetase complex interacting multifunctional protein 2. Significantly, α-synuclein expression in the background of telomere removal led to the enhancement of protein aggregation, suggesting positive feed-forward interaction between aging and PD pathogenesis. Collectively, our results demonstrate that CRISPR-Cas9 can be used to efficiently model cellular aging and PD.

  7. CRISPR-Cas9 Mediated Telomere Removal Leads to Mitochondrial Stress and Protein Aggregation.

    Science.gov (United States)

    Kim, Hyojung; Ham, Sangwoo; Jo, Minkyung; Lee, Gum Hwa; Lee, Yun-Song; Shin, Joo-Ho; Lee, Yunjong

    2017-10-03

    Aging is considered the major risk factor for neurodegenerative diseases including Parkinson's disease (PD). Telomere shortening is associated with cellular senescence. In this regard, pharmacological or genetic inhibition of telomerase activity has been used to model cellular aging. Here, we employed CRISPR-Cas9 technology to instantly remove the telomere to induce aging in a neuroblastoma cell line. Expression of both Cas9 and guide RNA targeting telomere repeats ablated the telomere, leading to retardation of cell proliferation. Instant deletion of telomere in SH-SY5Y cells impaired mitochondrial function with diminished mitochondrial respiration and cell viability. Supporting the pathological relevance of cell aging by CRISPR-Cas9 mediated telomere removal, alterations were observed in the levels of PD-associated proteins including PTEN-induced putative kinase 1, peroxisome proliferator-activated receptor γ coactivator 1-α, nuclear respiratory factor 1, parkin, and aminoacyl tRNA synthetase complex interacting multifunctional protein 2. Significantly, α-synuclein expression in the background of telomere removal led to the enhancement of protein aggregation, suggesting positive feed-forward interaction between aging and PD pathogenesis. Collectively, our results demonstrate that CRISPR-Cas9 can be used to efficiently model cellular aging and PD.

  8. Yeast hnRNP-related proteins contribute to the maintenance of telomeres

    Energy Technology Data Exchange (ETDEWEB)

    Lee-Soety, Julia Y., E-mail: jlee04@sju.edu [Department of Biology, Saint Joseph' s University, PA 19131 (United States); Jones, Jennifer; MacGibeny, Margaret A.; Remaly, Erin C.; Daniels, Lynsey; Ito, Andrea; Jean, Jessica; Radecki, Hannah; Spencer, Shannon [Department of Biology, Saint Joseph' s University, PA 19131 (United States)

    2012-09-14

    Highlights: Black-Right-Pointing-Pointer Yeast hnRNP-related proteins are able to prevent faster senescence in telomerase-null cells. Black-Right-Pointing-Pointer The conserved RRMs in Npl3 are important for telomere maintenance. Black-Right-Pointing-Pointer Human hnRNP A1 is unable to complement the lack of NPL3 in yeast. Black-Right-Pointing-Pointer Npl3 and Cbc2 may work as telomere capping proteins. -- Abstract: Telomeres protect the ends of linear chromosomes, which if eroded to a critical length can become uncapped and lead to replicative senescence. Telomerase maintains telomere length in some cells, but inappropriate expression facilitates the immortality of cancer cells. Recently, proteins involved in RNA processing and ribosome assembly, such as hnRNP (heterogeneous nuclear ribonucleoprotein) A1, have been found to participate in telomere maintenance in mammals. The Saccharomyces cerevisiae protein Npl3 shares significant amino acid sequence similarities with hnRNP A1. We found that deleting NPL3 accelerated the senescence of telomerase null cells. The highly conserved RNA recognition motifs (RRM) in Npl3 appear to be important for preventing faster senescence. Npl3 preferentially binds telomere sequences in vitro, suggesting that Npl3 may affect telomeres directly. Despite similarities between the two proteins, human hnRNP A1 is unable to complement the lack of Npl3 to rescue accelerated senescence in tlc1 npl3 cells. Deletion of CBC2, which encodes another hnRNP-related protein that associates with Npl3, also accelerates senescence. Potential mechanisms by which hnRNP-related proteins maintain telomeres are discussed.

  9. Using centromere mediated genome elimination to elucidate the functional redundancy of candidate telomere binding proteins in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Karel eRiha

    2016-01-01

    Full Text Available Proteins that bind to telomeric DNA form the key structural and functional constituents of telomeres. While telomere binding proteins have been described in the majority of organisms, their identity in plants remains unknown. Several protein families containing a telomere binding motif known as the telobox have been previously described in Arabidopsis thaliana. Nonetheless, functional evidence for their involvement at telomeres has not been obtained, likely due to functional redundancy. Here we performed genetic analysis on the TRF-like family consisting of six proteins (TRB1, TRP1, TRFL1, TRFL2, TRFL4 and TRF9 which have previously shown to bind telomeric DNA in vitro. We used haploid genetics to create multiple knock-out plants deficient for all six proteins of this gene family. These plants did not exhibit changes in telomere length, or phenotypes associated with telomere dysfunction. This data demonstrates that this telobox protein family is not involved in telomere maintenance in Arabidopsis. Phylogenetic analysis in major plant lineages revealed early diversification of telobox proteins families indicating that telomere function may be associated with other telobox proteins.

  10. Suppression of telomere-binding protein TPP1 resulted in telomere dysfunction and enhanced radiation sensitivity in telomerase-negative osteosarcoma cell line

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, Weiguang [Hubei Cancer Clinical Study Center, Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital, Wuhan University, Wuhan (China); Department of Oncology, The Third Affiliated Hospital, Soochow University, Changzhou (China); Wu, Qinqin [Hubei Cancer Clinical Study Center, Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital, Wuhan University, Wuhan (China); Department of Radiation Oncology, Changzhou Tumor Hospital, Soochow University, Changzhou (China); Zhou, Fuxiang; Xie, Conghua [Hubei Cancer Clinical Study Center, Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital, Wuhan University, Wuhan (China); Wu, Changping, E-mail: wcpzlk@163.com [Department of Oncology, The Third Affiliated Hospital, Soochow University, Changzhou (China); Zhou, Yunfeng, E-mail: yfzhouwhu@163.com [Hubei Cancer Clinical Study Center, Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital, Wuhan University, Wuhan (China)

    2014-03-07

    Highlights: • Down-regulation of TPP1 shortened telomere length in telomerase-negative cells. • Down-regulation of TPP1 induced cell apoptosis in telomerase-negative cells. • Down-regulation of TPP1 increased radiosensitivity in telomerase-negative cells. - Abstract: Mammalian telomeres are protected by the shelterin complex that contains the six core proteins POT1, TPP1, TIN2, TRF1, TRF2 and RAP1. TPP1, formerly known as TINT1, PTOP, and PIP1, is a key factor that regulates telomerase recruitment and activity. In addition to this, TPP1 is required to mediate the shelterin assembly and stabilize telomere. Previous work has found that TPP1 expression was elevated in radioresistant cells and that overexpression of TPP1 led to radioresistance and telomere lengthening in telomerase-positive cells. However, the exact effects and mechanism of TPP1 on radiosensitivity are yet to be precisely defined in the ALT cells. Here we report on the phenotypes of the conditional deletion of TPP1 from the human osteosarcoma U2OS cells using ALT pathway to extend the telomeres.TPP1 deletion resulted in telomere shortening, increased apoptosis and radiation sensitivity enhancement. Together, our findings show that TPP1 plays a vital role in telomere maintenance and protection and establish an intimate relationship between TPP1, telomere and cellular response to ionizing radiation, but likely has the specific mechanism yet to be defined.

  11. HYPOTHESIS: PARALOG FORMATION FROM PROGENITOR PROTEINS AND PARALOG MUTAGENESIS SPUR THE RAPID EVOLUTION OF TELOMERE BINDING PROTEINS

    Directory of Open Access Journals (Sweden)

    Arthur J Lustig

    2016-02-01

    Full Text Available Through elegant studies in fungal cells and complex organisms, we propose a unifying paradigm for the rapid evolution of telomere binding proteins (TBPs that associate with either (or both telomeric DNA and telomeric proteins. TBPs protect and regulate telomere structure and function. Four critical factors are involved. First, TBPs that commonly bind to telomeric DNA include the c-Myb binding proteins, OB-fold single-stranded binding proteins, and G-G base paired Hoogsteen structure (G4 binding proteins. Each contributes independently or, in some cases, cooperatively, to provide a minimum level of telomere function. As a result of these minimal requirements and the great abundance of homologs of these motifs in the proteome, DNA telomere-binding activity may be generated more easily than expected. Second, telomere dysfunction gives rise to genome instability, through the elevation of recombination rates, genome ploidy, and the frequency of gene mutations. The formation of paralogs that diverge from their progenitor proteins ultimately can form a high frequency of altered TBPs with altered functions. Third, TBPs that assemble into complexes (e.g. mammalian shelterin derive benefits from the novel emergent functions. Fourth, a limiting factor in the evolution of TBP complexes is the formation of mutually compatible interaction surfaces amongst the TBPs. These factors may have different degrees of importance in the evolution of different phyla, illustrated by the apparently simpler telomeres in complex plants. Selective pressures that can utilize the mechanisms of paralog formation and mutagenesis to drive TBP evolution along routes dependent on the requisite physiologic changes.

  12. DNA-PKcs-interacting protein KIP binding to TRF2 is required for the maintenance of functional telomeres.

    Science.gov (United States)

    Khadka, Prabhat; Lee, Ji Hoon; Baek, Seung Han; Oh, Sue Young; Chung, In Kwon

    2014-10-01

    Human telomeres associate with shelterin, a six-protein complex that protects chromosome ends from being recognized as sites of DNA damage. The shelterin subunit TRF2 (telomeric repeat-binding factor 2) protects telomeres by facilitating their organization into the protective capping structure. We have reported previously that the DNA-PKcs (DNA-dependent protein kinase catalytic subunit)-interacting protein KIP associates with telomerase through an interaction with hTERT (human telomerase reverse transcriptase). In the present study, we identify KIP as a novel interacting partner of TRF2. KIP is able to interact with both TRF2 and DNA-PKcs at telomeres. Because KIP is required for the association between TRF2 and DNA-PKcs, the interplay of these three proteins may provide a mechanism for the recruitment of DNA-PKcs to telomeres. We also show that KIP binding to TRF2 enhances the telomere-binding activity of TRF2, suggesting that KIP acts as a positive regulator of TRF2 function. Furthermore, depletion of KIP induces DNA-damage response foci at telomeres, thereby leading to induction of growth arrest, cellular senescence and altered cell cycle distribution. Collectively, our findings suggest that KIP, in addition to its association with catalytically active telomerase, plays important roles in the maintenance of functional telomeres and the regulation of telomere-associated DNA-damage response. Thus KIP represents a new pathway for modulating telomerase and telomere function in cancer.

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

    Science.gov (United States)

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

    2014-02-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Giannone, Richard J [ORNL; McDonald, W Hayes [ORNL; Hurst, Gregory {Greg} B [ORNL; Shen, Rong-Fong [National Institute on Aging, National Institutes of Health; Wang, Yisong [ORNL; Liu, Yie [National Institute on Aging, Baltimore

    2010-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Richard J Giannone

    2010-08-01

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

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

    Science.gov (United States)

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

    2014-07-01

    Werner syndrome (WS), caused by loss of function of the RecQ helicase WRN, is a hereditary disease characterized by premature aging and elevated cancer incidence. WRN has DNA binding, exonuclease, ATPase, helicase and strand annealing activities, suggesting possible roles in recombination-related processes. Evidence indicates that WRN deficiency causes telomeric abnormalities that likely underlie early onset of aging phenotypes in WS. Furthermore, TRF2, a protein essential for telomere protection, interacts with WRN and influences its basic helicase and exonuclease activities. However, these studies provided little insight into WRN's specific function at telomeres. Here, we explored the possibility that WRN and TRF2 cooperate during telomeric recombination processes. Our results indicate that TRF2, through its interactions with both WRN and telomeric DNA, stimulates WRN-mediated strand exchange specifically between telomeric substrates; TRF2's basic domain is particularly important for this stimulation. Although TRF1 binds telomeric DNA with similar affinity, it has minimal effects on WRN-mediated strand exchange of telomeric DNA. Moreover, TRF2 is displaced from telomeric DNA by WRN, independent of its ATPase and helicase activities. Together, these results suggest that TRF2 and WRN act coordinately during telomeric recombination processes, consistent with certain telomeric abnormalities associated with alteration of WRN function. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

  17. Increased Body Mass Index, Elevated C-reactive Protein, and Short Telomere Length

    DEFF Research Database (Denmark)

    Rode, Line; Nordestgaard, Børge G; Weischer, Maren

    2014-01-01

    -reactive protein. SETTING AND DESIGN: We studied 45,069 individuals from the Copenhagen General Population Study with measurements of leukocyte telomere length, BMI, and C-reactive protein in a Mendelian randomization study. Using the three obesity-associated polymorphisms FTO rs9939609, MC4R rs17782313, and TMEM...

  18. The telomeric protein TRF2 is critical for the protection of A549 cells from both telomere erosion and DNA double-strand breaks driven by salvicine.

    Science.gov (United States)

    Zhang, Yong-Wei; Zhang, Zhi-Xiang; Miao, Ze-Hong; Ding, Jian

    2008-03-01

    Telomere repeat binding factor 2 (TRF2) has been increasingly recognized to be involved in DNA damage response and telomere maintenance. Our previous report found that salvicine (SAL), a novel topoisomerase II poison, elicited DNA double-strand breaks and telomere erosion in separate experimental systems. However, it remains to be clarified whether they share a common response to these two events and in particular whether TRF2 is involved in this process. In this study, we found that SAL concurrently induced DNA double-strand breaks, telomeric DNA damage, and telomere erosion in lung carcinoma A549 cells. It was unexpected to find that SAL led to disruption of TRF2, independently of either its transcription or proteasome-mediated degradation. By overexpressing the full-length trf2 gene and transfecting TRF2 small interfering RNAs, we showed that TRF2 protein protected both telomeric and genomic DNA from the SAL-elicited events. It is noteworthy that although both the Ataxia-telangiectasia-mutated (ATM) and the ATM- and Rad3-related (ATR) kinases responded to the SAL-induced DNA damages, only ATR was essential for the telomere erosion. The study also showed that the activated ATR augmented the SAL-triggered TRF2 disruption, whereas TRF2 reduction in turn enhanced ATR function. All of these findings suggest the emerging significance of TRF2 protecting both telomeric DNA and genomic DNA on the one hand and reveal the mutual modulation between ATR and TRF2 in sensing DNA damage signaling during cancer development on the other hand.

  19. Alternative mechanisms of telomere lengthening: Permissive mutations, DNA repair proteins and tumorigenic progression

    Energy Technology Data Exchange (ETDEWEB)

    Gocha, April Renee Sandy; Harris, Julia [Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University College of Medicine, Columbus, OH 43210 (United States); Groden, Joanna, E-mail: joanna.groden@osumc.edu [Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University College of Medicine, Columbus, OH 43210 (United States)

    2013-03-15

    Highlights: ► Neoplastic cells maintain telomeres by telomerase or ALT. ► Genetic mutations in p53, ATRX, DAXX or H3F3A may activate ALT. ► Many DNA repair proteins are involved in ALT. ► Tumor progression is favored by telomerase expression. - Abstract: Telomeres protect chromosome termini to maintain genomic stability and regulate cellular lifespan. Maintenance of telomere length is required for neoplastic cells after the acquisition of mutations that deregulate cell cycle control and increase cellular proliferation, and can occur through expression of the enzyme telomerase or in a telomerase-independent manner termed alternative lengthening of telomeres (ALT). The precise mechanisms that govern the activation of ALT or telomerase in tumor cells are unknown, although cellular origin may favor one or the other mechanisms. ALT pathways are incompletely understood to date; however, recent publications have increasingly broadened our understanding of how ALT is activated, how it proceeds, and how it influences tumor growth. Specific mutational events influence ALT activation, as mutations in genes that suppress recombination and/or alterations in the regulation of telomerase expression are associated with ALT. Once engaged, ALT uses DNA repair proteins to maintain telomeres in the absence of telomerase; experiments that manipulate the expression of specific proteins in cells using ALT are illuminating some of its mechanisms. Furthermore, ALT may influence tumor growth, as experimental and clinical data suggest that telomerase expression may favor tumor progression. This review summarizes recent findings in mammalian cells and models, as well as clinical data, that identify the genetic mutations permissive to ALT, the DNA repair proteins involved in ALT mechanisms and the importance of telomere maintenance mechanisms for tumor progression. A comprehensive understanding of the mechanisms that permit tumor cell immortalization will be important for identifying

  20. MRT-2 checkpoint protein is required for germline immortality and telomere replication in C. elegans.

    Science.gov (United States)

    Ahmed, S; Hodgkin, J

    2000-01-13

    The germ line is an immortal cell lineage that is passed indefinitely from one generation to the next. To identify the genes that are required for germline immortality, we isolated Caenorhabditis elegans mutants with mortal germ lines--worms that can reproduce for several healthy generations but eventually become sterile. One of these mortal germline (mrt) mutants, mrt-2, exhibits progressive telomere shortening and accumulates end-to-end chromosome fusions in later generations, indicating that the MRT-2 protein is required for telomere replication. In addition, the germ line of mrt-2 is hypersensitive to X-rays and to transposon activity. Therefore, mrt-2 has defects in responding both to damaged DNA and to normal double-strand breaks present at telomeres. mrt-2 encodes a homologue of a checkpoint gene that is required to sense DNA damage in yeast. These results indicate that telomeres may be identified as a type of DNA damage and then repaired by the telomere-replication enzyme telomerase.

  1. Ku80 facilitates chromatin binding of the telomere binding protein, TRF2.

    Science.gov (United States)

    Fink, Lauren S; Lerner, Chad A; Torres, Paulina F; Sell, Christian

    2010-09-15

    The Ku70/80 heterodimer is central to non-homologous end joining repair of DNA double-strand breaks and the Ku80 gene appears to be essential for human but not rodent cell survival. The Ku70/80 heterodimer is located at telomeres but its precise function in telomere maintenance is not known. In order to examine the role of Ku80 beyond DNA repair in more detail, we have taken a knockdown approach using a human fibroblast strain. Following targeted Ku80 knockdown, telomere defects are observed and the steady state levels of the TRF2 protein are reduced. Inhibitor studies indicate that this loss of TRF2 is mediated by the proteasome and degradation of TRF2 following Ku depletion appears to involve a decrease in chromatin binding of TRF2, suggesting that the Ku heterodimer enhances TRF2 chromatin association and that non-chromatin bound TRF2 is targeted to the proteasome.

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

    Directory of Open Access Journals (Sweden)

    Ladislav eDokládal

    2015-11-01

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

  3. The Myb/SANT domain of the telomere-binding protein TRF2 alters chromatin structure.

    Science.gov (United States)

    Baker, Asmaa M; Fu, Qiang; Hayward, William; Lindsay, Stuart M; Fletcher, Terace M

    2009-08-01

    Eukaryotic DNA is packaged into chromatin, which regulates genome activities such as telomere maintenance. This study focuses on the interactions of a myb/SANT DNA-binding domain from the telomere-binding protein, TRF2, with reconstituted telomeric nucleosomal array fibers. Biophysical characteristics of the factor-bound nucleosomal arrays were determined by analytical agarose gel electrophoresis (AAGE) and single molecules were visualized by atomic force microscopy (AFM). The TRF2 DNA-binding domain (TRF2 DBD) neutralized more negative charge on the surface of nucleosomal arrays than histone-free DNA. Binding of TRF2 DBD at lower concentrations increased the radius and conformational flexibility, suggesting a distortion of the fiber structure. Additional loading of TRF2 DBD onto the nucleosomal arrays reduced the flexibility and strongly blocked access of micrococcal nuclease as contour lengths shortened, consistent with formation of a unique, more compact higher-order structure. Mirroring the structural results, TRF2 DBD stimulated a strand invasion-like reaction, associated with telomeric t-loops, at lower concentrations while inhibiting the reaction at higher concentrations. Full-length TRF2 was even more effective at stimulating this reaction. The TRF2 DBD had less effect on histone-free DNA structure and did not stimulate the t-loop reaction with this substrate, highlighting the influence of chromatin structure on the activities of DNA-binding proteins.

  4. Telomeres and human health

    DEFF Research Database (Denmark)

    Bojesen, S E

    2013-01-01

    Telomeres are the tips of chromosomes and consist of proteins and hexanucleotide tandem repeats of DNA. The DNA repeats are shortened at each mitotic division of normal cells, and the telomere length chronicles how many divisions the cell has undergone. Thus, telomere length is a marker of fundam...

  5. Molecular mechanism of DNA recognition by the alpha subunit of the Oxytricha telomere binding protein.

    Science.gov (United States)

    Laporte, L; Benevides, J M; Thomas, G J

    1999-01-12

    Interactions between telomeric DNA and the alpha subunit of the heterodimeric telomere binding protein of Oxytricha nova have been probed by Raman spectroscopy, CD spectroscopy, and nondenaturing gel electrophoresis. Telomeric sequences investigated include the Oxytricha 3' overhang, d(T4G4)2, and the related sequence dT6(T4G4)2, which incorporates a 5'-thymidylate leader. Corresponding nontelomeric isomers, d(TG)8 and dT6(TG)8, have also been investigated. Both d(T4G4)2 and dT6(T4G4)2 form stable hairpins that contain Hoogsteen G.G base pairs [Laporte, L., and Thomas, G. J., Jr. (1998) J. Mol. Biol. 281, 261-270]. The alpha subunit binds specifically and stoichiometrically to the dT6(T4G4)2 hairpin and alters its secondary structure by inducing conformational changes in the 5'-thymidylate leader without extensive disruption of G.G base pairing. Conversely, binding of the alpha subunit to d(T4G4)2 eliminates G.G pairing and unfolds the hairpin. DNA unfolding is accompanied by conformational changes affecting both the backbone and dG residues, as evidenced by Raman and CD spectra. Interestingly, the alpha subunit also forms complexes with the nontelomeric isomers, d(TG)8 and dT6(TG)8, evidenced by altered electrophoretic mobility in nondenaturing gels; however, Raman and CD spectra of complexes of the alpha subunit with nontelomeric DNA suggest no significant changes in backbone or deoxynucleoside conformations. Similarly, the alpha subunit binds to but does not appreciably alter the secondary structure of duplex DNA. The present results show that while the alpha subunit has the capacity to bind to Watson-Crick and different non-Watson-Crick motifs, DNA refolding is specific to the Oxytricha telomeric hairpin and the retention of G.G pairing is specific to the telomeric sequence incorporating the 5' leading sequence. A model is proposed for alpha subunit binding to telomeric DNA, and the physiological role of the alpha subunit in telomere organization is discussed.

  6. Identification of two human nuclear proteins that recognise the cytosine-rich strand of human telomeres in vitro

    Science.gov (United States)

    Lacroix, Laurent; Liénard, Hélène; Labourier, Emmanuel; Djavaheri-Mergny, Mojgan; Lacoste, Jérôme; Leffers, Henrik; Tazi, Jamal; Hélène, Claude; Mergny, Jean-Louis

    2000-01-01

    Most studies on the structure of DNA in telomeres have been dedicated to the double-stranded region or the guanosine-rich strand and consequently little is known about the factors that may bind to the telomere cytosine-rich (C-rich) strand. This led us to investigate whether proteins exist that can recognise C-rich sequences. We have isolated several nuclear factors from human cell extracts that specifically bind the C-rich strand of vertebrate telomeres [namely a d(CCCTAA)n repeat] with high affinity and bind double-stranded telomeric DNA with a 100× reduced affinity. A biochemical assay allowed us to characterise four proteins of apparent molecular weights 66–64, 45 and 35 kDa, respectively. To identify these polypeptides we screened a λgt11-based cDNA expression library, obtained from human HeLa cells using a radiolabelled telomeric oligonucleotide as a probe. Two clones were purified and sequenced: the first corresponded to the hnRNP K protein and the second to the ASF/SF2 splicing factor. Confirmation of the screening results was obtained with recombinant proteins, both of which bind to the human telomeric C-rich strand in vitro. PMID:10710423

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

    OpenAIRE

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

    2014-01-01

    Werner syndrome (WS), caused by loss of function of the RecQ helicase WRN, is a hereditary disease characterized by premature aging and elevated cancer incidence. WRN has DNA binding, exonuclease, ATPase, helicase and strand annealing activities, suggesting possible roles in recombination-related processes. Evidence indicates that WRN deficiency causes telomeric abnormalities that likely underlie early onset of aging phenotypes in WS. Furthermore, TRF2, a protein essential for telomere protec...

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

    NARCIS (Netherlands)

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

    2013-01-01

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

  9. Ndj1, a telomere-associated protein, regulates centrosome separation in budding yeast meiosis

    Science.gov (United States)

    Li, Ping; Shao, Yize; Jin, Hui

    2015-01-01

    Yeast centrosomes (called spindle pole bodies [SPBs]) remain cohesive for hours during meiotic G2 when recombination takes place. In contrast, SPBs separate within minutes after duplication in vegetative cells. We report here that Ndj1, a previously known meiosis-specific telomere-associated protein, is required for protecting SPB cohesion. Ndj1 localizes to the SPB but dissociates from it ∼16 min before SPB separation. Without Ndj1, meiotic SPBs lost cohesion prematurely, whereas overproduction of Ndj1 delayed SPB separation. When produced ectopically in vegetative cells, Ndj1 caused SPB separation defects and cell lethality. Localization of Ndj1 to the SPB depended on the SUN domain protein Mps3, and removal of the N terminus of Mps3 allowed SPB separation and suppressed the lethality of NDJ1-expressing vegetative cells. Finally, we show that Ndj1 forms oligomeric complexes with Mps3, and that the Polo-like kinase Cdc5 regulates Ndj1 protein stability and SPB separation. These findings reveal the underlying mechanism that coordinates yeast centrosome dynamics with meiotic telomere movement and cell cycle progression. PMID:25897084

  10. Telomeres: Hallmarks of radiosensitivity

    Energy Technology Data Exchange (ETDEWEB)

    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)

  11. HPV16 E7 protein and hTERT proteins defective for telomere maintenance cooperate to immortalize human keratinocytes.

    Directory of Open Access Journals (Sweden)

    Jonathan Miller

    Full Text Available Previous studies have shown that wild-type human telomerase reverse transcriptase (hTERT protein can functionally replace the human papillomavirus type 16 (HPV-16 E6 protein, which cooperates with the viral E7 protein in the immortalization of primary keratinocytes. In the current study, we made the surprising finding that catalytically inactive hTERT (hTERT-D868A, elongation-defective hTERT (hTERT-HA, and telomere recruitment-defective hTERT (hTERT N+T also cooperate with E7 in mediating bypass of the senescence blockade and effecting cell immortalization. This suggests that hTERT has activities independent of its telomere maintenance functions that mediate transit across this restriction point. Since hTERT has been shown to have a role in gene activation, we performed microarray studies and discovered that E6, hTERT and mutant hTERT proteins altered the expression of highly overlapping sets of cellular genes. Most important, the E6 and hTERT proteins induced mRNA and protein levels of Bmi1, the core subunit of the Polycomb Group (PcG complex 1. We show further that Bmi1 substitutes for E6 or hTERT in cell immortalization. Finally, tissue array studies demonstrated that expression of Bmi1 increased with the severity of cervical dysplasia, suggesting a potential role in the progression of cervical cancer. Together, these data demonstrate that hTERT has extra-telomeric activities that facilitate cell immortalization and that its induction of Bmi1 is one potential mechanism for mediating this activity.

  12. CRISPR-Cas9 Mediated Telomere Removal Leads to Mitochondrial Stress and Protein Aggregation

    OpenAIRE

    Kim, Hyojung; Ham, Sangwoo; Jo, Minkyung; Lee, Gum Hwa; Lee, Yun-Song; Shin, Joo-Ho; Lee, Yunjong

    2017-01-01

    Aging is considered the major risk factor for neurodegenerative diseases including Parkinson’s disease (PD). Telomere shortening is associated with cellular senescence. In this regard, pharmacological or genetic inhibition of telomerase activity has been used to model cellular aging. Here, we employed CRISPR-Cas9 technology to instantly remove the telomere to induce aging in a neuroblastoma cell line. Expression of both Cas9 and guide RNA targeting telomere repeats ablated the telomere, leadi...

  13. MERISTEM DISORGANIZATION1 encodes TEN1, an essential telomere protein that modulates telomerase processivity in Arabidopsis.

    Science.gov (United States)

    Leehy, Katherine A; Lee, Jung Ro; Song, Xiangyu; Renfrew, Kyle B; Shippen, Dorothy E

    2013-04-01

    Telomeres protect chromosome ends from being recognized as DNA damage, and they facilitate the complete replication of linear chromosomes. CST [for CTC1(Cdc13)/STN1/TEN1] is a trimeric chromosome end binding complex implicated in both aspects of telomere function. Here, we characterize TEN1 in the flowering plant Arabidopsis thaliana. We report that TEN1 (for telomeric pathways in association with Stn1, which stands for suppressor of cdc thirteen) is encoded by a previously characterized gene, MERISTEM DISORGANIZATION1 (MDO1). A point mutation in MDO1, mdo1-1/ten1-3 (G77E), triggers stem cell differentiation and death as well as a constitutive DNA damage response. We provide biochemical and genetic evidence that ten1-3 is likely to be a null mutation. As with ctc1 and stn1 null mutants, telomere tracts in ten1-3 are shorter and more heterogeneous than the wild type. Mutants also exhibit frequent telomere fusions, increased single-strand telomeric DNA, and telomeric circles. However, unlike stn1 or ctc1 mutants, telomerase enzyme activity is elevated in ten1-3 mutants due to an increase in repeat addition processivity. In addition, TEN1 is detected at a significantly smaller fraction of telomeres than CTC1. These data indicate that TEN1 is critical for telomere stability and also plays an unexpected role in modulating telomerase enzyme activity.

  14. Essential role for the TRF2 telomere protein in adult skin homeostasis.

    Science.gov (United States)

    Martínez, Paula; Ferrara-Romeo, Iole; Flores, Juana M; Blasco, Maria A

    2014-08-01

    TRF2 is a component of shelterin, the protein complex that protects the ends of mammalian chromosomes. TRF2 is essential for telomere capping owing to its roles in suppressing an ATM-dependent DNA damage response (DDR) at chromosome ends and inhibiting end-to-end chromosome fusions. Mice deficient for TRF2 are early embryonic lethal. However, the role of TRF2 in later stages of development and in the adult organism remains largely unaddressed, with the exception of liver, where TRF2 was found to be dispensable for maintaining tissue function. Here, we study the impact of TRF2 conditional deletion in stratified epithelia by generating the TRF2(∆/∆) -K5-Cre mouse model, which targets TRF2 deletion to the skin from embryonic day E11.5. In marked contrast to TRF2 deletion in the liver, TRF2(∆/∆) -K5-Cre mice show lethality in utero reaching 100% lethality perinataly. At the molecular and cellular level, TRF2 deletion provokes induction of an acute DDR at telomeres, leading to activation of p53 signaling pathways and to programed cell death since the time of Cre expression at E11.5. Unexpectedly, neither inhibition of the NHEJ pathway by abrogation of 53BP1 nor inhibition of DDR by p53 deficiency rescued these severe phenotypes. Instead, TRF2 deletion provokes an extensive epidermal cell death accompanied by severe inflammation already at E16.5 embryos, which are independent of p53. These results are in contrast with conditional deletion of TRF1 and TPP1 in the skin, where p53 deficiency rescued the associated skin phenotypes, highlighting the comparatively more essential role of TRF2 in skin homeostasis. © 2014 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  15. A Shared Docking Motif in TRF1 and TRF2 Used for Differential Recruitment of Telomeric Proteins

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yong; Yang, Yuting; van Overbeek, Megan; Donigian, Jill R.; Baciu, Paul; de Lange, Titia; Lei, Ming (Michigan-Med); (Rockefeller)

    2008-05-01

    Mammalian telomeres are protected by a six-protein complex: shelterin. Shelterin contains two closely related proteins (TRF1 and TRF2), which recruit various proteins to telomeres. We dissect the interactions of TRF1 and TRF2 with their shared binding partner (TIN2) and other shelterin accessory factors. TRF1 recognizes TIN2 using a conserved molecular surface in its TRF homology (TRFH) domain. However, this same surface does not act as a TIN2 binding site in TRF2, and TIN2 binding to TRF2 is mediated by a region outside the TRFH domain. Instead, the TRFH docking site of TRF2 binds a shelterin accessory factor (Apollo), which does not interact with the TRFH domain of TRF1. Conversely, the TRFH domain of TRF1, but not of TRF2, interacts with another shelterin-associated factor: PinX1.

  16. Evolutionary-conserved telomere-linked helicase genes of fission yeast are repressed by silencing factors, RNAi components and the telomere-binding protein Taz1

    DEFF Research Database (Denmark)

    Hansen, K. R.; Ibarra, P. T.; Thon, G.

    2006-01-01

    In Schizosaccharomyces pombe the RNAi machinery and proteins mediating heterochromatin formation regulate the transcription of non-coding centromeric repeats. These repeats share a high sequence similarity with telomere-linked helicase (tlh) genes, implying an ancestral relationship between the two...... types of elements and suggesting that transcription of the tlh genes might be regulated by the same factors as centromeric repeats. Indeed, we found that mutants lacking the histone methyltransferase Clr4, the Pcu4 cullin, Clr7 or Clr8, accumulate high levels of tlh forward and reverse transcripts....... Mutations and conditions perturbing histone acetylation had similar effects further demonstrating that the tlh genes are normally repressed by heterochromatin. In contrast, mutations in the RNAi factors Dcr1, Ago1 or Rdp1 led only to a modest derepression of the tlh genes indicating an alternate pathway...

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

    Directory of Open Access Journals (Sweden)

    Jan Karlseder

    2004-08-01

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

  18. De novo digenic mutations of telomere-associated proteins and inflammasomes initiate many chronic human diseases: a hypothesis.

    Science.gov (United States)

    Marchesi, Vincent T

    2017-09-01

    Many age-related human diseases have inflammatory components of uncertain causes. It has been proposed that some may be initiated or sustained by doubly mutated immune cells that have both inappropriately activated inflammasomes and enhanced replicative potential. Genes of cells that express mutant TERT and NLRP3 proteins are presumed to be at increased risk for mutagenesis because they reside in subtelomeric regions of chromatin that are deficient in DNA repair mechanisms. Expanded clones of proinflammatory cells can occur throughout one's lifetime and could represent an alternative explanation for some forms of pathologic scarring that are now attributed to truncated telomeres.-Marchesi, V. T. De novo digenic mutations of telomere-associated proteins and inflammasomes initiate many chronic human diseases: a hypothesis. © FASEB.

  19. Telomeres: Implications for Cancer Development

    Directory of Open Access Journals (Sweden)

    Aina Bernal

    2018-01-01

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

  20. Role of HMGB Proteins in Chromatin Dynamics and Telomere Maintenance in Arabidopsis thaliana

    Czech Academy of Sciences Publication Activity Database

    Schrumpfová, P.; Fojtová, Miloslava; Mokroš, P.; Grasser, K.D.; Fajkus, Jiří

    2011-01-01

    Roč. 12, č. 2 (2011), s. 105-111 ISSN 1389-2037 Institutional support: RVO:68081707 Keywords : HMGB * telomere shortening/elongation * plants Subject RIV: BO - Biophysics Impact factor: 2.886, year: 2011

  1. PIAS1-mediated sumoylation promotes STUbL-dependent proteasomal degradation of the human telomeric protein TRF2.

    Science.gov (United States)

    Her, Joonyoung; Jeong, Yu Young; Chung, In Kwon

    2015-10-24

    The human telomeric protein TRF2 protects chromosome ends by facilitating their organization into the protective capping structure. Here we show that the stability of TRF2 is regulated via modification by the small ubiquitin-like modifiers (SUMO). TRF2 specifically interacts with and is sumoylated by PIAS1 in mammalian cells. The proteasome inhibitor stabilizes SUMO-conjugated TRF2 without affecting the level of unmodified TRF2, suggesting that SUMO conjugation is required for proteasomal degradation of TRF2. We also show that RNF4, a mammalian SUMO-targeted ubiquitin ligase, interacts with TRF2 in a SUMO-dependent manner and preferentially targets SUMO-conjugated TRF2 for ubiquitination. Collectively, our data demonstrate that the PIAS1-mediated sumoylation status of TRF2 serves as a molecular switch that controls the level of TRF2 at telomeres. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  2. Break-induced telomere synthesis underlies alternative telomere maintenance.

    Science.gov (United States)

    Dilley, Robert L; Verma, Priyanka; Cho, Nam Woo; Winters, Harrison D; Wondisford, Anne R; Greenberg, Roger A

    2016-11-03

    Homology-directed DNA repair is essential for genome maintenance through templated DNA synthesis. Alternative lengthening of telomeres (ALT) necessitates homology-directed DNA repair to maintain telomeres in about 10-15% of human cancers. How DNA damage induces assembly and execution of a DNA replication complex (break-induced replisome) at telomeres or elsewhere in the mammalian genome is poorly understood. Here we define break-induced telomere synthesis and demonstrate that it utilizes a specialized replisome, which underlies ALT telomere maintenance. DNA double-strand breaks enact nascent telomere synthesis by long-tract unidirectional replication. Proliferating cell nuclear antigen (PCNA) loading by replication factor C (RFC) acts as the initial sensor of telomere damage to establish predominance of DNA polymerase δ (Pol δ) through its POLD3 subunit. Break-induced telomere synthesis requires the RFC-PCNA-Pol δ axis, but is independent of other canonical replisome components, ATM and ATR, or the homologous recombination protein Rad51. Thus, the inception of telomere damage recognition by the break-induced replisome orchestrates homology-directed telomere maintenance.

  3. Telomere dysfunction and chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-02-01

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

  4. The Telomeric Protein TRF2 Regulates Angiogenesis by Binding and Activating the PDGFRβ Promoter.

    Science.gov (United States)

    El Maï, Mounir; Wagner, Kay-Dietrich; Michiels, Jean-François; Ambrosetti, Damien; Borderie, Arnaud; Destree, Sandrine; Renault, Valerie; Djerbi, Nadir; Giraud-Panis, Marie-Josèphe; Gilson, Eric; Wagner, Nicole

    2014-11-06

    Telomeric repeat binding factor 2 (TRF2), which plays a central role in telomere capping, is frequently increased in human tumors. We reveal here that TRF2 is expressed in the vasculature of most human cancer types, where it colocalizes with the Wilms' tumor suppressor WT1. We further show that TRF2 is a transcriptional target of WT1 and is required for proliferation, migration, and tube formation of endothelial cells. These angiogenic effects of TRF2 are uncoupled from its function in telomere capping. Instead, TRF2 binds and transactivates the promoter of the angiogenic tyrosine kinase platelet-derived growth factor receptor β (PDGFRβ). These findings reveal an unexpected role of TRF2 in neoangiogenesis and delineate a distinct function of TRF2 as a transcriptional regulator. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  5. The Telomeric Protein TRF2 Regulates Angiogenesis by Binding and Activating the PDGFRβ Promoter

    Directory of Open Access Journals (Sweden)

    Mounir El Maï

    2014-11-01

    Full Text Available Telomeric repeat binding factor 2 (TRF2, which plays a central role in telomere capping, is frequently increased in human tumors. We reveal here that TRF2 is expressed in the vasculature of most human cancer types, where it colocalizes with the Wilms’ tumor suppressor WT1. We further show that TRF2 is a transcriptional target of WT1 and is required for proliferation, migration, and tube formation of endothelial cells. These angiogenic effects of TRF2 are uncoupled from its function in telomere capping. Instead, TRF2 binds and transactivates the promoter of the angiogenic tyrosine kinase platelet-derived growth factor receptor β (PDGFRβ. These findings reveal an unexpected role of TRF2 in neoangiogenesis and delineate a distinct function of TRF2 as a transcriptional regulator.

  6. The Telomeric Protein TRF2 Regulates Angiogenesis by Binding and Activating the PDGFRβ Promoter

    OpenAIRE

    El Maï, Mounir; Wagner, Kay-Dietrich; Michiels, Jean-François; Ambrosetti, Damien; Borderie, Arnaud; Destree, Sandrine; Renault, Valerie; Djerbi, Nadir; Giraud-Panis, Marie-Josèphe; Gilson, Eric; Wagner, Nicole

    2014-01-01

    Telomeric repeat binding factor 2 (TRF2), which plays a central role in telomere capping, is frequently increased in human tumors. We reveal here that TRF2 is expressed in the vasculature of most human cancer types, where it colocalizes with the Wilms’ tumor suppressor WT1. We further show that TRF2 is a transcriptional target of WT1 and is required for proliferation, migration, and tube formation of endothelial cells. These angiogenic effects of TRF2 are uncoupled from its function in telome...

  7. Telomere elongation chooses TERRA ALTernatives.

    Science.gov (United States)

    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 remains elusive. Mounting evidence suggests that the long noncoding telomeric RNA TERRA renders ALT telomeres recombinogenic by forming RNA:DNA hybrids with the telomeric C-rich strand. TERRA and telomeric hybrids act in concert with a number of other factors, including the RNA endoribonuclease RNaseH1 and the single stranded DNA binding protein RPA. The functional interaction network built upon these different players seems indispensable for ALT telomere maintenance, and digging into the molecular details of this previously unappreciated network might open the way to novel avenues for cancer treatments.

  8. Enhanced electrostatic force microscopy reveals higher-order DNA looping mediated by the telomeric protein TRF2.

    Science.gov (United States)

    Kaur, Parminder; Wu, Dong; Lin, Jiangguo; Countryman, Preston; Bradford, Kira C; Erie, Dorothy A; Riehn, Robert; Opresko, Patricia L; Wang, Hong

    2016-02-09

    Shelterin protein TRF2 modulates telomere structures by promoting dsDNA compaction and T-loop formation. Advancement of our understanding of the mechanism underlying TRF2-mediated DNA compaction requires additional information regarding DNA paths in TRF2-DNA complexes. To uncover the location of DNA inside protein-DNA complexes, we recently developed the Dual-Resonance-frequency-Enhanced Electrostatic force Microscopy (DREEM) imaging technique. DREEM imaging shows that in contrast to chromatin with DNA wrapping around histones, large TRF2-DNA complexes (with volumes larger than TRF2 tetramers) compact DNA inside TRF2 with portions of folded DNA appearing at the edge of these complexes. Supporting coarse-grained molecular dynamics simulations uncover the structural requirement and sequential steps during TRF2-mediated DNA compaction and result in folded DNA structures with protruding DNA loops as seen in DREEM imaging. Revealing DNA paths in TRF2 complexes provides new mechanistic insights into structure-function relationships underlying telomere maintenance pathways.

  9. Telomere functions grounding on TERRA firma.

    Science.gov (United States)

    Azzalin, Claus M; Lingner, Joachim

    2015-01-01

    Long noncoding telomeric repeat-containing RNAs - TERRAs - are transcribed in a regulated manner from telomeres throughout eukaryotes. TERRA molecules consist of chromosome end-specific subtelomeric sequences and telomeric repeats at their 3' ends. Recent work suggests that TERRA sustains several important functions at chromosome ends. TERRA can regulate telomere length through modulation of exonuclease 1 and telomerase, it may promote recruitment of chromatin modifiers to damaged telomeres and thereby enable DNA end-processing, and it may promote telomere protein composition changes during cell cycle progression. Furthermore, telomere transcription regulates chromosome-end mobility within the nucleus. We review how TERRA, by regulated expression and by providing a molecular scaffold for various protein enzymes, can support a large variety of vital functions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Persistent telomere cohesion triggers a prolonged anaphase

    Science.gov (United States)

    Kim, Mi Kyung; Smith, Susan

    2014-01-01

    Telomeres use distinct mechanisms (not used by arms or centromeres) to mediate cohesion between sister chromatids. However, the motivation for a specialized mechanism at telomeres is not well understood. Here we show, using fluorescence in situ hybridization and live-cell imaging, that persistent sister chromatid cohesion at telomeres triggers a prolonged anaphase in normal human cells and cancer cells. Excess cohesion at telomeres can be induced by inhibition of tankyrase 1, a poly(ADP-ribose) polymerase that is required for resolution of telomere cohesion, or by overexpression of proteins required to establish telomere cohesion, the shelterin subunit TIN2 and the cohesin subunit SA1. Regardless of the method of induction, excess cohesion at telomeres in mitosis prevents a robust and efficient anaphase. SA1- or TIN2-induced excess cohesion and anaphase delay can be rescued by overexpression of tankyrase 1. Moreover, we show that primary fibroblasts, which accumulate excess telomere cohesion at mitosis naturally during replicative aging, undergo a similar delay in anaphase progression that can also be rescued by overexpression of tankyrase 1. Our study demonstrates that there are opposing forces that regulate telomere cohesion. The observation that cells respond to unresolved telomere cohesion by delaying (but not completely disrupting) anaphase progression suggests a mechanism for tolerating excess cohesion and maintaining telomere integrity. This attempt to deal with telomere damage may be ultimately futile for aging fibroblasts but useful for cancer cells. PMID:24173716

  11. Mapping of interaction domains of putative telomere-binding proteins AtTRB1 and AtPOT1b from Arabidopsis thaliana.

    Science.gov (United States)

    Schrumpfová, Petra Procházková; Kuchar, Milan; Palecek, Jan; Fajkus, Jirí

    2008-04-30

    We previously searched for interactions between plant telomere-binding proteins and found that AtTRB1, from the single-myb-histone (Smh) family, interacts with the Arabidopsis POT1-like-protein, AtPOT1b, involved in telomere capping. Here we identify domains responsible for that interaction. We also map domains in AtTRB1 responsible for interactions with other Smh-family-members. Our results show that the N-terminal OB-fold-domain of AtPOT1b mediates the interaction with AtTRB1. This domain is characteristic for POT1- proteins and is involved with binding the G-rich-strand of telomeric DNA. AtPOT1b also interacts with AtTRB2 and AtTRB3. The central histone-globular-domain of AtTRB1 is involved with binding to AtTRB2 and 3, as well as to AtPOT1b. AtTRB1-heterodimers with other Smh-family-members are more stable than AtTRB1-homodimers. Our results reveal interaction networks of plant telomeres.

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

    Science.gov (United States)

    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 telomeres specifically in ALT cells and its depletion led to telomeric hybrid accumulation, exposure of single-stranded telomeric DNA, activation of replication protein A at telomeres and abrupt telomere excision. Conversely, overexpression of RNaseH1 weakened the recombinogenic nature of ALT telomeres and led to telomere shortening. Altering cellular RNaseH1 levels did not perturb telomere homoeostasis in telomerase-positive cells. RNaseH1 maintains regulated levels of telomeric RNA–DNA hybrids at ALT telomeres to trigger HR without compromising telomere integrity too severely. PMID:25330849

  13. Increased in vitro glial fibrillary acidic protein expression, telomerase activity, and telomere length after productive human immunodeficiency virus-1 infection in murine astrocytes.

    Science.gov (United States)

    Ojeda, Diego; López-Costa, Juan José; Sede, Mariano; López, Ester María; Berria, María Isabel; Quarleri, Jorge

    2014-02-01

    Although HIV-associated neurocognitive disorders (HAND) result from injury and loss of neurons, productive infection routinely takes place in cells of macrophage lineage. In such a complex context, astrocytosis induced by local chemokines/cytokines is one of the hallmarks of HIV neuropathology. Whether this sustained astrocyte activation is able to alter telomere-aging process is unknown. We hypothesized that interaction of HIV with astrocytes may impact astrocyte telomerase activity (TA) and telomere length in a scenario of astrocytic activation measured by expression of glial fibrillary acidic protein (GFAP). To test this hypothesis, cultured murine astrocytes were challenged with pseudotyped HIV/vesicular stomatitis virus (HIV/VSV) to circumvent the absence of viral receptors; and GFAP, telomerase activity, and telomere length were quantified. As an early and transient event after HIV infection, both TA activity and telomere length were significantly augmented (P < 0.001). Later, a strong negative correlation (-0.8616, P < 0.0001) between virus production and telomerase activity was demonstrated. Once HIV production had reached a peak (7 dpi), the TA decreased, showing levels similar to those of noninfected cells. In contrast, the astrocyte became activated, exhibiting significantly increased levels of GFAP expression directly related to the level of HIV/VSV replication (P < 0.0001). Our results suggest that HIV-infected astrocytes exhibit early disturbance in their cellular functions, such as telomerase activity and telomere length, that may attenuate cell proliferation and enhance the astrocyte dysregulation, contributing to HIV neuropathogenesis. Understanding the mechanisms involved in HIV-mediated persistence by altering the telomere-related aging processes could aid in the development of therapeutic modalities for neurological complications of HIV infection. Copyright © 2013 Wiley Periodicals, Inc.

  14. An H2A Histone Isotype, H2ac, Associates with Telomere and Maintains Telomere Integrity.

    Directory of Open Access Journals (Sweden)

    Chia-Hsin Su

    Full Text Available Telomeres are capped at the ends of eukaryotic chromosomes and are composed of TTAGGG repeats bound to the shelterin complex. Here we report that a replication-dependent histone H2A isotype, H2ac, was associated with telomeres in human cells and co-immunoprecipitates with telomere repeat factor 2 (TRF2 and protection of telomeres protein 1 (POT1, whereas other histone H2A isotypes and mutations of H2ac did not bind to telomeres or these two proteins. The amino terminal basic domain of TRF2 was necessary for the association with H2ac and for the recruitment of H2ac to telomeres. Depletion of H2ac led to loss of telomeric repeat sequences, the appearance of dysfunctional telomeres, and chromosomal instability, including chromosomal breaks and anaphase bridges, as well as accumulation of telomere-associated DNA damage factors in H2ac depleted cells. Additionally, knockdown of H2ac elicits an ATM-dependent DNA damage response at telomeres and depletion of XPF protects telomeres against H2ac-deficiency-induced G-strand overhangs loss and DNA damage response, and prevents chromosomal instability. These findings suggest that the H2A isotype, H2ac, plays an essential role in maintaining telomere functional integrity.

  15. The C. elegans maternal-effect gene clk-2 is essential for embryonic development, encodes a protein homologous to yeast Tel2p and affects telomere length.

    Science.gov (United States)

    Bénard, C; McCright, B; Zhang, Y; Felkai, S; Lakowski, B; Hekimi, S

    2001-10-01

    The Caenorhabditis elegans maternal-effect clk genes are involved in the temporal control of development and behavior. We report the genetic and molecular characterization of clk-2. A temperature-sensitive mutation in the gene clk-2 affects embryonic and post-embryonic development, reproduction, and rhythmic behaviors. Yet, virtually all phenotypes are fully maternally rescued. Embryonic development strictly requires the activity of maternal clk-2 during a narrow time window between oocyte maturation and the two- to four-cell embryonic stage. Positional cloning of clk-2 reveals that it encodes a protein homologous to S. cerevisiae Tel2p. In yeast, the gene TEL2 regulates telomere length and participates in gene silencing at subtelomeric regions. In C. elegans, clk-2 mutants have elongated telomeres, and clk-2 overexpression can lead to telomere shortening. Tel2p has been reported to bind to telomeric DNA repeats in vitro. However, we find that a functional CLK-2::GFP fusion protein is cytoplasmic in worms. We discuss how the phenotype of clk-2 mutants could be the result of altered patterns of gene expression.

  16. Higher order nuclear organization in growth arrest of humanmammary epithelial cells: A novel role for telomere-associated proteinTIN2

    Energy Technology Data Exchange (ETDEWEB)

    Kaminker, Patrick; Plachot, Cedric; Kim, Sahn-Ho; Chung, Peter; Crippen, Danielle; Petersen, Ole W.; Bissell, Mina J.; Campisi, Judith; Lelievre, Sophie A.

    2004-12-15

    Nuclear organization, such as the formation of specific nuclear subdomains, is generally thought to be involved in the control of cellular phenotype; however, there are relatively few specific examples of how mammalian nuclei organize during radical changes in phenotype, such as those which occur during differentiation and growth arrest. Using human mammary epithelial cells (HMECs) in which growth arrest is essential for morphological differentiation, we show that the arrest of cell proliferation is accompanied by a reorganization of the telomere-associated protein, TIN2, into one to three large nuclear subdomains. The large TIN2 domains do not contain telomeres and occur concomitant with the continued presence of TIN2 at telomeres. The TIN2 domains were sensitive to DNAse, but not RNAse, occurred frequently, but not exclusively near nucleoli, and overlapped often with dense domains containing heterochromatin protein l{gamma}. Expression of truncated forms of TIN2 simultaneously prevented the formation of TIN2 domains and relaxed the stringent morphogenesis-induced growth arrest in HMECs. Our findings reveal a novel extra-telomeric organization of TIN2 associated with the control of cell proliferation and identify TIN2 as an important regulator of mammary epithelial differentiation.

  17. Expression of TRF1, TRF2, TIN2, TERT, KU70, and BRCA1 proteins is associated with telomere shortening and may contribute to multistage carcinogenesis of gastric cancer.

    Science.gov (United States)

    Hu, Hua; Zhang, Yang; Zou, Mei; Yang, Shuai; Liang, Xiao-Qiu

    2010-09-01

    Telomere dysfunction is believed to be a significant factor in carcinogenesis. To elucidate the carcinogenesis mechanism in gastric cancer, the expression of telomeric proteins and changes in telomere length were investigated during multistage carcinogenesis of gastric cancer. Tissue samples were obtained during surgical operations from the normal gastric mucosa of 10 patients, the precancerous lesions of 15 patients, the gastric cancer tissues (GC) of 20 patients, and of tumors due to gastric cancer with lymph node metastasis (GCLM) from 5 patients. The expression of TRF1, TRF2, and TIN2 proteins was measured by Western blotting, while the expression of TERT, KU70, and BRCA1 proteins was detected using the immunohistochemical method. The mean telomere length was determined by Southern blotting. Compared with normal gastric mucosa tissues, the expression of TRF1, TRF2, and TIN2 proteins was significantly higher in precancerous lesions, GC, and GCLM (P TRF2, and TIN2 proteins was significantly higher in GC and GCLM than in precancerous lesions (P TRF2, TIN2, TERT, and Ku70 proteins. Our results suggest that the over-expression of telomeric proteins, TRF1, TRF2, TIN2, TERT, and Ku70, and the transposition of the BRCA1 protein may work together to reduce the telomere length in precancerous lesions and gastric cancer, and could contribute to the multistage carcinogenesis of gastric cancer. These findings offer new insight into the mechanism of carcinogenesis in gastric cancer.

