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Sample records for dysfunctional mammalian telomeres

  1. Mammalian telomeres and their partnership with lamins

    PubMed Central

    Burla, Romina; La Torre, Mattia; Saggio, Isabella

    2016-01-01

    ABSTRACT Chromosome ends are complex structures, which require a panel of factors for their elongation, replication, and protection. We describe here the mechanics of mammalian telomeres, dynamics and maintainance in relation to lamins. Multiple biochemical connections, including association of telomeres to the nuclear envelope and matrix, of telomeric proteins to lamins, and of lamin-associated proteins to chromosome ends, underline the interplay between lamins and telomeres. Paths toward senescence, such as defective telomere replication, altered heterochromatin organization, and impaired DNA repair, are common to lamins' and telomeres' dysfunction. The convergence of phenotypes can be interpreted through a model of dynamic, lamin-controlled functional platforms dedicated to the function of telomeres as fragile sites. The features of telomeropathies and laminopathies, and of animal models underline further overlapping aspects, including the alteration of stem cell compartments. We expect that future studies of basic biology and on aging will benefit from the analysis of this telomere-lamina interplay. PMID:27116558

  2. Telomere dysfunction and chromothripsis.

    PubMed

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

    2016-06-15

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

  3. 53BP1 mediates the fusion of mammalian telomeres rendered dysfunctional by DNA-PKcs loss or inhibition.

    PubMed

    Rybanska-Spaeder, Ivana; Ghosh, Rajib; Franco, Sonia

    2014-01-01

    Telomere dysfunction promotes genomic instability and carcinogenesis via inappropriate end-to-end chromosomal rearrangements, or telomere fusions. Previous work indicates that the DNA Damage Response (DDR) factor 53BP1 promotes the fusion of telomeres rendered dysfunctional by loss of TRF2, but is dispensable for the fusion of telomeres lacking Pot1 or critically shortened (in telomerase-deficient mice). Here, we examine a role for 53BP1 at telomeres rendered dysfunctional by loss or catalytic inhibition of DNA-PKcs. Using mouse embryonic fibroblasts lacking 53BP1 and/or DNA-PKcs, we show that 53BP1 deficiency suppresses G1-generated telomere fusions that normally accumulate in DNA-PKcs-deficient fibroblasts with passage. Likewise, we find that 53BP1 promotes telomere fusions during the replicative phases of the cell cycle in cells treated with the specific DNA-PKcs inhibitor NU7026. However, telomere fusions are not fully abrogated in DNA-PKcs-inhibited 53BP1-deficient cells, but occur with a frequency approximately 10-fold lower than in control 53BP1-proficient cells. Treatment with PARP inhibitors or PARP1 depletion abrogates residual fusions, while Ligase IV depletion has no measurable effect, suggesting that PARP1-dependent alternative end-joining operates at low efficiency at 53BP1-deficient, DNA-PKcs-inhibited telomeres. Finally, we have also examined the requirement for DDR factors ATM, MDC1 or H2AX in this context. We find that ATM loss or inhibition has no measurable effect on the frequency of NU7026-induced fusions in wild-type MEFs. Moreover, analysis of MEFs lacking both ATM and 53BP1 indicates that ATM is also dispensable for telomere fusions via PARP-dependent end-joining. In contrast, loss of either MDC1 or H2AX abrogates telomere fusions in response to DNA-PKcs inhibition, suggesting that these factors operate upstream of both 53BP1-dependent and -independent telomere rejoining. Together, these experiments define a novel requirement for 53BP1 in

  4. [Telomere Recombination in Normal Mammalian Cells].

    PubMed

    Zhdanova, N S; Rubtsov, N B

    2016-01-01

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

  5. Telomere Dysfunction Induced Foci (TIF) Analysis

    PubMed Central

    Mender, Ilgen; Shay, Jerry W.

    2016-01-01

    Telomerase maintains telomeric DNA in eukaryotes during early developments, ~90% of cancer cells and some proliferative stem like cells. Telomeric repeats at the end of chromosomes are associated with the shelterin complex. This complex consists of TRF1, TRF2, Rap1, TIN2, TPP1, POT1 which protect DNA from being recognized as DNA double-stranded breaks. Critically short telomeres or impaired shelterin proteins can cause telomere dysfunction, which eventually induces DNA damage responses at the telomeres. DNA damage responses can be identified by antibodies to 53BP1, gammaH2AX, Rad17, ATM, and Mre11. DNA damage foci at uncapped telomeres are referred to as Telomere dysfunction-Induced Foci (TIFs) (de Lange, 2005; Takai et al., 2003). The TIF assay is based on the co-localization detection of DNA damage by an antibody against DNA damage markers, such as gamma-H2AX, and telomeres using an antibody against one of the shelterin proteins such as TRF2 (Takai et al., 2003; de Lange, 2002; Karlseder et al., 1999). The method we describe here can be used in normal human and cancer cells. Other commonly used methods-Telomere Restriction Fragment (TRF) Analysis (Mender and Shay, 2015b) and Telomere Repeat Amplification Protocol (TRAP) (Mender and Shay, 2015a)- in telomere biology can be found by clicking on the indicated links.

  6. Telomere-telomere interactions and candidate telomere binding protein(s) in mammalian sperm cells.

    PubMed

    Zalensky, A O; Tomilin, N V; Zalenskaya, I A; Teplitz, R L; Bradbury, E M

    1997-04-10

    We have used fluorescent in situ hybridization to localize telomeres within the nuclei of sperm from six mammals (human, rat, mouse, stallion, boar, and bull). In minimally swollen sperm of mouse and rat, most of the telomeres are clustered within a limited area in the posterior part of nuclei. In sperm of other species, telomeres associate into tetrameres and dimers. On swelling of sperm cells with heparin/dithiotriethol, telomere associations disperse, and hybridization signals become smaller in size and their numbers approach or correspond to the number of chromosome ends in a haploid genome. Quantitation of telomere loci indicates that dimeric associations are prominent features of mammalian sperm nuclear architecture. Higher order telomere-telomere interactions and organization develop during meiotic stages of human spermatogenesis. At this stage, telomeres also become associated with the nuclear membrane. In an attempt to elucidate the molecular mechanisms underlying telomere interactions in sperm, we have identified a novel protein activity that binds to the double-stranded telomeric repeat (TTAGGG)n. Sperm telomere binding protein(s) (STBP) was extracted from human and bull sperm by 0.5 M NaCl. STBP does not bind single-stranded telomeric DNA and is highly specific for single base substitutions in a duplex DNA sequence. Depending on the conditions of binding, we observed the formation of several nucleoprotein complexes. We have shown that there is a transition between complexes, which indicates that the slower migrating complex is a multimer of the higher mobility one. We propose that STBP participates in association between the telomere domains which were microscopically observed in mammalian spermatozoa. PMID:9141618

  7. Telomere dysfunction causes alveolar stem cell failure.

    PubMed

    Alder, Jonathan K; Barkauskas, Christina E; Limjunyawong, Nathachit; Stanley, Susan E; Kembou, Frant; Tuder, Rubin M; Hogan, Brigid L M; Mitzner, Wayne; Armanios, Mary

    2015-04-21

    Telomere syndromes have their most common manifestation in lung disease that is recognized as idiopathic pulmonary fibrosis and emphysema. In both conditions, there is loss of alveolar integrity, but the underlying mechanisms are not known. We tested the capacity of alveolar epithelial and stromal cells from mice with short telomeres to support alveolar organoid colony formation and found that type 2 alveolar epithelial cells (AEC2s), the stem cell-containing population, were limiting. When telomere dysfunction was induced in adult AEC2s by conditional deletion of the shelterin component telomeric repeat-binding factor 2, cells survived but remained dormant and showed all the hallmarks of cellular senescence. Telomere dysfunction in AEC2s triggered an immune response, and this was associated with AEC2-derived up-regulation of cytokine signaling pathways that are known to provoke inflammation in the lung. Mice uniformly died after challenge with bleomycin, underscoring an essential role for telomere function in AEC2s for alveolar repair. Our data show that alveoloar progenitor senescence is sufficient to recapitulate the regenerative defects, inflammatory responses, and susceptibility to injury that are characteristic of telomere-mediated lung disease. They suggest alveolar stem cell failure is a driver of telomere-mediated lung disease and that efforts to reverse it may be clinically beneficial. PMID:25840590

  8. Postnatal telomere dysfunction induces cardiomyocyte cell-cycle arrest through p21 activation.

    PubMed

    Aix, Esther; Gutiérrez-Gutiérrez, Óscar; Sánchez-Ferrer, Carlota; Aguado, Tania; Flores, Ignacio

    2016-06-01

    The molecular mechanisms that drive mammalian cardiomyocytes out of the cell cycle soon after birth remain largely unknown. Here, we identify telomere dysfunction as a critical physiological signal for cardiomyocyte cell-cycle arrest. We show that telomerase activity and cardiomyocyte telomere length decrease sharply in wild-type mouse hearts after birth, resulting in cardiomyocytes with dysfunctional telomeres and anaphase bridges and positive for the cell-cycle arrest protein p21. We further show that premature telomere dysfunction pushes cardiomyocytes out of the cell cycle. Cardiomyocytes from telomerase-deficient mice with dysfunctional telomeres (G3 Terc(-/-)) show precocious development of anaphase-bridge formation, p21 up-regulation, and binucleation. In line with these findings, the cardiomyocyte proliferative response after cardiac injury was lost in G3 Terc(-/-) newborns but rescued in G3 Terc(-/-)/p21(-/-) mice. These results reveal telomere dysfunction as a crucial signal for cardiomyocyte cell-cycle arrest after birth and suggest interventions to augment the regeneration capacity of mammalian hearts. PMID:27241915

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

    PubMed Central

    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

  10. Telomere homeostasis in mammalian germ cells: a review.

    PubMed

    Reig-Viader, Rita; Garcia-Caldés, Montserrat; Ruiz-Herrera, Aurora

    2016-06-01

    Telomeres protect against genome instability and participate in chromosomal movements during gametogenesis, especially in meiosis. Thus, maintaining telomere structure and telomeric length is essential to both cell integrity and the production of germ cells. As a result, alteration of telomere homeostasis in the germ line may result in the generation of aneuploid gametes or gametogenesis disruption, triggering fertility problems. In this work, we provide an overview on fundamental aspects of the literature regarding the organization of telomeres in mammalian germ cells, paying special attention to telomere structure and function, as well as the maintenance of telomeric length during gametogenesis. Moreover, we discuss the different roles recently described for telomerase and TERRA in maintaining telomere functionality. Finally, we review how new findings in the field of reproductive biology underscore the role of telomere homeostasis as a potential biomarker for infertility. Overall, we anticipate that the study of telomere stability and equilibrium will contribute to improve diagnoses of patients; assess the risk of infertility in the offspring; and in turn, find new treatments. PMID:26525972

  11. Telomere dysfunction drives aberrant hematopoietic differentiation and Myelodysplastic Syndrome

    PubMed Central

    Colla, Simona; Ong, Derrick Sek Tong; Ogoti, Yamini; Marchesini, Matteo; Mistry, Nipun A.; Clise-Dwyer, Karen; Ang, Sonny A.; Storti, Paola; Viale, Andrea; Giuliani, Nicola; Ruisaard, Kathryn; Gomez, Irene Ganan; Bristow, Christopher A.; Estecio, Marcos; Weksberg, David C.; Ho, Yan Wing; Hu, Baoli; Genovese, Giannicola; Pettazzoni, Piergiorgio; Multani, Asha S.; Jiang, Shan; Hua, Sujun; Ryan, Michael C.; Carugo, Alessandro; Nezi, Luigi; Wei, Yue; Yang, Hui; D’Anca, Marianna; Zhang, Li; Gaddis, Sarah; Gong, Ting; Horner, James W.; Heffernan, Timothy P.; Jones, Philip; Cooper, Laurence J.N.; Liang, Han; Kantarjian, Hagop; Wang, Y. Alan; Chin, Lynda; Bueso-Ramos, Carlos; Garcia-Manero, Guillermo; DePinho, Ronald A.

    2015-01-01

    SUMMARY Myelodysplastic syndrome (MDS) risk correlates with advancing age, therapy-induced DNA damage, and/or shorter telomeres but whether telomere erosion directly induces MDS is unknown. Here, we provide the genetic evidence that telomere dysfunction-induced DNA damage drives classical MDS phenotypes and alters common myeloid progenitor (CMP) differentiation by repressing the expression of mRNA splicing/processing genes, including srsf2. RNA-Seq analyses of telomere dysfunctional CMP identified aberrantly spliced transcripts linked to pathways relevant to MDS pathogenesis such as genome stability, DNA repair, chromatin remodeling and histone modification, which are also enriched in mouse CMP haploinsufficient for srsf2 and in CD34+ CMML patient cells harboring srsf2 mutation. Together, our studies establish an intimate link across telomere biology, aberrant RNA splicing and myeloid progenitor differentiation. PMID:25965571

  12. 53BP1 deficiency combined with telomere dysfunction activates ATR-dependent DNA damage response.

    PubMed

    Martínez, Paula; Flores, Juana M; Blasco, Maria A

    2012-04-16

    TRF1 protects mammalian telomeres from fusion and fragility. Depletion of TRF1 leads to telomere fusions as well as accumulation of γ-H2AX foci and activation of both the ataxia telangiectasia mutated (ATM)- and the ataxia telangiectasia and Rad3 related (ATR)-mediated deoxyribonucleic acid (DNA) damage response (DDR) pathways. 53BP1, which is also present at dysfunctional telomeres, is a target of ATM that accumulates at DNA double-strand breaks and favors nonhomologous end-joining (NHEJ) repair over ATM-dependent resection and homology-directed repair (homologous recombination [HR]). To address the role of 53BP1 at dysfunctional telomeres, we generated mice lacking TRF1 and 53BP1. 53BP1 deficiency significantly rescued telomere fusions in mouse embryonic fibroblasts (MEFs) lacking TRF1, but they showed evidence of a switch from the NHEJ- to HR-mediated repair of uncapped telomeres. Concomitantly, double-mutant MEFs showed evidence of hyperactivation of the ATR-dependent DDR. In intact mice, combined 53BP1/TRF1 deficiency in stratified epithelia resulted in earlier onset of DNA damage and increased CHK1 phosphorylation during embryonic development, leading to aggravation of skin phenotypes. PMID:22508511

  13. Telomere dysfunction and Tumor Suppression-the Senescence Connection

    PubMed Central

    Deng, Yibin; Chan, Suzanne; Chang, Sandy

    2013-01-01

    Long lived organisms such as humans have evolved several intrinsic tumor suppressor mechanisms to combat the slew of oncogenic somatic mutations that constantly arise in proliferating stem cell compartments. One of these anti-cancer barriers is the telomere, a specialized nucleoprotein that caps the ends of eukaryotic chromosome. Impaired telomere function activates the canonical DNA damage response pathway that engages p53 to initiate apoptosis or replicative senescence. Here, we discuss how p53-dependent senescence induced by dysfunctional telomeres may be as potent as apoptosis in suppressing tumorigenesis in vivo. PMID:18500246

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

    PubMed

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

    2013-11-01

    Human tumors using the alternative lengthening of telomeres (ALT) exert high rates of telomere dysfunction. Numerical chromosomal aberrations are very frequent, and structural rearrangements are widely scattered among the genome. This challenging context allows the study of telomere dysfunction-driven chromosomal instability in neoplasia (CIN) in a massive scale. We used molecular cytogenetics to achieve detailed karyotyping in 10 human ALT neoplastic cell lines. We identified 518 clonal recombinant chromosomes affected by 649 structural rearrangements. While all human chromosomes were involved in random or clonal, terminal, or pericentromeric rearrangements and were capable to undergo telomere healing at broken ends, a differential recombinatorial propensity of specific genomic regions was noted. We show that ALT cells undergo epigenetic modifications rendering polycentric chromosomes functionally monocentric, and because of increased terminal recombinogenicity, they generate clonal recombinant chromosomes with interstitial telomeric repeats. Losses of chromosomes 13, X, and 22, gains of 2, 3, 5, and 20, and translocation/deletion events involving several common chromosomal fragile sites (CFSs) were recurrent. Long-term reconstitution of telomerase activity in ALT cells reduced significantly the rates of random ongoing telomeric and pericentromeric CIN. However, the contribution of CFS in overall CIN remained unaffected, suggesting that in ALT cells whole-genome replication stress is not suppressed by telomerase activation. Our results provide novel insights into ALT-driven CIN, unveiling in parallel specific genomic sites that may harbor genes critical for ALT cancerous cell growth. PMID:24339742

  15. Polymerases ε and ∂ repair dysfunctional telomeres facilitated by salt

    PubMed Central

    Ivanova, Iglika G.; Maringele, Laura

    2016-01-01

    Damaged DNA can be repaired by removal and re-synthesis of up to 30 nucleotides during base or nucleotide excision repair. An important question is what happens when many more nucleotides are removed, resulting in long single-stranded DNA (ssDNA) lesions. Such lesions appear on chromosomes during telomere damage, double strand break repair or after the UV damage of stationary phase cells. Here, we show that long single-stranded lesions, formed at dysfunctional telomeres in budding yeast, are re-synthesized when cells are removed from the telomere-damaging environment. This process requires Pol32, an accessory factor of Polymerase δ. However, re-synthesis takes place even when the telomere-damaging conditions persist, in which case the accessory factors of both polymerases δ and ε are required, and surprisingly, salt. Salt added to the medium facilitates the DNA synthesis, independently of the osmotic stress responses. These results provide unexpected insights into the DNA metabolism and challenge the current view on cellular responses to telomere dysfunction. PMID:26883631

  16. Oxidative Stress Induces Persistent Telomeric DNA Damage Responsible for Nuclear Morphology Change in Mammalian Cells

    PubMed Central

    Coluzzi, Elisa; Colamartino, Monica; Cozzi, Renata; Leone, Stefano; Meneghini, Carlo; O’Callaghan, Nathan; Sgura, Antonella

    2014-01-01

    One main function of telomeres is to maintain chromosome and genome stability. The rate of telomere shortening can be accelerated significantly by chemical and physical environmental agents. Reactive oxygen species are a source of oxidative stress and can produce modified bases (mainly 8-oxoG) and single strand breaks anywhere in the genome. The high incidence of guanine residues in telomeric DNA sequences makes the telomere a preferred target for oxidative damage. Our aim in this work is to evaluate whether chromosome instability induced by oxidative stress is related specifically to telomeric damage. We treated human primary fibroblasts (MRC-5) in vitro with hydrogen peroxide (100 and 200 µM) for 1 hr and collected data at several time points. To evaluate the persistence of oxidative stress-induced DNA damage up to 24 hrs after treatment, we analysed telomeric and genomic oxidative damage by qPCR and a modified comet assay, respectively. The results demonstrate that the genomic damage is completely repaired, while the telomeric oxidative damage persists. The analysis of telomere length reveals a significant telomere shortening 48 hrs after treatment, leading us to hypothesise that residual telomere damage could be responsible for the telomere shortening observed. Considering the influence of telomere length modulation on genomic stability, we quantified abnormal nuclear morphologies (Nucleoplasmic Bridges, Nuclear Buds and Micronuclei) and observed an increase of chromosome instability in the same time frame as telomere shortening. At subsequent times (72 and 96 hrs), we observed a restoration of telomere length and a reduction of chromosome instability, leaving us to conjecture a correlation between telomere shortening/dysfunction and chromosome instability. We can conclude that oxidative base damage leads to abnormal nuclear morphologies and that telomere dysfunction is an important contributor to this effect. PMID:25354277

  17. Mammalian Ku86 mediates chromosomal fusions and apoptosis caused by critically short telomeres

    PubMed Central

    Espejel, Silvia; Franco, Sonia; Rodríguez-Perales, Sandra; Bouffler, Simon D.; Cigudosa, Juan C.; Blasco, María A.

    2002-01-01

    Here we analyze the functional interaction between Ku86 and telomerase at the mammalian telomere by studying mice deficient for both proteins. We show that absence of Ku86 prevents the end-to-end chromosomal fusions that result from critical telomere shortening in telomerase-deficient mice. In addition, Ku86 deficiency rescues the male early germ cell apoptosis triggered by short telomeres in these mice. Together, these findings define a role for Ku86 in mediating chromosomal instability and apoptosis triggered by short telomeres. In addition, we show here that Ku86 deficiency results in telomerase-dependent telomere elongation and in the fusion of random pairs of chromosomes in telomerase-proficient cells, suggesting a model in which Ku86 keeps normal-length telomeres less accessible to telomerase- mediated telomere lengthening and to DNA repair activities. PMID:11980718

  18. Paclitaxel stimulates chromosomal fusion and instability in cells with dysfunctional telomeres: Implication in multinucleation and chemosensitization

    SciTech Connect

    Park, Jeong-Eun; Woo, Seon Rang; Kang, Chang-Mo; Juhn, Kyoung-Mi; Ju, Yeun-Jin; Shin, Hyun-Jin; Joo, Hyun-Yoo; Park, Eun Ran; Park, In-chul; Hong, Sung Hee; Hwang, Sang-Gu; Lee, Jung-Kee; Kim, Hae Kwon; Cho, Myung-Haing; Park, Gil Hong; Lee, Kee-Ho

    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.

  19. TeloPIN: a database of telomeric proteins interaction network in mammalian cells.

    PubMed

    Luo, Zhenhua; Dai, Zhiming; Xie, Xiaowei; Feng, Xuyang; Liu, Dan; Songyang, Zhou; Xiong, Yuanyan

    2015-01-01

    Interaction network surrounding telomeres has been intensively studied during the past two decades. However, no specific resource by integrating telomere interaction information data is currently available. To facilitate the understanding of the molecular interaction network by which telomeres are associated with biological process and diseases, we have developed TeloPIN (Telomeric Proteins Interaction Network) database (http://songyanglab.sysu.edu.cn/telopin/), a novel database that points to provide comprehensive information on protein-protein, protein-DNA and protein-RNA interaction of telomeres. TeloPIN database contains four types of interaction data, including (i) protein--protein interaction (PPI) data, (ii) telomeric proteins ChIP-seq data, (iii) telomere-associated proteins data and (iv) telomeric repeat-containing RNAs (TERRA)-interacting proteins data. By analyzing these four types of interaction data, we found that 358 and 199 proteins have more than one type of interaction information in human and mouse cells, respectively. We also developed table browser and TeloChIP genome browser to help researchers with better integrated visualization of interaction data from different studies. The current release of TeloPIN database includes 1111 PPI, eight telomeric protein ChIP-seq data sets, 1391 telomere-associated proteins and 183 TERRA-interacting proteins from 92 independent studies in mammalian cells. The interaction information provided by TeloPIN database will greatly expand our knowledge of telomeric proteins interaction network. PMID:25792605

  20. Chronic inflammation induces telomere dysfunction and accelerates ageing in mice

    PubMed Central

    Jurk, Diana; Wilson, Caroline; Passos, João F.; Oakley, Fiona; Correia-Melo, Clara; Greaves, Laura; Saretzki, Gabriele; Fox, Chris; Lawless, Conor; Anderson, Rhys; Hewitt, Graeme; Pender, Sylvia LF; Fullard, Nicola; Nelson, Glyn; Mann, Jelena; van de Sluis, Bart; Mann, Derek A.; von Zglinicki, Thomas

    2014-01-01

    Chronic inflammation is associated with normal and pathological ageing. Here we show that chronic, progressive low-grade inflammation induced by knockout of the nfkb1 subunit of the transcription factor NF-κB induces premature ageing in mice. We also show that these mice have reduced regeneration in liver and gut. nfkb1−/− fibroblasts exhibit aggravated cell senescence because of an enhanced autocrine and paracrine feedback through NF-κB, COX-2 and ROS, which stabilizes DNA damage. Preferential accumulation of telomere-dysfunctional senescent cells in nfkb1−/− tissues is blocked by anti-inflammatory or antioxidant treatment of mice, and this rescues tissue regenerative potential. Frequencies of senescent cells in liver and intestinal crypts quantitatively predict mean and maximum lifespan in both short- and long-lived mice cohorts. These data indicate that systemic chronic inflammation can accelerate ageing via ROS-mediated exacerbation of telomere dysfunction and cell senescence in the absence of any other genetic or environmental factor. PMID:24960204

  1. Differential impact of telomere dysfunction on initiation and progression of hepatocellular carcinoma.

    PubMed

    Farazi, Paraskevi A; Glickman, Jonathan; Jiang, Shan; Yu, Alice; Rudolph, Karl Lenhard; DePinho, Ronald A

    2003-08-15

    Telomere maintenance and telomerase reactivation are near universal features of human hepatocellular carcinoma (HCC), yet the shorter telomeres and highly abnormal cytogenetic profiles of HCC suggest that telomere erosion and dysfunction may be operative during the formative stages of tumorigenesis. Previous studies have established that the cancer-enhancing or suppressing impact of telomere dysfunction is highly dependent on several parameters including cell type, tumor stage, and p53 status. Here, to understand better the pathogenetic role of telomere dysfunction in the initiation and progression in human HCC, we have used three mechanistically distinct liver cancer-prone model systems (urokinase plasminogen activator transgenic mice, carbon tetrachloride exposure, and diethylnistrosamine treatment) in the context of successive generations of telomerase-deficient mice null for the telomerase RNA component, mTERC. Across all of the HCC model systems, telomere dysfunction suppressed both the incidence and growth of HCC lesions, a trend that mirrored the level of intratumoral proliferative arrest and apoptosis. On the histological level, telomere dysfunction was associated with a significant increase in the number of early stage neoplastic lesions and a reciprocal decline in the occurrence of high-grade malignancies. These genetic data in the mouse indicate that telomere dysfunction exerts an opposing role in the initiation versus progression of HCC and provide a framework for understanding the intimate link among chronic liver disease, chromosomal instability, and increased HCC in humans. PMID:12941829

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

    PubMed

    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. PMID:26712234

  3. The crosstalk of telomere dysfunction and inflammation through cell-free TERRA containing exosomes.

    PubMed

    Wang, Zhuo; Lieberman, Paul M

    2016-08-01

    Telomeric repeats-containing RNA (TERRA) are telomere-derived non-coding RNAs that contribute to telomere function in protecting chromosome ends. We recently identified a cell-free form of TERRA (cfTERRA) enriched in extracellular exosomes. These cfTERRA-containing exosomes stimulate inflammatory cytokines when incubated with immune responsive cells. Here, we report that cfTERRA levels were increased in exosomes during telomere dysfunction induced by the expression of the dominant negative TRF2. The exosomes from these damaged cells also enriched with DNA damage marker γH2AX and fragmented telomere repeat DNA. Purified cfTERRA stimulated inflammatory cytokines, but the intact membrane-associated nucleoprotein complexes produced a more robust cytokine activation. Therefore, we propose cfTERRA-containing exosomes transport a telomere-associated molecular pattern (TAMP) and telomere-specific alarmin from dysfunctional telomeres to the extracellular environment to elicit an inflammatory response. Since cfTERRA can be readily detected in human serum it may provide a useful biomarker for the detection of telomere dysfunction in the early stage of cancers and aging-associated inflammatory disease. PMID:27351774

  4. Complex interactions between the DNA-damage response and mammalian telomeres

    PubMed Central

    Arnoult, Nausica; Karlseder, Jan

    2016-01-01

    Natural chromosome ends resemble double-stranded DNA breaks, but they do not activate a damage response in healthy cells. Telomeres therefore have evolved to solve the ‘end-protection problem’ by inhibiting multiple DNA damage–response pathways. During the past decade, the view of telomeres has progressed from simple caps that hide chromosome ends to complex machineries that have an active role in organizing the genome. Here we focus on mammalian telomeres and summarize and interpret recent discoveries in detail, focusing on how repair pathways are inhibited, how resection and replication are controlled and how these mechanisms govern cell fate during senescence, crisis and transformation. PMID:26581520

  5. Oncogene-induced telomere dysfunction enforces cellular senescence in human cancer precursor lesions

    PubMed Central

    Suram, Anitha; Kaplunov, Jessica; Patel, Priyanka L; Ruan, Haihe; Cerutti, Aurora; Boccardi, Virginia; Fumagalli, Marzia; Di Micco, Raffaella; Mirani, Neena; Gurung, Resham Lal; Hande, Manoor Prakash; d'Adda di Fagagna, Fabrizio; Herbig, Utz

    2012-01-01

    In normal human somatic cells, telomere dysfunction causes cellular senescence, a stable proliferative arrest with tumour suppressing properties. Whether telomere dysfunction-induced senescence (TDIS) suppresses cancer growth in humans, however, is unknown. Here, we demonstrate that multiple and distinct human cancer precursor lesions, but not corresponding malignant cancers, are comprised of cells that display hallmarks of TDIS. Furthermore, we demonstrate that oncogenic signalling, frequently associated with initiating cancer growth in humans, dramatically affected telomere structure and function by causing telomeric replication stress, rapid and stochastic telomere attrition, and consequently telomere dysfunction in cells that lack hTERT activity. DNA replication stress induced by drugs also resulted in telomere dysfunction and cellular senescence in normal human cells, demonstrating that telomeric repeats indeed are hypersensitive to DNA replication stress. Our data reveal that TDIS, accelerated by oncogene-induced DNA replication stress, is a biological response of cells in human cancer precursor lesions and provide strong evidence that TDIS is a critical tumour suppressing mechanism in humans. PMID:22569128

  6. Role of TERRA in the Regulation of Telomere Length

    PubMed Central

    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. PMID:25678850

  7. TeloPIN: a database of telomeric proteins interaction network in mammalian cells

    PubMed Central

    Luo, Zhenhua; Dai, Zhiming; Xie, Xiaowei; Feng, Xuyang; Liu, Dan; Songyang, Zhou; Xiong, Yuanyan

    2015-01-01

    Interaction network surrounding telomeres has been intensively studied during the past two decades. However, no specific resource by integrating telomere interaction information data is currently available. To facilitate the understanding of the molecular interaction network by which telomeres are associated with biological process and diseases, we have developed TeloPIN (Telomeric Proteins Interaction Network) database (http://songyanglab.sysu.edu.cn/telopin/), a novel database that points to provide comprehensive information on protein–protein, protein–DNA and protein–RNA interaction of telomeres. TeloPIN database contains four types of interaction data, including (i) protein–protein interaction (PPI) data, (ii) telomeric proteins ChIP-seq data, (iii) telomere-associated proteins data and (iv) telomeric repeat-containing RNAs (TERRA)-interacting proteins data. By analyzing these four types of interaction data, we found that 358 and 199 proteins have more than one type of interaction information in human and mouse cells, respectively. We also developed table browser and TeloChIP genome browser to help researchers with better integrated visualization of interaction data from different studies. The current release of TeloPIN database includes 1111 PPI, eight telomeric protein ChIP-seq data sets, 1391 telomere-associated proteins and 183 TERRA-interacting proteins from 92 independent studies in mammalian cells. The interaction information provided by TeloPIN database will greatly expand our knowledge of telomeric proteins interaction network. Database URL: TeloPIN database address is http://songyanglab.sysu.edu.cn/telopin. TeloPIN database is freely available to non-commercial use. PMID:25792605

  8. Induction of Telomere Dysfunction Mediated By the Telomerase Substrate Precursor 6-Thio-2’-Deoxyguanosine

    PubMed Central

    Mender, Ilgen; Gryaznov, Sergei; Dikmen, Zeliha G.; Wright, Woodring E.; Shay, Jerry W.

    2014-01-01

    The relationships between telomerase and telomeres represent attractive targets for new anti-cancer agents. Here, we report that the nucleoside analogue 6-thio-2’-deoxyguanosine (6-thio-dG) is recognized by telomerase and is incorporated into de novo synthesized telomeres. This results in modified telomeres, leading to telomere dysfunction, but only in cells expressing telomerase. 6-thio-dG, but not 6-thioguanine, induces telomere dysfunction in telomerase positive human cancer cells and hTERT expressing human fibroblasts, but not in telomerase negative cells. Treatment with 6-thio-dG resulted in rapid cell death for the vast majority of the cancer cell lines tested, whereas normal human fibroblasts and human colonic epithelial cells were largely unaffected. In A549 lung cancer cell-based mouse xenograft studies, 6-thio-dG caused a decrease of the tumor growth rate, superior to that observed with 6-thioguanine treatment. Additionally, 6-thio-dG increased telomere dysfunction in tumor cells in vivo. These results indicate that 6-thio-dG may provide a new telomere-addressed telomerase-dependent anti-cancer approach. PMID:25516420

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

    SciTech Connect

    Cosme-Blanco, Wilfredo; Chang, Sandy

    2008-06-10

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

  10. Role of Telomere Dysfunction in Cardiac Failure in Duchenne Muscular Dystrophy

    PubMed Central

    Mourkioti, Foteini; Kustan, Jackie; Kraft, Peggy; Day, John W.; Zhao, Ming-Ming; Kost-Alimova, Maria; Protopopov, Alexei; DePinho, Ronald A.; Bernstein, Daniel; Meeker, Alan K.; Blau, Helen M.

    2013-01-01

    Duchenne Muscular Dystrophy (DMD), the most common inherited muscular dystrophy of childhood, leads to death due to cardiorespiratory failure. Paradoxically, mdx mice with the same genetic deficiency of dystrophin, exhibit minimal cardiac dysfunction, impeding the development of therapies. We postulated that the difference between mdx and DMD might result from differences in telomere lengths in mice and humans. We show here that, like DMD patients, mice that lack dystrophin and have shortened telomeres (mdx/mTRKO) develop severe functional cardiac deficits including ventricular dilation, contractile and conductance dysfunction, and accelerated mortality. These cardiac defects are accompanied by telomere erosion, mitochondrial fragmentation, and increased oxidative stress. Treatment with anti-oxidants significantly retards the onset of cardiac dysfunction and death of mdx/mTRKO mice. In corroboration, of four DMD patients analyzed, all had 45% shorter telomeres in their cardiomyocytes relative to age- and sex-matched controls. We propose that the demands of contraction in the absence of dystrophin coupled with increased oxidative stress conspire to accelerate telomere erosion culminating in cardiac failure and death. These findings provide strong support for a link between telomere length and dystrophin deficiency in the etiology of dilated cardiomyopathy in DMD and suggest preventive interventions. PMID:23831727

  11. Progressive Telomere Dysfunction Causes Cytokinesis Failure and Leads to the Accumulation of Polyploid Cells

    PubMed Central

    Pampalona, Judit; Frías, Cristina; Genescà, Anna; Tusell, Laura

    2012-01-01

    Most cancer cells accumulate genomic abnormalities at a remarkably rapid rate, as they are unable to maintain their chromosome structure and number. Excessively short telomeres, a known source of chromosome instability, are observed in early human-cancer lesions. Besides telomere dysfunction, it has been suggested that a transient phase of polyploidization, in most cases tetraploidization, has a causative role in cancer. Proliferation of tetraploids can gradually generate subtetraploid lineages of unstable cells that might fire the carcinogenic process by promoting further aneuploidy and genomic instability. Given the significance of telomere dysfunction and tetraploidy in the early stages of carcinogenesis, we investigated whether there is a connection between these two important promoters of chromosomal instability. We report that human mammary epithelial cells exhibiting progressive telomere dysfunction, in a pRb deficient and wild-type p53 background, fail to complete the cytoplasmatic cell division due to the persistence of chromatin bridges in the midzone. Flow cytometry together with fluorescence in situ hybridization demonstrated an accumulation of binucleated polyploid cells upon serial passaging cells. Restoration of telomere function through hTERT transduction, which lessens the formation of anaphase bridges by recapping the chromosome ends, rescued the polyploid phenotype. Live-cell imaging revealed that these polyploid cells emerged after abortive cytokinesis due to the persistence of anaphase bridges with large intervening chromatin in the cleavage plane. In agreement with a primary role of anaphase bridge intermediates in the polyploidization process, treatment of HMEC-hTERT cells with bleomycin, which produces chromatin bridges through illegimitate repair, resulted in tetraploid binucleated cells. Taken together, we demonstrate that human epithelial cells exhibiting physiological telomere dysfunction engender tetraploid cells through interference of

  12. Telomere Dysfunction Triggers Palindrome Formation Independently of Double-Strand Break Repair Mechanisms

    PubMed Central

    Raykov, Vasil; Marvin, Marcus E.; Louis, Edward J.; Maringele, Laura

    2016-01-01

    Inverted chromosome duplications or palindromes are linked with genetic disorders and malignant transformation. They are considered by-products of DNA double-strand break (DSB) repair: the homologous recombination (HR) and the nonhomologous end joining (NHEJ). Palindromes near chromosome ends are often triggered by telomere losses. An important question is to what extent their formation depends upon DSB repair mechanisms. Here we addressed this question using yeast genetics and comparative genomic hybridization. We induced palindrome formation by passaging cells lacking any form of telomere maintenance (telomerase and telomere recombination). Surprisingly, we found that DNA ligase 4, essential for NHEJ, did not make a significant contribution to palindrome formation induced by telomere losses. Moreover RAD51, important for certain HR-derived mechanisms, had little effect. Furthermore RAD52, which is essential for HR in yeast, appeared to decrease the number of palindromes in cells proliferating without telomeres. This study also uncovered an important role for Rev3 and Rev7 (but not for Pol32) subunits of polymerase ζ in the survival of cells undergoing telomere losses and forming palindromes. We propose a model called short-inverted repeat-induced synthesis in which DNA synthesis, rather than DSB repair, drives the inverted duplication triggered by telomere dysfunction. PMID:27334270

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

    PubMed

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

    2016-01-01

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

  14. Telomere Dysfunction Triggers Palindrome Formation Independently of Double-Strand Break Repair Mechanisms.

    PubMed

    Raykov, Vasil; Marvin, Marcus E; Louis, Edward J; Maringele, Laura

    2016-08-01

    Inverted chromosome duplications or palindromes are linked with genetic disorders and malignant transformation. They are considered by-products of DNA double-strand break (DSB) repair: the homologous recombination (HR) and the nonhomologous end joining (NHEJ). Palindromes near chromosome ends are often triggered by telomere losses. An important question is to what extent their formation depends upon DSB repair mechanisms. Here we addressed this question using yeast genetics and comparative genomic hybridization. We induced palindrome formation by passaging cells lacking any form of telomere maintenance (telomerase and telomere recombination). Surprisingly, we found that DNA ligase 4, essential for NHEJ, did not make a significant contribution to palindrome formation induced by telomere losses. Moreover RAD51, important for certain HR-derived mechanisms, had little effect. Furthermore RAD52, which is essential for HR in yeast, appeared to decrease the number of palindromes in cells proliferating without telomeres. This study also uncovered an important role for Rev3 and Rev7 (but not for Pol32) subunits of polymerase ζ in the survival of cells undergoing telomere losses and forming palindromes. We propose a model called short-inverted repeat-induced synthesis in which DNA synthesis, rather than DSB repair, drives the inverted duplication triggered by telomere dysfunction. PMID:27334270

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

    PubMed Central

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

    2016-01-01

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

  16. Telomeres in cancer and ageing

    PubMed Central

    Donate, Luis E.; Blasco, Maria A.

    2011-01-01

    Telomeres protect the chromosome ends from unscheduled DNA repair and degradation. Telomeres are heterochromatic domains composed of repetitive DNA (TTAGGG repeats) bound to an array of specialized proteins. The length of telomere repeats and the integrity of telomere-binding proteins are both important for telomere protection. Furthermore, telomere length and integrity are regulated by a number of epigenetic modifications, thus pointing to higher order control of telomere function. In this regard, we have recently discovered that telomeres are transcribed generating long, non-coding RNAs, which remain associated with the telomeric chromatin and are likely to have important roles in telomere regulation. In the past, we showed that telomere length and the catalytic component of telomerase, Tert, are critical determinants for the mobilization of stem cells. These effects of telomerase and telomere length on stem cell behaviour anticipate the premature ageing and cancer phenotypes of telomerase mutant mice. Recently, we have demonstrated the anti-ageing activity of telomerase by forcing telomerase expression in mice with augmented cancer resistance. Shelterin is the major protein complex bound to mammalian telomeres; however, its potential relevance for cancer and ageing remained unaddressed to date. To this end, we have generated mice conditionally deleted for the shelterin proteins TRF1, TPP1 and Rap1. The study of these mice demonstrates that telomere dysfunction, even if telomeres are of a normal length, is sufficient to produce premature tissue degeneration, acquisition of chromosomal aberrations and initiation of neoplastic lesions. These new mouse models, together with the telomerase-deficient mouse model, are valuable tools for understanding human pathologies produced by telomere dysfunction. PMID:21115533

  17. The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase over-expression

    PubMed Central

    de Jonge, Nick; Björkholm, Magnus; Xu, Dawei

    2015-01-01

    DNA methyltransferase inhibitors (DNMTIs) such as 5-azacytidine (5-AZA) have been used for treatment of acute myeloid leukemia (AML) and other malignancies. Although inhibiting global/gene-specific DNA methylation is widely accepted as a key mechanism behind DNMTI anti-tumor activity, other mechanisms are likely involved in DNMTI's action. Because telomerase reverse transcriptase (TERT) plays key roles in cancer through telomere elongation and telomere lengthening-independent activities, and TERT has been shown to confer chemo- or radio-resistance to cancer cells, we determine whether DNMTIs affect telomere function and whether TERT/telomerase interferes with their anti-cancer efficacy. We showed that 5-AZA induced DNA damage and telomere dysfunction in AML cell lines by demonstrating the presence of 53-BP1 foci and the co-localization of 53-BP1 foci with telomere signals, respectively. Telomere dysfunction was coupled with diminished TERT expression, shorter telomere and apoptosis in 5-AZA-treated cells. However, 5-AZA treatment did not lead to changes in the methylation status of subtelomere regions. Down-regulation of TERT expression similarly occurred in primary leukemic cells derived from AML patients exposed to 5-AZA. TERT over-expression significantly attenuated 5-AZA-mediated DNA damage, telomere dysfunction and apoptosis of AML cells. Collectively, 5-AZA mediates the down-regulation of TERT expression, and induces telomere dysfunction, which consequently exerts an anti-tumor activity. PMID:25682873

  18. The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase over-expression.

    PubMed

    Zhang, Xiaolu; Li, Bingnan; de Jonge, Nick; Björkholm, Magnus; Xu, Dawei

    2015-03-10

    DNA methyltransferase inhibitors (DNMTIs) such as 5-azacytidine (5-AZA) have been used for treatment of acute myeloid leukemia (AML) and other malignancies. Although inhibiting global/gene-specific DNA methylation is widely accepted as a key mechanism behind DNMTI anti-tumor activity, other mechanisms are likely involved in DNMTI's action. Because telomerase reverse transcriptase (TERT) plays key roles in cancer through telomere elongation and telomere lengthening-independent activities, and TERT has been shown to confer chemo- or radio-resistance to cancer cells, we determine whether DNMTIs affect telomere function and whether TERT/telomerase interferes with their anti-cancer efficacy. We showed that 5-AZA induced DNA damage and telomere dysfunction in AML cell lines by demonstrating the presence of 53-BP1 foci and the co-localization of 53-BP1 foci with telomere signals, respectively. Telomere dysfunction was coupled with diminished TERT expression, shorter telomere and apoptosis in 5-AZA-treated cells. However, 5-AZA treatment did not lead to changes in the methylation status of subtelomere regions. Down-regulation of TERT expression similarly occurred in primary leukemic cells derived from AML patients exposed to 5-AZA. TERT over-expression significantly attenuated 5-AZA-mediated DNA damage, telomere dysfunction and apoptosis of AML cells. Collectively, 5-AZA mediates the down-regulation of TERT expression, and induces telomere dysfunction, which consequently exerts an anti-tumor activity. PMID:25682873

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

    SciTech Connect

    Qiang, Weiguang; Wu, Qinqin; Zhou, Fuxiang; Xie, Conghua; Wu, Changping; Zhou, Yunfeng

    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.

  20. In Vitro Properties of the Conserved Mammalian Protein hnRNP D Suggest a Role in Telomere Maintenance

    PubMed Central

    Eversole, Ashley; Maizels, Nancy

    2000-01-01

    Mammalian chromosomes terminate with a 3′ tail which consists of reiterations of the G-rich repeat, d(TTAGGG). The telomeric tail is the primer for replication by telomerase, and it may also invade telomeric duplex DNA to form terminal lariat structures, or T loops. Here we show that the ubiquitous and highly conserved mammalian protein hnRNP D interacts specifically with the G-rich strand of the telomeric repeat. A single gene encodes multiple isoforms of hnRNP D. All isoforms bind comparably to the G-rich strand, and certain isoforms can also bind tightly and specifically to the C-rich telomeric strand. G-rich telomeric sequences readily form structures stabilized by G-G pairing, which can interfere with telomere replication by telomerase. We show that hnRNP D binding to the G-rich strand destabilizes intrastrand G-G pairing and that hnRNP D interacts specifically with telomerase in human cell extracts. This biochemical analysis suggest that hnRNP D could function in vivo to destabilize structures formed by telomeric G-rich tails and facilitate their extension by telomerase. PMID:10891483

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

    SciTech Connect

    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.

  2. The level of telomere dysfunction determines the efficacy of telomerase-based therapeutics in a lung cancer cell line.

    PubMed

    Pantic, Milena; Zimmermann, Stefan; Waller, Cornelius F; Martens, Uwe M

    2005-05-01

    Telomerase is the ribonucleoprotein enzyme that maintains telomeres of eukaryotic chromosomes. Activation of telomerase is a common feature of the majority of human cancers, and inhibition of this enzyme has been proposed as a novel target for cancer therapeutics. Here, we investigated the effects of telomerase inhibition in the non-small cell lung cancer cell line NCI-H460, using a genetic approach by ectopic expression of dominant-negative (DN)-hTERT. Five clones were selected in which telomerase activity was completely abolished. As a result, telomere erosion was observed leading to proliferation arrest after a lag period of 20-28 population doublings. Although overall telomere length was similar between the different clones as measured by quantitative fluorescence in situ hybridization (Q-FISH), striking differences were found in telomere length of individual chromosomes. In particular, lack of individual telomeres and formation of end-to-end fusions were variable. Interestingly, this level of individual telomere dysfunction was positively correlated with the remaining life span of the different clones in vitro. In addition, the amount of telomere dysfunction induced by DN-hTERT was twice as high compared to the small molecule telomerase inhibitor BIBR1532, which induced growth arrest after >100 population doublings. Thus, pharmacological strategies that aim at inhibition of telomerase in cancer cells should take into account that not only overall telomere shortening, but rapid induction of a high level telomere dysfunction appears to be the crucial surrogate parameter for the development of future telomerase-based therapeutics. PMID:15809713

  3. Arsenic trioxide inhibits glioma cell growth through induction of telomerase displacement and telomere dysfunction

    PubMed Central

    Cheng, Ye; Li, Yunqian; Ma, Chengyuan; Song, Yang; Xu, Haiyang; Yu, Hongquan; Xu, Songbai; Mu, Qingchun; Li, Haisong; Chen, Yong; Zhao, Gang

    2016-01-01

    Glioblastomas are resistant to many kinds of treatment, including chemotherapy, radiation and other adjuvant therapies. As2O3 reportedly induces ROS generation in cells, suggesting it may be able to induce telomerase suppression and telomere dysfunction in glioblastoma cells. We show here that As2O3 induces ROS generation as well as telomerase phosphorylation in U87, U251, SHG4 and C6 glioma cells. It also induces translocation of telomerase from the nucleus to the cytoplasm, thereby decreasing total telomerase activity. These effects of As2O3 trigger an extensive DNA damage response at the telomere, which includes up-regulation of ATM, ATR, 53BP1, γ-H2AX and Mer11, in parallel with telomere fusion and 3′-overhang degradation. This ultimately results in induction of p53- and p21-mediated cell apoptosis, G2/M cell cycle arrest and cellular senescence. These results provide new insight into the antitumor effects of As2O3 and can perhaps contribute to solving the problem of glioblastoma treatment resistance. PMID:26871293

  4. Specific telomere dysfunction induced by GRN163L increases radiation sensitivity in breast cancer cells

    SciTech Connect

    Gomez-Millan, Jaime; Goldblatt, Erin M.; Gryaznov, Sergei M.; Mendonca, Marc S.; Herbert, Brittney-Shea . E-mail: brherber@iupui.edu

    2007-03-01

    Purpose: Telomerase is expressed in 80-90% of tumor cells, but is absent in most somatic cells. The absence of telomerase activity results in progressive telomere shortening, leading to cellular senescence or death through deoxyribonucleic acid (DNA) damage signals. In addition, a role for telomerase in DNA damage repair has also been suggested. A specific telomerase inhibitor, GRN163L that is complementary to the template region of the telomerase ribonucleic acid component (hTR). We hypothesized that exposure to GRN163L, either through immediate inhibition of telomerase activity or through eventual telomere shortening and dysfunction, may enhance radiation sensitivity. Our goal was to test whether the treatment with GRN163L enhances sensitivity to irradiation (IR) in MDA-MB-231 breast cancer cells. Methods and Materials: The MDA-MB-231 breast cancer cells were treated with or without GRN163L for 2-42 days. Inhibition of telomerase activity and shortening of telomeres were confirmed. Cells were then irradiated and clonogenic assays were performed to show cell survival differences. In vivo studies using MDA-MB-231 xenografts were performed to corroborate the in vitro results. Results: We show that cells with shortened telomeres due to GRN163L enhance the effect on IR reducing survival by an additional 30% (p < 0.01). These results are confirmed in vivo, with a significant decrease in tumor growth in mice exposed to GRN163L. Conclusions: We found that GRN163L is a promising adjuvant treatment in combination with radiation therapy that may improve the therapeutic index by enhancing the radiation sensitivity. These studies prompt further investigation as to whether this combination can be applied to other cancers and the clinic.

  5. Isolation of chromatin from dysfunctional telomeres reveals an important role for Ring1b in NHEJ-mediated chromosome fusions.

    PubMed

    Bartocci, Cristina; Diedrich, Jolene K; Ouzounov, Iliana; Li, Julia; Piunti, Andrea; Pasini, Diego; Yates, John R; Lazzerini Denchi, Eros

    2014-05-22

    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. PMID:24813883

  6. A novel telomerase substrate precursor rapidly induces telomere dysfunction in telomerase positive cancer cells but not telomerase silent normal cells

    PubMed Central

    Mender, Ilgen; Gryaznov, Sergei; Shay, Jerry W.

    2015-01-01

    Although telomerase is an almost universal target for cancer therapy, there has been no effective telomerase targeted inhibitor that has progressed to late stage human clinical trials. Recently, we reported that a telomerase-mediated telomere-disrupting compound, 6-thio-2′-deoxyguanosine (6-thio-dG), was very effective at targeting telomerase positive cancer cells while sparing telomerase silent normal cells. 6-thio-dG, a nucleoside analogue of the already-approved drug 6-thioguanine, is incorporated into telomeres by telomerase, resulting in disruption of the telomere-protecting shelterin complex. This disruption leads to Telomere dysfunction-Induced Foci (TIFs) formation and rapid cell death for the vast majority of cancer cells. Since most chemotherapies eventually fail due to drug acquired resistance, novel drugs such as 6-thio-dG, as a single first line agent or in the maintenance setting, may represent an effective new treatment for cancer patients. PMID:26425659

  7. The G-quadruplex-stabilising agent RHPS4 induces telomeric dysfunction and enhances radiosensitivity in glioblastoma cells.

    PubMed

    Berardinelli, F; Siteni, S; Tanzarella, C; Stevens, M F; Sgura, A; Antoccia, A

    2015-01-01

    G-quadruplex (G4) interacting agents are a class of ligands that can bind to and stabilise secondary structures located in genomic G-rich regions such as telomeres. Stabilisation of G4 leads to telomere architecture disruption with a consequent detrimental effect on cell proliferation, which makes these agents good candidates for chemotherapeutic purposes. RHPS4 is one of the most effective and well-studied G4 ligands with a very high specificity for telomeric G4. In this work, we tested the in vitro efficacy of RHPS4 in astrocytoma cell lines, and we evaluated whether RHPS4 can act as a radiosensitising agent by destabilising telomeres. In the first part of the study, the response to RHPS4 was investigated in four human astrocytoma cell lines (U251MG, U87MG, T67 and T70) and in two normal primary fibroblast strains (AG01522 and MRC5). Cell growth reduction, histone H2AX phosphorylation and telomere-induced dysfunctional foci (TIF) formation were markedly higher in astrocytoma cells than in normal fibroblasts, despite the absence of telomere shortening. In the second part of the study, the combined effect of submicromolar concentrations of RHPS4 and X-rays was assessed in the U251MG glioblastoma radioresistant cell line. Long-term growth curves, cell cycle analysis and cell survival experiments, clearly showed the synergistic effect of the combined treatment. Interestingly the effect was greater in cells bearing a higher number of dysfunctional telomeres. DNA double-strand breaks rejoining after irradiation revealed delayed repair kinetics in cells pre-treated with the drug and a synergistic increase in chromosome-type exchanges and telomeric fusions. These findings provide the first evidence that exposure to RHPS4 radiosensitizes astrocytoma cells, suggesting the potential for future therapeutic applications. PMID:25467559

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

    SciTech Connect

    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.

  9. Dysfunctional telomeres induce p53-dependent and independent apoptosis to compromise cellular proliferation and inhibit tumor formation.

    PubMed

    Wang, Yang; Wang, Xinwei; Flores, Elsa R; Yu, Jian; Chang, Sandy

    2016-08-01

    Aging is associated with progressive telomere shortening, resulting in the formation of dysfunctional telomeres that compromise tissue proliferation. However, dysfunctional telomeres can limit tumorigenesis by activating p53-dependent cellular senescence and apoptosis. While activation of both senescence and apoptosis is required for repress tumor formation, it is not clear which pathway is the major tumor suppressive pathway in vivo. In this study, we generated Eμ-myc; Pot1b(∆/∆) mouse to directly compare tumor formation under conditions in which either p53-dependent apoptosis or senescence is activated by telomeres devoid of the shelterin component Pot1b. We found that activation of p53-dependent apoptosis plays a more critical role in suppressing lymphoma formation than p53-dependent senescence. In addition, we found that telomeres in Pot1b(∆/∆) ; p53(-/-) mice activate an ATR-Chk1-dependent DNA damage response to initiate a robust p53-independent, p73-dependent apoptotic pathway that limited stem cell proliferation but suppressed B-cell lymphomagenesis. Our results demonstrate that in mouse models, both p53-dependent and p53-independent apoptosis are important to suppressing tumor formation. PMID:27113195

  10. G-quadruplex ligand-induced DNA damage response coupled with telomere dysfunction and replication stress in glioma stem cells.

    PubMed

    Hasegawa, Daiki; Okabe, Sachiko; Okamoto, Keiji; Nakano, Ichiro; Shin-ya, Kazuo; Seimiya, Hiroyuki

    2016-02-26

    Glioblastoma (GBM) is an invariably fatal brain tumor in which a small subpopulation of self-renewable glioma stem cells (GSCs) contributes to tumor propagation and relapse. Targeting GSCs could therefore have a significant clinical impact for GBM. Telomestatin is a naturally-occurring compound that preferentially impairs GSC growth by perturbing transcription and inducing a DNA damage response. Telomestatin stabilizes G-quadruplexes (G4s), which are guanine-rich four-strand nucleic acid structures observed in vitro and in vivo. However, the mechanism underlying the GSC-selective nature of the DNA damage response remains unknown. Here we demonstrate that GSCs are more susceptible to telomestatin-induced telomere dysfunction and replication stress when compared with GSC-derived non-stem glioma cells (NSGCs). Telomestatin induced dissociation of the telomere-capping protein TRF2 from telomeres, leading to telomeric DNA damage in GSCs-but not in NSGCs. BIBR1532, a telomerase catalytic inhibitor, did not preferentially inhibit GSC growth, suggesting that telomestatin promotes telomere dysfunction in a telomerase-independent manner. GSCs and NSGCs had comparable levels of G4s in their nuclei, and both responded to telomestatin with phosphorylation of RPA2 at Ser33-a hallmark of replication stress. However, activation of the checkpoint kinase Chk1, induction of a DNA damage response, and subsequent growth inhibition occurred only in telomestatin-treated GSCs. These observations suggest that telomestatin impairs GSC growth through removal of TRF2 from telomeres and potent activation of the replication stress response pathway. Therefore, a novel G4-directed therapeutic strategy could specifically target cancer stem cells in GBM. PMID:26845351

  11. Opposing impacts on healthspan and longevity by limiting dietary selenium in Telomere Dysfunctional mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium (Se) is an essential trace element essential for optimal health. We investigated the role of Se in longevity and healthspan in a mouse model of healthy aging in humans with short telomeres. Telomere shortening is associated with aging, mortality and aging-related diseases. We found that whi...

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

    PubMed

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

    2016-06-01

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

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

    PubMed Central

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

    2016-01-01

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

  14. HnRNP A3 binds to and protects mammalian telomeric repeats in vitro

    SciTech Connect

    Tanaka, Etsuko; Fukuda, Hirokazu; Nakashima, Katsuhiko; Tsuchiya, Naoto; Seimiya, Hiroyuki; Nakagama, Hitoshi . E-mail: hnakagam@gan2.res.ncc.go.jp

    2007-06-29

    The biological function of hnRNP family proteins is widely diverse and involved in pre-mRNA processing, transcriptional regulation, recombination, and telomere maintenance. In the course of our study on the elucidation of biological functions of minisatellite DNA, we isolated several nuclear proteins that bind to the mouse minisatellite Pc-1, which consists of a tandem array of d(GGCAG) repeats, from NIH3T3 cells. One of the minisatellite binding proteins, MNBP-A, which binds to a single-stranded G-rich strand of the Pc-1 repeat, was proven identical to the hnRNP A3. Recombinant hnRNP A3 was demonstrated to bind to the single-stranded telomeric d(TTAGGG) repeat with much higher affinity than the d(GGCAG) repeat. Binding of hnRNP A3 to the single-stranded telomeric repeat protected the repeat from nuclease attack, and inhibited both telomerase reaction and DNA synthesis in vitro. These results suggest a possible biological role of hnRNP A3 in the stable maintenance of telomere repeats.

  15. Telomere dysfunction promotes metastasis in a Terc null mouse model of head and neck cancer

    PubMed Central

    Bojovic, Bojana; Crowe, David L.

    2011-01-01

    Squamous cell carcinoma arises from highly proliferative basal layer epithelial cells which normally divide for a short time before detaching from the basement membrane and undergoing terminal differentiation. Basal layer cells in stratified epithelia express the reverse transcriptase known as telomerase. Most human cells do not express telomerase and therefore are subject to loss of telomeric DNA with age due to the inability of lagging strand synthesis to completely replicate chromosomal ends. Late generation telomerase deficient mice exhibit signs of premature aging including reduced function of proliferating cellular compartments. We examined development of squamous cell carcinoma in a telomerase deficient murine background with long and short telomeres. G1 Terc−/− mice (long telomeres) had fewer lymph node metastases which correlated with increased numbers of apoptotic cells in these tumors compared to wild type mice. However, G5 Terc−/− mice with short telomeres had increased metastatic tumor burden similar to wild type mice. This increased metastasis correlated with genomic instability and aneuploidy in tumor cells from G5 Terc−/− mice. A number of similarities with human SCC were noted in the mouse model, and dramatic differences in global gene expression profiles were demonstrated between primary and metastatic tumors. We concluded that telomere shortening promotes metastatic tumor development in a Terc null mouse model of head and neck cancer. PMID:21593138

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

    SciTech Connect

    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.

  17. Telomeres and reproductive aging.

    PubMed

    Keefe, David L; Liu, Lin

    2009-01-01

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

  18. Stn1 is critical for telomere maintenance and long-term viability of somatic human cells

    PubMed Central

    Boccardi, Virginia; Razdan, Neetu; Kaplunov, Jessica; Mundra, Jyoti J; Kimura, Masayuki; Aviv, Abraham; Herbig, Utz

    2015-01-01

    Disruption of telomere maintenance pathways leads to accelerated entry into cellular senescence, a stable proliferative arrest that promotes aging-associated disorders in some mammals. The budding yeast CST complex, comprising Cdc13, Stn1, and Ctc1, is critical for telomere replication, length regulation, and end protection. Although mammalian homologues of CST have been identified recently, their role and function for telomere maintenance in normal somatic human cells are still incompletely understood. Here, we characterize the function of human Stn1 in cultured human fibroblasts and demonstrate its critical role in telomere replication, length regulation, and function. In the absence of high telomerase activity, shRNA-mediated knockdown of hStn1 resulted in aberrant and fragile telomeric structures, stochastic telomere attrition, increased telomere erosion rates, telomere dysfunction, and consequently accelerated entry into cellular senescence. Oxidative stress augmented the defects caused by Stn1 knockdown leading to almost immediate cessation of cell proliferation. In contrast, overexpression of hTERT suppressed some of the defects caused by hStn1 knockdown suggesting that telomerase can partially compensate for hStn1 loss. Our findings reveal a critical role for human Stn1 in telomere length maintenance and function, supporting the model that efficient replication of telomeric repeats is critical for long-term viability of normal somatic mammalian cells. PMID:25684230

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

    SciTech Connect

    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{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.

  20. Apollo contributes to G-overhang maintenance and protects leading-end telomeres

    PubMed Central

    Wu, Peng; van Overbeek, Megan; Rooney, Sean; de Lange, Titia

    2010-01-01

    SUMMARY Mammalian telomeres contain a single-stranded 3′ overhang that is thought to mediate telomere protection. Here we identify the TRF2-interacting factor Apollo as a nuclease that contributes to the generation/maintenance of this overhang. The function of mouse Apollo was determined using Cre-mediated gene deletion, complementation with Apollo mutants, and the TRF2-F120A mutant that cannot bind Apollo. Cells lacking Apollo activated the ATM kinase at their telomeres in S phase and showed leading-end telomere fusions. These telomere dysfunction phenotypes were accompanied by a reduction in the telomeric overhang signal. The telomeric functions of Apollo required its TRF2-interaction and nuclease motifs. Thus, TRF2 recruits the Apollo nuclease to process telomere ends synthesized by leading-strand DNA synthesis, thereby creating a terminal structure that avoids ATM activation and resists end-joining. These data establish that the telomeric overhang is required for the protection of telomeres from the DNA damage response. PMID:20619712

  1. SNMIB/Apollo protects leading-strand telomeres against NHEJ-mediated repair.

    PubMed

    Lam, Yung C; Akhter, Shamima; Gu, Peili; Ye, Jing; Poulet, Anaïs; Giraud-Panis, Marie-Josèphe; Bailey, Susan M; Gilson, Eric; Legerski, Randy J; Chang, Sandy

    2010-07-01

    Progressive telomere attrition or deficiency of the protective shelterin complex elicits a DNA damage response as a result of a cell's inability to distinguish dysfunctional telomeric ends from DNA double-strand breaks. SNMIB/Apollo is a shelterin-associated protein and a member of the SMN1/PSO2 nuclease family that localizes to telomeres through its interaction with TRF2. Here, we generated SNMIB/Apollo knockout mouse embryo fibroblasts (MEFs) to probe the function of SNMIB/Apollo at mammalian telomeres. SNMIB/Apollo null MEFs exhibit an increased incidence of G2 chromatid-type fusions involving telomeres created by leading-strand DNA synthesis, reflective of a failure to protect these telomeres after DNA replication. Mutations within SNMIB/Apollo's conserved nuclease domain failed to suppress this phenotype, suggesting that its nuclease activity is required to protect leading-strand telomeres. SNMIB/Apollo(-/-)ATM(-/-) MEFs display robust telomere fusions when Trf2 is depleted, indicating that ATM is dispensable for repair of uncapped telomeres in this setting. Our data implicate the 5'-3' exonuclease function of SNM1B/Apollo in the generation of 3' single-stranded overhangs at newly replicated leading-strand telomeres to protect them from engaging the non-homologous end-joining pathway. PMID:20551906

  2. Chromatin Structure in Telomere Dynamics

    PubMed Central

    Galati, Alessandra; Micheli, Emanuela; Cacchione, Stefano

    2013-01-01

    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 deprotected state and their role in telomere functions. PMID:23471416

  3. The E3 ubiquitin ligase RNF8 stabilizes TPP1 to promote telomere end protection

    PubMed Central

    Rai, Rekha; Li, Ju-Mei; Zheng, Hong; Lok, Gabriel Tsz-Mei; Deng, Yu; Huen, Michael; Chen, Junjie; Jin, Jianping; Chang, Sandy

    2013-01-01

    TPP1, a component of the mammalian shelterin complex, plays essential roles in telomere maintenance. It forms a heterodimer with POT1 to repress ATR-dependent DNA damage signaling at telomeres, and recruits telomerase to chromosome ends. Here we show that the E3 ubiquitin ligase RNF8 localizes to and promotes the accumulation of DNA damage proteins 53BP1 and γ-H2AX to uncapped telomeres. TPP1 is unstable in the absence of RNF8, resulting in telomere shortening and chromosome fusions via the alternative non-homologous end joining (A-NHEJ)-mediated DNA repair pathway. The RNF8 ubiquitin ligase RING domain is essential for TPP1 stability and retention at telomeres. RNF8 physically interacts with TPP1 to generate Ubc13-dependent K63 polyubiquitin chains that stabilizes TPP1 at telomeres. The conserved TPP1 lysine residue 233 is essential for RNF8-mediated TPP1 ubiquitylation and localization to telomeres. Our results demonstrate that TPP1 is a novel substrate for RNF8, and suggest a previously unrecognized role for RNF8 in telomere end protection. We propose a model in which engagement of classical vs. A-NHEJ repair pathways at dysfunctional telomeres is controlled by the ubiquitin ligase functions of RNF8. PMID:22101936

  4. Transcription regulates telomere dynamics in human cancer cells

    PubMed Central

    Arora, Rajika; Brun, Catherine M.; Azzalin, Claus M.

    2012-01-01

    Telomeres are nucleoprotein structures capping the physical ends of linear eukaryotic chromosomes. Although largely heterochromatic, telomeres are transcribed into telomeric repeat-containing RNA (TERRA) molecules by RNA polymerase II. The functions associated with telomere transcription and TERRA remain ill defined. Here we show that the transcriptional activity of human telomeres directly regulates their movement during interphase. We find that chemical inhibition of global transcription dampens telomere motion, while global stimulation promotes it. Likewise, when DNA methyltransferase enzymes are deleted to augment telomere transcription, we observe increased telomere movement. Finally, using a cell line engineered with a unique transcriptionally inducible telomere, we show that transcription of one specific telomere stimulates only its own dynamics without overtly affecting its stability or its length. We reveal a new and unforeseen function for telomere transcription as a regulator of telomere motion, and speculate on the intriguing possibility that transcription-dependent telomere motion sustains the maintenance of functional and dysfunctional telomeres. PMID:22357912

  5. Mitochondrial Dysfunction Is the Focus of Quaternary Ammonium Surfactant Toxicity to Mammalian Epithelial Cells

    PubMed Central

    Inácio, Ângela S.; Costa, Gabriel N.; Domingues, Neuza S.; Santos, Maria S.; Moreno, António J. M.; Vaz, Winchil L. C.