  18. TERRA RNA Antagonizes ATRX and Protects Telomeres.

    Science.gov (United States)

    Chu, Hsueh-Ping; Cifuentes-Rojas, Catherine; Kesner, Barry; Aeby, Eric; Lee, Hun-Goo; Wei, Chunyao; Oh, Hyun Jung; Boukhali, Myriam; Haas, Wilhelm; Lee, Jeannie T

    2017-06-29

    Through an integration of genomic and proteomic approaches to advance understanding of long noncoding RNAs, we investigate the function of the telomeric transcript, TERRA. By identifying thousands of TERRA target sites in the mouse genome, we demonstrate that TERRA can bind both in cis to telomeres and in trans to genic targets. We then define a large network of interacting proteins, including epigenetic factors, telomeric proteins, and the RNA helicase, ATRX. TERRA and ATRX share hundreds of target genes and are functionally antagonistic at these loci: whereas TERRA activates, ATRX represses gene expression. At telomeres, TERRA competes with telomeric DNA for ATRX binding, suppresses ATRX localization, and ensures telomeric stability. Depleting TERRA increases telomerase activity and induces telomeric pathologies, including formation of telomere-induced DNA damage foci and loss or duplication of telomeric sequences. We conclude that TERRA functions as an epigenomic modulator in trans and as an essential regulator of telomeres in cis. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Abnormal mRNA Expression Levels of Telomere-Binding Proteins Represent Biomarkers in Myelodysplastic Syndromes: A Case-Control Study

    Directory of Open Access Journals (Sweden)

    Baoshan Liu

    2017-09-01

    Full Text Available Objective: As evidence was shown that abnormal shortening of telomeres begins to accumulate in myelodysplastic syndrome (MDS patients, this study was conducted to determine the relationship between the mRNA expression levels of telomere-binding proteins (TRF1/TRF2/TIN2/TPP1/POT1/RAP1 and the risk level in MDS. Materials and Methods: There were 40 patients with MDS and 40 normal controls in this study. Methods including telomere content assays and quantitative reverse transcription-polymerase chain reaction were used to examine the mRNA levels of TRF1/TRF2/TIN2/ TPP1/POT1/RAP1 in patients with MDS. Results: Compared to the normal group used as a control, the mRNA expression levels of RAP1/POT1/TPP1 of the patients with MDS were decreased, whereas their levels of TRF1/TRF2 and TIN2 were increased. A positive correlation was found between the TRF1, TRF2, and TIN2 mRNA expression levels and the risk level of the International Prognostic Scoring System (IPSS and the World Health Organization Prognostic Scoring System (WPSS criteria; however, a negative correlation was found between RAP1/POT1/TPP1 mRNA expression levels and the risk levels of IPSS and WPSS criteria. Conclusion: Because the reduction of TRF1/TRF2/TIN2 mRNA expression and the increase of RAP1/POT1/TPP1 mRNA expression are closely related to the risk levels of the IPSS and WPSS criteria in MDS, it is thought that these telomere-binding proteins could lead to abnormal telomere length and function, which cause chromosomal abnormalities in MDS. With this evidence, we suggest that those proteins’ mRNA expressions could be used as biomarkers for the assessment of the risk degree of MDS patients.

  20. Telomeres, telomerase and premature ovarian failure

    Directory of Open Access Journals (Sweden)

    Renata Košir Pogačnik

    2011-11-01

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

  1. Design of High-Affinity Stapled Peptides To Target the Repressor Activator Protein 1 (RAP1)/Telomeric Repeat-Binding Factor 2 (TRF2) Protein-Protein Interaction in the Shelterin Complex.

    Science.gov (United States)

    Ran, Xu; Liu, Liu; Yang, Chao-Yie; Lu, Jianfeng; Chen, Yong; Lei, Ming; Wang, Shaomeng

    2016-01-14

    Shelterin, a six-protein complex, plays a fundamental role in protecting both the length and the stability of telomeres. Repressor activator protein 1 (RAP1) and telomeric repeat-binding factor 2 (TRF2) are two subunits in shelterin that interact with each other. Small-molecule inhibitors that block the RAP1/TRF2 protein-protein interaction can disrupt the structure of shelterin and may be employed as pharmacological tools to investigate the biology of shelterin. On the basis of the cocrystal structure of RAP1/TRF2 complex, we have developed first-in-class triazole-stapled peptides that block the protein-protein interaction between RAP1 and TRF2. Our most potent stapled peptide binds to RAP1 protein with a Ki value of 7 nM and is >100 times more potent than the corresponding wild-type TRF2 peptide. On the basis of our high-affinity peptides, we have developed and optimized a competitive, fluorescence polarization (FP) assay for accurate and rapid determination of the binding affinities of our designed compounds and this assay may also assist in the discovery of non-peptide, small-molecule inhibitors capable of blocking the RAP1/TRF2 protein-protein interaction.

  2. Loss of telomere protection: consequences and opportunities.

    Directory of Open Access Journals (Sweden)

    Jacqueline Johanna Leonarda Jacobs

    2013-04-01

    Full Text Available Telomeres are repetitive sequences at the natural ends of linear eukaryotic chromosomes that protect these from recognition as chromosome breaks. Their ability to do so critically depends on the binding of sufficient quantities of functional shelterin, a six-unit protein complex with specific and crucial roles in telomere maintenance and function. Insufficient telomere length, leading to insufficient concentration of shelterin at chromosome ends, or otherwise crippled shelterin function, causes telomere deprotection. While contributing to aging-related pathologies, loss of telomere protection can act as a barrier to tumorigenesis, as dysfunctional telomeres activate DNA-damage-like checkpoint responses that halt cell proliferation or trigger cell death. In addition, dysfunctional telomeres affect cancer development and progression by being a source of genomic instability. Reviewed here are the different approaches that are being undertaken to investigate the mammalian cellular response to telomere dysfunction and its consequences for cancer. Furthermore, it is discussed how current and future knowledge about the mechanisms underlying telomere damage responses might be applied for diagnostic purposes or therapeutic intervention.

  3. Single-Molecule Studies of Telomeres and Telomerase.

    Science.gov (United States)

    Parks, Joseph W; Stone, Michael D

    2017-05-22

    Telomeres are specialized chromatin structures that protect chromosome ends from dangerous processing events. In most tissues, telomeres shorten with each round of cell division, placing a finite limit on cell growth. In rapidly dividing cells, including the majority of human cancers, cells bypass this growth limit through telomerase-catalyzed maintenance of telomere length. The dynamic properties of telomeres and telomerase render them difficult to study using ensemble biochemical and structural techniques. This review describes single-molecule approaches to studying how individual components of telomeres and telomerase contribute to function. Single-molecule methods provide a window into the complex nature of telomeres and telomerase by permitting researchers to directly visualize and manipulate the individual protein, DNA, and RNA molecules required for telomere function. The work reviewed in this article highlights how single-molecule techniques have been utilized to investigate the function of telomeres and telomerase.

  4. Mice with Pulmonary Fibrosis Driven by Telomere Dysfunction

    Directory of Open Access Journals (Sweden)

    Juan M. Povedano

    2015-07-01

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

  5. SMARCAL1 Resolves Replication Stress at ALT Telomeres

    Directory of Open Access Journals (Sweden)

    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.

  6. Actin-binding protein (ABP-280) filamin gene (FLN) maps telomeric to the color vision locus (R/GCP) and centromeric to G6PD in Xq28

    Energy Technology Data Exchange (ETDEWEB)

    Gorlin, J.B. (Brigham and Women' s Hospital, Boston, MA (United States) Dana-Farber Cancer Institute, Boston, MA (United States)); Henske, E.; Hartwig, J.H.; Kwiatkowski, D.J. (Brigham and Women' s Hospital, Boston, MA (United States)); Warren, S.T.; Kunst, C.B. (Emory Univ. School of Medicine, Atlanta, GA (United States)); D' Urso, M.; Palmieri, G. (International Institute of Genetics and Biophysics, Naples, (Italy)); Bruns, G. (Children' s Hospital, Boston, MA (United States))

    1993-08-01

    Actin-binding protein-280 (ABP-280) is a dimeric actin filament-crosslinking protein that promotes orthogonal branching of actin filaments and links actin filaments to membrane glycoproteins. The authors have mapped the ABP-280 filamin gene (FLN) to Xq28 by Southern blot analysis of somatic cell hybrid lines, by fluorescence in situ hybridization, and through identification of portions of the FLN gene within cosmids and YACs mapped to Xq28. The FLN gene is found within a 200-kb region centromeric to the G6PD locus and telomeric to DSX52 and the color vision locus. 23 refs., 2 figs.

  7. The telomere-binding protein TRF2 is required for metronomic therapeutic effects of gemcitabine and capecitabine.

    Science.gov (United States)

    Lee, Wei-Ping; Lan, Keng-Hsin; Li, Chung-Pin; Chao, Yee; Hou, Ming-Chih; Lin, Han-Chieh; Lee, Shou-Dong

    2017-04-01

    Gemcitabine and capecitabine are two effective anticancer agents against solid tumors. The pharmacological mechanisms have been known as incorporation into DNA and thereby inhibition of DNA synthesis. When used as metronomic chemotherapy, they may inhibit angiogenesis and induce immunity. In our previous study, we showed that low-dose gemcitabine caused telomere shortening by stabilizing TRF2 that was required for XPF-dependent telomere loss. In this report, we established a SKOV3.ip1 ascites cell model. Tumor-bearing mice were treated with low-dose gemcitabine (GEM) or capecitabine (CAP). Both GEM and CAP caused telomere shortening and increased expression of TRF2 with improved ascites in nude mice and decreased in vitro clonogenic activity. TRF2 knockdown altered telomeres to a shortened but new status that may evade XPF-dependent telomere loss and conferred resistance of SKOV3.ip1 ascites cells to low-dose GEM and CAP. Our study provides a new mechanism of metronomic chemotherapy i.e. TRF2 is required for metronomic therapeutic effects of gemcitabine and capecitabine. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Telomere Chromatin Condensation Assay (TCCA): a novel approach to study structural telomere integrity.

    Science.gov (United States)

    Gonzalez-Vasconcellos, Iria; Alonso-Rodríguez, Silvia; López-Baltar, Isidoro; Fernández, José Luis

    2015-01-01

    Telomeres, the DNA-protein complexes located at the end of linear eukaryotic chromosomes are essential for genome stability. Improper higher-order chromatin organization at the chromosome ends can give rise to telomeric recombination and genomic instability. We report the development of an assay to quantify differences in the condensation of telomeric chromatin, thereby offering new opportunities to study telomere biology and stability. We have combined a DNA nuclease digestion with a quantitative PCR (qPCR) assay of telomeric DNA, which we term the Telomere Chromatin Condensation Assay (TCCA). By quantifying the relative quantities of telomeric DNA that are progressively digested with the exonuclease Bal 31 the method can discriminate between different levels of telomeric chromatin condensation. The structural chromatin packaging at telomeres shielded against exonuclease digestion delivered an estimate, which we term Chromatin Protection Factor (CPF) that ranged from 1.7 to 2.3 fold greater than that present in unpacked DNA. The CPF was significantly decreased when cell cultures were incubated with the DNA hypomethylating agent 5-azacytidine, demonstrating the ability of the TCCA assay to discriminate between packaging levels of telomeric DNA. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Telomere-binding Protein TRF2 Binds to and Stimulates the Werner and Bloom Syndrome Helicases

    National Research Council Canada - National Science Library

    Patricia L. Opresko; Cayetano von Kobbe; Jean-Philippe Laine; Jeanine Harrigan; Ian D. Hickson; Vilhelm A. Bohr

    2002-01-01

    .... This interaction is mediated by the RecQ conserved C-terminal region of WRN. In vitro , TRF2 demonstrates high affinity for WRN and for another RecQ family member, the Bloom syndrome protein (BLM...

  10. Telomerer og telomerase

    DEFF Research Database (Denmark)

    Bendix, Laila; Kølvraa, Steen

    2010-01-01

    In 2009 the Nobel Prize in Medicine was awarded to EH Blackburn, CW Greider and JW Szostak for their work on "How chromosomes are protected by telomeres and the enzyme telomerase". Telomeres are specialized DNA structures localized at the end of linear chromosomes. Telomeres are known as the biol......In 2009 the Nobel Prize in Medicine was awarded to EH Blackburn, CW Greider and JW Szostak for their work on "How chromosomes are protected by telomeres and the enzyme telomerase". Telomeres are specialized DNA structures localized at the end of linear chromosomes. Telomeres are known...... as the biological clock of the cell, since they shorten with each cell division. Telomerase can elongate telomeres. Telomeres protect chromosome ends against being recognized as double stranded DNA breaks, and are thought to be a guard against cancer. It has furthermore been suggested that telomeres may play a role...

  11. DNA Replication Origins and Fork Progression at Mammalian Telomeres

    Science.gov (United States)

    Higa, Mitsunori; Fujita, Masatoshi; Yoshida, Kazumasa

    2017-01-01

    Telomeres are essential chromosomal regions that prevent critical shortening of linear chromosomes and genomic instability in eukaryotic cells. The bulk of telomeric DNA is replicated by semi-conservative DNA replication in the same way as the rest of the genome. However, recent findings revealed that replication of telomeric repeats is a potential cause of chromosomal instability, because DNA replication through telomeres is challenged by the repetitive telomeric sequences and specific structures that hamper the replication fork. In this review, we summarize current understanding of the mechanisms by which telomeres are faithfully and safely replicated in mammalian cells. Various telomere-associated proteins ensure efficient telomere replication at different steps, such as licensing of replication origins, passage of replication forks, proper fork restart after replication stress, and dissolution of post-replicative structures. In particular, shelterin proteins have central roles in the control of telomere replication. Through physical interactions, accessory proteins are recruited to maintain telomere integrity during DNA replication. Dormant replication origins and/or homology-directed repair may rescue inappropriate fork stalling or collapse that can cause defects in telomere structure and functions. PMID:28350373

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

    Directory of Open Access Journals (Sweden)

    Keiko eMuraki

    2012-10-01

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

  13. Comparative biology of telomeres: where plants stand.

    Science.gov (United States)

    Watson, J Matthew; Riha, Karel

    2010-09-10

    Telomeres are essential structures at the ends of eukaryotic chromosomes. Work on their structure and function began almost 70 years ago in plants and flies, continued through the Nobel Prize winning work on yeast and ciliates, and goes on today in many model and non-model organisms. The basic molecular mechanisms of telomeres are highly conserved throughout evolution, and our current understanding of how telomeres function is a conglomeration of insights gained from many different species. This review will compare the current knowledge of telomeres in plants with other organisms, with special focus on the functional length of telomeric DNA, the search for TRF homologs, the family of POT1 proteins, and the recent discovery of members of the CST complex. Copyright 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  14. Telomerers rolle i cancer

    DEFF Research Database (Denmark)

    Bendix, Laila; Kølvraa, Steen

    2010-01-01

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

  15. The shelterin protein TRF2 inhibits Chk2 activity at telomeres in the absence of DNA damage.

    Science.gov (United States)

    Buscemi, Giacomo; Zannini, Laura; Fontanella, Enrico; Lecis, Daniele; Lisanti, Sofia; Delia, Domenico

    2009-05-26

    The shelterin complex [1] shapes and protects telomeric DNA from being processed as double strand breaks (DSBs) [2, 3]. Here we show that in human undamaged cells, a fraction of the kinase Chk2, a downstream target of ATM and mediator of checkpoint responses and senescence [4, 5], physically interacts with the shelterin subunit TRF2 and colocalizes with this complex at chromosome ends. This interaction, enhanced by TRF2 binding to telomeric DNA, inhibits the activation and senescence-induced function of Chk2 by a mechanism in which TRF2 binding to the N terminus of Chk2 surrounding Thr68 hinders the phosphorylation of this priming site. In response to radiation-induced DSBs, but not chromatin-remodelling agents, the telomeric Chk2-TRF2 binding dissociates in a Chk2 activity-dependent manner. Moreover, active Chk2 phosphorylates TRF2 and decreases its binding to telomeric DNA repeats, corroborating the evidences on the specific TRF2 relocalization in presence of DSBs [6]. Altogether, the capacity of TRF2 to locally repress Chk2 provides an additional level of control by which shelterin restrains the DNA damage response from an unwanted activation [6, 7] and may explain why TRF2 overexpression acts as a telomerase-independent oncogenic stimulus [8].

  16. TERRA: telomeric repeat-containing RNA.

    Science.gov (United States)

    Luke, Brian; Lingner, Joachim

    2009-09-02

    Telomeres, the physical ends of eukaryotic chromosomes, consist of tandem arrays of short DNA repeats and a large set of specialized proteins. A recent analysis has identified telomeric repeat-containing RNA (TERRA), a large non-coding RNA in animals and fungi, which forms an integral component of telomeric heterochromatin. TERRA transcription occurs at most or all chromosome ends and it is regulated by RNA surveillance factors and in response to changes in telomere length. TERRA functions that are emerging suggest important roles in the regulation of telomerase and in orchestrating chromatin remodelling throughout development and cellular differentiation. The accumulation of TERRA at telomeres can also interfere with telomere replication, leading to a sudden loss of telomere tracts. Such a phenotype can be observed upon impairment of the RNA surveillance machinery or in cells from ICF (Immunodeficiency, Centromeric region instability, Facial anomalies) patients, in which TERRA is upregulated because of DNA methylation defects in the subtelomeric region. Thus, TERRA may mediate several crucial functions at the telomeres, a region of the genome that had been considered to be transcriptionally silent.

  17. Accumulation and altered localization of telomere-associated protein TRF2 in immortally transformed and tumor-derived human breast cells

    Energy Technology Data Exchange (ETDEWEB)

    Nijjar, Tarlochan; Bassett, Ekaterina; Garbe, James; Takenaka, Yasuhiro; Stampfer, Martha R.; Gilley, David; Yaswen, Paul

    2004-12-23

    We have used cultured human mammary epithelial cells (HMEC) and breast tumor-derived lines to gain information on defects that occur during breast cancer progression. HMEC immortalized by a variety of agents (the chemical carcinogen benzo(a)pyrene, oncogenes c-myc and ZNF217, and/or dominant negative p53 genetic suppressor element GSE22) displayed marked up regulation (10-15 fold) of the telomere binding protein, TRF2. Up-regulation of TRF2 protein was apparently due to differences in post-transcriptional regulation, as mRNA levels remained comparable in finite life span and immortal HMEC. TRF2 protein was not up-regulated by the oncogenic agents alone in the absence of immortalization, nor by expression of exogenously introduced hTERT genes. We found TRF2 levels to be at least 2-fold higher than in control cells in 11/15 breast tumor cell lines, suggesting that elevated TRF2 levels are a frequent occurrence during the transformation of breast tumor cells in vivo. The dispersed distribution of TRF2 throughout the nuclei in some immortalized and tumor-derived cells indicated that not all the TRF2 was associated with telomeres in these cells. The process responsible for accumulation of TRF2 in immortalized HMEC and breast tumor-derived cell lines may promote tumorigenesis by contributing to the cells ability to maintain an indefinite life span.

  18. Telomere Biology—Insights into an Intriguing Phenomenon

    Directory of Open Access Journals (Sweden)

    Shriram Venkatesan

    2017-06-01

    Full Text Available Bacteria and viruses possess circular DNA, whereas eukaryotes with typically very large DNA molecules have had to evolve into linear chromosomes to circumvent the problem of supercoiling circular DNA of that size. Consequently, such organisms possess telomeres to cap chromosome ends. Telomeres are essentially tandem repeats of any DNA sequence that are present at the ends of chromosomes. Their biology has been an enigmatic one, involving various molecules interacting dynamically in an evolutionarily well-trimmed fashion. Telomeres range from canonical hexameric repeats in most eukaryotes to unimaginably random retrotransposons, which attach to chromosome ends and reverse-transcribe to DNA in some plants and insects. Telomeres invariably associate with specialised protein complexes that envelop it, also regulating access of the ends to legitimate enzymes involved in telomere metabolism. They also transcribe into repetitive RNA which also seems to be playing significant roles in telomere maintenance. Telomeres thus form the intersection of DNA, protein, and RNA molecules acting in concert to maintain chromosome integrity. Telomere biology is emerging to appear ever more complex than previously envisaged, with the continual discovery of more molecules and interplays at the telomeres. This review also includes a section dedicated to the history of telomere biology, and intends to target the scientific audience new to the field by rendering an understanding of the phenomenon of chromosome end protection at large, with more emphasis on the biology of human telomeres. The review provides an update on the field and mentions the questions that need to be addressed.

  19. Telomeric repeat-containing RNA (TERRA) and telomerase are components of telomeres during mammalian gametogenesis.

    Science.gov (United States)

    Reig-Viader, Rita; Vila-Cejudo, Marta; Vitelli, Valerio; Buscà, Rafael; Sabaté, Montserrat; Giulotto, Elena; Caldés, Montserrat Garcia; Ruiz-Herrera, Aurora

    2014-05-01

    Telomeres are ribonucleoprotein structures at the end of chromosomes composed of telomeric DNA, specific-binding proteins, and noncoding RNA (TERRA). Despite their importance in preventing chromosome instability, little is known about the cross talk between these three elements during the formation of the germ line. Here, we provide evidence that both TERRA and the telomerase enzymatic subunit (TERT) are components of telomeres in mammalian germ cells. We found that TERRA colocalizes with telomeres during mammalian meiosis and that its expression progressively increases during spermatogenesis until the beginning of spermiogenesis. While both TERRA levels and distribution would be regulated in a gender-specific manner, telomere-TERT colocalization appears to be regulated based on species-specific characteristics of the telomeric structure. Moreover, we found that TERT localization at telomeres is maintained throughout spermatogenesis as a structural component without affecting telomere elongation. Our results represent the first evidence of colocalization between telomerase and telomeres during mammalian gametogenesis. © 2014 by the Society for the Study of Reproduction, Inc.

  20. A balance between elongation and trimming regulates telomere stability in stem cells

    Science.gov (United States)

    Rivera, Teresa; Haggblom, Candy; Cosconati, Sandro; Karlseder, Jan

    2016-01-01

    Telomere length maintenance ensures self-renewal of human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), however the mechanisms governing telomere length homeostasis in these cell types are unclear. Here, we report that telomere length is determined by the balance between telomere elongation mediated by telomerase and telomere trimming, controlled by the homologous recombination proteins XRCC3 and Nbs1 that generate single-stranded C-rich telomeric DNA and double-stranded telomeric circular DNA (T-circles), respectively. We found that reprogramming of differentiated cells induces T-circle and single stranded C-rich telomeric DNA accumulation, indicating the activation of telomere trimming pathways that compensate telomerase dependent telomere elongation in hiPSCs. Excessive telomere elongation compromises telomere stability and promotes the formation of partially single-stranded telomeric DNA circles (C-circles) in hESCs, suggesting heightened sensitivity of stem cells to replication stress at overly long telomeres. Thus, tight control of telomere length homeostasis is essential to maintain telomere stability in hESCs. PMID:27918544

  1. Telomere in Aging and Age-Related Diseases

    Directory of Open Access Journals (Sweden)

    Anna Meiliana

    2017-12-01

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

  2. hnRNP C1/C2 and Pur-beta proteins mediate induction of senescence by oligonucleotides homologous to the telomere overhang

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    Mulnix RE

    2013-12-01

    Full Text Available Richard E Mulnix,1,* Ryan T Pitman,1 Allison Retzer,2 Ceyda Bertram,1 Kavin Arasi,2 Zachary Crees,2 Jennifer Girard,2 Srijayaprakash B Uppada,1 Amanda L Stone,1 Neelu Puri1,* 1Department of Biomedical Sciences, University of Illinois at Chicago, Rockford, IL, USA; 2College of Medicine, University of Illinois at Chicago, Rockford, IL, USA *These authors contributed equally to this work Background: Experimental disruption of the telomere overhang induces a potent DNA damage response and is the target of newly emerging cancer therapeutics. Introduction of T-oligo, an eleven-base oligonucleotide homologous to the 3'-telomeric overhang, mimics telomere disruption and induces DNA damage responses through activation of p53, p73, p95/Nbs1, E2F1, pRb, and other DNA damage response proteins. ATM (ataxia telangiectasia mutated was once thought to be the primary driver of T-oligo-induced DNA damage responses; however, recent experiments have highlighted other key proteins that may also play a significant role. Methods: To identify proteins associated with T-oligo, MM-AN cells were treated with biotinylated T-oligo or complementary oligonucleotide, cell lysates were run on SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis, and the protein bands observed after treatment of cells with T-oligo or complementary oligonucleotide were analyzed using mass spectrometry. To study the effect of T-oligo on expression of hnRNP C1/C2 (heterogeneous nuclear ribonucleoprotein C1 and C2 and purine-rich element binding proteins (Pur proteins, cells were treated with T-oligo, and immunoblotting experiments were performed. To determine their role in senescence, cells were treated with shRNA (short hairpin ribonucleic acid against these proteins, and senescence was studied using the senescence associated beta-galactosidase assay. Results: Using mass spectrometry, RNA-binding hnRNP C1/C2 and DNA-binding Pur proteins were found to associate with T-oligo. hnRNP C1

  3. Telomeres and human reproduction.

    Science.gov (United States)

    Kalmbach, Keri Horan; Fontes Antunes, Danielle Mota; Dracxler, Roberta Caetano; Knier, Taylor Warner; Seth-Smith, Michelle Louise; Wang, Fang; Liu, Lin; Keefe, David Lawrence

    2013-01-01

    Telomeres mediate biologic aging in organisms as diverse as plants, yeast, and mammals. We propose a telomere theory of reproductive aging that posits telomere shortening in the female germ line as the primary driver of reproductive aging in women. Experimental shortening of telomeres in mice, which normally do not exhibit appreciable oocyte aging, and which have exceptionally long telomeres, recapitulates the aging phenotype of human oocytes. Telomere shortening in mice reduces synapsis and chiasmata, increases embryo fragmentation, cell cycle arrest, apoptosis, spindle dysmorphologies, and chromosome abnormalities. Telomeres are shorter in the oocytes from women undergoing in vitro fertilization, who then produce fragmented, aneuploid embryos that fail to implant. In contrast, the testes are replete with spermatogonia that can rejuvenate telomere reserves throughout the life of the man by expressing telomerase. Differences in telomere dynamics across the life span of men and women may have evolved because of the difference in the inherent risks of aging on reproduction between men and women. Additionally, growing evidence links altered telomere biology to endometriosis and gynecologic cancers, thus future studies should examine the role of telomeres in pathologies of the reproductive tract. Copyright © 2013. Published by Elsevier Inc.

  4. Telomeres and disease: enter TERRA.

    Science.gov (United States)

    Maicher, André; Kastner, Lisa; Luke, Brian

    2012-06-01

    Telomere function is tightly regulated in order to maintain chromosomal stability. When telomeres become dysfunctional, the replicative capacity of cells diminishes and cellular senescence ensues. This can lead to impaired tissue replenishment and eventually degenerative disorders, referred to as telomere syndromes. Cancer can also develop as a result of the genomic instability associated with telomere dysfunction. TERRA (TElomeric Repeat containing RNA) is a long non-coding transcript that stems from sub-telomeric regions and continues into the telomeric tract and is therefore a hybrid of both sub-telomeric and telomeric sequence. In general, increased TERRA transcription is associated with telomere shortening and compromised telomere function. Here we will briefly outline the general principles behind telomere dysfunction-associated diseases. Furthermore, we will discuss the few known links that exist between telomere transcription (TERRA) and disease. Finally, we will speculate on how the understanding, and eventual manipulation, of TERRA transcription could potentially be used in terms of therapeutic strategies.

  5. Telomeres, histone code, and DNA damage response.

    Science.gov (United States)

    Misri, S; Pandita, S; Kumar, R; Pandita, T K

    2008-01-01

    Genomic stability is maintained by telomeres, the end terminal structures that protect chromosomes from fusion or degradation. Shortening or loss of telomeric repeats or altered telomere chromatin structure is correlated with telomere dysfunction such as chromosome end-to-end associations that could lead to genomic instability and gene amplification. The structure at the end of telomeres is such that its DNA differs from DNA double strand breaks (DSBs) to avoid nonhomologous end-joining (NHEJ), which is accomplished by forming a unique higher order nucleoprotein structure. Telomeres are attached to the nuclear matrix and have a unique chromatin structure. Whether this special structure is maintained by specific chromatin changes is yet to be thoroughly investigated. Chromatin modifications implicated in transcriptional regulation are thought to be the result of a code on the histone proteins (histone code). This code, involving phosphorylation, acetylation, methylation, ubiquitylation, and sumoylation of histones, is believed to regulate chromatin accessibility either by disrupting chromatin contacts or by recruiting non-histone proteins to chromatin. The histone code in which distinct histone tail-protein interactions promote engagement may be the deciding factor for choosing specific DSB repair pathways. Recent evidence suggests that such mechanisms are involved in DNA damage detection and repair. Altered telomere chromatin structure has been linked to defective DNA damage response (DDR), and eukaryotic cells have evolved DDR mechanisms utilizing proficient DNA repair and cell cycle checkpoints in order to maintain genomic stability. Recent studies suggest that chromatin modifying factors play a critical role in the maintenance of genomic stability. This review will summarize the role of DNA damage repair proteins specifically ataxia-telangiectasia mutated (ATM) and its effectors and the telomere complex in maintaining genome stability. Copyright 2008 S. Karger

  6. The heritability of telomere length among the elderly and oldest-old

    DEFF Research Database (Denmark)

    Bischoff, Claus; Graakjaer, Jesper; Petersen, Hans Christian

    2005-01-01

    replication problem, explains why the telomere erodes at each cellular turnover. Telomere length is regulated by a number of associated proteins through a number of different signaling pathways. The determinants of telomere length were studied using whole blood samples from 287 twin pairs aged 73 to 95 years......A tight link exists between telomere length and both population doublings of a cell culture and age of a given organism. The more population doublings of the cell culture or the higher the age of the organism, the shorter the telomeres. The proposed model for telomere shortening, called the end...

  7. Short Telomere Length and Ischemic Heart Disease

    DEFF Research Database (Denmark)

    Madrid, Alexander Scheller; Rode, Line; Nordestgaard, Børge Grønne

    2016-01-01

    BACKGROUND: Short telomeres are associated with aging and have been associated with a high risk of ischemic heart disease in observational studies; however, the latter association could be due to residual confounding and/or reverse causation. We wanted to test the hypothesis that short telomeres...... are associated with high risk of ischemic heart disease using a Mendelian randomization approach free of reverse causation and of most confounding. METHODS: We genotyped 3 genetic variants in OBFC1 (oligonucleotide/oligosaccharide binding fold containing 1), TERT (telomerase reverse transcriptase), and TERC...... (telomerase RNA component), which code for proteins and RNA involved in telomere maintenance. We studied 105 055 individuals from Copenhagen; 17 235 of these individuals were diagnosed with ischemic heart disease between 1977 and 2013, and 66 618 had telomere length measured. For genetic studies, we further...

  8. Telomere Length and Mortality

    DEFF Research Database (Denmark)

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

    2008-01-01

    Leukocyte telomere length, representing the mean length of all telomeres in leukocytes, is ostensibly a bioindicator of human aging. The authors hypothesized that shorter telomeres might forecast imminent mortality in elderly people better than leukocyte telomere length. They performed mortality...... telomeres predicted the death of the first co-twin better than the mTRFL did (mTRFL: 0.56, 95% confidence interval (CI): 0.49, 0.63; mTRFL(50): 0.59, 95% CI: 0.52, 0.66; mTRFL(25): 0.59, 95% CI: 0.52, 0.66; MTRFL: 0.60, 95% CI: 0.53, 0.67). The telomere-mortality association was stronger in years 3-4 than...

  9. SLX4 Assembles a Telomere Maintenance Toolkit by Bridging Multiple Endonucleases with Telomeres

    Directory of Open Access Journals (Sweden)

    Bingbing Wan

    2013-09-01

    Full Text Available SLX4 interacts with several endonucleases to resolve structural barriers in DNA metabolism. SLX4 also interacts with telomeric protein TRF2 in human cells. The molecular mechanism of these interactions at telomeres remains unknown. Here, we report the crystal structure of the TRF2-binding motif of SLX4 (SLX4TBM in complex with the TRFH domain of TRF2 (TRF2TRFH and map the interactions of SLX4 with endonucleases SLX1, XPF, and MUS81. TRF2 recognizes a unique HxLxP motif on SLX4 via the peptide-binding site in its TRFH domain. Telomeric localization of SLX4 and associated nucleases depend on the SLX4-endonuclease and SLX4-TRF2 interactions and the protein levels of SLX4 and TRF2. SLX4 assembles an endonuclease toolkit that negatively regulates telomere length via SLX1-catalyzed nucleolytic resolution of telomere DNA structures. We propose that the SLX4-TRF2 complex serves as a double-layer scaffold bridging multiple endonucleases with telomeres for recombination-based telomere maintenance.

  10. Telomere length modulation in human astroglial brain tumors.

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    Domenico La Torre

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

  11. The yeast VPS genes affect telomere length regulation.

    Science.gov (United States)

    Rog, Ofer; Smolikov, Sarit; Krauskopf, Anat; Kupiec, Martin

    2005-01-01

    Eukaryotic cells invest a large proportion of their genome in maintaining telomere length homeostasis. Among the 173 non-essential yeast genes found to affect telomere length, a large proportion is involved in vacuolar traffic. When mutated, these vacuolar protein-sorting (VPS) genes lead to telomeres shorter than those observed in the wild type. Using genetic analysis, we characterized the pathway by which VPS15, VPS34, VPS22, VPS23 and VPS28 affect the telomeres. Our results indicate that these VPS genes affect telomere length through a single pathway and that this effect requires the activity of telomerase and the Ku heterodimer, but not the activity of Tel1p or Rif2p. We present models to explain the link between vacuolar traffic and telomere length homeostasis.

  12. A balanced transcription between telomerase and the telomeric DNA-binding proteins TRF1, TRF2 and Pot1 in resting, activated, HTLV-1-transformed and Tax-expressing human T lymphocytes

    Directory of Open Access Journals (Sweden)

    Gilson Eric

    2005-12-01

    Full Text Available Abstract Background The functional state of human telomeres is controlled by telomerase and by a protein complex named shelterin, including the telomeric DNA-binding proteins TRF1, TRF2 and Pot1 involved in telomere capping functions. The expression of hTERT, encoding the catalytic subunit of telomerase, plays a crucial role in the control of lymphocyte proliferation by maintaining telomere homeostasis. It has been previously found that hTERT activity is down-regulated by the human T cell leukaemia virus type 1 (HTLV-1 Tax protein in HTLV-1 transformed T lymphocytes. In this study, we have examined the effects of Tax expression on the transcriptional profile of telomerase and of shelterin in human T lymphocytes. Results We first provide evidence that the up-regulation of hTERT transcription in activated CD4+ T lymphocytes is associated with a down-regulation of that of TERF1, TERF2 and POT1 genes. Next, the down-regulation of hTERT transcription by Tax in HTLV-1 transformed or in Tax-expressing T lymphocytes is found to correlate with a significant increase of TRF2 and/or Pot1 mRNAs. Finally, ectopic expression of hTERT in one HTLV-1 T cell line induces a marked decrease in the transcription of the POT1 gene. Collectively, these observations predict that the increased transcriptional expression of shelterin genes is minimizing the impact on telomere instability induced by the down-regulation of hTERT by Tax. Conclusion These findings support the notion that Tax, telomerase and shelterin play a critical role in the proliferation of HTLV-1 transformed T lymphocytes.

  13. Trypanosoma brucei RAP1 maintains telomere and subtelomere integrity by suppressing TERRA and telomeric RNA:DNA hybrids.

    Science.gov (United States)

    Nanavaty, Vishal; Sandhu, Ranjodh; Jehi, Sanaa E; Pandya, Unnati M; Li, Bibo

    2017-06-02

    Trypanosoma brucei causes human African trypanosomiasis and regularly switches its major surface antigen, VSG, thereby evading the host's immune response. VSGs are monoallelically expressed from subtelomeric expression sites (ESs), and VSG switching exploits subtelomere plasticity. However, subtelomere integrity is essential for T. brucei viability. The telomeric transcript, TERRA, was detected in T. brucei previously. We now show that the active ES-adjacent telomere is transcribed. We find that TbRAP1, a telomere protein essential for VSG silencing, suppresses VSG gene conversion-mediated switching. Importantly, TbRAP1 depletion increases the TERRA level, which appears to result from longer read-through into the telomere downstream of the active ES. Depletion of TbRAP1 also results in more telomeric RNA:DNA hybrids and more double strand breaks (DSBs) at telomeres and subtelomeres. In TbRAP1-depleted cells, expression of excessive TbRNaseH1, which cleaves the RNA strand of the RNA:DNA hybrid, brought telomeric RNA:DNA hybrids, telomeric/subtelomeric DSBs and VSG switching frequency back to WT levels. Therefore, TbRAP1-regulated appropriate levels of TERRA and telomeric RNA:DNA hybrid are fundamental to subtelomere/telomere integrity. Our study revealed for the first time an important role of a long, non-coding RNA in antigenic variation and demonstrated a link between telomeric silencing and subtelomere/telomere integrity through TbRAP1-regulated telomere transcription. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  14. Cancer and aging: The importance of telomeres in genome maintenance

    Energy Technology Data Exchange (ETDEWEB)

    Rodier, Francis; Kim, Sahn-ho; Nijjar, Tarlochan; Yaswen, Paul; Campisi, Judith

    2004-10-01

    Telomeres are the specialized DNA-protein structures that cap the ends of linear chromosomes, thereby protecting them from degradation and fusion by cellular DNA repair processes. In vertebrate cells, telomeres consist of several kilobase pairs of DNA having the sequence TTAGGG, a few hundred base pairs of single-stranded DNA at the 3' end of the telomeric DNA tract, and a host of proteins that organize the telomeric double and single stranded DNA into a protective structure. Functional telomeres are essential for maintaining the integrity and stability of genomes. When combined with loss of cell cycle checkpoint controls, telomere dysfunction can lead to genomic instability, a common cause and hallmark of cancer. Consequently, normal mammalian cells respond to dysfunctional telomeres by undergoing apoptosis (programmed cell death) or cellular senescence (permanent cell cycle arrest), two cellular tumor suppressor mechanisms. These tumor suppressor mechanisms are potent suppressors of cancer, but recent evidence suggests that they can antagonistically also contribute to aging phenotypes. Here, we review what is known about the structure and function of telomeres in mammalian cells, particularly human cells, and how telomere dysfunction may arise and contribute to cancer and aging phenotypes.

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

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    Endang Purwaningsih

    2017-07-01

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

  16. The PML-associated protein DEK regulates the balance of H3.3 loading on chromatin and is important for telomere integrity

    Science.gov (United States)

    Ivanauskiene, Kristina; Delbarre, Erwan; McGhie, James D.; Küntziger, Thomas

    2014-01-01

    Histone variant H3.3 is deposited in chromatin at active sites, telomeres, and pericentric heterochromatin by distinct chaperones, but the mechanisms of regulation and coordination of chaperone-mediated H3.3 loading remain largely unknown. We show here that the chromatin-associated oncoprotein DEK regulates differential HIRA- and DAAX/ATRX-dependent distribution of H3.3 on chromosomes in somatic cells and embryonic stem cells. Live cell imaging studies show that nonnucleosomal H3.3 normally destined to PML nuclear bodies is re-routed to chromatin after depletion of DEK. This results in HIRA-dependent widespread chromatin deposition of H3.3 and H3.3 incorporation in the foci of heterochromatin in a process requiring the DAXX/ATRX complex. In embryonic stem cells, loss of DEK leads to displacement of PML bodies and ATRX from telomeres, redistribution of H3.3 from telomeres to chromosome arms and pericentric heterochromatin, induction of a fragile telomere phenotype, and telomere dysfunction. Our results indicate that DEK is required for proper loading of ATRX and H3.3 on telomeres and for telomeric chromatin architecture. We propose that DEK acts as a “gatekeeper” of chromatin, controlling chromatin integrity by restricting broad access to H3.3 by dedicated chaperones. Our results also suggest that telomere stability relies on mechanisms ensuring proper histone supply and routing. PMID:25049225

  17. Telomere length and depression

    DEFF Research Database (Denmark)

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

    2017-01-01

    as prospectively and genetically. METHOD: Telomere length and three polymorphisms, TERT, TERC and OBFC1, were measured in 67 306 individuals aged 20-100 years from the Danish general population and associated with register-based attendance at hospital for depression and purchase of antidepressant medication.......0-21.5). The genetic analyses suggested that telomere length was not causally associated with attendance at hospital for depression or with purchase of antidepressant medication. CONCLUSIONS: Short telomeres were not associated with depression in prospective or in causal, genetic analyses.......BACKGROUND: Depression has been cross-sectionally associated with short telomeres as a measure of biological age. However, the direction and nature of the association is currently unclear. AIMS: We examined whether short telomere length is associated with depression cross-sectionally as well...

  18. What Makes Telomeres Unique?

    Science.gov (United States)

    Sieradzan, Adam K; Krupa, Paweł; Wales, David J

    2017-03-16

    Telomeres are repetitive nucleotide sequences, which are essential for protecting the termini of chromosomes. Thousands of such repetitions are necessary to maintain the stability of the whole chromosome. Several similar repeated telomeric sequences have been found in different species, but why has nature chosen them? What features do telomeres have in common? In this article, we study the physical properties of human-like (TTAGGG), plant (TTTAGG), insect (TTAGG), and Candida guilermondi (GGTGTAC) telomeres in comparison with seven control, nontelomeric sequences. We used steered molecular dynamics with the nucleic acid united residue (NARES) coarse-grained force field, which we compared with the all-atom AMBER14 force field and experimental data. Our results reveal important features in all of the telomeric sequences, including their exceptionally high mechanical resistance and stability to untangling and stretching, compared to those of nontelomeric sequences. We find that the additional stability of the telomeres comes from their ability to form triplex structures and wrap around loose chains of linear DNA by regrabbing the chain. We find that, with slower pulling speed, regrabbing and triplex formation is more frequent. We also found that some of the sequences can form triplexes experimentally, such as TTTTTCCCC, and can mimic telomeric properties.

  19. Elevated levels of TRF2 induce telomeric ultrafine anaphase bridges and rapid telomere deletions.

    Science.gov (United States)

    Nera, Bernadette; Huang, Hui-Shun; Lai, Thao; Xu, Lifeng

    2015-12-07

    The shelterin protein TRF2 is essential for chromosome-end protection. Depletion of TRF2 causes chromosome end-to-end fusions, initiating genomic instability that can be cancer promoting. Paradoxically, significant increased levels of TRF2 are observed in a subset of human cancers. Experimental overexpression of TRF2 has also been shown to induce telomere shortening, through an unknown mechanism. Here we report that TRF2 overexpression results in replication stalling in duplex telomeric repeat tracts and the subsequent formation of telomeric ultrafine anaphase bridges (UFBs), ultimately leading to stochastic loss of telomeric sequences. These TRF2 overexpression-induced telomere deletions generate chromosome fusions resembling those detected in human cancers and in mammalian cells containing critically shortened telomeres. Therefore, our findings have uncovered a second pathway by which altered TRF2 protein levels can induce end-to-end fusions. The observations also provide mechanistic insight into the molecular basis of genomic instability in tumour cells containing significantly increased TRF2 levels.

  20. Elevated TRF2 in advanced breast cancers with short telomeres.

    Science.gov (United States)

    Diehl, Malissa C; Idowu, Michael O; Kimmelshue, Katherine N; York, Timothy P; Jackson-Cook, Colleen K; Turner, Kristi C; Holt, Shawn E; Elmore, Lynne W

    2011-06-01

    Telomere repeat binding factor 2 (TRF2) binds directly to telomeres and preserves the structural integrity of chromosome ends. In vitro models suggest that expression of TRF2 protein increases during mammary cancer progression. However, a recent study has reported that TRF2 mRNA levels tend to be lower in clinical specimens of malignant breast tissue. Here, we conduct the first large-scale investigation to assess the levels and cellular localization of the TRF2 protein in normal, pre-malignant and malignant breast tissues. Breast tissue arrays, containing normal, ductal carcinoma in situ (DCIS) and invasive carcinoma specimens, were used to assess the expression and localization of TRF2 protein. Telomere lengths were semi-quantitatively measured using a pantelomeric peptide nucleic acid probe. A mixed effects modeling approach was used to assess the relationship between TRF2 expression and telomeric signal scores across disease states or clinical staging. We demonstrate that TRF2 is exclusively nuclear with a trend toward lower expression with increased malignancy. More case-to-case variability of TRF2 immunostaining intensity was noted amongst the invasive carcinomas than the other disease groups. Invasive carcinomas also displayed variable telomere lengths while telomeres in normal mammary epithelium were generally longer. Statistical analyses revealed that increased TRF2 immunostaining intensity in invasive carcinomas is associated with shorter telomeres and shorter telomeres correlate with a higher TNM stage. All immortalized and cancer cell lines within the array displayed strong, nuclear TRF2 expression. Our data indicate that elevated expression of TRF2 is not a frequent occurrence during the transformation of breast cancer cells in vivo, but higher levels of this telomere-binding protein may be important for protecting advanced cancer cells with critically short telomeres. Our findings also reinforce the concept that serially propagated cancer cells

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

    Directory of Open Access Journals (Sweden)

    Eugene V Shakirov

    2012-07-01

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

  2. Human Rap1 modulates TRF2 attraction to telomeric DNA

    OpenAIRE

    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...

  3. Chromatin structure in telomere dynamics

    Directory of Open Access Journals (Sweden)

    Alessandra eGalati

    2013-03-01

    Full Text Available The establishment of a specific nucleoprotein structure, the telomere, is required to ensure the protection of chromosome ends from being recognized as DNA damage sites. Telomere shortening below a critical length triggers a DNA damage response that leads to replicative senescence. In normal human somatic cells, characterized by telomere shortening with each cell division, telomere uncapping is a regulated process associated with cell turnover. Nevertheless, telomere dysfunction has also been associated with genomic instability, cell transformation and cancer. Despite the essential role telomeres play in chromosome protection and in tumorigenesis, our knowledge of the chromatin structure involved in telomere maintenance is still limited. Here we review the recent findings on chromatin modifications associated with the dynamic changes of telomeres from protected to de-protected state and their role in telomere functions.

  4. The role of ATM in the deficiency in nonhomologous end-joining near telomeres in a human cancer cell line.

    Directory of Open Access Journals (Sweden)

    Keiko Muraki

    2013-03-01

    Full Text Available Telomeres distinguish chromosome ends from double-strand breaks (DSBs and prevent chromosome fusion. However, telomeres can also interfere with DNA repair, as shown by a deficiency in nonhomologous end joining (NHEJ and an increase in large deletions at telomeric DSBs. The sensitivity of telomeric regions to DSBs is important in the cellular response to ionizing radiation and oncogene-induced replication stress, either by preventing cell division in normal cells, or by promoting chromosome instability in cancer cells. We have previously proposed that the telomeric protein TRF2 causes the sensitivity of telomeric regions to DSBs, either through its inhibition of ATM, or by promoting the processing of DSBs as though they are telomeres, which is independent of ATM. Our current study addresses the mechanism responsible for the deficiency in repair of DSBs near telomeres by combining assays for large deletions, NHEJ, small deletions, and gross chromosome rearrangements (GCRs to compare the types of events resulting from DSBs at interstitial and telomeric DSBs. Our results confirm the sensitivity of telomeric regions to DSBs by demonstrating that the frequency of GCRs is greatly increased at DSBs near telomeres and that the role of ATM in DSB repair is very different at interstitial and telomeric DSBs. Unlike at interstitial DSBs, a deficiency in ATM decreases NHEJ and small deletions at telomeric DSBs, while it increases large deletions. These results strongly suggest that ATM is functional near telomeres and is involved in end protection at telomeric DSBs, but is not required for the extensive resection at telomeric DSBs. The results support our model in which the deficiency in DSB repair near telomeres is a result of ATM-independent processing of DSBs as though they are telomeres, leading to extensive resection, telomere loss, and GCRs involving alternative NHEJ.

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

    Directory of Open Access Journals (Sweden)

    Grazia Daniela Raffa

    2013-05-01

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

  6. Protection of Drosophila chromosome ends through minimal telomere capping.

    Science.gov (United States)

    Dubruille, Raphaëlle; Loppin, Benjamin

    2015-05-15

    In Drosophila, telomere-capping proteins have the remarkable capacity to recognize chromosome ends in a sequence-independent manner. This epigenetic protection is essential to prevent catastrophic ligations of chromosome extremities. Interestingly, capping proteins occupy a large telomere chromatin domain of several kilobases; however, the functional relevance of this to end protection is unknown. Here, we investigate the role of the large capping domain by manipulating HOAP (encoded by caravaggio) capping-protein expression in the male germ cells, where telomere protection can be challenged without compromising viability. We show that the exhaustion of HOAP results in a dramatic reduction of other capping proteins at telomeres, including K81 [encoded by ms(3)K81], which is essential for male fertility. Strikingly however, we demonstrate that, although capping complexes are barely detected in HOAP-depleted male germ cells, telomere protection and male fertility are not dramatically affected. Our study thus demonstrates that efficient protection of Drosophila telomeres can be achieved with surprisingly low amounts of capping complexes. We propose that these complexes prevent fusions by acting at the very extremity of chromosomes, reminiscent of the protection conferred by extremely short telomeric arrays in yeast or mammalian systems. © 2015. Published by The Company of Biologists Ltd.

  7. Platination of telomeric DNA by cisplatin disrupts recognition by TRF2 and TRF1.

    Science.gov (United States)

    Ourliac-Garnier, Isabelle; Poulet, Anaïs; Charif, Razan; Amiard, Simon; Magdinier, Frédérique; Rezaï, Keyvan; Gilson, Eric; Giraud-Panis, Marie-Josèphe; Bombard, Sophie

    2010-06-01

    Telomeres, the nucleoprotein complexes located at the ends of chromosomes, are involved in chromosome protection and genome stability. Telomeric repeat binding factor 1 (TRF1) and telomeric repeat binding factor 2 (TRF2) are the two telomeric proteins that bind to duplex telomeric DNA through interactions between their C-terminal domain and several guanines of the telomeric tract. Since the antitumour drug cisplatin binds preferentially to two adjacent guanines, we have investigated whether cisplatin adducts could affect the binding of TRF1 and TRF2 to telomeric DNA and the property of TRF2 to stimulate telomeric invasion, a process that is thought to participate in the formation of the t-loop. We show that the binding of TRF1 and TRF2 to telomeric sequences selectively modified by one GG chelate of cisplatin is markedly affected by cisplatin but that the effect is more drastic for TRF2 than for TRF1 (3-5-fold more sensitivity for TRF2 than for TRF1). We also report that platinum adducts cause a decrease in TRF2-dependent stimulation of telomeric invasion in vitro. Finally, in accordance with in vitro data, analysis of telomeric composition after cisplatin treatment reveals that 60% of TRF2 dissociate from telomeres.

  8. Human XPF controls TRF2 and telomere length maintenance through distinctive mechanisms.

    Science.gov (United States)

    Wu, Yili; Mitchell, Taylor R H; Zhu, Xu-Dong

    2008-10-01

    XPF-ERCC1, a structure-specific endonuclease, is involved in nucleotide excision repair, crosslink repair and homologous recombination. XPF-ERCC1 is also found to interact with TRF2, a duplex telomeric DNA binding protein. We have previously shown that XPF-ERCC1 is required for TRF2-promoted telomere shortening. However, whether XPF-ERCC1 by itself has a role in telomere length maintenance has not been determined. Here we report that overexpression of XPF induces telomere shortening in XPF-proficient cells whereas XPF complementation suppresses telomere lengthening in XPF-deficient cells. These results suggest that XPF-ERCC1 can function as a negative mediator of telomere length maintenance. In addition, we find that introduction of wild type XPF into XPF-deficient cells leads to over 40% reduction in TRF2 association with telomeric DNA, indicating that XPF-ERCC1 negatively regulates TRF2 binding to telomeric DNA. Furthermore, we show that XPF carrying mutations in the conserved nuclease domain fails to control TRF2 association with telomeric DNA but it is competent for modulating telomere length maintenance. These results imply that XPF-ERCC1 controls TRF2 and telomere length maintenance through two distinctive mechanisms, with the former requiring its nuclease activity. Our results further imply that TRF2 association with telomeres may be deregulated in cells derived from XPF patients.

  9. Telomeric noncoding RNA TERRA is induced by telomere shortening to nucleate telomerase molecules at short telomeres.

    Science.gov (United States)

    Cusanelli, Emilio; Romero, Carmina Angelica Perez; Chartrand, Pascal

    2013-09-26

    Elongation of a short telomere depends on the action of multiple telomerase molecules, which are visible as telomerase RNA foci or clusters associated with telomeres in yeast and mammalian cells. How several telomerase molecules act on a single short telomere is unknown. Herein, we report that the telomeric noncoding RNA TERRA is involved in the nucleation of telomerase molecules into clusters prior to their recruitment at a short telomere. We find that telomere shortening induces TERRA expression, leading to the accumulation of TERRA molecules into a nuclear focus. Simultaneous time-lapse imaging of telomerase RNA and TERRA reveals spontaneous events of telomerase nucleation on TERRA foci in early S phase, generating TERRA-telomerase clusters. This cluster is subsequently recruited to the short telomere from which TERRA transcripts originate during S phase. We propose that telomere shortening induces noncoding RNA expression to coordinate the recruitment and activity of telomerase molecules at short telomeres. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. CTCF driven TERRA transcription facilitates completion of telomere DNA replication.

    Science.gov (United States)

    Beishline, Kate; Vladimirova, Olga; Tutton, Stephen; Wang, Zhuo; Deng, Zhong; Lieberman, Paul M

    2017-12-13

    Telomere repeat DNA forms a nucleo-protein structure that can obstruct chromosomal DNA replication, especially under conditions of replication stress. Transcription of telomere repeats can initiate at subtelomeric CTCF-binding sites to generate telomere repeat-encoding RNA (TERRA), but the role of transcription, CTCF, and TERRA in telomere replication is not known. Here, we have used CRISPR/Cas9 gene editing to mutate CTCF-binding sites at the putative start site of TERRA transcripts for a class of subtelomeres. Under replication stress, telomeres lacking CTCF-driven TERRA exhibit sister-telomere loss and upon entry into mitosis, exhibit the formation of ultra-fine anaphase bridges and micronuclei. Importantly, these phenotypes could be rescued by the forced transcription of TERRA independent of CTCF binding. Our findings indicate that subtelomeric CTCF facilitates telomeric DNA replication by promoting TERRA transcription. Our findings also demonstrate that CTCF-driven TERRA transcription acts in cis to facilitate telomere repeat replication and chromosome stability.

  11. TRF2-RAP1 is required to protect telomeres from engaging in homologous recombination-mediated deletions and fusions.

    Science.gov (United States)

    Rai, Rekha; Chen, Yong; Lei, Ming; Chang, Sandy

    2016-03-04

    Repressor/activator protein 1 (RAP1) is a highly conserved telomere-interacting protein. Yeast Rap1 protects telomeres from non-homologous end joining (NHEJ), plays important roles in telomere length control and is involved in transcriptional gene regulation. However, a role for mammalian RAP1 in telomere end protection remains controversial. Here we present evidence that mammalian RAP1 is essential to protect telomere from homology directed repair (HDR) of telomeres. RAP1 cooperates with the basic domain of TRF2 (TRF2(B)) to repress PARP1 and SLX4 localization to telomeres. Without RAP1 and TRF2(B), PARP1 and SLX4 HR factors promote rapid telomere resection, resulting in catastrophic telomere loss and the generation of telomere-free chromosome fusions in both mouse and human cells. The RAP1 Myb domain is required to repress both telomere loss and formation of telomere-free fusions. Our results highlight the importance of the RAP1-TRF2 heterodimer in protecting telomeres from inappropriate processing by the HDR pathway.

  12. Telomere attrition due to infection

    National Research Council Canada - National Science Library

    Ilmonen, Petteri; Kotrschal, Alexander; Penn, Dustin J

    2008-01-01

    Telomeres--the terminal caps of chromosomes--become shorter as individuals age, and there is much interest in determining what causes telomere attrition since this process may play a role in biological aging...