    2013-01-01

    Surfactants have long been known to have microbicidal action and have been extensively used as antiseptics and disinfectants for a variety of general hygiene and clinical purposes. Among surfactants, quaternary ammonium compounds (QAC) are known to be the most useful antiseptics and disinfectants. However, our previous toxicological studies showed that QAC are also the most toxic surfactants for mammalian cells. An understanding of the mechanisms that underlie QAC toxicity is a crucial first step in their rational use and in the design and development of more effective and safer molecules. We show that QAC-induced toxicity is mediated primarily through mitochondrial dysfunction in mammalian columnar epithelial cell cultures in vitro. Toxic effects begin at sublethal concentrations and are characterized by mitochondrial fragmentation accompanied by decreased cellular energy charge. At very low concentrations, several QAC act on mitochondrial bioenergetics through a common mechanism of action, primarily by inhibiting mitochondrial respiration initiated at complex I and, to a lesser extent, by slowing down coupled ADP phosphorylation. The result is a reduction of cellular energy charge which, when reduced below 50% of its original value, induces apoptosis. The lethal effects are shown to be primarily a result of this process. At higher doses (closer to the critical micellar concentration), QAC induce the complete breakdown of cellular energy charge and necrotic cell death. PMID:23529737

  6. Telomere-Binding Protein TPP1 Modulates Telomere Homeostasis and Confers Radioresistance to Human Colorectal Cancer Cells

    PubMed Central

    Hu, Liu; Yang, Xiaoxi; Zhong, Juan; Li, Zheng; Yang, Hui; Lei, Han; Yu, Haijun; Liao, ZhengKai; Zhou, Fuxiang; Xie, Conghua; Zhou, Yunfeng

    2013-01-01

    Background Radiotherapy is one of the major therapeutic strategies in cancer treatment. The telomere-binding protein TPP1 is an important component of the shelterin complex at mammalian telomeres. Our previous reports showed that TPP1 expression was elevated in radioresistant cells, but the exact effects and mechanisms of TPP1 on radiosensitivity is unclear. Principal Findings In this study, we found that elevated TPP1 expression significantly correlated with radioresistance and longer telomere length in human colorectal cancer cell lines. Moreover, TPP1 overexpression showed lengthened telomere length and a significant decrease of radiosensitivity to X-rays. TPP1 mediated radioresistance was correlated with a decreased apoptosis rate after IR exposure. Furthermore, TPP1 overexpression showed prolonged G2/M arrest mediated by ATM/ATR-Chk1 signal pathway after IR exposure. Moreover, TPP1 overexpression accelerated the repair kinetics of total DNA damage and telomere dysfunction induced by ionizing radiation. Conclusions We demonstrated that elevated expressions of TPP1 in human colorectal cancer cells could protect telomere from DNA damage and confer radioresistance. These results suggested that TPP1 may be a potential target in the radiotherapy of colorectal cancer. PMID:24260532

  7. Rapid induction of Alternative Lengthening of Telomeres by depletion of the histone chaperone ASF1

    PubMed Central

    O’Sullivan, Roderick J.; Arnoult, Nausica; Lackner, Daniel H.; Oganesian, Liana; Haggblom, Candy; Corpet, Armelle; Almouzni, Genevieve; Karlseder, Jan

    2013-01-01

    The mechanism of activation of the Alternative Lengthening of Telomeres (ALT) pathway of mammalian chromosome end maintenance has remained an unresolved issue. We have discovered that co-depletion of the histone chaperones ASF1a and ASF1b in human cells induced all hallmarks of ALT in both primary and cancer cells. These included the formation of ALT associated PML bodies (APBs), extra-chromosomal telomeric DNA species an elevated frequency of telomeric sister chromatid exchanges (t-SCE) events and inter-telomeric exchange of an integrated tag. The induction of ALT characteristics in this setting led to the simultaneous suppression of telomerase. We identified that ALT induction is positively regulated by RAD17 and BLM, while negatively regulated by EXO1 and DNA2. The induction of ALT phenotypes as a consequence of ASF1 depletion strongly support the hypothesis that ALT is a consequence of a histone management dysfunction. PMID:24413054

  8. Telomere Restriction Fragment (TRF) Analysis

    PubMed Central

    Mender, Ilgen; Shay, Jerry W.

    2016-01-01

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

  9. Stop pulling my strings - what telomeres taught us about the DNA damage response.

    PubMed

    Lazzerini-Denchi, Eros; Sfeir, Agnel

    2016-06-01

    Mammalian cells have evolved specialized mechanisms to sense and repair double-strand breaks (DSBs) to maintain genomic stability. However, in certain cases, the activity of these pathways can lead to aberrant DNA repair, genomic instability and tumorigenesis. One such case is DNA repair at the natural ends of linear chromosomes, known as telomeres, which can lead to chromosome-end fusions. Here, we review data obtained over the past decade and discuss the mechanisms that protect mammalian chromosome ends from the DNA damage response. We also discuss how telomere research has helped to uncover key steps in DSB repair. Last, we summarize how dysfunctional telomeres and the ensuing genomic instability drive the progression of cancer. PMID:27165790

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

    PubMed Central

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

    2015-01-01

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

  11. Mammalian Polymerase Theta Promotes Alternative-NHEJ and Suppresses Recombination

    PubMed Central

    Mateos-Gomez, Pedro A.; Gong, Fade; Nair, Nidhi; Miller, Kyle M.; Lazzerini-Denchi, Eros; Sfeir, Agnel

    2016-01-01

    The alternative nonhomologous end-joining (alt-NHEJ) machinery facilitates a number of genomic rearrangements, some of which can lead to cellular transformation. This error-prone repair pathway is triggered upon telomere de-protection to promote the formation of deleterious chromosome end-to-end fusions1,2,3. Using next-generation sequencing technology, we found that repair by alt-NHEJ yields non-TTAGGG nucleotide insertions at fusion breakpoints of dysfunctional telomeres. Investigating the enzymatic activity responsible for the random insertions enabled us to identify Polymerase theta (Polθ; encoded by PolQ) as a critical alt-NHEJ factor in mammalian cells. PolQ inhibition suppresses alt-NHEJ at dysfunctional telomeres, and hinders chromosomal translocations at non-telomeric loci. In addition, we found that PolQ loss results in increased rates of homology directed repair (HDR), evident by recombination of dysfunctional telomeres and accumulation of Rad51 at double stranded breaks. Lastly, we show that depletion of PolQ has a synergistic impact on cell survival in the absence of BRCA genes, suggesting that the inhibition of this mutagenic polymerase represents a valid therapeutic avenue for tumors carrying mutations in HDR genes. PMID:25642960

  12. Fanconi anemia proteins in telomere maintenance.

    PubMed

    Sarkar, Jaya; Liu, Yie

    2016-07-01

    Mammalian chromosome ends are protected by nucleoprotein structures called telomeres. Telomeres ensure genome stability by preventing chromosome termini from being recognized as DNA damage. Telomere length homeostasis is inevitable for telomere maintenance because critical shortening or over-lengthening of telomeres may lead to DNA damage response or delay in DNA replication, and hence genome instability. Due to their repetitive DNA sequence, unique architecture, bound shelterin proteins, and high propensity to form alternate/secondary DNA structures, telomeres are like common fragile sites and pose an inherent challenge to the progression of DNA replication, repair, and recombination apparatus. It is conceivable that longer the telomeres are, greater is the severity of such challenges. Recent studies have linked excessively long telomeres with increased tumorigenesis. Here we discuss telomere abnormalities in a rare recessive chromosomal instability disorder called Fanconi Anemia and the role of the Fanconi Anemia pathway in telomere biology. Reports suggest that Fanconi Anemia proteins play a role in maintaining long telomeres, including processing telomeric joint molecule intermediates. We speculate that ablation of the Fanconi Anemia pathway would lead to inadequate aberrant structural barrier resolution at excessively long telomeres, thereby causing replicative burden on the cell. PMID:27118469

  13. Telomere attrition and diabetes mellitus.

    PubMed

    Tamura, Yoshiaki; Takubo, Kaiyo; Aida, Junko; Araki, Atsushi; Ito, Hideki

    2016-03-01

    Type 2 diabetes mellitus (DM) is a disease characterized by dysfunction of various organs. Recent studies have shown a close relationship between DM and telomere attrition in leukocytes. In patients with DM or impaired glucose tolerance, excessive oxidative stress induces damage to telomeres and shortens their length. Furthermore, it is suggested that telomere length is a good surrogate marker for mortality and diabetic complications in DM patients. We recently found that telomere length in pancreatic β-cells is also shortened in DM patients, potentially leading to an impaired capacity for proliferation and insulin secretion, and accelerated cell death. In contrast, leukocyte telomere length has also been reported in patients with obesity or insulin resistance, both of which are frequently associated with type 2 DM. In an animal model, it has been shown that telomere attrition in adipose tissue induces insulin resistance. Taken together, the available data suggest that hyperglycemia, oxidative stress, and telomere attrition in pancreatic β-cells and adipocytes create a vicious cycle that underlies the pathophysiology of type 2 DM. Inhibition of telomere attrition in various organs, including pancreatic β-cells, could be a new approach for preventing the progression of DM and its complications. PMID:27018285

  14. Hypothesis: Paralog Formation from Progenitor Proteins and Paralog Mutagenesis Spur the Rapid Evolution of Telomere Binding Proteins.

    PubMed

    Lustig, Arthur J

    2016-01-01

    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. PMID:26904098

  15. Hypothesis: Paralog Formation from Progenitor Proteins and Paralog Mutagenesis Spur the Rapid Evolution of Telomere Binding Proteins

    PubMed Central

    Lustig, Arthur J.

    2016-01-01

    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. PMID:26904098

  16. Identification of Neuroblastoma Subgroups Based on Three-Dimensional Telomere Organization.

    PubMed

    Kuzyk, Alexandra; Gartner, John; Mai, Sabine

    2016-08-01

    Using 3D telomere quantitative fluorescence in situ hybridization, we determined the 3D telomere organization of 74 neuroblastoma tissue samples. Hierarchical cluster analysis of the measured telomere parameters identified three subgroups from our patient cohort. These subgroups have unique telomere profiles based on telomere length and nuclear architecture. Subgroups with higher levels of telomere dysfunction were comprised of tumors with greater numbers of telomeres, telomeric aggregates, and short telomeres (P<.0001). Tumors with greater telomere dysfunction were associated with unfavorable tumor characteristics (greater age at diagnosis, unfavorable histology, higher stage of disease, MYCN amplification, and higher MYCN expression) and poor prognostic risk (P<.001). Subgroups with greater telomere dysfunction also had higher intratumor heterogeneity. MYCN overexpression in two neuroblastoma cell lines with constitutively low MYCN expression induced changes in their telomere profile that were consistent with increased telomere dysfunction; this illustrates a functional relationship between MYCN and 3D telomere organization. This study demonstrates the ability to classify neuroblastomas based on the level of telomere dysfunction, which is a novel approach for this cancer. PMID:27567959

  17. Targeted DNA damage at individual telomeres disrupts their integrity and triggers cell death

    PubMed Central

    Sun, Luxi; Tan, Rong; Xu, Jianquan; LaFace, Justin; Gao, Ying; Xiao, Yanchun; Attar, Myriam; Neumann, Carola; Li, Guo-Min; Su, Bing; Liu, Yang; Nakajima, Satoshi; Levine, Arthur S.; Lan, Li

    2015-01-01

    Cellular DNA is organized into chromosomes and capped by a unique nucleoprotein structure, the telomere. Both oxidative stress and telomere shortening/dysfunction cause aging-related degenerative pathologies and increase cancer risk. However, a direct connection between oxidative damage to telomeric DNA, comprising <1% of the genome, and telomere dysfunction has not been established. By fusing the KillerRed chromophore with the telomere repeat binding factor 1, TRF1, we developed a novel approach to generate localized damage to telomere DNA and to monitor the real time damage response at the single telomere level. We found that DNA damage at long telomeres in U2OS cells is not repaired efficiently compared to DNA damage in non-telomeric regions of the same length in heterochromatin. Telomeric DNA damage shortens the average length of telomeres and leads to cell senescence in HeLa cells and cell death in HeLa, U2OS and IMR90 cells, when DNA damage at non-telomeric regions is undetectable. Telomere-specific damage induces chromosomal aberrations, including chromatid telomere loss and telomere associations, distinct from the damage induced by ionizing irradiation. Taken together, our results demonstrate that oxidative damage induces telomere dysfunction and underline the importance of maintaining telomere integrity upon oxidative damage. PMID:26082495

  18. HSV-1 Remodels Host Telomeres To Facilitate Viral Replication

    PubMed Central

    Deng, Zhong; Kim, Eui Tae; Vladimirova, Olga; Dheekollu, Jayaraju; Wang, Zhuo; Newhart, Alyshia; Liu, Dongmei; Myers, Jaclyn L.; Hensley, Scott E.; Moffat, Jennifer; Janicki, Susan M.; Fraser, Nigel W.; Knipe, David M.; Weitzman, Matthew D.; Lieberman, Paul M.

    2015-01-01

    Summary Telomeres protect the ends of cellular chromosomes. We show here that infection with herpes simplex virus 1 (HSV-1) results in chromosomal structural aberrations at telomeres and the accumulation of telomere dysfunction-induced DNA damage foci (TIFs). At the molecular level, HSV-1 induces transcription of telomere repeat-containing RNA (TERRA), followed by the proteolytic degradation of the telomere protein TPP1, and loss of the telomere repeat DNA signal. The HSV-1 encoded E3 ubiquitin ligase ICP0 is required for TERRA transcription and facilitates TPP1 degradation. shRNA depletion of TPP1 increases viral replication, arguing that TPP1inhibits viral replication. Viral replication protein ICP8 forms foci that coincide with telomeric proteins and ICP8 null virus failed to degrade telomere DNA signal. These findings suggest that HSV-1 reorganizes telomeres to form ICP8-associated pre-replication foci and promotes viral genomic replication. PMID:25497088

  19. Telomerase Activity and Telomere Length in Daphnia

    PubMed Central

    Schumpert, Charles; Nelson, Jacob; Kim, Eunsuk; Dudycha, Jeffry L.; Patel, Rekha C.

    2015-01-01

    Telomeres, comprised of short repetitive sequences, are essential for genome stability and have been studied in relation to cellular senescence and aging. Telomerase, the enzyme that adds telomeric repeats to chromosome ends, is essential for maintaining the overall telomere length. A lack of telomerase activity in mammalian somatic cells results in progressive shortening of telomeres with each cellular replication event. Mammals exhibit high rates of cell proliferation during embryonic and juvenile stages but very little somatic cell proliferation occurs during adult and senescent stages. The telomere hypothesis of cellular aging states that telomeres serve as an internal mitotic clock and telomere length erosion leads to cellular senescence and eventual cell death. In this report, we have examined telomerase activity, processivity, and telomere length in Daphnia, an organism that grows continuously throughout its life. Similar to insects, Daphnia telomeric repeat sequence was determined to be TTAGG and telomerase products with five-nucleotide periodicity were generated in the telomerase activity assay. We investigated telomerase function and telomere lengths in two closely related ecotypes of Daphnia with divergent lifespans, short-lived D. pulex and long-lived D. pulicaria. Our results indicate that there is no age-dependent decline in telomere length, telomerase activity, or processivity in short-lived D. pulex. On the contrary, a significant age dependent decline in telomere length, telomerase activity and processivity is observed during life span in long-lived D. pulicaria. While providing the first report on characterization of Daphnia telomeres and telomerase activity, our results also indicate that mechanisms other than telomere shortening may be responsible for the strikingly short life span of D. pulex. PMID:25962144

  20. Telomerase activity and telomere length in Daphnia.

    PubMed

    Schumpert, Charles; Nelson, Jacob; Kim, Eunsuk; Dudycha, Jeffry L; Patel, Rekha C

    2015-01-01

    Telomeres, comprised of short repetitive sequences, are essential for genome stability and have been studied in relation to cellular senescence and aging. Telomerase, the enzyme that adds telomeric repeats to chromosome ends, is essential for maintaining the overall telomere length. A lack of telomerase activity in mammalian somatic cells results in progressive shortening of telomeres with each cellular replication event. Mammals exhibit high rates of cell proliferation during embryonic and juvenile stages but very little somatic cell proliferation occurs during adult and senescent stages. The telomere hypothesis of cellular aging states that telomeres serve as an internal mitotic clock and telomere length erosion leads to cellular senescence and eventual cell death. In this report, we have examined telomerase activity, processivity, and telomere length in Daphnia, an organism that grows continuously throughout its life. Similar to insects, Daphnia telomeric repeat sequence was determined to be TTAGG and telomerase products with five-nucleotide periodicity were generated in the telomerase activity assay. We investigated telomerase function and telomere lengths in two closely related ecotypes of Daphnia with divergent lifespans, short-lived D. pulex and long-lived D. pulicaria. Our results indicate that there is no age-dependent decline in telomere length, telomerase activity, or processivity in short-lived D. pulex. On the contrary, a significant age dependent decline in telomere length, telomerase activity and processivity is observed during life span in long-lived D. pulicaria. While providing the first report on characterization of Daphnia telomeres and telomerase activity, our results also indicate that mechanisms other than telomere shortening may be responsible for the strikingly short life span of D. pulex. PMID:25962144

  1. Arsenic exposure, telomere length, and expression of telomere-related genes among Bangladeshi individuals

    PubMed Central

    Gao, Jianjun; Roy, Shantanu; Tong, Lin; Argos, Maria; Jasmine, Farzana; Rahaman, Ronald; Rakibuz-Zaman, Muhammad; Parvez, Faruque; Ahmed, Alauddin; Hore, Samar K; Sarwar, Golam; Slavkovich, Vesna; Yunus, Mohammad; Rahman, Mahfuzar; Baron, John A.; Graziano, Joseph H.; Ahsan, Habibul; Pierce, Brandon L.

    2014-01-01

    Background Inorganic arsenic is a carcinogen whose mode of action may involve telomere dysfunction. Recent epidemiological studies suggest that chronic arsenic exposure is associated with longer telomeres and altered expression of telomere-related genes in peripheral blood. In this study, we evaluated the association of urinary arsenic concentration with expression of telomere-related genes and telomere length in Bangladeshi individuals with a wide range of arsenic exposure through naturally contaminated drinking water. Methods We used linear regression models to estimate associations between urinary arsenic and array-based expression measures for 69 telomere related genes using mononuclear cell RNA samples from 1,799 individuals. Association between arsenic exposure and a qPCR-based telomere length was assessed among 167 individuals. Results Urinary arsenic was possitively associated with expression of WRN, and negatively associated with TERF2, DKC1, TERF2IP and OBFC1 (all P < 0.00035, Bonferroni correction threshold). We detected interaction between urinary arsenic and arsenic metabolism efficiency in relation to expression of WRN (P for interaction = 0.00008). In addition, we observed that very high arsenic exposure was associated with longer telomeres compared to very low exposure (P=0.02). Discussion Our findings suggest that arsenic’s carcinogenic mode of action may involve alteration of telomere maintenance and/or telomere damage. This study extends our knowledge regarding the effect of arsenic on telomere length and expression of telomere-related genes. PMID:25460668

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

    PubMed Central

    Tzeng, Tsai-Yu; Lin, I-Hsuan; Hsu, Ming-Ta

    2016-01-01

    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. PMID:27228173

  3. Alternative end joining, clonal evolution, and escape from a telomere-driven crisis

    PubMed Central

    Hendrickson, Eric A; Baird, Duncan M

    2015-01-01

    Telomere dysfunction and fusion play key roles in driving genomic instability and clonal evolution in many tumor types. We have recently described a role for DNA ligase III (LIG3) in facilitating the escape of cells from crisis induced by telomere dysfunction. Our data indicate that LIG3-mediated telomere fusion is important in facilitating clonal evolution. PMID:27308409

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

    PubMed

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

    2016-05-10

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

  5. Unconventional secretion of misfolded proteins promotes adaptation to proteasome dysfunction in mammalian cells.

    PubMed

    Lee, Jin-Gu; Takahama, Shokichi; Zhang, Guofeng; Tomarev, Stanislav I; Ye, Yihong

    2016-07-01

    To safeguard proteomic integrity, cells rely on the proteasome to degrade aberrant polypeptides, but it is unclear how cells remove defective proteins that have escaped degradation owing to proteasome insufficiency or dysfunction. Here we report a pathway termed misfolding-associated protein secretion, which uses the endoplasmic reticulum (ER)-associated deubiquitylase USP19 to preferentially export aberrant cytosolic proteins. Intriguingly, the catalytic domain of USP19 possesses an unprecedented chaperone activity, allowing recruitment of misfolded proteins to the ER surface for deubiquitylation. Deubiquitylated cargos are encapsulated into ER-associated late endosomes and secreted to the cell exterior. USP19-deficient cells cannot efficiently secrete unwanted proteins, and grow more slowly than wild-type cells following exposure to a proteasome inhibitor. Together, our findings delineate a protein quality control (PQC) pathway that, unlike degradation-based PQC mechanisms, promotes protein homeostasis by exporting misfolded proteins through an unconventional protein secretion process. PMID:27295555

  6. Role of mitochondrial dysfunction and dysregulation of Ca(2+) homeostasis in insulin insensitivity of mammalian cells.

    PubMed

    Wang, Chih-Hao; Tsai, Ting-Fen; Wei, Yau-Huei

    2015-09-01

    Mitochondria and endoplasmic reticulum (ER) play an important role in the maintenance of intracellular Ca(2+) homeostasis, and their defects may be etiological factors contributing to insulin resistance and type 2 diabetes (T2D). Recent studies indicate that alterations of Ca(2+) levels and Ca(2+) -dependent signaling pathways can impede the insulin signaling cascade, resulting in insulin resistance of β cells and insulin-responsive cells. Mitochondria-associated ER membranes (MAMs) are essential for efficient communication between the ER and mitochondria. Thus, abnormalities in the structure and function of MAMs in affected tissue cells in T2D are an important area of study. Recently, we demonstrated that a deficiency of Cisd2, an iron-sulfur protein localized on MAMs, could lead to mitochondrial dysfunction and disturbance of intracellular Ca(2+) homeostasis. Moreover, we first elucidated that defects in the function of MAMs in Ca(2+) uptake resulted in insulin insensitivity of adipocytes, which plays an important role in the pathogenesis of diabetes in Cisd2 knockout mice. On the basis of these observations, we suggest improving the bioenergetic function of mitochondria and the function of MAMs in maintaining Ca(2+) homeostasis as a novel strategy for the development of new therapeutics aimed at preventing and treating insulin resistance and T2D. PMID:26214798

  7. Spontaneous tumor development in bone marrow-rescued DNA-PKcs(3A/3A) mice due to dysfunction of telomere leading strand deprotection.

    PubMed

    Zhang, S; Matsunaga, S; Lin, Y-F; Sishc, B; Shang, Z; Sui, J; Shih, H-Y; Zhao, Y; Foreman, O; Story, M D; Chen, D J; Chen, B P C

    2016-07-28

    Phosphorylation of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) at the Thr2609 cluster is essential for its complete function in DNA repair and tissue stem cell homeostasis. This phenomenon is demonstrated by congenital bone marrow failure occurring in DNA-PKcs(3A/3A) mutant mice, which require bone marrow transplantation (BMT) to prevent early mortality. Surprisingly, an increased incidence of spontaneous tumors, especially skin cancer, was observed in adult BMT-rescued DNA-PKcs(3A/3A) mice. Upon further investigation, we found that spontaneous γH2AX foci occurred in DNA-PKcs(3A/3A) skin biopsies and primary keratinocytes and that these foci overlapped with telomeres during mitosis, indicating impairment of telomere replication and maturation. Consistently, we observed significantly elevated frequencies of telomere fusion events in DNA-PKcs(3A/3A) cells as compared with wild-type and DNA-PKcs-knockout cells. In addition, a previously identified DNA-PKcs Thr2609Pro mutation, found in breast cancer, also induces a similar impairment of telomere leading-end maturation. Taken together, our current analyses indicate that the functional DNA-PKcs T2609 cluster is required to facilitate telomere leading strand maturation and prevention of genomic instability and cancer development. PMID:26616856

  8. Widespread telomere instability in prostatic lesions.

    PubMed

    Tu, LiRen; Huda, Nazmul; Grimes, Brenda R; Slee, Roger B; Bates, Alison M; Cheng, Liang; Gilley, David

    2016-05-01

    A critical function of the telomere is to disguise chromosome ends from cellular recognition as double strand breaks, thereby preventing aberrant chromosome fusion events. Such chromosome end-to-end fusions are known to initiate genomic instability via breakage-fusion-bridge cycles. Telomere dysfunction and other forms of genomic assault likely result in misregulation of genes involved in growth control, cell death, and senescence pathways, lowering the threshold to malignancy and likely drive disease progression. Shortened telomeres and anaphase bridges have been reported in a wide variety of early precursor and malignant cancer lesions including those of the prostate. These findings are being extended using methods for the analysis of telomere fusions (decisive genetic markers for telomere dysfunction) specifically within human tissue DNA. Here we report that benign prostatic hyperplasia (BPH), high-grade prostatic intraepithelial neoplasia (PIN), and prostate cancer (PCa) prostate lesions all contain similarly high frequencies of telomere fusions and anaphase bridges. Tumor-adjacent, histologically normal prostate tissue generally did not contain telomere fusions or anaphase bridges as compared to matched PCa tissues. However, we found relatively high levels of telomerase activity in this histologically normal tumor-adjacent tissue that was reduced but closely correlated with telomerase levels in corresponding PCa samples. Thus, we present evidence of high levels of telomere dysfunction in BPH, an established early precursor (PIN) and prostate cancer lesions but not generally in tumor adjacent normal tissue. Our results suggest that telomere dysfunction may be a common gateway event leading to genomic instability in prostate tumorigenesis. . PMID:25917938

  9. A role for Separase in telomere protection

    PubMed Central

    Cipressa, Francesca; Morciano, Patrizia; Bosso, Giuseppe; Mannini, Linda; Galati, Alessandra; Daniela Raffa, Grazia; Cacchione, Stefano; Musio, Antonio; Cenci, Giovanni

    2016-01-01

    Drosophila telomeres are elongated by transposition of specialized retroelements rather than telomerase activity and are assembled independently of the sequence. Fly telomeres are protected by the terminin complex that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. We show that mutations in the Drosophila Separase encoding gene Sse lead not only to endoreduplication but also telomeric fusions (TFs), suggesting a role for Sse in telomere capping. We demonstrate that Separase binds terminin proteins and HP1, and that it is enriched at telomeres. Furthermore, we show that loss of Sse strongly reduces HP1 levels, and that HP1 overexpression in Sse mutants suppresses TFs, suggesting that TFs are caused by a HP1 diminution. Finally, we find that siRNA-induced depletion of ESPL1, the Sse human orthologue, causes telomere dysfunction and HP1 level reduction in primary fibroblasts, highlighting a conserved role of Separase in telomere protection. PMID:26778495

  10. p53 Prevents Entry into Mitosis with Uncapped Telomeres

    PubMed Central

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

    2016-01-01

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

  11. Gcn5 and SAGA Regulate Shelterin Protein Turnover and Telomere Maintenance

    PubMed Central

    Atanassov, Boyko S.; Evrard, Yvonne A.; Multani, Asha S.; Zhang, Zhijing; Tora, László; Devys, Didier; Chang, Sandy; Dent, Sharon Y.R.

    2009-01-01

    SUMMARY Histone acetyltransferases (HATs) play important roles in gene regulation and DNA repair by influencing the accessibility of chromatin to transcription factors and repair proteins. Here we show that deletion of Gcn5 leads to telomere dysfunction in mouse and human cells. Biochemical studies reveal that depletion of Gcn5 or ubiquitin specific protease 22 (Usp22), which is another bona fide component of the Gcn5-containing SAGA complex, increases ubiquitination and turnover of TRF1, a primary component of the telomeric shelterin complex. Inhibition of the proteasome or over expression of USP22 opposes this effect. The USP22 deubiquitinating module requires association with SAGA complexes for activity, and we find that depletion of Gcn5 compromises this association in mammalian cells. Thus, our results indicate that Gcn5 regulates TRF1 levels through effects on Usp22 activity and SAGA integrity. PMID:19683498

  12. Dysfunction of Chromatin Assembly Factor 1 Induces Shortening of Telomeres and Loss of 45S rDNA in Arabidopsis thaliana[W][OA

    PubMed Central

    Mozgová, Iva; Mokroš, Petr; Fajkus, Jiří

    2010-01-01

    Chromatin Assembly Factor 1 (CAF1) is a three-subunit H3/H4 histone chaperone responsible for replication-dependent nucleosome assembly. It is composed of CAC 1-3 in yeast; p155, p60, and p48 in humans; and FASCIATA1 (FAS1), FAS2, and MULTICOPY SUPPRESSOR OF IRA1 in Arabidopsis thaliana. We report that disruption of CAF1 function by fas mutations in Arabidopsis results in telomere shortening and loss of 45S rDNA, while other repetitive sequences (5S rDNA, centromeric 180-bp repeat, CACTA, and Athila) are unaffected. Substantial telomere shortening occurs immediately after the loss of functional CAF1 and slows down at telomeres shortened to median lengths around 1 to 1.5 kb. The 45S rDNA loss is progressive, leaving 10 to 15% of the original number of repeats in the 5th generation of mutants affecting CAF1, but the level of the 45S rRNA transcripts is not altered in these mutants. Increasing severity of the fas phenotype is accompanied by accumulation of anaphase bridges, reduced viability, and plant sterility. Our results show that appropriate replication-dependent chromatin assembly is specifically required for stable maintenance of telomeres and 45S rDNA. PMID:20699390

  13. Short Telomeres in Key Tissues Initiate Local and Systemic Aging in Zebrafish

    PubMed Central

    Carneiro, Madalena C.; Ferreira, Tânia; Carvalho, Tânia; Ferreira, Miguel Godinho

    2016-01-01

    Telomeres shorten with each cell division and telomere dysfunction is a recognized hallmark of aging. Tissue proliferation is expected to dictate the rate at which telomeres shorten. We set out to test whether proliferative tissues age faster than non-proliferative due to telomere shortening during zebrafish aging. We performed a prospective study linking telomere length to tissue pathology and disease. Contrary to expectations, we show that telomeres shorten to critical lengths only in specific tissues and independently of their proliferation rate. Short telomeres accumulate in the gut but not in other highly proliferative tissues such as the blood and gonads. Notably, the muscle, a low proliferative tissue, accumulates short telomeres and DNA damage at the same rate as the gut. Together, our work shows that telomere shortening and DNA damage in key tissues triggers not only local dysfunction but also anticipates the onset of age-associated diseases in other tissues, including cancer. PMID:26789415

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

    PubMed Central

    Procházková Schrumpfová, Petra; Vychodilová, Ivona; Dvořáčková, Martina; Majerská, Jana; Dokládal, Ladislav; Schořová, Šárka; Fajkus, Jiří

    2014-01-01

    Although telomere-binding proteins constitute an essential part of telomeres, in vivo data indicating the existence of a structure similar to mammalian shelterin complex in plants are limited. Partial characterization of a number of candidate proteins has not identified true components of plant shelterin or elucidated their functional mechanisms. Telomere repeat binding (TRB) proteins from Arabidopsis thaliana bind plant telomeric repeats through a Myb domain of the telobox type in vitro, and have been shown to interact with POT1b (Protection of telomeres 1). Here we demonstrate co-localization of TRB1 protein with telomeres in situ using fluorescence microscopy, as well as in vivo interaction using chromatin immunoprecipitation. Classification of the TRB1 protein as a component of plant telomeres is further confirmed by the observation of shortening of telomeres in knockout mutants of the trb1 gene. Moreover, TRB proteins physically interact with plant telomerase catalytic subunits. These findings integrate TRB proteins into the telomeric interactome of A. thaliana. PMID:24397874

  15. Telomere uncapping at the crossroad between cell cycle arrest and carcinogenesis

    PubMed Central

    Gobbini, Elisa; Trovesi, Camilla; Cassani, Corinne; Longhese, Maria Pia

    2014-01-01

    Telomeres are nucleoprotein complexes that protect the natural ends of chromosomes from fusion and degradation and prevent them eliciting a checkpoint response. This protective function, which is called telomere capping, is largely mediated by telomere-binding proteins that suppress checkpoint activation and DNA repair activities. Telomere dysfunction through progressive shortening or removal of capping proteins leads to a checkpoint-mediated block of cell proliferation, which acts as a cancer-suppressor mechanism. However, genetic alterations that inactivate the checkpoint can lead to further telomere erosion and increased genomic instability that, coupled with the activation of mechanisms to restabilize telomeres, can drive the oncogenic process. PMID:27308311

  16. Nuclear-receptor-mediated telomere insertion leads to genome instability in ALT cancers.

    PubMed

    Marzec, Paulina; Armenise, Claudia; Pérot, Gaëlle; Roumelioti, Fani-Marlen; Basyuk, Eugenia; Gagos, Sarantis; Chibon, Frédéric; Déjardin, Jérôme

    2015-02-26

    The breakage-fusion-bridge cycle is a classical mechanism of telomere-driven genome instability in which dysfunctional telomeres are fused to other chromosomal extremities, creating dicentric chromosomes that eventually break at mitosis. Here, we uncover a distinct pathway of telomere-driven genome instability, specifically occurring in cells that maintain telomeres with the alternative lengthening of telomeres mechanism. We show that, in these cells, telomeric DNA is added to multiple discrete sites throughout the genome, corresponding to regions regulated by NR2C/F transcription factors. These proteins drive local telomere DNA addition by recruiting telomeric chromatin. This mechanism, which we name targeted telomere insertion (TTI), generates potential common fragile sites that destabilize the genome. We propose that TTI driven by NR2C/F proteins contributes to the formation of complex karyotypes in ALT tumors. PMID:25723166

  17. Role of telomeres and telomerase in cancer

    PubMed Central

    Shay, Jerry W.; Wright, Woodring E.

    2012-01-01

    There is mounting evidence for the existence of an important relationship between telomeres and telomerase and cellular aging and cancer. Normal human cells progressively lose telomeres with each cell division until a few short telomeres become uncapped leading to a growth arrest known as replicative aging. In the absence of genomic alterations these cells do not die but remain quiescent producing a different constellation of proteins compared to young quiescent cells. Upon specific genetic and epigenetic alterations, normal human cells bypass replicative senescence and continue to proliferate until many telomere ends become uncapped leading to a phenomenon known as crisis. In crisis cells have critically shortened telomeres but continue to attempt to divide leading to significant cell death (apoptosis) and progressive genomic instability. Rarely, a human cell escapes crisis and these cells almost universally express the ribonucleoprotein, telomerase, and maintain stable but short telomeres. The activation of telomerase may be thought of as a mechanism to slow down the rate genomic instability due to dysfunctional telomeres. While telomerase does not drive the oncogenic process, it is permissive and required for the sustain growth of most advanced cancers. Since telomerase is not expressed in most normal human cells, this has led to the development of targeted telomerase cancer therapeutic approaches that are presently in advanced clinical trials. PMID:22015685

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

    PubMed

    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. PMID:27101289

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

    PubMed Central

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

    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. PMID:27101289

  20. Cohesin SMC1beta protects telomeres in meiocytes.

    PubMed

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

    2009-10-19

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

  1. CGGBP1 phosphorylation constitutes a telomere-protection signal

    PubMed Central

    Singh, Umashankar; Maturi, Varun; Jones, Rhiannon E; Paulsson, Ylva; Baird, Duncan M; Westermark, Bengt

    2014-01-01

    The shelterin proteins are required for telomere integrity. Shelterin dysfunction can lead to initiation of unwarranted DNA damage and repair pathways at chromosomal termini. Interestingly, many shelterin accessory proteins are involved in DNA damage signaling and repair. We demonstrate here that in normal human fibroblasts, telomeric ends are protected by phosphorylation of CGG triplet repeat-binding protein 1 (CGGBP1) at serine 164 (S164). We show that serine 164 is a major phosphorylation site on CGGBP1 with important functions. We provide evidence that one of the kinases that can phosphorylate S164 CGGBP1 is ATR. Overexpression of S164A phospho-deficient CGGBP1 exerted a dominant-negative effect, causing telomeric dysfunction, accelerated telomere shortening, enhanced fusion of telomeres, and crisis. However, overexpression of wild-type or phospho-mimicking S164E CGGBP1 did not cause these effects. This telomere damage was associated with reduced binding of the shelterin protein POT1 to telomeric DNA. Our results suggest that CGGBP1 phosphorylation at S164 is a novel telomere protection signal, which can affect telomere-protective function of the shelterin complex. PMID:24196442

  2. Biology of Telomeres: Importance in Etiology of Esophageal Cancer And As Therapeutic Target

    PubMed Central

    Pal, Jagannath; Gold, Jason S.; Munshi, Nikhil C.; Shammas, Masood A.

    2013-01-01

    Purpose of review The purpose of this review is to highlight the importance of telomeres, the mechanisms implicated in their maintenance, and their role in the etiology as well as the treatment of human esophageal cancer. We will also discuss the role of telomeres in the maintenance/preservation of genomic integrity, the consequences of telomere dysfunction, and the various factors that may affect telomere health in esophageal tissue predisposing it to oncogenesis. Recent findings There has been growing evidence that telomeres, which can be affected by various intrinsic and extrinsic factors, contribute to genomic instability, oncogenesis, as well as proliferation of cancer cells. Summary Telomeres are the protective DNA-protein complexes at chromosome ends. Telomeric DNA undergoes progressive shortening with age leading to cellular senescence and/or apoptosis. If senescence/apoptosis is prevented as a consequence of specific genomic changes, continued proliferation leads to very short (i.e. dysfunctional) telomeres that can potentially cause genomic instability thus increasing the risk for activation of telomere maintenance mechanisms and oncogenesis. Like many other cancers, esophageal cancer cells have short telomeres and elevated telomerase, the enzyme that maintains telomeres in most cancer cells. Homologous recombination, which is implicated in the alternate pathway of telomere elongation, is also elevated in Barrett’s-associated esophageal adenocarcinoma. Evidence from our laboratory indicates that both telomerase and homologous recombination contribute to telomere maintenance, DNA repair, and the ongoing survival of esophageal cancer cells. This indicates that telomere maintenance mechanisms may potentially be targeted to make esophageal cancer cells static. The rate at which telomeres in healthy cells shorten is determined by a number of intrinsic and extrinsic factors, including those associated with lifestyle. Avoidance of factors that may directly or

  3. The Role of Telomeres and Telomerase in Cancer Research

    PubMed Central

    Stewart, Sheila A.

    2010-01-01

    The fourth AACR Special Conference on The Role of Telomeres and Telomerase in Cancer Research was held February 27–March 2, 2010 in Fort Worth, Texas. The meeting was organized to bring together those interested in the basic molecular mechanisms that govern telomere dynamics and stability with those interested in the clinical implications of telomere dysfunction and the use of telomeres and telomerase as therapeutic targets. The meeting was extremely successful as evidenced by the attendance and quality of the presentations. Indeed, several important themes emerged including 1) the intricate connection between the DNA replication and repair machineries in basic telomere replication and stability; 2) the complex interplay between the telomere-specific shelterin components and DNA repair proteins; 3) the non-telomeric functions of TERT in numerous cell types including stem cells; 4) a growing appreciation for the connection that exists between telomere maintenance deficiency states and diverse conditions such as idiopathic pulmonary fibrosis and hematopoietic malignancies; and 5) the successful progression of agents targeting telomerase directly and immunologically to Phase III clinical trials. Evident at the meeting was the vibrant energy that permeates the telomere field and the important biological and medical findings that it continues to yield. PMID:20841475

  4. Quantification of telomere length by FISH and laser scanning cytometry

    NASA Astrophysics Data System (ADS)

    Mahoney, John E.; Sahin, Ergun; Jaskelioff, Mariela; Chin, Lynda; DePinho, Ronald A.; Protopopov, Alexei I.

    2008-02-01

    Telomeres play a critical role in the maintenance of chromosomal stability. Telomere erosion, coupled with loss of DNA damage checkpoint function, results in genomic instability that promotes the development of cancer. The critical role of telomere dynamics in cancer has motivated the development of technologies designed to monitor telomere reserves in a highly quantitative and high-throughput manner in humans and model organisms. To this end, we have adapted and modified two established technologies, telomere-FISH and laser scanning cytometry. Specifically, we have produced a number of enhancements to the iCys LSC (CompuCyte) package including software updates, use of 60X dry objectives, and increased spatial resolution by 0.2 um size of stage steps. In addition, the 633 nm HeNe laser was replaced with a 532 nm green diode laser to better match the viewing options. Utilization of telomere-deficient mouse cells with short dysfunctional telomeres and matched telomerase reconstituted cultures demonstrated significantly higher mean integral specific fluorescence values for mTR transfectants relative to empty vector controls: 4.485M vs. 1.362M (p<0.0001). Histograms of average telomere intensities for individual cells were obtained and demonstrated intercellular heterogeneity in telomere lengths. The validation of the approach derives from a strong correlation between iCys LSC values and Southern blotting. This validated method greatly increases our experimental throughput and objectivity.

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

    PubMed

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

    2016-01-01

    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. PMID:26941064

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

    PubMed Central

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

    2016-01-01

    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 (TRF2B) to repress PARP1 and SLX4 localization to telomeres. Without RAP1 and TRF2B, 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. PMID:26941064

  7. Stress impacts telomere dynamics.

    PubMed

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

    2007-04-22

    Telomeres are DNA-protein complexes at the ends of chromosomes that control genomic integrity but appear to become shorter with age and stress. To test whether stress causes telomere attrition, we exposed the offspring of wild-caught house mice (Mus musculus) to stressful conditions and examined the changes in telomere length over six months. We found that females exposed to males and reproductive stress (either with or without crowding) had significantly shorter telomeres than controls, and males exposed to crowding stress had shorter telomeres than males that were not crowded. Our results indicate that stress alters telomere dynamics, causing attrition and hindering restoration, and these effects are sex dependent. Telomeres may thus provide a biomarker for assessing an individual's cumulative exposure or ability to cope with stressful conditions. PMID:17264051

  8. The potential utility of telomere-related markers for cancer diagnosis

    PubMed Central

    Heaphy, Christopher M; Meeker, Alan K

    2011-01-01

    Abstract The role telomeres and telomerase play in the initiation and progression of human cancers has been extensively evaluated. Telomeres are nucleoprotein complexes comprising the hexanucleotide DNA repeat sequence, TTAGGG and numerous telomere-associated proteins, including the six member Shelterin complex. The main function of the telomere is to stabilize the ends of the chromosomes. However, through multiple mechanisms, telomeres can become dysfunctional, which may drive genomic instability leading to the development of cancer. The majority of human cancers maintain, or actively lengthen, telomeres through up-regulation of the reverse transcriptase telomerase. Because there are significant differences in telomere length and telomerase activity between malignant and non-malignant tissues, many investigations have assessed the potential to utilize these molecular markers for cancer diagnosis. Here, we critically evaluate whether measurements of telomere lengths and telomerase levels may be clinically utilized as diagnostic markers in solid tumours, with emphasis on breast and prostate cancer as representative examples. Future directions focusing on the direct detection of dysfunctional telomeres are explored. New markers for telomere dysfunction may eventually prove clinically useful. PMID:21352473

  9. DNA damage response at telomeres contributes to lung aging and chronic obstructive pulmonary disease

    PubMed Central

    Birch, Jodie; Anderson, Rhys K.; Correia-Melo, Clara; Jurk, Diana; Hewitt, Graeme; Marques, Francisco Madeira; Green, Nicola J.; Moisey, Elizabeth; Birrell, Mark A.; Belvisi, Maria G.; Black, Fiona; Taylor, John J.; Fisher, Andrew J.; De Soyza, Anthony

    2015-01-01

    Cellular senescence has been associated with the structural and functional decline observed during physiological lung aging and in chronic obstructive pulmonary disease (COPD). Airway epithelial cells are the first line of defense in the lungs and are important to COPD pathogenesis. However, the mechanisms underlying airway epithelial cell senescence, and particularly the role of telomere dysfunction in this process, are poorly understood. We aimed to investigate telomere dysfunction in airway epithelial cells from patients with COPD, in the aging murine lung and following cigarette smoke exposure. We evaluated colocalization of γ-histone protein 2A.X and telomeres and telomere length in small airway epithelial cells from patients with COPD, during murine lung aging, and following cigarette smoke exposure in vivo and in vitro. We found that telomere-associated DNA damage foci increase in small airway epithelial cells from patients with COPD, without significant telomere shortening detected. With age, telomere-associated foci increase in small airway epithelial cells of the murine lung, which is accelerated by cigarette smoke exposure. Moreover, telomere-associated foci predict age-dependent emphysema, and late-generation Terc null mice, which harbor dysfunctional telomeres, show early-onset emphysema. We found that cigarette smoke accelerates telomere dysfunction via reactive oxygen species in vitro and may be associated with ataxia telangiectasia mutated-dependent secretion of inflammatory cytokines interleukin-6 and -8. We propose that telomeres are highly sensitive to cigarette smoke-induced damage, and telomere dysfunction may underlie decline of lung function observed during aging and in COPD. PMID:26386121

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

    PubMed Central

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

    2015-01-01

    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. PMID:26640040

  11. DNA-PKcs is critical for telomere capping

    SciTech Connect

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

    2001-04-10

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

  12. Telomeric RNAs are essential to maintain telomeres

    PubMed Central

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

    2016-01-01

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

  13. Telomeric RNAs are essential to maintain telomeres.

    PubMed

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

    2016-01-01

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

  14. Heregulin, a new regulator of telomere length in human cells

    PubMed Central

    Campisi, Judith; Lupu, Ruth

    2015-01-01

    The growth factor heregulin (HRG) promotes breast cancer (BC) tumorigenesis and metastasis and differentially modulates BC cell responses to DNA-damaging agents via its dual extracellular and nuclear localization. Given the central role of telomere dysfunction to drive carcinogenesis and to alter the chemotherapeutic profile of transformed cells, we hypothesized that an unanticipated nuclear function of HRG might be to regulate telomere length. Engineered overexpression of the HRGβ2 isoform in non-aggressive, HRG-negative MCF-7 BC cells resulted in a significant shortening of telomeres (up to 1.3 kb) as measured by Southern blotting of telomere terminal restriction fragments. Conversely, antisense-mediated suppression of HRGβ2 in highly aggressive, HRG-overexpressing MDA-MB-231 and Hs578T cells increased telomere length up to 3.0 kb. HRGβ2 overexpression promoted a marked upregulation of telomere-binding protein 2 (TRF2) protein expression, whereas its knockdown profoundly decreased TRF2 expression. Double staining of endogenous HRGβ2 with telomere-specific peptide nucleic acid probe/fluorescence in situ hybridization (PNA/FISH) revealed the partial localization of HRG at the chromosome ends. Moreover, a predominantly nucleoplasmic staining pattern of endogenous HRGβ2 appeared to co-localize with TRF2 and, concomitantly with RAP1, a telomere regulator that specifically interacts with TRF2. Small interfering RNA-mediated knockdown of HRG decreased the expression of TRF2 and RAP1, decreased their presence at chromosome ends, and coincidentally resulted in the formation of longer telomeres. This study uncovers a new function for HRGβ2 in controlling telomere length, in part due to its ability to regulate and interact with the telomere-associated proteins TRF2 and RAP1. PMID:26318724

  15. Telomeric G-Tail Length and Hospitalization for Cardiovascular Events in Hemodialysis Patients

    PubMed Central

    Hirashio, Shuma; Nakashima, Ayumu; Doi, Shigehiro; Anno, Kumiko; Aoki, Eriko; Shimamoto, Akira; Yorioka, Noriaki; Kohno, Nobuoki; Masaki, Takao

    2014-01-01

    Background and objectives Telomeric G-tails play a pivotal role in maintaining the intramolecular loop structure of telomeres. Previous in vitro studies have suggested that the erosion of telomeric G-tails triggers cellular senescence, leading to organ dysfunction and atherosclerosis. The authors recently established a method to measure telomeric G-tail length using a hybridization protection assay. Using this method, this study investigated whether telomeric G-tail length could be used as a novel predictor for future cardiovascular events in hemodialysis patients. Design, setting, participants, & measurements A prospective observational study was performed involving a cohort of 203 Japanese hemodialysis patients to examine the lengths of telomeric G-tails and total telomeres and subsequent cardiovascular events during a median follow-up period of 48 months. The lengths of telomeric G-tails and total telomeres were also measured in 203 participants who did not have CKD and who were age- and sex-matched to hemodialysis patients. Results The lengths of telomeric G-tails and total telomeres were significantly shorter in hemodialysis patients than in control subjects. Telomeric G-tails, but not total telomeres, were independently and negatively associated with clinical history of cardiovascular disease. During follow-up, 80 cardiovascular events occurred. Total telomere length did not predict cardiovascular events. However, the length of telomeric G-tails was associated with new-onset cardiovascular events (hazard ratio per log luminescence signals, 0.12; 95% confidence interval, 0.12 to 0.50) that persisted after adjustment for age, sex, diabetes mellitus, clinical history of cardiovascular disease, inflammation, use of vitamin D, and serum levels of phosphate and intact parathyroid hormone. Conclusions Longer telomeric G-tail length is associated with a lower risk of future cardiovascular events in hemodialysis patients. PMID:25237070

  16. Telomeres in aging and disease: lessons from zebrafish

    PubMed Central

    Carneiro, Madalena C.; de Castro, Inês Pimenta

    2016-01-01

    ABSTRACT Age is the highest risk factor for some of the most prevalent human diseases, including cancer. Telomere shortening is thought to play a central role in the aging process in humans. The link between telomeres and aging is highlighted by the fact that genetic diseases causing telomerase deficiency are associated with premature aging and increased risk of cancer. For the last two decades, this link has been mostly investigated using mice that have long telomeres. However, zebrafish has recently emerged as a powerful and complementary model system to study telomere biology. Zebrafish possess human-like short telomeres that progressively decline with age, reaching lengths in old age that are observed when telomerase is mutated. The extensive characterization of its well-conserved molecular and cellular physiology makes this vertebrate an excellent model to unravel the underlying relationship between telomere shortening, tissue regeneration, aging and disease. In this Review, we explore the advantages of using zebrafish in telomere research and discuss the primary discoveries made in this model that have contributed to expanding our knowledge of how telomere attrition contributes to cellular senescence, organ dysfunction and disease. PMID:27482813

  17. Possible contributions of a novel form of synaptic plasticity in Aplysia to reward, memory, and their dysfunctions in mammalian brain

    PubMed Central

    Hawkins, Robert D.

    2013-01-01

    Recent studies in Aplysia have identified a new variation of synaptic plasticity in which modulatory transmitters enhance spontaneous release of glutamate, which then acts on postsynaptic receptors to recruit mechanisms of intermediate- and long-term plasticity. In this review I suggest the hypothesis that similar plasticity occurs in mammals, where it may contribute to reward, memory, and their dysfunctions in several psychiatric disorders. In Aplysia, spontaneous release is enhanced by activation of presynaptic serotonin receptors, but presynaptic D1 dopamine receptors or nicotinic acetylcholine receptors could play a similar role in mammals. Those receptors enhance spontaneous release of glutamate in hippocampus, entorhinal cortex, prefrontal cortex, ventral tegmental area, and nucleus accumbens. In all of those brain areas, glutamate can activate postsynaptic receptors to elevate Ca2+ and engage mechanisms of early-phase long-term potentiation (LTP), including AMPA receptor insertion, and of late-phase LTP, including protein synthesis and growth. Thus, presynaptic receptors and spontaneous release may contribute to postsynaptic mechanisms of plasticity in brain regions involved in reward and memory, and could play roles in disorders that affect plasticity in those regions, including addiction, Alzheimer’s disease, schizophrenia, and attention deficit hyperactivity disorder (ADHD). PMID:24049187

  18. Telomere replication: poised but puzzling

    PubMed Central

    Sampathi, Shilpa; Chai, Weihang

    2011-01-01

    Abstract Faithful replication of chromosomes is essential for maintaining genome stability. Telomeres, the chromosomal termini, pose quite a challenge to replication machinery due to the complexity in their structures and sequences. Efficient and complete replication of chromosomes is critical to prevent aberrant telomeres as well as to avoid unnecessary loss of telomere DNA. Compelling evidence supports the emerging picture of synergistic actions between DNA replication proteins and telomere protective components in telomere synthesis. This review discusses the actions of various replication and telomere-specific binding proteins that ensure accurate telomere replication and their roles in telomere maintenance and protection. PMID:21122064

  19. TRF2 Controls Telomeric Nucleosome Organization in a Cell Cycle Phase-Dependent Manner

    PubMed Central

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

    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. PMID:22536324

  20. A TIN2 dyskeratosis congenita mutation causes telomerase-independent telomere shortening in mice.

    PubMed

    Frescas, David; de Lange, Titia

    2014-01-15

    The progressive bone marrow failure syndrome dyskeratosis congenita (DC) is often caused by mutations in telomerase or the factors involved in telomerase biogenesis and trafficking. However, a subset of DC patients is heterozygous for mutations in the shelterin component TIN2. To determine how the TIN2-DC mutations affect telomere function, we generated mice with the equivalent of the TIN2 K280E DC allele (TIN2(DC)) by gene targeting. Whereas homozygous TIN2(DC/DC) mice were not viable, first-generation TIN2(+/DC) mice were healthy and fertile. In the second and third generations, the TIN2(+/DC) mice developed mild pancytopenia, consistent with hematopoietic dysfunction in DC, as well as diminished fecundity. Bone marrow telomeres of TIN2(+/DC) mice shortened over the generations, and immortalized TIN2(+/DC) mouse embryonic fibroblasts (MEFs) showed telomere shortening with proliferation. Unexpectedly, telomere shortening was accelerated in TIN2(+/DC) mTR(-/-) mice and MEFs compared with TIN2(+/+) mTR(-/-) controls, establishing that the TIN2(DC) telomere maintenance defect was not solely due to diminished telomerase action. The TIN2(DC) allele induced mild ATR kinase signaling at telomeres and a fragile telomere phenotype, suggestive of telomere replication problems. These data suggest that this TIN2-DC mutation could induce telomeric dysfunction phenotypes in telomerase-negative somatic cells and tissues that further exacerbate the telomere maintenance problems in telomerase-positive stem cell compartments. PMID:24449270

  1. The Presence of Telomere Fusion in Sporadic Colon Cancer Independently of Disease Stage, TP53/KRAS Mutation Status, Mean Telomere Length, and Telomerase Activity

    PubMed Central

    Tanaka, Hiromi; Beam, Matthew J.; Caruana, Kevin

    2014-01-01

    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. PMID:25379018

  2. Ageing and the telomere connection: An intimate relationship with inflammation.

    PubMed

    Zhang, Jingwen; Rane, Grishma; Dai, Xiaoyun; Shanmugam, Muthu K; Arfuso, Frank; Samy, Ramar Perumal; Lai, Mitchell Kim Peng; Kappei, Dennis; Kumar, Alan Prem; Sethi, Gautam

    2016-01-01

    Telomeres are the heterochromatic repeat regions at the ends of eukaryotic chromosomes, whose length is considered to be a determinant of biological ageing. Normal ageing itself is associated with telomere shortening. Here, critically short telomeres trigger senescence and eventually cell death. This shortening rate may be further increased by inflammation and oxidative stress and thus affect the ageing process. Apart from shortened or dysfunctional telomeres, cells undergoing senescence are also associated with hyperactivity of the transcription factor NF-κB and overexpression of inflammatory cytokines such as TNF-α, IL-6, and IFN-γ in circulating macrophages. Interestingly, telomerase, a reverse transcriptase that elongates telomeres, is involved in modulating NF-κB activity. Furthermore, inflammation and oxidative stress are implicated as pre-disease mechanisms for chronic diseases of ageing such as neurodegenerative diseases, cardiovascular disease, and cancer. To date, inflammation and telomere shortening have mostly been studied individually in terms of ageing and the associated disease phenotype. However, the interdependent nature of the two demands a more synergistic approach in understanding the ageing process itself and for developing new therapeutic approaches. In this review, we aim to summarize the intricate association between the various inflammatory molecules and telomeres that together contribute to the ageing process and related diseases. PMID:26616852

  3. Pathways connecting telomeres and p53 in senescence, apoptosis, and cancer

    SciTech Connect

    Artandi, Steven E. . E-mail: sartandi@stanford.edu; Attardi, Laura D. . E-mail: attardi@stanford.edu

    2005-06-10

    The ends of eukaryotic chromosomes are protected by specialized structures termed telomeres that serve in part to prevent the chromosome end from activating a DNA damage response. However, this important function for telomeres in chromosome end protection can be lost as telomeres shorten with cell division in culture or in self-renewing tissues with advancing age. Impaired telomere function leads to induction of a DNA damage response and activation of the tumor suppressor protein p53. p53 serves a critical role in enforcing both senescence and apoptotic responses to dysfunctional telomeres. Loss of p53 creates a permissive environment in which critically short telomeres are inappropriately joined to generate chromosomal end-to-end fusions. These fused chromosomes result in cycles of chromosome fusion-bridge-breakage, which can fuel cancer initiation, especially in epithelial tissues, by facilitating changes in gene copy number.

  4. BRCA1 and CtIP promote alternative non-homologous end-joining at uncapped telomeres.

    PubMed

    Badie, Sophie; Carlos, Ana Rita; Folio, Cecilia; Okamoto, Keiji; Bouwman, Peter; Jonkers, Jos; Tarsounas, Madalena

    2015-02-01

    Loss of telomere protection occurs during physiological cell senescence and ageing, due to attrition of telomeric repeats and insufficient retention of the telomere-binding factor TRF2. Subsequently formed telomere fusions trigger rampant genomic instability leading to cell death or tumorigenesis. Mechanistically, telomere fusions require either the classical non-homologous end-joining (C-NHEJ) pathway dependent on Ku70/80 and LIG4, or the alternative non-homologous end-joining (A-NHEJ), which relies on PARP1 and LIG3. Here, we show that the tumour suppressor BRCA1, together with its interacting partner CtIP, both acting in end resection, also promotes end-joining of uncapped telomeres. BRCA1 and CtIP do not function in the ATM-dependent telomere damage signalling, nor in telomere overhang removal, which are critical for telomere fusions by C-NHEJ. Instead, BRCA1 and CtIP act in the same pathway as LIG3 to promote joining of de-protected telomeres by A-NHEJ. Our work therefore ascribes novel roles for BRCA1 and CtIP in end-processing and fusion reactions at uncapped telomeres, underlining the complexity of DNA repair pathways that act at chromosome ends lacking protective structures. Moreover, A-NHEJ provides a mechanism of previously unanticipated significance in telomere dysfunction-induced genome instability. PMID:25582120

  5. Formation of extrachromosomal circles from telomeric DNA in Xenopus laevis.

    PubMed

    Cohen, Sarit; Méchali, Marcel

    2002-12-01

    Instability and plasticity of telomeric DNA, which includes extrachromosomal DNA, are usually correlated with the absence of telomerase and with abnormal growth of mammalian cells. Here, we show the formation of extrachromosomal circular DNA of telomeric repeats (tel-eccDNA) during the development of Xenopus laevis. Tel-eccDNA is double-stranded relaxed circles composed of the vertebrate consensus telomeric repeats [TTAGGG](n). Its size varies from <2 to >20 kb and it comprises up to 10% of the total cellular telomere content of the early embryo (pre-MBT stage). The amount of tel-eccDNA is reduced in later developmental stages and in adult tissues. Using a cell-free system derived from Xenopus egg extracts, we show that tel-eccDNA can be formed de novo from the telomere chromosomal tracts of sperm nuclei and naked DNA in a replication-independent manner. These results reveal an unusual plasticity of telomeric DNA during normal development of Xenopus. PMID:12446568

  6. Telomere length and cardiovascular aging.

    PubMed

    Fyhrquist, Frej; Saijonmaa, Outi

    2012-06-01

    Telomeres are located at the end of chromosomes. They are composed of repetitive TTAGGG tandem repeats and associated proteins of crucial importance for telomere function. Telomeric DNA is shortened by each cell division until a critical length is achieved and the cell enters senescence and eventually apoptosis. Telomeres are therefore considered a 'biological clock' of the cell. Telomerase adds nucleotides to telomeric DNA thereby contributing to telomere maintenance, genomic stability, functions, and proliferative capacity of the cell. In certain rare forms of progeria, point mutations within the telomere lead to accelerated telomere attrition and premature aging. Endogenous factors causing telomere shortening are aging, inflammation, and oxidative stress. Leukocyte telomere length (LTL) shortening is inhibited by estrogen and endogenous antioxidants. Accelerated telomere attrition is associated with cardiovascular risk factors such as age, gender, obesity, smoking, sedentary life-style, excess alcohol intake, and even mental stress. Cardiovascular (CV) diseases and CV aging are usually but not invariably associated with shorter telomeres than in healthy subjects. LTL appears to be a biomarker of CV aging, reflecting the cumulative burden of endogenous and exogenous factors negatively affecting LTL. Whether accelerated telomere shortening is cause or consequence of CV aging and disease is not clear. PMID:22713142

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

    PubMed Central

    Watson, J. Matthew; Shippen, Dorothy E.

    2007-01-01

    Telomere length is maintained in species-specific equilibrium primarily through a competition between telomerase-mediated elongation and the loss of terminal DNA through the end-replication problem. Recombinational activities are also capable of both lengthening and shortening telomeres. Here we demonstrate that elongated telomeres in Arabidopsis Ku70 mutants reach a new length set point after three generations. Restoration of wild-type Ku70 in these mutants leads to discrete telomere-shortening events consistent with telomere rapid deletion (TRD). These findings imply that the longer telomere length set point is achieved through competition between overactive telomerase and TRD. Surprisingly, in the absence of telomerase, a subset of elongated telomeres was further lengthened, suggesting that in this background a mechanism of telomerase-independent lengthening of telomeres operates. Unexpectedly, we also found that plants possessing wild-type-length telomeres exhibit TRD when telomerase is inactivated. TRD is stochastic, and all chromosome ends appear to be equally susceptible. The frequency of TRD decreases as telomeres shorten; telomeres less than 2 kb in length are rarely subject to TRD. We conclude that TRD functions as a potent force to regulate telomere length in Arabidopsis. PMID:17189431

  8. Telomeric repeat silencing in germ cells is essential for early development in Drosophila

    PubMed Central

    Morgunova, Valeriya; Akulenko, Natalia; Radion, Elizaveta; Olovnikov, Ivan; Abramov, Yuri; Olenina, Ludmila V.; Shpiz, Sergey; Kopytova, Daria V.; Georgieva, Sofia G.; Kalmykova, Alla

    2015-01-01

    The germline-specific role of telomeres consists of chromosome end elongation and proper chromosome segregation during early developmental stages. Despite the crucial role of telomeres in germ cells, little is known about telomere biology in the germline. We analyzed telomere homeostasis in the Drosophila female germline and early embryos. A novel germline-specific function of deadenylase complex Ccr4-Not in the telomeric transcript surveillance mechanism is reported. Depletion of Ccr4-Not complex components causes strong derepression of the telomeric retroelement HeT-A in the germ cells, accompanied by elongation of the HeT-A poly(A) tail. Dysfunction of transcription factors Woc and Trf2, as well as RNA-binding protein Ars2, also results in the accumulation of excessively polyadenylated HeT-A transcripts in ovaries. Germline knockdowns of Ccr4-Not components, Woc, Trf2 and Ars2, lead to abnormal mitosis in early embryos, characterized by chromosome missegregation, centrosome dysfunction and spindle multipolarity. Moreover, the observed phenotype is accompanied by the accumulation of HeT-A transcripts around the centrosomes in early embryos, suggesting the putative relationship between overexpression of telomeric transcripts and mitotic defects. Our data demonstrate that Ccr4-Not, Woc, Trf2 and Ars2, components of different regulatory pathways, are required for telomere protection in the germline in order to guarantee normal development. PMID:26240377

  9. Telomeres, lifestyle, cancer, and aging

    PubMed Central

    Shammas, Masood A.

    2012-01-01

    Purpose of review There has been growing evidence that lifestyle factors may affect the health and lifespan of an individual by affecting telomere length. The purpose of this review was to highlight the importance of telomeres in human health and aging and to summarize possible lifestyle factors that may affect health and longevity by altering the rate of telomere shortening. Recent findings Recent studies indicate that telomere length, which can be affected by various lifestyle factors, can affect the pace of aging and onset of age-associated diseases. Summary Telomere length shortens with age. Progressive shortening of telomeres leads to senescence, apoptosis, or oncogenic transformation of somatic cells, affecting the health and lifespan of an individual. Shorter telomeres have been associated with increased incidence of diseases and poor survival. The rate of telomere shortening can be either increased or decreased by specific lifestyle factors. Better choice of diet and activities has great potential to reduce the rate of telomere shortening or at least prevent excessive telomere attrition, leading to delayed onset of age-associated diseases and increased lifespan. This review highlights the role of telomeres in aging and describes the lifestyle factors which may affect telomeres, human health, and aging. PMID:21102320

  10. Ticking Telomeres/Telltale Telomerase.

    ERIC Educational Resources Information Center

    Biermann, Carol A.

    1997-01-01

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

  11. Shortened leukocyte telomere length in type 2 diabetes mellitus: genetic polymorphisms in mitochondrial uncoupling proteins and telomeric pathways.

    PubMed

    Zhou, Yuling; Ning, Zhixin; Lee, Yvonne; Hambly, Brett D; McLachlan, Craig S

    2016-03-01

    Current debate in type 2 diabetes (T2DM) has focused on shortened leukocyte telomere length (LTL) as the result of a number of possible causes, including polymorphisms in mitochondrial uncoupling proteins (UCPs) leading to oxidative stress, telomere regulatory pathway gene polymorphisms, or as a direct result of associated cardiovascular complications inducing tissue organ inflammation and oxidative stress. There is evidence that a heritable shorter telomere trait is a risk factor for development of T2DM. This review discusses the contribution and balance of genetic regulation of UCPs and telomere pathways in the context of T2DM. We discuss genotypes that are well known to influence the shortening of LTL, in particular OBFC1 and telomerase genotypes such as TERC. Interestingly, the interaction between short telomeres and T2DM risk appears to involve mitochondrial dysfunction as an intermediate process. A hypothesis is presented that genetic heterogeneity within UCPs may directly affect oxidative stress that feeds back to influence the fine balance of telomere regulation, cell cycle regulation and diabetes risk and/or metabolic disease progression. PMID:26951191

  12. Msh2 deficiency leads to chromosomal abnormalities, centrosome amplification, and telomere capping defect

    SciTech Connect

    Wang, Yisong; Liu, Yie

    2006-01-01

    Msh2 is a key mammalian DNA mismatch repair (MMR) gene and mutations or deficiencies in mammalian Msh2 gene result in microsatellite instability (MSI+) and the development of cancer. Here, we report that primary mouse embryonic fibroblasts (MEFs) deficient in the murine MMR gene Msh2 (Msh2-/-) showed a significant increase in chromosome aneuploidy, centrosome amplification, and defective mitotic spindle organization and unequal chromosome segregation. Although Msh2-/- mouse tissues or primary MEFs had no apparent change in telomerase activity, telomere length, or recombination at telomeres, Msh2-/- MEFs showed an increase in chromosome end-to-end fusions or chromosome ends without detectable telomeric DNA. These data suggest that MSH2 helps to maintain genomic stability through the regulation of the centrosome and normal telomere capping in vivo and that defects in MMR can contribute to oncogenesis through multiple pathways.

  13. Telomere length in blood cells and breast cancer risk: investigations in two case-control studies.

    PubMed

    Zheng, Yun-Ling; Ambrosone, Christine; Byrne, Celia; Davis, Warren; Nesline, Mary; McCann, Susan E

    2010-04-01

    Telomere dysfunction, which leads to genomic instability, is hypothesized to play a causal role in the development of breast cancer. However, the few epidemiologic studies that assessed the relationship between telomere length in blood cells and breast cancer risk have been inconsistent. We conducted two case-control studies to further understand the role of telomere length and breast cancer risk. Overall telomere lengths were measured by telomere quantitative fluorescent in situ hybridization (TQ-FISH) and telomere quantitative real-time PCR (TQ-PCR). The associations between telomere length in blood leukocytes and risk of breast cancer were examined in two breast cancer case-control studies that were conducted at Roswell Park Cancer Institute (RPCI) and Lombardi Comprehensive Cancer Center (LCCC). Using the 50th percentile value in controls as a cut point, women who had shorter telomere length were not at significantly increased risk of breast cancer compared with women who had longer telomere length in the RPCI study (odds ratio [OR] = 1.34, 95% confidence interval [CI] = 0.84-2.12), in the LCCC study (OR = 1.18, 95% CI = 0.73-1.91), or in the combined RPCI and LCCC studies (OR = 1.23, 95% CI = 0.89-1.71). There was no significant dose-response relationship across quartiles of telomere length and no significant difference when comparing women in the lowest to highest quartile of telomere length. Overall telomere length in blood leukocytes was not significantly associated with the risk of breast cancer. PMID:19543829

  14. Telomere and Telomerase Therapeutics in Cancer.

    PubMed

    Xu, Yucheng; Goldkorn, Amir

    2016-01-01

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

  15. Telomere and Telomerase Therapeutics in Cancer

    PubMed Central

    Xu, Yucheng; Goldkorn, Amir

    2016-01-01

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

  16. Donor Telomere Length SAA

    Cancer.gov

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

  17. Tying up loose ends: telomeres, genomic instability and lamins.

    PubMed

    Gonzalo, Susana; Eissenberg, Joel C

    2016-04-01

    On casual inspection, the eukaryotic nucleus is a deceptively simple organelle. Far from being a bag of chromatin, the nucleus is, in some ways, a structural and functional extension of the chromosomes it contains. Recently, interest has intensified in how chromosome compartmentalization and dynamics affect nuclear function. Different studies uncovered functional interactions between chromosomes and the filamentous nuclear meshwork comprised of lamin proteins. Here, we summarize recent research suggesting that telomeres, the capping structures that protect chromosome ends, are stabilized by lamin-binding and that alterations in nuclear lamins lead to defects in telomere compartmentalization, homeostasis and function. Telomere dysfunction contributes to the genomic instability that characterizes aging-related diseases, and might be an important factor in the pathophysiology of lamin-related diseases. PMID:27010504

  18. Replication Timing of Human Telomeres is Conserved during Immortalization and Influenced by Respective Subtelomeres.

    PubMed

    Piqueret-Stephan, Laure; Ricoul, Michelle; Hempel, William M; Sabatier, Laure

    2016-01-01

    Telomeres are specific structures that protect chromosome ends and act as a biological clock, preventing normal cells from replicating indefinitely. Mammalian telomeres are replicated throughout S-phase in a predetermined order. However, the mechanism of this regulation is still unknown. We wished to investigate this phenomenon under physiological conditions in a changing environment, such as the immortalization process to better understand the mechanism for its control. We thus examined the timing of human telomere replication in normal and SV40 immortalized cells, which are cytogenetically very similar to cancer cells. We found that the timing of telomere replication was globally conserved under different conditions during the immortalization process. The timing of telomere replication was conserved despite changes in telomere length due to endogenous telomerase reactivation, in duplicated homologous chromosomes, and in rearranged chromosomes. Importantly, translocated telomeres, possessing their initial subtelomere, retained the replication timing of their homolog, independently of the proportion of the translocated arm, even when the remaining flanking DNA is restricted to its subtelomere, the closest chromosome-specific sequences (inferior to 500 kb). Our observations support the notion that subtelomere regions strongly influence the replication timing of the associated telomere. PMID:27587191

  19. Replication Timing of Human Telomeres is Conserved during Immortalization and Influenced by Respective Subtelomeres

    PubMed Central

    Piqueret-Stephan, Laure; Ricoul, Michelle; Hempel, William M.; Sabatier, Laure

    2016-01-01

    Telomeres are specific structures that protect chromosome ends and act as a biological clock, preventing normal cells from replicating indefinitely. Mammalian telomeres are replicated throughout S-phase in a predetermined order. However, the mechanism of this regulation is still unknown. We wished to investigate this phenomenon under physiological conditions in a changing environment, such as the immortalization process to better understand the mechanism for its control. We thus examined the timing of human telomere replication in normal and SV40 immortalized cells, which are cytogenetically very similar to cancer cells. We found that the timing of telomere replication was globally conserved under different conditions during the immortalization process. The timing of telomere replication was conserved despite changes in telomere length due to endogenous telomerase reactivation, in duplicated homologous chromosomes, and in rearranged chromosomes. Importantly, translocated telomeres, possessing their initial subtelomere, retained the replication timing of their homolog, independently of the proportion of the translocated arm, even when the remaining flanking DNA is restricted to its subtelomere, the closest chromosome-specific sequences (inferior to 500 kb). Our observations support the notion that subtelomere regions strongly influence the replication timing of the associated telomere. PMID:27587191

  20. Telomere length in Hepatitis C.

    PubMed

    Kitay-Cohen, Y; Goldberg-Bittman, L; Hadary, R; Fejgin, M D; Amiel, A

    2008-11-01

    Telomeres are nucleoprotein structures located at the termini of chromosomes that protect the chromosomes from fusion and degradation. Hepatocyte cell-cycle turnover may be a primary mechanism of telomere shortening in hepatitis C virus (HCV) infection, inducing fibrosis and cellular senescence. HCV infection has been recognized as potential cause of B-cell lymphoma and hepatocellular carcinoma. The present study sought to assess relative telomere length in leukocytes from patients with chronic HCV infection, patients after eradication of HCV infection (in remission), and healthy controls. A novel method of manual evaluation was applied. Leukocytes derived from 22 patients with chronic HCV infection and age- and sex-matched patients in remission and healthy control subjects were subjected to a fluorescence-in-situ protocol (DAKO) to determine telomere fluorescence intensity and number. The relative, manual, analysis of telomere length was validated against findings on applied spectral imaging (ASI) in a random sample of study and control subjects. Leukocytes from patients with chronic HCV infection had shorter telomeres than leukocytes from patients in remission and healthy controls. On statistical analysis, more cells with low signal intensity on telomere FISH had shorter telomeres whereas more cells with high signal intensity had longer telomeres. The findings were corroborated by the ASI telomere software. Telomere shortening in leukocytes from patients with active HCV infection is probably due to the lower overall telomere level rather than higher cell cycle turnover. Manual evaluation is an accurate and valid method of assessing relative telomere length between patients with chronic HCV infection and healthy subjects. PMID:18992639

  1. Using Centromere Mediated Genome Elimination to Elucidate the Functional Redundancy of Candidate Telomere Binding Proteins in Arabidopsis thaliana.