  13. Post-translational modifications of TRF1 and TRF2 and their roles in telomere maintenance.

    Science.gov (United States)

    Walker, John R; Zhu, Xu-Dong

    2012-06-01

    Telomeres, heterochromatic structures, found at the ends of linear eukaryotic chromosomes, function to protect natural chromosome ends from nucleolytic attack. Human telomeric DNA is bound by a telomere-specific six-subunit protein complex, termed shelterin/telosome. The shelterin subunits TRF1 and TRF2 bind in a sequence-specific manner to double-stranded telomeric DNA, providing a vital platform for recruitment of additional shelterin proteins as well as non-shelterin factors crucial for the maintenance of telomere length and structure. Both TRF1 and TRF2 are engaged in multiple roles at telomeres including telomere protection, telomere replication, sister telomere resolution and telomere length maintenance. Regulation of TRF1 and TRF2 in these various processes is controlled by post-translational modifications, at times in a cell-cycle-dependent manner, affecting key functions such as DNA binding, dimerization, localization, degradation and interactions with other proteins. Here we review the post-translational modifications of TRF1 and TRF2 and discuss the mechanisms by which these modifications contribute to the function of these two proteins. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  14. TRF2 controls telomeric nucleosome organization in a cell cycle phase-dependent manner.

    Directory of Open Access Journals (Sweden)

    Alessandra Galati

    Full Text Available Mammalian telomeres stabilize chromosome ends as a result of their assembly into a peculiar form of chromatin comprising a complex of non-histone proteins named shelterin. TRF2, one of the shelterin components, binds to the duplex part of telomeric DNA and is essential to fold the telomeric chromatin into a protective cap. Although most of the human telomeric DNA is organized into tightly spaced nucleosomes, their role in telomere protection and how they interplay with telomere-specific factors in telomere organization is still unclear. In this study we investigated whether TRF2 can regulate nucleosome assembly at telomeres.By means of chromatin immunoprecipitation (ChIP and Micrococcal Nuclease (MNase mapping assay, we found that the density of telomeric nucleosomes in human cells was inversely proportional to the dosage of TRF2 at telomeres. This effect was not observed in the G1 phase of the cell cycle but appeared coincident of late or post-replicative events. Moreover, we showed that TRF2 overexpression altered nucleosome spacing at telomeres increasing internucleosomal distance. By means of an in vitro nucleosome assembly system containing purified histones and remodeling factors, we reproduced the short nucleosome spacing found in telomeric chromatin. Importantly, when in vitro assembly was performed in the presence of purified TRF2, nucleosome spacing on a telomeric DNA template increased, in agreement with in vivo MNase mapping.Our results demonstrate that TRF2 negatively regulates the number of nucleosomes at human telomeres by a cell cycle-dependent mechanism that alters internucleosomal distance. These findings raise the intriguing possibility that telomere protection is mediated, at least in part, by the TRF2-dependent regulation of nucleosome organization.

  15. TRF2 controls telomeric nucleosome organization in a cell cycle phase-dependent manner.

    Science.gov (United States)

    Galati, Alessandra; Magdinier, Frédérique; Colasanti, Valentina; Bauwens, Serge; Pinte, Sébastien; Ricordy, Ruggero; Giraud-Panis, Marie-Josèphe; Pusch, Miriam Caroline; Savino, Maria; Cacchione, Stefano; Gilson, Eric

    2012-01-01

    Mammalian telomeres stabilize chromosome ends as a result of their assembly into a peculiar form of chromatin comprising a complex of non-histone proteins named shelterin. TRF2, one of the shelterin components, binds to the duplex part of telomeric DNA and is essential to fold the telomeric chromatin into a protective cap. Although most of the human telomeric DNA is organized into tightly spaced nucleosomes, their role in telomere protection and how they interplay with telomere-specific factors in telomere organization is still unclear. In this study we investigated whether TRF2 can regulate nucleosome assembly at telomeres.By means of chromatin immunoprecipitation (ChIP) and Micrococcal Nuclease (MNase) mapping assay, we found that the density of telomeric nucleosomes in human cells was inversely proportional to the dosage of TRF2 at telomeres. This effect was not observed in the G1 phase of the cell cycle but appeared coincident of late or post-replicative events. Moreover, we showed that TRF2 overexpression altered nucleosome spacing at telomeres increasing internucleosomal distance. By means of an in vitro nucleosome assembly system containing purified histones and remodeling factors, we reproduced the short nucleosome spacing found in telomeric chromatin. Importantly, when in vitro assembly was performed in the presence of purified TRF2, nucleosome spacing on a telomeric DNA template increased, in agreement with in vivo MNase mapping.Our results demonstrate that TRF2 negatively regulates the number of nucleosomes at human telomeres by a cell cycle-dependent mechanism that alters internucleosomal distance. These findings raise the intriguing possibility that telomere protection is mediated, at least in part, by the TRF2-dependent regulation of nucleosome organization.

  16. Mathematical model of alternative mechanism of telomere length maintenance.

    Science.gov (United States)

    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.

  17. Does oxidative stress shorten telomeres?

    NARCIS (Netherlands)

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

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

  18. Telomerers rolle ved aldersbetingede sygdomme

    DEFF Research Database (Denmark)

    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...

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

    KAUST Repository

    Burla, Romina

    2015-06-25

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

  20. Human Rap1 interacts directly with telomeric DNA and regulates TRF2 localization at the telomere.

    Science.gov (United States)

    Arat, N Özlem; Griffith, Jack D

    2012-12-07

    The TRF2-Rap1 complex suppresses non-homologous end joining and interacts with DNAPK-C to prevent end joining. We previously demonstrated that hTRF2 is a double strand telomere binding protein that forms t-loops in vitro and recognizes three- and four-way junctions independent of DNA sequence. How the DNA binding characteristics of hTRF2 to DNA is altered in the presence of hRap1 however is not known. Here we utilized EM and quantitative gel retardation to characterize the DNA binding properties of hRap1 and the TRF2-Rap1 complex. Both gel filtration chromatography and mass analysis from two-dimensional projections showed that the TRF2-Rap1 complex exists in solution and binds to DNA as a complex consisting of four monomers each of hRap1 and hTRF2. EM revealed for the first time that hRap1 binds to DNA templates in the absence of hTRF2 with a preference for double strand-single strand junctions in a sequence independent manner. When hTRF2 and hRap1 are in a complex, its affinity for ds telomeric sequences is 2-fold higher than TRF2 alone and more than 10-fold higher for telomeric 3' ends. This suggests that as hTRF2 recruits hRap1 to telomeric sequences, hRap1 alters the affinity of hTRF2 and its binding preference on telomeric DNA. Moreover, the TRF2-Rap1 complex has higher ability to re-model telomeric DNA than either component alone. This finding underlies the importance of complex formation between hRap1 and hTRF2 for telomere function and end protection.

  1. Human Rap1 Interacts Directly with Telomeric DNA and Regulates TRF2 Localization at the Telomere*

    Science.gov (United States)

    Arat, N. Özlem; Griffith, Jack D.

    2012-01-01

    The TRF2-Rap1 complex suppresses non-homologous end joining and interacts with DNAPK-C to prevent end joining. We previously demonstrated that hTRF2 is a double strand telomere binding protein that forms t-loops in vitro and recognizes three- and four-way junctions independent of DNA sequence. How the DNA binding characteristics of hTRF2 to DNA is altered in the presence of hRap1 however is not known. Here we utilized EM and quantitative gel retardation to characterize the DNA binding properties of hRap1 and the TRF2-Rap1 complex. Both gel filtration chromatography and mass analysis from two-dimensional projections showed that the TRF2-Rap1 complex exists in solution and binds to DNA as a complex consisting of four monomers each of hRap1 and hTRF2. EM revealed for the first time that hRap1 binds to DNA templates in the absence of hTRF2 with a preference for double strand-single strand junctions in a sequence independent manner. When hTRF2 and hRap1 are in a complex, its affinity for ds telomeric sequences is 2-fold higher than TRF2 alone and more than 10-fold higher for telomeric 3′ ends. This suggests that as hTRF2 recruits hRap1 to telomeric sequences, hRap1 alters the affinity of hTRF2 and its binding preference on telomeric DNA. Moreover, the TRF2-Rap1 complex has higher ability to re-model telomeric DNA than either component alone. This finding underlies the importance of complex formation between hRap1 and hTRF2 for telomere function and end protection. PMID:23086976

  2. Telomerase-Associated Protein TEP1 Is Not Essential for Telomerase Activity or Telomere Length Maintenance In Vivo

    OpenAIRE

    Liu, Yie; Snow, Bryan E.; Hande, M. Prakash; Baerlocher, Gabriela; Kickhoefer, Valerie A.; Yeung, David; Wakeham, Andrew; Itie, Annick; Siderovski, David P.; Lansdorp, Peter M.; Robinson, Murray O.; Harrington, Lea

    2000-01-01

    TEP1 is a mammalian telomerase-associated protein with similarity to the Tetrahymena telomerase protein p80. Like p80, TEP1 is associated with telomerase activity and the telomerase reverse transcriptase, and it specifically interacts with the telomerase RNA. To determine the role of mTep1 in telomerase function in vivo, we generated mouse embryonic stem (ES) cells and mice lacking mTep1. The mTep1-deficient (mTep1−/−) mice were viable and were bred for seven successive generations with no ob...

  3. High Mobility Group A2 protects cancer cells against telomere dysfunction

    Science.gov (United States)

    Natarajan, Suchitra; Begum, Farhana; Gim, Jeonga; Wark, Landon; Henderson, Dana; Davie, James R.

    2016-01-01

    The non-histone chromatin binding protein High Mobility Group AT-hook protein 2 (HMGA2) plays important roles in the repair and protection of genomic DNA in embryonic stem cells and cancer cells. Here we show that HMGA2 localizes to mammalian telomeres and enhances telomere stability in cancer cells. We present a novel interaction of HMGA2 with the key shelterin protein TRF2. We found that the linker (L1) region of HMGA2 contributes to this interaction but the ATI-L1-ATII molecular region of HMGA2 is required for strong interaction with TRF2. This interaction was independent of HMGA2 DNA-binding and did not require the TRF2 interacting partner RAP1 but involved the homodimerization and hinge regions of TRF2. HMGA2 retained TRF2 at telomeres and reduced telomere-dysfunction despite induced telomere stress. Silencing of HMGA2 resulted in (i) reduced binding of TRF2 to telomere DNA as observed by ChIP, (ii) increased telomere instability and (iii) the formation of telomere dysfunction-induced foci (TIF). This resulted in increased telomere aggregation, anaphase bridges and micronuclei. HMGA2 prevented ATM-dependent pTRF2T188 phosphorylation and attenuated signaling via the telomere specific ATM-CHK2-CDC25C DNA damage signaling axis. In summary, our data demonstrate a unique and novel role of HMGA2 in telomere protection and promoting telomere stability in cancer cells. This identifies HMGA2 as a new therapeutic target for the destabilization of telomeres in HMGA2+ cancer cells. PMID:26799419

  4. Rap1 Binds Single-stranded DNA at Telomeric Double- and Single-stranded Junctions and Competes with Cdc13 Protein*

    Science.gov (United States)

    Gustafsson, Cecilia; Rhodin Edsö, Jenny; Cohn, Marita

    2011-01-01

    The ends of eukaryotic chromosomes are protected by specialized telomere chromatin structures. Rap1 and Cdc13 are essential for the formation of functional telomere chromatin in budding yeast by binding to the double-stranded part and the single-stranded 3′ overhang, respectively. We analyzed the binding properties of Saccharomyces castellii Rap1 and Cdc13 to partially single-stranded oligonucleotides, mimicking the junction of the double- and single-stranded DNA (ds-ss junction) at telomeres. We determined the optimal and the minimal DNA setup for a simultaneous binding of Rap1 and Cdc13 at the ds-ss junction. Remarkably, Rap1 is able to bind to a partially single-stranded binding site spanning the ds-ss junction. The binding over the ds-ss junction is anchored in a single double-stranded hemi-site and is stabilized by a sequence-independent interaction of Rap1 with the single-stranded 3′ overhang. Thus, Rap1 is able to switch between a sequence-specific and a nonspecific binding mode of one hemi-site. At a ds-ss junction configuration where the two binding sites partially overlap, Rap1 and Cdc13 are competing for the binding. These results shed light on the end protection mechanisms and suggest that Rap1 and Cdc13 act together to ensure the protection of both the 3′ and the 5′ DNA ends at telomeres. PMID:22075002

  5. Human Rap1 modulates TRF2 attraction to telomeric DNA.

    Science.gov (United States)

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

    2015-03-11

    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 repair in Ku 70/80 heterodimer absence. To understand how Rap1 affects key functions of TRF2, we investigated full-length Rap1 binding to TRF2 and Rap1-TRF2 complex interactions with double-stranded DNA by quantitative biochemical approaches. We observed that Rap1 reduces the overall DNA duplex binding affinity of TRF2 but increases the selectivity of TRF2 to telomeric DNA. Additionally, we observed that Rap1 induces a partial release of TRF2 from DNA duplex. The improved TRF2 selectivity to telomeric DNA is caused by less pronounced electrostatic attractions between TRF2 and DNA in Rap1 presence. Thus, Rap1 prompts more accurate and selective TRF2 recognition of telomeric DNA and TRF2 localization on single/double-strand DNA junctions. These quantitative functional studies contribute to the understanding of the selective recognition of telomeric DNA by the whole shelterin complex. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  6. Telomeres and their possible role in chromosome stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Day, J.P.; Marder, B.A.; Morgan, W.F. (Univ. of California, San Francisco, CA (United States))

    1993-01-01

    The evidence to date generally supports the hypothesis that telomere capping makes chromosome fragments refractory to subsequent rejoining events, but this control may be somewhat relaxed after chromosome breakage. Cell survival requires that the fragments rejoin before metaphase. Unprotected ends such as those produced by DNA damage are subject to degradation, presumably by endogenous cellular exo- and endonucleases. Telomere repeat sequences may be added to broken chromosome ends to protect the ends from further degradation. That telomeric DNA does not always prevent rejoining raises interesting questions as to what constitutes capping, and how rapidly it occurs after DNA damage in relation to chromosome break rejoining. The prevention of degradation and control of rejoining may be mediated by telomere-specific binding proteins, especially the telomere terminal binding protein. Some of these proteins may be involved in scavenging telomeric DNA when the cell senses that chromosomal breaks have occurred. Although chromosome break rejoining is an efficient process in eukaryotic cells, some breaks are never rejoined and can result in terminal delections and chromatid and isochromatid deletions at metaphase. It is unclear why these breaks are not rejoined, but it may be due to one or more of the following: (1) chance: broken chromosomes are separated, do not approach sufficiently close to one another, and are consequently physically unable to rejoin; (2) a large number of added telomere repeat sequences indicating to the cell that the chromosome has an authentic telomere; (3) some other DNA modification event that protects DNA ends from degradation, e.g., folding back of DNA ends to form a hairpin, as has been implicated in VDJ recombination.

  7. Curcusone C induces telomeric DNA-damage response in cancer cells through inhibition of telomeric repeat factor 2.

    Science.gov (United States)

    Wang, Mingxue; Cao, Jiaojiao; Zhu, Jian-Yong; Qiu, Jun; Zhang, Yan; Shu, Bing; Ou, Tian-Miao; Tan, Jia-Heng; Gu, Lian-Quan; Huang, Zhi-Shu; Yin, Sheng; Li, Ding

    2017-11-01

    Telomeric repeat factor 2 (known as TRF2 or TERF2) is a key component of telomere protection protein complex named as Shelterin. TRF2 helps the folding of telomere to form T-loop structure and the suppression of ATM-dependent DNA damage response activation. TRF2 has been recognized as a potentially new therapeutic target for cancer treatment. In our routine screening of small molecule libraries, we found that Curcusone C had significant effect in disrupting the binding between TRF2 and telomeric DNA, with potent antitumor activity against cancer cells. Our result showed that Curcusone C could bind with TRF2 without binding interaction with TRF1 (telomeric repeat factor 1) although these two proteins share high sequence homology, indicating that their binding conformations and biological functions in telomere could be different. Our mechanistic studies showed that Curcusone C bound with TRF2 possibly through its DNA binding site causing blockage of its interaction with telomeric DNA. Further in cellular studies indicated that the interaction of TRF2 with Curcusone C could activate DNA-damage response, inhibit tumor cell proliferation, and cause cell cycle arrest, resulting in tumor cell apoptosis. Our studies showed that Curcusone C could become a promising lead compound for further development for cancer treatment. Here, TRF2 was firstly identified as a target of Curcusone C. It is likely that the anti-cancer activity of some other terpenes and terpenoids are related with their possible effect for telomere protection proteins. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Glyceraldehyde 3-phosphate dehydrogenase-telomere association correlates with redox status in Trypanosoma cruzi.

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    Ricardo Pariona-Llanos

    Full Text Available Glyceraldehyde 3-phosphate dehydrogenase (GAPDH is a classical metabolic enzyme involved in energy production and plays a role in additional nuclear functions, including transcriptional control, recognition of misincorporated nucleotides in DNA and maintenance of telomere structure. Here, we show that the recombinant protein T. cruzi GAPDH (rTcGAPDH binds single-stranded telomeric DNA. We demonstrate that the binding of GAPDH to telomeric DNA correlates with the balance between oxidized and reduced forms of nicotinamide adenine dinucleotides (NAD+/NADH. We observed that GAPDH-telomere association and NAD+/NADH balance changed throughout the T. cruzi life cycle. For example, in replicative epimastigote forms of T. cruzi, which show similar intracellular concentrations of NAD+ and NADH, GAPDH binds to telomeric DNA in vivo and this binding activity is inhibited by exogenous NAD+. In contrast, in the T. cruzi non-proliferative trypomastigote forms, which show higher NAD+ concentration, GAPDH was absent from telomeres. In addition, NAD+ abolishes physical interaction between recombinant GAPDH and synthetic telomere oligonucleotide in a cell free system, mimicking exogenous NAD+ that reduces GAPDH-telomere interaction in vivo. We propose that the balance in the NAD+/NADH ratio during T. cruzi life cycle homeostatically regulates GAPDH telomere association, suggesting that in trypanosomes redox status locally modulates GAPDH association with telomeric DNA.

  9. Involvement of human ORC and TRF2 in pre-replication complex assembly at telomeres.

    Science.gov (United States)

    Tatsumi, Yasutoshi; Ezura, Kai; Yoshida, Kazumasa; Yugawa, Takashi; Narisawa-Saito, Mako; Kiyono, Tohru; Ohta, Satoshi; Obuse, Chikashi; Fujita, Masatoshi

    2008-10-01

    The origin recognition complex (ORC) binds to replication origins to regulate the cell cycle-dependent assembly of pre-replication complexes (pre-RCs). We have found a novel link between pre-RC assembly regulation and telomere homeostasis in human cells. Biochemical analyses showed that human ORC binds to TRF2, a telomere sequence-binding protein that protects telomeres and functions in telomere length homeostasis, via the ORC1 subunit. Immunostaining further revealed that ORC and TRF2 partially co-localize in nuclei, whereas chromatin immunoprecipitation analyses confirmed that pre-RCs are assembled at telomeres in a cell cycle-dependent manner. Over-expression of TRF2 stimulated ORC and MCM binding to chromatin and RNAi-directed TRF2 silencing resulted in reduced ORC binding and pre-RC assembly at telomeres. As expected from previous reports, TRF2 silencing induced telomere elongation. Interestingly, ORC1 silencing by RNAi weakened the TRF2 binding as well as the pre-RC assembly at telomeres, suggesting that ORC and TRF2 interact with each other to achieve stable binding. Furthermore, ORC1 silencing also resulted in modest telomere elongation. These data suggest that ORC might be involved in telomere homeostasis in human cells.

  10. TRF1 and TRF2 binding to telomeres is modulated by nucleosomal organization.

    Science.gov (United States)

    Galati, Alessandra; Micheli, Emanuela; Alicata, Claudia; Ingegnere, Tiziano; Cicconi, Alessandro; Pusch, Miriam Caroline; Giraud-Panis, Marie-Josèphe; Gilson, Eric; Cacchione, Stefano

    2015-07-13

    The ends of eukaryotic chromosomes need to be protected from the activation of a DNA damage response that leads the cell to replicative senescence or apoptosis. In mammals, protection is accomplished by a six-factor complex named shelterin, which organizes the terminal TTAGGG repeats in a still ill-defined structure, the telomere. The stable interaction of shelterin with telomeres mainly depends on the binding of two of its components, TRF1 and TRF2, to double-stranded telomeric repeats. Tethering of TRF proteins to telomeres occurs in a chromatin environment characterized by a very compact nucleosomal organization. In this work we show that binding of TRF1 and TRF2 to telomeric sequences is modulated by the histone octamer. By means of in vitro models, we found that TRF2 binding is strongly hampered by the presence of telomeric nucleosomes, whereas TRF1 binds efficiently to telomeric DNA in a nucleosomal context and is able to remodel telomeric nucleosomal arrays. Our results indicate that the different behavior of TRF proteins partly depends on the interaction with histone tails of their divergent N-terminal domains. We propose that the interplay between the histone octamer and TRF proteins plays a role in the steps leading to telomere deprotection. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

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

    Science.gov (United States)

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

    2016-06-01

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

  12. The Analysis of Pendolino (peo Mutants Reveals Differences in the Fusigenic Potential among Drosophila Telomeres.

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    Giovanni Cenci

    2015-06-01

    Full Text Available Drosophila telomeres are sequence-independent structures that are maintained by transposition to chromosome ends of three specialized retroelements (HeT-A, TART and TAHRE; collectively designated as HTT rather than telomerase activity. Fly telomeres are protected by the terminin complex (HOAP-HipHop-Moi-Ver that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. Although all Drosophila telomeres terminate with HTT arrays and are capped by terminin, they differ in the type of subtelomeric chromatin; the Y, XR, and 4L HTT are juxtaposed to constitutive heterochromatin, while the XL, 2L, 2R, 3L and 3R HTT are linked to the TAS repetitive sequences; the 4R HTT is associated with a chromatin that has features common to both euchromatin and heterochromatin. Here we show that mutations in pendolino (peo cause telomeric fusions (TFs. The analysis of several peo mutant combinations showed that these TFs preferentially involve the Y, XR and 4th chromosome telomeres, a TF pattern never observed in the other 10 telomere-capping mutants so far characterized. peo encodes a non-terminin protein homologous to the E2 variant ubiquitin-conjugating enzymes. The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment. However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells. We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres. Alternatively, it is possible that Peo plays a dual function being independently required for DNA replication and telomere capping.

  13. The Analysis of Pendolino (peo) Mutants Reveals Differences in the Fusigenic Potential among Drosophila Telomeres.

    Science.gov (United States)

    Cenci, Giovanni; Ciapponi, Laura; Marzullo, Marta; Raffa, Grazia D; Morciano, Patrizia; Raimondo, Domenico; Burla, Romina; Saggio, Isabella; Gatti, Maurizio

    2015-06-01

    Drosophila telomeres are sequence-independent structures that are maintained by transposition to chromosome ends of three specialized retroelements (HeT-A, TART and TAHRE; collectively designated as HTT) rather than telomerase activity. Fly telomeres are protected by the terminin complex (HOAP-HipHop-Moi-Ver) that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. Although all Drosophila telomeres terminate with HTT arrays and are capped by terminin, they differ in the type of subtelomeric chromatin; the Y, XR, and 4L HTT are juxtaposed to constitutive heterochromatin, while the XL, 2L, 2R, 3L and 3R HTT are linked to the TAS repetitive sequences; the 4R HTT is associated with a chromatin that has features common to both euchromatin and heterochromatin. Here we show that mutations in pendolino (peo) cause telomeric fusions (TFs). The analysis of several peo mutant combinations showed that these TFs preferentially involve the Y, XR and 4th chromosome telomeres, a TF pattern never observed in the other 10 telomere-capping mutants so far characterized. peo encodes a non-terminin protein homologous to the E2 variant ubiquitin-conjugating enzymes. The Peo protein directly interacts with the terminin components, but peo mutations do not affect telomeric localization of HOAP, Moi, Ver and HP1a, suggesting that the peo-dependent telomere fusion phenotype is not due to loss of terminin from chromosome ends. peo mutants are also defective in DNA replication and PCNA recruitment. However, our results suggest that general defects in DNA replication are unable to induce TFs in Drosophila cells. We thus hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in heterochromatin-associated telomeres. Alternatively, it is possible that Peo plays a dual function being independently required for DNA replication and telomere capping.

  14. Molecular adaptation of telomere associated genes in mammals.

    Science.gov (United States)

    Morgan, Claire C; Mc Cartney, Ann M; Donoghue, Mark T A; Loughran, Noeleen B; Spillane, Charles; Teeling, Emma C; O'Connell, Mary J

    2013-11-15

    Placental mammals display a huge range of life history traits, including size, longevity, metabolic rate and germ line generation time. Although a number of general trends have been proposed between these traits, there are exceptions that warrant further investigation. Species such as naked mole rat, human and certain bat species all exhibit extreme longevity with respect to body size. It has long been established that telomeres and telomere maintenance have a clear role in ageing but it has not yet been established whether there is evidence for adaptation in telomere maintenance proteins that could account for increased longevity in these species. Here we carry out a molecular investigation of selective pressure variation, specifically focusing on telomere associated genes across placental mammals. In general we observe a large number of instances of positive selection acting on telomere genes. Although these signatures of selection overall are not significantly correlated with either longevity or body size we do identify positive selection in the microbat species Myotis lucifugus in functionally important regions of the telomere maintenance genes DKC1 and TERT, and in naked mole rat in the DNA repair gene BRCA1. These results demonstrate the multifarious selective pressures acting across the mammal phylogeny driving lineage-specific adaptations of telomere associated genes. Our results show that regardless of the longevity of a species, these proteins have evolved under positive selection thereby removing increased longevity as the single selective force driving this rapid rate of evolution. However, evidence of molecular adaptations specific to naked mole rat and Myotis lucifugus highlight functionally significant regions in genes that may alter the way in which telomeres are regulated and maintained in these longer-lived species.

  15. TERRA, hnRNP A1, and DNA-PKcs Interactions at Human Telomeres.

    Science.gov (United States)

    Le, Phuong N; Maranon, David G; Altina, Noelia H; Battaglia, Christine L R; Bailey, Susan M

    2013-01-01

    Maintenance of telomeres, repetitive elements at eukaryotic chromosomal termini, and the end-capping structure and function they provide, are imperative for preserving genome integrity and stability. The discovery that telomeres are transcribed into telomere repeat containing RNA (TERRA) has revolutionized our view of this repetitive, rather unappreciated region of the genome. We have previously shown that the non-homologous end-joining, shelterin associated DNA dependent protein kinase catalytic subunit (DNA-PKcs) participates in mammalian telomeric end-capping, exclusively at telomeres created by leading-strand synthesis. Here, we explore potential roles of DNA-PKcs and its phosphorylation target heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) in the localization of TERRA at human telomeres. Evaluation of co-localized foci utilizing RNA-FISH and three-dimensional (3D) reconstruction strategies provided evidence that both inhibition of DNA-PKcs kinase activity and siRNA depletion of hnRNP A1 result in accumulation of TERRA at individual telomeres; depletion of hnRNP A1 also resulted in increased frequencies of fragile telomeres. These observations are consistent with previous demonstrations that decreased levels of the nonsense RNA-mediated decay factors SMG1 and UPF1 increase TERRA at telomeres and interfere with replication of leading-strand telomeres. We propose that hTR mediated stimulation of DNA-PKcs and subsequent phosphorylation of hnRNP A1 influences the cell cycle dependent distribution of TERRA at telomeres by contributing to the removal of TERRA from telomeres, an action important for progression of S-phase, and thereby facilitating efficient telomere replication and end-capping.

  16. The DNA damage response at eroded telomeres and tethering to the nuclear pore complex

    DEFF Research Database (Denmark)

    Khadaroo, Basheer; Teixeira, M Teresa; Luciano, Pierre

    2009-01-01

    to induce the recruitment of checkpoint and recombination proteins. Notably, a DNA damage response at eroded telomeres starts many generations before senescence and is characterized by the recruitment of Cdc13 (cell division cycle 13), replication protein A, DNA damage checkpoint proteins and the DNA repair......The ends of linear eukaryotic chromosomes are protected by telomeres, which serve to ensure proper chromosome replication and to prevent spurious recombination at chromosome ends. In this study, we show by single cell analysis that in the absence of telomerase, a single short telomere is sufficient...... protein Rad52 into a single focus. Moreover, we show that eroded telomeres, although remaining at the nuclear periphery, move to the nuclear pore complex. Our results link the DNA damage response at eroded telomeres to changes in subnuclear localization and suggest the existence of collapsed replication...

  17. Replication stress as a source of telomere recombination during replicative senescence in Saccharomyces cerevisiae.

    Science.gov (United States)

    Simon, Marie-Noëlle; Churikov, Dmitri; Géli, Vincent

    2016-11-01

    Replicative senescence is triggered by short unprotected telomeres that arise in the absence of telomerase. In addition, telomeres are known as difficult regions to replicate due to their repetitive G-rich sequence prone to secondary structures and tightly bound non-histone proteins. Here we review accumulating evidence that telomerase inactivation in yeast immediately unmasks the problems associated with replication stress at telomeres. Early after telomerase inactivation, yeast cells undergo successive rounds of stochastic DNA damages and become dependent on recombination for viability long before the bulk of telomeres are getting critically short. The switch from telomerase to recombination to repair replication stress-induced damage at telomeres creates telomere instability, which may drive further genomic alterations and prepare the ground for telomerase-independent immortalization observed in yeast survivors and in 15% of human cancer. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  18. p300-mediated acetylation of TRF2 is required for maintaining functional telomeres.

    Science.gov (United States)

    Her, Yoon Ra; Chung, In Kwon

    2013-02-01

    The human telomeric protein TRF2 is required to protect chromosome ends by facilitating their organization into the protective capping structure. Post-translational modifications of TRF2 such as phosphorylation, ubiquitination, SUMOylation, methylation and poly(ADP-ribosyl)ation have been shown to play important roles in telomere function. Here we show that TRF2 specifically interacts with the histone acetyltransferase p300, and that p300 acetylates the lysine residue at position 293 of TRF2. We also report that p300-mediated acetylation stabilizes the TRF2 protein by inhibiting its ubiquitin-dependent proteolysis and is required for efficient telomere binding of TRF2. Furthermore, overexpression of the acetylation-deficient mutant, K293R, induces DNA-damage response foci at telomeres, thereby leading to induction of impaired cell growth, cellular senescence and altered cell cycle distribution. A small but significant number of metaphase chromosomes show no telomeric signals at chromatid ends, suggesting an aberrant telomere structure. These findings demonstrate that acetylation of TRF2 by p300 plays a crucial role in the maintenance of functional telomeres as well as in the regulation of the telomere-associated DNA-damage response, thus providing a new route for modulating telomere protection function.

  19. Predictors of telomere content in dragon lizards

    Science.gov (United States)

    Ballen, Cissy; Healey, Mo; Wilson, Mark; Tobler, Michael; Olsson, Mats

    2012-08-01

    Telomeres shorten as a consequence of DNA replication, in particular in cells with low production of telomerase and perhaps in response to physiological stress from exposure to reactive oxygen species, such as superoxide. This process of telomere attrition is countered by innate antioxidation, such as via the production of superoxide dismutase. We studied the inheritance of telomere length in the Australian painted dragon lizard ( Ctenophorus pictus) and the extent to which telomere length covaries with mass-corrected maternal reproductive investment, which reflects the level of circulating yolk precursor and antioxidant, vitellogenin. Our predictors of offspring telomere length explained 72 % of telomere variation (including interstitial telomeres if such are present). Maternal telomere length and reproductive investment were positively influencing offspring telomere length in our analyses, whereas flow cytometry-estimated superoxide level was negatively impacting offspring telomere length. We suggest that the effects of superoxide on hatchling telomere shortening may be partly balanced by transgenerational effects of vitellogenin antioxidation.

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

    Science.gov (United States)

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

    2011-03-24

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-09-26

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

  2. POT1-independent single-strand telomeric DNA binding activities in Brassicaceae.

    Science.gov (United States)

    Shakirov, Eugene V; McKnight, Thomas D; Shippen, Dorothy E

    2009-06-01

    Telomeres define the ends of linear eukaryotic chromosomes and are required for genome maintenance and continued cell proliferation. The extreme ends of telomeres terminate in a single-strand protrusion, termed the G-overhang, which, in vertebrates and fission yeast, is bound by evolutionarily conserved members of the POT1 (protection of telomeres) protein family. Unlike most other model organisms, the flowering plant Arabidopsis thaliana encodes two divergent POT1-like proteins. Here we show that the single-strand telomeric DNA binding activity present in A. thaliana nuclear extracts is not dependent on POT1a or POT1b proteins. Furthermore, in contrast to POT1 proteins from yeast and vertebrates, recombinant POT1a and POT1b proteins from A. thaliana, and from two additional Brassicaceae species, Arabidopsis lyrata and Brassica oleracea (cauliflower), fail to bind single-strand telomeric DNA in vitro under the conditions tested. Finally, although we detected four single-strand telomeric DNA binding activities in nuclear extracts from B. oleracea, partial purification and DNA cross-linking analysis of these complexes identified proteins that are smaller than the predicted sizes of BoPOT1a or BoPOT1b. Taken together, these data suggest that POT1 proteins are not the major single-strand telomeric DNA binding activities in A. thaliana and its close relatives, underscoring the remarkable functional divergence of POT1 proteins from plants and other eukaryotes.

  3. Differential Telomere Shortening in Blood versus Arteries in an Animal Model of Type 2 Diabetes

    Directory of Open Access Journals (Sweden)

    Samira Tajbakhsh

    2015-01-01

    Full Text Available Vascular dysfunction is an early feature of diabetic vascular disease, due to increased oxidative stress and reduced nitric oxide (NO bioavailability. This can lead to endothelial cell senescence and clinical complications such as stroke. Cells can become senescent by shortened telomeres and oxidative stress is known to accelerate telomere attrition. Sirtuin 1 (SIRT1 has been linked to vascular health by upregulating endothelial nitric oxide synthase (eNOS, suppressing oxidative stress, and attenuating telomere shortening. Accelerated leukocyte telomere attrition appears to be a feature of clinical type 2 diabetes (T2D and therefore the telomere system may be a potential therapeutic target in preventing vascular complications of T2D. However the effect of T2D on vascular telomere length is currently unknown. We hypothesized that T2D gives rise to shortened leukocyte and vascular telomeres alongside reduced vascular SIRT1 expression and increased oxidative stress. Accelerated telomere attrition was observed in circulating leukocytes, but not arteries, in T2D compared to control rats. T2D rats had blunted arterial SIRT1 and eNOS protein expression levels which were associated with reduced antioxidant defense capacity. Our findings suggest that hyperglycemia and a deficit in vascular SIRT1 per se are not sufficient to prematurely shorten vascular telomeres.

  4. TP53-dependent chromosome instability is associated with transient reductions in telomere length in immortal telomerase-positive cell lines

    Science.gov (United States)

    Schwartz, J. L.; Jordan, R.; Liber, H.; Murnane, J. P.; Evans, H. H.

    2001-01-01

    Telomere shortening in telomerase-negative somatic cells leads to the activation of the TP53 protein and the elimination of potentially unstable cells. We examined the effect of TP53 gene expression on both telomere metabolism and chromosome stability in immortal, telomerase-positive cell lines. Telomere length, telomerase activity, and chromosome instability were measured in multiple clones isolated from three related human B-lymphoblast cell lines that vary in TP53 expression; TK6 cells express wild-type TP53, WTK1 cells overexpress a mutant form of TP53, and NH32 cells express no TP53 protein. Clonal variations in both telomere length and chromosome stability were observed, and shorter telomeres were associated with higher levels of chromosome instability. The shortest telomeres were found in WTK1- and NH32-derived cells, and these cells had 5- to 10-fold higher levels of chromosome instability. The primary marker of instability was the presence of dicentric chromosomes. Aneuploidy and other stable chromosome alterations were also found in clones showing high levels of dicentrics. Polyploidy was found only in WTK1-derived cells. Both telomere length and chromosome instability fluctuated in the different cell populations with time in culture, presumably as unstable cells and cells with short telomeres were eliminated from the growing population. Our results suggest that transient reductions in telomere lengths may be common in immortal cell lines and that these alterations in telomere metabolism can have a profound effect on chromosome stability. Copyright 2000 Wiley-Liss, Inc.

  5. TRF1 and TRF2 differentially modulate Rad51-mediated telomeric and nontelomeric displacement loop formation in vitro.

    Science.gov (United States)

    Bower, Brian D; Griffith, Jack D

    2014-09-02

    A growing body of literature suggests that the homologous recombination/repair (HR) pathway cooperates with components of the shelterin complex to promote both telomere maintenance and nontelomeric HR. This may be due to the ability of both HR and shelterin proteins to promote strand invasion, wherein a single-stranded DNA (ssDNA) substrate base pairs with a homologous double-stranded DNA (dsDNA) template displacing a loop of ssDNA (D-loop). Rad51 recombinase catalyzes D-loop formation during HR, and telomere repeat binding factor 2 (TRF2) catalyzes the formation of a telomeric D-loop that stabilizes a looped structure in telomeric DNA (t-loop) that may facilitate telomere protection. We have characterized this functional interaction in vitro using a fluorescent D-loop assay measuring the incorporation of Cy3-labeled 90-nucleotide telomeric and nontelomeric substrates into telomeric and nontelomeric plasmid templates. We report that preincubation of a telomeric template with TRF2 inhibits the ability of Rad51 to promote telomeric D-loop formation upon preincubation with a telomeric substrate. This suggests Rad51 does not facilitate t-loop formation and suggests a mechanism whereby TRF2 can inhibit HR at telomeres. We also report a TRF2 mutant lacking the dsDNA binding domain promotes Rad51-mediated nontelomeric D-loop formation, possibly explaining how TRF2 promotes nontelomeric HR. Finally, we report telomere repeat binding factor 1 (TRF1) promotes Rad51-mediated telomeric D-loop formation, which may facilitate HR-mediated replication fork restart and explain why TRF1 is required for efficient telomere replication.

  6. Unprotected Drosophila melanogaster telomeres activate the spindle assembly checkpoint.

    Science.gov (United States)

    Musarò, Mariarosaria; Ciapponi, Laura; Fasulo, Barbara; Gatti, Maurizio; Cenci, Giovanni

    2008-03-01

    In both yeast and mammals, uncapped telomeres activate the DNA damage response (DDR) and undergo end-to-end fusion. Previous work has shown that the Drosophila HOAP protein, encoded by the caravaggio (cav) gene, is required to prevent telomeric fusions. Here we show that HOAP-depleted telomeres activate both the DDR and the spindle assembly checkpoint (SAC). The cell cycle arrest elicited by the DDR was alleviated by mutations in mei-41 (encoding ATR), mus304 (ATRIP), grp (Chk1) and rad50 but not by mutations in tefu (ATM). The SAC was partially overridden by mutations in zw10 (also known as mit(1)15) and bubR1, and also by mutations in mei-41, mus304, rad50, grp and tefu. As expected from SAC activation, the SAC proteins Zw10, Zwilch, BubR1 and Cenp-meta (Cenp-E) accumulated at the kinetochores of cav mutant cells. Notably, BubR1 also accumulated at cav mutant telomeres in a mei-41-, mus304-, rad50-, grp- and tefu-dependent manner. Our results collectively suggest that recruitment of BubR1 by dysfunctional telomeres inhibits Cdc20-APC function, preventing the metaphase-to-anaphase transition.

  7. Dissecting the telomere-inner nuclear membrane interface formed in meiosis.

    Science.gov (United States)

    Pendlebury, Devon F; Fujiwara, Yasuhiro; Tesmer, Valerie M; Smith, Eric M; Shibuya, Hiroki; Watanabe, Yoshinori; Nandakumar, Jayakrishnan

    2017-12-01

    Tethering telomeres to the inner nuclear membrane (INM) allows homologous chromosome pairing during meiosis. The meiosis-specific protein TERB1 binds the telomeric protein TRF1 to establish telomere-INM connectivity and is essential for mouse fertility. Here we solve the structure of the human TRF1-TERB1 interface to reveal the structural basis for telomere-INM linkage. Disruption of this interface abrogates binding and compromises telomere-INM attachment in mice. An embedded CDK-phosphorylation site within the TRF1-binding region of TERB1 provides a mechanism for cap exchange, a late-pachytene phenomenon involving the dissociation of the TRF1-TERB1 complex. Indeed, further strengthening this interaction interferes with cap exchange. Finally, our biochemical analysis implicates distinct complexes for telomere-INM tethering and chromosome-end protection during meiosis. Our studies unravel the structure, stoichiometry, and physiological implications underlying telomere-INM tethering, thereby providing unprecedented insights into the unique function of telomeres in meiosis.

  8. The Leishmania amazonensis TRF (TTAGGG repeat-binding factor homologue binds and co-localizes with telomeres

    Directory of Open Access Journals (Sweden)

    Freitas Lucio de H

    2010-05-01

    Full Text Available Abstract Background Telomeres are specialized structures at the end of chromosomes essential for maintaining genome stability and cell viability. The importance of telomeric proteins for telomere maintenance has increased our interest in the identification of homologues within the genus Leishmania. The mammalian TRF1 and TRF2 proteins, for example, bind double-stranded telomeres via a Myb-like DNA-binding domain and are involved with telomere length regulation and chromosome end protection. In addition, TRF2 can modulate the activity of several enzymes and influence the conformation of telomeric DNA. In this work, we identified and characterized a Leishmania protein (LaTRF homologous to both mammalian TRF1 and TRF2. Results LaTRF was cloned using a PCR-based strategy. ClustalW and bl2seq sequence analysis showed that LaTRF shared sequence identity with the Trypanosoma brucei TRF (TbTRF protein and had the same degree of sequence similarities with the dimerization (TRFH and the canonical DNA-binding Myb-like domains of both mammalian TRFs. LaTRF was predicted to be an 82.5 kDa protein, indicating that it is double the size of the trypanosome TRF homologues. Western blot and indirect immunofluorescence combined with fluorescence in situ hybridization showed that LaTRF, similarly to hTRF2, is a nuclear protein that also associates with parasite telomeres. Native and full length LaTRF and a mutant bearing the putative Myb-like domain expressed in bacteria bound double-stranded telomeric DNA in vitro. Chromatin immunoprecipitation showed that LaTRF interacted specifically with telomeres in vivo. Conclusion The nuclear localization of LaTRF, its association and co-localization with parasite telomeres and its high identity with TbTRF protein, support the hypothesis that LaTRF is a Leishmania telomeric protein.

  9. Creation of a novel telomere-cutting endonuclease based on the EN domain of telomere-specific non-long terminal repeat retrotransposon, TRAS1

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    Yoshitake Kazutoshi

    2010-04-01

    Full Text Available Abstract Background The ends of chromosomes, termed telomeres consist of repetitive DNA. The telomeric sequences shorten with cell division and, when telomeres are critically abbreviated, cells stop proliferating. However, in cancer cells, by the expression of telomerase which elongates telomeres, the cells can continue proliferating. Many approaches for telomere shortening have been pursued in the past, but to our knowledge, cutting telomeres in vivo has not so far been demonstrated. In addition, there is lack of information on the cellular effects of telomere shortening in human cells. Results Here, we created novel chimeric endonucleases to cut telomeres by fusing the endonuclease domain (TRAS1EN of the silkworm's telomere specific non-long terminal repeat retrotransposon TRAS1 to the human telomere-binding protein, TRF1. An in vitro assay demonstrated that the TRAS1EN-TRF1 chimeric endonucleases (T-EN and EN-T cut the human (TTAGGGn repeats specifically. The concentration of TRAS1EN-TRF1 chimeric endonucleases necessary for the cleavage of (TTAGGGn repeats was about 40-fold lower than that of TRAS1EN alone. When TRAS1EN-TRF1 endonucleases were introduced into human U2OS cancer cells using adenovirus vectors, the enzymes localized at telomeres of nuclei, cleaved and shortened the telomeric DNA by double-strand breaks. When human U2OS and HFL-1 fibroblast cells were infected with EN-T recombinant adenovirus, their cellular proliferation was suppressed for about 2 weeks after infection. In contrast, the TRAS1EN mutant (H258A chimeric endonuclease fused with TRF1 (ENmut-T did not show the suppression effect. The EN-T recombinant adenovirus induced telomere shortening in U2OS cells, activated the p53-dependent pathway and caused the senescence associated cellular responses, while the ENmut-T construct did not show such effects. Conclusions A novel TRAS1EN-TRF1 chimeric endonuclease (EN-T cuts the human telomeric repeats (TTAGGGn specifically in

  10. Platinum(II) phenanthroimidazole G-quadruplex ligand induces selective telomere shortening in A549 cancer cells.

    Science.gov (United States)

    Mancini, Johanna; Rousseau, Philippe; Castor, Katherine J; Sleiman, Hanadi F; Autexier, Chantal

    2016-02-01

    Telomere maintenance, achieved by the binding of protective shelterin capping proteins to telomeres and by either telomerase or a recombination-based alternative lengthening of telomere (ALT) mechanism, is critical for cell proliferation and survival. Extensive telomere shortening or loss of telomere integrity activates DNA damage checkpoints, leading to cell senescence or death. Although telomerase upregulation is an attractive target for anti-cancer therapy, the lag associated with telomere shortening and the potential activation of ALT pose a challenge. An alternative approach is to modify telomere interactions with binding proteins (telomere uncapping). G-quadruplex ligands stabilize structures generated from single-stranded G-rich 3'-telomere end (G-quadruplex) folding, which in principle, cannot be elongated by telomerase, thus leading to telomere shortening. Ligands can also mediate rapid anti-proliferative effects by telomere uncapping. We previously reported that the G-quadruplex ligand, phenylphenanthroimidazole ethylenediamine platinum(II) (PIP), inhibits telomerase activity in vitro[47]. In the current study, a long-term seeding assay showed that PIP significantly inhibited the seeding capacity of A549 lung cancer cells and to a lesser extent primary MRC5 fibroblast cells. Importantly, treatment with PIP caused a significant dose- and time-dependent decrease in average telomere length of A549 but not MRC5 cells. Moreover, cell cycle analysis revealed a significant increase in G1 arrest upon treatment of A549 cells, but not MRC5 cells. Both apoptosis and cellular senescence may contribute to the anti-proliferative effects of PIP. Our studies validate the development of novel and specific therapeutic ligands targeting telomeric G-quadruplex structures in cancer cells. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  11. Inheritance of telomere length in a bird.

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    Thorsten Horn

    Full Text Available Telomere dynamics are intensively studied in human ageing research and epidemiology, with many correlations reported between telomere length and age-related diseases, cancer and death. While telomere length is influenced by environmental factors there is also good evidence for a strong heritable component. In human, the mode of telomere length inheritance appears to be paternal and telomere length differs between sexes, with females having longer telomeres than males. Genetic factors, e.g. sex chromosomal inactivation, and non-genetic factors, e.g. antioxidant properties of oestrogen, have been suggested as possible explanations for these sex-specific telomere inheritance and telomere length differences. To test the influence of sex chromosomes on telomere length, we investigated inheritance and sex-specificity of telomere length in a bird species, the kakapo (Strigops habroptilus, in which females are the heterogametic sex (ZW and males are the homogametic (ZZ sex. We found that, contrary to findings in humans, telomere length was maternally inherited and also longer in males. These results argue against an effect of sex hormones on telomere length and suggest that factors associated with heterogamy may play a role in telomere inheritance and sex-specific differences in telomere length.

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

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    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.

  13. Mathematical model of alternative mechanism of telomere length maintenance

    CERN Document Server

    Kollár, Richard; Nosek, Jozef; Tomaska, Lubomir

    2014-01-01

    Biopolymer length regulation is a complex process that involves a large number of subprocesses acting simultaneously across multiple spatial and temporal scales. An illustrative example important for genomic stability is the length regulation of telomeres---nucleo-protein structures at the ends of linear chromosomes. 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 formulae f...

  14. TRF2 recruits RTEL1 to telomeres in S phase to promote t-loop unwinding.

    Science.gov (United States)

    Sarek, Grzegorz; Vannier, Jean-Baptiste; Panier, Stephanie; Petrini, John H J; Boulton, Simon J

    2015-02-19

    The helicase RTEL1 promotes t-loop unwinding and suppresses telomere fragility to maintain the integrity of vertebrate telomeres. An interaction between RTEL1 and PCNA is important to prevent telomere fragility, but how RTEL1 engages with the telomere to promote t-loop unwinding is unclear. Here, we establish that the shelterin protein TRF2 recruits RTEL1 to telomeres in S phase, which is required to prevent catastrophic t-loop processing by structure-specific nucleases. We show that the TRF2-RTEL1 interaction is mediated by a metal-coordinating C4C4 motif in RTEL1, which is compromised by the Hoyeraal-Hreidarsson syndrome (HHS) mutation, RTEL1(R1264H). Conversely, we define a TRF2(I124D) substitution mutation within the TRFH domain of TRF2, which eliminates RTEL1 binding and phenocopies the RTEL1(R1264H) mutation, giving rise to aberrant t-loop excision, telomere length heterogeneity, and loss of the telomere as a circle. These results implicate TRF2 in the recruitment of RTEL1 to facilitate t-loop disassembly at telomeres in S phase. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

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

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    Jia Zhou

    2017-08-01

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

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

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    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.

  17. Identification of New Genes that Regulate Telomerase and Telomere Length in Budding Yeast

    National Research Council Canada - National Science Library

    Pennock, Erin

    2001-01-01

    ... of telomerase to the chromosome end. The exact molecular mechanism by which Cdc13 protects the telomere has not been elucidated, although Stn1, a protein previously shown to interact with Cdc13, may contribute to end protection...

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

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    Romina Burla

    2015-06-01

    Full Text Available 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

  19. Long telomeres in blood leukocytes are associated with a high risk of ascending aortic aneurysm.

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    Tuija J Huusko

    Full Text Available Ascending aortic aneurysm is a connective tissue disorder. Even though multiple novel gene mutations have been identified, risk profiling and diagnosis before rupture still represent a challenge. There are studies demonstrating shorter telomere lengths in the blood leukocytes of abdominal aortic aneurysm patients. The aim of this study was to measure whether relative telomere lengths are changed in the blood leukocytes of ascending aortic aneurysm patients. We also studied the expression of telomerase in aortic tissue samples of ascending aortic aneurysms. Relative lengths of leukocyte telomeres were determined from blood samples of patients with ascending aortic aneurysms and compared with healthy controls. Telomerase expression, both at the level of mRNA and protein, was quantified from the aortic tissue samples. Mean relative telomere length was significantly longer in ascending aortic aneurysm blood samples compared with controls (T/S ratio 0.87 vs. 0.61, p<0.001. Expressions of telomerase mRNA and protein were elevated in the aortic aneurysm samples (p<0.05 and p<0.01. Our study reveals a significant difference in the mean length of blood leukocyte telomeres in ascending aortic aneurysm and controls. Furthermore, expression of telomerase, the main compensating factor for telomere loss, is elevated at both the mRNA and protein level in the samples of aneurysmal aorta. Further studies will be needed to confirm if this change in telomere length can serve as a tool for assessing the risk of ascending aortic aneurysm.

  20. Quantitative interaction screen of telomeric repeat-containing RNA reveals novel TERRA regulators.

    Science.gov (United States)

    Scheibe, Marion; Arnoult, Nausica; Kappei, Dennis; Buchholz, Frank; Decottignies, Anabelle; Butter, Falk; Mann, Matthias

    2013-12-01

    Telomeres are actively transcribed into telomeric repeat-containing RNA (TERRA), which has been implicated in the regulation of telomere length and heterochromatin formation. Here, we applied quantitative mass spectrometry (MS)-based proteomics to obtain a high-confidence interactome of TERRA. Using SILAC-labeled nuclear cell lysates in an RNA pull-down experiment and two different salt conditions, we distinguished 115 proteins binding specifically to TERRA out of a large set of background binders. While TERRA binders identified in two previous studies showed little overlap, using quantitative mass spectrometry we obtained many candidates reported in these two studies. To test whether novel candidates found here are involved in TERRA regulation, we performed an esiRNA-based interference analysis for 15 of them. Knockdown of 10 genes encoding candidate proteins significantly affected total cellular levels of TERRA, and RNAi of five candidates perturbed TERRA recruitment to telomeres. Notably, depletion of SRRT/ARS2, involved in miRNA processing, up-regulated both total and telomere-bound TERRA. Conversely, knockdown of MORF4L2, a component of the NuA4 histone acetyltransferase complex, reduced TERRA levels both globally and for telomere-bound TERRA. We thus identified new proteins involved in the homeostasis and telomeric abundance of TERRA, extending our knowledge of TERRA regulation.

  1. The effect of the TRF2 N-terminal and TRFH regions on telomeric G-quadruplex structures

    OpenAIRE

    Pedroso, Ilene M.; Hayward, William; Fletcher, Terace M.

    2009-01-01

    The sequence of human telomeric DNA consists of tandem repeats of 5?-d(TTAGGG)-3?. This guanine-rich DNA can form G-quadruplex secondary structures which may affect telomere maintenance. A current model for telomere protection by the telomere-binding protein, TRF2, involves the formation of a t-loop which is stabilized by a strand invasion-like reaction. This type of reaction may be affected by G-quadruplex structures. We analyzed the influence of the arginine-rich, TRF2 N-terminus (TRF2B), a...

  2. Telomere homeostasis in IUGR placentas - A review.

    Science.gov (United States)

    Biron-Shental, Tal; Sadeh-Mestechkin, Dana; Amiel, Aliza

    2016-03-01

    Telomeres are nucleoprotein structures located at the termini of chromosomes. They are essential for chromosome stability. Telomeres become shorter due to mitotic cycles and environmental factors. When telomeres are shortened and therefore dysfunctional, cellular senescence occurs and organ dysfunction might develop. During pregnancy, fetal growth restriction secondary to placental insufficiency has been linked to impaired telomere homeostasis in which telomeres are shorter, telomerase is decreased, and compensatory mechanisms of telomere capture are enhanced. These characteristics, along with increased signs of senescence, indicate telomere dysfunction in trophoblasts from placentas affected by intrauterine growth restriction (IUGR). This review summarizes the information currently available regarding telomere homeostasis in trophoblasts from human pregnancies affected by IUGR. Improved understanding of placental physiology might help in the development of treatment options for fetuses with IUGR. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Engineered telomere degradation models dyskeratosis congenita

    National Research Council Canada - National Science Library

    Hockemeyer, Dirk; Palm, Wilhelm; Wang, Richard C; Couto, Suzana S; de Lange, Titia

    2008-01-01

    .... However, mice with extensively shortened telomeres due to telomerase deficiency do not develop the characteristics of DC, raising questions about the etiology of DC and/or mouse models for human telomere dysfunction...

  4. Paternal age and telomere length in twins

    DEFF Research Database (Denmark)

    Hjelmborg, Jacob B; Dalgård, Christine; Mangino, Massimo

    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...

  5. Csm4-dependent telomere movement on nuclear envelope promotes meiotic recombination.

    Directory of Open Access Journals (Sweden)

    Hiromichi Kosaka

    2008-09-01

    Full Text Available During meiotic prophase, chromosomes display rapid movement, and their telomeres attach to the nuclear envelope and cluster to form a "chromosomal bouquet." Little is known about the roles of the chromosome movement and telomere clustering in this phase. In budding yeast, telomere clustering is promoted by a meiosis-specific, telomere-binding protein, Ndj1. Here, we show that a meiosis-specific protein, Csm4, which forms a complex with Ndj1, facilitates bouquet formation. In the absence of Csm4, Ndj1-bound telomeres tether to nuclear envelopes but do not cluster, suggesting that telomere clustering in the meiotic prophase consists of at least two distinct steps: Ndj1-dependent tethering to the nuclear envelope and Csm4-dependent clustering/movement. Similar to Ndj1, Csm4 is required for several distinct steps during meiotic recombination. Our results suggest that Csm4 promotes efficient second-end capture of a double-strand break following a homology search, as well as resolution of the double-Holliday junction during crossover formation. We propose that chromosome movement and associated telomere dynamics at the nuclear envelope promotes the completion of key biochemical steps during meiotic recombination.

  6. Telomerase inhibitor PinX1 provides a link between TRF1 and telomerase to prevent telomere elongation.

    Science.gov (United States)

    Soohoo, Christina Y; Shi, Rong; Lee, Tae Ho; Huang, Pengyu; Lu, Kun Ping; Zhou, Xiao Zhen

    2011-02-04

    Telomere maintenance is essential for protecting chromosome ends. Aberrations in telomere length have been implicated in cancer and aging. Telomere elongation by human telomerase is inhibited in cis by the telomeric protein TRF1 and its associated proteins. However, the link between TRF1 and inhibition of telomerase elongation of telomeres remains elusive because TRF1 has no direct effect on telomerase activity. We have previously identified one Pin2/TRF1-interacting protein, PinX1, that has the unique property of directly binding and inhibiting telomerase catalytic activity (Zhou, X. Z., and Lu, K. P. (2001) Cell 107, 347-359). However, nothing is known about the role of the PinX1-TRF1 interaction in the regulation of telomere maintenance. By identifying functional domains and key amino acid residues in PinX1 and TRF1 responsible for the PinX1-TRF1 interaction, we show that the TRF homology domain of TRF1 interacts with a minimal 20-amino acid sequence of PinX1 via hydrophilic and hydrophobic interactions. Significantly, either disrupting this interaction by mutating the critical Leu-291 residue in PinX1 or knocking down endogenous TRF1 by RNAi abolishes the ability of PinX1 to localize to telomeres and to inhibit telomere elongation in cells even though neither has any effect on telomerase activity per se. Thus, the telomerase inhibitor PinX1 is recruited to telomeres by TRF1 and provides a critical link between TRF1 and telomerase inhibition to prevent telomere elongation and help maintain telomere homeostasis.

  7. TRF2 promotes, remodels and protects telomeric Holliday junctions.

    Science.gov (United States)

    Poulet, Anaïs; Buisson, Rémi; Faivre-Moskalenko, Cendrine; Koelblen, Mélanie; Amiard, Simon; Montel, Fabien; Cuesta-Lopez, Santiago; Bornet, Olivier; Guerlesquin, Françoise; Godet, Thomas; Moukhtar, Julien; Argoul, Françoise; Déclais, Anne-Cécile; Lilley, David M J; Ip, Stephen C Y; West, Stephen C; Gilson, Eric; Giraud-Panis, Marie-Josèphe

    2009-03-18

    The ability of the telomeric DNA-binding protein, TRF2, to stimulate t-loop formation while preventing t-loop deletion is believed to be crucial to maintain telomere integrity in mammals. However, little is known on the molecular mechanisms behind these properties of TRF2. In this report, we show that TRF2 greatly increases the rate of Holliday junction (HJ) formation and blocks the cleavage by various types of HJ resolving activities, including the newly identified human GEN1 protein. By using potassium permanganate probing and differential scanning calorimetry, we reveal that the basic domain of TRF2 induces structural changes to the junction. We propose that TRF2 contributes to t-loop stabilisation by stimulating HJ formation and by preventing resolvase cleavage. These findings provide novel insights into the interplay between telomere protection and homologous recombination and suggest a general model in which TRF2 maintains telomere integrity by controlling the turnover of HJ at t-loops and at regressed replication forks.

  8. Telomere lengths, pulmonary fibrosis and telomerase (TERT mutations.

    Directory of Open Access Journals (Sweden)

    Alberto Diaz de Leon

    2010-05-01

    Full Text Available Telomerase is an enzyme that catalyzes the addition of nucleotides on the ends of chromosomes. Rare loss of function mutations in the gene that encodes the protein component of telomerase (TERT have been described in patients with idiopathic pulmonary fibrosis (IPF. Here we examine the telomere lengths and pulmonary fibrosis phenotype seen in multiple kindreds with heterozygous TERT mutations.We have identified 134 individuals with heterozygous TERT mutations from 21 unrelated families. Available medical records, surgical lung biopsies and radiographs were evaluated retrospectively. Genomic DNA isolated from circulating leukocytes has been used to measure telomere lengths with a quantitative PCR assay. We find that telomere lengths of TERT mutation carriers decrease in an age-dependent manner and show progressive shortening with successive generations of mutation inheritance. Family members without TERT mutations have a shorter mean telomere length than normal, demonstrating epigenetic inheritance of shortened telomere lengths in the absence of an inherited TERT mutation. Pulmonary fibrosis is an age-dependent phenotype not seen in mutation carriers less than 40 years of age but found in 60% of men 60 years or older; its development is associated with environmental exposures including cigarette smoking. A radiographic CT pattern of usual interstitial pneumonia (UIP, which is consistent with a diagnosis of IPF, is seen in 74% of cases and a pathologic pattern of UIP is seen in 86% of surgical lung biopsies. Pulmonary fibrosis associated with TERT mutations is progressive and lethal with a mean survival of 3 years after diagnosis. Overall, TERT mutation carriers demonstrate reduced life expectancy, with a mean age of death of 58 and 67 years for males and females, respectively.A subset of pulmonary fibrosis, like dyskeratosis congenita, bone marrow failure, and liver disease, represents a "telomeropathy" caused by germline mutations in telomerase

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

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    Eric Aeby

    2016-12-01

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

  10. The JIL-1 kinase affects telomere expression in the different telomere domains of Drosophila.

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    Rute Silva-Sousa

    Full Text Available In Drosophila, the non-LTR retrotransposons HeT-A, TART and TAHRE build a head-to-tail array of repetitions that constitute the telomere domain by targeted transposition at the end of the chromosome whenever needed. As a consequence, Drosophila telomeres have the peculiarity to harbor the genes in charge of telomere elongation. Understanding telomere expression is important in Drosophila since telomere homeostasis depends in part on the expression of this genomic compartment. We have recently shown that the essential kinase JIL-1 is the first positive regulator of the telomere retrotransposons. JIL-1 mediates chromatin changes at the promoter of the HeT-A retrotransposon that are necessary to obtain wild type levels of expression of these telomere transposons. With the present study, we show how JIL-1 is also needed for the expression of a reporter gene embedded in the telomere domain. Our analysis, using different reporter lines from the telomere and subtelomere domains of different chromosomes, indicates that JIL-1 likely acts protecting the telomere domain from the spreading of repressive chromatin from the adjacent subtelomere domain. Moreover, the analysis of the 4R telomere suggests a slightly different chromatin structure at this telomere. In summary, our results strongly suggest that the action of JIL-1 depends on which telomere domain, which chromosome and which promoter is embedded in the telomere chromatin.

  11. Telomere length in early life predicts lifespan.

    Science.gov (United States)

    Heidinger, Britt J; Blount, Jonathan D; Boner, Winnie; Griffiths, Kate; Metcalfe, Neil B; Monaghan, Pat

    2012-01-31

    The attrition of telomeres, the ends of eukaryote chromosomes, is thought to play an important role in cell deterioration with advancing age. The observed variation in telomere length among individuals of the same age is therefore thought to be related to variation in potential longevity. Studies of this relationship are hampered by the time scale over which individuals need to be followed, particularly in long-lived species where lifespan variation is greatest. So far, data are based either on simple comparisons of telomere length among different age classes or on individuals whose telomere length is measured at most twice and whose subsequent survival is monitored for only a short proportion of the typical lifespan. Both approaches are subject to bias. Key studies, in which telomere length is tracked from early in life, and actual lifespan recorded, have been lacking. We measured telomere length in zebra finches (n = 99) from the nestling stage and at various points thereafter, and recorded their natural lifespan (which varied from less than 1 to almost 9 y). We found telomere length at 25 d to be a very strong predictor of realized lifespan (P telomeres at all points at which they were measured. Reproduction increased adult telomere loss, but this effect appeared transient and did not influence survival. Our results provide the strongest evidence available of the relationship between telomere length and lifespan and emphasize the importance of understanding factors that determine early life telomere length.

  12. Environmental stresses disrupt telomere length homeostasis.

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    Kara A Boltz

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

  14. Shorter telomeres with high telomerase activity are associated with raised allostatic load and impoverished psychosocial resources.

    Science.gov (United States)

    Zalli, Argita; Carvalho, Livia A; Lin, Jue; Hamer, Mark; Erusalimsky, Jorge D; Blackburn, Elizabeth H; Steptoe, Andrew

    2014-03-25

    Recent work has linked psychological stress with premature cellular aging as indexed by reduced leukocyte telomere length. The combination of shorter telomeres with high telomerase activity (TA) may be indicative of active cell stress. We hypothesized that older individuals characterized by shorter telomeres with high TA in unstimulated leukocytes would show signs of high allostatic load and low levels of protective psychosocial resources. We studied 333 healthy men and women aged 54-76 y who underwent laboratory testing in which we measured cardiovascular, neuroendocrine, and inflammatory responses to standardized mental stress tasks. The tasks elicited prompt increases in blood pressure (BP), heart rate, cortisol, and mediators of inflammation and reductions in heart rate variability, returning toward baseline levels following stress. However, men having shorter telomeres with high TA showed blunted poststress recovery in systolic BP, heart rate variability, and monocyte chemoattractant protein-1, together with reduced responsivity in diastolic BP, heart rate, and cortisol, in comparison to men with longer telomeres or men with shorter telomeres and low TA. Shorter telomeres with high TA were also associated with reduced social support, lower optimism, higher hostility, and greater early life adversity. These effects were independent of age, socioeconomic status, and body mass index. We did not observe differences among older women. Our findings suggest that active cell stress is associated with impaired physiological stress responses and impoverished psychosocial resources, reflecting an integration of cellular, systemic, and psychological stress processes potentially relevant to health in older men.

  15. Exposure to oxychlordane is associated with shorter telomeres in arctic breeding kittiwakes.

    Science.gov (United States)

    Blévin, Pierre; Angelier, Frédéric; Tartu, Sabrina; Ruault, Stéphanie; Bustamante, Paco; Herzke, Dorte; Moe, Børge; Bech, Claus; Gabrielsen, Geir Wing; Bustnes, Jan Ove; Chastel, Olivier

    2016-09-01

    Telomeres are DNA-protein complexes located at the end of chromosomes, which play an important role in maintaining the genomic integrity. Telomeres shorten at each cell division and previous studies have shown that telomere length is related to health and lifespan and can be affected by a wide range of environmental factors. Among them, some persistent organic pollutants (POPs) have the potential to damage DNA. However, the effect of POPs on telomeres is poorly known for wildlife. Here, we investigated the relationships between some legacy POPs (organochlorine pesticides and polychlorobiphenyls) and telomere length in breeding adult black-legged kittiwakes (Rissa tridactyla), an arctic seabird species. Our results show that among legacy POPs, only blood concentration of oxychlordane, the major metabolite of chlordane mixture, is associated with shorter telomere length in females but not in males. This suggests that female kittiwakes could be more sensitive to oxychlordane, potentially explaining the previously reported lower survival rate in most oxychlordane-contaminated kittiwakes from the same population. This study is the first to report a significant and negative relationship between POPs and telomere length in a free-living bird and highlights sex-related susceptibility to banned pesticides. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Proteomic and microRNA data clarifying the effects of telomere shortening on cancer cells

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    Orit Uziel

    2015-03-01

    Full Text Available In a previous study, we have shown that shortening of telomeres by telomerase inhibition sensitized cancer cells to cisplatinum, slower their migration, increased DNA damage and impaired DNA repair [1]. In the following study, we present a network model combining microRNA and proteomic profiling attempting to decipher the molecular mechanism underlying the effect of shortened telomeres on the obtained phenotype of cancer cells [2]. The microRNA and proteomic data were used for a network model construction, which provided us with several nodal candidates that may potentially mediate the shortened-telomeres dependent features. These protein expressions were experimentally validated, supporting their potential central role in this system [2]. In this article, we delineate the full proteomic data and a microarray analyses performed on cells with shortened telomeres compared to their cognate parental intact telomere cells. The data is attached as excel files. In principle, clarifying the mechanism behind telomere shortened phenotype may facilitate novel therapeutics development and may also obviate the time consuming process of telomere shortening achieved by telomerase inhibition.

  17. Localization-Dependent and -Independent Roles of SLX4 in Regulating Telomeres

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    Jamie S.J. Wilson

    2013-09-01

    Full Text Available SLX4, a scaffold for structure-specific DNA repair nucleases, is important for several types of DNA repair. Many repair proteins bind to sites of DNA damage, resulting in subnuclear “foci,” but SLX4 forms foci in human cells even without DNA damage. Using several approaches, we show that most, but not all, SLX4 foci localize to telomeres in a range of human cell lines irrespective of the mechanisms used to maintain telomere length. The SLX1 Holliday-junction-processing enzyme is recruited to telomeres by SLX4, and SLX4, in turn, is recruited by a motif that binds to the shelterin subunit TRF2 directly. We also show that TRF2-dependent recruitment of SLX4 prevents telomere damage. Furthermore, SLX4 prevents telomere lengthening and fragility in a manner that appears to be independent of telomere association. These findings reveal that SLX4 plays multiple roles in regulating telomere homeostasis.

  18. Physical Activity and Telomere Biology: Exploring the Link with Aging-Related Disease Prevention

    Directory of Open Access Journals (Sweden)

    Andrew T. Ludlow

    2011-01-01

    Full Text Available Physical activity is associated with reduced risk of several age-related diseases as well as with increased longevity in both rodents and humans. Though these associations are well established, evidence of the molecular and cellular factors associated with reduced disease risk and increased longevity resulting from physical activity is sparse. A long-standing hypothesis of aging is the telomere hypothesis: as a cell divides, telomeres shorten resulting eventually in replicative senescence and an aged phenotype. Several reports have recently associated telomeres and telomere-related proteins to diseases associated with physical inactivity and aging including cardiovascular disease, insulin resistance, and hypertension. Interestingly several reports have also shown that longer telomeres are associated with higher physical activity levels, indicating a potential mechanistic link between physical activity, reduced age-related disease risk, and longevity. The primary purpose of this review is to discuss the potential importance of physical activity in telomere biology in the context of inactivity- and age-related diseases. A secondary purpose is to explore potential mechanisms and important avenues for future research in the field of telomeres and diseases associated with physical inactivity and aging.

  19. Regulation of homologous recombination at telomeres in budding yeast

    DEFF Research Database (Denmark)

    Eckert-Boulet, Nadine; Lisby, Michael

    2010-01-01

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

  20. Telomeric DNA mediates de novo PML body formation.

    Science.gov (United States)

    Brouwer, Anneke K; Schimmel, Joost; Wiegant, Joop C A G; Vertegaal, Alfred C O; Tanke, Hans J; Dirks, Roeland W

    2009-11-01

    The cell nucleus harbors a variety of different bodies that vary in number, composition, and size. Although these bodies coordinate important nuclear processes, little is known about how they are formed. Among the most intensively studied bodies in recent years is the PML body. These bodies have been implicated in gene regulation and other cellular processes and are disrupted in cells from patients suffering from acute promyelocytic leukemia. Using live cell imaging microscopy and immunofluorescence, we show in several cell types that PML bodies are formed at telomeric DNA during interphase. Recent studies revealed that both SUMO modification sites and SUMO interaction motifs in the promyelocytic leukemia (PML) protein are required for PML body formation. We show that SMC5, a component of the SUMO ligase MMS21-containing SMC5/6 complex, localizes temporarily at telomeric DNA during PML body formation, suggesting a possible role for SUMO in the formation of PML bodies at telomeric DNA. Our data identify a novel role of telomeric DNA during PML body formation.

  1. Telomeres and Telomerase in Cardiovascular Diseases

    Directory of Open Access Journals (Sweden)

    Jih-Kai Yeh

    2016-09-01

    Full Text Available Telomeres are tandem repeat DNA sequences present at the ends of each eukaryotic chromosome to stabilize the genome structure integrity. Telomere lengths progressively shorten with each cell division. Inflammation and oxidative stress, which are implicated as major mechanisms underlying cardiovascular diseases, increase the rate of telomere shortening and lead to cellular senescence. In clinical studies, cardiovascular risk factors such as smoking, obesity, sedentary lifestyle, and hypertension have been associated with short leukocyte telomere length. In addition, low telomerase activity and short leukocyte telomere length have been observed in atherosclerotic plaque and associated with plaque instability, thus stroke or acute myocardial infarction. The aging myocardium with telomere shortening and accumulation of senescent cells limits the tissue regenerative capacity, contributing to systolic or diastolic heart failure. In addition, patients with ion-channel defects might have genetic imbalance caused by oxidative stress-related accelerated telomere shortening, which may subsequently cause sudden cardiac death. Telomere length can serve as a marker for the biological status of previous cell divisions and DNA damage with inflammation and oxidative stress. It can be integrated into current risk prediction and stratification models for cardiovascular diseases and can be used in precise personalized treatments. In this review, we summarize the current understanding of telomeres and telomerase in the aging process and their association with cardiovascular diseases. In addition, we discuss therapeutic interventions targeting the telomere system in cardiovascular disease treatments.

  2. Mother–offspring and nest-mate resemblance but no heritability in early-life telomere length in white-throated dippers

    OpenAIRE

    Becker, Philipp J. J.; Reichert, Sophie; Zahn, Sandrine; Hegelbach, Johann; Massemin, Sylvie; Keller, Lukas F; Postma, Erik; Criscuolo, François

    2015-01-01

    Telomeres are protective DNA–protein complexes located at the ends of eukaryotic chromosomes, whose length has been shown to predict life-history parameters in various species. Although this suggests that telomere length is subject to natural selection, its evolutionary dynamics crucially depends on its heritability. Using pedigree data for a population of white-throated dippers (Cinclus cinclus), we test whether and how variation in early-life relative telomere length (RTL, measured as the n...

  3. PIF1 disruption or NBS1 hypomorphism does not affect chromosome healing or fusion resulting from double-strand breaks near telomeres in murine embryonic stem cells

    OpenAIRE

    Reynolds, Gloria E.; Gao, Qing; Miller, Douglas; Snow, Bryan E.; Harrington, Lea A.; Murnane, John P.

    2011-01-01

    Telomerase serves to maintain telomeric repeat sequences at the ends of chromosomes. However, telomerase can also add telomeric repeat sequences at DNA double-strand breaks (DSBs), a process called chromosome healing. Here, we employed a method of inducing DSBs near telomeres to query the role of two proteins, PIF1 and NBS1, in chromosome healing in mammalian cells. PIF1 was investigated because the PIF1 homolog in S. cerevisiae inhibits chromosome healing, as shown by a 1000-fold increase in...

  4. Yeast Interacting Proteins Database: YNL216W, YLR453C [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available nscription, depending on binding site context; also binds telomere sequences and plays a role in telomeric p...NA-binding protein involved in either activation or repression of transcription, depending on binding site context

  5. Role of TERRA in the regulation of telomere length.

    Science.gov (United States)

    Wang, Caiqin; Zhao, Li; Lu, Shiming

    2015-01-01

    Telomere dysfunction is closely associated with human diseases such as cancer and ageing. Inappropriate changes in telomere length and/or structure result in telomere dysfunction. Telomeres have been considered to be transcriptionally silent, but it was recently demonstrated that mammalian telomeres are transcribed into telomeric repeat-containing RNA (TERRA). TERRA, a long non-coding RNA, participates in the regulation of telomere length, telomerase activity and heterochromatinization. The correct regulation of telomere length may be crucial to telomeric homeostasis and functions. Here, we summarize recent advances in our understanding of the crucial role of TERRA in the maintenance of telomere length, with focus on the variety of mechanisms by which TERRA is involved in the regulation of telomere length. This review aims to enable further understanding of how TERRA-targeted drugs can target telomere-related diseases.

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    Werner syndrome is an inherited human progeriod syndrome caused by mutations in the gene encoding the Werner Syndrome protein, WRN. It has both 3'-5' DNA helicase and exonuclease activities, and is suggested to have roles in many aspects of DNA metabolism, including DNA repair and telomere...... maintenance. The DNA-PK complex also functions in both DNA double strand break repair and telomere maintenance. Interaction between WRN and the DNA-PK complex has been reported in DNA double strand break repair, but their possible cooperation at telomeres has not been reported. This study analyzes thein vitro...... D-loop model substrate. In addition, the length of telomeric G-tails decreases in DNA-PKcs knockdown cells, and this phenotype is reversed by overexpression of WRN helicase. These results suggest that WRN and DNA-PKcs may cooperatively prevent G-tail shortening in vivo....

  7. The basic N-terminal domain of TRF2 limits recombination endonuclease action at human telomeres.

    Science.gov (United States)

    Saint-Léger, Adélaïde; Koelblen, Melanie; Civitelli, Livia; Bah, Amadou; Djerbi, Nadir; Giraud-Panis, Marie-Josèphe; Londoño-Vallejo, Arturo; Ascenzioni, Fiorentina; Gilson, Eric

    2014-01-01

    The stability of mammalian telomeres depends upon TRF2, which prevents inappropriate repair and checkpoint activation. By using a plasmid integration assay in yeasts carrying humanized telomeres, we demonstrated that TRF2 possesses the intrinsic property to both stimulate initial homologous recombination events and to prevent their resolution via its basic N-terminal domain. In human cells, we further showed that this TRF2 domain prevents telomere shortening mediated by the resolvase-associated protein SLX4 as well as GEN1 and MUS81, 2 different types of endonucleases with resolvase activities. We propose that various types of resolvase activities are kept in check by the basic N-terminal domain of TRF2 in order to favor an accurate repair of the stalled forks that occur during telomere replication.

  8. ERK1/2/MAPK pathway-dependent regulation of the telomeric factor TRF2.

    Science.gov (United States)

    Picco, Vincent; Coste, Isabelle; Giraud-Panis, Marie-Josèphe; Renno, Toufic; Gilson, Eric; Pagès, Gilles

    2016-07-19

    Telomere stability is a hallmark of immortalized cells, including cancer cells. While the telomere length is maintained in most cases by the telomerase, the activity of a protein complex called Shelterin is required to protect telomeres against unsuitable activation of the DNA damage response pathway. Within this complex, telomeric repeat binding factor 2 (TRF2) plays an essential role by blocking the ataxia telangiectasia-mutated protein (ATM) signaling pathway at telomeres and preventing chromosome end fusion. We showed that TRF2 was phosphorylated in vitro and in vivo on serine 323 by extracellular signal-regulated kinase (ERK1/2) in both normal and cancer cells. Moreover, TRF2 and activated ERK1/2 unexpectedly interacted in the cytoplasm of tumor cells and human tumor tissues. The expression of non-phosphorylatable forms of TRF2 in melanoma cells induced the DNA damage response, leading to growth arrest and tumor reversion. These findings revealed that the telomere stability is under direct control of one of the major pro-oncogenic signaling pathways (RAS/RAF/MEK/ERK) via TRF2 phosphorylation.

  9. TRF2-Mediated Control of Telomere DNA Topology as a Mechanism for Chromosome-End Protection.

    Science.gov (United States)

    Benarroch-Popivker, Delphine; Pisano, Sabrina; Mendez-Bermudez, Aaron; Lototska, Liudmyla; Kaur, Parminder; Bauwens, Serge; Djerbi, Nadir; Latrick, Chrysa M; Fraisier, Vincent; Pei, Bei; Gay, Alexandre; Jaune, Emilie; Foucher, Kevin; Cherfils-Vicini, Julien; Aeby, Eric; Miron, Simona; Londoño-Vallejo, Arturo; Ye, Jing; Le Du, Marie-Hélène; Wang, Hong; Gilson, Eric; Giraud-Panis, Marie-Josèphe

    2016-01-21

    The shelterin proteins protect telomeres against activation of the DNA damage checkpoints and recombinational repair. We show here that a dimer of the shelterin subunit TRF2 wraps ∼ 90 bp of DNA through several lysine and arginine residues localized around its homodimerization domain. The expression of a wrapping-deficient TRF2 mutant, named Top-less, alters telomeric DNA topology, decreases the number of terminal loops (t-loops), and triggers the ATM checkpoint, while still protecting telomeres against non-homologous end joining (NHEJ). In Top-less cells, the protection against NHEJ is alleviated if the expression of the TRF2-interacting protein RAP1 is reduced. We conclude that a distinctive topological state of telomeric DNA, controlled by the TRF2-dependent DNA wrapping and linked to t-loop formation, inhibits both ATM activation and NHEJ. The presence of RAP1 at telomeres appears as a backup mechanism to prevent NHEJ when topology-mediated telomere protection is impaired. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Telomeric repeat-containing RNA TERRA: a noncoding RNA connecting telomere biology to genome integrity.

    Science.gov (United States)

    Cusanelli, Emilio; Chartrand, Pascal

    2015-01-01

    Telomeres are dynamic nucleoprotein structures that protect the ends of chromosomes from degradation and activation of DNA damage response. For this reason, telomeres are essential to genome integrity. Chromosome ends are enriched in heterochromatic marks and proper organization of telomeric chromatin is important to telomere stability. Despite their heterochromatic state, telomeres are transcribed giving rise to long noncoding RNAs (lncRNA) called TERRA (telomeric repeat-containing RNA). TERRA molecules play critical roles in telomere biology, including regulation of telomerase activity and heterochromatin formation at chromosome ends. Emerging evidence indicate that TERRA transcripts form DNA-RNA hybrids at chromosome ends which can promote homologous recombination among telomeres, delaying cellular senescence and sustaining genome instability. Intriguingly, TERRA RNA-telomeric DNA hybrids are involved in telomere length homeostasis of telomerase-negative cancer cells. Furthermore, TERRA transcripts play a role in the DNA damage response (DDR) triggered by dysfunctional telomeres. We discuss here recent developments on TERRA's role in telomere biology and genome integrity, and its implication in cancer.

  11. TRF2-tethered TIN2 can mediate telomere protection by TPP1/POT1.

    Science.gov (United States)

    Frescas, David; de Lange, Titia

    2014-04-01

    The shelterin protein TIN2 is required for the telomeric accumulation of TPP1/POT1 heterodimers and for the protection of telomeres by the POT1 proteins (POT1a and POT1b in the mouse). TIN2 also binds to TRF1 and TRF2, improving the telomeric localization of TRF2 and its function. Here, we ask whether TIN2 needs to interact with both TRF1 and TRF2 to mediate the telomere protection afforded by TRF2 and POT1a/b. Using a TIN2 allele deficient in TRF1 binding (TIN2-L247E), we demonstrate that TRF1 is required for optimal recruitment of TIN2 to telomeres and document phenotypes associated with the TIN2-L247E allele that are explained by insufficient TIN2 loading onto telomeres. To bypass the requirement for TRF1-dependent recruitment, we fused TIN2-L247E to the TRF2-interacting (RCT) domain of Rap1. The RCT-TIN2-L247E fusion showed improved telomeric localization and was fully functional in terms of chromosome end protection by TRF2, TPP1/POT1a, and TPP1/POT1b. These data indicate that when sufficient TIN2 is loaded onto telomeres, its interaction with TRF1 is not required to mediate the function of TRF2 and the TPP1/POT1 heterodimers. We therefore conclude that shelterin can protect chromosome ends as a TRF2-tethered TIN2/TPP1/POT1 complex that lacks a physical connection to TRF1.

  12. TERRA and the state of the telomere.

    Science.gov (United States)

    Rippe, Karsten; Luke, Brian

    2015-11-01

    Long noncoding telomeric repeat-containing RNA (TERRA) has been implicated in telomere maintenance in a telomerase-dependent and a telomerase-independent manner during replicative senescence and cancer. TERRA's proposed activities are diverse, thus making it difficult to pinpoint the critical roles that TERRA may have. We propose that TERRA orchestrates different activities at chromosome ends in a manner that depends on the state of the telomere.

  13. Evolutionary ecology of telomeres: a review.

    Science.gov (United States)

    Olsson, Mats; Wapstra, Erik; Friesen, Christopher R

    2017-10-06

    Telomere-induced selection could take place if telomere-associated disease risk shortens reproductive life span and differently reduces relative fitness among individuals. Some of these diseases first appear before reproductive senescence and could thus influence ongoing selection. We ask whether we can estimate the components of the breeder's equation for telomeres, in which the response to selection (R, by definition "evolution") is the product of ongoing selection (S) and heritability (h2 ). However, telomere inheritance is a conundrum: in quantitative genetics, traits can usually be allocated to categories with relatively high or low heritability, depending on their association with relative fitness. Telomere traits, however, show wide variation in heritability from zero to one, across taxa, gender, ethnicity, age, and disease status. In spite of this, there is divergence in telomere length among populations, supporting past and ongoing telomere evolution. Rates of telomere attrition and elongation vary among taxa with some, but not complete, taxonomic coherence. For example, telomerase is commonly referred to as "restricted to the germ line in mammals," but inbred mice and beavers have telomerase upregulation in somatic tissue, as do many ectotherms. These observations provoke a simplistic understanding of telomere evolutionary biology-clearly much is yet to be discovered. © 2017 The Authors. Annals of the New York Academy of Sciences published by Wiley Periodicals, Inc. on behalf of The New York Academy of Sciences.

  14. Leukocyte telomere dynamics in the elderly

    DEFF Research Database (Denmark)

    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......, 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 entire...

  15. yKu70/yKu80 and Rif1 Regulate Silencing Differentially at Telomeres in Candida glabrata▿ ‡

    Science.gov (United States)

    Rosas-Hernández, Lluvia L.; Juárez-Reyes, Alejandro; Arroyo-Helguera, Omar E.; De Las Peñas, Alejandro; Pan, Shih-Jung; Cormack, Brendan P.; Castaño, Irene

    2008-01-01

    Candida glabrata, a common opportunistic fungal pathogen, adheres efficiently to mammalian epithelial cells in culture. This interaction in vitro depends mainly on the adhesin Epa1, one of a large family of cell wall proteins. Most of the EPA genes are located in subtelomeric regions, where they are transcriptionally repressed by silencing. In order to better characterize the transcriptional regulation of the EPA family, we have assessed the importance of C. glabrata orthologues of known regulators of subtelomeric silencing in Saccharomyces cerevisiae. To this end, we used a series of strains containing insertions of the reporter URA3 gene within different intergenic regions throughout four telomeres of C. glabrata. Using these reporter strains, we have assessed the roles of SIR2, SIR3, SIR4, HDF1 (yKu70), HDF2 (yKu80), and RIF1 in mediating silencing at four C. glabrata telomeres. We found that, whereas the SIR proteins are absolutely required for silencing of the reporter genes and the native subtelomeric EPA genes, the Rif1 and the Ku proteins regulate silencing at only a subset of the analyzed telomeres. We also mapped a cis element adjacent to the EPA3 locus that can silence a reporter gene when placed at a distance of 31 kb from the telomere. Our data show that silencing of the C. glabrata telomeres varies from telomere to telomere. In addition, recruitment of silencing proteins to the subtelomeres is likely, for certain telomeres, to depend both on the telomeric repeats and on particular discrete silencing elements. PMID:18836091

  16. Plastic roles of phenylalanine and tyrosine residues of TLS/FUS in complex formation with the G-quadruplexes of telomeric DNA and TERRA.

    Science.gov (United States)

    Kondo, Keiko; Mashima, Tsukasa; Oyoshi, Takanori; Yagi, Ryota; Kurokawa, Riki; Kobayashi, Naohiro; Nagata, Takashi; Katahira, Masato

    2018-02-12

    The length of a telomere is regulated via elongation and shortening processes. Telomeric DNA and telomeric repeat-containing RNA (TERRA), which both contain G-rich repeated sequences, form G-quadruplex structures. Previously, translocated in liposarcoma (TLS) protein, also known as fused in sarcoma (FUS) protein, was found to form a ternary complex with the G-quadruplex structures of telomeric DNA and TERRA. We then showed that the third RGG motif of TLS, the RGG3 domain, is responsible for the complex formation. However, the structural basis for their binding remains obscure. Here, NMR-based binding assaying revealed the interactions in the binary and ternary complexes of RGG3 with telomeric DNA or/and TERRA. In the ternary complex, tyrosine bound exclusively to TERRA, while phenylalanine bound exclusively to telomeric DNA. Thus, tyrosine and phenylalanine each play a central role in the recognition of TERRA and telomeric DNA, respectively. Surprisingly in the binary complexes, RGG3 used both tyrosine and phenylalanine residues to bind to either TERRA or telomeric DNA. We propose that the plastic roles of tyrosine and phenylalanine are important for RGG3 to efficiently form the ternary complex, and thereby regulate the telomere shortening.

  17. XPF with mutations in its conserved nuclease domain is defective in DNA repair but functions in TRF2-mediated telomere shortening.

    Science.gov (United States)

    Wu, Yili; Zacal, Natalie J; Rainbow, Andrew J; Zhu, Xu-Dong

    2007-02-04

    TRF2, a telomere-binding protein, is a crucial player in telomere length maintenance. Overexpression of TRF2 results in telomere shortening in both normal primary fibroblasts and telomerase-positive cancer cells. TRF2 is found to be associated with XPF-ERCC1, a structure-specific endonuclease involved in nucleotide excision repair, crosslink repair and DNA recombination. XPF-ERCC1 is implicated in TRF2-dependent telomere loss in mouse keratinocytes, however, whether XPF-ERCC1 and its nuclease activity are required for TRF2-mediated telomere shortening in human cells is unknown. Here we report that TRF2-induced telomere shortening is abrogated in human cells deficient in XPF, demonstrating that XPF-ERCC1 is required for TRF2-promoted telomere shortening. To further understand the role of XPF in TRF2-dependent telomere shortening, we generated constructs containing either wild type XPF or mutant XPF proteins carrying amino acid substitutions in its conserved nuclease domain. We show that wild type XPF can complement XPF-deficient cells for repair of UV-induced DNA damage whereas the nuclease-inactive XPF proteins fail to do so, indicating that the nuclease activity of XPF is essential for nucleotide excision repair. In contrast, both wild type XPF and nuclease-inactive XPF proteins, when expressed in XPF-deficient cells, are able to rescue TRF2-mediated telomere shortening. Thus, our results suggest that the function of XPF in TRF2-mediated telomere shortening is conserved between mouse and human. Furthermore, our findings reveal an unanticipated nuclease-independent function of XPF in TRF2-mediated telomere shortening.

  18. TOR regulates cell death induced by telomere dysfunction in budding yeast.

    Directory of Open Access Journals (Sweden)

    Haiyan Qi

    Full Text Available Telomere dysfunction is known to induce growth arrest (senescence and cell death. However, the regulation of the senescence-death process is poorly understood. Here using a yeast dysfunctional telomere model cdc13-1, which carries a temperature sensitive-mutant telomere binding protein Cdc13p, we demonstrate that inhibition of TOR (Target of Rapamycin, a central regulator of nutrient pathways for cell growth, prevents cell death, but not growth arrest, induced by inactivation of Cdc13-1p. This function of TOR is novel and separable from its G1 inhibition function, and not associated with alterations in the telomere length, the amount of G-tails, and the telomere position effect (TPE in cdc13-1 cells. Furthermore, antioxidants were also shown to prevent cell death initiated by inactivation of cdc13-1. Moreover, inhibition of TOR was also shown to prevent cell death induced by inactivation of telomerase in an est1 mutant. Interestingly, rapamycin did not prevent cell death induced by DNA damaging agents such as etoposide and UV. In the aggregate, our results suggest that the TOR signaling pathway is specifically involved in the regulation of cell death initiated by telomere dysfunction.

  19. Evolution of Arabidopsis protection of telomeres 1 alters nucleic acid recognition and telomerase regulation.

    Science.gov (United States)

    Arora, Amit; Beilstein, Mark A; Shippen, Dorothy E

    2016-11-16

    Protection of telomeres (POT1) binds chromosome ends, recognizing single-strand telomeric DNA via two oligonucleotide/oligosaccharide binding folds (OB-folds). The Arabidopsis thaliana POT1a and POT1b paralogs are atypical: they do not exhibit telomeric DNA binding, and they have opposing roles in regulating telomerase activity. AtPOT1a stimulates repeat addition processivity of the canonical telomerase enzyme, while AtPOT1b interacts with a regulatory lncRNA that represses telomerase activity. Here, we show that OB1 of POT1a, but not POT1b, has an intrinsic affinity for telomeric DNA. DNA binding was dependent upon a highly conserved Phe residue (F65) that in human POT1 directly contacts telomeric DNA. F65A mutation of POT1a OB1 abolished DNA binding and diminished telomerase repeat addition processivity. Conversely, AtPOT1b and other POT1b homologs from Brassicaceae and its sister family, Cleomaceae, naturally bear a non-aromatic amino acid at this position. By swapping Val (V63) with Phe, AtPOT1b OB1 gained the capacity to bind telomeric DNA and to stimulate telomerase repeat addition processivity. We conclude that, in the context of DNA binding, variation at a single amino acid position promotes divergence of the AtPOT1b paralog from the ancestral POT1 protein. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  20. Ontogeny of Unstable Chromosomes Generated by Telomere Error in Budding Yeast.

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    Tracey Beyer

    2016-10-01

    Full Text Available DNA replication errors at certain sites in the genome initiate chromosome instability that ultimately leads to stable genomic rearrangements. Where instability begins is often unclear. And, early instability may form unstable chromosome intermediates whose transient nature also hinders mechanistic understanding. We report here a budding yeast model that reveals the genetic ontogeny of genome rearrangements, from initial replication error to unstable chromosome formation to their resolution. Remarkably, the initial error often arises in or near the telomere, and frequently forms unstable chromosomes. Early unstable chromosomes may then resolve to an internal "collection site" where a dicentric forms and resolves to an isochromosome (other outcomes are possible at each step. The initial telomere-proximal unstable chromosome is increased in mutants in telomerase subunits, Tel1, and even Rad9, with no known telomere-specific function. Defects in Tel1 and in Rrm3, a checkpoint protein kinase with a role in telomere maintenance and a DNA helicase, respectively, synergize dramatically to generate unstable chromosomes, further illustrating the consequence of replication error in the telomere. Collectively, our results suggest telomeric replication errors may be a common cause of seemingly unrelated genomic rearrangements located hundreds of kilobases away.

  1. Mir-23a induces telomere dysfunction and cellular senescence by inhibiting TRF2 expression.

    Science.gov (United States)

    Luo, Zhenhua; Feng, Xuyang; Wang, Haoli; Xu, Weiyi; Zhao, Yong; Ma, Wenbin; Jiang, Songshan; Liu, Dan; Huang, Junjiu; Songyang, Zhou

    2015-06-01

    Telomeric repeat binding factor 2 (TRF2) is essential for telomere maintenance and has been implicated in DNA damage response and aging. Telomere dysfunction induced by TRF2 inhibition can accelerate cellular senescence in human fibroblasts. While previous work has demonstrated that a variety of factors can regulate TRF2 expression transcriptionally and post-translationally, whether microRNAs (miRNAs) also participate in post-transcriptionally modulating TRF2 levels remains largely unknown. To better understand the regulatory pathways that control TRF2, we carried out a large-scale luciferase reporter screen using a miRNA expression library and identified four miRNAs that could target human TRF2 and significantly reduce the level of endogenous TRF2 proteins. In particular, our data revealed that miR-23a could directly target the 3' untranslated region (3'UTR) of TRF2. Overexpression of miR-23a not only reduced telomere-bound TRF2 and increased telomere dysfunction-induced foci (TIFs), but also accelerated senescence of human fibroblast cells, which could be rescued by ectopically expressed TRF2. Our findings demonstrate that TRF2 is a specific target of miR-23a, and uncover a previously unknown role for miR-23a in telomere regulation and cellular senescence. © 2015 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  2. MST-312 Alters Telomere Dynamics, Gene Expression Profiles and Growth in Human Breast Cancer Cells.

    Science.gov (United States)

    Gurung, Resham Lal; Lim, Shi Ni; Low, Grace Kah Mun; Hande, M Prakash

    2014-01-01

    Targeting telomerase is a potential cancer management strategy given that it allows unlimited cellular replication in the majority of cancers. Dysfunctional telomeres are recognized as double-strand breaks. However, the status of DNA repair response pathways following telomerase inhibition is not well understood in human breast cancer cells. Here, we evaluated the effects of MST-312, a chemically modified derivative from tea catechin, epigallocatechin gallate, on telomere dynamics and DNA damage gene expression in breast cancer cells. Breast cancer cells MCF-7 and MDA-MB-231 were treated with MST-312, and telomere-telomerase homeostasis, induced DNA damage and gene expression profiling were analyzed. MST-312 decreased telomerase activity and induced telomere dysfunction and growth arrest in breast cancer cells with more profound effects in MDA-MB-231 than in MCF-7 cells. Consistent with these data, the telomere-protective protein TRF2 was downregulated in MDA-MB-231 cells. MST-312 induced DNA damage at telomeres accompanied by reduced expression of DNA damage-related genes ATM and RAD50. Co-treatment with MST-312 and the poly(ADP-ribose) polymerase 1 (PARP-1) inhibitor PJ-34 further enhanced growth reduction as compared to single treatment with MST-312 or PJ-34. Our work demonstrates potential importance for the establishment of antitelomerase cancer therapy using MST-312 along with PARP-1 inhibition in breast cancer therapy. © 2015 S. Karger AG, Basel.

  3. Ontogeny of Unstable Chromosomes Generated by Telomere Error in Budding Yeast

    Science.gov (United States)

    Weinert, Ted

    2016-01-01

    DNA replication errors at certain sites in the genome initiate chromosome instability that ultimately leads to stable genomic rearrangements. Where instability begins is often unclear. And, early instability may form unstable chromosome intermediates whose transient nature also hinders mechanistic understanding. We report here a budding yeast model that reveals the genetic ontogeny of genome rearrangements, from initial replication error to unstable chromosome formation to their resolution. Remarkably, the initial error often arises in or near the telomere, and frequently forms unstable chromosomes. Early unstable chromosomes may then resolve to an internal "collection site" where a dicentric forms and resolves to an isochromosome (other outcomes are possible at each step). The initial telomere-proximal unstable chromosome is increased in mutants in telomerase subunits, Tel1, and even Rad9, with no known telomere-specific function. Defects in Tel1 and in Rrm3, a checkpoint protein kinase with a role in telomere maintenance and a DNA helicase, respectively, synergize dramatically to generate unstable chromosomes, further illustrating the consequence of replication error in the telomere. Collectively, our results suggest telomeric replication errors may be a common cause of seemingly unrelated genomic rearrangements located hundreds of kilobases away. PMID:27716774

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

    Directory of Open Access Journals (Sweden)

    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.

  5. Augmented telomerase activity, reduced telomere length and the presence of alternative lengthening of telomere in renal cell carcinoma: plausible predictive and diagnostic markers.

    Science.gov (United States)

    Pal, Deeksha; Sharma, Ujjawal; Khajuria, Ragini; Singh, Shrawan Kumar; Kakkar, Nandita; Prasad, Rajendra

    2015-05-15

    In this study, we analyzed 100 cases of renal cell carcinoma (RCC) for telomerase activity, telomere length and alternative lengthening of telomeres (ALT) using the TRAP assay, TeloTTAGGG assay kit and immunohistochemical analysis of ALT associated promyelocytic leukemia (PML) bodies respectively. A significantly higher (P=0.000) telomerase activity was observed in 81 cases of RCC which was correlated with clinicopathological features of tumor for instance, stage (P=0.008) and grades (P=0.000) but not with the subtypes of RCC (P = 0.355). Notwithstanding, no correlation was found between telomerase activity and subtypes of RCC. Strikingly, the telomere length was found to be significantly shorter in RCC (P=0.000) to that of corresponding normal renal tissues and it is well correlated with grades (P=0.016) but not with stages (P=0.202) and subtypes (P=0.669) of RCC. In this study, telomere length was also negatively correlated with the age of patients (r(2)=0.528; P=0.000) which supports the notion that it could be used as a marker for biological aging. ALT associated PML bodies containing PML protein was found in telomerase negative cases of RCC. It suggests the presence of an ALT pathway mechanism to maintain the telomere length in telomerase negative RCC tissues which was associated with high stages of RCC, suggesting a prevalent mechanism for telomere maintenance in high stages. In conclusion, the telomerase activity and telomere length can be used as a diagnostic as well as a predictive marker in RCC. The prevalence of ALT mechanism in high stages of RCC is warranted for the development of anti-ALT inhibitors along with telomerase inhibitor against RCC as a therapeutic approach. Copyright © 2015 Elsevier B.V. All rights reserved.

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

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    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.

  7. Dual roles of TRF1 in tethering telomeres to the nuclear envelope and protecting them from fusion during meiosis.

    Science.gov (United States)

    Wang, Lina; Tu, Zhaowei; Liu, Chao; Liu, Hongbin; Kaldis, Philipp; Chen, Zijiang; Li, Wei

    2018-01-08

    Telomeres integrity is indispensable for chromosomal stability by preventing chromosome erosion and end-to-end fusions. During meiosis, telomeres attach to the inner nuclear envelope and cluster into a highly crowded microenvironment at the bouquet stage, which requires specific mechanisms to protect the telomeres from fusion. Here, we demonstrate that germ cell-specific knockout of a shelterin complex subunit, Trf1, results in arrest of spermatocytes at two different stages. The obliterated telomere-nuclear envelope attachment in Trf1-deficient spermatocytes impairs homologue synapsis and recombination, resulting in a pachytene-like arrest, while the meiotic division arrest might stem from chromosome end-to-end fusion due to the failure of recruiting meiosis specific telomere associated proteins. Further investigations uncovered that TRF1 could directly interact with Speedy A, and Speedy A might work as a scaffold protein to further recruit Cdk2, thus protecting telomeres from fusion at this stage. Together, our results reveal a novel mechanism of TRF1, Speedy A, and Cdk2 in protecting telomere from fusion in a highly crowded microenvironment during meiosis.

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

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    Kamal Ahmed

    2011-04-01

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

  9. Problem-Solving Test: Telomere Replication

    Science.gov (United States)

    Szeberenyi, Jozsef

    2010-01-01

    The Nobel Prize in Physiology or Medicine in 2009 was awarded to Elizabeth H. Blackburn, Carol W. Greider, and Jack W. Szostak for the discovery of "how chromosomes are protected by telomeres and the enzyme telomerase." The discovery has important implications in the processes of cellular aging and carcinogenesis. Telomeres are satellite DNA…

  10. Telomere biology in healthy aging and disease

    NARCIS (Netherlands)

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

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

  11. Telomeres and telomerase in prostate cancer development and therapy.

    Science.gov (United States)

    Graham, Mindy Kim; Meeker, Alan

    2017-10-01

    Aberrations in telomere biology are among the earliest events in prostate cancer tumorigenesis and continue during tumour progression. Substantial telomere shortening occurs in prostate cancer cells and high-grade prostatic intraepithelial neoplasia. Not all mechanisms of telomere shortening are understood, but oxidative stress from local inflammation might accelerate prostatic telomere loss. Critically short telomeres can drive the accumulation of tumour-promoting genomic alterations; however, continued telomere erosion is unsustainable and must be mitigated to ensure cancer cell survival and unlimited replication potential. Prostate cancers predominantly maintain telomeres by activating telomerase, but alternative mechanisms of telomere extension can occur in metastatic disease. Telomerase activity and telomere length assessment might be useful in prostate cancer diagnosis and prognosis. Telomere shortening in normal stromal cells has been associated with prostate cancer, whereas variable telomere lengths in prostate cancer cells and telomere shortening in cancer-associated stromal cells correlated with lethal disease. Single-agent telomerase-targeted treatments for solid cancers were ineffective in clinical trials but have not been investigated in prostate cancer and might be useful in combination with established regimens. Telomere-directed strategies have not been explored as extensively. Telomere deprotection strategies have the advantage of being effective in both telomerase-dependent and telomerase-independent cancers. Disruption of androgen receptor function in prostate cancer cells results in telomere dysfunction, indicating telomeres and telomerase as potential therapeutic targets in prostate cancer.

  12. Telomere shortening exposes functions for the mouse Werner and Bloom syndrome genes.

    Science.gov (United States)

    Du, Xiaobing; Shen, Johnny; Kugan, Nishan; Furth, Emma E; Lombard, David B; Cheung, Catherine; Pak, Sally; Luo, Guangbin; Pignolo, Robert J; DePinho, Ronald A; Guarente, Leonard; Johnson, F Brad

    2004-10-01

    The Werner and Bloom syndromes are caused by loss-of-function mutations in WRN and BLM, respectively, which encode the RecQ family DNA helicases WRN and BLM, respectively. Persons with Werner syndrome displays premature aging of the skin, vasculature, reproductive system, and bone, and those with Bloom syndrome display more limited features of aging, including premature menopause; both syndromes involve genome instability and increased cancer. The proteins participate in recombinational repair of stalled replication forks or DNA breaks, but the precise functions of the proteins that prevent rapid aging are unknown. Accumulating evidence points to telomeres as targets of WRN and BLM, but the importance in vivo of the proteins in telomere biology has not been tested. We show that Wrn and Blm mutations each accentuate pathology in later-generation mice lacking the telomerase RNA template Terc, including acceleration of phenotypes characteristic of latest-generation Terc mutants. Furthermore, pathology not observed in Terc mutants but similar to that observed in Werner syndrome and Bloom syndrome, such as bone loss, was observed. The pathology was accompanied by enhanced telomere dysfunction, including end-to-end chromosome fusions and greater loss of telomere repeat DNA compared with Terc mutants. These findings indicate that telomere dysfunction may contribute to the pathogenesis of Werner syndrome and Bloom syndrome.

  13. Telomestatin-induced telomere uncapping is modulated by POT1 through G-overhang extension in HT1080 human tumor cells.

    Science.gov (United States)

    Gomez, Dennis; Wenner, Thomas; Brassart, Bertrand; Douarre, Céline; O'Donohue, Marie-Françoise; El Khoury, Victoria; Shin-Ya, Kazuo; Morjani, Hamid; Trentesaux, Chantal; Riou, Jean-François

    2006-12-15

    Telomestatin is a potent G-quadruplex ligand that interacts with the 3' telomeric overhang, leading to its degradation, and induces a delayed senescence and apoptosis of cancer cells. POT1 and TRF2 were recently identified as specific telomere-binding proteins involved in telomere capping and t-loop maintenance and whose interaction with telomeres is modulated by telomestatin. We show here that the treatment of HT1080 human tumor cells by telomestatin induces a rapid decrease of the telomeric G-overhang and of the double-stranded telomeric repeats. Telomestatin treatment also provokes a strong decrease of POT1 and TRF2 from their telomere sites, suggesting that the ligand triggers the uncapping of the telomere ends. The effect of the ligand is associated with an increase of the gamma-H2AX foci, one part of them colocalizing at telomeres, thus indicating the occurrence of a DNA damage response at the telomere, but also the presence of additional DNA targets for telomestatin. Interestingly, the expression of GFP-POT1 in HT1080 cells increases both telomere and G-overhang length. As compared with HT1080 cells, HT1080GFP-POT1 cells presented a resistance to telomestatin treatment characterized by a protection to the telomestatin-induced growth inhibition and the G-overhang shortening. This protection is related to the initial G-overhang length rather than to its degradation rate and is overcome by increased telomestatin concentration. Altogether these results suggest that telomestatin induced a telomere dysfunction in which G-overhang length and POT1 level are important factors but also suggest the presence of additional DNA sites of action for the ligand.

  14. Telomeric D-loops containing 8-oxo-2'-deoxyguanosine are preferred substrates for Werner and Bloom syndrome helicases and are bound by POT1.

    Science.gov (United States)

    Ghosh, Avik; Rossi, Marie L; Aulds, Jason; Croteau, Deborah; Bohr, Vilhelm A

    2009-11-06

    8-Oxo-2'-deoxyguanosine (8-oxodG) is one of the most important oxidative DNA lesions, and G-rich telomeric DNA is especially susceptible to oxidative DNA damage. RecQ helicases WRN and BLM and telomere-binding protein POT1 are thought to play roles in telomere maintenance. This study examines the ability of WRN, BLM, and RecQ5 to unwind and POT1 to bind telomeric D-loops containing 8-oxodG. The results demonstrate that WRN and BLM preferentially unwind telomeric D-loops containing 8-oxodG and that POT1 binds with higher affinity to telomeric D-loops with 8-oxodG but shows no preference for telomeric single-stranded DNA with 8-oxodG. We speculate that telomeric D-loops with 8-oxodG may have a greater tendency to form G-quadruplex DNA structures than telomeric DNA lacking 8-oxodG.

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

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    Eva-Maria Holstein

    2017-07-01

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

  16. Synaptonemal complex extension from clustered telomeres mediates full-length chromosome pairing in Schmidtea mediterranea.

    Science.gov (United States)

    Xiang, Youbin; Miller, Danny E; Ross, Eric J; Sánchez Alvarado, Alejandro; Hawley, R Scott

    2014-12-02

    In the 1920s, József Gelei proposed that chromosome pairing in flatworms resulted from the formation of a telomere bouquet followed by the extension of synapsis from telomeres at the base of the bouquet, thus facilitating homolog pairing in a processive manner. A modern interpretation of Gelei's model postulates that the synaptonemal complex (SC) is nucleated close to the telomeres and then extends progressively along the full length of chromosome arms. We used the easily visible meiotic chromosomes, a well-characterized genome, and RNAi in the sexual biotype of the planarian Schmidtea mediterranea to test that hypothesis. By identifying and characterizing S. mediterranea homologs of genes encoding synaptonemal complex protein 1 (SYCP1), the topoisomerase-like protein SPO11, and RAD51, a key player in homologous recombination, we confirmed that SC formation begins near the telomeres and progresses along chromosome arms during zygotene. Although distal regions pair at the time of bouquet formation, pairing of a unique interstitial locus is not observed until the formation of full-length SC at pachytene. Moreover, neither full extension of the SC nor homologous pairing is dependent on the formation of double-strand breaks. These findings validate Gelei's speculation that full-length pairing of homologous chromosomes is mediated by the extension of the SC formed near the telomeres. S. mediterranea thus becomes the first organism described (to our knowledge) that forms a canonical telomere bouquet but does not require double-strand breaks for synapsis between homologous chromosomes. However, the initiation of SC formation at the base of the telomere bouquet, which then is followed by full-length homologous pairing in planarian spermatocytes, is not observed in other species and may not be conserved.

  17. Telomeres and telomerase in prostate cancer development and therapy

    OpenAIRE

    Graham, Mindy Kim; Meeker, Alan

    2017-01-01

    Aberrations in telomere biology are among the earliest events in prostate cancer tumorigenesis and continue during tumour progression. Substantial telomere shortening occurs in prostate cancer cells and high-grade prostatic intraepithelial neoplasia. Not all mechanisms of telomere shortening are understood, but oxidative stress from local inflammation might accelerate prostatic telomere loss. Critically short telomeres can drive the accumulation of tumour-promoting genomic alterations; howeve...

  18. The differential processing of telomeres in response to increased telomeric transcription and RNA-DNA hybrid accumulation.