    PubMed

    Fulcher, Nick; Riha, Karel

    2015-01-01

    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. PMID:26779251

  2. Using Centromere Mediated Genome Elimination to Elucidate the Functional Redundancy of Candidate Telomere Binding Proteins in Arabidopsis thaliana

    PubMed Central

    Fulcher, Nick; Riha, Karel

    2016-01-01

    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. PMID:26779251

  3. Telomere targeting with a novel G-quadruplex-interactive ligand BRACO-19 induces T-loop disassembly and telomerase displacement in human glioblastoma cells.

    PubMed

    Zhou, Guangtong; Liu, Xinrui; Li, Yunqian; Xu, Songbai; Ma, Chengyuan; Wu, Xinmin; Cheng, Ye; Yu, Zhiyun; Zhao, Gang; Chen, Yong

    2016-03-22

    Interference with telomerase and telomere maintenance is emerging as an attractive target for anticancer therapies. Ligand-induced stabilization of G-quadruplex formation by the telomeric DNA 3'-overhang inhibits telomerase from catalyzing telomeric DNA synthesis and from capping telomeric ends, making these ligands good candidates for chemotherapeutic purposes. BRACO-19 is one of the most effective and specific ligand for telomeric G4. It is shown here that BRACO-19 suppresses proliferation and reduces telomerase activity in human glioblastoma cells, paralleled by the displacement of telomerase from nuclear to cytoplasm. Meanwhile, BRACO-19 triggers extensive DNA damage response at telomere, which may result from uncapping and disassembly of telomeric T-loop structure, characterized by the formation of anaphase bridge and telomere fusion, as well as the release of telomere-binding protein from telomere. The resulting dysfunctional telomere ultimately provokes p53 and p21-mediated cell cycle arrest, apoptosis and senescence. Notably, normal primary astrocytes do not respond to the treatment of BRACO-19, suggesting the agent's good selectivity for cancer cells. These results reinforce the notion that G-quadruplex binding compounds can act as broad inhibitors of telomere-related processes and have potential as selective antineoplastic drugs for various tumors including malignant gliomas. PMID:26908447

  4. Telomere targeting with a novel G-quadruplex-interactive ligand BRACO-19 induces T-loop disassembly and telomerase displacement in human glioblastoma cells

    PubMed Central

    Zhou, Guangtong; Liu, Xinrui; Li, Yunqian; Xu, Songbai; Ma, Chengyuan; Wu, Xinmin; Cheng, Ye; Yu, Zhiyun; Zhao, Gang; Chen, Yong

    2016-01-01

    Interference with telomerase and telomere maintenance is emerging as an attractive target for anticancer therapies. Ligand-induced stabilization of G-quadruplex formation by the telomeric DNA 3′-overhang inhibits telomerase from catalyzing telomeric DNA synthesis and from capping telomeric ends, making these ligands good candidates for chemotherapeutic purposes. BRACO-19 is one of the most effective and specific ligand for telomeric G4. It is shown here that BRACO-19 suppresses proliferation and reduces telomerase activity in human glioblastoma cells, paralleled by the displacement of telomerase from nuclear to cytoplasm. Meanwhile, BRACO-19 triggers extensive DNA damage response at telomere, which may result from uncapping and disassembly of telomeric T-loop structure, characterized by the formation of anaphase bridge and telomere fusion, as well as the release of telomere-binding protein from telomere. The resulting dysfunctional telomere ultimately provokes p53 and p21-mediated cell cycle arrest, apoptosis and senescence. Notably, normal primary astrocytes do not respond to the treatment of BRACO-19, suggesting the agent's good selectivity for cancer cells. These results reinforce the notion that G-quadruplex binding compounds can act as broad inhibitors of telomere-related processes and have potential as selective antineoplastic drugs for various tumors including malignant gliomas. PMID:26908447

  5. Diet-related telomere shortening and chromosome stability

    PubMed Central

    Marcon, Francesca; Siniscalchi, Ester; Crebelli, Riccardo; Saieva, Calogero; Sera, Francesco; Fortini, Paola; Simonelli, Valeria; Palli, Domenico

    2012-01-01

    Recent evidences have highlighted an influence of micronutrients in the maintenance of telomere length (TL). In order to explore whether diet-related telomere shortening had any physiological relevance and was accompanied by significant damage in the genome, in the present study, TL was assessed by terminal restriction fragment (TRF) analysis in peripheral blood lymphocytes of 56 healthy subjects for which detailed information on dietary habits was available and data were compared \\with the incidence of nucleoplasmic bridges (NPBs), a marker of chromosomal instability related to telomere dysfunction visualised with the cytokinesis-blocked micronucleus assay. To increase the capability to detect even slight impairment of telomere function, the incidence of NPBs was also evaluated on cells exposed in vitro to ionising radiation. Care was taken to control for potential confounding factors that might influence TL, viz. age, hTERT genotype and smoking status. Data showed that higher consumption of vegetables was related with significantly higher mean TL (P = 0.013); in particular, the analysis of the association between micronutrients and mean TL highlighted a significant role of antioxidant intake, especially beta-carotene, on telomere maintenance (P = 0.004). However, the diet-related telomere shortening did not result in associated increased spontaneous or radiation-induced NPBs. The distribution of TRFs was also analysed and a slight prevalence of radiation-induced NPBs (P = 0.03) was observed in subjects with higher amount of very short TRFs (<2 kb). The relative incidence of very short TRFs was positively associate with ageing (P = 0.008) but unrelated to vegetables consumption and daily intake of micronutrients, suggesting that the degree of telomere erosion related with low dietary intake of antioxidants observed in this study was not so extensive to lead to chromosome instability. PMID:21857007

  6. Population mixture model for nonlinear telomere dynamics

    NASA Astrophysics Data System (ADS)

    Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl

    2008-12-01

    Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.

  7. Parallel telomere shortening in multiple body tissues owing to malaria infection.

    PubMed

    Asghar, Muhammad; Palinauskas, Vaidas; Zaghdoudi-Allan, Nadège; Valkiūnas, Gediminas; Mukhin, Andrey; Platonova, Elena; Färnert, Anna; Bensch, Staffan; Hasselquist, Dennis

    2016-08-17

    Several studies have shown associations between shorter telomere length in blood and weakened immune function, susceptibility to infections, and increased risk of morbidity and mortality. Recently, we have shown that malaria accelerates telomere attrition in blood cells and shortens lifespan in birds. However, the impact of infections on telomere attrition in different body tissues within an individual is unknown. Here, we tested whether malarial infection leads to parallel telomere shortening in blood and tissue samples from different organs. We experimentally infected siskins (Spinus spinus) with the avian malaria parasite Plasmodium ashfordi, and used real-time quantitative polymerase chain reaction (PCR) to measure telomere length in control and experimentally infected siskins. We found that experimentally infected birds showed faster telomere attrition in blood over the course of infection compared with control individuals (repeatedly measured over 105 days post-infection (DPI)). Shorter telomeres were also found in the tissue of all six major organs investigated (liver, lungs, spleen, heart, kidney, and brain) in infected birds compared with controls at 105 DPI. To the best of our knowledge, this is the first study showing that an infectious disease results in synchronous telomere shortening in the blood and tissue cells of internal organs within individuals, implying that the infection induces systemic stress. Our results have far-reaching implications for understanding how the short-term effects of an infection can translate into long-term costs, such as organ dysfunction, degenerative diseases, and ageing. PMID:27488651

  8. Predictors of telomere content in dragon lizards

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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. PMID:25483196

  10. Telomere function in colorectal cancer.

    PubMed

    Frías, Cristina; Morán, Alberto; de Juan, Carmen; Ortega, Paloma; Fernández-Marcelo, Tamara; Sánchez-Pernaute, Andrés; Torres, Antonio José; Díaz-Rubio, Eduardo; Benito, Manuel; Iniesta, Pilar

    2009-10-15

    Colorectal cancer is the third most common form of cancer and the second leading cause of cancer-related death in the western world. Tumour cells acquire the hallmarks of cancer during the carcinogenic selection process. Cell immortality is one of the principal features acquired during this process which involves the stabilization of telomere length. It is achieved mainly, by telomerase activation. Thus, the discovery of telomeres and telomerase allowed an understanding of the mechanisms by which cells can become immortalized. Different studies have shown that tumour cells have shorter telomeres than nontumour cells and have detected telomerase activity in the majority of tumours. Survival studies have determined that telomere maintenance and telomerase activity are associated with poor prognosis. Taking into account all the results achieved by different groups, quantification and evaluation of telomerase activity and measurement of telomere length may be useful methods for additional biologic and prognostic staging of colorectal carcinoma. PMID:21160767

  11. ALT telomeres get together with nuclear receptors.

    PubMed

    Aeby, Eric; Lingner, Joachim

    2015-02-26

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

  12. A 'telomere-associated secretory phenotype' cooperates with BCR-ABL to drive malignant proliferation of leukemic cells.

    PubMed

    Braig, M; Pällmann, N; Preukschas, M; Steinemann, D; Hofmann, W; Gompf, A; Streichert, T; Braunschweig, T; Copland, M; Rudolph, K L; Bokemeyer, C; Koschmieder, S; Schuppert, A; Balabanov, S; Brümmendorf, T H

    2014-10-01

    Telomere biology is frequently associated with disease evolution in human cancer and dysfunctional telomeres have been demonstrated to contribute to genetic instability. In BCR-ABL(+) chronic myeloid leukemia (CML), accelerated telomere shortening has been shown to correlate with leukemia progression, risk score and response to treatment. Here, we demonstrate that proliferation of murine CML-like bone marrow cells strongly depends on telomere maintenance. CML-like cells of telomerase knockout mice with critically short telomeres (CML-iG4) are growth retarded and proliferation is terminally stalled by a robust senescent cell cycle arrest. In sharp contrast, CML-like cells with pre-shortened, but not critically short telomere lengths (CML-G2) grew most rapidly and were found to express a specific 'telomere-associated secretory phenotype', comprising secretion of chemokines, interleukins and other growth factors, thereby potentiating oncogene-driven growth. Moreover, conditioned supernatant of CML-G2 cells markedly enhanced proliferation of CML-WT and pre-senescent CML-iG4 cells. Strikingly, a similar inflammatory mRNA expression pattern was found with disease progression from chronic phase to accelerated phase in CML patients. These findings demonstrate that telomere-induced senescence needs to be bypassed by leukemic cells in order to progress to blast crisis and provide a novel mechanism by which telomere shortening may contribute to disease evolution in CML. PMID:24603533

  13. Telomere Biology in Metazoa

    PubMed Central

    Gomes, Nuno M.V.; Shay, Jerry W.; Wright, Woodring E.

    2010-01-01

    In this review we present critical overview of some of the available literature on the fundamental biology of telomeres and telomerase in Metazoan. With the exception of Nematodes and Arthropods, the (TTAGGG)n sequence is conserved in most Metazoa. Available data shows that telomerase-based end maintenance is a very ancient mechanism in unicellular and multicellular organisms. In invertebrates, fish, amphibian, and reptiles persistent telomerase activity in somatic tissues might allow the maintenance of the extensive regenerative potentials of these species. Telomerase repression among birds and many mammals suggests that, as humans, they may use replicative aging as a tumor protection mechanism. PMID:20655915

  14. The topoisomerase II catalytic inhibitor ICRF-193 preferentially targets telomeres that are capped by TRF2.

    PubMed

    Chen, Lianxiang; Zhu, Xiaowei; Zou, Yaru; Xing, Jun; Gilson, Eric; Lu, Yiming; Ye, Jing

    2015-03-01

    The increased level of chromosome instability in cancer cells is not only a driving force for oncogenesis but also can be the Achille's heel of the disease since many chemotherapies kill cells by inducing a nontolerable rate of DNA damage. A wealth of published evidence showed that telomere stability can be more affected than the bulk of the genome by several conventional antineoplastic drugs. In the present study, HT1080 cell lines compromised for either telomere repeats binding factor 2 (TRF2) or POT1 were treated with ICRF-193 (3 μM, 24 h) or bleomycin (1 μM, 24 h). DNA damage was assayed by combining telomeric DNA staining of a (CCCTAA)n PNA probe with immunofluorescence of 53BP1 to score the rate of telomere colocalization with 53BP1 foci. We found that ICRF-193, but not bleomycin, leads to DNA damage preferentially at telomeres, which can be rescued by TRF2 inhibition. POT1 inhibition exacerbates telomere dysfunction induced by ICRF-193. Thus, ICRF-193 induces damage at telomeres properly capped by TRF2 but not by POT1. These findings are expected to broaden our view on the mechanism by which conventional therapeutic molecules act to eliminate cancer cells and how to use TRF2 and POT1 levels as surrogate markers for anti-topoisomerase II sensitivity. PMID:25518961

  15. TRF2/RAP1 and DNA-PK mediate a double protection against joining at telomeric ends.

    PubMed

    Bombarde, Oriane; Boby, Céline; Gomez, Dennis; Frit, Philippe; Giraud-Panis, Marie-Josèphe; Gilson, Eric; Salles, Bernard; Calsou, Patrick

    2010-05-01

    DNA-dependent protein kinase (DNA-PK) is a double-strand breaks repair complex, the subunits of which (KU and DNA-PKcs) are paradoxically present at mammalian telomeres. Telomere fusion has been reported in cells lacking these proteins, raising two questions: how is DNA-PK prevented from initiating classical ligase IV (LIG4)-dependent non-homologous end-joining (C-NHEJ) at telomeres and how is the backup end-joining (EJ) activity (B-NHEJ) that operates at telomeres under conditions of C-NHEJ deficiency controlled? To address these questions, we have investigated EJ using plasmid substrates bearing double-stranded telomeric tracks and human cell extracts with variable C-NHEJ or B-NHEJ activity. We found that (1) TRF2/RAP1 prevents C-NHEJ-mediated end fusion at the initial DNA-PK end binding and activation step and (2) DNA-PK counteracts a potent LIG4-independent EJ mechanism. Thus, telomeres are protected against EJ by a lock with two bolts. These results account for observations with mammalian models and underline the importance of alternative non-classical EJ pathways for telomere fusions in cells. PMID:20407424

  16. Potential Risks in the Paradigm of Basic to Translational Research: A Critical Evaluation of qPCR Telomere Size Techniques

    PubMed Central

    Lustig, Arthur J

    2015-01-01

    Real time qPCR has become the method of choice for rapid large-scale telomere length measurements. Large samples sizes are critical for clinical trials, and epidemiological studies. QPCR has become such routine procedure that it is often used with little critical analysis. With proper controls, the mean telomere size can be derived from the data and even the size can be estimated. But there is a need for more consistent and reliable controls that will provide closer to the actual mean size can be obtained with uniform consensus controls. Although originating at the level of basic telomere research, many researchers less familiar with telomeres often misunderstand the source and significance of the qPCR metric. These include researchers and clinicians who are interested in having a rapid tool to produce exciting results in disease prognostics and diagnostics than in the multiple characteristics of telomeres that form the basis of the measurement. But other characteristics of the non-bimodal and heterogeneous telomeres as well as the complexities of telomere dynamics are not easily related to qPCR mean telomere values. The qPCR metric does not reveal the heterogeneity and dynamics of telomeres. This is a critical issue since mutations in multiple genes including telomerase can cause telomere dysfunction and a loss of repeats. The smallest cellular telomere has been shown to arrest growth of the cell carrying the dysfunction telomere. A goal for the future is a simple method that takes into account the heterogeneity by measuring the highest and lowest values as part of the scheme to compare. In the absence of this technique, Southern blots need to be performed in a subset of qPCR samples for both mean telomere size and the upper and lower extremes of the distribution. Most importantly, there is a need for greater transparency in discussing the limitations of the qPCR data. Given the potentially exciting qPCR telomere size results emerging from clinical studies that

  17. Telomere stability and carcinogenesis: an off-again, on-again relationship

    PubMed Central

    Wanat, Jennifer J.; Johnson, F. Brad

    2012-01-01

    Previous studies in mice have demonstrated antagonistic effects of telomerase loss on carcinogenesis. Telomere attrition can promote genome instability, thereby stimulating initiation of early-stage cancers, but can also inhibit tumorigenesis by promoting permanent cell growth arrest or death. Human cancers likely develop in cell lineages with low levels of telomerase, leading to telomere losses in early lesions, followed by subsequent activation of telomerase. Mouse models constitutively lacking telomerase have thus not addressed how telomere losses within telomerase-proficient cells have an impact on carcinogenesis. Using a novel transgenic mouse model, Begus-Nahrmann et al. demonstrate in this issue of the JCI that transient telomere dysfunction in telomerase-proficient animals is a potent stimulus of tumor formation. PMID:22622044

  18. The Telomere/Telomerase System in Chronic Inflammatory Diseases. Cause or Effect?

    PubMed

    Kordinas, Vasileios; Ioannidis, Anastasios; Chatzipanagiotou, Stylianos

    2016-01-01

    Telomeres are specialized nucleoprotein structures located at the end of linear chromosomes and telomerase is the enzyme responsible for telomere elongation. Telomerase activity is a key component of many cancer cells responsible for rapid cell division but it has also been found by many laboratories around the world that telomere/telomerase biology is dysfunctional in many other chronic conditions as well. These conditions are characterized by chronic inflammation, a situation mostly overlooked by physicians regarding patient treatment. Among others, these conditions include diabetes, renal failure, chronic obstructive pulmonary disease, etc. Since researchers have in many cases identified the association between telomerase and inflammation but there are still many missing links regarding this correlation, the latest findings about this phenomenon will be discussed by reviewing the literature. Our focus will be describing telomere/telomerase status in chronic diseases under the prism of inflammation, reporting molecular findings where available and proposing possible future approaches. PMID:27598205

  19. The human telomere

    SciTech Connect

    Moyzis, R.K.

    1989-01-01

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

  20. Ergodicity convergence test suggests telomere motion obeys fractional dynamics.

    PubMed

    Kepten, E; Bronshtein, I; Garini, Y

    2011-04-01

    Anomalous diffusion, observed in many biological processes, is a generalized description of a wide variety of processes, all obeying the same law of mean-square displacement. Identifying the basic mechanisms of these observations is important for deducing the nature of the biophysical systems measured. We implement a previously suggested method for distinguishing between fractional Langevin dynamics, fractional Brownian motion, and continuous time random walk based on the ergodic nature of the data. We apply the method together with the recently suggested P-variation test and the displacement correlation to the lately measured dynamics of telomeres in the nucleus of mammalian cells and find strong evidence that the telomeres motion obeys fractional dynamics. The ergodic dynamics are observed experimentally to fit fractional Brownian or Langevin dynamics. PMID:21599212

  1. Ergodicity convergence test suggests telomere motion obeys fractional dynamics

    NASA Astrophysics Data System (ADS)

    Kepten, E.; Bronshtein, I.; Garini, Y.

    2011-04-01

    Anomalous diffusion, observed in many biological processes, is a generalized description of a wide variety of processes, all obeying the same law of mean-square displacement. Identifying the basic mechanisms of these observations is important for deducing the nature of the biophysical systems measured. We implement a previously suggested method for distinguishing between fractional Langevin dynamics, fractional Brownian motion, and continuous time random walk based on the ergodic nature of the data. We apply the method together with the recently suggested P-variation test and the displacement correlation to the lately measured dynamics of telomeres in the nucleus of mammalian cells and find strong evidence that the telomeres motion obeys fractional dynamics. The ergodic dynamics are observed experimentally to fit fractional Brownian or Langevin dynamics.

  2. Telomeres and Telomerase in the Radiation Response: Implications for Instability, Reprograming, and Carcinogenesis.

    PubMed

    Sishc, Brock J; Nelson, Christopher B; McKenna, Miles J; Battaglia, Christine L R; Herndon, Andrea; Idate, Rupa; Liber, Howard L; Bailey, Susan M

    2015-01-01

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

  3. Telomeres and Telomerase in the Radiation Response: Implications for Instability, Reprograming, and Carcinogenesis

    PubMed Central

    Sishc, Brock J.; Nelson, Christopher B.; McKenna, Miles J.; Battaglia, Christine L. R.; Herndon, Andrea; Idate, Rupa; Liber, Howard L.; Bailey, Susan M.

    2015-01-01

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

  4. Extra telomeres, but not internal tracts of telomeric DNA, reduce transcriptional repression at Saccharomyces telomeres

    SciTech Connect

    Wiley, E.A.; Zakian, V.A.

    1995-01-01

    Yeast telomeric DNA is assembled into a nonnucleosomal chromatin structure known as the telosome, which is thought to influence the transcriptional repression of genes placed in its vicinity, a phenomenon called telomere position effect (TPE). The product of the RAP1 gene, Rap1p, is a component of the telosome. We show that the fraction of cells exhibiting TPE can be substantially reduced by expressing large amounts of a deletion derivative of Rap1p that is unable to bind DNA, called Rap1{Delta}BBp, or by introducing extra telomeres on a linear plasmid, presumably because both compete in trans with telomeric chromatin for factor(s) important for TPE. This reduction in TPE, observed in three different strains, was demonstrated for two different genes, each assayed at a different telomere. In contrast, the addition of internal tracts of telomeric DNA on a circular plasmid had very little effect on TPE. The product of the SIR3 gene, Sir3p, appears to be limiting for TPE. Overexpression of Sir3p completely suppressed the reduction in TPE observed with expression of Rap1{Delta}BBp, but did not restore high levels of TPE to cells with extra telomeres. These results suggest that extra telomeres must titrate a factor other than Sir3p that is important for TPE. These results also provide evidence for a terminus-specific binding factor that is a factor with a higher affinity for DNA termini than for nonterminal tracts of telomeric DNA and indicate that this factor is important for TPE. 51 refs., 8 figs., 1 tab.

  5. Extra Telomeres, but Not Internal Tracts of Telomeric Dna, Reduce Transcriptional Repression at Saccharomyces Telomeres

    PubMed Central

    Wiley, E. A.; Zakian, V. A.

    1995-01-01

    Yeast telomeric DNA is assembled into a nonnucleosomal chromatin structure known as the telosome, which is thought to influence the transcriptional repression of genes placed in its vicinity, a phenomenon called telomere position effect (TPE). The product of the RAP1 gene, Rap1p, is a component of the telosome. We show that the fraction of cells exhibiting TPE can be substantially reduced by expressing large amounts of a deletion derivative of Rap1p that is unable to bind DNA, called Rap1δBBp, or by introducing extra telomeres on a linear plasmid, presumably because both compete in trans with telomeric chromatin for factor(s) important for TPE. This reduction in TPE, observed in three different strains, was demonstrated for two different genes, each assayed at a different telomere. In contrast, the addition of internal tracts of telomeric DNA on a circular plasmid had very little effect on TPE. The product of the SIR3 gene, Sir3p, appears to be limiting for TPE. Overexpression of Sir3p completely suppressed the reduction in TPE observed with expression of Rap1δBBp, but did not restore high levels of TPE to cells with extra telomeres. These results suggest that extra telomeres must titrate a factor other than Sir3p that is important for TPE. These results also provide evidence for a terminus-specific binding factor that is a factor with a higher affinity for DNA termini than for nonterminal tracts of telomeric DNA and indicate that this factor is important for TPE. PMID:7705652

  6. Telomeres and telomere dynamics: relevance to cancers of the gastrointestinal tract

    PubMed Central

    Basu, Nivedita; Skinner, Halcyon G.; Litzelman, Kristin; Vanderboom, Russell; Baichoo, Esha; Boardman, Lisa A.

    2013-01-01

    Summary Aberrations in telomere length and telomere maintenance contribute to cancer development. In this article, we review basic principles of telomere length in normal and tumor tissue and the presence of the two main telomere maintenance pathways as they pertain to GI tract cancer. Peripheral blood telomeres are shorter in patients with many types of GI tract cancers. Telomere length in tumor DNA also appears to shorten early in cancer development. Tumor telomere shortening is often accompanied by telomerase activation to protect genetically damaged DNA from normal cell senescence or apoptosis, allowing immortalized but damaged DNA to persist. Alternative lengthening of telomeres (ALT) is another mechanism used by cancer to maintain telomere length in cancer cells. Telomerase and ALT activators and inhibitors may become important chemopreventive or chemotherapeutic agents as our understanding of telomere biology, specific telomere related phenotypes, and its relationship to carcinogenesis increases. PMID:24161135

  7. Telomere Length in Peripheral Blood Leukocytes and Lung Cancer Risk: A Large Case-Control Study in Caucasians

    PubMed Central

    Sanchez-Espiridion, Beatriz; Chen, Meng; Chang, Joe Y.; Lu, Charles; Chang, David W.; Roth, Jack A.; Wu, Xifeng; Gu, Jian

    2015-01-01

    Telomere dysfunction is a crucial event in malignant transformation and tumorigenesis. Telomere length in peripheral blood leukocytes has been associated with lung cancer risk, but the relationship has remained controversial. In this study, we investigated whether the association might be confounded by study of different histological subtypes of lung cancer. We measured relative telomere lengths in patients in a large case-control study of lung cancer and performed stratified analyses according to the two major histological subtypes (adenocarcinoma [AC] and squamous cell carcinoma [SCC]). Notably, AC patients had longer telomeres than controls, whereas SCC patients had shorter telomeres compared to controls. Long telomeres were associated with increased risk of AC, with the highest risk associated with female sex, younger age (<60 years) and lighter smoking (<30 pack-years). In contrast, long telomeres were protective against SCC, particularly in male patients. Our results extend the concept that telomere length affects risk of lung cancer in a manner that differs with histological subtype. PMID:24618342

  8. TRIP6 and LPP, but not Zyxin, are present at a subset of telomeres in human cells

    PubMed Central

    Sheppard, Samantha A; Savinova, Tatiana

    2011-01-01

    The protection of chromosome ends requires the inhibition of DNA damage responses at telomeres. This inhibition is exerted in great part by the shelterin complex, known to prevent inappropriate ATM and ATR activation. The molecular mechanisms by which shelterin protects telomeres are incompletely understood. Recently, we have implicated for the first time a class of molecules, LIM domain proteins, in telomere protection. This protection occurred through interaction with shelterin, possibly through POT1, and required the pair of LIM proteins TRIP6 and LPP, themselves part of the Zyxin family. The domain similarity between TRIP6, LPP and Zyxin led us to ask whether the latter also interacted with telomeres. Here, we show that there is specificity in the association of LIM proteins with telomeres: Zyxin, despite a high degree of similarity with TRIP6 and LPP, was not detected at telomeres, nor found in a complex with shelterin. TRIP6 and LPP, however, were detected by immunofluorescence at a small subset of telomeres, perhaps those that are critically short. We speculate that specific LIM proteins are part of complex events occurring in the context of the telomere dysfunction response and are possibly at play during the induction of senescence. PMID:21519191

  9. Telomerase abrogates aneuploidy-induced telomere replication stress, senescence and cell depletion

    PubMed Central

    Meena, Jitendra K; Cerutti, Aurora; Beichler, Christine; Morita, Yohei; Bruhn, Christopher; Kumar, Mukesh; Kraus, Johann M; Speicher, Michael R; Wang, Zhao-Qi; Kestler, Hans A; d’Adda di Fagagna, Fabrizio; Günes, Cagatay; Rudolph, Karl Lenhard

    2015-01-01

    The causal role of aneuploidy in cancer initiation remains under debate since mutations of euploidy-controlling genes reduce cell fitness but aneuploidy strongly associates with human cancers. Telomerase activation allows immortal growth by stabilizing telomere length, but its role in aneuploidy survival has not been characterized. Here, we analyze the response of primary human cells and murine hematopoietic stem cells (HSCs) to aneuploidy induction and the role of telomeres and the telomerase in this process. The study shows that aneuploidy induces replication stress at telomeres leading to telomeric DNA damage and p53 activation. This results in p53/Rb-dependent, premature senescence of human fibroblast, and in the depletion of hematopoietic cells in telomerase-deficient mice. Endogenous telomerase expression in HSCs and enforced expression of telomerase in human fibroblasts are sufficient to abrogate aneuploidy-induced replication stress at telomeres and the consequent induction of premature senescence and hematopoietic cell depletion. Together, these results identify telomerase as an aneuploidy survival factor in mammalian cells based on its capacity to alleviate telomere replication stress in response to aneuploidy induction. PMID:25820263

  10. Moderate stem-cell telomere shortening rate postpones cancer onset in a stochastic model

    NASA Astrophysics Data System (ADS)

    Holbek, Simon; Bendtsen, Kristian Moss; Juul, Jeppe

    2013-10-01

    Mammalian cells are restricted from proliferating indefinitely. Telomeres at the end of each chromosome are shortened at cell division and when they reach a critical length, the cell will enter permanent cell cycle arrest—a state known as senescence. This mechanism is thought to be tumor suppressing, as it helps prevent precancerous cells from dividing uncontrollably. Stem cells express the enzyme telomerase, which elongates the telomeres, thereby postponing senescence. However, unlike germ cells and most types of cancer cells, stem cells only express telomerase at levels insufficient to fully maintain the length of their telomeres, leading to a slow decline in proliferation potential. It is not yet fully understood how this decline influences the risk of cancer and the longevity of the organism. We here develop a stochastic model to explore the role of telomere dynamics in relation to both senescence and cancer. The model describes the accumulation of cancerous mutations in a multicellular organism and creates a coherent theoretical framework for interpreting the results of several recent experiments on telomerase regulation. We demonstrate that the longest average cancer-free lifespan before cancer onset is obtained when stem cells start with relatively long telomeres that are shortened at a steady rate at cell division. Furthermore, the risk of cancer early in life can be reduced by having a short initial telomere length. Finally, our model suggests that evolution will favor a shorter than optimal average cancer-free lifespan in order to postpone cancer onset until late in life.

  11. Human telomeric proteins occupy selective interstitial sites

    PubMed Central

    Yang, Dong; Xiong, Yuanyan; Kim, Hyeung; He, Quanyuan; Li, Yumei; Chen, Rui; Songyang, Zhou

    2011-01-01

    Human telomeres are bound and protected by protein complexes assembled around the six core telomeric proteins RAP1, TRF1, TRF2, TIN2, TPP1, and POT1. The function of these proteins on telomeres has been studied extensively. Recently, increasing evidence has suggested possible roles for these proteins outside of telomeres. However, the non-canonical (extra-telomeric) function of human telomeric proteins remains poorly understood. To this end, we systematically investigated the binding sites of telomeric proteins along human chromosomes, by performing whole-genome chromatin immunoprecipitation (ChIP) for RAP1 and TRF2. ChIP sequencing (ChIP-seq) revealed that RAP1 and TRF2 could be found on a small number of interstitial sites, including regions that are proximal to genes. Some of these binding sites contain short telomere repeats, suggesting that telomeric proteins could directly bind to interstitial sites. Interestingly, only a small fraction of the available interstitial telomere repeat-containing regions were occupied by RAP1 and TRF2. Ectopically expressed TRF2 was able to occupy additional interstitial telomere repeat sites, suggesting that protein concentration may dictate the selective targeting of telomeric proteins to interstitial sites. Reducing RAP1 and TRF2 expression by RNA interference led to altered transcription of RAP1- and TRF2-targeted genes. Our results indicate that human telomeric proteins could occupy a limited number of interstitial sites and regulate gene transcription. PMID:21423278

  12. Urinary Dysfunction

    MedlinePlus

    ... PCF Spotlight Glossary African American Men Living with Prostate Cancer Urinary Dysfunction Side Effects Urinary Dysfunction Bowel Dysfunction ... dysfunction is normal following initial therapy for localized prostate cancer. But it’s important to realize that not all ...