    Science.gov (United States)

    Balk, Bettina; Dees, Martina; Bender, Katharina; Luke, Brian

    2014-01-01

    Telomeres are protective nucleoprotein structures at the ends of eukaryotic chromosomes. Despite the heterochromatic state of telomeres they are transcribed, generating non-coding telomeric repeat-containing RNA (TERRA). Strongly induced TERRA transcription has been shown to cause telomere shortening and accelerated senescence in the absence of both telomerase and homology-directed repair (HDR). Moreover, it has recently been demonstrated that TERRA forms RNA-DNA hybrids at chromosome ends. The accumulation of RNA-DNA hybrids at telomeres also leads to rapid senescence and telomere loss in the absence of telomerase and HDR. Conversely, in the presence of HDR, telomeric RNA-DNA hybrid accumulation and increased telomere transcription promote telomere recombination, and hence, delayed senescence. Here, we demonstrate that despite these similar phenotypic outcomes, telomeres that are highly transcribed are not processed in the same manner as those that accumulate RNA-DNA hybrids.

  19. Protection of Arabidopsis Blunt-Ended Telomeres Is Mediated by a Physical Association with the Ku Heterodimer.

    Science.gov (United States)

    Valuchova, Sona; Fulnecek, Jaroslav; Prokop, Zbynek; Stolt-Bergner, Peggy; Janouskova, Eliska; Hofr, Ctirad; Riha, Karel

    2017-06-01

    Telomeres form specialized chromatin that protects natural chromosome termini from being recognized as DNA double-strand breaks. Plants possess unusual blunt-ended telomeres that are unable to form t-loops or complex with single-strand DNA binding proteins, raising the question of the mechanism behind their protection. We have previously suggested that blunt-ended telomeres in Arabidopsis thaliana are protected by Ku, a DNA repair factor with a high affinity for DNA ends. In nonhomologous end joining, Ku loads onto broken DNA via a channel consisting of positively charged amino acids. Here, we demonstrate that while association of Ku with plant telomeres also depends on this channel, Ku's requirements for DNA binding differ between DNA repair and telomere protection. We show that a Ku complex proficient in DNA loading but impaired in translocation along DNA is able to protect blunt-ended telomeres but is deficient in DNA repair. This suggests that Ku physically sequesters blunt-ended telomeres within its DNA binding channel, shielding them from other DNA repair machineries. © 2017 American Society of Plant Biologists. All rights reserved.

  20. Automated nuclear analysis of Leishmania major telomeric clusters reveals changes in their organization during the parasite's life cycle.

    Directory of Open Access Journals (Sweden)

    Fernando de M Dossin

    Full Text Available Parasite virulence genes are usually associated with telomeres. The clustering of the telomeres, together with their particular spatial distribution in the nucleus of human parasites such as Plasmodium falciparum and Trypanosoma brucei, has been suggested to play a role in facilitating ectopic recombination and in the emergence of new antigenic variants. Leishmania parasites, as well as other trypanosomes, have unusual gene expression characteristics, such as polycistronic and constitutive transcription of protein-coding genes. Leishmania subtelomeric regions are even more unique because unlike these regions in other trypanosomes they are devoid of virulence genes. Given these peculiarities of Leishmania, we sought to investigate how telomeres are organized in the nucleus of Leishmania major parasites at both the human and insect stages of their life cycle. We developed a new automated and precise method for identifying telomere position in the three-dimensional space of the nucleus, and we found that the telomeres are organized in clusters present in similar numbers in both the human and insect stages. While the number of clusters remained the same, their distribution differed between the two stages. The telomeric clusters were found more concentrated near the center of the nucleus in the human stage than in the insect stage suggesting reorganization during the parasite's differentiation process between the two hosts. These data provide the first 3D analysis of Leishmania telomere organization. The possible biological implications of these findings are discussed.

  1. Telomere Length in Elite Athletes.

    Science.gov (United States)

    Muniesa, Carlos A; Verde, Zoraida; Diaz-Ureña, Germán; Santiago, Catalina; Gutiérrez, Fernando; Díaz, Enrique; Gómez-Gallego, Félix; Pareja-Galeano, Helios; Soares-Miranda, Luisa; Lucia, Alejandro

    2017-08-01

    Growing evidence suggests that regular moderate-intensity physical activity is associated with an attenuation of leukocyte telomere length (LTL) shortening. However, more controversy exists regarding higher exercise loads such as those imposed by elite-sport participation. The authors investigated LTL differences between young elite athletes (n = 61, 54% men, age [mean ± SD] 27.2 ± 4.9 y) and healthy nonsmoker, physically inactive controls (n = 64, 52% men, 28.9 ± 6.3 y) using analysis of variance (ANOVA). Elite athletes had, on average, higher LTL than control subjects, 0.89 ± 0.26 vs 0.78 ± 0.31, P = .013 for the group effect, with no significant sex (P = .995) or age effect (P = .114). The results suggest that young elite athletes have longer telomeres than their inactive peers. Further research might assess the LTL of elite athletes of varying ages compared with both age-matched active and inactive individuals.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-11-07

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

  3. Super-resolution fluorescence imaging of telomeres reveals TRF2-dependent T-loop formation.

    Science.gov (United States)

    Doksani, Ylli; Wu, John Y; de Lange, Titia; Zhuang, Xiaowei

    2013-10-10

    We have applied a super-resolution fluorescence imaging method, stochastic optical reconstruction microscopy (STORM), to visualize the structure of functional telomeres and telomeres rendered dysfunctional through removal of shelterin proteins. The STORM images showed that functional telomeres frequently exhibit a t-loop configuration. Conditional deletion of individual components of shelterin showed that TRF2 was required for the formation and/or maintenance of t-loops, whereas deletion of TRF1, Rap1, or the POT1 proteins (POT1a and POT1b) had no effect on the frequency of t-loop occurrence. Within the shelterin complex, TRF2 uniquely serves to protect telomeres from two pathways that are initiated on free DNA ends: classical nonhomologous end-joining (NHEJ) and ATM-dependent DNA damage signaling. The TRF2-dependent remodeling of telomeres into t-loop structures, which sequester the ends of chromosomes, can explain why NHEJ and the ATM signaling pathway are repressed when TRF2 is present. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Heat shock factor 1 promotes TERRA transcription and telomere protection upon heat stress.

    Science.gov (United States)

    Koskas, Sivan; Decottignies, Anabelle; Dufour, Solenne; Pezet, Mylène; Verdel, André; Vourc'h, Claire; Faure, Virginie

    2017-06-20

    In response to metabolic or environmental stress, cells activate powerful defense mechanisms to prevent the formation and accumulation of toxic protein aggregates. The main orchestrator of this cellular response is HSF1 (heat shock factor 1), a transcription factor involved in the up-regulation of protein-coding genes with protective roles. It has become very clear that HSF1 has a broader function than initially expected. Indeed, our previous work demonstrated that, upon stress, HSF1 activates the transcription of a non-coding RNA, named Satellite III, at pericentromeric heterochromatin. Here, we observe that the function of HSF1 extends to telomeres and identify subtelomeric DNA as a new genomic target of HSF1. We show that the binding of HSF1 to subtelomeric regions plays an essential role in the upregulation of non-coding TElomeric Repeat containing RNA (TERRA) transcription upon heat shock. Importantly, our data show that telomere integrity is impacted by heat shock and that telomeric DNA damages are markedly enhanced in HSF1 deficient cells. Altogether, our findings reveal a new direct and essential function of HSF1 in the transcriptional activation of TERRA and in telomere protection upon stress. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  5. Induced senescence in HeLa cervical carcinoma cells containing elevated telomerase activity and extended telomeres.

    Science.gov (United States)

    Goodwin, E C; DiMaio, D

    2001-11-01

    Proliferation of normal somatic human cells in culture is limited by replicative senescence, a growth-arrested state that appears to be triggered by the erosion of telomeres. Tumor cells such as HeLa cervical carcinoma cells, which contain short telomeres, can be induced to undergo senescence by various manipulations including oncogene withdrawal. Repression of the human papillomavirus (HPV) type 18 E6/E7 genes in HeLa cells by the bovine papillomavirus E2 transcriptional regulatory protein results in reactivation of the dormant p53 and p105(Rb) tumor suppressor pathways in these cells, repression of telomerase, and profound growth arrest. Strikingly, the growth-arrested cells rapidly and synchronously acquired numerous characteristics of primary cells undergoing replicative senescence. To explore the role of telomerase and telomere length in induced senescence, we expressed an exogenous hTERT gene, which encodes the catalytic subunit of telomerase, to generate stable HeLa cell clones with elevated telomerase activity and extended telomeres. Expression of the E2 protein in these cells repressed HPV E6/E7 expression, activated tumor suppressor pathways, and induced senescence as assessed by growth arrest, morphological changes, senescence-associated beta-galactosidase expression, and increased autofluorescence. Cells carrying the hTERT gene and control cells displayed identical responses to E2 expression. Therefore, HeLa cell senescence induced by HPV repression is not triggered by short telomeres or low levels of telomerase activity.

  6. Stn1-Ten1 is an Rpa2-Rpa3-like complex at telomeres

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jia; Yu, Eun Young; Yang, Yuting; Confer, Laura A; Sun, Steven H; Wan, Ke; Lue, Neal F; Lei, Ming; (Weill); (Michigan-Med)

    2010-09-02

    In budding yeast, Cdc13, Stn1, and Ten1 form a heterotrimeric complex (CST) that is essential for telomere protection and maintenance. Previous bioinformatics analysis revealed a putative oligonucleotide/oligosaccharide-binding (OB) fold at the N terminus of Stn1 (Stn1N) that shows limited sequence similarity to the OB fold of Rpa2, a subunit of the eukaryotic ssDNA-binding protein complex replication protein A (RPA). Here we present functional and structural analyses of Stn1 and Ten1 from multiple budding and fission yeast. The crystal structure of the Candida tropicalis Stn1N complexed with Ten1 demonstrates an Rpa2N-Rpa3-like complex. In both structures, the OB folds of the two components pack against each other through interactions between two C-terminal helices. The structure of the C-terminal domain of Saccharomyces cerevisiae Stn1 (Stn1C) was found to comprise two related winged helix-turn-helix (WH) motifs, one of which is most similar to the WH motif at the C terminus of Rpa2, again supporting the notion that Stn1 resembles Rpa2. The crystal structure of the fission yeast Schizosaccharomyces pombe Stn1N-Ten1 complex exhibits a virtually identical architecture as the C. tropicalis Stn1N-Ten1. Functional analyses of the Candida albicans Stn1 and Ten1 proteins revealed critical roles for these proteins in suppressing aberrant telomerase and recombination activities at telomeres. Mutations that disrupt the Stn1-Ten1 interaction induce telomere uncapping and abolish the telomere localization of Ten1. Collectively, our structural and functional studies illustrate that, instead of being confined to budding yeast telomeres, the CST complex may represent an evolutionarily conserved RPA-like telomeric complex at the 3' overhangs that works in parallel with or instead of the well-characterized POT1-TPP1/TEBP{alpha}-{beta} complex.

  7. A selfish DNA element engages a meiosis-specific motor and telomeres for germ-line propagation

    Science.gov (United States)

    Sau, Soumitra; Conrad, Michael N.; Lee, Chih-Ying; Kaback, David B.; Dresser, Michael E.

    2014-01-01

    The chromosome-like mitotic stability of the yeast 2 micron plasmid is conferred by the plasmid proteins Rep1-Rep2 and the cis-acting locus STB, likely by promoting plasmid-chromosome association and segregation by hitchhiking. Our analysis reveals that stable plasmid segregation during meiosis requires the bouquet proteins Ndj1 and Csm4. Plasmid relocalization from the nuclear interior in mitotic cells to the periphery at or proximal to telomeres rises from early meiosis to pachytene. Analogous to chromosomes, the plasmid undergoes Csm4- and Ndj1-dependent rapid prophase movements with speeds comparable to those of telomeres. Lack of Ndj1 partially disrupts plasmid–telomere association without affecting plasmid colocalization with the telomere-binding protein Rap1. The plasmid appears to engage a meiosis-specific motor that orchestrates telomere-led chromosome movements for its telomere-associated segregation during meiosis I. This hitherto uncharacterized mode of germ-line transmission by a selfish genetic element signifies a mechanistic variation within the shared theme of chromosome-coupled plasmid segregation during mitosis and meiosis. PMID:24914236

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

    National Research Council Canada - National Science Library

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

    2015-01-01

    .... However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases...

  9. Accelerated Telomere Shortening in Acromegaly; IGF-I Induces Telomere Shortening and Cellular Senescence: e0140189

    National Research Council Canada - National Science Library

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

    2015-01-01

    .... However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases...

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

    Directory of Open Access Journals (Sweden)

    Greicy H Goto

    2015-08-01

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

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

    Directory of Open Access Journals (Sweden)

    Hien-Ping Ngo

    2010-08-01

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

  12. Disruption of direct 3D telomere-TRF2 interaction through two molecularly disparate mechanisms is a hallmark of primary Hodgkin and Reed-Sternberg cells.

    Science.gov (United States)

    Knecht, Hans; Johnson, Nathalie A; Haliotis, Tina; Lichtensztejn, Daniel; Mai, Sabine

    2017-07-01

    In classical Hodgkin's lymphoma (cHL), specific changes in the 3D telomere organization cause progression from mononuclear Hodgkin cells (H) to multinucleated Reed-Sternberg cells (RS). In a post-germinal center B-cell in vitro model, permanent latent membrane protein 1 (LMP1) expression, as observed in Epstein-Barr virus (EBV)-associated cHL, results in multinuclearity and complex chromosomal aberrations through downregulation of key element of the shelterin complex, the telomere repeat binding factor 2 (TRF2). Thus, we hypothesized that the three-dimensional (3D) telomere-TRF2 interaction was progressively disturbed during transition from H to RS cells. To this end, we developed and applied for the first time a combined quantitative 3D TRF2-telomere immune fluorescent in situ hybridization (3D TRF2/Telo-Q-FISH) technique to monolayers of primary H and RS cells, and adjacent benign internal control lymphocytes of lymph node biopsy suspensions from diagnostic lymph node biopsies of 14 patients with cHL. We show that H and RS cells are characterized by two distinct patterns of disruption of 3D telomere-TRF2 interaction. Disruption pattern A is defined by massive attrition of telomere signals and a considerable increase of TRF2 signals not associated with telomeres. This pattern is restricted to EBV-negative cHL. Disruption pattern B is defined by telomere de-protection due to an impressive loss of TRF2 signals, physically linked to telomeres. This pattern is typical of, but is not restricted to, LMP1+EBV-associated cHL. In the disruption pattern B group, so-called 'ghost' end-stage RS cells, void of both TRF2 and telomere signals, were identified, whether or not associated with EBV. Our findings demonstrate that two molecularly disparate mechanisms converge on the level of 3D telomere-TRF2 interaction in the formation of RS cells.

  13. Telomere Maintenance in the Absence of Telomerase

    National Research Council Canada - National Science Library

    Lundblad, Vicki

    2000-01-01

    .... In the budding yeasts S. cerevisiae and K. lactis, telomerase- independent survival is mediated via RAD52-dependent recombination which results in amplification of telomeric and subtelomeric repeat sequences...

  14. Telomere length in early life predicts lifespan

    OpenAIRE

    Heidinger, B. J.; Blount, J.D.; Boner, W.; Griffiths, K.; Metcalfe, N.B.; Monaghan, P.

    2012-01-01

    The attrition of telomeres, the ends of eukaryote chromosomes, is thought to play an important role in cell deterioration with advancing age. The observed variation in telomere length among individuals of the same age is therefore thought to be related to variation in potential longevity. Studies of this relationship are hampered by the time scale over which individuals need to be followed, particularly in long-lived species where lifespan variation is greatest. So far, data are based either ...

  15. Telomeres and the ethics of human cloning.

    Science.gov (United States)

    Allhoff, Fritz

    2004-01-01

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

  16. Identification of Proteins Essential for Telomere Elongation

    National Research Council Canada - National Science Library

    Banik, Soma

    2003-01-01

    .... One of the most consistent changes to occur n breast cancer is cellular immortalization through the upregulation of hTERT, which encodes the catalytic subunit of the telomerase ribonucleoprotein holoenzyme...

  17. Zscan4 Is Activated after Telomere Shortening in Mouse Embryonic Stem Cells

    Directory of Open Access Journals (Sweden)

    Yoko Nakai-Futatsugi

    2016-04-01

    Full Text Available ZSCAN4 is a DNA-binding protein that functions for telomere elongation and genomic stability. In vivo, it is specifically expressed at the two-cell stage during mouse development. In vitro, it is transiently expressed in mouse embryonic stem cells (ESCs, only in 5% of the population at one time. Here we attempted to elucidate when, under what circumstances, Zscan4 is activated in ESCs. Using live cell imaging, we monitored the activity of Zscan4 together with the pluripotency marker Rex1. The lengths of the cell cycles in ESCs were diverse. Longer cell cycles were accompanied by shorter telomeres and higher activation of Zscan4. Since activation of Zscan4 is involved in telomere elongation, we speculate that the extended cell cycles accompanied by Zscan4 activation reflect the time for telomere recovery. Rex1 and Zscan4 did not show any correlation. Taken together, we propose that Zscan4 is activated to recover shortened telomeres during extended cell cycles, irrespective of the pluripotent status.

  18. Human cells lacking coilin and Cajal bodies are proficient in telomerase assembly, trafficking and telomere maintenance.

    Science.gov (United States)

    Chen, Yanlian; Deng, Zhiqiang; Jiang, Shuai; Hu, Qian; Liu, Haiying; Songyang, Zhou; Ma, Wenbin; Chen, Shi; Zhao, Yong

    2015-01-01

    The RNA component of human telomerase (hTR) localizes to Cajal bodies, and it has been proposed that Cajal bodies play a role in the assembly of telomerase holoenzyme and telomerase trafficking. Here, the role of Cajal bodies was examined in Human cells deficient of coilin (i.e. coilin-knockout (KO) cells), in which no Cajal bodies are detected. In coilin-KO cells, a normal level of telomerase activity is detected and interactions between core factors of holoenzyme are preserved, indicating that telomerase assembly occurs in the absence of Cajal bodies. Moreover, dispersed hTR aggregates and forms foci specifically during S and G2 phase in coilin-KO cells. Colocalization of these hTR foci with telomeres implies proper telomerase trafficking, independent of Cajal bodies. Therefore, telomerase adds similar numbers of TTAGGG repeats to telomeres in coilin-KO and controls cells. Overexpression of TPP1-OB-fold blocks cell cycle-dependent formation of hTR foci and inhibits telomere extension. These findings suggest that telomerase assembly, trafficking and extension occur with normal efficiency in Cajal bodies deficient human cells. Thus, Cajal bodies, as such, are not essential in these processes, although it remains possible that non-coilin components of Cajal bodies and/or telomere binding proteins (e.g. TPP1) do play roles in telomerase biogenesis and telomere homeostasis. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

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

    Directory of Open Access Journals (Sweden)

    Jue Lin

    2016-01-01

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

  20. XPO1 Inhibition Preferentially Disrupts the 3D Nuclear Organization of Telomeres in Tumor Cells

    Science.gov (United States)

    Taylor‐Kashton, Cheryl; Lichtensztejn, Daniel; Baloglu, Erkan; Senapedis, William; Shacham, Sharon; Kauffman, Michael G.; Kotb, Rami

    2016-01-01

    Previous work has shown that the three‐dimensional (3D) nuclear organization of telomeres is altered in cancer cells and the degree of alterations coincides with aggressiveness of disease. Nuclear pores are essential for spatial genome organization and gene regulation and XPO1 (exportin 1/CRM1) is the key nuclear export protein. The Selective Inhibitor of Nuclear Export (SINE) compounds developed by Karyopharm Therapeutics (KPT‐185, KPT‐330/selinexor, and KPT‐8602) inhibit XPO1 nuclear export function. In this study, we investigated whether XPO1 inhibition has downstream effects on the 3D nuclear organization of the genome. This was assessed by measuring the 3D telomeric architecture of normal and tumor cells in vitro and ex vivo. Our data demonstrate for the first time a rapid and preferential disruption of the 3D nuclear organization of telomeres in tumor cell lines and in primary cells ex vivo derived from treatment‐naïve newly diagnosed multiple myeloma patients. Normal primary cells in culture as well as healthy lymphocyte control cells from the same patients were minimally affected. Using both lymphoid and non‐lymphoid tumor cell lines, we found that the downstream effects on the 3D nuclear telomere structure are independent of tumor type. We conclude that the 3D nuclear organization of telomeres is a sensitive indicator of cellular response when treated with XPO1 inhibitors. J. Cell. Physiol. 231: 2711–2719, 2016. © 2016 The Authors. Journal of Cellular Physiology published by Wiley Periodicals, Inc. PMID:26991404

  1. XPO1 Inhibition Preferentially Disrupts the 3D Nuclear Organization of Telomeres in Tumor Cells.

    Science.gov (United States)

    Taylor-Kashton, Cheryl; Lichtensztejn, Daniel; Baloglu, Erkan; Senapedis, William; Shacham, Sharon; Kauffman, Michael G; Kotb, Rami; Mai, Sabine

    2016-12-01

    Previous work has shown that the three-dimensional (3D) nuclear organization of telomeres is altered in cancer cells and the degree of alterations coincides with aggressiveness of disease. Nuclear pores are essential for spatial genome organization and gene regulation and XPO1 (exportin 1/CRM1) is the key nuclear export protein. The Selective Inhibitor of Nuclear Export (SINE) compounds developed by Karyopharm Therapeutics (KPT-185, KPT-330/selinexor, and KPT-8602) inhibit XPO1 nuclear export function. In this study, we investigated whether XPO1 inhibition has downstream effects on the 3D nuclear organization of the genome. This was assessed by measuring the 3D telomeric architecture of normal and tumor cells in vitro and ex vivo. Our data demonstrate for the first time a rapid and preferential disruption of the 3D nuclear organization of telomeres in tumor cell lines and in primary cells ex vivo derived from treatment-naïve newly diagnosed multiple myeloma patients. Normal primary cells in culture as well as healthy lymphocyte control cells from the same patients were minimally affected. Using both lymphoid and non-lymphoid tumor cell lines, we found that the downstream effects on the 3D nuclear telomere structure are independent of tumor type. We conclude that the 3D nuclear organization of telomeres is a sensitive indicator of cellular response when treated with XPO1 inhibitors. J. Cell. Physiol. 231: 2711-2719, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  2. Telomere Dynamics in Immune Senescence and Exhaustion Triggered by Chronic Viral Infection.

    Science.gov (United States)

    Bellon, Marcia; Nicot, Christophe

    2017-10-05

    The progressive loss of immunological memory during aging correlates with a reduced proliferative capacity and shortened telomeres of T cells. Growing evidence suggests that this phenotype is recapitulated during chronic viral infection. The antigenic volume imposed by persistent and latent viruses exposes the immune system to unique challenges that lead to host T-cell exhaustion, characterized by impaired T-cell functions. These dysfunctional memory T cells lack telomerase, the protein capable of extending and stabilizing chromosome ends, imposing constraints on telomere dynamics. A deleterious consequence of this excessive telomere shortening is the premature induction of replicative senescence of viral-specific CD8+ memory T cells. While senescent cells are unable to expand, they can survive for extended periods of time and are more resistant to apoptotic signals. This review takes a closer look at T-cell exhaustion in chronic viruses known to cause human disease: Epstein-Barr virus (EBV), Hepatitis B/C/D virus (HBV/HCV/HDV), human herpesvirus 8 (HHV-8), human immunodeficiency virus (HIV), human T-cell leukemia virus type I (HTLV-I), human papillomavirus (HPV), herpes simplex virus-1/2(HSV-1/2), and Varicella-Zoster virus (VZV). Current literature linking T-cell exhaustion with critical telomere lengths and immune senescence are discussed. The concept that enduring antigen stimulation leads to T-cell exhaustion that favors telomere attrition and a cell fate marked by enhanced T-cell senescence appears to be a common endpoint to chronic viral infections.

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

    Science.gov (United States)

    Fouquerel, Elise; Opresko, Patricia L

    2017-01-01

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

  4. Positive feedback between p53 and TRF2 during telomere-damage signalling and cellular senescence.

    Science.gov (United States)

    Fujita, Kaori; Horikawa, Izumi; Mondal, Abdul M; Jenkins, Lisa M Miller; Appella, Ettore; Vojtesek, Borivoj; Bourdon, Jean-Christophe; Lane, David P; Harris, Curtis C

    2010-12-01

    The telomere-capping complex shelterin protects functional telomeres and prevents the initiation of unwanted DNA-damage-response pathways. At the end of cellular replicative lifespan, uncapped telomeres lose this protective mechanism and DNA-damage signalling pathways are triggered that activate p53 and thereby induce replicative senescence. Here, we identify a signalling pathway involving p53, Siah1 (a p53-inducible E3 ubiquitin ligase) and TRF2 (telomere repeat binding factor 2; a component of the shelterin complex). Endogenous Siah1 and TRF2 were upregulated and downregulated, respectively, during replicative senescence with activated p53. Experimental manipulation of p53 expression demonstrated that p53 induces Siah1 and represses TRF2 protein levels. The p53-dependent ubiquitylation and proteasomal degradation of TRF2 are attributed to the E3 ligase activity of Siah1. Knockdown of Siah1 stabilized TRF2 and delayed the onset of cellular replicative senescence, suggesting a role for Siah1 and TRF2 in p53-regulated senescence. This study reveals that p53, a downstream effector of telomere-initiated damage signalling, also functions upstream of the shelterin complex.

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

    Directory of Open Access Journals (Sweden)

    Kirsi Ahola

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

  6. Expression of telomerase reverse transcriptase and telomere elongation during sexual maturation in Paramecium caudatum.

    Science.gov (United States)

    Takenaka, Y; Matsuura, T; Haga, N; Mitsui, Y

    2001-02-21

    Paramecium caudatum has a sexually immature period that lasts for about 60 fissions. To examine the possibility that telomere length is one of the determining factors of the duration of immaturity, we cloned the telomerase reverse transcriptase (TERT) gene from P. caudatum, and analyzed its expression levels at mRNA, telomerase activity, and telomere length during the course of clonal division. Paramecium TERT (Pc_TERT) cDNA encodes a basic protein of 107 kDa that harbors conserved RT motifs, T motif, CP motif, and N motif. Pc_TERT mRNA is expressed at very low levels only detectable by RT-PCR, but constitutively, during immature and mature periods, exhibiting abundant telomerase activity. No clear phase shift in Pc_TERT expression, telomerase activity, or telomere length was observed at the point of maturation in P. caudatum. Instead, the telomere elongates successively as cells divide in P. caudatum, although a close species, P. tetraurelia, was reported to keep the length constant. We discuss possible mechanisms for the expression of sexual activity associated with telomere length in P. caudatum.

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

    Directory of Open Access Journals (Sweden)

    Cristina Bartocci

    2014-05-01

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

  8. Telomere--the twilight to immortality.

    Science.gov (United States)

    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.

  9. Telomere protection and TRF2 expression are enhanced by the canonical Wnt signalling pathway.

    Science.gov (United States)

    Diala, Irmina; Wagner, Nicole; Magdinier, Frédérique; Shkreli, Marina; Sirakov, Maria; Bauwens, Serge; Schluth-Bolard, Caroline; Simonet, Thomas; Renault, Valérie M; Ye, Jing; Djerbi, Abdelnnadir; Pineau, Pascal; Choi, Jinkuk; Artandi, Steven; Dejean, Anne; Plateroti, Michelina; Gilson, Eric

    2013-04-01

    The DNA-binding protein TRF2 is essential for telomere protection and chromosome stability in mammals. We show here that TRF2 expression is activated by the Wnt/β-catenin signalling pathway in human cancer and normal cells as well as in mouse intestinal tissues. Furthermore, β-catenin binds to TRF2 gene regulatory regions that are functional in a luciferase transactivating assay. Reduced β-catenin expression in cancer cells triggers a marked increase in telomere dysfunction, which can be reversed by TRF2 overexpression. We conclude that the Wnt/β-catenin signalling pathway maintains a level of TRF2 critical for telomere protection. This is expected to have an important role during development, adult stem cell function and oncogenesis.

  10. Telomeres and Telomerase in The Aging Heart

    Directory of Open Access Journals (Sweden)

    Anna Meiliana

    2017-12-01

    Full Text Available BACKGROUND: Aging per se is a risk factor for reduced cardiac function and heart diseases, even when adjusted for aging-associated cardiovascular risk factors. Accordingly, aging-related biochemical and cell-biological changes lead to pathophysiological conditions, especially reduced heart function and heart disease. CONTENT: Telomere dysfunction induces a profound p53-dependent repression of the master regulators of mitochondrial biogenesis and function, peroxisome proliferator-activated receptor gamma coactivator (PGC-1a and PGC-1b in the heart, which leads to bioenergetic compromise due to impaired oxidative phosphorylation and ATP generation. This telomere-p53-PGC mitochondrial/metabolic axis integrates many factors linked to heart aging including increased DNA damage, p53 activation, mitochondrial, and metabolic dysfunction and provides a molecular basis of how dysfunctional telomeres can compromise cardiomyocytes and stem cell compartments in the heart to precipitate cardiac aging. SUMMARY: The aging myocardium with telomere shortening and accumulation of senescent cells restricts the tissue regenerative ability, which contributes to systolic or diastolic heart failure. Moreover, patients with ion-channel defects might have genetic imbalance caused by oxidative stress-related accelerated telomere shortening, which may subsequently cause sudden cardiac death. Telomere length can serve as a marker for the biological status of previous cell divisions and DNA damage with inflammation and oxidative stress. It can be integrated into current risk prediction and stratification models for cardiovascular diseases and can be used in precise personalized treatments. KEYWORDS: aging, telomere, telomerase, aging heart, mitochondria, cardiac stem cell

  11. 3D nuclear organization of telomeres in the Hodgkin cell lines U-HO1 and U-HO1-PTPN1: PTPN1 expression prevents the formation of very short telomeres including "t-stumps"

    Directory of Open Access Journals (Sweden)

    Lemieux Bruno

    2010-12-01

    Full Text Available Abstract Background In cancer cells the three-dimensional (3D telomere organization of interphase nuclei into a telomeric disk is heavily distorted and aggregates are found. In Hodgkin's lymphoma quantitative FISH (3D Q-FISH reveals a major impact of nuclear telomere dynamics during the transition form mononuclear Hodgkin (H to diagnostic multinuclear Reed-Sternberg (RS cells. In vitro and in vivo formation of RS-cells is associated with the increase of very short telomeres including "t-stumps", telomere loss, telomeric aggregate formation and the generation of "ghost nuclei". Results Here we analyze the 3D telomere dynamics by Q-FISH in the novel Hodgkin cell line U-HO1 and its non-receptor protein-tyrosine phosphatase N1 (PTPN1 stable transfectant U-HO1-PTPN1, derived from a primary refractory Hodgkin's lymphoma. Both cell lines show equally high telomerase activity but U-HO1-PTPN differs from U-HO1 by a three times longer doubling time, low STAT5A expression, accumulation of RS-cells (p As expected, multinuclear U-HO1-RS-cells and multinuclear U-HO1-PTPN1-RS-cells differ from their mononuclear H-precursors by their nuclear volume (p Conclusion Abundant RS-cells without additional very short telomeres including "t-stumps", high rate of apoptosis, but low STAT5A expression, are hallmarks of the U-HO1-PTPN1 cell line. These characteristics are independent of telomerase activity. Thus, PTPN1 induced dephosphorylation of STAT5 with consecutive lack of Akt/PKB activation and cellular arrest in G2, promoting induction of apoptosis, appears as a possible pathogenetic mechanism deserving further experimental investigation.

  12. Renal failure induces telomere shortening in the rat heart

    NARCIS (Netherlands)

    Wong, L. S.; Windt, W. A.; Roks, A. J.; van Dokkum, R. P.; Schoemaker, R. G.; de Zeeuw, D.; Henning, R. H.

    Background. Renal failure aggravates pathological cardiac remodelling induced by myocardial infarction (MI). Cardiac remodelling is associated with telomere shortening, a marker for biological ageing. We investigated whether mild and severe renal failure shorten cardiac telomeres and excessively

  13. Tumor viruses and replicative immortality--avoiding the telomere hurdle.

    Science.gov (United States)

    Chen, Xinsong; Kamranvar, Siamak Akbari; Masucci, Maria G

    2014-06-01

    Tumor viruses promote cell proliferation in order to gain access to an environment suitable for persistence and replication. The expression of viral products that promote growth transformation is often accompanied by the induction of multiple signs of telomere dysfunction, including telomere shortening, damage of telomeric DNA and chromosome instability. Long-term survival and progression to full malignancy require the bypassing of senescence programs that are triggered by the damaged telomeres. Here we review different strategies by which tumor viruses interfere with telomere homeostasis during cell transformation. This frequently involves the activation of telomerase, which assures both the integrity and functionality of telomeres. In addition, recent evidence suggests that oncogenic viruses may activate a recombination-based mechanism for telomere elongation known as Alternative Lengthening of Telomeres (ALT). This error-prone strategy promotes genomic instability and could play an important role in viral oncogenesis. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Linking telomere loss and mitochondrial dysfunction in chronic disease

    DEFF Research Database (Denmark)

    Gonzalez-Ebsen, Ana Carlota; Gregersen, Niels; Olsen, Rikke Kj

    2017-01-01

    Telomeres and mitochondria are known to deteriorate over time. Telomere shortening is associated with aging, early senescence, and premature cell death. Mitochondrial dysfunction produces indiscriminate amounts of reactive oxygen species that may lead to oxidative damage to cellular constituents,...

  15. Telomere stability and telomerase in mesenchymal stem cells

    DEFF Research Database (Denmark)

    Serakinci, Nedime; Graakjaer, Jesper; Kølvrå, Steen

    2008-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    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.

  17. Telomere reprogramming and maintenance in porcine iPS cells.

    Directory of Open Access Journals (Sweden)

    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.

  18. Telomeres, workload and life-history in great tits

    OpenAIRE

    Atema, Els

    2017-01-01

    Ageing and the effects of increased workload in great tits A new measurement to quantify variation in quality and rate of ageing between individuals is telomere length. Telomeres are a piece of DNA at the end of chromosomes, and they protect the other DNA. In many species shortening of telomere length with increasing age was demonstrated. This shortening is accelerated by processes that also decrease life expectancy. In this project we discovered that telomeres of great tits differ from telom...

  19. Telomere reprogramming and maintenance in porcine iPS cells.

    Science.gov (United States)

    Ji, Guangzhen; Ruan, Weimin; Liu, Kai; Wang, Fang; Sakellariou, Despoina; Chen, Jijun; Yang, Yang; Okuka, Maja; Han, Jianyong; Liu, Zhonghua; Lai, Liangxue; Gagos, Sarantis; Xiao, Lei; Deng, Hongkui; Li, Ning; Liu, Lin

    2013-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Zhilong Wang

    2010-05-01

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

  1. Telomeres, workload and life-history in great tits

    NARCIS (Netherlands)

    Atema, Els

    2017-01-01

    Ageing and the effects of increased workload in great tits A new measurement to quantify variation in quality and rate of ageing between individuals is telomere length. Telomeres are a piece of DNA at the end of chromosomes, and they protect the other DNA. In many species shortening of telomere

  2. Acute coronary syndrome: Role of the telomere dynamic | Behjati ...

    African Journals Online (AJOL)

    Telomeres, or historically named "terminal genes" are first discovered by Muller working on fruit fly in 1930s. Since then, the great progress was made in understanding the consequences of telomere erosion on the human health and disease states, as age related vascular diseases. The overlapping links between telomere ...

  3. Approaching TERRA Firma: Genomic Functions of Telomeric Noncoding RNA.

    Science.gov (United States)

    Roake, Caitlin M; Artandi, Steven E

    2017-06-29

    Functions of the telomeric repeat-containing RNA (TERRA), the long noncoding RNA (lncRNA) transcribed from telomeres, have eluded researchers. In this issue of Cell, Graf el al. and Chu et al. uncover new regulatory roles for TERRA at the telomere and at distant genomic sites. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Telomere Length Correlates with Life Span of Dog Breeds

    Directory of Open Access Journals (Sweden)

    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.

  5. Recruitment of Rad51 and Rad52 to short telomeres triggers a Mec1-mediated hypersensitivity to double-stranded DNA breaks in senescent budding yeast.

    Directory of Open Access Journals (Sweden)

    Yi-Hsuan Lin

    Full Text Available Telomere maintenance is required for chromosome stability, and telomeres are typically replicated by the action of telomerase. In both mammalian tumor and yeast cells that lack telomerase, telomeres are maintained by an alternative recombination mechanism. Here we demonstrated that the budding yeast Saccharomyces cerevisiae type I survivors derived from telomerase-deficient cells were hypersensitive to DNA damaging agents. Assays to track telomere lengths and drug sensitivity of telomerase-deficient cells from spore colonies to survivors suggested a correlation between telomere shortening and bleomycin sensitivity. Our genetic studies demonstrated that this sensitivity depends on Mec1, which signals checkpoint activation, leading to prolonged cell-cycle arrest in senescent budding yeasts. Moreover, we also observed that when cells equipped with short telomeres, recruitments of homologous recombination proteins, Rad51 and Rad52, were reduced at an HO-endonuclease-catalyzed double-strand break (DSB, while their associations were increased at chromosome ends. These results suggested that the sensitive phenotype may be attributed to the sequestration of repair proteins to compromised telomeres, thus limiting the repair capacity at bona fide DSB sites.

  6. The TPR-containing domain within Est1 homologs exhibits species-specific roles in telomerase interaction and telomere length homeostasis

    Directory of Open Access Journals (Sweden)

    LeBel Catherine

    2011-10-01

    Full Text Available Abstract Background The first telomerase-associated protein (Est1 was isolated in yeast due to its essential role in telomere maintenance. The human counterparts EST1A, EST1B, and EST1C perform diverse functions in nonsense-mediated mRNA decay (NMD, telomere length homeostasis, and telomere transcription. Although Est1 and EST1A/B interact with the catalytic subunit of yeast and human telomerase (Est2 and TERT, respectively, the molecular determinants of these interactions have not been elaborated fully. Results To investigate the functional conservation of the EST1 protein family, we performed protein-protein interaction mapping and structure-function analysis. The domain in hEST1A most conserved between species, containing a TPR (tricotetrapeptide repeat, was sufficient for interaction of hEST1A with multiple fragments of hTERT including the N-terminus. Two mutations within the hTERT N-terminus that perturb in vivo function (NAAIRS92, NAAIRS122 did not affect this protein interaction. ScEst1 hybrids containing the TPR of hEST1A, hEST1B, or hEST1C were expressed in yeast strains lacking EST1, yet they failed to complement senescence. Point mutations within and outside the cognate ScEst1 TPR, chosen to disrupt a putative protein interaction surface, resulted in telomere lengthening or shortening without affecting recruitment to telomeres. Conclusions These results identify a domain encompassing the TPR of hEST1A as an hTERT interaction module. The TPR of S. cerevisiae Est1 is required for telomerase-mediated telomere length maintenance in a manner that appears separable from telomere recruitment. Discrete residues in or adjacent to the TPR of Est1 also regulate telomere length homeostasis.

  7. An evolutionary review of human telomere biology: the thrifty telomere hypothesis and notes on potential adaptive paternal effects.

    Science.gov (United States)

    Eisenberg, Dan T A

    2011-01-01

    Telomeres, repetitive DNA sequences found at the ends of linear chromosomes, play a role in regulating cellular proliferation, and shorten with increasing age in proliferating human tissues. The rate of age-related shortening of telomeres is highest early in life and decreases with age. Shortened telomeres are thought to limit the proliferation of cells and are associated with increased morbidity and mortality. Although natural selection is widely assumed to operate against long telomeres because they entail increased cancer risk, the evidence for this is mixed. Instead, here it is proposed that telomere length is primarily limited by energetic constraints. Cell proliferation is energetically expensive, so shorter telomeres should lead to a thrifty phenotype. Shorter telomeres are proposed to restrain adaptive immunity as an energy saving mechanism. Such a limited immune system, however, might also result in chronic infections, inflammatory stress, premature aging, and death--a more "disposable soma." With an increased reproductive lifespan, the fitness costs of premature aging are higher and longer telomeres will be favored by selection. Telomeres exhibit a paternal effect whereby the offspring of older fathers have longer telomeres due to increased telomere lengths of sperm with age. This paternal effect is proposed to be an adaptive signal of the expected age of male reproduction in the environment offspring are born into. The offspring of lineages of older fathers will tend to have longer, and thereby less thrifty, telomeres, better preparing them for an environment with higher expected ages at reproduction. Copyright © 2010 Wiley-Liss, Inc.

  8. Telomere length is shorter in healthy offspring of subjects with coronary artery disease : support for the telomere hypothesis

    NARCIS (Netherlands)

    Brouilette, S. W.; Whittaker, A.; Stevens, S. E.; van der Harst, P.; Goodall, A. H.; Samani, N. J.

    Background: Telomeres are shorter in subjects with coronary artery disease (CAD) and may indicate premature biological ageing. However, whether shorter telomeres are a primary abnormality or secondary to the disease is unclear. Objective: To investigate whether shorter telomeres are a primary

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-10-02

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

  10. Apparent ploidy effects on silencing are post-transcriptional at HML and telomeres in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Jenny M McLaughlan

    Full Text Available The repression of genes in regions of heterochromatin is known as transcriptional silencing. It occurs in a wide range of organisms and can have importance in adaptation to the environment, developmental changes and disease. The model organism Saccharomyces cerevisiae has been used for many years to study transcriptional silencing, but until recently no study has been made in relation to ploidy. The aim of this work was to compare transcriptional silencing in haploids and diploids at both telomeres and the hidden mating-type (HM loci. Transcriptional silencing was assayed, by growth on 5-fluoroorotic acid (5-FOA media or by flow cytometry, on strains where a telomere or HM locus was marked. RNA levels were measured by quantitative RT-PCR to confirm that effects were transcriptional. 5-FOA assays and flow cytometry were consistent with transcriptional silencing at telomeres and at HML being reduced as ploidy increases which agreed with conclusions in previous publications. However, QRT-PCR revealed that transcriptional silencing was unaffected by ploidy and thus protein levels were increasing independently of RNA levels. At telomere XI left (XI-L, changes in protein level were strongly influenced by mating-type, whereas at HML mating-type had much less influence. The post-transcriptional effects seen in this study, illustrate the often ignored need to measure RNA levels when assaying transcriptional silencing in Saccharomyces cerevisiae.

  11. Telomere length alterations unique to invasive lobular carcinoma.

    Science.gov (United States)

    Heaphy, Christopher M; Asch-Kendrick, Rebecca; Argani, Pedram; Meeker, Alan K; Cimino-Mathews, Ashley

    2015-08-01

    Telomeres are nucleoprotein complexes located at the extreme ends of eukaryotic chromosomes and protect chromosomal ends from degradation and recombination. Dysfunctional telomeres contribute to genomic instability, promote tumorigenesis, and, in breast cancer, have been associated with increased cancer risk and poor prognosis. Short telomere lengths have been previously associated with triple-negative and human epidermal growth factor receptor (Her2)--positive ductal carcinomas. However, these investigations have not specifically assessed invasive lobular carcinomas (ILCs), which accounts for 5% to 15% of all invasive breast cancers. Here, we evaluate telomere lengths within 48 primary ILCs with complete characterization of estrogen receptor (ER), progesterone receptor (PR), and Her2 status, including 32 luminal/Her2- (ER+/PR+/Her2-), 8 luminal/Her2+ (ER+/PR+/Her2+), 3 Her2+ (ER-/PR-/Her2+), and 5 triple-negative (ER-/PR-/Her2-) carcinomas. A telomere-specific fluorescence in situ hybridization assay, which provides single-cell telomere length resolution, was used to evaluate telomere lengths and compare with standard clinicopathological markers. In contrast to breast ductal carcinoma, in which more than 85% of cases display abnormally short telomeres, approximately half (52%) of the ILCs displayed either normal or long telomeres. Short telomere length was associated with older patient age. Interestingly, 3 cases (6%) displayed a unique telomere pattern consisting of 1 or 2 bright telomere spots among the normal telomere signals within each individual cancer cell, a phenotype that has not been previously described. Additional studies are needed to further evaluate the significance of the unique bright telomere spot phenotype and the potential utility of telomere length as a prognostic marker in ILC. Copyright © 2015 Elsevier Inc. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Kez Cleal

    2018-02-01

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

  13. Tetrafluoroethylene telomerization initiated by benzoyl peroxide

    Science.gov (United States)

    Bolshakov, A. I.; Kuzina, S. I.; Kiryukhin, D. P.

    2017-03-01

    The radical telomerization of tetrafluoroethylene initiated by benzoyl peroxide (BP) photolysis at λ ≥ 365 nm is studied in acetone, dichloromethane, carbon tetrachloride, and Freon 114B2 at 25°C. The products of synthesis are a mixture of telomers of different molar masses, segregated into soluble and insoluble fractions. To characterize the radicals initiating telomerization, crystalline BP and its solution in ethanol are subjected to low-temperature (77 K) photolysis, with the liquid system serving as a model for BP behavior in solutions of telogens. It is established that radicals are not only initiators but also participate in chain termination reactions, lowering the telomers' molar mass and thus raising the proportion of the soluble fraction. Telomerization initiated by an initiator compound versus initiation by gamma radiation are compared and discussed.

  14. Telomeres and the natural lifespan limit in humans

    DEFF Research Database (Denmark)

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

    2017-01-01

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

  15. Repair of UV-induced DNA lesions in natural Saccharomyces cerevisiae telomeres is moderated by Sir2 and Sir3, and inhibited by yKu–Sir4 interaction

    Science.gov (United States)

    Guintini, Laetitia; Tremblay, Maxime; Toussaint, Martin; D’Amours, Annie; Wellinger, Ralf E.

    2017-01-01

    Abstract Ultraviolet light (UV) causes DNA damage that is removed by nucleotide excision repair (NER). UV-induced DNA lesions must be recognized and repaired in nucleosomal DNA, higher order structures of chromatin and within different nuclear sub-compartments. Telomeric DNA is made of short tandem repeats located at the ends of chromosomes and their maintenance is critical to prevent genome instability. In Saccharomyces cerevisiae the chromatin structure of natural telomeres is distinctive and contingent to telomeric DNA sequences. Namely, nucleosomes and Sir proteins form the heterochromatin like structure of X-type telomeres, whereas a more open conformation is present at Y’-type telomeres. It is proposed that there are no nucleosomes on the most distal telomeric repeat DNA, which is bound by a complex of proteins and folded into higher order structure. How these structures affect NER is poorly understood. Our data indicate that the X-type, but not the Y’-type, sub-telomeric chromatin modulates NER, a consequence of Sir protein-dependent nucleosome stability. The telomere terminal complex also prevents NER, however, this effect is largely dependent on the yKu–Sir4 interaction, but Sir2 and Sir3 independent. PMID:28334768

  16. Repair of UV-induced DNA lesions in natural Saccharomyces cerevisiae telomeres is moderated by Sir2 and Sir3, and inhibited by yKu-Sir4 interaction.

    Science.gov (United States)

    Guintini, Laetitia; Tremblay, Maxime; Toussaint, Martin; D'Amours, Annie; Wellinger, Ralf E; Wellinger, Raymund J; Conconi, Antonio

    2017-05-05

    Ultraviolet light (UV) causes DNA damage that is removed by nucleotide excision repair (NER). UV-induced DNA lesions must be recognized and repaired in nucleosomal DNA, higher order structures of chromatin and within different nuclear sub-compartments. Telomeric DNA is made of short tandem repeats located at the ends of chromosomes and their maintenance is critical to prevent genome instability. In Saccharomyces cerevisiae the chromatin structure of natural telomeres is distinctive and contingent to telomeric DNA sequences. Namely, nucleosomes and Sir proteins form the heterochromatin like structure of X-type telomeres, whereas a more open conformation is present at Y'-type telomeres. It is proposed that there are no nucleosomes on the most distal telomeric repeat DNA, which is bound by a complex of proteins and folded into higher order structure. How these structures affect NER is poorly understood. Our data indicate that the X-type, but not the Y'-type, sub-telomeric chromatin modulates NER, a consequence of Sir protein-dependent nucleosome stability. The telomere terminal complex also prevents NER, however, this effect is largely dependent on the yKu-Sir4 interaction, but Sir2 and Sir3 independent. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  17. Telomere tracking from birth to adulthood and residential traffic exposure.

    Science.gov (United States)

    Bijnens, Esmée M; Zeegers, Maurice P; Derom, Catherine; Martens, Dries S; Gielen, Marij; Hageman, Geja J; Plusquin, Michelle; Thiery, Evert; Vlietinck, Robert; Nawrot, Tim S

    2017-11-21

    Telomere attrition is extremely rapid during the first years of life, while lifestyle during adulthood exerts a minor impact. This suggests that early life is an important period in the determination of telomere length. We investigated the importance of the early-life environment on both telomere tracking and adult telomere length. Among 184 twins of the East Flanders Prospective Twin Survey, telomere length in placental tissue and in buccal cells in young adulthood was measured. Residential addresses at birth and in young adulthood were geocoded and residential traffic and greenness exposure was determined. We investigated individual telomere tracking from birth over a 20 year period (mean age (SD), 22.6 (3.1) years) in association with residential exposure to traffic and greenness. Telomere length in placental tissue and in buccal cells in young adulthood correlated positively (r = 0.31, P adulthood was negatively and significantly associated with residential traffic exposure at the birth address, while traffic exposure at the residential address at adult age was not associated with telomere length. Longitudinal evidence of telomere length tracking from birth to adulthood shows inverse associations of residential traffic exposure in association with telomere length at birth as well as accelerated telomere shortening in the first two decades of life.

  18. TERRA promotes telomerase-mediated telomere elongation in Schizosaccharomyces pombe.

    Science.gov (United States)

    Moravec, Martin; Wischnewski, Harry; Bah, Amadou; Hu, Yan; Liu, Na; Lafranchi, Lorenzo; King, Megan C; Azzalin, Claus M

    2016-07-01

    Telomerase-mediated telomere elongation provides cell populations with the ability to proliferate indefinitely. Telomerase is capable of recognizing and extending the shortest telomeres in cells; nevertheless, how this mechanism is executed remains unclear. Here, we show that, in the fission yeast Schizosaccharomyces pombe, shortened telomeres are highly transcribed into the evolutionarily conserved long noncoding RNA TERRA A fraction of TERRA produced upon telomere shortening is polyadenylated and largely devoid of telomeric repeats, and furthermore, telomerase physically interacts with this polyadenylated TERRA in vivo We also show that experimentally enhanced transcription of a manipulated telomere promotes its association with telomerase and concomitant elongation. Our data represent the first direct evidence that TERRA stimulates telomerase recruitment and activity at chromosome ends in an organism with human-like telomeres. © 2016 The Authors.

  19. Homeostasis of telomere length rather than telomere shortening after allogeneic peripheral blood stem cell transplantation

    NARCIS (Netherlands)

    Roelofs, Helene; de Pauw, Elmar S. D.; Zwinderman, Aeilko H.; Opdam, Sonja M.; Willemze, Roel; Tanke, Hans J.; Fibbe, Willem E.

    2003-01-01

    Hematopoietic reconstitution after stem cell transplantation requires excessive replicative activity because of the limited number of stem cells that are used for transplantation. Telomere shortening has been detected in hematopoietic cells after bone marrow transplantation. This has been thought to

  20. TRF2 binds branched DNA to safeguard telomere integrity.

    Science.gov (United States)

    Schmutz, Isabelle; Timashev, Leonid; Xie, Wei; Patel, Dinshaw J; de Lange, Titia

    2017-09-01

    Although t-loops protect telomeres, they are at risk of cleavage by Holliday junction (HJ) resolvases if branch migration converts the three-way t-loop junction into four-way HJs. T-loop cleavage is repressed by the TRF2 basic domain, which binds three- and four-way junctions and protects HJs in vitro. By replacing the basic domain with bacterial-protein domains binding three- and four-way junctions, we demonstrated the in vivo relevance of branched-DNA binding. Branched-DNA binding also repressed PARP1, presumably by masking the PARP1 site in the t-loop junction. Although PARP1 recruits HJ resolvases and promotes t-loop cleavage, PARP1 activation alone did not result in t-loop cleavage, thus suggesting that the basic domain also prevents formation of HJs. Concordantly, removal of HJs by BLM helicase mitigated t-loop cleavage in response to loss of the basic domain. We propose that TRF2 masks and stabilizes the t-loop three-way junction, thereby protecting telomeres from detrimental deletions and PARP1 activation.

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

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    Despoina Sakellariou

    2013-11-01

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

  2. A loopy view of telomere evolution

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    Titia eDe Lange

    2015-10-01

    Full Text Available About a decade ago, I proposed that t-loops, the lariat structures adopted by many eukaryotic telomeres, could explain how the transition from circular to linear chromosomes was successfully negotiated by early eukaryotes. Here I reconsider this loopy hypothesis in the context of the idea that eukaryotes evolved through a period of genome invasion by Group II introns.

  3. Paternal age and telomere length in twins

    DEFF Research Database (Denmark)

    Hjelmborg, Jacob B; Dalgård, Christine; Mangino, Massimo

    2015-01-01

    . 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...

  4. Twin correlations of telomere length metrics

    DEFF Research Database (Denmark)

    Hjelmborg, Jacob B; Dalgård, Christine; Möller, Sören

    2015-01-01

    BACKGROUND: Leucocyte telomere length (LTL) is a complex trait associated with ageing and longevity. LTL dynamics are defined by LTL and its age-dependent attrition. Strong, but indirect evidence suggests that LTL at birth and its attrition during childhood largely explains interindividual LTL va...

  5. Antagonizing functions of BARD1 and its alternatively spliced variant BARD1δ in telomere stability

    Science.gov (United States)

    Pilyugin, Maxim; André, Pierre-Alain; Ratajska, Magdalena; Kuzniacka, Alina; Limon, Janusz; Tournier, Benjamin B.; Colas, Julien; Laurent, Geoff; Irminger-Finger, Irmgard

    2017-01-01

    Previous reports have shown that expression of BARD1δ, a deletion-bearing isoform of BARD1, correlates with tumor aggressiveness and progression. We show that expression of BARD1δ induces cell cycle arrest in vitro and in vivo in non-malignant cells. We investigated the mechanism that leads to proliferation arrest and found that BARD1δ overexpression induced mitotic arrest with chromosome and telomere aberrations in cell cultures, in transgenic mice, and in cells from human breast and ovarian cancer patients with BARD1 mutations. BARD1δ binds more efficiently than BARD1 to telomere binding proteins and causes their depletion from telomeres, leading to telomere and chromosomal instability. While this induces cell cycle arrest, cancer cells lacking G2/M checkpoint controls might continue to proliferate despite the BARD1δ-induced chromosomal instability. These features of BARD1δ may make it a genome permutator and a driver of continuous uncontrolled proliferation of cancer cells. PMID:28030839

  6. Positive feedback between p53 and TRF2 in telomere damage signaling and cellular senescence

    Science.gov (United States)

    Fujita, Kaori; Horikawa, Izumi; Mondal, Abdul M.; Miller Jenkins, Lisa M.; Appella, Ettore; Vojtesek, Borivoj; Bourdon, Jean-Christophe; Lane, David P.; Harris, Curtis C.

    2012-01-01

    The telomere-capping complex (shelterin) protects functional telomeres from initiating unwanted DNA damage response. Uncapped telomeres at the end of cellular replicative lifespan lose this protective mechanism and trigger DNA damage signaling to activate p53 and thereby induce replicative senescence. Here we identify a signaling pathway involving p53, Siah-1, a p53-inducible E3 ubiquitin ligase, and TRF2, a component of the shelterin complex. Endogenous Siah-1 and TRF2 were up- and down-regulated, respectively, at replicative senescence with activated p53. A series of experimental manipulations of p53 showed that p53 induced Siah-1 and repressed TRF2 protein levels. The p53-dependent ubiquitination and proteasomal degradation of TRF2 were attributed to the E3 ligase activity of Siah-1. Siah-1 knockdown stabilized TRF2 and delayed the onset of cellular replicative senescence, suggesting the role of Siah-1 and TRF2 in p53-regulated senescence. This study reveals that p53, a downstream effector of the telomere-initiated damage signaling, also functions upstream of the shelterin complex. PMID:21057505

  7. Identification of TERRA locus unveils a telomere protection role through association to nearly all chromosomes.

    Science.gov (United States)

    López de Silanes, Isabel; Graña, Osvaldo; De Bonis, Maria Luigia; Dominguez, Orlando; Pisano, David G; Blasco, Maria A

    2014-09-03

    Telomeric RNAs (TERRAs) are UUAGGG repeat-containing RNAs that are transcribed from the subtelomere towards the telomere. The precise genomic origin of TERRA has remained elusive. Using a whole-genome RNA-sequencing approach, we identify novel mouse transcripts arising mainly from the subtelomere of chromosome 18, and to a lesser extend chromosome 9, that resemble TERRA in several key aspects. Those transcripts contain UUAGGG-repeats and are heterogeneous in size, fluctuate in abundance in a TERRA-like manner during the cell cycle, are bound by TERRA RNA-binding proteins and are regulated in a manner similar to TERRA in response to stress and the induction of pluripotency. These transcripts are also found to associate with nearly all chromosome ends and downregulation of the transcripts that originate from chromosome 18 causes a reduction in TERRA abundance. Interestingly, downregulation of either chromosome 18 transcripts or TERRA results in increased number of telomere dysfunction-induced foci, suggesting a protective role at telomeres.

  8. Functional characterization of the TERRA transcriptome at damaged telomeres.

    Science.gov (United States)

    Porro, Antonio; Feuerhahn, Sascha; Delafontaine, Julien; Riethman, Harold; Rougemont, Jacques; Lingner, Joachim

    2014-10-31

    Telomere deprotection occurs during tumorigenesis and aging upon telomere shortening or loss of the telomeric shelterin component TRF2. Deprotected telomeres undergo changes in chromatin structure and elicit a DNA damage response (DDR) that leads to cellular senescence. The telomeric long noncoding RNA TERRA has been implicated in modulating the structure and processing of deprotected telomeres. Here, we characterize the human TERRA transcriptome at normal and TRF2-depleted telomeres and demonstrate that TERRA upregulation is occurring upon depletion of TRF2 at all transcribed telomeres. TRF2 represses TERRA transcription through its homodimerization domain, which was previously shown to induce chromatin compaction and to prevent the early steps of DDR activation. We show that TERRA associates with SUV39H1 H3K9 histone methyltransferase, which promotes accumulation of H3K9me3 at damaged telomeres and end-to-end fusions. Altogether our data elucidate the TERRA landscape and defines critical roles for this RNA in the telomeric DNA damage response.

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

    Directory of Open Access Journals (Sweden)

    Beata Ujvari

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

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

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    João P. Amorim

    2016-09-01

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

  11. Basic domain of telomere guardian TRF2 reduces D-loop unwinding whereas Rap1 restores it.

    Science.gov (United States)

    Necasová, Ivona; Janoušková, Eliška; Klumpler, Tomáš; Hofr, Ctirad

    2017-09-13

    Telomeric repeat binding factor 2 (TRF2) folds human telomeres into loops to prevent unwanted DNA repair and chromosome end-joining. The N-terminal basic domain of TRF2 (B-domain) protects the telomeric displacement loop (D-loop) from cleavage by endonucleases. Repressor activator protein 1 (Rap1) binds TRF2 and improves telomeric DNA recognition. We found that the B-domain of TRF2 stabilized the D-loop and thus reduced unwinding by BLM and RPA, whereas the formation of the Rap1-TRF2 complex restored DNA unwinding. To understand how the B-domain of TRF2 affects DNA binding and D-loop processing, we analyzed DNA binding of full-length TRF2 and a truncated TRF2 construct lacking the B-domain. We quantified how the B-domain improves TRF2's interaction with DNA via enhanced long-range electrostatic interactions. We developed a structural envelope model of the B-domain bound on DNA. The model revealed that the B-domain is flexible in solution but becomes rigid upon binding to telomeric DNA. We proposed a mechanism for how the B-domain stabilizes the D-loop. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  12. Telomere Dynamics in Immune Senescence and Exhaustion Triggered by Chronic Viral Infection

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    Marcia Bellon

    2017-10-01

    Full Text Available The progressive loss of immunological memory during aging correlates with a reduced proliferative capacity and shortened telomeres of T cells. Growing evidence suggests that this phenotype is recapitulated during chronic viral infection. The antigenic volume imposed by persistent and latent viruses exposes the immune system to unique challenges that lead to host T-cell exhaustion, characterized by impaired T-cell functions. These dysfunctional memory T cells lack telomerase, the protein capable of extending and stabilizing chromosome ends, imposing constraints on telomere dynamics. A deleterious consequence of this excessive telomere shortening is the premature induction of replicative senescence of viral-specific CD8+ memory T cells. While senescent cells are unable to expand, they can survive for extended periods of time and are more resistant to apoptotic signals. This review takes a closer look at T-cell exhaustion in chronic viruses known to cause human disease: Epstein–Barr virus (EBV, Hepatitis B/C/D virus (HBV/HCV/HDV, human herpesvirus 8 (HHV-8, human immunodeficiency virus (HIV, human T-cell leukemia virus type I (HTLV-I, human papillomavirus (HPV, herpes simplex virus-1/2(HSV-1/2, and Varicella–Zoster virus (VZV. Current literature linking T-cell exhaustion with critical telomere lengths and immune senescence are discussed. The concept that enduring antigen stimulation leads to T-cell exhaustion that favors telomere attrition and a cell fate marked by enhanced T-cell senescence appears to be a common endpoint to chronic viral infections.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-14

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

  14. Dynamics of Chromatin Silencing at Telomeres: Deterministic and Stochastic Aspects

    Science.gov (United States)

    Apratim, Manjul; Dayarian, Adel; Sontag, Eduardo; Sengupta, Anirvan

    2012-02-01

    Epigenetic silencing modifications of are often associated with well-defined domains. We study potential mechanisms of formation of boundary of silenced regions. We specially focus on the possibility that some telomeric silencing boundaries are formed in a self-organized manner, as opposed to being defined by specific boundary elements. In particular, we examine systems where a titration-induced feedback can stabilize the boundary of the silenced region. A consequence of having multiple such boundaries is large stochastic cell-to-cell variation of boundary locations. We proceed to make an argument about the nature of the fall-off of the average silencing protein occupancy, coming from such variability, and test the predictions against HA-Sir3 ChIP-seq data from experiments performed on yeast.

  15. Short Telomere Load, Telomere Length, and Subclinical Atherosclerosis: The PESA Study.

    Science.gov (United States)

    Fernández-Alvira, Juan M; Fuster, Valentin; Dorado, Beatriz; Soberón, Nora; Flores, Ignacio; Gallardo, Mercedes; Pocock, Stuart; Blasco, María A; Andrés, Vicente

    2016-05-31

    Leucocyte telomere length (LTL) shortening is associated with cardiovascular ischemic events and mortality in humans, but data on its association with subclinical atherosclerosis are scarce. Whether the incidence and severity of subclinical atherosclerosis are associated with the abundance of critically short telomeres, a major trigger of cellular senescence, remains unknown. The authors conducted a cross-sectional exploration of the association between subclinical atherosclerosis burden and both average LTL and the abundance of short telomeres (%LTLSubclinical Atherosclerosis) study. Subclinical atherosclerosis was evaluated by coronary artery calcium scan and 2-dimensional/3-dimensional ultrasound in different aortic territories. Statistical significance of differences among multiple covariates was assessed with linear regression models. Independent associations of telomere parameters with plaque presence were evaluated using general linear models. In men and women, age was inversely associated with LTL (Pearson's r = -0.127, p subclinical atherosclerosis. Longitudinal follow-up of PESA participants will assess long-term associations between telomere length and progression of subclinical atherosclerosis. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  16. The effect of chemotherapeutic agents on telomere length maintenance in breast cancer cell lines

    OpenAIRE

    Motevalli, A; Yasaei, H; Virmouni, SA; Slijepcevic, P; Roberts, T

    2014-01-01

    Copyright @ 2014 the authors. This article is made available through the Brunel Open Access Publishing Fund. It is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. Mammalian telomeric DNA consists of tandem repeats of the sequence TTAGGG associated with a specialized set of proteins, known collectively ...

  17. Telomere Q-PNA-FISH--reliable results from stochastic signals.

    Directory of Open Access Journals (Sweden)

    Andrea Cukusic Kalajzic

    Full Text Available Structural and functional analysis of telomeres is very important for understanding basic biological functions such as genome stability, cell growth control, senescence and aging. Recently, serious concerns have been raised regarding the reliability of current telomere measurement methods such as Southern blot and quantitative polymerase chain reaction. Since telomere length is associated with age related pathologies, including cardiovascular disease and cancer, both at the individual and population level, accurate interpretation of measured results is a necessity. The telomere Q-PNA-FISH technique has been widely used in these studies as well as in commercial analysis for the general population. A hallmark of telomere Q-PNA-FISH is the wide variation among telomere signals which has a major impact on obtained results. In the present study we introduce a specific mathematical and statistical analysis of sister telomere signals during cell culture senescence which enabled us to identify high regularity in their variations. This phenomenon explains the reproducibility of results observed in numerous telomere studies when the Q-PNA-FISH technique is used. In addition, we discuss the molecular mechanisms which probably underlie the observed telomere behavior.

  18. PRL-3 promotes telomere deprotection and chromosomal instability

    Science.gov (United States)

    Meng, Lin; Yang, Yongyong; Ma, Ting; Xing, Xiaofang; Feng, Qin; Song, Qian; Liu, Caiyun; Tian, Zhihua

    2017-01-01

    Abstract Phosphatase of regenerating liver (PRL-3) promotes cell invasiveness, but its role in genomic integrity remains unknown. We report here that shelterin component RAP1 mediates association between PRL-3 and TRF2. In addition, TRF2 and RAP1 assist recruitment of PRL-3 to telomeric DNA. Silencing of PRL-3 in colon cancer cells does not affect telomere integrity or chromosomal stability, but induces reactive oxygen species-dependent DNA damage response and senescence. However, overexpression of PRL-3 in colon cancer cells and primary fibroblasts promotes structural abnormalities of telomeres, telomere deprotection, DNA damage response, chromosomal instability and senescence. Furthermore, PRL-3 dissociates RAP1 and TRF2 from telomeric DNA in vitro and in cells. PRL-3-promoted telomere deprotection, DNA damage response and senescence are counteracted by disruption of PRL-3–RAP1 complex or expression of ectopic TRF2. Examination of clinical samples showed that PRL-3 status positively correlates with telomere deprotection and senescence. PRL-3 transgenic mice exhibit hallmarks of telomere deprotection and senescence and are susceptible to dextran sodium sulfate-induced colon malignancy. Our results uncover a novel role of PRL-3 in tumor development through its adverse impact on telomere homeostasis. PMID:28482095

  19. Telomere length elongation after weight loss intervention in obese adults.

    Science.gov (United States)

    Carulli, L; Anzivino, C; Baldelli, E; Zenobii, M F; Rocchi, M B L; Bertolotti, M

    2016-06-01

    Telomeres may be considered markers of biological aging, shorter telomere length is associated with some age-related diseases; in several studies short telomere length has also been associated to obesity in adults and adolescents. However the relationship between telomere complex functions and obesity is still not clear. Aim of the study was to assess telomere length (TL) in adults' obese subjects before and after weight loss obtained by placement of bioenteric intragastric balloon (BIB) for 6months. We enrolled 42 obese subjects before and after BIB placement as weight loss intervention. Blood samples were collected in order to obtain DNA from leukocyte to measure TL by quantitative PCR. Data were analyzed only in 37 subjects with complete data; all presented important body weight loss (124.06±26.7 vs 105.40±23.14, pweight loss (r=0.44, p=0.007) as well as an inverse correlation between TL at baseline and TL elongation (r=-0.35, p=0.03).The predictors of TL elongation were once again weight loss and short TL at baseline (respectively p=0.007 and p=0.003). Our study shows that weight loss is associated to telomere lengthening in a positive correlation: the greater weight loss the greater telomere lengthening; moreover telomere lengthening is more significant in those subjects with shortest telomeres at baseline. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Live-cell CRISPR imaging in plants reveals dynamic telomere movements.

    Science.gov (United States)

    Dreissig, Steven; Schiml, Simon; Schindele, Patrick; Weiss, Oda; Rutten, Twan; Schubert, Veit; Gladilin, Evgeny; Mette, Michael F; Puchta, Holger; Houben, Andreas

    2017-08-01

    Elucidating the spatiotemporal organization of the genome inside the nucleus is imperative to our understanding of the regulation of genes and non-coding sequences during development and environmental changes. Emerging techniques of chromatin imaging promise to bridge the long-standing gap between sequencing studies, which reveal genomic information, and imaging studies that provide spatial and temporal information of defined genomic regions. Here, we demonstrate such an imaging technique based on two orthologues of the bacterial clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9). By fusing eGFP/mRuby2 to catalytically inactive versions of Streptococcus pyogenes and Staphylococcus aureus Cas9, we show robust visualization of telomere repeats in live leaf cells of Nicotiana benthamiana. By tracking the dynamics of telomeres visualized by CRISPR-dCas9, we reveal dynamic telomere movements of up to 2 μm over 30 min during interphase. Furthermore, we show that CRISPR-dCas9 can be combined with fluorescence-labelled proteins to visualize DNA-protein interactions in vivo. By simultaneously using two dCas9 orthologues, we pave the way for the imaging of multiple genomic loci in live plants cells. CRISPR imaging bears the potential to significantly improve our understanding of the dynamics of chromosomes in live plant cells. © 2017 The Authors The Plant Journal published by John Wiley & Sons Ltd and Society for Experimental Biology.

  1. Telomeres, replicative senescence and human ageing.

    Science.gov (United States)

    Kipling, D

    2001-02-28

    Ageing concerns the extracellular environment and cells that are either post-mitotic or capable of division during life. Primary human cells have a finite division capacity in culture before they enter a state of viable cell cycle arrest termed senescence. Cell division occurs during life in many tissues, either as part of normal tissue function or in response to tissue damage. The accumulation of cells at the end of their replicative lifespan in the elderly might contribute to aged tissue either because of a reduced ability to undergo proliferation or because of the known altered gene-expression patterns of senescent cells. This has been illustrated experimentally using a transgenic telomerase-negative mouse, which shows some premature ageing phenotypes. The mechanism whereby cells count divisions uses the gradual erosion of the ends of chromosomes (telomeres) with cell division caused by the repression of the telomere-maintenance enzyme telomerase in most human cells. Telomere erosion ultimately triggers replicative senescence in many cell types; this can be prevented experimentally by forcibly expressing telomerase. This extends the lifespan of normal human cells and those from progeroid syndromes such as Werner's. Telomere-driven senescence did not evolve to cause ageing, but is instead a by-product of a system devised to provide a tumour-suppression function, a concept that fits well with evolutionary arguments regarding trade-offs between somatic maintenance and reproduction. Work in the future will focus on the development of new animal models to critically address the quantitative significance of this ageing mechanism.

  2. Offspring's leukocyte telomere length, paternal age, and telomere elongation in sperm.

    Directory of Open Access Journals (Sweden)

    Masayuki Kimura

    2008-02-01

    Full Text Available Leukocyte telomere length (LTL is a complex genetic trait. It shortens with age and is associated with a host of aging-related disorders. Recent studies have observed that offspring of older fathers have longer LTLs. We explored the relation between paternal age and offspring's LTLs in 4 different cohorts. Moreover, we examined the potential cause of the paternal age on offspring's LTL by delineating telomere parameters in sperm donors. We measured LTL by Southern blots in Caucasian men and women (n=3365, aged 18-94 years, from the Offspring of the Framingham Heart Study (Framingham Offspring, the NHLBI Family Heart Study (NHLBI-Heart, the Longitudinal Study of Aging Danish Twins (Danish Twins, and the UK Adult Twin Registry (UK Twins. Using Southern blots, Q-FISH, and flow-FISH, we also measured telomere parameters in sperm from 46 young (50 years donors. Paternal age had an independent effect, expressed by a longer LTL in males of the Framingham Offspring and Danish Twins, males and females of the NHLBI-Heart, and females of UK Twins. For every additional year of paternal age, LTL in offspring increased at a magnitude ranging from half to more than twice of the annual attrition in LTL with age. Moreover, sperm telomere length analyses were compatible with the emergence in older men of a subset of sperm with elongated telomeres. Paternal age exerts a considerable effect on the offspring's LTL, a phenomenon which might relate to telomere elongation in sperm from older men. The implications of this effect deserve detailed study.

  3. Oligonucleotide Models of Telomeric DNA and RNA Form a Hybrid G-quadruplex Structure as a Potential Component of Telomeres*

    Science.gov (United States)

    Xu, Yan; Ishizuka, Takumi; Yang, Jie; Ito, Kenichiro; Katada, Hitoshi; Komiyama, Makoto; Hayashi, Tetsuya

    2012-01-01

    Telomeric repeat-containing RNA, a non-coding RNA molecule, has recently been found in mammalian cells. The detailed structural features and functions of the telomeric RNA at human chromosome ends remain unclear, although this RNA molecule may be a key component of the telomere machinery. In this study, using model human telomeric DNA and RNA sequences, we demonstrated that human telomeric RNA and DNA oligonucleotides form a DNA-RNA G-quadruplex. We next employed chemistry-based oligonucleotide probes to mimic the naturally formed telomeric DNA-RNA G-quadruplexes in living cells, suggesting that the process of DNA-RNA G-quadruplex formation with oligonucleotide models of telomeric DNA and RNA could occur in cells. Furthermore, we investigated the possible roles of this DNA-RNA G-quadruplex. The formation of the DNA-RNA G-quadruplex causes a significant increase in the clonogenic capacity of cells and has an effect on inhibition of cellular senescence. Here, we have used a model system to provide evidence about the formation of G-quadruplex structures involving telomeric DNA and RNA sequences that have the potential to provide a protective capping structure for telomere ends. PMID:23012368

  4. Increased brood size leads to persistent eroded telomeres

    Directory of Open Access Journals (Sweden)

    Sophie eReichert

    2014-04-01

    Full Text Available Costs of reproduction can be divided in mandatory costs coming from physiological, metabolic and anatomical changes required to sustain reproduction itself, and in investment-dependent costs that are likely to become apparent when reproductive efforts are exceeding what organisms were prepared to sustain. Interestingly, recent data showed that entering reproduction enhanced breeders’ telomere loss, but no data explored so far the impact of reproductive investment. Telomeres protect the ends of eukaryote chromosomes. Shortened telomeres were associated with shorter lifespan, telomere erosion being then proposed to powerfully quantify life’s insults. Here, we experimentally manipulated brood size in order to modify reproductive investment of adult zebra finches (Taeniopygia guttata below or beyond their (optimal starting investment and tested the consequences of our treatment on parents’ telomere dynamics. We show that an increased brood size led to a reduction in telomere lengths in both parents compared to control and to parents raising a reduced brood. This greater telomere erosion was detected in parents immediately after the reproductive event and the telomere length difference persisted up to one year later. However, we did not detect any effects of brood size manipulation on annual survival of parents kept under laboratory conditions. In addition, telomere lengths at the end of reproduction were not associated with annual survival. Altogether, although our findings highlight that fast telomere erosion can come as a cost of brood size manipulation, they provide mixed correlative support to the emerging hypothesis that telomere erosion could account for the links between high reproductive investment and longevity.

  5. The telomere lengthening conundrum - it could be biology.

    Science.gov (United States)

    Bateson, Melissa; Nettle, Daniel

    2017-04-01

    Longitudinal studies of human leucocyte telomere length often report a percentage of individuals whose telomeres appear to lengthen. However, based on theoretical considerations and empirical data, Steenstrup et al. (Nucleic Acids Research, 2013, vol 41(13): e131) concluded that this lengthening is unlikely to be a real biological phenomenon and is more likely to be an artefact of measurement error. We dispute the logic underlying this claim. We argue that Steenstrup et al.'s analysis is incomplete because it failed to compare predictions derived from assuming a scenario with no true telomere lengthening with alternative scenarios in which true lengthening occurs. To address this deficit, we built a computational model of telomere dynamics that allowed us to compare the predicted percentage of observed telomere length gainers given differing assumptions about measurement error and the true underling dynamics. We modelled a set of scenarios, all assuming measurement error, but both with and without true telomere lengthening. We found a range of scenarios assuming some true telomere lengthening that yielded either similar or better quantitative fits to the empirical data on the percentage of individuals showing apparent telomere lengthening. We conclude that although measurement error contributes to the prevalence of apparent telomere lengthening, Steenstrup et al.'s conclusion was too strong, and current data do not allow us to reject the hypothesis that true telomere lengthening is a real biological phenomenon in epidemiological studies. Our analyses highlight the need for process-level models in the analysis of telomere dynamics. © 2016 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  6. Rapid telomere motions in live human cells analyzed by highly time-resolved microscopy

    Directory of Open Access Journals (Sweden)

    Wang Xueying

    2008-10-01

    Full Text Available Abstract Background Telomeres cap chromosome ends and protect the genome. We studied individual telomeres in live human cancer cells. In capturing telomere motions using quantitative imaging to acquire complete high-resolution three-dimensional datasets every second for 200 seconds, telomere dynamics were systematically analyzed. Results The motility of individual telomeres within the same cancer cell nucleus was widely heterogeneous. One class of internal heterochromatic regions of chromosomes analyzed moved more uniformly and showed less motion and heterogeneity than telomeres. The single telomere analyses in cancer cells revealed that shorter telomeres showed more motion, and the more rapid telomere motions were energy dependent. Experimentally increasing bulk telomere length dampened telomere motion. In contrast, telomere uncapping, but not a DNA damaging agent, methyl methanesulfonate, significantly increased telomere motion. Conclusion New methods for seconds-scale, four-dimensional, live cell microscopic imaging and data analysis, allowing systematic tracking of individual telomeres in live cells, have defined a previously undescribed form of telomere behavior in human cells, in which the degree of telomere motion was dependent upon telomere length and functionality.

  7. Telomeric Retrotransposon HeT-A Contains a Bidirectional Promoter that Initiates Divergent Transcription of piRNA Precursors in Drosophila Germline.

    Science.gov (United States)

    Radion, Elizaveta; Ryazansky, Sergei; Akulenko, Natalia; Rozovsky, Yakov; Kwon, Dmitry; Morgunova, Valeriya; Olovnikov, Ivan; Kalmykova, Alla

    2017-10-27

    PIWI-interacting RNAs (piRNAs) provide the silencing of transposable elements in the germline. Drosophila telomeres are maintained by transpositions of specialized telomeric retroelements. piRNAs generated from sense and antisense transcripts of telomeric elements provide telomere length control in the germline. Previously, we have found that antisense transcription of the major telomeric retroelement HeT-A is initiated upstream of the HeT-A sense transcription start site. Here, we performed a deletion analysis of the HeT-A promoter and show that common regulatory elements are shared by sense and antisense promoters of HeT-A. Therefore, the HeT-A promoter is a bidirectional promoter capable of processive sense and antisense transcription. Ovarian small RNA data show that a solo HeT-A promoter within an euchromatic transgene initiates the divergent transcription of transgenic reporter genes and subsequent processing of these transcripts into piRNAs. These events lead to the formation of a divergent unistrand piRNA cluster at solo HeT-A promoters, in contrast to endogenous telomeres that represent strong dual-strand piRNA clusters. Solo HeT-A promoters are not immunoprecipitated with heterochromatin protein 1 (HP1) homolog Rhino, a marker of the dual-strand piRNA clusters, but are associated with HP1 itself, which provides piRNA-mediated transcriptional repression of the reporter genes. Unlike endogenous dual-strand piRNA clusters, the solo HeT-A promoter does not produce overlapping transcripts. In a telomeric context, however, bidirectional promoters of tandem HeT-A repeats provide a read-through transcription of both genomic strands, followed by Rhi binding. These data indicate that Drosophila telomeres share properties of unistrand and dual-strand piRNA clusters. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Live cell CRISPR-imaging in plants reveals dynamic telomere movements

    KAUST Repository

    Dreissig, Steven

    2017-05-16

    Elucidating the spatio-temporal organization of the genome inside the nucleus is imperative to understand the regulation of genes and non-coding sequences during development and environmental changes. Emerging techniques of chromatin imaging promise to bridge the long-standing gap between sequencing studies which reveal genomic information and imaging studies that provide spatial and temporal information of defined genomic regions. Here, we demonstrate such an imaging technique based on two orthologues of the bacterial CRISPR-Cas9 system. By fusing eGFP/mRuby2 to the catalytically inactive version of Streptococcus pyogenes and Staphylococcus aureus Cas9, we show robust visualization of telomere repeats in live leaf cells of Nicotiana benthamiana. By tracking the dynamics of telomeres visualized by CRISPR-dCas9, we reveal dynamic telomere movements of up to 2 μm within 30 minutes during interphase. Furthermore, we show that CRISPR-dCas9 can be combined with fluorescence-labelled proteins to visualize DNA-protein interactions in vivo. By simultaneously using two dCas9 orthologues, we pave the way for imaging of multiple genomic loci in live plants cells. CRISPR-imaging bears the potential to significantly improve our understanding of the dynamics of chromosomes in live plant cells.

  9. The effect of the TRF2 N-terminal and TRFH regions on telomeric G-quadruplex structures.

    Science.gov (United States)

    Pedroso, Ilene M; Hayward, William; Fletcher, Terace M

    2009-04-01

    The sequence of human telomeric DNA consists of tandem repeats of 5'-d(TTAGGG)-3'. This guanine-rich DNA can form G-quadruplex secondary structures which may affect telomere maintenance. A current model for telomere protection by the telomere-binding protein, TRF2, involves the formation of a t-loop which is stabilized by a strand invasion-like reaction. This type of reaction may be affected by G-quadruplex structures. We analyzed the influence of the arginine-rich, TRF2 N-terminus (TRF2(B)), as well as this region plus the TRFH domain of TRF2 (TRF2(BH)), on the structure of G-quadruplexes. Circular dichroism results suggest that oligonucleotides with 4, 7 and 8 5'-d(TTAGGG)-3' repeats form hybrid structures, a mix of parallel/antiparallel strand orientation, in K(+). TRF2(B) stimulated the formation of parallel-stranded structures and, in some cases, intermolecular structures. TRF2(BH) also stimulated intermolecular but not parallel-stranded structures. Only full-length TRF2 and TRF2(BH) stimulated uptake of a telomeric single-stranded oligonucleotide into a plasmid containing telomeric DNA in the presence of K(+). The results in this study suggest that G-quadruplex formation inhibits oligonucleotide uptake into the plasmid, but the inhibition can be overcome by TRF2. This study is the first analysis of the effects of TRF2 domains on G-quadruplex structures and has implications for the role of G-quadruplexes and TRF2 in the formation of t-loops.

  10. Acute coronary syndrome: Role of the telomere dynamic

    African Journals Online (AJOL)

    USER

    2010-05-03

    May 3, 2010 ... telomeres showed an inverse correlation with pulse pressure, biologic marker of vascular aging and predictor of increased mortality rate, in men (Benetos, 2001). This relation was inconsistent in females (Benetos, 2001). Effects of telomere length on the future cardiovascular risks have been determined in ...

  11. Common variants near TERC are associated with mean telomere length

    NARCIS (Netherlands)

    Codd, Veryan; Mangino, Massimo; van der Harst, Pim; Braund, Peter S.; Kaiser, Michael; Beveridge, Alan J.; Rafelt, Suzanne; Moore, Jasbir; Nelson, Chris; Soranzo, Nicole; Zhai, Guangju; Valdes, Ana M.; Blackburn, Hannah; Mateo Leach, Irene; de Boer, Rudolf A.; Goodall, Alison H.; Ouwehand, Willem; van Veldhuisen, Dirk J.; van Gilst, Wiek H.; Navis, Gerjan; Burton, Paul R.; Tobin, Martin D.; Hall, Alistair S.; Thompson, John R.; Spector, Tim; Samani, Nilesh J.

    We conducted genome-wide association analyses of mean leukocyte telomere length in 2,917 individuals, with follow-up replication in 9,492 individuals. We identified an association with telomere length on 3q26 (rs12696304, combined P = 3.72 x 10(-14)) at a locus that includes TERC, which encodes the

  12. Acute coronary syndrome: Role of the telomere dynamic

    African Journals Online (AJOL)

    USER

    2010-05-03

    May 3, 2010 ... Telomeres, or historically named "terminal genes" are first discovered by Muller working on fruit fly in. 1930s. Since then, the great progress was made in understanding the consequences of telomere erosion on the human health and disease states, as age related vascular diseases. The overlapping.

  13. Telomeres and HIV-1 infection: in search of exhaustion

    NARCIS (Netherlands)

    Wolthers, K. C.; Miedema, F.

    1998-01-01

    Telomere length analysis could be helpful in determining if exhaustion and replicative senescence are involved in HIV-1 pathogenesis. Evidence that CD8+ T cells have shorter telomeres may point towards an increased turnover of CD8+ T cells and exhaustion of the CD8+ T-cell responses in HIV-1

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

    NARCIS (Netherlands)

    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

  15. Gender and telomere length : Systematic review and meta-analysis

    NARCIS (Netherlands)

    Gardner, Michael; Bann, David; Wiley, Laura; Cooper, Rachel; Hardy, Rebecca; Nitsch, Dorothea; Martin-Ruiz, Carmen; Shiels, Paul; Sayer, Avan Aihie; Barbieri, Michelangela; Bekaert, Sofie; Bischoff, Claus; Brooks-Wilson, Angela; Chen, Wei; Cooper, Cyrus; Christensen, Kaare; De Meyer, Tim; Deary, Ian; Der, Geoff; Roux, Ana Diez; Fitzpatrick, Annette; Hajat, Anjum; Halaschek-Wiener, Julius; Harris, Sarah; Hunt, Steven C.; Jagger, Carol; Jeon, Hyo-Sung; Kaplan, Robert; Kimura, Masayuki; Lansdorp, Peter; Li, Changyong; Maeda, Toyoki; Mangino, Massimo; Nawrot, Tim S.; Nilsson, Peter; Nordfjall, Katarina; Paolisso, Giuseppe; Ren, Fu; Riabowol, Karl; Robertson, Tony; Roos, Goran; Staessen, Jan A.; Spector, Tim; Tang, Nelson; Unryn, Brad; van der Harst, Pim; Woo, Jean; Xing, Chao; Yadegarfar, Mohammad E.; Park, Jae Yong; Young, Neal; Kuh, Diana; von Zglinicki, Thomas; Ben-Shlomo, Yoav

    Background: It is widely believed that females have longer telomeres than males, although results from studies have been contradictory. Methods: We carried out a systematic review and meta-analyses to test the hypothesis that in humans, females have longer telomeres than males and that this

  16. Quantitative theory of telomere length regulation and cellular senescence.

    Science.gov (United States)

    Rodriguez-Brenes, Ignacio A; Peskin, Charles S

    2010-03-23

    In normal somatic cells, telomere length shortens with each cell replication. This progressive shortening is associated with cellular senescence and apoptosis. Germ cells, stem cells, and the majority of cancer cells express telomerase, an enzyme that extends telomere length and, when expressed at sufficient levels, can immortalize or extend the life span of a cell line. It is believed that telomeres switch between two states: capped and uncapped. The telomere state determines its accessibility to telomerase and also the onset of senescence. One hypothesis is that the t loop, a large lariat-like structure, represents the capped state. In this paper we model a telomere state on the basis of the biophysics of t-loop formation, allowing us to develop a single mathematical model that accounts for two processes: telomere length regulation for telomerase positive cells and cellular senescence in somatic cells. The model predicts the steady-state length distribution for telomerase positive cells, describes the time evolution of telomere length, and computes the life span of a cell line on the basis of the levels of TRF2 and telomerase expression. The model reproduces a wide range of experimental behavior and fits data from immortal cell lines (HeLa S3 and 293T) and somatic cells (human diploid fibroblasts) well. We conclude that the t loop as the capped state is a quantitatively reasonable model of telomere length regulation and cellular senescence.

  17. Telomere Length – a New Biomarker in Medicine

    Directory of Open Access Journals (Sweden)

    Agnieszka Kozłowska

    2015-12-01

    Full Text Available A number of xenobiotics in the environment and workplace influences on our health and life. Biomarkers are tools for measuring such exposures and their effects in the organism. Nowadays, telomere length, epigenetic changes, mutations and changes in gene expression pattern have become new molecular biomarkers. Telomeres play the role of molecular clock, which influences on expectancy of cell life and thus aging, the formation of damages, development diseases and carcinogenesis. The telomere length depends on mechanisms of replication and the activity of telomerase. Telomere length is currently used as a biomarker of susceptibility and/or exposure. This paper describes the role of telomere length as a biomarker of aging cells, oxidative stress, a marker of many diseases including cancer, and as a marker of environmental and occupational exposure.

  18. Telomere Replication Stress Induced by POT1 Inactivation Accelerates Tumorigenesis

    Directory of Open Access Journals (Sweden)

    Alexandra M. Pinzaru

    2016-06-01

    Full Text Available Genome sequencing studies have revealed a number of cancer-associated mutations in the telomere-binding factor POT1. Here, we show that when combined with p53 deficiency, depletion of murine POT1a in common lymphoid progenitor cells fosters genetic instability, accelerates the onset, and increases the severity of T cell lymphomas. In parallel, we examined human and mouse cells carrying POT1 mutations found in cutaneous T cell lymphoma (CTCL patients. Inhibition of POT1 activates ATR-dependent DNA damage signaling and induces telomere fragility, replication fork stalling, and telomere elongation. Our data suggest that these phenotypes are linked to impaired CST (CTC1-STN1-TEN1 function at telomeres. Lastly, we show that proliferation of cancer cells lacking POT1 is enabled by the attenuation of the ATR kinase pathway. These results uncover a role for defective telomere replication during tumorigenesis.

  19. Sub-fertile sperm cells exemplify telomere dysfunction.

    Science.gov (United States)

    Biron-Shental, Tal; Wiser, Amir; Hershko-Klement, Anat; Markovitch, Ofer; Amiel, Aliza; Berkovitch, Arie

    2017-09-13

    The purpose of this study was to evaluate telomere homeostasis in sub-fertile compared to fertile human sperm. This observational, comparative study included 16 sub-fertile men who required intracytoplasmic sperm injection and 10 fertile men. At least 100 sperm cells from each participant were assessed. Main outcome measures were telomere length and telomere aggregates. Telomerase RNA component (TERC) copy number and telomere capture were assessed using fluorescence in situ hybridization technique and human telomerase reverse transcriptase (hTERT) using immunohistochemistry. Clinical backgrounds were similar. The percentage of sperm cells with shorter telomeres was higher among the sub-fertile compared to the fertile participants (3.3 ± 3.1 vs. 0.6 ± 1.2%, respectively; P < 0.005). The percentage of cells with telomere aggregates was significantly higher in the sub-fertile group (15.12 ± 3.73 vs. 4.73 ± 3.73%; P < 0.005). TERC gene copy number was similar between groups. The percentage of cells that were positive for hTERT was lower in the sub-fertile group (3.81 ± 1.27 vs. 8.42 ± 1.80%; P < 0.005). Telomere capture rates were higher among the sub-fertile sperm cells (P < 0.005). Sub-fertile sperm cells have short telomeres that are elongated by the alternative pathway of telomere capture. Dysfunctional telomeres may affect sperm fertilizability.

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

    Science.gov (United States)

    Boardman, Lisa A; Johnson, Ruth A; Viker, Kimberly B; Hafner, Kari A; Jenkins, Robert B; Riegert-Johnson, Douglas L; Smyrk, Thomas C; Litzelman, Kristin; Seo, Songwon; Gangnon, Ronald E; Engelman, Corinne D; Rider, David N; Vanderboom, Russell J; Thibodeau, Stephen N; Petersen, Gloria M; Skinner, Halcyon G

    2013-01-01

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

  1. Father Loss and Child Telomere Length.

    Science.gov (United States)

    Mitchell, Colter; McLanahan, Sara; Schneper, Lisa; Garfinkel, Irv; Brooks-Gunn, Jeanne; Notterman, Daniel

    2017-08-01

    Father loss during childhood has negative health and behavioral consequences, but the biological consequences are unknown. Our goal was to examine how father loss (because of separation and/or divorce, death, or incarceration) is associated with cellular function as estimated by telomere length. Data come from the 9-year follow-up of the Fragile Families and Child Wellbeing Study, a birth cohort study of children in 20 large American cities (N = 2420). Principal measures are as follows: salivary telomere length (sTL), mother reports of father loss, and polymorphisms in genes related to serotonergic and dopaminergic signaling. At 9 years of age, children with father loss have significantly shorter telomeres (14% reduction). Paternal death has the largest association (16%), followed by incarceration (10%), and separation and/or divorce (6%). Changes in income partially mediate these associations (95% mediation for separation and/or divorce, 30% for incarceration, and 25% for death). Effects are 40% greater for boys and 90% greater for children with the most reactive alleles of the serotonin transporter genes when compared with those with the least reactive alleles. No differences were found by age at father loss or a child's race/ethnicity. Father loss has a significant association with children's sTL, with the death of a father showing the largest effect. Income loss explains most of the association between child sTL and separation and/or divorce but much less of the association with incarceration or death. This underscores the important role of fathers in the care and development of children and supplements evidence of the strong negative effects of parental incarceration. Copyright © 2017 by the American Academy of Pediatrics.

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

    Directory of Open Access Journals (Sweden)

    Lisa A Boardman

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

  3. TRF2 Protein Interacts with Core Histones to Stabilize Chromosome Ends*

    Science.gov (United States)

    Izumi, Takashi; Shimizu, Shigeomi

    2016-01-01

    Mammalian chromosome ends are protected by a specialized nucleoprotein complex called telomeres. Both shelterin, a telomere-specific multi-protein complex, and higher order telomeric chromatin structures combine to stabilize the chromosome ends. Here, we showed that TRF2, a component of shelterin, binds to core histones to protect chromosome ends from inappropriate DNA damage response and loss of telomeric DNA. The N-terminal Gly/Arg-rich domain (GAR domain) of TRF2 directly binds to the globular domain of core histones. The conserved arginine residues in the GAR domain of TRF2 are required for this interaction. A TRF2 mutant with these arginine residues substituted by alanine lost the ability to protect telomeres and induced rapid telomere shortening caused by the cleavage of a loop structure of the telomeric chromatin. These findings showed a previously unnoticed interaction between the shelterin complex and nucleosomal histones to stabilize the chromosome ends. PMID:27514743

  4. Cancer cells with alternative lengthening of telomeres do not display a general hypersensitivity to ATR inhibition

    Directory of Open Access Journals (Sweden)

    Katharina I Deeg

    2016-08-01

    Full Text Available Telomere maintenance is a hallmark of cancer as it provides cancer cells with cellular immortality. A significant fraction of tumors uses the alternative lengthening of telomeres (ALT pathway to elongate their telomeres and to gain an unlimited proliferation potential. Since the ALT pathway is unique to cancer cells, it represents a potentially valuable, currently unexploited target for anticancer therapies. Recently, it was proposed that ALT renders cells hypersensitive to ataxia telangiectasia- and RAD3-related (ATR protein inhibitors (Flynn et al., Science 347, 273. Here, we measured the response of various ALT or telomerase positive cell lines to the ATR inhibitor VE-821. In addition, we compared the effect of the inhibitor on cell viability in isogenic cell lines, in which ALT was active or suppressed. In these experiments a general ATR inhibitor sensitivity of cells with ALT could not be confirmed. We rather propose that the observed variations in sensitivity reflect differences between cell lines that are unrelated to ALT.

  5. A distinct type of heterochromatin at the telomeric region of the Drosophila melanogaster Y chromosome.

    Directory of Open Access Journals (Sweden)

    Sidney H Wang

    Full Text Available Heterochromatin assembly and its associated phenotype, position effect variegation (PEV, provide an informative system to study chromatin structure and genome packaging. In the fruit fly Drosophila melanogaster, the Y chromosome is entirely heterochromatic in all cell types except the male germline; as such, Y chromosome dosage is a potent modifier of PEV. However, neither Y heterochromatin composition, nor its assembly, has been carefully studied. Here, we report the mapping and characterization of eight reporter lines that show male-specific PEV. In all eight cases, the reporter insertion sites lie in the telomeric transposon array (HeT-A and TART-B2 homologous repeats of the Y chromosome short arm (Ys. Investigations of the impact on the PEV phenotype of mutations in known heterochromatin proteins (i.e., modifiers of PEV show that this Ys telomeric region is a unique heterochromatin domain: it displays sensitivity to mutations in HP1a, EGG and SU(VAR3-9, but no sensitivity to Su(z2 mutations. It appears that the endo-siRNA pathway plays a major targeting role for this domain. Interestingly, an ectopic copy of 1360 is sufficient to induce a piRNA targeting mechanism to further enhance silencing of a reporter cytologically localized to the Ys telomere. These results demonstrate the diversity of heterochromatin domains, and the corresponding variation in potential targeting mechanisms.

  6. Associations of Leukocyte Telomere Length With Aerobic and Muscular Fitness in Young Adults.

    Science.gov (United States)

    Williams, Dylan M; Buxton, Jessica L; Kantomaa, Marko T; Tammelin, Tuija H; Blakemore, Alexandra I F; Järvelin, Marjo-Riitta

    2017-04-01

    Decline in both telomere length and physical fitness over the life course may contribute to increased risk of several chronic diseases. The relationship between telomere length and aerobic and muscular fitness is not well characterized. We examined whether there are cross-sectional associations of mean relative leukocyte telomere length (LTL) with objective measures of aerobic fitness, muscle strength, and muscle endurance, using data on 31-year-old participants of the Northern Finland Birth Cohort 1966 (n = 4,952-5,205, varying by exposure-outcome analysis). Aerobic fitness was assessed by means of heart rate measurement following a standardized submaximal step test; muscular fitness was assessed by means of a maximal isometric handgrip strength test and a test of lower-back trunk muscle endurance. Longer LTL was associated with higher aerobic fitness and better trunk muscle endurance in models including adjustment for age, sex, body mass index, socioeconomic position, diet, smoking, alcohol consumption, physical activity level, and C-reactive protein. In a sex-stratified analysis, LTL was not associated with handgrip strength in either men or women. LTL may relate to aspects of physical fitness in young adulthood, but replication of these findings is required, along with further studies to help assess directions and causality in these associations. © The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health.

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

    Directory of Open Access Journals (Sweden)

    Mauricio Valerio-Santiago

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Habib, Ahmed G K; Masuda, Kenta; Yukawa, Masashi; Tsuchiya, Eiko; Ueno, Masaru

    2015-08-14

    Protection of telomere (Pot1) is a single-stranded telomere binding protein which is essential for chromosome ends protection. Fission yeast Rqh1 is a member of RecQ helicases family which has essential roles in the maintenance of genomic stability and regulation of homologous recombination. Double mutant between fission yeast pot1Δ and rqh1 helicase dead (rqh1-hd) maintains telomere by homologous recombination. In pot1Δ rqh1-hd double mutant, recombination intermediates accumulate near telomere which disturb chromosome segregation and make cells sensitive to microtubule inhibitors thiabendazole (TBZ). Deletion of chk1(+) or mutation of its kinase domain shortens the G2 of pot1Δ rqh1-hd double mutant and suppresses both the accumulation of recombination intermediates and the TBZ sensitivity of that double mutant. In this study, we asked whether the long G2 is the reason for the TBZ sensitivity of pot1Δ rqh1-hd double mutant. We found that shortening the G2 of pot1Δ rqh1-hd double mutant by additional mutations of wee1 and mik1 or gain of function mutation of Cdc2 suppresses both the accumulation of recombination intermediates and the TBZ sensitivity of pot1Δ rqh1-hd double mutant. Our results suggest that long G2 of pot1Δ rqh1-hd double mutant may allow time for the accumulation of recombination intermediates which disturb chromosome segregation and make cells sensitive to TBZ. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Telomerase efficiently elongates highly transcribing telomeres in human cancer cells.

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    Benjamin O Farnung

    Full Text Available RNA polymerase II transcribes the physical ends of linear eukaryotic chromosomes into a variety of long non-coding RNA molecules including telomeric repeat-containing RNA (TERRA. Since TERRA discovery, advances have been made in the characterization of TERRA biogenesis and regulation; on the contrary its associated functions remain elusive. Most of the biological roles so far proposed for TERRA are indeed based on in vitro experiments carried out using short TERRA-like RNA oligonucleotides. In particular, it has been suggested that TERRA inhibits telomerase activity. We have exploited two alternative cellular systems to test whether TERRA and/or telomere transcription influence telomerase-mediated telomere elongation in human cancer cells. In cells lacking the two DNA methyltransferases DNMT1 and DNMT3b, TERRA transcription and steady-state levels are greatly increased while telomerase is able to elongate telomeres normally. Similarly, telomerase can efficiently elongate transgenic inducible telomeres whose transcription has been experimentally augmented. Our data challenge the current hypothesis that TERRA functions as a general inhibitor of telomerase and suggest that telomere length homeostasis is maintained independently of TERRA and telomere transcription.

  11. Relationship between interpersonal sensitivity and leukocyte telomere length.

    Science.gov (United States)

    Suzuki, Akihito; Matsumoto, Yoshihiko; Enokido, Masanori; Shirata, Toshinori; Goto, Kaoru; Otani, Koichi

    2017-10-10

    Telomeres are repetitive DNA sequences located at the ends of chromosomes, and telomere length represents a biological marker for cellular aging. Interpersonal sensitivity, excessive sensitivity to the behavior and feelings of others, is one of the vulnerable factors to depression. In the present study, we examined the effect of interpersonal sensitivity on telomere length in healthy subjects. The subjects were 159 unrelated healthy Japanese volunteers. Mean age ± SD (range) of the subjects was 42.3 ± 7.8 (30-61) years. Interpersonal sensitivity was assessed by the Japanese version of the Interpersonal Sensitivity Measure (IPSM). Leukocyte telomere length was determined by a quantitative real-time PCR method. Higher scores of the total IPSM were significantly (β = -0.163, p = 0.038) related to shorter telomere length. In the sub-scale analysis, higher scores of timidity were significantly (β = -0.220, p = 0.044) associated with shorter telomere length. The present study suggests that subjects with higher interpersonal sensitivity have shorter leukocyte telomere length, implying that interpersonal sensitivity has an impact on cellular aging.

  12. Worldwide genetic structure in 37 genes important in telomere biology

    Science.gov (United States)

    Mirabello, L; Yeager, M; Chowdhury, S; Qi, L; Deng, X; Wang, Z; Hutchinson, A; Savage, S A

    2012-01-01

    Telomeres form the ends of eukaryotic chromosomes and are vital in maintaining genetic integrity. Telomere dysfunction is associated with cancer and several chronic diseases. Patterns of genetic variation across individuals can provide keys to further understanding the evolutionary history of genes. We investigated patterns of differentiation and population structure of 37 telomere maintenance genes among 53 worldwide populations. Data from 898 unrelated individuals were obtained from the genome-wide scan of the Human Genome Diversity Panel (HGDP) and from 270 unrelated individuals from the International HapMap Project at 716 single-nucleotide polymorphism (SNP) loci. We additionally compared this gene set to HGDP data at 1396 SNPs in 174 innate immunity genes. The majority of the telomere biology genes had low to moderate haplotype diversity (45–85%), high ancestral allele frequencies (>60%) and low differentiation (FST HapMap 3. TERT had higher than expected levels of haplotype diversity, likely attributable to a lack of linkage disequilibrium, and a potential cancer-associated SNP in this gene, rs2736100, varied substantially in genotype frequency across major continental regions. It is possible that the genes under selection could influence telomere biology diseases. As a group, there appears to be less diversity and differentiation in telomere biology genes than in genes with different functions, possibly due to their critical role in telomere maintenance and chromosomal stability. PMID:21731055

  13. The relationship between telomere length and beekeeping among Malaysians.

    Science.gov (United States)

    Nasir, Nurul Fatihah Mohamad; Kannan, Thirumulu Ponnuraj; Sulaiman, Siti Amrah; Shamsuddin, Shaharum; Azlina, Ahmad; Stangaciu, Stefan

    2015-06-01

    The belief that beekeepers live longer than anyone else is present since ages. However, no research has been done to explore the longevity of life in beekeepers. Here, we investigated the telomere length in 30 male beekeepers and 30 male non-beekeepers and associated them with the longevity of life using Southern analysis of terminal restriction fragments (TRFs) generated by Hinf I/Rsa I digestion of human genomic DNA using TeloTAGGG Telomere Length Assay. Interestingly, we found that the telomere length of male beekeepers was significantly longer than those of male non-beekeepers with a p value of less than 0.05, suggesting that beekeepers may have longer life compared to non-beekeepers. We further found that the consumption of bee products for a long period and frequent consumption of bee products per day are associated with telomere length. An increase of year in consuming bee products is associated with a mean increase in telomere length of 0.258 kbp. In addition, an increase in frequency of eating bee products per day was also associated with a mean increase of 2.66 kbp in telomere length. These results suggested that bee products might play some roles in telomere length maintenance.

  14. Telomere Length and the Cancer–Atherosclerosis Trade-Off

    Science.gov (United States)

    Stone, Rivka C.; Horvath, Kent; Kark, Jeremy D.; Susser, Ezra; Tishkoff, Sarah A.; Aviv, Abraham

    2016-01-01

    Modern humans, the longest-living terrestrial mammals, display short telomeres and repressed telomerase activity in somatic tissues compared with most short-living small mammals. The dual trait of short telomeres and repressed telomerase might render humans relatively resistant to cancer compared with short-living small mammals. However, the trade-off for cancer resistance is ostensibly increased age-related degenerative diseases, principally in the form of atherosclerosis. In this communication, we discuss (a) the genetics of human telomere length, a highly heritable complex trait that is influenced by genetic ancestry, sex, and paternal age at conception, (b) how cancer might have played a role in the evolution of telomere biology across mammals, (c) evidence that in modern humans telomere length is a determinant (rather than only a biomarker) of cancer and atherosclerosis, and (d) the potential influence of relatively recent evolutionary forces in fashioning the variation in telomere length across and within populations, and their likely lasting impact on major diseases in humans. Finally, we propose venues for future research on human telomere genetics in the context of its potential role in shaping the modern human lifespan. PMID:27386863

  15. Nickel enhances telomeric silencing in Saccharomyces cerevisiae.

    Science.gov (United States)

    Broday, L; Cai, J; Costa, M

    1999-04-06

    Certain nickel compounds including crystalline nickel sulfide (NiS) and subsulfide (Ni3S2) are potent human and animal carcinogens. In Chinese hamster embryo cells, an X-linked senescence gene was inactivated following nickel-induced DNA methylation. Nickel also induced the inactivation of the gpt reporter gene by chromatin condensation and a DNA methylation process in a transgenic gpt+ Chinese hamster cell line (G12), which is located near a heterochromatic region. To determine if nickel can cause gene silencing independently of DNA methylation, based only on the induction of changes in chromatin structure, we measured its effect on gene silencing in Saccharomyces cerevisiae. Growth of yeast in the presence of nickel chloride repressed a telomeric marker gene (URA3) and resulted in a stable epigenetic switch. This phenomenon was dependent on the number of cell doubling prior to selection and also on the distance of the marker gene from the end of the chromosome. The level of TPE (telomeric position effect) increased linearly with elevations of nickel concentration. Addition of magnesium inhibited this effect, but magnesium did not silence the reporter gene by itself. The level of silencing was also assessed following treatment with other transition metals: cobalt, copper and cadmium. In the sublethal range, cobalt induced similar effects as nickel, while copper and cadmium did not change the basal level of gene expression. Silencing by copper and cadmium were evident only at concentrations of those metals where the viability was very low. Copyright 1999 Elsevier Science B.V.

  16. Aberrant leukocyte telomere length in Birdshot Uveitis.

    Directory of Open Access Journals (Sweden)

    Nadia Vazirpanah

    Full Text Available Birdshot Uveitis (BU is an archetypical chronic inflammatory eye disease, with poor visual prognosis, that provides an excellent model for studying chronic inflammation. BU typically affects patients in the fifth decade of life. This suggests that it may represent an age-related chronic inflammatory disease, which has been linked to increased erosion of telomere length of leukocytes.To study this in detail, we exploited a sensitive standardized quantitative real-time polymerase chain reaction to determine the peripheral blood leukocyte telomere length (LTL in 91 genotyped Dutch BU patients and 150 unaffected Dutch controls.Although LTL erosion rates were very similar between BU patients and healthy controls, we observed that BU patients displayed longer LTL, with a median of log (LTL = 4.87 (= 74131 base pair compared to 4.31 (= 20417 base pair in unaffected controls (P<0.0001. The cause underpinning the difference in LTL could not be explained by clinical parameters, immune cell-subtype distribution, nor genetic predisposition based upon the computed weighted genetic risk score of genotyped validated variants in TERC, TERT, NAF1, OBFC1 and RTEL1.These findings suggest that BU is accompanied by significantly longer LTL.

  17. Telomere length and cortisol reactivity in children of depressed mothers.

    Science.gov (United States)

    Gotlib, I H; LeMoult, J; Colich, N L; Foland-Ross, L C; Hallmayer, J; Joormann, J; Lin, J; Wolkowitz, O M

    2015-05-01

    A growing body of research demonstrates that individuals diagnosed with major depressive disorder (MDD) are characterized by shortened telomere length, which has been posited to underlie the association between depression and increased instances of medical illness. The temporal nature of the relation between MDD and shortened telomere length, however, is not clear. Importantly, both MDD and telomere length have been associated independently with high levels of stress, implicating dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and anomalous levels of cortisol secretion in this relation. Despite these associations, no study has assessed telomere length or its relation with HPA-axis activity in individuals at risk for depression, before the onset of disorder. In the present study, we assessed cortisol levels in response to a laboratory stressor and telomere length in 97 healthy young daughters of mothers either with recurrent episodes of depression (i.e., daughters at familial risk for depression) or with no history of psychopathology. We found that daughters of depressed mothers had shorter telomeres than did daughters of never-depressed mothers and, further, that shorter telomeres were associated with greater cortisol reactivity to stress. This study is the first to demonstrate that children at familial risk of developing MDD are characterized by accelerated biological aging, operationalized as shortened telomere length, before they had experienced an onset of depression; this may predispose them to develop not only MDD but also other age-related medical illnesses. It is critical, therefore, that we attempt to identify and distinguish genetic and environmental mechanisms that contribute to telomere shortening.

  18. BRCA1 in the DNA damage response and at telomeres

    Directory of Open Access Journals (Sweden)

    Eliot Michael Rosen

    2013-06-01

    Full Text Available Abstract. Mutations of the breast and ovarian cancer susceptibility gene 1 (BRCA1 account for about 40-45% of hereditary breast cancer cases. Moreover, a significant fraction of sporadic (non-hereditary breast and ovarian cancers exhibit reduced or absent expression of the BRCA1 protein, suggesting an additional role for BRCA1 in sporadic cancers. BRCA1 follows the classic pattern of a highly penetrant Knudsen-type tumor suppressor gene in which one allele is inactivated through a germ-line mutation and the other is mutated or deleted within the tumor. BRCA1 is a multi-functional protein but it is not fully understood which function(s is (are most important for tumor suppression, nor is it clear why BRCA1 mutations confer a high risk for breast and ovarian cancers and not a broad spectrum of tumor types. Here, we will review BRCA1 functions in the DNA damage response (DDR, which are likely to contribute to tumor suppression. In the process, we will highlight some of the controversies and unresolved issues in the field. We will also describe a recently identified and under-investigated role for BRCA1 in the regulation of telomeres and the implications of this role in the DDR and cancer suppression.