  13. The role of telomeres and vitamin D in cellular aging and age-related diseases.

    PubMed

    Pusceddu, Irene; Farrell, Christopher-John L; Di Pierro, Angela Maria; Jani, Erika; Herrmann, Wolfgang; Herrmann, Markus

    2015-10-01

    Aging is a complex biological process characterized by a progressive decline of organ functions leading to an increased risk of age-associated diseases and death. Decades of intensive research have identified a range of molecular and biochemical pathways contributing to aging. However, many aspects regarding the regulation and interplay of these pathways are insufficiently understood. Telomere dysfunction and genomic instability appear to be of critical importance for aging at a cellular level. For example, age-related diseases and premature aging syndromes are frequently associated with telomere shortening. Telomeres are repetitive nucleotide sequences that together with the associated sheltrin complex protect the ends of chromosomes and maintain genomic stability. Recent studies suggest that micronutrients, such as vitamin D, folate and vitamin B12, are involved in telomere biology and cellular aging. In particular, vitamin D is important for a range of vital cellular processes including cellular differentiation, proliferation and apoptosis. As a result of the multiple functions of vitamin D it has been speculated that vitamin D might play a role in telomere biology and genomic stability. Here we review existing knowledge about the link between telomere biology and cellular aging with a focus on the role of vitamin D. We searched the literature up to November 2014 for human studies, animal models and in vitro experiments that addressed this topic. PMID:25803084

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

    PubMed Central

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

    2015-01-01

    Current methods for characterizing extrachromosomal nuclear DNA in mammalian cells do not permit single-cell analysis, are often semi-quantitative and frequently biased toward the detection of circular species. To overcome these limitations, we developed Halo-FISH to visualize and quantitatively analyze extrachromosomal DNA in single cells. We demonstrate Halo-FISH by using it to analyze extrachromosomal telomere-repeat (ECTR) in human cells that use the Alternative Lengthening of Telomeres (ALT) pathway(s) to maintain telomere lengths. We find that GM847 and VA13 ALT cells average ∼80 detectable G/C-strand ECTR DNA molecules/nucleus, while U2OS ALT cells average ∼18 molecules/nucleus. In comparison, human primary and telomerase-positive cells contain <5 ECTR DNA molecules/nucleus. ECTR DNA in ALT cells exhibit striking cell-to-cell variations in number (<20 to >300), range widely in length (<1 to >200 kb) and are composed of primarily G- or C-strand telomere-repeat DNA. Halo-FISH enables, for the first time, the simultaneous analysis of ECTR DNA and chromosomal telomeres in a single cell. We find that ECTR DNA comprises ∼15% of telomere-repeat DNA in GM847 and VA13 cells, but <4% in U2OS cells. In addition to its use in ALT cell analysis, Halo-FISH can facilitate the study of a wide variety of extrachromosomal DNA in mammalian cells. PMID:25662602

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

    PubMed

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

    2015-02-27

    Current methods for characterizing extrachromosomal nuclear DNA in mammalian cells do not permit single-cell analysis, are often semi-quantitative and frequently biased toward the detection of circular species. To overcome these limitations, we developed Halo-FISH to visualize and quantitatively analyze extrachromosomal DNA in single cells. We demonstrate Halo-FISH by using it to analyze extrachromosomal telomere-repeat (ECTR) in human cells that use the Alternative Lengthening of Telomeres (ALT) pathway(s) to maintain telomere lengths. We find that GM847 and VA13 ALT cells average ∼80 detectable G/C-strand ECTR DNA molecules/nucleus, while U2OS ALT cells average ∼18 molecules/nucleus. In comparison, human primary and telomerase-positive cells contain <5 ECTR DNA molecules/nucleus. ECTR DNA in ALT cells exhibit striking cell-to-cell variations in number (<20 to >300), range widely in length (<1 to >200 kb) and are composed of primarily G- or C-strand telomere-repeat DNA. Halo-FISH enables, for the first time, the simultaneous analysis of ECTR DNA and chromosomal telomeres in a single cell. We find that ECTR DNA comprises ∼15% of telomere-repeat DNA in GM847 and VA13 cells, but <4% in U2OS cells. In addition to its use in ALT cell analysis, Halo-FISH can facilitate the study of a wide variety of extrachromosomal DNA in mammalian cells. PMID:25662602

  16. How do telomeres and NHEJ coexist?

    PubMed Central

    Marcand, Stéphane

    2014-01-01

    The telomeres of eukaryotes are stable open double-strand ends that coexist with nonhomologous end joining (NHEJ), the repair pathway that directly ligates DNA ends generated by double-strand breaks. Since a single end-joining event between 2 telomeres generates a circular chromosome or an unstable dicentric chromosome, NHEJ must be prevented from acting on telomeres. Multiple mechanisms mediated by telomere factors act in synergy to achieve this inhibition. PMID:27308342

  17. Bortezomib-mediated down-regulation of telomerase and disruption of telomere homeostasis contributes to apoptosis of malignant cells.

    PubMed

    Ci, Xinyu; Li, Bingnan; Ma, Xueping; Kong, Feng; Zheng, Chengyun; Björkholm, Magnus; Jia, Jihui; Xu, Dawei

    2015-11-10

    Bortezomib inhibits the ubiquitin/proteasome pathway to achieve its anti-cancer effect and its well characterized activity is the NF-κB inhibition through which the anti-apoptotic bcl-2 expression is down-regulated and apoptosis is subsequently induced. However, the downstream molecular targets of bortezomib are still incompletely defined. Because telomere stabilization via activation of telomerase, induction of telomerase reverse transcriptase (hTERT) and appropriate expression of shelterin proteins is essential to cancer development and progression, we investigated the effect of bortezomib on telomere homeostasis/function in malignant cells. The bortezomib treatment of leukemic (HEL) and gastric cancer cells (BGC-823) led to significant inhibition of hTERT and telomerase expression, widespread dysregulation of shelterin protein expression, and telomere shortening, thereby triggering telomere dysfunction and DNA damage. hTERT over-expression attenuated bortezomib-induced telomere shortening, abnormal shelterin expression and telomere dysfunction. Importantly, bortezomib-mediated apoptosis of malignant cells was partially prevented by hTERT over-expression. Mechanistically, hTERT first robustly enhances bcl2 expression and maintains significantly high residual levels of bcl2 even in bortezomib-treated HEL cells. Second, hTERT protects against bortezomib-induced DNA damage. Our findings collectively reveal a profound impact of bortezomib on telomere homeostasis/function. Down-regulation of hTERT expression and telomere dysfunction induced by bortezomib both contribute to its cancer cell killing actions. It is evident from the present study that hTERT can confer resistance of malignant cells to bortezomib-based target cancer therapy, which may have important clinical implications. PMID:26472030

  18. Bortezomib-mediated down-regulation of telomerase and disruption of telomere homeostasis contributes to apoptosis of malignant cells

    PubMed Central

    Ci, Xinyu; Li, Bingnan; Ma, Xueping; Kong, Feng; Zheng, Chengyun; Björkholm, Magnus; Jia, Jihui; Xu, Dawei

    2015-01-01

    Bortezomib inhibits the ubiquitin/proteasome pathway to achieve its anti-cancer effect and its well characterized activity is the NF-κB inhibition through which the anti-apoptotic bcl-2 expression is down-regulated and apoptosis is subsequently induced. However, the downstream molecular targets of bortezomib are still incompletely defined. Because telomere stabilization via activation of telomerase, induction of telomerase reverse transcriptase (hTERT) and appropriate expression of shelterin proteins is essential to cancer development and progression, we investigated the effect of bortezomib on telomere homeostasis/function in malignant cells. The bortezomib treatment of leukemic (HEL) and gastric cancer cells (BGC-823) led to significant inhibition of hTERT and telomerase expression, widespread dysregulation of shelterin protein expression, and telomere shortening, thereby triggering telomere dysfunction and DNA damage. hTERT over-expression attenuated bortezomib-induced telomere shortening, abnormal shelterin expression and telomere dysfunction. Importantly, bortezomib-mediated apoptosis of malignant cells was partially prevented by hTERT over-expression. Mechanistically, hTERT first robustly enhances bcl2 expression and maintains significantly high residual levels of bcl2 even in bortezomib-treated HEL cells. Second, hTERT protects against bortezomib-induced DNA damage. Our findings collectively reveal a profound impact of bortezomib on telomere homeostasis/function. Down-regulation of hTERT expression and telomere dysfunction induced by bortezomib both contribute to its cancer cell killing actions. It is evident from the present study that hTERT can confer resistance of malignant cells to bortezomib-based target cancer therapy, which may have important clinical implications. PMID:26472030

  19. Characterization of the Yeast Telomere Nucleoprotein Core

    PubMed Central

    Williams, Tanya L.; Levy, Daniel L.; Maki-Yonekura, Saori; Yonekura, Koji; Blackburn, Elizabeth H.

    2010-01-01

    At the core of Saccharomyces cerevisiae telomeres is an array of tandem telomeric DNA repeats bound site-specifically by multiple Rap1 molecules. There, Rap1 orchestrates the binding of additional telomere-associated proteins and negatively regulates both telomere fusion and length homeostasis. Using electron microscopy, viscosity, and light scattering measurements, we show that purified Rap1 is a monomer in solution that adopts a ringlike or C shape with a central cavity. Rap1 could orchestrate telomere function by binding multiple telomere array sites through either cooperative or independent mechanisms. To determine the mechanism, we analyze the distribution of Rap1 monomers on defined telomeric DNA arrays. This analysis clearly indicates that Rap1 binds independently to each nonoverlapping site in an array, regardless of the spacing between sites, the total number of sites, the affinity of the sites for Rap1, and over a large concentration range. Previous experiments have not clearly separated the effects of affinity from repeat spacing on telomere function. We clarify these results by testing in vivo the function of defined telomere arrays containing the same Rap1 binding site separated by spacings that were previously defined as low or high activity. We find that Rap1 binding affinity in vitro correlates with the ability of telomeric repeat arrays to regulate telomere length in vivo. We suggest that Rap1 binding to multiple sites in a telomere array does not, by itself, promote formation of a more energetically stabile complex. PMID:20826803

  20. Telomeres, A Busy Platform for Cell Signaling

    PubMed Central

    Gardano, Laura; Pucci, Fabio; Christian, Larissa; Le Bihan, Thierry; Harrington, Lea

    2013-01-01

    Telomeres are the terminal structures at the ends of linear chromosomes that represent a solution to the end replication problem. Specific binding of the six-protein subunit complex shelterin to telomeric, repetitive TTAGGG DNA sequences contributes to the stable architecture and maintenance of telomeres. Proteins involved in the DNA damage response are also localized at telomeres, and play a role in the surveillance and maintenance of telomere integrity. The enzyme responsible for telomere extension is telomerase, a ribonucleoprotein with reverse transcriptase activity. In the absence of telomerase, telomeres shorten to a length threshold that triggers the DNA damage response and replicative senescence. Here, we will summarize the latest findings concerning vertebrate telomere structure and epigenetics, and we present data regarding the impact of short telomeres upon cell signaling. In particular, in murine embryonic stem cells lacking telomerase, we found that distribution of cytosolic/nuclear β-catenin, a key component of the Wnt signaling pathway, changes when telomeres become critically short. We discuss implications and future perspectives of the effect of epigenetic modifications and/or conformational changes of telomeres on cell metabolism and signaling networks. Such an analysis may unveil potential therapeutic targets for pathologies like cancer, where the integrity of telomeres is altered. PMID:23772418

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

    PubMed

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

    2014-01-01

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

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

    PubMed

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

    2016-01-01

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

  3. Histone H3.3 maintains genome integrity during mammalian development

    PubMed Central

    Jang, Chuan-Wei; Shibata, Yoichiro; Starmer, Joshua; Yee, Della; Magnuson, Terry

    2015-01-01

    Histone H3.3 is a highly conserved histone H3 replacement variant in metazoans and has been implicated in many important biological processes, including cell differentiation and reprogramming. Germline and somatic mutations in H3.3 genomic incorporation pathway components or in H3.3 encoding genes have been associated with human congenital diseases and cancers, respectively. However, the role of H3.3 in mammalian development remains unclear. To address this question, we generated H3.3-null mouse models through classical genetic approaches. We found that H3.3 plays an essential role in mouse development. Complete depletion of H3.3 leads to developmental retardation and early embryonic lethality. At the cellular level, H3.3 loss triggers cell cycle suppression and cell death. Surprisingly, H3.3 depletion does not dramatically disrupt gene regulation in the developing embryo. Instead, H3.3 depletion causes dysfunction of heterochromatin structures at telomeres, centromeres, and pericentromeric regions of chromosomes, leading to mitotic defects. The resulting karyotypical abnormalities and DNA damage lead to p53 pathway activation. In summary, our results reveal that an important function of H3.3 is to support chromosomal heterochromatic structures, thus maintaining genome integrity during mammalian development. PMID:26159997

  4. HipHop interacts with HOAP and HP1 to protect Drosophila telomeres in a sequence-independent manner

    PubMed Central

    Gao, Guanjun; Walser, Jean-Claude; Beaucher, Michelle L; Morciano, Patrizia; Wesolowska, Natalia; Chen, Jie; Rong, Yikang S

    2010-01-01

    Telomeres prevent chromosome ends from being repaired as double-strand breaks (DSBs). Telomere identity in Drosophila is determined epigenetically with no sequence either necessary or sufficient. To better understand this sequence-independent capping mechanism, we isolated proteins that interact with the HP1/ORC-associated protein (HOAP) capping protein, and identified HipHop as a subunit of the complex. Loss of one protein destabilizes the other and renders telomeres susceptible to fusion. Both HipHop and HOAP are enriched at telomeres, where they also interact with the conserved HP1 protein. We developed a model telomere lacking repetitive sequences to study the distribution of HipHop, HOAP and HP1 using chromatin immunoprecipitation (ChIP). We discovered that they occupy a broad region >10 kb from the chromosome end and their binding is independent of the underlying DNA sequence. HipHop and HOAP are both rapidly evolving proteins yet their telomeric deposition is under the control of the conserved ATM and Mre11–Rad50–Nbs (MRN) proteins that modulate DNA structures at telomeres and at DSBs. Our characterization of HipHop and HOAP reveals functional analogies between the Drosophila proteins and subunits of the yeast and mammalian capping complexes, implicating conservation in epigenetic capping mechanisms. PMID:20057353

  5. HipHop interacts with HOAP and HP1 to protect Drosophila telomeres in a sequence-independent manner.

    PubMed

    Gao, Guanjun; Walser, Jean-Claude; Beaucher, Michelle L; Morciano, Patrizia; Wesolowska, Natalia; Chen, Jie; Rong, Yikang S

    2010-02-17

    Telomeres prevent chromosome ends from being repaired as double-strand breaks (DSBs). Telomere identity in Drosophila is determined epigenetically with no sequence either necessary or sufficient. To better understand this sequence-independent capping mechanism, we isolated proteins that interact with the HP1/ORC-associated protein (HOAP) capping protein, and identified HipHop as a subunit of the complex. Loss of one protein destabilizes the other and renders telomeres susceptible to fusion. Both HipHop and HOAP are enriched at telomeres, where they also interact with the conserved HP1 protein. We developed a model telomere lacking repetitive sequences to study the distribution of HipHop, HOAP and HP1 using chromatin immunoprecipitation (ChIP). We discovered that they occupy a broad region >10 kb from the chromosome end and their binding is independent of the underlying DNA sequence. HipHop and HOAP are both rapidly evolving proteins yet their telomeric deposition is under the control of the conserved ATM and Mre11-Rad50-Nbs (MRN) proteins that modulate DNA structures at telomeres and at DSBs. Our characterization of HipHop and HOAP reveals functional analogies between the Drosophila proteins and subunits of the yeast and mammalian capping complexes, implicating conservation in epigenetic capping mechanisms. PMID:20057353

  6. Histone variant H3.3 provides the heterochromatic H3 lysine 9 tri-methylation mark at telomeres

    PubMed Central

    Udugama, Maheshi; M. Chang, Fiona T.; Chan, F. Lyn; Tang, Michelle C.; Pickett, Hilda A.; R. McGhie, James D.; Mayne, Lynne; Collas, Philippe; Mann, Jeffrey R.; Wong, Lee H.

    2015-01-01

    In addition to being a hallmark at active genes, histone variant H3.3 is deposited by ATRX at repressive chromatin regions, including the telomeres. It is unclear how H3.3 promotes heterochromatin assembly. We show that H3.3 is targeted for K9 trimethylation to establish a heterochromatic state enriched in trimethylated H3.3K9 at telomeres. In H3f3a−/− and H3f3b−/− mouse embryonic stem cells (ESCs), H3.3 deficiency results in reduced levels of H3K9me3, H4K20me3 and ATRX at telomeres. The H3f3b−/− cells show increased levels of telomeric damage and sister chromatid exchange (t-SCE) activity when telomeres are compromised by treatment with a G-quadruplex (G4) DNA binding ligand or by ASF1 depletion. Overexpression of wild-type H3.3 (but not a H3.3K9 mutant) in H3f3b−/− cells increases H3K9 trimethylation level at telomeres and represses t-SCE activity induced by a G4 ligand. This study demonstrates the importance of H3.3K9 trimethylation in heterochromatin formation at telomeres. It provides insights into H3.3 function in maintaining integrity of mammalian constitutive heterochromatin, adding to its role in mediating transcription memory in the genome. PMID:26304540

  7. Sister chromatid telomere fusions, but not NHEJ-mediated inter-chromosomal telomere fusions, occur independently of DNA ligases 3 and 4

    PubMed Central

    Liddiard, Kate; Ruis, Brian; Takasugi, Taylor; Harvey, Adam; Ashelford, Kevin E.; Hendrickson, Eric A.; Baird, Duncan M.

    2016-01-01

    Telomeres shorten with each cell division and can ultimately become substrates for nonhomologous end-joining repair, leading to large-scale genomic rearrangements of the kind frequently observed in human cancers. We have characterized more than 1400 telomere fusion events at the single-molecule level, using a combination of high-throughput sequence analysis together with experimentally induced telomeric double-stranded DNA breaks. We show that a single chromosomal dysfunctional telomere can fuse with diverse nontelomeric genomic loci, even in the presence of an otherwise stable genome, and that fusion predominates in coding regions. Fusion frequency was markedly increased in the absence of TP53 checkpoint control and significantly modulated by the cellular capacity for classical, versus alternative, nonhomologous end joining (NHEJ). We observed a striking reduction in inter-chromosomal fusion events in cells lacking DNA ligase 4, in contrast to a remarkably consistent profile of intra-chromosomal fusion in the context of multiple genetic knockouts, including DNA ligase 3 and 4 double-knockouts. We reveal distinct mutational signatures associated with classical NHEJ-mediated inter-chromosomal, as opposed to alternative NHEJ-mediated intra-chromosomal, telomere fusions and evidence for an unanticipated sufficiency of DNA ligase 1 for these intra-chromosomal events. Our findings have implications for mechanisms driving cancer genome evolution. PMID:26941250

  8. Antioxidants safeguard telomeres in bold chicks

    PubMed Central

    Kim, Sin-Yeon; Velando, Alberto

    2015-01-01

    Telomeres are sensitive to damage induced by oxidative stress, and thus it is expected that dietary antioxidants may support the maintenance of telomere length in animals, particularly those with a fast rate of life (e.g. fast metabolism, activity and growth). We tested experimentally the effect of antioxidant supplements on telomere length during early development in wild gull chicks with natural individual variations in behaviour pattern and growth rate. Proactive chicks had shorter telomeres than reactive chicks, but the penalty for the bold behaviour pattern was reduced by antioxidant supplementation. Chicks growing faster had longer telomeres during early growth, suggesting that inherited quality supports a fast life history. PMID:25948570

  9. Antioxidants safeguard telomeres in bold chicks.

    PubMed

    Kim, Sin-Yeon; Velando, Alberto

    2015-05-01

    Telomeres are sensitive to damage induced by oxidative stress, and thus it is expected that dietary antioxidants may support the maintenance of telomere length in animals, particularly those with a fast rate of life (e.g. fast metabolism, activity and growth). We tested experimentally the effect of antioxidant supplements on telomere length during early development in wild gull chicks with natural individual variations in behaviour pattern and growth rate. Proactive chicks had shorter telomeres than reactive chicks, but the penalty for the bold behaviour pattern was reduced by antioxidant supplementation. Chicks growing faster had longer telomeres during early growth, suggesting that inherited quality supports a fast life history. PMID:25948570

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

    PubMed

    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. PMID:17050546

  11. Telomere length in early life predicts lifespan

    PubMed Central

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

    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 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 < 0.001); those individuals living longest had relatively long 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. PMID:22232671

  12. Shelterin Protects Chromosome Ends by Compacting Telomeric Chromatin.

    PubMed

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

    2016-02-11

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

  13. Telomerase inhibition and telomere targeting in hematopoietic cancer cell lines with small non-nucleosidic synthetic compounds (BIBR1532).

    PubMed

    El Daly, Hesham; Martens, Uwe M

    2007-01-01

    Telomere maintenance has been shown to be essential for unlimited growth potential of human cells and is regarded as one hallmark of cancer. Telomere repeats at the ends of eukaryotic chromosomes are synthesized by the enzyme telomerase, which is active in most cancers and to some extend also in normal somatic cells. Therefore, targeting the telomerase/telomere complex offers great potential for the development of novel anticancer therapeutics. An example of such a strategy is the small molecule BIBR1532 that is a selective, non-nucleosidic inhibitor of the catalytic component hTERT. Treatment of cancer cells with this compound leads to progressive telomere shortening, consecutive telomere dysfunction, and finally growth arrest after a lag period that is largely dependent on initial telomere length. We have additionally shown that using this class of telomerase inhibitor at higher concentrations exerts a direct cytotoxic effect on malignant cells of the hematopoietic system but not on normal stem cells, which appears to derive from direct damage to the structure of individual telomeres. PMID:18369817

  14. Partial pneumonectomy of telomerase null mice carrying shortened telomeres initiates cell growth arrest resulting in a limited compensatory growth response

    PubMed Central

    Jackson, Sha-Ron; Lee, Jooeun; Reddy, Raghava; Williams, Genevieve N.; Kikuchi, Alexander; Freiberg, Yael; Warburton, David

    2011-01-01

    Telomerase mutations and significantly shortened chromosomal telomeres have recently been implicated in human lung pathologies. Natural telomere shortening is an inevitable consequence of aging, which is also a risk factor for development of lung disease. However, the impact of shortened telomeres and telomerase dysfunction on the ability of lung cells to respond to significant challenge is still largely unknown. We have previously shown that lungs of late generation, telomerase null B6.Cg-Terctm1Rdp mice feature alveolar simplification and chronic stress signaling at baseline, a phenocopy of aged lung. To determine the role telomerase plays when the lung is challenged, B6.Cg-Terctm1Rdp mice carrying shortened telomeres and wild-type controls were subjected to partial pneumonectomy. We found that telomerase activity was strongly induced in alveolar epithelial type 2 cells (AEC2) of the remaining lung immediately following surgery. Eighty-six percent of wild-type animals survived the procedure and exhibited a burst of early compensatory growth marked by upregulation of proliferation, stress response, and DNA repair pathways in AEC2. In B6.Cg-Terctm1Rdp mice carrying shortened telomeres, response to pneumonectomy was characterized by decreased survival, diminished compensatory lung growth, attenuated distal lung progenitor cell response, persistent DNA damage, and cell growth arrest. Overall, survival correlated strongly with telomere length. We conclude that functional telomerase and properly maintained telomeres play key roles in both long-term survival and the early phase of compensatory lung growth following partial pneumonectomy. PMID:21460122

  15. Telomere shortening leads to an acceleration of synucleinopathy and impaired microglia response in a genetic mouse model.

    PubMed

    Scheffold, Annika; Holtman, Inge R; Dieni, Sandra; Brouwer, Nieske; Katz, Sarah-Fee; Jebaraj, Billy Michael Chelliah; Kahle, Philipp J; Hengerer, Bastian; Lechel, André; Stilgenbauer, Stephan; Boddeke, Erik W G M; Eggen, Bart J L; Rudolph, Karl-Lenhard; Biber, Knut

    2016-01-01

    Parkinson's disease is one of the most common neurodegenerative disorders of the elderly and ageing hence described to be a major risk factor. Telomere shortening as a result of the inability to fully replicate the ends of linear chromosomes is one of the hallmarks of ageing. The role of telomere dysfunction in neurological diseases and the ageing brain is not clarified and there is an ongoing discussion whether telomere shortening is linked to Parkinson's disease. Here we studied a mouse model of Parkinson's disease (Thy-1 [A30P] α-synuclein transgenic mouse model) in the background of telomere shortening (Terc knockout mouse model). α-synuclein transgenic mice with short telomeres (αSYN(tg/tg) G3Terc(-/-)) developed an accelerated disease with significantly decreased survival. This accelerated phenotype of mice with short telomeres was characterized by a declined motor performance and an increased formation of α-synuclein aggregates. Immunohistochemical analysis and mRNA expression studies revealed that the disease end-stage brain stem microglia showed an impaired response in αSYN(tg/tg) G3Terc(-/-) microglia animals. These results provide the first experimental data that telomere shortening accelerates α-synuclein pathology that is linked to limited microglia function in the brainstem. PMID:27550225

  16. Cloning and molecular characterization of telomerase reverse transcriptase (TERT) and telomere length analysis of Peromyscus leucopus

    PubMed Central

    Zhao, Xin; Ueda, Yasutaka; Kajigaya, Sachiko; Alaks, Glen; Desierto, Marie J; Townsley, Danielle M.; Dumitriu, Bogdan; Chen, Jichun; Lacy, Robert C.; Young, Neal S.

    2015-01-01

    Telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase complex that regulates telomerase activity to maintain telomere length for all animals with linear chromosomes. As the Mus musculus (MM) laboratory mouse has very long telomeres compared to humans, a potential alternative animal model for telomere research is the Peromyscus leucopus (PL) mouse that has telomere lengths close to the human range and has the wild counterparts for comparison. We report the full TERT coding sequence (pTERT) from PL mice to use in the telomere research. Comparative analysis with eight other mammalian TERTs revealed a pTERT protein considerably homologous to other TERTs and preserved all TERT specific-sequence signatures, yet with some distinctive features. pTERT displayed the highest nucleotide and amino acid sequence homology with hamster TERT. Unlike human but similar to MM mice, pTERT expression was detected in various adult somatic tissues of PL mice, with the highest expression in testes. Four different captive stocks of PL mice and wild-captured PL mice each displayed group-specific average telomere lengths, with the longest and shortest telomeres in inbred and outbred stock mice, respectively. pTERT showed considerable numbers of synonymous and nonsynonymous mutations. A pTERT proximal promoter region cloned was homologous among PL and MM mice and rat, but with species-specific features. From PL mice, we further cloned and characterized ribosomal protein, large, P0 (pRPLP0) to use as an internal control for various assays. Peromyscus mice have been extensively used for various studies, including human diseases, for which pTERT and pRPLP0 would be useful tools. PMID:25962353

  17. Cloning and molecular characterization of telomerase reverse transcriptase (TERT) and telomere length analysis of Peromyscus leucopus.

    PubMed

    Zhao, Xin; Ueda, Yasutaka; Kajigaya, Sachiko; Alaks, Glen; Desierto, Marie J; Townsley, Danielle M; Dumitriu, Bogdan; Chen, Jichun; Lacy, Robert C; Young, Neal S

    2015-08-15

    Telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase complex that regulates telomerase activity to maintain telomere length for all animals with linear chromosomes. As the Mus musculus (MM) laboratory mouse has very long telomeres compared to humans, a potential alternative animal model for telomere research is the Peromyscus leucopus (PL) mouse that has telomere lengths close to the human range and has the wild counterparts for comparison. We report the full TERT coding sequence (pTERT) from PL mice to use in the telomere research. Comparative analysis with eight other mammalian TERTs revealed a pTERT protein considerably homologous to other TERTs and preserved all TERT specific-sequence signatures, yet with some distinctive features. pTERT displayed the highest nucleotide and amino acid sequence homology with hamster TERT. Unlike human but similar to MM mice, pTERT expression was detected in various adult somatic tissues of PL mice, with the highest expression in testes. Four different captive stocks of PL mice and wild-captured PL mice each displayed group-specific average telomere lengths, with the longest and shortest telomeres in inbred and outbred stock mice, respectively. pTERT showed considerable numbers of synonymous and nonsynonymous mutations. A pTERT proximal promoter region cloned was homologous among PL and MM mice and rat, but with species-specific features. From PL mice, we further cloned and characterized ribosomal protein, large, P0 (pRPLP0) to use as an internal control for various assays. Peromyscus mice have been extensively used for various studies, including human diseases, for which pTERT and pRPLP0 would be useful tools. PMID:25962353

  18. Linking functional decline of telomeres, mitochondria and stem cells during ageing

    PubMed Central

    Sahin, Ergün; DePinho, Ronald A.

    2013-01-01

    The study of human genetic disorders and mutant mouse models has provided evidence that genome maintenance mechanisms, DNA damage signalling and metabolic regulation cooperate to drive the ageing process. In particular, age-associated telomere damage, diminution of telomere ‘capping’ function and associated p53 activation have emerged as prime instigators of a functional decline of tissue stem cells and of mitochondrial dysfunction that adversely affect renewal and bioenergetic support in diverse tissues. Constructing a model of how telomeres, stem cells and mitochondria interact with key molecules governing genome integrity, ‘stemness’ and metabolism provides a framework for how diverse factors contribute to ageing and age-related disorders. PMID:20336134

  19. Nestling telomere shortening, but not telomere length, reflects developmental stress and predicts survival in wild birds

    PubMed Central

    Boonekamp, Jelle J.; Mulder, G. A.; Salomons, H. Martijn; Dijkstra, Cor; Verhulst, Simon

    2014-01-01

    Developmental stressors often have long-term fitness consequences, but linking offspring traits to fitness prospects has remained a challenge. Telomere length predicts mortality in adult birds, and may provide a link between developmental conditions and fitness prospects. Here, we examine the effects of manipulated brood size on growth, telomere dynamics and post-fledging survival in free-living jackdaws. Nestlings in enlarged broods achieved lower mass and lost 21% more telomere repeats relative to nestlings in reduced broods, showing that developmental stress accelerates telomere shortening. Adult telomere length was positively correlated with their telomere length as nestling (r = 0.83). Thus, an advantage of long telomeres in nestlings is carried through to adulthood. Nestling telomere shortening predicted post-fledging survival and recruitment independent of manipulation and fledgling mass. This effect was strong, with a threefold difference in recruitment probability over the telomere shortening range. By contrast, absolute telomere length was neither affected by brood size manipulation nor related to survival. We conclude that telomere loss, but not absolute telomere length, links developmental conditions to subsequent survival and suggest that telomere shortening may provide a key to unravelling the physiological causes of developmental effects on fitness. PMID:24789893

  20. Bowel Dysfunction

    MedlinePlus

    ... PCF Spotlight Glossary African American Men Living with Prostate Cancer Bowel Dysfunction Side Effects Urinary Dysfunction Bowel Dysfunction ... rectal worse. Back to Side Effects Print | Understanding Prostate Cancer Research Faces of Prostate Cancer About PCF Take ...

  1. Telomeres and Telomerase in Cardiovascular Diseases.

    PubMed

    Yeh, Jih-Kai; Wang, Chao-Yung

    2016-01-01

    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. PMID:27598203

  2. Three-dimensional telomere architecture of esophageal squamous cell carcinoma: comparison of tumor and normal epithelial cells.