  19. Heat shock-induced dissociation of TRF2 from telomeres does not initiate a telomere-dependent DNA damage response.

    Science.gov (United States)

    Petrova, Nadezhda V; Velichko, Artem K; Kantidze, Omar L; Razin, Sergey V

    2014-05-01

    Telomeric repeat binding factor 2 (TRF2) is a well-studied shelterin complex subunit that plays a major role in the protection of chomosome ends and the prevention of the telomere-associated DNA damage response. We show that heat shock induces the dissociation of TRF2 from telomeres in human primary and cancer cell cultures. TRF2 is not simply degraded in response to heat shock, but redistributed thoughout the nucleoplasm. This TRF2 depletion/redistribution does not initiate the DNA damage response at chomosome termini. © 2014 International Federation for Cell Biology.

  20. Highly Aggressive Metastatic Melanoma Cells Unable to Maintain Telomere Length.

    Science.gov (United States)

    Viceconte, Nikenza; Dheur, Marie-Sophie; Majerova, Eva; Pierreux, Christophe E; Baurain, Jean-François; van Baren, Nicolas; Decottignies, Anabelle

    2017-06-20

    Unlimited replicative potential is one of the hallmarks of cancer cells. In melanoma, hTERT (telomerase reverse transcriptase) is frequently overexpressed because of activating mutations in its promoter, suggesting that telomerase is necessary for melanoma development. We observed, however, that a subset of melanoma metastases and derived cell lines had no telomere maintenance mechanism. Early passages of the latter displayed long telomeres that progressively shortened and fused before cell death. We propose that, during melanoma formation, oncogenic mutations occur in precursor melanocytes with long telomeres, providing cells with sufficient replicative potential, thereby bypassing the need to re-activate telomerase. Our data further support the emerging idea that long telomeres promote melanoma formation. These observations are important when considering anticancer therapies targeting telomerase. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  1. Highly Aggressive Metastatic Melanoma Cells Unable to Maintain Telomere Length

    Directory of Open Access Journals (Sweden)

    Nikenza Viceconte

    2017-06-01

    Full Text Available Unlimited replicative potential is one of the hallmarks of cancer cells. In melanoma, hTERT (telomerase reverse transcriptase is frequently overexpressed because of activating mutations in its promoter, suggesting that telomerase is necessary for melanoma development. We observed, however, that a subset of melanoma metastases and derived cell lines had no telomere maintenance mechanism. Early passages of the latter displayed long telomeres that progressively shortened and fused before cell death. We propose that, during melanoma formation, oncogenic mutations occur in precursor melanocytes with long telomeres, providing cells with sufficient replicative potential, thereby bypassing the need to re-activate telomerase. Our data further support the emerging idea that long telomeres promote melanoma formation. These observations are important when considering anticancer therapies targeting telomerase.

  2. The N-terminal domains of TRF1 and TRF2 regulate their ability to condense telomeric DNA.

    Science.gov (United States)

    Poulet, Anaïs; Pisano, Sabrina; Faivre-Moskalenko, Cendrine; Pei, Bei; Tauran, Yannick; Haftek-Terreau, Zofia; Brunet, Frédéric; Le Bihan, Yann-Vaï; Ledu, Marie-Hélène; Montel, Fabien; Hugo, Nicolas; Amiard, Simon; Argoul, Françoise; Chaboud, Annie; Gilson, Eric; Giraud-Panis, Marie-Josèphe

    2012-03-01

    TRF1 and TRF2 are key proteins in human telomeres, which, despite their similarities, have different behaviors upon DNA binding. Previous work has shown that unlike TRF1, TRF2 condenses telomeric, thus creating consequential negative torsion on the adjacent DNA, a property that is thought to lead to the stimulation of single-strand invasion and was proposed to favor telomeric DNA looping. In this report, we show that these activities, originating from the central TRFH domain of TRF2, are also displayed by the TRFH domain of TRF1 but are repressed in the full-length protein by the presence of an acidic domain at the N-terminus. Strikingly, a similar repression is observed on TRF2 through the binding of a TERRA-like RNA molecule to the N-terminus of TRF2. Phylogenetic and biochemical studies suggest that the N-terminal domains of TRF proteins originate from a gradual extension of the coding sequences of a duplicated ancestral gene with a consequential progressive alteration of the biochemical properties of these proteins. Overall, these data suggest that the N-termini of TRF1 and TRF2 have evolved to finely regulate their ability to condense DNA.

  3. Two pathways recruit telomerase to Saccharomyces cerevisiae telomeres.

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    Angela Chan

    2008-10-01

    Full Text Available The catalytic subunit of yeast telomerase, Est2p, is a telomere associated throughout most of the cell cycle, while the Est1p subunit binds only in late S/G2 phase, the time of telomerase action. Est2p binding in G1/early S phase requires a specific interaction between telomerase RNA (TLC1 and Ku80p. Here, we show that in four telomerase-deficient strains (cdc13-2, est1A, tlc1-SD, and tlc1-BD, Est2p telomere binding was normal in G1/early S phase but reduced to about 40-50% of wild type levels in late S/G2 phase. Est1p telomere association was low in all four strains. Wild type levels of Est2p telomere binding in late S/G2 phase was Est1p-dependent and required that Est1p be both telomere-bound and associated with a stem-bulge region in TLC1 RNA. In three telomerase-deficient strains in which Est1p is not Est2p-associated (tlc1-SD, tlc1-BD, and est2A, Est1p was present at normal levels but its telomere binding was very low. When the G1/early S phase and the late S/G2 phase telomerase recruitment pathways were both disrupted, neither Est2p nor Est1p was telomere-associated. We conclude that reduced levels of Est2p and low Est1p telomere binding in late S/G2 phase correlated with an est phenotype, while a WT level of Est2p binding in G1 was not sufficient to maintain telomeres. In addition, even though Cdc13p and Est1p interact by two hybrid, biochemical and genetic criteria, this interaction did not occur unless Est1p was Est2p-associated, suggesting that Est1p comes to the telomere only as part of the holoenzyme. Finally, the G1 and late S/G2 phase pathways for telomerase recruitment are distinct and are likely the only ones that bring telomerase to telomeres in wild-type cells.

  4. Childhood adversity, social support, and telomere length among perinatal women.

    Science.gov (United States)

    Mitchell, Amanda M; Kowalsky, Jennifer M; Epel, Elissa S; Lin, Jue; Christian, Lisa M

    2018-01-01

    Adverse perinatal health outcomes are heightened among women with psychosocial risk factors, including childhood adversity and a lack of social support. Biological aging could be one pathway by which such outcomes occur. However, data examining links between psychosocial factors and indicators of biological aging among perinatal women are limited. The current study examined the associations of childhood socioeconomic status (SES), childhood trauma, and current social support with telomere length in peripheral blood mononuclear cells (PBMCs) in a sample of 81 women assessed in early, mid, and late pregnancy as well as 7-11 weeks postpartum. Childhood SES was defined as perceived childhood social class and parental educational attainment. Measures included the Childhood Trauma Questionnaire, Center for Epidemiologic Studies-Depression Scale, Multidimensional Scale of Perceived Social Support, and average telomere length in PBMCs. Per a linear mixed model, telomere length did not change across pregnancy and postpartum visits; thus, subsequent analyses defined telomere length as the average across all available timepoints. ANCOVAs showed group differences by perceived childhood social class, maternal and paternal educational attainment, and current family social support, with lower values corresponding with shorter telomeres, after adjustment for possible confounds. No effects of childhood trauma or social support from significant others or friends on telomere length were observed. Findings demonstrate that while current SES was not related to telomeres, low childhood SES, independent of current SES, and low family social support were distinct risk factors for cellular aging in women. These data have relevance for understanding potential mechanisms by which early life deprivation of socioeconomic and relationship resources affect maternal health. In turn, this has potential significance for intergenerational transmission of telomere length. The predictive value of

  5. The heritability of leucocyte telomere length dynamics

    DEFF Research Database (Denmark)

    Hjelmborg, Jacob B; Dalgård, Christine; Möller, Sören

    2015-01-01

    BACKGROUND: Leucocyte telomere length (LTL) is a complex trait associated with ageing and longevity. LTL dynamics are defined by LTL and its age-dependent attrition. Strong, but indirect evidence suggests that LTL at birth and its attrition during childhood largely explains interindividual LTL...... variation among adults. A number of studies have estimated the heritability of LTL, but none has assessed the heritability of age-dependent LTL attrition. METHODS: We examined the heritability of LTL dynamics based on a longitudinal evaluation (an average follow-up of 12 years) in 355 monozygotic and 297...... dizygotic same-sex twins (aged 19-64 years at baseline). RESULTS: Heritability of LTL at baseline was estimated at 64% (95% CI 39% to 83%) with 22% (95% CI 6% to 49%) of shared environmental effects. Heritability of age-dependent LTL attrition rate was estimated at 28% (95% CI 16% to 44%). Individually...

  6. The telomere lengthening conundrum - artifact or biology?

    DEFF Research Database (Denmark)

    Steenstrup, Troels; Hjelmborg, Jacob V B; Kark, Jeremy D

    2013-01-01

    Recent longitudinal studies of age-dependent leukocyte telomere length (LTL) attrition have reported that variable proportions of individuals experience LTL lengthening. Often, LTL lengthening has been taken at face value, and authors have speculated about the biological causation of this finding......-dependent LTL attrition in longitudinal studies. We find that LTL lengthening is far less frequent in studies with long follow-up periods and those that used a high-precision Southern blot method (as compared with quantitative polymerase chain reaction determination, which is associated with larger laboratory...... error). We conclude that the LTL lengthening observed in longitudinal studies is predominantly, if not entirely, an artifact of measurement error, which is exacerbated by short follow-up periods. We offer specific suggestions for design of longitudinal studies of LTL attrition to diminish this artifact....

  7. Estimation of the amount of telomere molecules in different human age groups and the telomere increasing effect of acupuncture and shiatsu on St.36, using synthesized basic units of the human telomere molecules as reference control substances for the bi-digital O-ring test resonance phenomenon.

    Science.gov (United States)

    Omura, Y; Shimotsura, Y; Ooki, M; Noguchi, T

    1998-01-01

    It is well established that the telomeres at the ends of chromosomes are composed of long arrays of (TTAGGG)n x (CCCTAA)n that form a nucleoprotein complex required for the replication and protection of chromosome ends. Throughout the cell cycle, telomeres also contain a protein component related to the proto-oncogene Myb that is known as TRF1 (telomere TTAGGG repeat binding factor 1) that binds to the duplex array of TTAGGG repeats in the telomere. Previous studies have shown that TRF1 appears to play a role in controlling the length of telomeres by acting as an inhibitor of telomerase. The amount of each of the TRF1(C-19) & TRF1(N-19) was identical to the amount of telomere of the same organ of the same apparently normal individual. Using synthesized basic unit of TTAGGG, as well as CCCTAA, as separate reference control substances for the Bi-Digital O-Ring Test of Resonance Phenomenon between 2 identical substances, we were able to non-invasively measure the approximate amount of TTAGGG and CCCTAA units, in both normal and cancerous human cells. We examined about 30 apparently normal subjects (both Asian and Caucasian in both sex). The subjects' ages ranged from infancy to 76 years. Each subject was first examined using TTAGGG as a control substance and then examined using CCCTAA as a control substance. The amount of telomere in various cancer tissues are almost always higher than that of normal tissue of the same organ. The measured amounts of both TTAGGG and CCCTAA were found to be in an average of 1500-1600 ng for human fetus or infancy and decreased with the advance of age in both sex with the exception of the heart, brain, eyes (retina), testes, and ovaries, which usually remain at the level of the infant, or reduced very little. Individuals in the same age group had a similar range of amounts of both TTAGGG and CCCTAA in the same organ of the same individual, (except for those with unusually low telomeres often had chronic degenerative diseases, and those

  8. Does oxidative stress shorten telomeres in vivo? A review.

    Science.gov (United States)

    Reichert, Sophie; Stier, Antoine

    2017-12-01

    The length of telomeres, the protective caps of chromosomes, is increasingly used as a biomarker of individual health state because it has been shown to predict chances of survival in a range of endothermic species including humans. Oxidative stress is presumed to be a major cause of telomere shortening, but most evidence to date comes from in vitro cultured cells. The importance of oxidative stress as a determinant of telomere shortening in vivo remains less clear and has recently been questioned. We, therefore, reviewed correlative and experimental studies investigating the links between oxidative stress and telomere shortening in vivo While correlative studies provide equivocal support for a connection between oxidative stress and telomere attrition (10 of 18 studies), most experimental studies published so far (seven of eight studies) partially or fully support this hypothesis. Yet, this link seems to be tissue-dependent in some cases, or restricted to particular categories of individual (e.g. sex-dependent) in other cases. More experimental studies, especially those decreasing antioxidant protection or increasing pro-oxidant generation, are required to further our understanding of the importance of oxidative stress in determining telomere length in vivo Studies comparing growing versus adult individuals, or proliferative versus non-proliferative tissues would provide particularly important insights. © 2017 The Author(s).

  9. Television Watching and Telomere Length Among Adults in Southwest China.

    Science.gov (United States)

    Xue, Hong-Mei; Liu, Qian-Qian; Tian, Guo; Quan, Li-Ming; Zhao, Yong; Cheng, Guo

    2017-09-01

    To explore the independent associations of sedentary behavior and physical activity with telomere length among Chinese adults. Data on total time of sedentary behavior, screen-based sedentary behavior (including television watching and computer or phone use), moderate to vigorous physical activity, and dietary intake of 518 adults in Chengdu, Guizhou, and Xiamen in China (54.25% women) aged 20 to 70 years were obtained between 2013 and 2015 through questionnaires. Height, weight, and waist circumference were measured to calculate body mass index and percentage of body fat. Telomere length was measured through Southern blot technique. Television watching was inversely related to adjusted telomere length (-71.75 base pair; SE = 34.40; P  = .04). Furthermore, a similar trend between telomere length and television watching was found in the group aged 20 to 40 years after adjusting for all covariates. Adults aged 20 to 40 years in the highest tertile of daily time spent on watching television had 4.0% shorter telomere length than adults in the lowest tertile (P = .03). Although the association is modest, television watching is inversely related to telomere length among Chinese adults, warranting further investigation in large prospective studies.

  10. Structure and function of the telomeric CST complex

    Directory of Open Access Journals (Sweden)

    Cory Rice

    2016-01-01

    Full Text Available Telomeres comprise the ends of eukaryotic chromosomes and are essential for cell proliferation and genome maintenance. Telomeres are replicated by telomerase, a ribonucleoprotein (RNP reverse transcriptase, and are maintained primarily by nucleoprotein complexes such as shelterin (TRF1, TRF2, TIN2, RAP1, POT1, TPP1 and CST (Cdc13/Ctc1, Stn1, Ten1. The focus of this review is on the CST complex and its role in telomere maintenance. Although initially thought to be unique to yeast, it is now evident that the CST complex is present in a diverse range of organisms where it contributes to genome maintenance. The CST accomplishes these tasks via telomere capping and by regulating telomerase and DNA polymerase alpha-primase (polα-primase access to telomeres, a process closely coordinated with the shelterin complex in most organisms. The goal of this review is to provide a brief but comprehensive account of the diverse, and in some cases organism-dependent, functions of the CST complex and how it contributes to telomere maintenance and cell proliferation.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-06-15

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

  12. The Presence of Telomere Fusion in Sporadic Colon Cancer Independently of Disease Stage, TP53/KRAS Mutation Status, Mean Telomere Length, and Telomerase Activity

    Directory of Open Access Journals (Sweden)

    Hiromi Tanaka

    2014-10-01

    Full Text Available Defects in telomere maintenance can result in telomere fusions that likely play a causative role in carcinogenesis by promoting genomic instability. However, this proposition remains to be fully understood in human colon carcinogenesis. In the present study, the temporal sequence of telomere dysfunction dynamics was delineated by analyzing telomere fusion, telomere length, telomerase activity, hotspot mutations in KRAS or BRAF, and TP53 of tissue samples obtained from 18 colon cancer patients. Our results revealed that both the deficiency of p53 and the shortening of mean telomere length were not necessary for producing telomere fusions in colon tissue. In five cases, telomere fusion was observed even in tissue adjacent to cancerous lesions, suggesting that genomic instability is initiated in pathologically non-cancerous lesions. The extent of mean telomere attrition increased with lymph node invasiveness of tumors, implying that mean telomere shortening correlates with colon cancer progression. Telomerase activity was relatively higher in most cancer tissues containing mutation(s in KRAS or BRAF and/or TP53 compared to those without these hotspot mutations, suggesting that telomerase could become fully active at the late stage of colon cancer development. Interestingly, the majority of telomere fusion junctions in colon cancer appeared to be a chromatid-type containing chromosome 7q or 12q. In sum, this meticulous correlative study not only highlights the concept that telomere fusion is present in the early stages of cancer regardless of TP53/KRAS mutation status, mean telomere length, and telomerase activity, but also provides additional insights targeting key telomere fusion junctions which may have significant implications for colon cancer diagnoses.

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

    Science.gov (United States)

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

    2013-02-01

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

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

    Directory of Open Access Journals (Sweden)

    Denise Aydinonat

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

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

    Science.gov (United States)

    Aydinonat, Denise; Penn, Dustin J; Smith, Steve; Moodley, Yoshan; Hoelzl, Franz; Knauer, Felix; Schwarzenberger, Franz

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Amina Boussouar

    2013-01-01

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

  17. Ageing and reproduction: antioxidant supplementation alleviates telomere loss in wild birds

    National Research Council Canada - National Science Library

    Badás, E. P; Martínez, J; Rivero de Aguilar Cachafeiro, J; Miranda, F; Figuerola, J; Merino, S

    2015-01-01

    .... However, the effects of nutritional status and infection on ageing remain unknown. Telomeres function as protective caps at the ends of eukaryotic chromosomes, and changes in telomere length is a commonly used proxy for ageing...

  18. Migration and stress during reproduction govern telomere dynamics in a seabird

    Science.gov (United States)

    Schultner, Jannik; Moe, Børge; Chastel, Olivier; Bech, Claus; Kitaysky, Alexander S.

    2014-01-01

    Changes in telomere length are believed to reflect changes in physiological state and life expectancy in animals. However, much remains unknown about the determinants of telomere dynamics in wild populations, and specifically the influence of conditions during highly mobile life-history stages, for example migration. We tested whether telomere dynamics were associated with migratory behaviour and/or with stress during reproduction in free-living seabirds. We induced short-term stress during reproduction in chick-rearing, black-legged kittiwakes (Rissa tridactyla), tracked winter migration with geolocators and measured telomere length before and after winter migration. We found that time spent at wintering grounds correlated with reduced telomere loss, while stress during reproduction accelerated telomere shortening. Our results suggest that different life-history stages interact to influence telomere length, and that migratory patterns may be important determinants of variation in an individual's telomere dynamics. PMID:24429681

  19. Human telomere biology: A contributory and interactive factor in aging, disease risks, and protection.

    Science.gov (United States)

    Blackburn, Elizabeth H; Epel, Elissa S; Lin, Jue

    2015-12-04

    Telomeres are the protective end-complexes at the termini of eukaryotic chromosomes. Telomere attrition can lead to potentially maladaptive cellular changes, block cell division, and interfere with tissue replenishment. Recent advances in the understanding of human disease processes have clarified the roles of telomere biology, especially in diseases of human aging and in some aging-related processes. Greater overall telomere attrition predicts mortality and aging-related diseases in inherited telomere syndrome patients, and also in general human cohorts. However, genetically caused variations in telomere maintenance either raise or lower risks and progression of cancers, in a highly cancer type-specific fashion. Telomere maintenance is determined by genetic factors and is also cumulatively shaped by nongenetic influences throughout human life; both can interact. These and other recent findings highlight both causal and potentiating roles for telomere attrition in human diseases. Copyright © 2015, American Association for the Advancement of Science.

  20. TERRA Promotes Telomere Shortening through Exonuclease 1–Mediated Resection of Chromosome Ends

    Science.gov (United States)

    Pfeiffer, Verena; Lingner, Joachim

    2012-01-01

    The long noncoding telomeric repeat containing RNA (TERRA) is expressed at chromosome ends. TERRA upregulation upon experimental manipulation or in ICF (immunodeficiency, centromeric instability, facial anomalies) patients correlates with short telomeres. To study the mechanism of telomere length control by TERRA in Saccharomyces cerevisiae, we mapped the transcriptional start site of TERRA at telomere 1L and inserted a doxycycline regulatable promoter upstream. Induction of TERRA transcription led to telomere shortening of 1L but not of other chromosome ends. TERRA interacts with the Exo1-inhibiting Ku70/80 complex, and deletion of EXO1 but not MRE11 fully suppressed the TERRA–mediated short telomere phenotype in presence and absence of telomerase. Thus TERRA transcription facilitates the 5′-3′ nuclease activity of Exo1 at chromosome ends, providing a means to regulate the telomere shortening rate. Thereby, telomere transcription can regulate cellular lifespan through modulation of chromosome end processing activities. PMID:22719262

  1. TERRA promotes telomere shortening through exonuclease 1-mediated resection of chromosome ends.

    Science.gov (United States)

    Pfeiffer, Verena; Lingner, Joachim

    2012-01-01

    The long noncoding telomeric repeat containing RNA (TERRA) is expressed at chromosome ends. TERRA upregulation upon experimental manipulation or in ICF (immunodeficiency, centromeric instability, facial anomalies) patients correlates with short telomeres. To study the mechanism of telomere length control by TERRA in Saccharomyces cerevisiae, we mapped the transcriptional start site of TERRA at telomere 1L and inserted a doxycycline regulatable promoter upstream. Induction of TERRA transcription led to telomere shortening of 1L but not of other chromosome ends. TERRA interacts with the Exo1-inhibiting Ku70/80 complex, and deletion of EXO1 but not MRE11 fully suppressed the TERRA-mediated short telomere phenotype in presence and absence of telomerase. Thus TERRA transcription facilitates the 5'-3' nuclease activity of Exo1 at chromosome ends, providing a means to regulate the telomere shortening rate. Thereby, telomere transcription can regulate cellular lifespan through modulation of chromosome end processing activities.

  2. Examining the Role of Msh2 and Mre11 in Telomere Rescue

    National Research Council Canada - National Science Library

    Meyer, Damon

    2007-01-01

    .... Continuously dividing human somatic cells and S. cerevisiae cells lacking functional telomerase, a ribonucleoprotein complex required for telomere replication, experience progressive telomere degradation that culminates in replicative senescence 5,6...

  3. Telomere length reflects phenotypic quality and costs of reproduction in a long-lived seabird

    OpenAIRE

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

    2013-01-01

    Telomere length is associated with cellular senescence, lifestyle and ageing. Short telomeres indicate poor health in humans and reduced life expectancy in several bird species, but little is known about telomeres in relation to phenotypic quality in wild animals. We investigated telomere lengths in erythrocytes of known-age common terns (Sterna hirundo), a migratory seabird, in relation to arrival date and reproductive performance. Cross-sectional data revealed that, independent of age, indi...

  4. Telomeres are elongated in older individuals in a hibernating rodent, the edible dormouse (Glis glis)

    OpenAIRE

    Franz Hoelzl; Steve Smith; Cornils, Jessica S.; Denise Aydinonat; Claudia Bieber; Thomas Ruf

    2016-01-01

    Telomere shortening is thought to be an important biomarker for life history traits such as lifespan and aging, and can be indicative of genome integrity, survival probability and the risk of cancer development. In humans and other animals, telomeres almost always shorten with age, with more rapid telomere attrition in short-lived species. Here, we show that in the edible dormouse (Glis glis) telomere length significantly increases from an age of 6 to an age of 9 years. While this finding cou...

  5. Maternal pre-pregnancy body mass index and newborn telomere length

    OpenAIRE

    Martens, Dries S.; Plusquin, Michelle; Gyselaers, Wilfried; De Vivo, Immaculata; Nawrot, Tim

    2016-01-01

    Background: Newborn telomere length sets telomere length for later life. At birth, telomere length is highly variable among newborns and the environmental factors during in utero life for this observation remain largely unidentified. Obesity during pregnancy might reflect an adverse nutritional status affecting pregnancy and offspring outcomes, but the association of maternal pre-pregnancy body mass index (BMI) with newborn telomere length, as a mechanism of maternal obesity, on the next gene...

  6. Telomerecat: A ploidy-agnostic method for estimating telomere length from whole genome sequencing data

    NARCIS (Netherlands)

    Farmery, James H. R.; Smith, Mike L.; Lynch, Andy G.; Huissoon, Aarnoud; Furnell, Abigail; Mead, Adam; Levine, Adam P.; Manzur, Adnan; Thrasher, Adrian; Greenhalgh, Alan; Parker, Alasdair; Sanchis-Juan, Alba; Richter, Alex; Gardham, Alice; Lawrie, Allan; Sohal, Aman; Creaser-Myers, Amanda; Frary, Amy; Greinacher, Andreas; Themistocleous, Andreas; Peacock, Andrew J.; Marshall, Andrew; Mumford, Andrew; Rice, Andrew; Webster, Andrew; Brady, Angie; Koziell, Ania; Manson, Ania; Chandra, Anita; Hensiek, Anke; Veld, Anna Huis In't; Maw, Anna; Kelly, Anne M.; Moore, Anthony; Vonk Noordegraaf, Anton; Attwood, Antony; Herwadkar, Archana; Ghofrani, Ardi; Houweling, Arjan C.; Girerd, Barbara; Furie, Bruce; Treacy, Carmen M.; Millar, Carolyn M.; Sewell, Carrock; Roughley, Catherine; Titterton, Catherine; Williamson, Catherine; Hadinnapola, Charaka; Deshpande, Charu; Toh, Cheng-Hock; Bacchelli, Chiara; Patch, Chris; Geet, Chris Van; Babbs, Christian; Bryson, Christine; Penkett, Christopher J.; Rhodes, Christopher J.; Watt, Christopher; Bethune, Claire; Booth, Claire; Lentaigne, Claire; McJannet, Coleen; Church, Colin; French, Courtney; Samarghitean, Crina; Halmagyi, Csaba; Gale, Daniel; Greene, Daniel; Hart, Daniel; Allsup, David; Bennett, David; Edgar, David; Kiely, David G.; Gosal, David; Perry, David J.; Keeling, David; Montani, David; Shipley, Debbie; Whitehorn, Deborah; Fletcher, Debra; Krishnakumar, Deepa; Grozeva, Detelina; Kumararatne, Dinakantha; Thompson, Dorothy; Josifova, Dragana; Maher, Eamonn; Wong, Edwin K. S.; Murphy, Elaine; Dewhurst, Eleanor; Louka, Eleni; Rosser, Elisabeth; Chalmers, Elizabeth; Colby, Elizabeth; Drewe, Elizabeth; McDermott, Elizabeth; Thomas, Ellen; Staples, Emily; Clement, Emma; Matthews, Emma; Wakeling, Emma; Oksenhendler, Eric; Turro, Ernest; Reid, Evan; Wassmer, Evangeline; Raymond, F. Lucy; Hu, Fengyuan; Kennedy, Fiona; Soubrier, Florent; Flinter, Frances; Kovacs, Gabor; Polwarth, Gary; Ambegaonkar, Gautum; Arno, Gavin; Hudson, Gavin; Woods, Geoff; Coghlan, Gerry; Hayman, Grant; Arumugakani, Gururaj; Schotte, Gwen; Cook, H. Terry; Alachkar, Hana; Lango Allen, Hana; Lango-Allen, Hana; Stark, Hannah; Stauss, Hans; Schulze, Harald; Boggard, Harm J.; Baxendale, Helen; Dolling, Helen; Firth, Helen; Gall, Henning; Watson, Henry; Longhurst, Hilary; Markus, Hugh S.; Watkins, Hugh; Simeoni, Ilenia; Emmerson, Ingrid; Roberts, Irene; Quinti, Isabella; Wanjiku, Ivy; Gibbs, J. Simon R.; Thaventhiran, James; Whitworth, James; Hurst, Jane; Collins, Janine; Suntharalingam, Jay; Payne, Jeanette; Thachil, Jecko; Martin, Jennifer M.; Martin, Jennifer; Carmichael, Jenny; Maimaris, Jesmeen; Paterson, Joan; Pepke-Zaba, Joanna; Heemskerk, Johan W. M.; Gebhart, Johanna; Davis, John; Pasi, John; Bradley, John R.; Wharton, John; Stephens, Jonathan; Rankin, Julia; Anderson, Julie; Vogt, Julie; von Ziegenweldt, Julie; Rehnstrom, Karola; Megy, Karyn; Talks, Kate; Peerlinck, Kathelijne; Yates, Katherine; Freson, Kathleen; Stirrups, Kathleen; Gomez, Keith; Smith, Kenneth G. C.; Carss, Keren; Rue-Albrecht, Kevin; Gilmour, Kimberley; Masati, Larahmie; Scelsi, Laura; Southgate, Laura; Ranganathan, Lavanya; Ginsberg, Lionel; Devlin, Lisa; Willcocks, Lisa; Ormondroyd, Liz; Lorenzo, Lorena; Harper, Lorraine; Allen, Louise; Daugherty, Louise; Chitre, Manali; Kurian, Manju; Humbert, Marc; Tischkowitz, Marc; Bitner-Glindzicz, Maria; Erwood, Marie; Scully, Marie; Veltman, Marijke; Caulfield, Mark; Layton, Mark; McCarthy, Mark; Ponsford, Mark; Toshner, Mark; Bleda, Marta; Wilkins, Martin; Mathias, Mary; Reilly, Mary; Afzal, Maryam; Brown, Matthew; Rondina, Matthew; Stubbs, Matthew; Haimel, Matthias; Lees, Melissa; Laffan, Michael A.; Browning, Michael; Gattens, Michael; Richards, Michael; Michaelides, Michel; Lambert, Michele P.; Makris, Mike; de Vries, Minka; Mahdi-Rogers, Mohamed; Saleem, Moin; Thomas, Moira; Holder, Muriel; Eyries, Mélanie; Clements-Brod, Naomi; Canham, Natalie; Dormand, Natalie; Zuydam, Natalie Van; Kingston, Nathalie; Ghali, Neeti; Cooper, Nichola; Morrell, Nicholas W.; Yeatman, Nigel; Roy, Noémi; Shamardina, Olga; Alavijeh, Omid S.; Gresele, Paolo; Nurden, Paquita; Chinnery, Patrick; Deegan, Patrick; Yong, Patrick; Man, Patrick Yu Wai; Corris, Paul A.; Calleja, Paul; Gissen, Paul; Bolton-Maggs, Paula; Rayner-Matthews, Paula; Ghataorhe, Pavandeep K.; Gordins, Pavel; Stein, Penelope; Collins, Peter; Dixon, Peter; Kelleher, Peter; Ancliff, Phil; Yu, Ping; Tait, R. Campbell; Linger, Rachel; Doffinger, Rainer; Machado, Rajiv; Kazmi, Rashid; Sargur, Ravishankar; Favier, Remi; Tan, Rhea; Liesner, Ri; Antrobus, Richard; Sandford, Richard; Scott, Richard; Trembath, Richard; Horvath, Rita; Hadden, Rob; MackenzieRoss, Rob V.; Henderson, Robert; MacLaren, Robert; James, Roger; Ghurye, Rohit; DaCosta, Rosa; Hague, Rosie; Mapeta, Rutendo; Armstrong, Ruth; Noorani, Sadia; Murng, Sai; Santra, Saikat; Tuna, Salih; Johnson, Sally; Chong, Sam; Lear, Sara; Walker, Sara; Goddard, Sarah; Mangles, Sarah; Westbury, Sarah; Mehta, Sarju; Hackett, Scott; Nejentsev, Sergey; Moledina, Shahin; Bibi, Shahnaz; Meehan, Sharon; Othman, Shokri; Revel-Vilk, Shoshana; Holden, Simon; McGowan, Simon; Staines, Simon; Savic, Sinisa; Burns, Siobhan; Grigoriadou, Sofia; Papadia, Sofia; Ashford, Sofie; Schulman, Sol; Ali, Sonia; Park, Soo-Mi; Davies, Sophie; Stock, Sophie; Ali, Souad; Deevi, Sri V. V.; Gräf, Stefan; Ghio, Stefano; Wort, Stephen J.; Jolles, Stephen; Austin, Steve; Welch, Steve; Meacham, Stuart; Rankin, Stuart; Walker, Suellen; Seneviratne, Suranjith; Holder, Susan; Sivapalaratnam, Suthesh; Richardson, Sylvia; Kuijpers, Taco; Bariana, Tadbir K.; Bakchoul, Tamam; Everington, Tamara; Renton, Tara; Young, Tim; Aitman, Timothy; Warner, Timothy Q.; Vale, Tom; Hammerton, Tracey; Pollock, Val; Matser, Vera; Cookson, Victoria; Clowes, Virginia; Qasim, Waseem; Wei, Wei; Erber, Wendy N.; Ouwehand, Willem H.; Astle, William; Egner, William; Turek, Wojciech; Henskens, Yvonne; Tan, Yvonne

    2018-01-01

    Telomere length is a risk factor in disease and the dynamics of telomere length are crucial to our understanding of cell replication and vitality. The proliferation of whole genome sequencing represents an unprecedented opportunity to glean new insights into telomere biology on a previously

  7. Chromatin features of plant telomeric sequences at terminal versus internal positions

    Directory of Open Access Journals (Sweden)

    Eva eMajerová

    2014-11-01

    Full Text Available Epigenetic mechanisms are involved in regulation of crucial cellular processes in eukaryotic organisms. Data on the epigenetic features of plant telomeres and their epigenetic regulation were published mostly for Arabidopsis thaliana, in which the presence of interstitial telomeric repeats (ITRs may interfere with genuine telomeres in most analyses. Here, we studied the epigenetic landscape and transcription of telomeres and ITRs in Nicotiana tabacum with long telomeres and no detectable ITRs, and in Ballantinia antipoda with large blocks of pericentromeric ITRs and relatively short telomeres. Chromatin of genuine telomeres displayed heterochromatic as well as euchromatic marks, while ITRs were just heterochromatic. Methylated cytosines were present at telomeres and ITRs, but showed a bias with more methylation towards distal telomere positions and different blocks of B. antipoda ITRs methylated to different levels. Telomeric transcripts TERRA (G-rich and ARRET (C-rich were identified in both plants and their levels varied among tissues with a maximum in blossoms. Plants with substantially different proportions of internally and terminally located telomeric repeats are instrumental in clarifying the chromatin status of telomeric repeats at distinct chromosome locations.

  8. Dynamic Length Changes of Telomeres and Their Nuclear Organization in Chronic Myeloid Leukemia

    Energy Technology Data Exchange (ETDEWEB)

    Samassekou, Oumar [Manitoba Institute of Cell Biology, Cancer Care Manitoba, Department of Physiology, University of Manitoba, Winnipeg, Manitoba R3E 0V9 (Canada)

    2013-08-22

    Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the t(9;22) translocation. As in most cancers, short telomeres are one of the features of CML cells, and telomere shortening accentuates as the disease progresses from the chronic phase to the blastic phase. Although most individual telomeres are short, some of them are lengthened, and long individual telomeres occur non-randomly and might be associated with clonal selection. Telomerase is the main mechanism used to maintain telomere lengths, and its activity increases when CML evolves toward advanced stages. ALT might be another mechanism employed by CML cells to sustain the homeostasis of their telomere lengths and this mechanism seems predominant at the early stage of leukemogenesis. Also, telomerase and ALT might jointly act to maintain telomere lengths at the chronic phase, and as CML progresses, telomerase becomes the major mechanism. Finally, CML cells display an altered nuclear organization of their telomeres which is characterized by the presence of high number of telomeric aggregates, a feature of genomic instability, and differential positioning of telomeres. CML represents a good model to study mechanisms responsible for dynamic changes of individual telomere lengths and the remodeling of telomeric nuclear organization throughout cancer progression.

  9. A different approach to telomere analysis with ddPRINS in chronic lymphocytic leukemia

    DEFF Research Database (Denmark)

    Palanduz, Sukru; Serakinci, Nedime; Cefle, Kivanc

    2006-01-01

    in patients with B-cell CLL in a comparison with the control group by using ddPRINS technique. Twenty patients with CLL and four healthy donors as a control group were included. We found short telomeres and no detectable telomeric repeats at the sites of chromosome fusion. We hypothesise that the telomeric...

  10. Dietary restraint and telomere length in pre- and postmenopausal women.

    Science.gov (United States)

    Kiefer, Amy; Lin, Jue; Blackburn, Elizabeth; Epel, Elissa

    2008-10-01

    Leukocyte telomere shortening can serve as a biomarker of aging, as telomere length (TL) can decline with age and shortening is positively associated with morbidity and mortality. It is therefore important to identify psychological and behavioral factors linked to accelerated telomere shortening. Stress and poorer metabolic health (greater adiposity, insulin resistance, and cortisol) correlate with shorter telomeres. Self-reported dietary restraint (DR), defined as chronic preoccupation with weight and attempts at restricting food intake, is linked to greater perceived stress, cortisol, and weight gain, when assessed in community studies (versus in weight loss programs). To test for an association between DR and TL in healthy women across a range of ages. We examined whether DR is linked to TL in two samples, one of premenopausal women (aged 20-50 years;N = 36) and one of postmenopausal women (aged 53-69 years; N = 20). In both samples, higher levels of DR were associated with shorter leukocyte TL, independent of body mass index, smoking, and age. Chronic DR, as assessed by self-report (i.e. not caloric restriction), may be a risk factor for premature telomere shortening. Potential mechanisms are discussed.

  11. Therapeutic opportunities: Telomere maintenance in inducible pluripotent stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Gourronc, Francoise A. [Department of Microbiology, University of Iowa (United States); Klingelhutz, Aloysius J., E-mail: al-klingelhutz@uiowa.edu [Department of Microbiology, University of Iowa (United States)

    2012-02-01

    It has been demonstrated that exogenous expression of a combination of transcription factors can reprogram differentiated cells such as fibroblasts and keratinocytes into what have been termed induced pluripotent stem (iPS) cells. These iPS cells are capable of differentiating into all the tissue lineages when placed in the right environment and, in the case of mouse cells, can generate chimeric mice and be transmitted through the germline. Safer and more efficient methods of reprogramming are rapidly being developed. Clearly, iPS cells present a number of exciting possibilities, including disease modeling and therapy. A major question is whether the nuclei of iPS cells are truly rejuvenated or whether they might retain some of the marks of aging from the cells from which they were derived. One measure of cellular aging is the telomere. In this regard, recent studies have demonstrated that telomeres in iPS cells may be rejuvenated. They are not only elongated by reactivated telomerase but they are also epigenetically modified to be similar but not identical to embryonic stem cells. Upon differentiation, the derivative cells turn down telomerase, the telomeres begin to shorten again, and the telomeres and the genome are returned to an epigenetic state that is similar to normal differentiated somatic cells. While these preliminary telomere findings are promising, the overall genomic integrity of reprogrammed cells may still be problematic and further studies are needed to examine the safety and feasibility of using iPS cells in regenerative medicine applications.

  12. Test anxiety and telomere length: Academic stress in adolescents may not cause rapid telomere erosion.

    Science.gov (United States)

    Zou, Yaru; Leong, Waiian; Yao, Mingling; Hu, Xuefei; Lu, Sixiao; Zhu, Xiaowei; Chen, Lianxiang; Tong, Jianjing; Shi, Jingyi; Gilson, Eric; Ye, Jing; Lu, Yiming

    2017-02-14

    Academic stress (AS) is one of the most important health problems experienced by students, but no biomarker of the potential psychological or physical problems associated with AS has yet been identified. As several cross-sectional studies have shown that psychiatric conditions accelerate aging and shorten telomere length (TL), we explored whether AS affected TL.Between June 2014 and July 2014, we recruited 200 junior high school students with imminent final examinations for participation in this study. The students were divided into three subgroups (mild, moderate, and severe anxiety) using the Sarason Test Anxiety Scale (TAS). Saliva samples were collected for TL measurement via quantitative polymerase chain reaction (qPCR).Students from both a specialized and a general school suffered from anxiety (p > 0.05). A total 35% had severe anxiety (score: 26.09±3.87), 33% had moderate anxiety (16.98±2.64), and 32% had mild anxiety (7.89±1.92). The TAS values differed significantly (p 0.05): 1.14±0.46 for those with severe anxiety, 1.02±0.40 for those with moderate anxiety, and 1.12±0.45 for those with mild anxiety.Previous reports have found that AS is very common in Asian adolescents. We found no immediate telomere shortening in adolescents with AS. Longitudinal observations are required to determine if TL is affected by AS.

  13. Tired telomeres: Poor global sleep quality, perceived stress, and telomere length in immune cell subsets in obese men and women.

    Science.gov (United States)

    Prather, Aric A; Gurfein, Blake; Moran, Patricia; Daubenmier, Jennifer; Acree, Michael; Bacchetti, Peter; Sinclair, Elizabeth; Lin, Jue; Blackburn, Elizabeth; Hecht, Frederick M; Epel, Elissa S

    2015-07-01

    Poor sleep quality and short sleep duration are associated with increased incidence and progression of a number of chronic health conditions observed at greater frequency among the obese and those experiencing high levels of stress. Accelerated cellular aging, as indexed by telomere attrition in immune cells, is a plausible pathway linking sleep and disease risk. Prior studies linking sleep and telomere length are mixed. One factor may be reliance on leukocytes, which are composed of varied immune cell types, as the sole measure of telomere length. To better clarify these associations, we investigated the relationships of global sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), and diary-reported sleep duration with telomere length in different immune cell subsets, including granulocytes, peripheral blood mononuclear cells (PBMCs), CD8+ and CD4+ T lymphocytes, and B lymphocytes in a sample of 87 obese men and women (BMI mean=35.4, SD=3.6; 81.6% women; 62.8% Caucasian). Multiple linear regression analyses were performed adjusting for age, gender, race, education, BMI, sleep apnea risk, and perceived stress. Poorer PSQI global sleep quality was associated with statistically significantly shorter telomere length in lymphocytes but not granulocytes and in particular CD8+ T cells (b=-56.8 base pairs per one point increase in PSQI, SE=20.4, p=0.007) and CD4+ T cells (b=-37.2, SE=15.9, p=0.022). Among separate aspects of global sleep quality, low perceived sleep quality and decrements in daytime function were most related to shorter telomeres. In addition, perceived stress moderated the sleep-CD8+ telomere association. Poorer global sleep quality predicted shorter telomere length in CD8+ T cells among those with high perceived stress but not in low stress participants. These findings provide preliminary evidence that poorer global sleep quality is related to telomere length in several immune cell types, which may serve as a pathway linking sleep and

  14. Meiotic chromosome pairing is promoted by telomere-led chromosome movements independent of bouquet formation.

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    Chih-Ying Lee

    Full Text Available Chromosome pairing in meiotic prophase is a prerequisite for the high fidelity of chromosome segregation that haploidizes the genome prior to gamete formation. In the budding yeast Saccharomyces cerevisiae, as in most multicellular eukaryotes, homologous pairing at the cytological level reflects the contemporaneous search for homology at the molecular level, where DNA double-strand broken ends find and interact with templates for repair on homologous chromosomes. Synapsis (synaptonemal complex formation stabilizes pairing and supports DNA repair. The bouquet stage, where telomeres have formed a transient single cluster early in meiotic prophase, and telomere-promoted rapid meiotic prophase chromosome movements (RPMs are prominent temporal correlates of pairing and synapsis. The bouquet has long been thought to contribute to the kinetics of pairing, but the individual roles of bouquet and RPMs are difficult to assess because of common dependencies. For example, in budding yeast RPMs and bouquet both require the broadly conserved SUN protein Mps3 as well as Ndj1 and Csm4, which link telomeres to the cytoskeleton through the intact nuclear envelope. We find that mutants in these genes provide a graded series of RPM activity: wild-type>mps3-dCC>mps3-dAR>ndj1Δ>mps3-dNT = csm4Δ. Pairing rates are directly correlated with RPM activity even though only wild-type forms a bouquet, suggesting that RPMs promote homologous pairing directly while the bouquet plays at most a minor role in Saccharomyces cerevisiae. A new collision trap assay demonstrates that RPMs generate homologous and heterologous chromosome collisions in or before the earliest stages of prophase, suggesting that RPMs contribute to pairing by stirring the nuclear contents to aid the recombination-mediated homology search.

  15. Telomere length as a potential biomarker of coronary artery disease

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    Joyeeta Bhattacharyya

    2017-01-01

    Full Text Available Coronary artery disease (CAD is a multifactorial disease whose prevalence remains unabated especially in developing countries. Both lifestyle factors and genetic predisposition contribute to this disorder. Though notable achievements have been made in the medical, interventional and surgical management of CAD, the need for its prevention is more important. Among other modalities, this calls for defining evidence-based new biomarkers, which on their own or in combination with other known biomarkers may predict the risk of CAD to enable institution of appropriate preventive strategies. In the present communication, we have discussed the usefulness of shortening of telomeres as a potential biomarker of CAD. Clinical research evidence in favour of telomere shortening in CAD is well documented in different ethnic populations of the world. Establishing a well-standardized and accurate method of evaluating telomere length is essential before its routine use in preventive cardiology.

  16. Telomere Transcripts Target Telomerase in Human Cancer Cells

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    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.

  17. Senescence is involved in the pathogenesis of chronic obstructive pulmonary disease through effects on telomeres and the anti-aging molecule fibroblast growth factor 23.

    Science.gov (United States)

    Ishii, Takeo; Gemma, Akihiko; Kida, Kozui

    2015-07-01

    Fibroblast growth factor 23 knockout mice develop premature aging and emphysema, indicating that dysregulation of the normal aging process is involved in the pathobiology of chronic obstructive pulmonary disease. Thus, we explored the association among a coding single-nucleotide polymorphism of fibroblast growth factor 23, its protein concentration in serum and telomere length in patients with chronic obstructive pulmonary disease. The study involved 361 smokers; among whom, 244 were patients with chronic obstructive pulmonary disease. We genotyped a coding single-nucleotide polymorphism of fibroblast growth factor 23, rs7955866, and measured the telomere length of the peripheral blood cells. We also determined emphysema severity and airflow obstruction using computed tomography and pulmonary function tests, respectively. Furthermore, we analyzed the association between the disease phenotypes and fibroblast growth factor 23 genotypes or telomere length of peripheral blood leukocytes, as well as the association between the serum level of the studied protein and its genotypes. The mice with A alleles on rs7955866 showed severe upper lung emphysema (P = 0.008). The serum concentration of the tested protein was lower in the mice with A allele than in the G homozygotes (P = 0.004). Telomere shortening was associated with airflow obstruction (P = 0.009), but not with upper lung emphysema. A variation of fibroblast growth factor 23 with a reduced serum concentration appeared to promote emphysema formation. Telomere shortening in peripheral blood leukocytes was not associated with emphysema, but with airflow obstruction in chronic obstructive pulmonary disease through an independent mechanism. © 2014 Japan Geriatrics Society.

  18. Estimating telomere length from whole genome sequence data.

    Science.gov (United States)

    Ding, Zhihao; Mangino, Massimo; Aviv, Abraham; Spector, Tim; Durbin, Richard

    2014-05-01

    Telomeres play a key role in replicative ageing and undergo age-dependent attrition in vivo. Here, we report a novel method, TelSeq, to measure average telomere length from whole genome or exome shotgun sequence data. In 260 leukocyte samples, we show that TelSeq results correlate with Southern blot measurements of the mean length of terminal restriction fragments (mTRFs) and display age-dependent attrition comparably well as mTRFs. © The Author(s) 2014. Published by Oxford University Press [on behalf of insert name of society].

  19. Association of Telomere Length with Breast Cancer Prognostic Factors.

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    Kaoutar Ennour-Idrissi

    Full Text Available Telomere length, a marker of cell aging, seems to be affected by the same factors thought to be associated with breast cancer prognosis.To examine associations of peripheral blood cell-measured telomere length with traditional and potential prognostic factors in breast cancer patients.We conducted a cross-sectional analysis of data collected before surgery from 162 breast cancer patients recruited consecutively between 01/2011 and 05/2012, at a breast cancer reference center. Data on the main lifestyle factors (smoking, alcohol consumption, physical activity were collected using standardized questionnaires. Anthropometric factors were measured. Tumor biological characteristics were extracted from pathology reports. Telomere length was measured using a highly reproducible quantitative PCR method in peripheral white blood cells. Spearman partial rank-order correlations and multivariate general linear models were used to evaluate relationships between telomere length and prognostic factors.Telomere length was positively associated with total physical activity (rs = 0.17, P = 0.033; Ptrend = 0.069, occupational physical activity (rs = 0.15, P = 0.054; Ptrend = 0.054 and transportation-related physical activity (rs = 0.19, P = 0.019; P = 0.005. Among post-menopausal women, telomere length remained positively associated with total physical activity (rs = 0.27, P = 0.016; Ptrend = 0.054 and occupational physical activity (rs = 0.26, P = 0.021; Ptrend = 0.056 and was only associated with transportation-related physical activity among pre-menopausal women (rs = 0.27, P = 0.015; P = 0.004. No association was observed between telomere length and recreational or household activities, other lifestyle factors or traditional prognostic factors.Telomeres are longer in more active breast cancer patients. Since white blood cells are involved in anticancer immune responses, these findings suggest that even regular low-intensity physical activity, such as that

  20. Characterization of telomeres and telomerase from the single-celled eukaryote Giardia intestinalis.

    Science.gov (United States)

    Uzlíková, Magdalena; Fulnečková, Jana; Weisz, Filip; Sýkorová, Eva; Nohýnková, Eva; Tůmová, Pavla

    2017-01-01

    The ends of linear chromosomes, telomeres, are most commonly maintained by the enzyme telomerase. Our study presents the characteristics of telomeres and telomerase from the single-celled parasitic eukaryote Giardia intestinalis. Using fluorescence in situ hybridization, we localized telomeres during all stages of the trophozoite cell cycle and demonstrated differences in the observed number of telomeric foci, indicating telomere clustering. The length of Giardia telomeres was determined in different cell lines derived from WB clinical isolate using terminal restriction fragment analysis and ranged from 0.5 to 2.5kb; moreover, a BAL-31 digestion experiment did not reveal any long interstitial telomeric sequences in the genome. Despite the absence of the specific T motif in the telomerase catalytic subunit, the presence of an active telomerase enzyme synthesising telomeric repeats in Giardia was proved by a Telomere repeat amplification protocol assay, and its localization in nuclei was determined by the expression of recombinant GiTERT. Except for the Giardia-type TAGGG telomeric repeat, Giardia telomerase was proved to synthesize in vitro also other repeat variants, TAAGG and TAAGGG. In summary, despite its unusual characteristics, including a structurally divergent but active telomerase, unique terminal sequences and relatively short telomeres, the present data support the view that the chromosomal termini in Giardia are maintained in a conservative manner that is common to other eukaryotes. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length.

    Science.gov (United States)

    Cook, Daniel E; Zdraljevic, Stefan; Tanny, Robyn E; Seo, Beomseok; Riccardi, David D; Noble, Luke M; Rockman, Matthew V; Alkema, Mark J; Braendle, Christian; Kammenga, Jan E; Wang, John; Kruglyak, Leonid; Félix, Marie-Anne; Lee, Junho; Andersen, Erik C

    2016-09-01

    Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans. Copyright © 2016 by the Genetics Society of America.

  2. Fission Yeast Exo1 and Rqh1-Dna2 Redundantly Contribute to Resection of Uncapped Telomeres.

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    Tomoko Nanbu

    Full Text Available The uncapping of telomeres induces a DNA damage response. In Schizosaccharomyces pombe, deletion of pot1+ causes telomere uncapping and rapid telomere resection, resulting in chromosome fusion. Using the nmt-pot1-aid strain, we previously reported that Pot1 shut-off causes telomere loss and chromosome fusion in S. pombe. However, the factors responsible for the resection of uncapped telomeres remain unknown. In this study, we investigated these factors and found that concomitant deletion of rqh1+ and exo1+ alleviated the loss of telomeres following Pot1 shut-off, suggesting that Rqh1 and Exo1 are redundantly involved in the resection of uncapped telomeres. We also investigated the role of Rqh1 helicase activity and found it to be essential for the resection of uncapped telomeres. Moreover, we found that Dna2 and Exo1 function redundantly in the resection of uncapped telomeres. Taken together, these results suggest that Exo1 and Rqh1-Dna2 redundantly contribute to the resection of uncapped telomeres. Therefore, our results demonstrate that nmt-pot1-aid is an important model strain to study the role of helicases and nucleases in the resection of uncapped telomeres and to improve our understanding of DNA double-strand break repair.

  3. Computel: computation of mean telomere length from whole-genome next-generation sequencing data.

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    Lilit Nersisyan

    Full Text Available Telomeres are the ends of eukaryotic chromosomes, consisting of consecutive short repeats that protect chromosome ends from degradation. Telomeres shorten with each cell division, leading to replicative cell senescence. Deregulation of telomere length homeostasis is associated with the development of various age-related diseases and cancers. A number of experimental techniques exist for telomere length measurement; however, until recently, the absence of tools for extracting telomere lengths from high-throughput sequencing data has significantly obscured the association of telomere length with molecular processes in normal and diseased conditions. We have developed Computel, a program in R for computing mean telomere length from whole-genome next-generation sequencing data. Computel is open source, and is freely available at https://github.com/lilit-nersisyan/computel. It utilizes a short-read alignment-based approach and integrates various popular tools for sequencing data analysis. We validated it with synthetic and experimental data, and compared its performance with the previously available software. The results have shown that Computel outperforms existing software in accuracy, independence of results from sequencing conditions, stability against inherent sequencing errors, and better ability to distinguish pure telomeric sequences from interstitial telomeric repeats. By providing a highly reliable methodology for determining telomere lengths from whole-genome sequencing data, Computel should help to elucidate the role of telomeres in cellular health and disease.

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

    DEFF Research Database (Denmark)

    Rhee, David B; Ghosh, Avik; Lu, Jian

    2011-01-01

    Telomeres are nucleoprotein complexes at the ends of linear chromosomes in eukaryotes, and are essential in preventing chromosome termini from being recognized as broken DNA ends. Telomere shortening has been linked to cellular senescence and human aging, with oxidative stress as a major...... contributing factor. 7,8-Dihydro-8-oxogaunine (8-oxodG) is one of the most abundant oxidative guanine lesions, and 8-oxoguanine DNA glycosylase (OGG1) is involved in its removal. In this study, we examined if telomeric DNA is particularly susceptible to oxidative base damage and if telomere-specific factors...... affect the incision of oxidized guanines by OGG1. We demonstrated that telomeric TTAGGG repeats were more prone to oxidative base damage and repaired less efficiently than non-telomeric TG repeats in vivo. We also showed that the 8-oxodG-incision activity of OGG1 is similar in telomeric and non...