    PubMed

    Sunpaweravong, S; Sunpaweravong, P; Sathitruangsak, C; Mai, S

    2016-05-01

    Telomeres are repetitive nucleotide sequences (TTAGGG)n located at the ends of chromosomes that function to preserve chromosomal integrity and prevent terminal end-to-end fusions. Telomere loss or dysfunction results in breakage-bridge-fusion cycles, aneuploidy, gene amplification and chromosomal rearrangements, which can lead to genomic instability and promote carcinogenesis. Evaluating the hypothesis that changes in telomeres contribute to the development of esophageal squamous cell carcinoma (ESCC) and to determine whether there are differences between young and old patients, we compared the three-dimensional (3D) nuclear telomere architecture in ESCC tumor cells with that of normal epithelial cells obtained from the same patient. Patients were equally divided by age into two groups, one comprising those less than 45 years of age and the other consisting of those over 80 years of age. Tumor and normal epithelial cells located at least 10 cm from the border of the tumor were biopsied in ESCC patients. Hematoxylin and eosin staining was performed for each sample to confirm and identify the cancer and normal epithelial cells. This study was based on quantitative 3D fluorescence in situ hybridization (Q-FISH), 3D imaging and 3D analysis of paraffin-embedded slides. The 3D telomere architecture data were computer analyzed using 100 nuclei per slide. The following were the main parameters compared: the number of signals (number of telomeres), signal intensity (telomere length), number of telomere aggregates, and nuclear volume. Tumor and normal epithelial samples from 16 patients were compared. The normal epithelial cells had more telomere signals and higher intensities than the tumor cells, with P-values of P < 0.0001 and P = 0.0078, respectively. There were no statistically significant differences in the numbers of telomere aggregates or the nuclear volumes between the tumor and normal epithelial cells. Secondary analyses examined the effects of age on 3D telomere

  3. LINE-1 induces hTERT and ensures telomere maintenance in tumour cell lines.

    PubMed

    Aschacher, T; Wolf, B; Enzmann, F; Kienzl, P; Messner, B; Sampl, S; Svoboda, M; Mechtcheriakova, D; Holzmann, K; Bergmann, M

    2016-01-01

    A hallmark of cancer cells is an activated telomere maintenance mechanism, which allows prolonged survival of the malignant cells. In more than 80% of tumours, telomeres are elongated by the enzyme telomerase, which adds de novo telomere repeats to the ends of chromosomes. Cancer cells are also characterized by expression of active LINE-1 elements (L1s, long interspersed nuclear elements-1). L1 elements are abundant retrotransposons in the eukaryotic genome that are primarily known for facilitating aberrant recombination. Using L1-knockdown (KD), we show for the first time that L1 is critical for telomere maintenance in telomerase-positive tumour cells. The reduced length of telomeres in the L1-KD-treated cells correlated with an increased rate of telomere dysfunction foci, a reduced expression of shelterin proteins and an increased rate of anaphase bridges. The decreased telomere length was associated with a decreased telomerase activity and decreased telomerase mRNA level; the latter was increased upon L1 overexpression. L1-KD also led to a decrease in mRNA and protein expression of cMyc and KLF-4, two main transcription factors of telomerase and altered mRNA levels of other stem-cell-associated proteins such as CD44 and hMyb, as well as a corresponding reduced growth of spheroids. The KD of KLF-4 or cMyc decreased the level of L1-ORF1 mRNA, suggesting a specific reciprocal regulation with L1. Thus, our findings contribute to the understanding of L1 as a pathogenicity factor in cancer cells. As L1 is only expressed in pathophysiological conditions, L1 now appears to be target in the rational treatment of telomerase-positive cancer. PMID:25798839

  4. The impact of voluntary exercise on relative telomere length in a rat model of developmental stress

    PubMed Central

    2012-01-01

    Background Exposure to early adverse events can result in the development of later psychopathology, and is often associated with cognitive impairment. This may be due to accelerated cell aging, which can be catalogued by attritioned telomeres. Exercise enhances neurogenesis and has been proposed to buffer the effect of psychological stress on telomere length. This study aimed to investigate the impact of early developmental stress and voluntary exercise on telomere length in the ventral hippocampus (VH) and prefrontal cortex (PFC) of the rat. Forty-five male Sprague–Dawley rats were categorised into four groups: maternally separated runners (MSR), maternally separated non-runners (MSnR), non-maternally separated runners (nMSR) and non-maternally separated non-runners (nMSnR). Behavioural analyses were conducted to assess anxiety-like behaviour and memory performance in the rats, after which relative telomere length was measured using qPCR. Results Maternally separated (MS) rats exhibited no significant differences in either anxiety levels or memory performance on the elevated-plus maze and the open field compared to non-maternally separated rats at 49 days of age. Exercised rats displayed increased levels of anxiety on the day that they were removed from the cages with attached running wheels, as well as improved spatial learning and temporal recognition memory compared to non-exercised rats. Exploratory post-hoc analyses revealed that maternally separated non-exercised rats exhibited significantly longer telomere length in the VH compared to those who were not maternally separated; however, exercise appeared to cancel this effect since there was no difference in VH telomere length between maternally separated and non-maternally separated runners. Conclusions The increased telomere length in the VH of maternally separated non-exercised rats may be indicative of reduced cellular proliferation, which could, in turn, indicate hippocampal dysfunction. This effect on

  5. Shorter telomeres in patients with cerebral autosomal dominant arteriopathy and leukoencephalopathy (CADASIL).

    PubMed

    Ragno, Michele; Pianese, Luigi; Pinelli, Michele; Silvestri, Serena; Cacchiò, Gabriella; Di Marzio, Fabio; Scarcella, Maria; Coretti, Francesco; Altamura, Fabiana; Monticelli, Antonella; Castaldo, Imma

    2011-11-01

    CADASIL is a hereditary systemic vasculopathy which affects mainly small cerebral arteries and is caused by mutations in the Notch3 gene. Misfolding of Notch3 is linked to endoplasmic reticulum stress and increased reactive oxygen species, which may result in dysfunction of endothelial cells, inflammation and ischemia. Oxidative stress and inflammation may induce a rapid telomere shortening in peripheral blood leukocytes (PBLs). The aim of this study was to assess the telomere length in PBLs from 29 patients with a genetic diagnosis of CADASIL by using a modified quantitative real-time polymerase chain reaction based assay. PBL telomere length was significantly shorter in CADASIL patients (T/S ratio = 0.17, 95% CI, 0.14-0.20) than in the controls (T/S ratio = 0.31, 95% CI, 0.27-0.35, t-test p < 0.001). Moreover, patients with functional dependence displayed shorter telomeres than those with functional independence (p = 0.039). Our data provide the first evidence that PBL telomere length is shortened in CADASIL disease, and this may be a systemic oxidative stress indicator in CADASIL patients, providing a possible biomarker of disease progression and for future therapeutic strategies. PMID:21881852

  6. Are Short Telomeres Predictive of Advanced Cancer?

    PubMed Central

    Shay, Jerry W.

    2013-01-01

    Summary The combination of variable telomere length in cancer cells combined with shorter telomere length in cancer-associated stromal cells, strongly correlate with progression to prostate cancer metastasis and cancer death. The implications are that telomere length measurements not only have the potential as a prognostic indicator of prostate cancer outcomes but also as a risk stratification enrichment biomarker for individualized therapeutic interventions. PMID:24124228

  7. Mammalian pheromones.

    PubMed

    Liberles, Stephen D

    2014-01-01

    Mammalian pheromones control a myriad of innate social behaviors and acutely regulate hormone levels. Responses to pheromones are highly robust, reproducible, and stereotyped and likely involve developmentally predetermined neural circuits. Here, I review several facets of pheromone transduction in mammals, including (a) chemosensory receptors and signaling components of the main olfactory epithelium and vomeronasal organ involved in pheromone detection; (b) pheromone-activated neural circuits subject to sex-specific and state-dependent modulation; and (c) the striking chemical diversity of mammalian pheromones, which range from small, volatile molecules and sulfated steroids to large families of proteins. Finally, I review (d) molecular mechanisms underlying various behavioral and endocrine responses, including modulation of puberty and estrous; control of reproduction, aggression, suckling, and parental behaviors; individual recognition; and distinguishing of own species from predators, competitors, and prey. Deconstruction of pheromone transduction mechanisms provides a critical foundation for understanding how odor response pathways generate instinctive behaviors. PMID:23988175

  8. Mammalian Pheromones

    PubMed Central

    Liberles, Stephen D.

    2015-01-01

    Mammalian pheromones control a myriad of innate social behaviors and acutely regulate hormone levels. Responses to pheromones are highly robust, reproducible, and stereotyped and likely involve developmentally predetermined neural circuits. Here, I review several facets of pheromone transduction in mammals, including (a) chemosensory receptors and signaling components of the main olfactory epithelium and vomeronasal organ involved in pheromone detection; (b) pheromone-activated neural circuits subject to sex-specific and state-dependent modulation; and (c) the striking chemical diversity of mammalian pheromones, which range from small, volatile molecules and sulfated steroids to large families of proteins. Finally, I review (d ) molecular mechanisms underlying various behavioral and endocrine responses, including modulation of puberty and estrous; control of reproduction, aggression, suckling, and parental behaviors; individual recognition; and distinguishing of own species from predators, competitors, and prey. Deconstruction of pheromone transduction mechanisms provides a critical foundation for understanding how odor response pathways generate instinctive behaviors. PMID:23988175

  9. Sirtuins: Guardians of Mammalian Healthspan

    PubMed Central

    Giblin, William; Skinner, Mary E.; Lombard, David B.

    2014-01-01

    The first link between sirtuins and longevity was made 15 years ago in yeast. These initial studies sparked efforts by many laboratories working in diverse model organisms to elucidate the relationships between sirtuins, lifespan, and age-associated dysfunction. Here we discuss the current understanding of how sirtuins relate to aging. We focus primarily on mammalian sirtuins SIRT1, SIRT3, and SIRT6, the three sirtuins for which the most relevant data are available. Strikingly, a large body of evidence now indicates that these and other mammalian sirtuins suppress a variety of age-related pathologies and promote healthspan. Moreover, increased expression of SIRT1 or SIRT6 extends mouse lifespan. Overall, these data point to important roles for sirtuins in promoting mammalian health, and perhaps in modulating the aging process. PMID:24877878

  10. Genetic variation in telomere maintenance genes, telomere length, and lung cancer susceptibility

    PubMed Central

    Hosgood, H Dean; Cawthon, Richard; He, Xingzhou; Chanock, Stephen; Lan, Qing

    2009-01-01

    Telomeres are responsible for the protection of the chromosome ends and shortened telomere length has been associated with risk of multiple cancers. Genetic variation in telomere related genes may alter cancer risk associated with telomere length. Using lung cancer cases (n = 120) and population-based controls (n = 110) from Xuanwei, China, we analyzed telomere length separately and in conjunction with single nucleotide polymorphisms in the telomere maintenance genes POT1, TERT, and TERF2, which we have previously reported were associated with risk of lung cancer in this study. POT1 rs10244817, TERT rs2075786, and TERF2 rs251796 were significantly associated with lung cancer (ptrend ≤ 0.05). The shortest tertile of telomere length was not significantly associated with risk of lung cancer (OR = 1.58; 95% CI = 0.79 – 3.18) when compared to the longest tertile of telomere length. When stratified by genotype, there was a suggestion of a dose-response relationship between tertiles of telomere length and risk of lung cancer among the POT1 rs10244817 common variant carriers (OR (95%CI) = 1.33 (0.47 – 3.75), 3.30 (1.14 – 9.56), respectively) but not among variant genotype carriers (pinteraction = 0.05). Our findings provide evidence that telomere length and genetic variation in telomere maintenance genes may be associated with risk of lung cancer susceptibility and warrant replication in larger studies. PMID:19285750

  11. Telomeric transcripts stimulate telomere recombination to suppress senescence in cells lacking telomerase.

    PubMed

    Yu, Tai-Yuan; Kao, Yu-wen; Lin, Jing-Jer

    2014-03-01

    In human somatic cells or yeast cells lacking telomerase, telomeres are shortened upon each cell division. This gradual shortening of telomeres eventually leads to senescence. However, a small population of telomerase-deficient cells can survive by bypassing senescence through the activation of alternative recombination pathways to maintain their telomeres. Although genes involved in telomere recombination have been identified, mechanisms that trigger telomere recombination are less known. The THO (suppressor of the transcriptional defects of Hpr1 mutants by overexpression) complex is involved in transcription elongation and mRNA export. Here we demonstrate that mutations in THO complex components can stimulate early senescence and type II telomere recombination in cells lacking telomerase. The accumulation of telomere-associated noncoding telomere repeat-containing RNA (TERRA) is required for the observed telomere effects in THO complex mutants; reduced transcriptional efficiency, or overexpression of RNase H or C(1-3)A RNA can severely impair the type II telomere recombination. The results highlight a unique function for telomere-associated TERRA, in the formation of type II survivors. Moreover, because TERRA is a long noncoding RNA, these results reveal a function for long noncoding RNA in regulating recombination. PMID:24550456

  12. The Role of Telomere Dysfunction in Driving Genomic Instability

    SciTech Connect

    Robert L Ullrich; Susan Bailey

    2008-01-17

    The mechanistic role of radiation-induced genomic instability in radiation carcinogenesis is an attractive hypothesis that remains to be rigorously tested. There are few in vivo studies on which to base judgments, but work in our laboratory with mouse models of radiogenic mammary neoplasia provided the first indications that certain forms of genetically predisposed radiation-induced genomic instability may contribute to tumor development. The central goal of this research project is to more firmly establish the mechanistic basis of this radiation-associated genomic instability and, from this, to assess whether such induced instability might play a major role in tumorigenesis at low doses of low LET radiation. In the case of mouse mammary tumors, susceptibility to induced instability is expressed as an autosomal recessive trait in mammary epithelial cells and is manifest largely as excess chromatid damage. Recently published studies associate this form of instability with DNA repair deficiency, polymorphic variation in the gene encoding DNA-PKcs (Prkdc), and mammary associated susceptibility. The underlying hypothesis being tested in this project is that tumor-associated genomic instability is preferentially expressed in certain recombinogenic genomic domains and that these may be cell lineage/individual-specific.

  13. Mitochondrial Localization of Telomeric Protein TIN2 Links Telomere Regulation to Metabolic Control

    PubMed Central

    Chen, Liuh-Yow; Zhang, Yi; Zhang, Qinfen; Li, Hongzhi; Luo, Zhenhua; Fang, Hezhi; Kim, Sok Ho; Qin, Li; Yotnda, Patricia; Xu, Jianmin; Tu, Benjamin P.; Bai, Yidong; Songyang, Zhou

    2012-01-01

    Summary Both mitochondria, which are metabolic powerhouses, and telomeres, which help maintain genomic stability, have been implicated in cancer and aging. However, the signaling events that connect these two cellular structures remain poorly understood. Here we report that the canonical telomeric protein TIN2 is also a regulator of metabolism. TIN2 is recruited to telomeres and associates with multiple telomere regulators including TPP1. TPP1 interacts with TIN2 N-terminus, which contains overlapping mitochondrial and telomeric targeting sequences, and controls TIN2 localization. We have found that TIN2 is post-translationally processed in mitochondria, and regulates mitochondria oxidative phosphorylation. Reducing TIN2 expression by RNAi knockdown inhibited glycolysis and reactive oxygen species (ROS) and production, and enhanced ATP levels and oxygen consumption in cancer cells. These results suggest a link between telomeric proteins and metabolic control, providing an additional mechanism by which telomeric proteins regulate cancer and aging. PMID:22885005

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

    PubMed

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

    2015-05-12

    Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants. PMID:25937286

  15. Telomere position effect: regulation of gene expression with progressive telomere shortening over long distances.

    PubMed

    Robin, Jérôme D; Ludlow, Andrew T; Batten, Kimberly; Magdinier, Frédérique; Stadler, Guido; Wagner, Kathyrin R; Shay, Jerry W; Wright, Woodring E

    2014-11-15

    While global chromatin conformation studies are emerging, very little is known about the chromatin conformation of human telomeres. Most studies have focused on the role of telomeres as a tumor suppressor mechanism. Here we describe how telomere length regulates gene expression long before telomeres become short enough to produce a DNA damage response (senescence). We directly mapped the interactions adjacent to specific telomere ends using a Hi-C (chromosome capture followed by high-throughput sequencing) technique modified to enrich for specific genomic regions. We demonstrate that chromosome looping brings the telomere close to genes up to 10 Mb away from the telomere when telomeres are long and that the same loci become separated when telomeres are short. Furthermore, expression array analysis reveals that many loci, including noncoding RNAs, may be regulated by telomere length. We report three genes (ISG15 [interferon-stimulated gene 15 kd], DSP [Desmoplakin], and C1S [complement component 1s subcomplement]) located at three different subtelomeric ends (1p, 6p, and 12p) whose expressions are altered with telomere length. Additionally, we confirmed by in situ analysis (3D-FISH [three-dimensional fluorescence in situ hybridization]) that chromosomal looping occurs between the loci of those genes and their respective telomere ends. We term this process TPE-OLD for "telomere position effect over long distances." Our results suggest a potential novel mechanism for how telomere shortening could contribute to aging and disease initiation/progression in human cells long before the induction of a critical DNA damage response. PMID:25403178

  16. One Identity or More for Telomeres?

    PubMed Central

    Giraud-Panis, Marie-Josèphe; Pisano, Sabrina; Benarroch-Popivker, Delphine; Pei, Bei; Le Du, Marie-Hélène; Gilson, Eric

    2013-01-01

    A major issue in telomere research is to understand how the integrity of chromosome ends is controlled. The fact that different types of nucleoprotein complexes have been described at the telomeres of different organisms raises the question of whether they have in common a structural identity that explains their role in chromosome protection. We will review here how telomeric nucleoprotein complexes are structured, comparing different organisms and trying to link these structures to telomere biology. It emerges that telomeres are formed by a complex and specific network of interactions between DNA, RNA, and proteins. The fact that these interactions and associated activities are reinforcing each other might help to guarantee the robustness of telomeric functions across the cell cycle and in the event of cellular perturbations. We will also discuss the recent notion that telomeres have evolved specific systems to overcome the DNA topological stress generated during their replication and transcription. This will lead to revisit the way we envisage the functioning of telomeric complexes since the regulation of topology is central to DNA stability, replication, recombination, and transcription as well as to chromosome higher-order organization. PMID:23509004

  17. Problem-Solving Test: Telomere Replication

    ERIC Educational Resources Information Center

    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…

  18. Neil3 and NEIL1 DNA Glycosylases Remove Oxidative Damages from Quadruplex DNA and Exhibit Preferences for Lesions in the Telomeric Sequence Context*

    PubMed Central

    Zhou, Jia; Liu, Minmin; Fleming, Aaron M.; Burrows, Cynthia J.; Wallace, Susan S.

    2013-01-01

    The telomeric DNA of vertebrates consists of d(TTAGGG)n tandem repeats, which can form quadruplex DNA structures in vitro and likely in vivo. Despite the fact that the G-rich telomeric DNA is susceptible to oxidation, few biochemical studies of base excision repair in telomeric DNA and quadruplex structures have been done. Here, we show that telomeric DNA containing thymine glycol (Tg), 8-oxo-7,8-dihydroguanine (8-oxoG), guanidinohydantoin (Gh), or spiroiminodihydantoin (Sp) can form quadruplex DNA structures in vitro. We have tested the base excision activities of five mammalian DNA glycosylases (NEIL1, NEIL2, mNeil3, NTH1, and OGG1) on these lesion-containing quadruplex substrates and found that only mNeil3 had excision activity on Tg in quadruplex DNA and that the glycosylase exhibited a strong preference for Tg in the telomeric sequence context. Although Sp and Gh in quadruplex DNA were good substrates for mNeil3 and NEIL1, none of the glycosylases had activity on quadruplex DNA containing 8-oxoG. In addition, NEIL1 but not mNeil3 showed enhanced glycosylase activity on Gh in the telomeric sequence context. These data suggest that one role for Neil3 and NEIL1 is to repair DNA base damages in telomeres in vivo and that Neil3 and Neil1 may function in quadruplex-mediated cellular events, such as gene regulation via removal of damaged bases from quadruplex DNA. PMID:23926102

  19. Telomere Maintenance Mechanisms in Cancer: Clinical Implications

    PubMed Central

    Reddel, Roger R

    2014-01-01

    The presence of immortal cell populations with an up-regulated telomere maintenance mechanism (TMM) is an almost univer-sal characteristic of cancers, whereas normal somatic cells are unable to prevent proliferation-associated telomere shortening and have a limited proliferative potential. TMMs and related aspects of telomere structure and function therefore appear to be ideal targets for the development of anticancer therapeutics. Such treatments would be targeted to a specific cancer-related molecular abnormality, and also be broad-spectrum in that they would be expected to be potentially applicable to most cancers. However, the telomere biology of normal and malignant human cells is a relatively young research field with large numbers of unanswered questions, so the optimal design of TMM-targeted therapeutic approaches remains unclear. This review outlines the opportunities and challenges presented by telomeres and TMMs for clinical management of cancer. PMID:24975603

  20. Association of telomere length and mitochondrial DNA copy number in a community sample of healthy adults.

    PubMed

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

    2015-06-01

    Cellular aging plays a role in longevity and senescence, and has been implicated in medical and psychiatric conditions, including heart disease, cancer, major depression and posttraumatic stress disorder. Telomere shortening and mitochondrial dysfunction are thought to be central to the cellular aging process. The present study examined the association between mitochondrial DNA (mtDNA) copy number and telomere length in a sample of medically healthy adults. Participants (total n=392) were divided into 4 groups based on the presence or absence of early life adversity and lifetime psychopathology: No Adversity/No Disorder, n=136; Adversity/No Disorder, n=91; No Adversity/Disorder, n=46; Adversity/Disorder, n=119. Telomere length and mtDNA copy number were measured using quantitative polymerase chain reaction. There was a positive correlation between mtDNA and telomere length in the entire sample (r=0.120, p<0.001) and in each of the four groups of participants (No Adversity/No Disorder, r=0.291, p=0.001; Adversity/No Disorder r=0.279, p=0.007; No Adversity/Disorder r=0.449, p=0.002; Adversity/Disorder, r=0.558, p<0.001). These correlations remained significant when controlling for age, smoking, and body mass index and establish an association between mtDNA and telomere length in a large group of women and men both with and without early adversity and psychopathology, suggesting co-regulation of telomeres and mitochondrial function. The mechanisms underlying this association may be important in the pathophysiology of age-related medical conditions, such as heart disease and cancer, as well as for stress-associated psychiatric disorders. PMID:25845980

  1. Novel features of telomere biology revealed by the absence of telomeric DNA methylation.

    PubMed

    Vega-Vaquero, Alejandro; Bonora, Giancarlo; Morselli, Marco; Vaquero-Sedas, María I; Rubbi, Liudmilla; Pellegrini, Matteo; Vega-Palas, Miguel A

    2016-08-01

    Cytosine methylation regulates the length and stability of telomeres, which can affect a wide variety of biological features, including cell differentiation, development, or illness. Although it is well established that subtelomeric regions are methylated, the presence of methylated cytosines at telomeres has remained controversial. Here, we have analyzed multiple bisulfite sequencing studies to address the methylation status of Arabidopsis thaliana telomeres. We found that the levels of estimated telomeric DNA methylation varied among studies. Interestingly, we estimated higher levels of telomeric DNA methylation in studies that produced C-rich telomeric strands with lower efficiency. However, these high methylation estimates arose due to experimental limitations of the bisulfite technique. We found a similar phenomenon for mitochondrial DNA: The levels of mitochondrial DNA methylation detected were higher in experiments with lower mitochondrial read production efficiencies. Based on experiments with high telomeric C-rich strand production efficiencies, we concluded that Arabidopsis telomeres are not methylated, which was confirmed by methylation-dependent restriction enzyme analyses. Thus, our studies indicate that telomeres are refractory to de novo DNA methylation by the RNA-directed DNA methylation machinery. This result, together with previously reported data, reveals that subtelomeric DNA methylation controls the homeostasis of telomere length. PMID:27405804

  2. Yeast telomeres exert a position effect on recombination between internal tracts of yeast telomeric DNA

    PubMed Central

    Stavenhagen, Jeffrey B.; Zakian, Virginia A.

    1998-01-01

    In Saccharomyces cerevisiae, proximity to a telomere affects both transcription and replication of adjacent DNA. In this study, we show that telomeres also impose a position effect on mitotic recombination. The rate of recombination between directly repeated tracts of telomeric C1–3A/TG1–3 DNA was reduced severely by proximity to a telomere. In contrast, recombination of two control substrates was not affected by telomere proximity. Thus, unlike position effects on transcription or replication, inhibition of recombination was sequence specific. Moreover, the repression of recombination was not under the same control as transcriptional repression (telomere position effect; TPE), as mutations in genes essential for TPE did not alleviate telomeric repression of recombination. The reduction in recombination between C1–3A/TG1–3 tracts near the telomere was caused by an absence of Rad52p-dependent events as well as a reduction in Rad1p-dependent events. The sequence-specific repression of recombination near the telomere was eliminated in cells that overexpressed the telomere-binding protein Rap1p, a condition that also increased recombination between C1–3A/TG1–3 tracts at internal positions on the chromosome. We propose that the specific inhibition between C1–3A/TG1–3 tracts near the telomere occurs through the action of a telomere-specific end-binding protein that binds to the single-strand TG1–3 tail generated during the processing of recombination intermediates. The recombination inhibitor protein may also block recombination between endogenous telomeres. PMID:9765206

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

    SciTech Connect

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

    2005-01-01

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

  4. TPP1 Blocks an ATR-Mediated Resection Mechanism at Telomeres.

    PubMed

    Kibe, Tatsuya; Zimmermann, Michal; de Lange, Titia

    2016-01-21

    The regulation of 5' end resection at DSBs and telomeres prevents genome instability. DSB resection is positively and negatively regulated by ATM signaling through CtIP/MRN and 53BP1-bound Rif1, respectively. Similarly, telomeres lacking TRF2 undergo ATM-controlled CtIP-dependent hyper-resection when the repression by 53BP1/Rif1 is alleviated. However, telomere resection in the absence of 53BP1/Rif1 is more extensive upon complete removal of shelterin, indicating additional protection against resection by shelterin. Here we show that TPP1 and POT1a/b in shelterin block a resection pathway distinct from that repressed by TRF2. This second pathway is regulated by ATR signaling, involves Exo1 and BLM, and is inhibited by 53BP1/Rif1. Thus, mammalian cells have two distinct 5' end-resection pathways that are regulated by DNA damage signaling, in part through Rif1-mediated inhibition. The data show that telomeres are protected from hyper-resection through the repression of the ATM and ATR kinases by TRF2 and TPP1-bound POT1a/b, respectively. PMID:26778124

  5. Two retrotransposons maintain telomeres in Drosophila

    PubMed Central

    Pardue, M.-L.; Rashkova, S.; Casacuberta, E.; DeBaryshe, P.G.; George, J. A.; Traverse, K.L.

    2005-01-01

    Telomeres across the genus Drosophila are maintained, not by telomerase, but by two non-LTR retrotransposons, HeT-A and TART, that transpose specifically to chromosome ends. Successive transpositions result in long head-to-tail arrays of these elements. Thus Drosophila telomeres, like those produced by telomerase, consist of repeated sequences reverse transcribed from RNA templates. The Drosophila repeats, complete and 5′-truncated copies of HeT-A and TART, are more complex than telomerase repeats; nevertheless these evolutionary variants have functional similarities to the more common telomeres. Like other telomeres, the Drosophila arrays are dynamic, fluctuating around an average length that can be changed by changes in the genetic background. Several proteins that interact with telomeres in other species have been found to have homologues that interact with Drosophila telomeres. Although they have hallmarks of non-LTR retrotransposons, HeT-A and TART appear to have a special relationship to Drosophila. Their Gag proteins are efficiently transported into diploid nuclei where HeT-A Gag recruits TART Gag to chromosome ends. Gags of other non-LTR elements remain predominantly in the cytoplasm. These studies provide intriguing evolutionary links between telomeres and retrotransposable elements. PMID:16132810

  6. Increased expression of telomere-regulating genes in endurance athletes with long leukocyte telomeres.

    PubMed

    Denham, Joshua; O'Brien, Brendan J; Prestes, Priscilla R; Brown, Nicholas J; Charchar, Fadi J

    2016-01-15

    Leukocyte telomeres shorten with age, and excessive shortening is associated with age-related cardiometabolic diseases. Exercise training may prevent disease through telomere length maintenance although the optimal amount of exercise that attenuates telomere attrition is unknown. Furthermore, the underlying molecular mechanisms responsible for the enhanced telomere maintenance observed in endurance athletes is poorly understood. We quantified the leukocyte telomere length and analyzed the expression of telomere-regulating genes in endurance athletes and healthy controls (both n = 61), using quantitative PCR. We found endurance athletes have significantly longer (7.1%, 208-416 nt) leukocyte telomeres and upregulated TERT (2.0-fold) and TPP1 (1.3-fold) mRNA expression compared with controls in age-adjusted analysis. The telomere length and telomere-regulating gene expression differences were no longer statistically significant after adjustment for resting heart rate and relative V̇O(2 max) (all P > 0.05). Resting heart rate emerged as an independent predictor of leukocyte telomere length and TERT and TPP1 mRNA expression in stepwise regression models. To gauge whether volume of exercise was associated with leukocyte telomere length, we divided subjects into running and cycling tertiles (distance covered per week) and found individuals in the middle and highest tertiles had longer telomeres than individuals in the lowest tertile. These data emphasize the importance of cardiorespiratory fitness and exercise training in the prevention of biological aging. They also support the concept that moderate amounts of exercise training protects against biological aging, while higher amounts may not elicit additional benefits. PMID:26586905

  7. MAD2L2 controls DNA repair at telomeres and DNA breaks by inhibiting 5′ end-resection

    PubMed Central

    Segura-Bayona, Sandra; Peuscher, Marieke H.; van der Torre, Jaco; Wevers, Brigitte A.; Orthwein, Alexandre; Durocher, Daniel; Jacobs, Jacqueline J.L.

    2015-01-01

    Appropriate repair of DNA lesions and the inhibition of DNA repair activities at telomeres are critical to prevent genomic instability. By fuelling the generation of genetic alterations and by compromising cell viability, genomic instability is a driving force in cancer and aging1, 2. Here we identify MAD2L2 (also known as MAD2B or REV7) through functional genetic screening as a novel factor controlling DNA repair activities at mammalian telomeres. We show that MAD2L2 accumulates at uncapped telomeres and promotes non-homologous end-joining (NHEJ)-mediated fusion of deprotected chromosome ends and genomic instability. MAD2L2 depletion causes elongated 3′ telomeric overhangs, implying that MAD2L2 inhibits 5′ end-resection. End-resection blocks NHEJ while committing to homology-directed repair (HDR) and is under control of 53BP1, RIF1 and PTIP3. Consistent with MAD2L2 promoting NHEJ-mediated telomere fusion by inhibiting 5′ end-resection, knockdown of the nucleases CTIP or EXO1 partially restores telomere-driven genomic instability in MAD2L2-depleted cells. Control of DNA repair by MAD2L2 is not limited to telomeres. MAD2L2 also accumulates and inhibits end-resection at irradiation (IR)-induced DNA double-strand breaks (DSBs) and promotes end-joining of DSBs in multiple settings, including during immunoglobulin class switch recombination (CSR). These activities of MAD2L2 depend on ATM kinase activity, RNF8, RNF168, 53BP1 and RIF1, but not on PTIP, REV1 and REV3, the latter two acting with MAD2L2 in translesion synthesis (TLS)4. Together our data establish MAD2L2 as a critical contributor to the control of DNA repair activity by 53BP1 that promotes NHEJ by inhibiting 5′ end-resection downstream of RIF1. PMID:25799990

  8. Mte1 interacts with Mph1 and promotes crossover recombination and telomere maintenance.

    PubMed

    Silva, Sonia; Altmannova, Veronika; Luke-Glaser, Sarah; Henriksen, Peter; Gallina, Irene; Yang, Xuejiao; Choudhary, Chunaram; Luke, Brian; Krejci, Lumir; Lisby, Michael

    2016-03-15

    Mph1 is a member of the conserved FANCM family of DNA motor proteins that play key roles in genome maintenance processes underlying Fanconi anemia, a cancer predisposition syndrome in humans. Here, we identify Mte1 as a novel interactor of the Mph1 helicase in Saccharomyces cerevisiae. In vitro, Mte1 (Mph1-associated telomere maintenance protein 1) binds directly to DNA with a preference for branched molecules such as D loops and fork structures. In addition, Mte1 stimulates the helicase and fork regression activities of Mph1 while inhibiting the ability of Mph1 to dissociate recombination intermediates. Deletion of MTE1 reduces crossover recombination and suppresses the sensitivity of mph1Δ mutant cells to replication stress. Mph1 and Mte1 interdependently colocalize at DNA damage-induced foci and dysfunctional telomeres, and MTE1 deletion results in elongated telomeres. Taken together, our data indicate that Mte1 plays a role in regulation of crossover recombination, response to replication stress, and telomere maintenance. PMID:26966248

  9. Exome Sequencing Links Mutations in PARN and RTEL1 with Familial Pulmonary Fibrosis and Telomere Shortening

    PubMed Central

    Stuart, Bridget D.; Choi, Jungmin; Zaidi, Samir; Xing, Chao; Holohan, Brody; Chen, Rui; Choi, Mihwa; Dharwadkar, Pooja; Torres, Fernando; Girod, Carlos E.; Weissler, Jonathan; Fitzgerald, John; Kershaw, Corey; Klesney-Tait, Julia; Mageto, Yolanda; Shay, Jerry W.; Ji, Weizhen; Bilguvar, Kaya; Mane, Shrikant; Lifton, Richard P.; Garcia, Christine Kim

    2015-01-01

    Idiopathic pulmonary fibrosis (IPF) is an age-related disease featuring progressive lung scarring. To elucidate the molecular basis of IPF, we performed exome sequencing of familial pulmonary fibrosis kindreds. Gene burden analysis comparing 78 European cases and 2,816 controls implicated PARN, an exoribonuclease with no prior connection to telomere biology or disease, with five novel heterozygous damaging mutations in unrelated cases and none in controls (P-value = 1.3 × 10−8); mutations were shared by all affected relatives (odds in favor of linkage = 4,096:1). RTEL1, an established locus for dyskeratosis congenita, harbored significantly more novel damaging and missense variants at conserved residues in cases than controls (P = 1.6 × 10−6). PARN and RTEL1 mutation carriers had shortened leukocyte telomere lengths and epigenetic inheritance of short telomeres was seen in family members. Together these genes explain ~7% of familial pulmonary fibrosis and strengthen the link between lung fibrosis and telomere dysfunction. PMID:25848748

  10. Allium telomeres unmasked: the unusual telomeric sequence (CTCGGTTATGGG)n is synthesized by telomerase.

    PubMed

    Fajkus, Petr; Peška, Vratislav; Sitová, Zdeňka; Fulnečková, Jana; Dvořáčková, Martina; Gogela, Roman; Sýkorová, Eva; Hapala, Jan; Fajkus, Jiří

    2016-02-01

    Phylogenetic divergence in Asparagales plants is associated with switches in telomere sequences. The last switch occurred with divergence of the genus Allium (Amaryllidaceae) from the other Allioideae (formerly Alliaceae) genera, resulting in uncharacterized telomeres maintained by an unknown mechanism. To characterize the unknown Allium telomeres, we applied a combination of bioinformatic processing of transcriptomic and genomic data with standard approaches in telomere biology such as BAL31 sensitivity tests, terminal restriction fragment analysis, the telomere repeat amplification protocol (TRAP), and fluorescence in situ hybridization (FISH). Using these methods, we characterize the unusual telomeric sequence (CTCGGTTATGGG)n present in Allium species, demonstrate its synthesis by telomerase, and characterize the telomerase reverse transcriptase (TERT) subunit of Allium cepa. Our findings open up the possibility of studying the molecular details of the evolutionary genetic change in Allium telomeres and its possible role in speciation. Experimental studies addressing the implications of this change in terms of the interplay of telomere components may now be designed to shed more light on telomere functions and evolution in general. PMID:26716914

  11. Significant correlation of species longevity with DNA double strand break recognition but not with telomere length.

    PubMed

    Lorenzini, Antonello; Johnson, F Brad; Oliver, Anthony; Tresini, Maria; Smith, Jasmine S; Hdeib, Mona; Sell, Christian; Cristofalo, Vincent J; Stamato, Thomas D

    2009-01-01

    The identification of the cellular mechanisms responsible for the wide differences in species lifespan remains one of the major unsolved problems of the biology of aging. We measured the capacity of nuclear protein to recognize DNA double strand breaks (DSBs) and telomere length of skin fibroblasts derived from mammalian species that exhibit wide differences in longevity. Our results indicate DNA DSB recognition increases exponentially with longevity. Further, an analysis of the level of Ku80 protein in human, cow, and mouse suggests that Ku levels vary dramatically between species and these levels are strongly correlated with longevity. In contrast mean telomere length appears to decrease with increasing longevity of the species, although not significantly. These findings suggest that an enhanced ability to bind to DNA ends may be important for longevity. A number of possible roles for increased levels of Ku and DNA-PKcs are discussed. PMID:19896964

  12. Mammalian sleep

    NASA Astrophysics Data System (ADS)

    Staunton, Hugh

    2005-05-01

    This review examines the biological background to the development of ideas on rapid eye movement sleep (REM sleep), so-called paradoxical sleep (PS), and its relation to dreaming. Aspects of the phenomenon which are discussed include physiological changes and their anatomical location, the effects of total and selective sleep deprivation in the human and animal, and REM sleep behavior disorder, the latter with its clinical manifestations in the human. Although dreaming also occurs in other sleep phases (non-REM or NREM sleep), in the human, there is a contingent relation between REM sleep and dreaming. Thus, REM is taken as a marker for dreaming and as REM is distributed ubiquitously throughout the mammalian class, it is suggested that other mammals also dream. It is suggested that the overall function of REM sleep/dreaming is more important than the content of the individual dream; its function is to place the dreamer protagonist/observer on the topographical world. This has importance for the developing infant who needs to develop a sense of self and separateness from the world which it requires to navigate and from which it is separated for long periods in sleep. Dreaming may also serve to maintain a sense of ‘I’ness or “self” in the adult, in whom a fragility of this faculty is revealed in neurological disorders.