  5. Regulated expression of the lncRNA TERRA and its impact on telomere biology.

    Science.gov (United States)

    Oliva-Rico, Diego; Herrera, Luis A

    2017-10-01

    The telomere protects against genomic instability by minimizing the accelerated end resection of the genetic material, a phenomenon that results in severe chromosome instability that could favor the transformation of a cell by enabling the emergence of tumor-promoting mutations. Some mechanisms that avoid this fate, such as capping and loop formation, have been very well characterized; however, telomeric non-coding transcripts, such as long non-coding RNAs (lncRNAs), should also be considered in this context because they play roles in the organization of telomere dynamics, involving processes such as replication, degradation, extension, and heterochromatin stabilization. Although the mechanism through which the expression of telomeric transcripts regulates telomere dynamics is not yet clear, a non-coding RNA component opens the research options in telomere biology and the impact that it can have on telomere-associated diseases such as cancer. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  6. Discovery-based protein expression profiling identifies distinct subgroups and pathways in leiomyosarcomas

    DEFF Research Database (Denmark)

    Kirik, Ufuk; Hansson, Karin; Krogh, Morten

    2014-01-01

    subgroups within the leiomyosarcomas with distinct protein expression patterns. Pathways analysis indicates that key biologic nodes like apoptosis, cytoskeleton remodeling, and telomere regulation are differentially regulated among these subgroups. Finally, investigating the similarities between protein...

  7. Dynamics of telomere length in different age groups in a Latvian population.

    Science.gov (United States)

    Zole, Egija; Pliss, Liana; Ranka, Renate; Krumina, Astrida; Baumanis, Viesturs

    2013-12-01

    The shortening of telomeres with ageing is a well-documented observation; however, the reported number of nucleotides in telomeres varies between different laboratories and studies. Such variability is likely caused by ethnic differences between the populations studied. Until now, there were no studies that investigated the variability of telomere length in a senescent Latvian population of the most common mitochondrial haplogroups, defined as H (45%), U (25%), Y chromosomal N1c (40%) and R1a1 (40%). Telomere length was determined in 121 individuals in different age groups, including a control group containing individuals of 20-40 years old and groups of individuals between 60-70 years old, 71-80 years old, 81-90 years old, and above 90 years old. Telomere length was determined using the Southern blot telomeric restriction fragment assay (TRF). Decreased telomere length with ageing was confirmed, but a comparison of centenarians and individuals between 60-90 years of age did not demonstrate a significant difference in telomere length. However, significant variability in telomere length was observed in the control group, indicating probable rapid telomere shortening in some individuals that could lead up to development of health status decline appearing with ageing. Telomere length measured in mononuclear blood cells (MNC) was compared with the telomere length measured in whole peripheral white blood cells (WBC) using TRF. Telomere length in MNC was longer than in WBC for the control group with individuals 20 to 40 years old; in contrast, for the group of individuals aged 65 to 85 years old, measured telomere length was shorter in MNC when compared to WBC.

  8. Processed Meat, but Not Unprocessed Red Meat, Is Inversely Associated with Leukocyte Telomere Length in the Strong Heart Family Study.

    Science.gov (United States)

    Fretts, Amanda M; Howard, Barbara V; Siscovick, David S; Best, Lyle G; Beresford, Shirley Aa; Mete, Mihriye; Eilat-Adar, Sigal; Sotoodehnia, Nona; Zhao, Jinying

    2016-10-01

    Telomeres are repetitive nucleotide sequences (TTAGGG) and their associated proteins at the end of eukaryote chromosomes. Telomere length shortens throughout the lifespan with each cell division, and leukocyte telomere length (LTL) is often used as a biomarker of cellular aging. LTL is related to many chronic diseases, including cardiovascular disease and diabetes. However, to our knowledge, the relation between LTL and risk factors for cardiovascular disease and diabetes, such as dietary intake of processed meat and unprocessed red meat, is largely unknown. We examined the associations of processed meat intake and unprocessed red meat intake with LTL. This cross-sectional study comprised 2846 American Indians from the Strong Heart Family Study who participated in the 2001-2003 examination. Dietary factors, including past-year consumption of processed meat and unprocessed red meat, were assessed with the use of a 119-item Block Food-Frequency Questionnaire. LTL was measured with the use of quantitative polymerase chain reaction. Generalized estimating equations were used to examine the associations of intake of processed meat and unprocessed red meat with LTL. Consumption of processed meat was negatively associated with LTL after adjustment for age, sex, site, education, smoking, alcohol use, physical activity, and other dietary factors. For every additional daily serving of processed meat, LTL was 0.021 units (telomeric product-to-single-copy gene ratio) shorter (β ± SE = -0.021 ± 0.008, P = 0.009). No association was observed between the intake of unprocessed red meat and LTL (β ± SE = 0.008 ± 0.011, P = 0.46). In the Strong Heart Family Study, consumption of processed meat, but not unprocessed red meat, was associated with shorter LTL, a potential mediator for several age-related diseases. Further studies are needed to better understand the biological mechanism by which processed meat intake influences cellular aging. © 2016 American Society for Nutrition.

  9. Leukocyte telomere length and late-life depression

    NARCIS (Netherlands)

    Schaakxs, R.; Verhoeven, J.E.; Oude Voshaar, R.C.; Comijs, H.C.; Penninx, B.W.

    2015-01-01

    OBJECTIVE: Depressive disorders have been associated with increased risk for aging-related diseases, possibly as a consequence of accelerated cellular aging. Cellular aging, indexed by telomere length (TL) shortening, has been linked to depression in adults younger than 60 years; however, it remains

  10. Telomere shortening and telomerase activity in ischaemic cardiomyopathy patients

    DEFF Research Database (Denmark)

    Sawhney, V; Campbell, N G; Brouilette, S W

    2016-01-01

    with primary prevention ICDs were recruited. 35 had received appropriate therapy from the ICD for potentially-fatal VA while the remaining 55 patients had not. No significant differences in baseline demographic data relevant to telomere biology were seen between the two groups. There was no significant...

  11. T cell renewal rates, telomerase, and telomere length shortening

    NARCIS (Netherlands)

    Boer, R.J. de; Noest, A.J.

    1998-01-01

    Measurements on the average telomere lengths of normal human naive and memory T cells suggested that 1) naive and memory human T cells have similar division rates, and 2) that the difference between naive and memory cells reflects the degree of clonal expansion during normal immune reactions. Here

  12. Cellular Consequences of Telomere Shortening in Histologically Normal Breast Tissues

    Science.gov (United States)

    2011-09-01

    mechanism. Cytogenet Genome Res 2008, 122:281–291 12. Cesare AJ, Reddel RR: Alternative lengthening of telomeres: models, mechanisms and implications......astrocytomas. Clin. Cancer Res. 11, 217 (2005). Medline 21. M. A. Cerone, C. Autexier, J. A. Londoño- Vallejo , S. Bacchetti, A human cell line that maintains

  13. Longitudinal Changes in Leukocyte Telomere Length and Mortality in Humans

    DEFF Research Database (Denmark)

    Bendix, Laila; Thinggaard, Mikael; Fenger, Mogens

    2014-01-01

    Leukocyte telomere length (LTL) ostensibly shortens with age and has been moderately associated with mortality. In humans, these findings have come almost solely from cross-sectional studies. Only recently has LTL shortening within individuals been analyzed in longitudinal studies. Such studies...

  14. Traffic noise exposure affects telomere length in nestling house sparrows.

    Science.gov (United States)

    Meillère, Alizée; Brischoux, François; Ribout, Cécile; Angelier, Frédéric

    2015-09-01

    In a consistently urbanizing world, anthropogenic noise has become almost omnipresent, and there are increasing evidence that high noise levels can have major impacts on wildlife. While the effects of anthropogenic noise exposure on adult animals have been widely studied, surprisingly, there has been little consideration of the effects of noise pollution on developing organisms. Yet, environmental conditions experienced in early life can have dramatic lifelong consequences for fitness. Here, we experimentally manipulated the acoustic environment of free-living house sparrows (Passer domesticus) breeding in nest boxes. We focused on the impact of such disturbance on nestlings' telomere length and fledging success, as telomeres (the protective ends of chromosomes) appear to be a promising predictor of longevity. We showed that despite the absence of any obvious immediate consequences (growth and fledging success), nestlings reared under traffic noise exposure exhibited reduced telomere lengths compared with their unexposed neighbours. Although the mechanisms responsible for this effect remain to be determined, our results provide the first experimental evidence that noise alone can affect a wild vertebrate's early-life telomere length. This suggests that noise exposure may entail important costs for developing organisms. © 2015 The Author(s).

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

    Science.gov (United States)

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

    2014-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-06

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

  17. Genomic Organization of the Drosophila Telomere RetrotransposableElements

    Energy Technology Data Exchange (ETDEWEB)

    George, J.A.; DeBaryshe, P.G.; Traverse, K.L.; Celniker, S. E.; Pardue, M-L.

    2006-10-16

    The emerging sequence of the heterochromatic portion of the Drosophila melanogaster genome, with the most recent update of euchromatic sequence, gives the first genome-wide view of the chromosomal distribution of the telomeric retrotransposons, HeT-A, TART, and Tahre. As expected, these elements are entirely excluded from euchromatin, although sequence fragments of HeT-A and TART 3 untranslated regions are found in nontelomeric heterochromatin on the Y chromosome. The proximal ends of HeT-A/TART arrays appear to be a transition zone because only here do other transposable elements mix in the array. The sharp distinction between the distribution of telomeric elements and that of other transposable elements suggests that chromatin structure is important in telomere element localization. Measurements reported here show (1) D. melanogaster telomeres are very long, in the size range reported for inbred mouse strains (averaging 46 kb per chromosome end in Drosophila stock 2057). As in organisms with telomerase, their length varies depending on genotype. There is also slight under-replication in polytene nuclei. (2) Surprisingly, the relationship between the number of HeT-A and TART elements is not stochastic but is strongly correlated across stocks, supporting the idea that the two elements are interdependent. Although currently assembled portions of the HeT-A/TART arrays are from the most-proximal part of long arrays, {approx}61% of the total HeT-A sequence in these regions consists of intact, potentially active elements with little evidence of sequence decay, making it likely that the content of the telomere arrays turns over more extensively than has been thought.

  18. HP1-mediated formation of alternative lengthening of telomeres-associated PML bodies requires HIRA but not ASF1a.

    Directory of Open Access Journals (Sweden)

    Wei-Qin Jiang

    Full Text Available Approximately 10% of cancers use recombination-mediated Alternative Lengthening of Telomeres (ALT instead of telomerase to prevent telomere shortening. A characteristic of cells that utilize ALT is the presence of ALT-associated PML nuclear bodies (APBs containing (TTAGGGn DNA, telomere binding proteins, DNA recombination proteins, and heterochromatin protein 1 (HP1. The function of APBs is unknown and it is possible that they are functionally heterogeneous. Most ALT cells lack functional p53, and restoration of the p53/p21 pathway in these cells results in growth arrest/senescence and a substantial increase in the number of large APBs that is dependent on two HP1 isoforms, HP1α and HP1γ. Here we investigated the mechanism of HP1-mediated APB formation, and found that histone chaperones, HIRA and ASF1a, are present in APBs following activation of the p53/p21 pathway in ALT cells. HIRA and ASF1a were also found to colocalize inside PML bodies in normal fibroblasts approaching senescence, providing evidence for the existence of a senescence-associated ASF1a/HIRA complex inside PML bodies, consistent with a role for these proteins in induction of senescence in both normal and ALT cells. Moreover, knockdown of HIRA but not ASF1a significantly reduced p53-mediated induction of large APBs, with a concomitant reduction of large HP1 foci. We conclude that HIRA, in addition to its physical and functional association with ASF1a, plays a unique, ASF1a-independent role, which is required for the localization of HP1 to PML bodies and thus for APB formation.

  19. Identification of Protein Components of Yeast Telomerase

    National Research Council Canada - National Science Library

    Teng, Shu-Chun

    1998-01-01

    .... Most eukaryotes replicate telomere by a special reverse transcriptase called telomerase. Another pathway of telomere formation is telomere-telomere recombination that uses homologs either in telomeric or subtelomeric repeats as the substrates...

  20. Modified Terminal Restriction Fragment Analysis for Quantifying Telomere Length Using In-gel Hybridization.

    Science.gov (United States)

    Jenkins, Frank J; Kerr, Charles M; Fouquerel, Elise; Bovbjerg, Dana H; Opresko, Patricia L

    2017-07-10

    There are several different techniques for measuring telomere length, each with their own advantages and disadvantages. The traditional approach, Telomere Restriction Fragment (TRF) analysis, utilizes a DNA hybridization technique whereby genomic DNA samples are digested with restriction enzymes, leaving behind telomere DNA repeats and some sub-telomeric DNA. These are separated by agarose gel electrophoresis, transferred to a filter membrane and hybridized to oligonucleotide probes tagged with either chemiluminescence or radioactivity to visualize telomere restriction fragments. This approach, while requiring a larger quantity of DNA than other techniques such as PCR, can measure the telomere length distribution of a population of cells and allows measurement expressed in absolute kilobases. This manuscript demonstrates a modified DNA hybridization procedure for determining telomere length. Genomic DNA is first digested with restriction enzymes (that do not cut telomeres) and separated by agarose gel electrophoresis. The gel is then dried and the DNA is denatured and hybridized in situ to a radiolabeled oligonucleotide probe. This in situ hybridization avoids loss of telomere DNA and improves signal intensity. Following hybridization, the gels are imaged utilizing phosphor screens and the telomere length is quantified using a graphing program. This procedure was developed by the laboratories of Drs. Woodring Wright and Jerry Shay at the University of Texas Southwestern 1 , 2 . Here, we present a detailed description of this procedure, with some modifications.

  1. Significantly lengthened telomere in granulosa cells from women with polycystic ovarian syndrome (PCOS).

    Science.gov (United States)

    Wei, Duo; Xie, Juanke; Yin, Baoli; Hao, Haoying; Song, Xiaobing; Liu, Qi; Zhang, Cuilian; Sun, Yingpu

    2017-07-01

    Polycystic ovary syndrome (PCOS) is the most common endocrinopathy among women at reproductive age. However, its etiology remains poorly understood. Recent studies indicated that telomere length was related to PCOS. However, the association between telomere length and PCOS has only been shown in leucocytes and remained controversial across different studies. To clarify the association between telomere length and PCOS, the current study interrogated telomere length not only in leucocytes, but also in follicular granulosa cells, which is essential for folliculogenesis and steroidogenesis. Seventy-five patients with PCOS and 81 controls with mechanical infertility undergoing their first in vitro fertilization cycle were enrolled. Their peripheral blood and granulosa cells were collected on the oocyte retrieval day. Telomere length of both leucocytes in the blood and granulosa cells was assayed by quantitative polymerase chain reaction. No significant difference was found in the leucocyte telomere length between controls and PCOS patients (0.99 ± 0.44 vs. 1.00 ± 0.38, p = 0.93). Interestingly, when comparing telomere length in granulosa cells between controls and PCOS subjects, significantly lengthened telomere length was found in PCOS subjects (1.00 ± 0.37 vs. 1.57±0.67, p PCOS. Given the importance of telomere length in cellular proliferation, our findings provided novel insights into the pathophysiology of PCOS that abnormalities in telomere length possibly disturb folliculogenesis and subsequently result in PCOS.

  2. Paclitaxel stimulates chromosomal fusion and instability in cells with dysfunctional telomeres: Implication in multinucleation and chemosensitization

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeong-Eun [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Woo, Seon Rang [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Department of Biochemistry, College of Medicine, Korea University, Seoul 136-705 (Korea, Republic of); Kang, Chang-Mo [Laboratory of Cytogenetics and Tissue Regeneration, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Juhn, Kyoung-Mi; Ju, Yeun-Jin; Shin, Hyun-Jin; Joo, Hyun-Yoo; Park, Eun Ran; Park, In-chul; Hong, Sung Hee; Hwang, Sang-Gu [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of); Lee, Jung-Kee [Department of Life Science and Genetic Engineering, Paichai University, Daejeon 302-735 (Korea, Republic of); Kim, Hae Kwon [Department of Biotechnology, Seoul Woman' s University, Seoul 139-774 (Korea, Republic of); Cho, Myung-Haing [Laboratory of Toxicology, College of Veterinary Medicine, Seoul National University, Seoul 151-74-2 (Korea, Republic of); Park, Gil Hong [Department of Biochemistry, College of Medicine, Korea University, Seoul 136-705 (Korea, Republic of); Lee, Kee-Ho, E-mail: khlee@kirams.re.kr [Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706 (Korea, Republic of)

    2011-01-14

    Research highlights: {yields} Paclitaxel serves as a stimulator of chromosomal fusion in cells in which telomeres are dysfunctional. {yields} Typical fusions involve p-arms, but paclitaxel-induced fusions occur between both q- and p-arms. {yields} Paclitaxel-stimulated fusions in cells in which telomeres are dysfunctional evoke prolonged G2/M cell cycle arrest and delay multinucleation. {yields} Upon telomere erosion, paclitaxel promotes chromosomal instability and subsequent apoptosis. {yields} Chromosomal fusion enhances paclitaxel chemosensitivity under telomere dysfunction. -- Abstract: The anticancer effect of paclitaxel is attributable principally to irreversible promotion of microtubule stabilization and is hampered upon development of chemoresistance by tumor cells. Telomere shortening, and eventual telomere erosion, evoke chromosomal instability, resulting in particular cellular responses. Using telomerase-deficient cells derived from mTREC-/-p53-/- mice, here we show that, upon telomere erosion, paclitaxel propagates chromosomal instability by stimulating chromosomal end-to-end fusions and delaying the development of multinucleation. The end-to-end fusions involve both the p- and q-arms in cells in which telomeres are dysfunctional. Paclitaxel-induced chromosomal fusions were accompanied by prolonged G2/M cell cycle arrest, delayed multinucleation, and apoptosis. Telomere dysfunctional cells with mutlinucleation eventually underwent apoptosis. Thus, as telomere erosion proceeds, paclitaxel stimulates chromosomal fusion and instability, and both apoptosis and chemosensitization eventually develop.

  3. Comparative analysis of whole genome sequencing-based telomere length measurement techniques.

    Science.gov (United States)

    Lee, Michael; Napier, Christine E; Yang, Sile F; Arthur, Jonathan W; Reddel, Roger R; Pickett, Hilda A

    2017-02-01

    Telomeres are regions of repetitive DNA at the ends of human chromosomes that function to maintain the integrity of the genome. Telomere attrition is associated with cellular ageing, whilst telomere maintenance is a prerequisite for malignant transformation. Whole genome sequencing (WGS) captures sequence information from the entire genome, including the telomeres, and is increasingly being applied in research and in the clinic. Several bioinformatics tools have been designed to determine telomere content and length from WGS data, and include Motif_counter, TelSeq, Computel, qMotif, and Telomerecat. These tools utilise different approaches to identify, quantify and normalise telomeric reads; however, it is not known how they compare to one another. Here we describe the details and utility of each tool, and directly compare WGS telomere length output with laboratory-based telomere length measurements. In addition, we evaluate the accessibility, practicality, speed, and additional features of each tool. Each tool was tested using a range of telomere read extraction criteria, to determine the optimal parameters for the specific WGS read length. The aim of this article is to improve the accessibility of WGS telomere length measurement tools, which have the potential to be applied to WGS cohorts for clinical as well as research benefit. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Telomere-Centromere-Driven Genomic Instability Contributes to Karyotype Evolution in a Mouse Model of Melanoma

    Directory of Open Access Journals (Sweden)

    Amanda Gonçalves dos Santos Silva

    2010-01-01

    Full Text Available Aneuploidy and chromosomal instability (CIN are hallmarks of most solid tumors. These alterations may result from inaccurate chromosomal segregation during mitosis, which can occur through several mechanisms including defective telomere metabolism, centrosome amplification, dysfunctional centromeres, and/or defective spindle checkpoint control. In this work, we used an in vitro murine melanoma model that uses a cellular adhesion blockade as a transforming factor to characterize telomeric and centromeric alterations that accompany melanocyte transformation. To study the timing of the occurrence of telomere shortening in this transformation model, we analyzed the profile of telomere length by quantitative fluorescent in situ hybridization and found that telomere length significantly decreased as additional rounds of cell adhesion blockages were performed. Together with it, an increase in telomere-free ends and complex karyotypic aberrations were also found, which include Robertsonian fusions in 100% of metaphases of the metastatic melanoma cells. These findings are in agreement with the idea that telomere length abnormalities seem to be one of the earliest genetic alterations acquired in the multistep process of malignant transformation and that telomere abnormalities result in telomere aggregation, breakage-bridge-fusion cycles, and CIN. Another remarkable feature of this model is the abundance of centromeric instability manifested as centromere fragments and centromeric fusions. Taken together, our results illustrate for this melanoma model CIN with a structural signature of centromere breakage and telomeric loss.

  5. Skin phenotypes can offer some insight about the association between telomere length and cancer susceptibility.

    Science.gov (United States)

    Ribero, S; Mangino, M; Bataille, V

    2016-12-01

    The role of telomere biology in cancer has been studied for a wide variety of different cancers but the association with telomere length has been controversial. This is because some cancers have been found to be associated with longer telomeres in circulating white cells whilst other cancer types are more common in individuals with shorter telomeres. Hence, there has been some skepticism as to whether telomere length may be helpful in estimating cancer risk. For melanoma, however, results have been fairly consistent showing that longer telomeres are associated with an increased risk. This link was first discovered because of a link between longer telomeres and a high number of naevi. In contrast, for cutaneous squamous cell carcinomas, the relationship is reversed with higher risk in individuals with shorter telomeres. Differences in skin phenotypes with the presence of high number of naevi versus photoageing with solar elastosis and solar keratoses have already been valuable for dermatologists as the former phenotype is associated with melanoma whilst the latter is more common in patients with squamous cell carcinoma of the skin. The hypothesis is that the differences in cutaneous phenotypes already observed by dermatologists for skin cancers may, in fact, be useful as well for cancer prediction in general as it may reflect underlying telomere biology. This manuscript will address the evidence for links between telomere biology, skin phenotypes and cancer risk. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2015-06-01

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

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    Porro, Antonio; Feuerhahn, Sascha; Lingner, Joachim

    2014-02-27

    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. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  9. Association of telomere length in older men with mortality and midlife body mass index and smoking.

    Science.gov (United States)

    Strandberg, Timo E; Saijonmaa, Outi; Tilvis, Reijo S; Pitkälä, Kaisu H; Strandberg, Arto Y; Miettinen, Tatu A; Fyhrquist, Frej

    2011-07-01

    Leukocyte telomere length has been taken as a measure of biological age but several inconsistencies exist. We investigated associations between leukocyte telomere length in old age, midlife risk factors, and mortality. The Helsinki Businessmen Study (a cohort of mainly business executives, born 1919-1934) had baseline assessments of cardiovascular risk factors including body mass index between 1964 and 1973 at a mean age of 40. Leukocyte telomere length and proportion of short telomeres were measured from DNA samples collected in 2002-2003 (n = 622, mean age 78 years). Body mass index and smoking in old age were assessed from questionnaires. Total mortality was verified from registers through January 2010. Main outcome measures were relationships between telomeres, body mass index, smoking, and mortality. Leukocyte telomere length and notably proportion of short telomeres (associated with midlife overweight and smoking. The associations were independent of age and cardiovascular risk factors including postload glucose. Associations with body mass index and smoking were nonsignificant in old age, and telomere length did not predict 7-year total mortality. We conclude that smoking and overweight in midlife, irrespective of glucose, cholesterol and blood pressure, are related to shorter leukocyte telomeres in old men. Telomere length in old age did not predict total mortality possibly due to competing causes.

  10. Processive and Distributive Extension of Human Telomeres by Telomerase Under Homeostatic and Non-equilibrium Conditions

    Science.gov (United States)

    Zhao, Yong; Abreu, Eladio; Kim, Jinyong; Stadler, Guido; Eskiocak, Ugur; Terns, Michael P.; Terns, Rebecca M.; Shay, Jerry W.; Wright, Woodring E.

    2011-01-01

    SUMMARY Specific information about how telomerase acts in vivo is necessary for understanding telomere dynamics in human tumor cells. Our results imply that under homeostatic telomere length-maintenance conditions only one molecule of telomerase acts at each telomere during every cell division and processively adds ~60 nt to each end. In contrast, multiple molecules of telomerase act at each telomere when telomeres are elongating (non-equilibrium conditions). Telomerase extension is less processive during the first few weeks following the reversal of long-term treatment with the telomerase inhibitor GRN163L, a time when Cajal bodies fail to deliver telomerase RNA to telomeres. This result implies that processing of telomerase by Cajal bodies may affect its processivity. Overexpressed telomerase is also less processive than the endogenously expressed telomerase. These findings reveal two major distinct extension modes adopted by telomerase in vivo. PMID:21549308

  11. Effects of donor cells' sex on nuclear transfer efficiency and telomere lengths of cloned goats.

    Science.gov (United States)

    Liu, H-J; Peng, H; Hu, C-C; Li, X-Y; Zhang, J-L; Zheng, Z; Zhang, W-C

    2016-10-01

    The aim of this study was to investigate the effects of donor cells' sex on nuclear transfer efficiency and telomere length of cloned goats from adult skin fibroblast cells. The telomere length of somatic cell cloned goats and their offspring was determined by measuring their mean terminal restriction fragment (TRF) length. The result showed that (i) reconstructed embryos with fibroblast cells from males Boer goats obtained significantly higher kids rate and rate of live kids than those of female embryos and (ii) the telomere lengths of four female cloned goats were shorter compared to their donor cells, but five male cloned goats had the same telomere length with their donor cells, mainly due to great variation existed among them. The offspring from female cloned goats had the same telomere length with their age-matched counterparts. In conclusion, the donor cells' sex had significant effects on nuclear transfer efficiency and telomere lengths of cloned goats. © 2016 Blackwell Verlag GmbH.

  12. Longer leukocyte telomere length in Costa Rica's Nicoyan Peninsula: A population-based study

    Science.gov (United States)

    Rehkopf, David H; Dow, William H; Rosero-Bixby, Luis; Lin, Jue; Epel, Elissa S; Blackburn, Elizabeth H

    2013-01-01

    Studies in humans suggest that leukocyte telomere length may act as a marker of biological aging. We investigated whether individuals in the Nicoya region of Costa Rica, known for exceptional longevity, had longer telomere length than those in other parts of the country. After controlling for age, age squared, rurality, rainy season and gender, mean leukocyte telomere length in Nicoya was substantially longer (81 base pairs, pCosta Rica, providing evidence of a biological pathway to which this notable longevity may be related. This relationship remains unchanged (79 base pairs, p<0.05) after statistically controlling for nineteen potential biological, dietary and social and demographic mediators. Thus the difference in mean leukocyte telomere length that characterizes this unique region does not appear to be explainable by traditional behavioral and biological risk factors. More detailed examination of mean leukocyte telomere length by age shows that the regional telomere length difference declines at older ages. PMID:23988653

  13. Age-dependence of relative telomere length profiles during spermatogenesis in man

    DEFF Research Database (Denmark)

    Jørgensen, Pernille Bach; Fedder, Jens; Koelvraa, Steen

    2013-01-01

    Telomeres, the protective structures at the outmost ends of chromosomes, shorten in all somatic cells with each cell-division and by cumulative oxidative damage. To counteract that these shortened telomeres are passed on to offspring, the telomeres are elongated by the enzyme, telomerase, during...... human spermatogenesis. A few groups have tried to elucidate this process by measuring telomerase activity in the various cell-types during spermatogenesis, but until now, no one has ever measured telomere length (TL) during these different stages in humans. Some groups have measured TL in spermatozoa...... by telomere QFISH. Our data revealed no difference in the TL profile during spermatogenesis between younger and older men. All men had a similar profile which strongly resembled the telomerase expression profile found by others. This indicates that the longer telomeres in older men are not caused by a wider...

  14. Paternal age and telomere length in twins: the germ stem cell selection paradigm

    Science.gov (United States)

    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-dependent germ stem cell selection process, whereby the selected stem cells have longer telomeres, are more homogenous with respect to telomere length, and share resistance to aging. PMID:25865872

  15. Cinnamaldehyde and eugenol change the expression folds of AKT1 and DKC1 genes and decrease the telomere length of human adipose-derived stem cells (hASCs: An experimental and in silico study

    Directory of Open Access Journals (Sweden)

    Abdorrahim Absalan

    2017-03-01

    Full Text Available Objective(s: To investigate the effect of cinnamaldehyde and eugenol on the telomere-dependent senescence of stem cells. In addition, to search the probable targets of mentioned phytochemicals between human telomere interacting proteins (TIPs using in silico studies. Materials and Methods: Human adipose derived stem cells (hASCs were studied under treatments with 2.5 µM/ml cinnamaldehyde, 0.1 µg/ml eugenol, 0.01% DMSO or any additive. The expression of TERT, AKT1 and DKC1 genes and the telomere length were assessed over 48-hr treatment. In addition, docking study was conducted to show probable ways through which phytochemicals interact with TIPs. Results: Treated and untreated hASCs had undetectable TERT expression, but they did affect the AKT1 and DKC1 expression levels (CI=0.95; P

  16. Long telomeres are associated with clonality in wild populations of the fissiparous starfish Coscinasterias tenuispina

    OpenAIRE

    García-Cisneros, Álex; Pérez-Portela, R.; Almroth, B. C.; Degerman, S; Palacín, Carlos; Sköld, H Nilsson

    2015-01-01

    Telomeres usually shorten during an organism’s lifespan and have thus been used as an aging and health marker. When telomeres become sufficiently short, senescence is induced. The most common method of restoring telomere length is via telomerase reverse transcriptase activity, highly expressed during embryogenesis. However, although asexual reproduction from adult tissues has an important role in the life cycles of certain species, its effect on the aging and fitness of wild populati...

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

    Directory of Open Access Journals (Sweden)

    Patrick J Rochette

    2010-04-01

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

  18. The effects of oxidative stress on telomeres and cell life span

    OpenAIRE

    Pańczyszyn, Anna; Boniewska-Bernacka, Ewa

    2016-01-01

    Oxidative stress is associated with excessive amounts of reactive oxygen species (ROSOS) in the body. The sources of ROSOS constitute the respiratory chain, immune system cells and external factors, e.g. smoking. ROSOS may cause damage and faster shortening of nucleoprotein structures called telomeres, which protect chromosome ends. The consequence of faster shortening of telomeres is aging and death of cells. The aim of this paper was to present the impact of ROSOS on the rate of telomere sh...

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

    Directory of Open Access Journals (Sweden)

    Owen M Wolkowitz

    2011-03-01

    Full Text Available Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of "accelerated aging" in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD, whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation.Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio and inflammation (IL-6. Analyses were controlled for age and sex.The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05. Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration was 281 base pairs shorter than that in controls (p<0.05, corresponding to approximately seven years of "accelerated cell aging." Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01 and in the controls (p<0.05 and with inflammation in the depressed subjects (p<0.05.These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression and is not an intrinsic feature. Rather, telomere shortening

  20. Everything You Ever Wanted to Know About Saccharomyces cerevisiae Telomeres: Beginning to End

    Science.gov (United States)

    Zakian, Virginia A.

    2012-01-01

    The mechanisms that maintain the stability of chromosome ends have broad impact on genome integrity in all eukaryotes. Budding yeast is a premier organism for telomere studies. Many fundamental concepts of telomere and telomerase function were first established in yeast and then extended to other organisms. We present a comprehensive review of yeast telomere biology that covers capping, replication, recombination, and transcription. We think of it as yeast telomeres—soup to nuts. PMID:22879408

  1. No Association between Mean Telomere Length and Life Stress Observed in a 30 Year Birth Cohort

    OpenAIRE

    Sarah Jodczyk; Fergusson, David M; John Horwood, L.; Pearson, John F; Martin A Kennedy

    2014-01-01

    Telomeres are specialised structures that cap the ends of chromosomes. They shorten with each cell division and have been proposed as a marker of cellular aging. Previous studies suggest that early life stressors increase the rate of telomere shortening with potential impact on disease states and mortality later in life. This study examined the associations between telomere length and exposure to a number of stressors that arise during development from the antenatal/perinatal period through t...

  2. Telomere dynamics in a long-lived bird, the barnacle goose

    Directory of Open Access Journals (Sweden)

    Pauliny Angela

    2012-12-01

    Full Text Available Abstract Background Theories of ageing predict a trade-off between metabolism, reproduction, and maintenance. Species with low investment in early reproduction are thus expected to be able to evolve more efficient maintenance and repair mechanisms, allowing for a longer potential life span (intrinsic longevity. The erosion of telomeres, the protective caps at the ends of linear chromosomes, plays an important role in cellular and organismal senescence, signalling the onset of age-related disease due to accumulation of unrepaired somatic damage. Using extensive longitudinal data from a long-term study of a natural population of barnacle geese Branta leucopsis, we investigated individual rates of telomere length changes over two years in 34 birds between 0 and 22 years of age, covering almost 80% of the species’ lifespan. Results We show that telomeres in this long-lived bird are very well maintained, as theoretically expected, with an average loss rate of only 5 base pairs per year among adults. We thus found no significant relationship between change in telomere length and age. However, telomeres tended to shorten at a faster pace in juveniles compared to adults. For the first time, we demonstrate a faster telomere attrition rate in females compared to males. We found no correlation between telomere loss rate and adult survival or change in body mass. Conclusions Our results add further support for a link between longevity and telomere maintenance, and highlight the complexities of telomere dynamics in natural populations.

  3. Telomeres are elongated in older individuals in a hibernating rodent, the edible dormouse (Glis glis).

    Science.gov (United States)

    Hoelzl, Franz; Smith, Steve; Cornils, Jessica S; Aydinonat, Denise; Bieber, Claudia; Ruf, Thomas

    2016-11-24

    Telomere shortening is thought to be an important biomarker for life history traits such as lifespan and aging, and can be indicative of genome integrity, survival probability and the risk of cancer development. In humans and other animals, telomeres almost always shorten with age, with more rapid telomere attrition in short-lived species. Here, we show that in the edible dormouse (Glis glis) telomere length significantly increases from an age of 6 to an age of 9 years. While this finding could be due to higher survival of individuals with longer telomeres, we also found, using longitudinal measurements, a positive effect of age on the rate of telomere elongation within older individuals. To our knowledge, no previous study has reported such an effect of age on telomere lengthening. We attribute this exceptional pattern to the peculiar life-history of this species, which skips reproduction in years with low food availability. Further, we show that this "sit tight" strategy in the timing of reproduction is associated with an increasing likelihood for an individual to reproduce as it ages. As reproduction could facilitate telomere attrition, this life-history strategy may have led to the evolution of increased somatic maintenance and telomere elongation with increasing age.

  4. Neighborhood characteristics and leukocyte telomere length: the Multi-Ethnic Study of Atherosclerosis.

    Science.gov (United States)

    Needham, Belinda L; Carroll, Judith E; Diez Roux, Ana V; Fitzpatrick, Annette L; Moore, Kari; Seeman, Teresa E

    2014-07-01

    Telomeres are the protective caps at the ends of eukaryotic chromosomes. Telomeres get shorter each time a cell divides, and critically shortened telomeres trigger cellular senescence. Thus, telomere length is hypothesized to be a biological marker of aging. The purpose of this study was to examine the association between neighborhood characteristics and leukocyte telomere length. Using data from a subsample (n=978) of the Multi-Ethnic Study of Atherosclerosis, a population-based study of women and men aged 45-84, we found that neighborhood social environment (but not neighborhood socioeconomic disadvantage) was associated with telomere length. Respondents who lived in neighborhoods characterized by lower aesthetic quality, safety, and social cohesion had shorter telomeres than those who lived in neighborhoods with a more salutary social environment, even after adjusting for individual-level socioeconomic status and biomedical and lifestyle factors related to telomere length. Telomere length may be one biological mechanism by which neighborhood characteristics influence an individual׳s risk of disease and death. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Telomere dysfunction in peripheral blood lymphocytes from patients with primary sclerosing cholangitis and inflammatory bowel disease.

    Science.gov (United States)

    Laish, Ido; Katz, Hila; Stein, Assaf; Liberman, Meytal; Naftali, Timna; Kitay-Cohen, Yona; Biron-Shental, Tal; Konikoff, Fred M; Amiel, Aliza

    2015-09-01

    Primary sclerosing cholangitis and inflammatory bowel disease are two associated, chronic inflammatory, pre-malignant conditions. We hypothesized that patients with these disorders may harbour telomere dysfunction as a marker of chromosomal instability. The aim of our study was to compare parameters of the telomere-telomerase system in these cohorts. In this prospective study, peripheral blood was withdrawn from patients with primary sclerosing cholangitis (N=20), inflammatory bowel disease (N=20) and healthy controls (N=20), and lymphocytes were isolated. Telomere length was quantified as a function of the signal intensity and telomere number. Random aneuploidy and telomere capture were determined by fluorescence in situ hybridization technique with specific probes. Patients with inflammatory bowel disease had higher measures of intestinal disease activity than patients with primary sclerosing cholangitis. Despite this, shorter telomere length and telomere aggregates, especially the fusion of 2-5 telomeres, were observed at significantly higher rate in patients with primary sclerosing cholangitis relative to inflammatory bowel disease or healthy controls. Rates of aneuploidy and telomere capture were higher in the two probes in both diseases compared to controls (pprimary sclerosing cholangitis patients more than inflammatory bowel disease and healthy controls patients, which attests to genetic instability and immunosenescence. NCT02247622. Copyright © 2015 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

  6. Diet quality and telomere length in older Australian men and women.

    Science.gov (United States)

    Milte, Catherine M; Russell, Aaron P; Ball, Kylie; Crawford, David; Salmon, Jo; McNaughton, Sarah A

    2016-10-26

    Telomere length is a biomarker of cellular ageing, with longer telomeres associated with longevity and reduced risk of chronic disease in older age. Consumption of a healthy diet may contribute to longevity via its impact on cellular ageing, but studies on diet and telomere length to date have been limited and their findings equivocal. The aim of this study was to examine associations between three indices of diet quality and telomere length in older men and women. Adults aged 57-68 years participating in the Wellbeing, Eating and Exercise for a Long Life (WELL) study in Victoria, Australia (n = 679), completed a postal survey including an 111-item food frequency questionnaire in 2012. Diet quality was assessed via three indices: the Dietary Guideline Index, the Recommended Food Score, and the Mediterranean Diet Score. Relative telomere length was measured by quantitative polymerase chain reaction. Associations between diet quality and telomere length were assessed using linear regression adjusted for covariates. After adjustment for age, sex, education, smoking, physical activity, and body mass index (BMI), there were no significant associations between diet quality and relative telomere length. In a sample of older adults residing in Victoria, Australia, men and women aged 57-68 years with better-quality diets did not have longer telomeres. Further investigation in longitudinal studies will determine whether diet can influence telomere length over time in an ageing population.

  7. Frequency of Chromosome Healing and Interstitial Telomeres in 40 Cases of Constitutional Abnormalities

    National Research Council Canada - National Science Library

    Fortin, F; Beaulieu Bergeron, M; Fetni, R; Lemieux, N

    2009-01-01

    .... In order to determine the frequency at which interstitial telomeres or chromosome healing events are observed in target chromosome abnormalities, we conducted a retrospective FISH study using pan...

  8. Telomeres shorten and then lengthen before fledging in Magellanic penguins (Spheniscus magellanicus).

    Science.gov (United States)

    Cerchiara, Jack A; Risques, Rosa Ana; Prunkard, Donna; Smith, Jeffrey R; Kane, Olivia J; Boersma, P Dee

    2017-02-08

    For all species, finite metabolic resources must be allocated toward three competing systems: maintenance, reproduction, and growth. Telomeres, the nucleoprotein tips of chromosomes, which shorten with age in most species, are correlated with increased survival. Chick growth is energetically costly and is associated with telomere shortening in most species. To assess the change in telomeres in penguin chicks, we quantified change in telomere length of wild known-age Magellanic penguin ( Spheniscus magellanicus ) chicks every 15 days during the species' growth period, from hatching to 60 days-of-age. Magellanic penguins continue to grow after fledging so we also sampled a set of 1-year-old juvenile penguins, and adults aged 5 years. Telomeres were significantly shorter on day 15 than on hatch day but returned to their initial length by 30 days old and remained at that length through 60 days of age. The length of telomeres of newly hatched chicks, chicks aged 30, 45 and 60 days, juveniles, and adults aged 5 years were similar. Chicks that fledged and those that died had similar telomere lengths. We show that while telomeres shorten during growth, Magellanic penguins elongate telomeres to their length at hatch, which may increase adult life span and reproductive opportunities.

  9. Short telomere length, cancer survival, and cancer risk in 47102 individuals

    DEFF Research Database (Denmark)

    Weischer, Maren; Nordestgaard, Børge G; Cawthon, Richard M

    2013-01-01

    Recent meta-analyses have suggested that short telomere length was associated with increased risk of cancer. We therefore tested the hypotheses that short telomere length was associated with increased risk of cancer and with increased risk of early death after cancer.......Recent meta-analyses have suggested that short telomere length was associated with increased risk of cancer. We therefore tested the hypotheses that short telomere length was associated with increased risk of cancer and with increased risk of early death after cancer....

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Telomere Length Determines TERRA and R-Loop Regulation through the Cell Cycle.

    Science.gov (United States)

    Graf, Marco; Bonetti, Diego; Lockhart, Arianna; Serhal, Kamar; Kellner, Vanessa; Maicher, André; Jolivet, Pascale; Teixeira, Maria Teresa; Luke, Brian

    2017-06-29

    Maintenance of a minimal telomere length is essential to prevent cellular senescence. When critically short telomeres arise in the absence of telomerase, they can be repaired by homology-directed repair (HDR) to prevent premature senescence onset. It is unclear why specifically the shortest telomeres are targeted for HDR. We demonstrate that the non-coding RNA TERRA accumulates as HDR-promoting RNA-DNA hybrids (R-loops) preferentially at very short telomeres. The increased level of TERRA and R-loops, exclusively at short telomeres, is due to a local defect in RNA degradation by the Rat1 and RNase H2 nucleases, respectively. Consequently, the coordination of TERRA degradation with telomere replication is altered at shortened telomeres. R-loop persistence at short telomeres contributes to activation of the DNA damage response (DDR) and promotes recruitment of the Rad51 recombinase. Thus, the telomere length-dependent regulation of TERRA and TERRA R-loops is a critical determinant of the rate of replicative senescence. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Telomere dynamics in a long-lived bird, the barnacle goose.

    Science.gov (United States)

    Pauliny, Angela; Larsson, Kjell; Blomqvist, Donald

    2012-12-31

    Theories of ageing predict a trade-off between metabolism, reproduction, and maintenance. Species with low investment in early reproduction are thus expected to be able to evolve more efficient maintenance and repair mechanisms, allowing for a longer potential life span (intrinsic longevity). The erosion of telomeres, the protective caps at the ends of linear chromosomes, plays an important role in cellular and organismal senescence, signalling the onset of age-related disease due to accumulation of unrepaired somatic damage. Using extensive longitudinal data from a long-term study of a natural population of barnacle geese Branta leucopsis, we investigated individual rates of telomere length changes over two years in 34 birds between 0 and 22 years of age, covering almost 80% of the species' lifespan. We show that telomeres in this long-lived bird are very well maintained, as theoretically expected, with an average loss rate of only 5 base pairs per year among adults. We thus found no significant relationship between change in telomere length and age. However, telomeres tended to shorten at a faster pace in juveniles compared to adults. For the first time, we demonstrate a faster telomere attrition rate in females compared to males. We found no correlation between telomere loss rate and adult survival or change in body mass. Our results add further support for a link between longevity and telomere maintenance, and highlight the complexities of telomere dynamics in natural populations.

  14. Telomere sister chromatid exchange and the process of aging.

    Science.gov (United States)

    Blagoev, Krastan B; Goodwin, Edwin H; Bailey, Susan M

    2010-10-01

    Telomeres are a hotspot for sister chromatid exchange (T-SCE). Any biological consequence of this form of instability remained obscure until quantitative modeling revealed a link between elevated T-SCE rates and accelerated cellular replicative senescence. This work strongly suggests that progressive telomere erosion is not the only determinant of replicative capacity; instead, T-SCE need to be considered as an independent factor controlling colony growth and senescence. Additionally high T-SCE rates have been observed in cells with deficiencies in WRN and BLM, the genes that are defective in Werner's and Bloom's syndromes, implying a connection to premature aging. In this Research Perspective we will explore some of the implications this recent work has for human health.

  15. Telomere length of anterior crucial ligament after rupture

    DEFF Research Database (Denmark)

    Ponsot, Elodie; Langberg, Henning; Krogsgaard, Michael R

    2011-01-01

    of human anterior cruciate ligament (ACL) obtained during ACL reconstruction: the macroscopically injured proximal part and macroscopically noninjured mid- and distal portions in eight subjects (age 28 ± 8 years). The mean telomere length in ACL was within normal range of values usually reported for other......The regeneration of ligaments following injury is a slow process compared to the healing of many other tissues and the underlying mechanisms remain unknown. The purpose of the study was to evaluate the proliferative potential of ligaments by assessing telomere length within three distinct parts...... tissues indicating that the endogenous machinery responsible for the proliferative potential of ligament is not implicated in its poor healing capacity. The three ACL parts showed similar mean TRF lengths (distal part: 11.5 ± 0.8 kbp, mid-portion: 11.8 ± 1.2 kbp, proximal part: 11.9 ± 1.6 kbp...

  16. Accelerated telomere shortening in response to life stress.

    Science.gov (United States)

    Epel, Elissa S; Blackburn, Elizabeth H; Lin, Jue; Dhabhar, Firdaus S; Adler, Nancy E; Morrow, Jason D; Cawthon, Richard M

    2004-12-07

    Numerous studies demonstrate links between chronic stress and indices of poor health, including risk factors for cardiovascular disease and poorer immune function. Nevertheless, the exact mechanisms of how stress gets "under the skin" remain elusive. We investigated the hypothesis that stress impacts health by modulating the rate of cellular aging. Here we provide evidence that psychological stress--both perceived stress and chronicity of stress--is significantly associated with higher oxidative stress, lower telomerase activity, and shorter telomere length, which are known determinants of cell senescence and longevity, in peripheral blood mononuclear cells from healthy premenopausal women. Women with the highest levels of perceived stress have telomeres shorter on average by the equivalent of at least one decade of additional aging compared to low stress women. These findings have implications for understanding how, at the cellular level, stress may promote earlier onset of age-related diseases.

  17. Telomere length is longer in women with late maternal age

    DEFF Research Database (Denmark)

    Fagan, Erin; Sun, Fangui; Bae, Harold

    2017-01-01

    years or less. METHODS:: A nested case control study was conducted using data from the Long Life Family Study. Three hundred eighty-seven women who gave birth to at least one child and lived to the top fifth percentile of their birth cohort, or died before the top fifth percentile of their birth cohort......OBJECTIVE:: Maternal age at birth of last child has been associated with maternal longevity. The aim of this study was to determine whether older women with a history of late maternal age at last childbirth had a longer leukocyte telomere length than those with maternal age at last childbirth of 29...... died, but were at least 70 years old, were studied. Logistic regression models using generalized estimating equations were used to determine the association between tertiles of telomere length and maternal age at last childbirth, adjusting for covariates. RESULTS:: Age at birth of the last child...

  18. Seasonal variation in telomere length of a hibernating rodent

    OpenAIRE

    Turbill, Christopher; Ruf, Thomas; Smith, Steve; Bieber, Claudia

    2013-01-01

    Small hibernating rodents have greater maximum lifespans and hence appear to age more slowly than similar-sized non-hibernators. We tested for a direct effect of hibernation on somatic maintenance and ageing by measuring seasonal changes in relative telomere length (RTL) in the edible dormouse Glis glis. Average RTL in our population did not change significantly over the hibernation season, and a regression model explaining individual variation in post-hibernation RTL suggested a significant ...

  19. Relationship between physical activity level, telomere length, and telomerase activity.

    Science.gov (United States)

    Ludlow, Andrew T; Zimmerman, Jo B; Witkowski, Sarah; Hearn, Joe W; Hatfield, Bradley D; Roth, Stephen M

    2008-10-01

    The purpose of this study was to examine the relationship of exercise energy expenditure (EEE) with both telomere length and telomerase activity in addition to accounting for hTERT C-1327T promoter genotype. Sixty-nine (n = 34 males; n = 35 females) participants 50-70 yr were assessed for weekly EEE level using the Yale Physical Activity Survey. Lifetime consistency of EEE was also determined. Subjects were recruited across a large range of EEE levels and separated into quartiles: 0-990, 991-2340, 2341-3540, and >3541 kcal x wk(-1). Relative telomere length and telomerase activity were measured in peripheral blood mononuclear cells (PBMC). The second EEE quartile exhibited significantly longer telomere lengths [1.12 +/- 0.03 relative units (RU)] than both the first and fourth EEE quartiles (0.94 +/- 0.03 and 0.96 +/- 0.03 RU, respectively; P EEE quartiles. An association was observed between telomerase enzyme activity and hTERT genotype with the TT genotype (1.0 x 10(-2) +/- 4.0 x 10(-3) attomoles (amol) per 10,000 cells; n = 19) having significantly greater telomerase enzyme activity than both the CT (1.3 x 10(-3) +/- 3.2 x 10(-3); n = 30) and CC groups (5.0 x 10(-4) +/- 3.9 x 10(-3); n = 20; P = 0.01). These results indicate that moderate physical activity levels may provide a protective effect on PBMC telomere length compared with both low and high EEE levels.

  20. Seasonal variation in telomere length of a hibernating rodent.

    Science.gov (United States)

    Turbill, Christopher; Ruf, Thomas; Smith, Steve; Bieber, Claudia

    2013-04-23

    Small hibernating rodents have greater maximum lifespans and hence appear to age more slowly than similar-sized non-hibernators. We tested for a direct effect of hibernation on somatic maintenance and ageing by measuring seasonal changes in relative telomere length (RTL) in the edible dormouse Glis glis. Average RTL in our population did not change significantly over the hibernation season, and a regression model explaining individual variation in post-hibernation RTL suggested a significant negative effect of the reduction in body mass over the inactive hibernation period (an index of time spent euthermic), supporting the idea that torpor slows ageing. Over the active season, RTL on average decreased in sub-adults but increased in adults, supporting previous findings of greater telomere shortening at younger ages. Telomere length increase might also have been associated with reproduction, which occurred only in adults. Our study reveals how seasonal changes in physiological state influence the progress of life-history traits, such as somatic maintenance and ageing, in a small hibernating rodent.

  1. Telomeric Repeat Containing RNA (TERRA): Aging and Cancer.

    Science.gov (United States)

    Sinha, Sonam; Shukla, Samriddhi; Khan, Sajid; Farhan, Mohammad; Kamal, Mohammad Amjad; Meeran, Syed Musthapa

    2015-01-01

    Telomeric repeat containing RNAs (TERRA) are small RNA molecules synthesized from telomeric regions which were previously considered as silent genomic domains. In normal cells, these RNAs are transcribed in a direction from subtelomeric region towards the chromosome ends, but in case of cancer cells, their expression remains limited or absent. Telomerase is a rate limiting enzyme for cellular senescence, cancer and aging. Most of the studies deal with the manipulation of telomerase enzyme in cancer and aging either by synthetic oligonucleotide or by natural phytochemicals. Here, we collected evidences and discussed intensely about the bio-molecular structure of TERRA, naturally occurring ligands of telomerase, and their genetic and epigenetic regulations in aging associated diseases. Due to their capability to act as naturally occurring ligands of telomerase, these RNAs can overcome the limitations possessed by synthetic oligonucleotides, which are aimed against telomerase. Drugs specifically targeting TERRA molecules could modulate telomerase-mediated telomere lengthening. Thus, targeting TERRA-mediated regulation of telomerase would be a promising therapeutic strategy against cancer and age-associated diseases.

  2. The telomeric sync model of speciation: species-wide telomere erosion triggers cycles of transposon-mediated genomic rearrangements, which underlie the saltatory appearance of nonadaptive characters

    Science.gov (United States)

    Stindl, Reinhard

    2014-03-01

    Charles Darwin knew that the fossil record is not overwhelmingly supportive of genetic and phenotypic gradualism; therefore, he developed the core of his theory on the basis of breeding experiments. Here, I present evidence for the existence of a cell biological mechanism that strongly points to the almost forgotten European concept of saltatory evolution of nonadaptive characters, which is in perfect agreement with the gaps in the fossil record. The standard model of chromosomal evolution has always been handicapped by a paradox, namely, how speciation can occur by spontaneous chromosomal rearrangements that are known to decrease the fertility of heterozygotes in a population. However, the hallmark of almost all closely related species is a differing chromosome complement and therefore chromosomal rearrangements seem to be crucial for speciation. Telomeres, the caps of eukaryotic chromosomes, erode in somatic tissues during life, but have been thought to remain stable in the germline of a species. Recently, a large human study spanning three healthy generations clearly found a cumulative telomere effect, which is indicative of transgenerational telomere erosion in the human species. The telomeric sync model of speciation presented here is based on telomere erosion between generations, which leads to identical fusions of chromosomes and triggers a transposon-mediated genomic repatterning in the germline of many individuals of a species. The phenotypic outcome of the telomere-triggered transposon activity is the saltatory appearance of nonadaptive characters simultaneously in many individuals. Transgenerational telomere erosion is therefore the material basis of aging at the species level.

  3. A dynamic meiotic SUN belt includes the zygotene-stage telomere bouquet and is disrupted in chromosome segregation mutants of maize (Zea mays L..

    Directory of Open Access Journals (Sweden)

    Shaun Patrick Murphy

    2014-07-01

    Full Text Available The nuclear envelope (NE plays an essential role in meiotic telomere behavior and links the cytoplasm and nucleoplasm during homologous chromosome pairing and recombination in many eukaryotic species. Resident NE proteins including SUN (Sad-1/UNC-84 and KASH (Klarsicht/ANC-1/Syne-homology domain proteins are known to interact forming the Linker of Nucleoskeleton and Cytoskeleton (LINC complex that connects chromatin to the cytoskeleton. To investigate the possible cross-kingdom conservation of SUN protein functions in plant meiosis, we immunolocalized maize SUN2 using 3D microscopy of pollen mother cells from maize (Zea mays L., a large-genome plant model with a canonical NE zygotene-stage telomere bouquet. We detected SUN2 at the nuclear periphery and found that it exhibited a distinct belt-like structure that transitioned to a half-belt during the zygotene stage and back to a full belt during and beyond the pachytene stage. The zygotene-stage half-belt SUN structure was shown by 3D immuno-FISH to include the NE-associated telomere cluster that defines the bouquet stage and coincides with homologous chromosome synapsis. Microtubule and filamentous actin staining patterns did not show any obvious belt or a retracted-like structure other than a general enrichment of tubulin staining distributed widely around the nucleus and throughout the cytoplasm. Genetic disruption of the meiotic SUN belt staining patterns with three different meiosis-specific mutants, desynaptic (dy1, asynaptic1 (as1, and divergent spindle1 (dv1 provides additional evidence for the role of the nuclear envelope in meiotic chromosome behavior. Taking into account all of the observations from this study, we propose that the maize SUN belt is directly or indirectly involved in meiotic telomere dynamics, chromosome synapsis, and possibly integration of signals and forces across the meiotic prophase nuclear envelope.

  4. The Roles of Chromosome Breaks and Telomere Dynamics in the Genomic Instability Associated with Human Breast Cancer

    National Research Council Canada - National Science Library

    Wilson, John

    2000-01-01

    ... of telomeres from chromosome ends. Loss of telomeres allows chromosomes to fuse end-to-end, triggering chromosome fusion-bridge-breakage cycles that lead to genome rearrangements, loss of heterozyg