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

    PubMed

    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. PMID:26450775

  14. Progressive cis-inhibition of telomerase upon telomere elongation.

    PubMed Central

    Marcand, S; Brevet, V; Gilson, E

    1999-01-01

    In yeast, the constant length of telomeric DNA results from a negative regulation of telomerase by the telomere itself. Here we follow the return to equilibrium of an abnormally shortened telomere. We observe that telomere elongation is restricted to a few base pairs per generation and that its rate decreases progressively with increasing telomere length. In contrast, in the absence of telomerase or in the presence of an over-elongated telomere, the degradation rate linked to the succession of generations appears to be constant, i.e. independent of telomere length. Together, these results indicate that telomerase is gradually inhibited at its site of action by the elongating telomere. The implications of this finding for the dynamics of telomere length regulation are discussed in this study. PMID:10369690

  15. Maternal telomere length inheritance in the king penguin

    PubMed Central

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

    2015-01-01

    Telomeres are emerging as a biomarker for ageing and survival, and are likely important in shaping life-history trade-offs. In particular, telomere length with which one starts in life has been linked to lifelong survival, suggesting that early telomere dynamics are somehow related to life-history trajectories. This result highlights the importance of determining the extent to which telomere length is inherited, as a crucial factor determining early life telomere length. Given the scarcity of species for which telomere length inheritance has been studied, it is pressing to assess the generality of telomere length inheritance patterns. Further, information on how this pattern changes over the course of growth in individuals living under natural conditions should provide some insight on the extent to which environmental constraints also shape telomere dynamics. To fill this gap partly, we followed telomere inheritance in a population of king penguins (Aptenodytes patagonicus). We tested for paternal and maternal influence on chick initial telomere length (10 days old after hatching), and how these relationships changed with chick age (at 70, 200 and 300 days old). Based on a correlative approach, offspring telomere length was positively associated with maternal telomere length early in life (at 10 days old). However, this relationship was not significant at older ages. These data suggest that telomere length in birds is maternally inherited. Nonetheless, the influence of environmental conditions during growth remained an important factor shaping telomere length, as the maternal link disappeared with chicks' age. PMID:25052413

  16. Telomere Shortening and Associated Chromosomal Instability in Peripheral Blood Lymphocytes of Patients With Hodgkin's Lymphoma Prior to Any Treatment Are Predictive of Second Cancers

    SciTech Connect

    M'kacher, Radhia . E-mail: mkacher@igr.fr; Bennaceur-Griscelli, Annelise; Girinsky, Theodore; Koscielny, Serge; Delhommeau, Francois; Dossou, Julien; Violot, Dominique; Leclercq, Evelyne; Courtier, Marie Helene; Beron-Gaillard, Nadine; Assaf, Elias; Ribrag, Vincent; Carde, Patrice; Bourhis, Jean |; Feneux, Daniele; Bernheim, Alain; Parmentier, Claude

    2007-06-01

    Purpose: To investigate a potential link between telomere length, chromosomal instability, and the advent of a second cancer (SC) in patients with Hodgkin's lymphoma (HL), who are known to be at risk for SCs. This study was premised on the finding that telomere dysfunction and DNA repair pathways were related to many pathologic conditions. Methods and Materials: Three cohorts of patients with HL were studied: 73 who were prospectively followed >5 years after diagnosis (prospective HL cohort), 28 who developed a SC (SC HL cohort), and 18 long-term survivors with no evidence of disease or complication since their initial treatment (NED HL cohort). Telomere length was analyzed by a telomeric restriction fragment assay in peripheral blood lymphocytes. Thirty healthy donors and 70 patients with a newly diagnosed solid tumor were the control population. Results: Compared with controls, patients from the prospective HL cohort, before any treatment, showed age-independent shorter telomeres (mean, 8.3 vs. 11.7 kb in healthy donors; <6 kb in 18% in HL patients), increased spontaneous chromosomal abnormalities, and increased in vitro radiation sensitivity (p < 10{sup -4} each). After treatment, telomere shortening was associated with cytogenetic profiles characterized by the persistence of complex chromosomal rearrangement and clonal aberrations. Moreover, the two cases of SC in the prospective HL patients had short telomeres and CCR initially. In addition, the SC HL cohort was characterized by markedly short telomeres (6.6 vs. 9.7 kb in the NED HL cohort), the presence of complex chromosome rearrangements, and increased in vitro radiation sensitivity. Conclusions: An intimate relationship between pre-treatment telomere shortening, chromosomal instability, radiation sensitivity and occurrence of SC was found in HL patients.

  17. The telomere bouquet regulates meiotic centromere assembly.

    PubMed

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

    2015-04-01

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

  18. Mammalian aromatases.

    PubMed

    Conley, A; Hinshelwood, M

    2001-05-01

    Aromatase is the enzyme complex that catalyses the synthesis of oestrogens from androgens, and therefore it has unique potential to influence the physiological balance between the sex steroid hormones. Both aromatase cytochrome P450 (P450arom) and NADPH-cytochrome P450 reductase (reductase), the two essential components of the enzyme complex, are highly conserved among mammals and vertebrates. Aromatase expression occurs in the gonads and brain, and is essential for reproductive development and fertility. Of interest are the complex mechanisms involving alternative promoter utilization that have evolved to control tissue-specific expression in these tissues. In addition, in a number of species, including humans, expression of aromatase has a broader tissue distribution, including placenta, adipose and bone. The relevance of oestrogen synthesis and possibly androgen metabolism in these peripheral sites of expression is now becoming clear from studies in P450arom knockout (ArKO) mice and from genetic defects recognized recently in both men and women. Important species differences in the physiological roles of aromatase expression are also likely to emerge, despite the highly conserved nature of the enzyme system. The identification of functionally distinct, tissue-specific isozymes of P450arom in at least one mammal, pigs, and several species of fish indicates that there are additional subtle, but physiologically significant, species-specific roles for aromatase. Comparative studies of mammalian and other vertebrate aromatases will expand understanding of the role played by this ancient enzyme system in the evolution of reproduction and the adaptive influence of oestrogen synthesis on general health and well being. PMID:11427156

  19. [Enhanced control of proliferation in telomerized cells].

    PubMed

    Egorov, E E; Moldaver, M V; Vishniakova, Kh S; Terekhov, S M; Dashinimaev, E B; Cheglakov, I B; Toropygin, I Iu; Iarygin, K N; Chumakov, P M; Korochkin, L I; Antonova, G A; Rybalkina, E Iu; Saburina, I N; Burnaevskiĭ, N S; Zelenin, A V

    2007-01-01

    Clones of telomerized fibroblasts of adult human skin have earlier been obtained. It was shown that despite their fast growth in mass cultures, these cells poorly form colonies. Conditioned medium, antioxidants, and reduced partial oxygen pressure enhanced their colony formation, but not to the level characteristic of the initial cells. The conditioned medium of telomerized cells enhanced colony formation to a much greater extent than that of the initial cells. A study of proteome of the telomerized fibroblasts has revealed changes in the activities of tens of genes. A general trend consists in weakening and increased lability of the cytoskeleton and in activation of the mechanisms controlling protein degradation. However, these changes are not very pronounced. During the formation of immortal telomerized cells, selection takes place, which appears to determine changes in the expression of some genes. It was proposed that a decrease in the capacity of telomerized cells for colony formation is due to increased requirements of these cells to cell-cell contacts. The rate of cell growth reached that characteristic of mass cultures only in the largest colonies. In this respect, the telomerized fibroblasts resembled stem cells: they are capable of self-maintenance, but "escape" to differentiation in the absence of the corresponding microenvironment (niche), which is represented by other fibroblasts. Non-dividing cells in the test of colony formation should be regarded as differentiated cells, since they have no features of degradation, preserve their viability, actively move, grow, phagocytized debris, etc. It was also shown that telomerization did not prevent differentiation of myoblasts and human neural stem cells. Thus, the results obtained suggest the existence of normal mechanisms underlying the regulation of proliferation in the telomerized cells, which opens possibilities of their use in cell therapy, especially in the case of autotransplantation to senior people

  20. Plant telomeres and telomerases. A review.

    PubMed

    McKnight, T D; Fitzgerald, M S; Shippen, D E

    1997-11-01

    Barbara McClintock began investigating plant telomeres during the 1930s, but little additional work was done in this area until a telomeric DNA sequence was isolated and characterized from Arabidopsis thaliana in 1988. This sequence, a simple repeat of the heptanucleotide 5'-TTTAGGG-3', has been found in telomeres of almost all plants analyzed. Telomere length in plants, which can be a long as 75 kb or as short as 2 kb, is controlled by both genetic and developmental factors. The major mechanism for synthesis of telomeres is telomerase, a ribonucleoprotein with reverse transcriptase activity. Telomerase expression is highly regulated in both plants and animals. For example, there is little or no detectable expression of telomerase in most vegetative tissues of plants nor in most somatic tissues of animals. In contrast to animals, plants do not specify a germ line until late in development, but telomerase is reactivated during flowering, possibly to ensure that gametes and embryos arising from them inherit fully functional chromosomes. Telomerase is also highly expressed in plant tissue culture cells, as might be expected for cells with an unlimited capacity for proliferation. Despite recent progress in investigating plant telomeres and telomerase at the molecular level, there is still much more to learn, especially concerning the developmental control of telomerase activity. PMID:9467846

  1. Telomere--the twilight to immortality.

    PubMed

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

    2010-09-01

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

  2. Telomeres, NAFLD and Chronic Liver Disease

    PubMed Central

    Donati, Benedetta; Valenti, Luca

    2016-01-01

    Telomeres consist of repeat DNA sequences located at the terminal portion of chromosomes that shorten during mitosis, protecting the tips of chromosomes. During chronic degenerative conditions associated with high cell replication rate, progressive telomere attrition is accentuated, favoring senescence and genomic instability. Several lines of evidence suggest that this process is involved in liver disease progression: (a) telomere shortening and alterations in the expression of proteins protecting the telomere are associated with cirrhosis and hepatocellular carcinoma; (b) advanced liver damage is a feature of a spectrum of genetic diseases impairing telomere function, and inactivating germline mutations in the telomerase complex (including human Telomerase Reverse Transcriptase (hTERT) and human Telomerase RNA Component (hTERC)) are enriched in cirrhotic patients independently of the etiology; and (c) experimental models suggest that telomerase protects from liver fibrosis progression. Conversely, reactivation of telomerase occurs during hepatocarcinogenesis, allowing the immortalization of the neoplastic clone. The role of telomere attrition may be particularly relevant in the progression of nonalcoholic fatty liver, an emerging cause of advanced liver disease. Modulation of telomerase or shelterins may be exploited to prevent liver disease progression, and to define specific treatments for different stages of liver disease. PMID:26999107

  3. Conventional anticancer therapeutics and telomere maintenance mechanisms.

    PubMed

    Uziel, Orit; Lahav, Meir

    2014-01-01

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

  4. Telomeres, NAFLD and Chronic Liver Disease.

    PubMed

    Donati, Benedetta; Valenti, Luca

    2016-01-01

    Telomeres consist of repeat DNA sequences located at the terminal portion of chromosomes that shorten during mitosis, protecting the tips of chromosomes. During chronic degenerative conditions associated with high cell replication rate, progressive telomere attrition is accentuated, favoring senescence and genomic instability. Several lines of evidence suggest that this process is involved in liver disease progression: (a) telomere shortening and alterations in the expression of proteins protecting the telomere are associated with cirrhosis and hepatocellular carcinoma; (b) advanced liver damage is a feature of a spectrum of genetic diseases impairing telomere function, and inactivating germline mutations in the telomerase complex (including human Telomerase Reverse Transcriptase (hTERT) and human Telomerase RNA Component (hTERC)) are enriched in cirrhotic patients independently of the etiology; and (c) experimental models suggest that telomerase protects from liver fibrosis progression. Conversely, reactivation of telomerase occurs during hepatocarcinogenesis, allowing the immortalization of the neoplastic clone. The role of telomere attrition may be particularly relevant in the progression of nonalcoholic fatty liver, an emerging cause of advanced liver disease. Modulation of telomerase or shelterins may be exploited to prevent liver disease progression, and to define specific treatments for different stages of liver disease. PMID:26999107

  5. Centrosome aberrations in human mammary epithelial cells driven by cooperative interactions between p16INK4a deficiency and telomere-dependent genotoxic stress

    PubMed Central

    Domínguez, Daniel; Feijoo, Purificación; Bernal, Aina; Ercilla, Amaia; Agell, Neus; Genescà, Anna; Tusell, Laura

    2015-01-01

    Virtually all human cancers display chromosome instability (CIN), a condition in which chromosomes are gained or lost at a high rate. CIN occurs early in cancer development where it may undermine the advance of the neoplastic disease. With the aim of establishing the mechanisms underlying CIN in cancer, we investigated possible links between telomere-dysfunction and centrosome defects, which were seen to coincide in early in breast carcinogenesis using human mammary epithelial cells (HMECs). In this study, we show that TP53 proficient vHMECs cells develop centrosome aberrations when telomere-dysfunction genotoxic stress is produced in the presence of a defective p16INK4a setting and in parallel with an activation of the DNA damage checkpoint response. These aberrations consist of the accumulation of centrosomes in polyploid vHMECs, plus centriole overduplication in both diploid and polyploid cells, thus reflecting that distinct mechanisms underlie the generation of centrosome aberrations in vHMECs. Transduction of vHMEC with hTERT, which rescued the telomere dysfunction phenotype and consequently reduced DNA damage checkpoint activation, led to a progressive reduction of centrosome aberrations with cell culture, both in diploid and in polyploid vHMECs. Radiation-induced DNA damage also raised centrosome aberrations in vHMEC-hTERT. Collectively, our results, using vHMECs define a model where p16INK4a deficiency along with short dysfunctional telomeres cooperatively engenders centrosome abnormalities before p53 function is compromised. PMID:26318587

  6. Ku suppresses formation of telomeric circles and alternative telomere lengthening in Arabidopsis.

    PubMed

    Zellinger, Barbara; Akimcheva, Svetlana; Puizina, Jasna; Schirato, Martina; Riha, Karel

    2007-07-01

    Telomeres in mammals and plants are protected by the terminal t loop structure, the formation of which parallels the first steps of intrachromatid homologous recombination (HR). Under some circumstances, cells can also utilize an HR-based mechanism (alternative lengthening of telomeres [ALT]) as a back-up pathway for telomere maintenance. We have found that the Ku70/80 heterodimer, a central nonhomologous end-joining DNA repair factor, inhibits engagement of ALT in Arabidopsis telomerase-negative cells. To further assess HR activities at telomeres, we have developed a sensitive assay for detecting extrachromosomal telomeric circles (t circles) that may arise from t loop resolution and aberrant HR. We show that Ku70/80 specifically inhibits circle formation at telomeres, but not at centromeric and rDNA repeats. Ku inactivation results in increased formation of t circles that represent approximately 4% of total telomeric DNA. However, telomeres in ku mutants are fully functional, indicating that telomerase efficiently heals ongoing terminal deletions arising from excision of the t circles. PMID:17612498

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-05-19

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

  9. Molecular basis of telomere syndrome caused by CTC1 mutations

    PubMed Central

    Chen, Liuh-Yow; Majerská, Jana; Lingner, Joachim

    2013-01-01

    Mutations in CTC1 lead to the telomere syndromes Coats Plus and dyskeratosis congenita (DC), but the molecular mechanisms involved remain unknown. CTC1 forms with STN1 and TEN1 a trimeric complex termed CST, which binds ssDNA, promotes telomere DNA synthesis, and inhibits telomerase-mediated telomere elongation. Here we identify CTC1 disease mutations that disrupt CST complex formation, the physical interaction with DNA polymerase α-primase (polα-primase), telomeric ssDNA binding in vitro, accumulation in the nucleus, and/or telomere association in vivo. While having diverse molecular defects, CTC1 mutations commonly lead to the accumulation of internal single-stranded gaps of telomeric DNA, suggesting telomere DNA replication defects as a primary cause of the disease. Strikingly, mutations in CTC1 may also unleash telomerase repression and telomere length control. Hence, the telomere defect initiated by CTC1 mutations is distinct from the telomerase insufficiencies seen in classical forms of telomere syndromes, which cause short telomeres due to reduced maintenance of distal telomeric ends by telomerase. Our analysis provides molecular evidence that CST collaborates with DNA polα-primase to promote faithful telomere DNA replication. PMID:24115768

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

    PubMed Central

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

    2014-01-01

    The telomere structure in the Iberian shrew Sorex granarius is characterized by unique, striking features, with short arms of acrocentric chromosomes carrying extremely long telomeres (up to 300 kb) with interspersed ribosomal DNA (rDNA) repeat blocks. In this work, we investigated the telomere physiology of S. granarius fibroblast cells and found that telomere repeats are transcribed on both strands and that there is no telomere-dependent senescence mechanism. Although telomerase activity is detectable throughout cell culture and appears to act on both short and long telomeres, we also discovered that signatures of a recombinogenic activity are omnipresent, including telomere-sister chromatid exchanges, formation of alternative lengthening of telomeres (ALT)-associated PML-like bodies, production of telomere circles, and a high frequency of telomeres carrying marks of a DNA damage response. Our results suggest that recombination participates in the maintenance of the very long telomeres in normal S. granarius fibroblasts. We discuss the possible interplay between the interspersed telomere and rDNA repeats in the stabilization of the very long telomeres in this organism. PMID:24842907

  11. Diastolic Dysfunction

    PubMed Central

    Jeong, Euy-Myoung; Dudley, Samuel C.

    2016-01-01

    Despite the growing number of patients affected, the understanding of diastolic dysfunction and heart failure with preserved ejection fraction (HFpEF) is still poor. Clinical trials, largely based on successful treatments for systolic heart failure, have been disappointing, suggesting that HFpEF has a different pathology to that of systolic dysfunction. In this review, general concepts, epidemiology, diagnosis, and treatment of diastolic dysfunction are summarized, with an emphasis on new experiments suggesting that oxidative stress plays a crucial role in the pathogenesis of at least some forms of the disease. This observation has lead to potential new diagnostics and therapeutics for diastolic dysfunction and heart failure caused by diastolic dysfunction. PMID:25746522

  12. Origin of human chromosome 2: An ancestral telomere-telomere fusion

    SciTech Connect

    Ijdo, J.W.; Baldini, A.; Ward, D.C.; Reeders, S.T.; Wells, R.A. )

    1991-10-15

    The authors identified two allelic genomic cosmids from human chromosome 2, c8.1 and c29B, each containing two inverted arrays of the vertebrate telomeric repeat in a head-to-head arrangement, 5{prime}(TTAGGG){sub n}-(CCCTAA){sub m}3{prime}. Sequences flanking this telomeric repeat are characteristic of present-day human pretelomeres. BAL-31 nuclease experiments with yeast artificial chromosome clones of human telomeres and fluorescence in situ hybridization reveal that sequences flanking these inverted repeats hybridize both to band 2q13 and to different, but overlapping, subsets of human chromosome ends. They conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2.

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

    SciTech Connect

    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.

  14. Remarkable interference with telomeric function by a G-quadruplex selective bisantrene regioisomer.

    PubMed

    Folini, Marco; Pivetta, Claudia; Zagotto, Giuseppe; De Marco, Cinzia; Palumbo, Manlio; Zaffaroni, Nadia; Sissi, Claudia

    2010-06-15

    The use of small molecules able to induce and stabilize selected G-quadruplex arrangements can cause telomerase inhibition and telomere dysfunction in cancer cells, thus providing very selective therapeutic approaches. Effective stabilizers usually comprise a planar aromatic portion to grant effective stacking onto the G-quartet and positively charged side chains to exploit the highly negative charge density on the quadruplex grooves. Since the relative position of these two pharmacophoric moieties is expected to play an important role in DNA folding stabilization, we evaluated a series of anthracene derivatives substituted with one or two 4,5-dihydro-1H-imidazol-2-yl-hydrazonic groups (the bisantrene side chain) at different positions of the aromatic system. Indeed, the various regioisomers showed distinct binding affinities for telomeric G-quadruplex, and the most effective was the 1,5 and 1,7 bis-substituted analogues. On turn, the 1,8 regioisomer was poorly effective. Interestingly, G-quadruplex binding is clearly related to telomerase inhibition in this class of compounds, thus confirming their ability to shift the nucleic acid conformational equilibrium upon binding and consequently produce interference with the telomere processing enzyme. Additionally, the 1,5 regioisomer was shown to inhibit telomerase activity at lower concentrations than those required to reduce tumor cell proliferation. Comparative analysis of drug effects in telomerase-positive and telomerase-negative cancer cells showed consistent cell growth impairment, as a consequence of activation of the senescence pathway, which was mainly attributable to anthracene-mediated telomere dysfunction. PMID:20206144

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

    PubMed

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

    2012-01-01

    Telomeres, specialised structures that protect chromosome ends, play a critical role in preserving chromosome integrity. Telomere dynamics in the Tasmanian devil (Sarcophilus harrisii) are of particular interest in light of the emergence of devil facial tumour disease (DFTD), a transmissible malignancy that causes rapid mortality and threatens the species with extinction. We used fluorescent in situ hybridisation to investigate telomere length in DFTD cells, in healthy Tasmanian devils and in four closely related marsupial species. Here we report that animals in the Order Dasyuromorphia have chromosomes characterised by striking telomere length dimorphism between homologues. Findings in sex chromosomes suggest that telomere length dimorphism may be regulated by events in the parental germlines. Long telomeres on the Y chromosome imply that telomere lengthening occurs during spermatogenesis, whereas telomere diminution occurs during oogenesis. Although found in several somatic cell tissue types, telomere length dimorphism was not found in DFTD cancer cells, which are characterised by uniformly short telomeres. This is, to our knowledge, the first report of naturally occurring telomere length dimorphism in any species and suggests a novel strategy of telomere length control. Comparative studies in five distantly related marsupials and a monotreme indicate that telomere dimorphism evolved at least 50 million years ago. PMID:23049977

  16. Rap1p telomere association is not required for mitotic stability of a C3TA2 telomere in yeast

    PubMed Central

    Alexander, Mary Kate; Zakian, Virginia A.

    2003-01-01

    Telomeric DNA usually consists of a repetitive sequence: C1–3A/TG1–3 in yeast, and C3TA2/T2AG3 in vertebrates. In yeast, the sequence-specific DNA- binding protein Rap1p is thought to be essential for telomere function. In a tlc1h mutant, the templating region of the telomerase RNA gene is altered so that telomerase adds the vertebrate telomere sequence instead of the yeast sequence to the chromosome end. A tlc1h strain has short but stable telomeres and no growth defect. We show here that Rap1p and the Rap1p-associated Rif2p did not bind to a telomere that contains purely vertebrate repeats, while the TG1–3 single-stranded DNA binding protein Cdc13p and the normally non-telomeric protein Tbf1p did bind this telomere. A chromosome with one entirely vertebrate-sequence telomere had a wild-type loss rate, and the telomere was maintained at a short but stable length. However, this telomere was unable to silence a telomere-adjacent URA3 gene, and the strain carrying this telomere had a severe defect in meiosis. We conclude that Rap1p localization to a C3TA2 telomere is not required for its essential mitotic functions. PMID:12660174

  17. Extreme Telomere Length Dimorphism in the Tasmanian Devil and Related Marsupials Suggests Parental Control of Telomere Length

    PubMed Central

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

    2012-01-01

    Telomeres, specialised structures that protect chromosome ends, play a critical role in preserving chromosome integrity. Telomere dynamics in the Tasmanian devil (Sarcophilus harrisii) are of particular interest in light of the emergence of devil facial tumour disease (DFTD), a transmissible malignancy that causes rapid mortality and threatens the species with extinction. We used fluorescent in situ hybridisation to investigate telomere length in DFTD cells, in healthy Tasmanian devils and in four closely related marsupial species. Here we report that animals in the Order Dasyuromorphia have chromosomes characterised by striking telomere length dimorphism between homologues. Findings in sex chromosomes suggest that telomere length dimorphism may be regulated by events in the parental germlines. Long telomeres on the Y chromosome imply that telomere lengthening occurs during spermatogenesis, whereas telomere diminution occurs during oogenesis. Although found in several somatic cell tissue types, telomere length dimorphism was not found in DFTD cancer cells, which are characterised by uniformly short telomeres. This is, to our knowledge, the first report of naturally occurring telomere length dimorphism in any species and suggests a novel strategy of telomere length control. Comparative studies in five distantly related marsupials and a monotreme indicate that telomere dimorphism evolved at least 50 million years ago. PMID:23049977

  18. Three-dimensional Nuclear Telomere Organization in Multiple Myeloma12

    PubMed Central

    Klewes, Ludger; Vallente, Rhea; Dupas, Eric; Brand, Carolin; Grün, Dietrich; Guffei, Amanda; Sathitruangsak, Chirawadee; Awe, Julius A; Kuzyk, Alexandra; Lichtensztejn, Daniel; Tammur, Pille; Ilus, Tiiu; Tamm, Anu; Punab, Mari; Rubinger, Morel; Olujohungbe, Adebayo; Mai, Sabine

    2013-01-01

    Multiple myeloma (MM) is preceded by monoclonal gammopathy of undetermined significance (MGUS). Up to date, it is difficult to predict an individual's time to disease progression and the treatment response. To examine whether the nuclear telomeric architecture will unravel some of these questions, we carried out. Three-dimensional (3D) telomere analysis on samples from patients diagnosed with MGUS and MM, as well as from patients who went into relapse. Telomere signal intensity, number of telomere aggregates, nuclear volume, and the overall nuclear telomere distribution (a/c ratio) were analyzed. The telomeric profiles allowed for the differentiation of the disease stages. The telomeric profiles of myeloma cells obtained from blood and bone marrow aspirates were identical. Based on this study, we discuss the use of 3D telomere profiling as a potential future tool for risk stratification and personalized treatment decisions. PMID:24466378

  19. SMARCAL1 Resolves Replication Stress at ALT Telomeres.

    PubMed

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

    2016-02-01

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

  20. Insomnia and Telomere Length in Older Adults

    PubMed Central

    Carroll, Judith E.; Esquivel, Stephanie; Goldberg, Alyssa; Seeman, Teresa E.; Effros, Rita B.; Dock, Jeffrey; Olmstead, Richard; Breen, Elizabeth C.; Irwin, Michael R.

    2016-01-01

    Study Objectives: Insomnia, particularly in later life, may raise the risk for chronic diseases of aging and mortality through its effect on cellular aging. The current study examines the effects of insomnia on telomere length, a measure of cellular aging, and tests whether insomnia interacts with chronological age to increase cellular aging. Methods: A total of 126 males and females (60–88 y) were assessed for insomnia using the Diagnostic and Statistical Manual IV criterion for primary insomnia and the International Classification of Sleep Disorders, Second Edition for general insomnia (45 insomnia cases; 81 controls). Telomere length in peripheral blood mononuclear cells (PBMC) was determined using real-time quantitative polymerase chain reaction (qPCR) methodology. Results: In the analysis of covariance model adjusting for body mass index and sex, age (60–69 y versus 70–88 y) and insomnia diagnosis interacted to predict shorter PBMC telomere length (P = 0.04). In the oldest age group (70–88 y), PBMC telomere length was significantly shorter in those with insomnia, mean (standard deviation) M(SD) = 0.59(0.2) compared to controls with no insomnia M(SD) = 0.78(0.4), P = 0.04. In the adults aged 60–69 y, PBMC telomere length was not different between insomnia cases and controls, P = 0.44. Conclusions: Insomnia is associated with shorter PBMC telomere length in adults aged 70–88 y, but not in those younger than 70 y, suggesting that clinically severe sleep disturbances may increase cellular aging, especially in the later years of life. These findings highlight insomnia as a vulnerability factor in later life, with implications for risk for diseases of aging. Citation: Carroll JE, Esquivel S, Goldberg A, Seeman TE, Effros RB, Dock J, Olmstead R, Breen EC, Irwin MR. Insomnia and telomere length in older adults. SLEEP 2016;39(3):559–564. PMID:26715231

  1. Telomere uncapping by the G-quadruplex ligand RHPS4 inhibits clonogenic tumour cell growth in vitro and in vivo consistent with a cancer stem cell targeting mechanism.

    PubMed

    Phatak, P; Cookson, J C; Dai, F; Smith, V; Gartenhaus, R B; Stevens, M F G; Burger, A M

    2007-04-23

    The pentacyclic acridinium methosulfate salt RHPS4 induces the 3'single-stranded guanine-rich telomeric overhang to fold into a G-quadruplex structure. Stabilisation of the latter is incompatible with an attachment of telomerase to the telomere and thus G-quadruplex ligands can effectively inhibit both the catalytic and capping functions of telomerase. In this study, we examined mechanisms underlying telomere uncapping by RHPS4 in uterus carcinoma cells (UXF1138L) with short telomeres and compared the susceptibility of bulk and clonogenic cancer cells to the G-quadruplex ligand. We show that treatment of UXF1138L cells with RHPS4 leads to the displacement of the telomerase catalytic subunit (hTERT) from the nucleus, induction of telomere-initiated DNA-damage signalling and chromosome fusions. We further report that RHPS4 is more potent against cancer cells that grow as colonies in soft agar than cells growing as monolayers. Human cord blood and HEK293T embryonic kidney cell colony forming units, however, were more resistant to RHPS4. RHPS4-treated UXF1138L xenografts had a decreased clonogenicity, showed loss of nuclear hTERT expression and an induction of mitotic abnormalities compared with controls. Although single-agent RHPS4 had limited in vivo efficacy, a combination of RHPS4 with the mitotic spindle poison Taxol caused tumour remissions and further enhancement of telomere dysfunction. PMID:17406367

  2. Telomere uncapping by the G-quadruplex ligand RHPS4 inhibits clonogenic tumour cell growth in vitro and in vivo consistent with a cancer stem cell targeting mechanism

    PubMed Central

    Phatak, P; Cookson, J C; Dai, F; Smith, V; Gartenhaus, R B; Stevens, M F G; Burger, A M

    2007-01-01

    The pentacyclic acridinium methosulfate salt RHPS4 induces the 3′single-stranded guanine-rich telomeric overhang to fold into a G-quadruplex structure. Stabilisation of the latter is incompatible with an attachment of telomerase to the telomere and thus G-quadruplex ligands can effectively inhibit both the catalytic and capping functions of telomerase. In this study, we examined mechanisms underlying telomere uncapping by RHPS4 in uterus carcinoma cells (UXF1138L) with short telomeres and compared the susceptibility of bulk and clonogenic cancer cells to the G-quadruplex ligand. We show that treatment of UXF1138L cells with RHPS4 leads to the displacement of the telomerase catalytic subunit (hTERT) from the nucleus, induction of telomere-initiated DNA-damage signalling and chromosome fusions. We further report that RHPS4 is more potent against cancer cells that grow as colonies in soft agar than cells growing as monolayers. Human cord blood and HEK293T embryonic kidney cell colony forming units, however, were more resistant to RHPS4. RHPS4-treated UXF1138L xenografts had a decreased clonogenicity, showed loss of nuclear hTERT expression and an induction of mitotic abnormalities compared with controls. Although single-agent RHPS4 had limited in vivo efficacy, a combination of RHPS4 with the mitotic spindle poison Taxol caused tumour remissions and further enhancement of telomere dysfunction. PMID:17406367

  3. Swi1Timeless Prevents Repeat Instability at Fission Yeast Telomeres.

    PubMed

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

    2016-03-01

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

  4. Swi1Timeless Prevents Repeat Instability at Fission Yeast Telomeres

    PubMed Central

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

    2016-01-01

    Genomic instability associated with DNA replication stress is linked to cancer and genetic pathologies in humans. If not properly regulated, replication stress, such as fork stalling and collapse, can be induced at natural replication impediments present throughout the genome. The fork protection complex (FPC) is thought to play a critical role in stabilizing stalled replication forks at several known replication barriers including eukaryotic rDNA genes and the fission yeast mating-type locus. However, little is known about the role of the FPC at other natural impediments including telomeres. Telomeres are considered to be difficult to replicate due to the presence of repetitive GT-rich sequences and telomere-binding proteins. However, the regulatory mechanism that ensures telomere replication is not fully understood. Here, we report the role of the fission yeast Swi1Timeless, a subunit of the FPC, in telomere replication. Loss of Swi1 causes telomere shortening in a telomerase-independent manner. Our epistasis analyses suggest that heterochromatin and telomere-binding proteins are not major impediments for telomere replication in the absence of Swi1. Instead, repetitive DNA sequences impair telomere integrity in swi1Δ mutant cells, leading to the loss of repeat DNA. In the absence of Swi1, telomere shortening is accompanied with an increased recruitment of Rad52 recombinase and more frequent amplification of telomere/subtelomeres, reminiscent of tumor cells that utilize the alternative lengthening of telomeres pathway (ALT) to maintain telomeres. These results suggest that Swi1 ensures telomere replication by suppressing recombination and repeat instability at telomeres. Our studies may also be relevant in understanding the potential role of Swi1Timeless in regulation of telomere stability in cancer cells. PMID:26990647

  5. Epigenetic Regulation of Mammalian Stem Cells

    PubMed Central

    Li, Xuekun

    2008-01-01

    Two critical properties of stem cells are self-renewal and multipotency. The maintenance of their “stemness” state and commitment to differentiation are therefore tightly controlled by intricate molecular networks. Epigenetic mechanisms, including DNA methylation, chromatin remodeling and the noncoding RNA-mediated process, have profound regulatory roles in mammalian gene expression. Recent studies have shown that epigenetic regulators are key players in stem cell biology and their dysfunction can result in human diseases such as cancer and neurodevelopmental disorders. Here, we review the recent evidences that advance our knowledge in epigenetic regulations of mammalian stem cells, with focus on embryonic stem cells and neural stem cells. PMID:18393635

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

    PubMed

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

    2012-12-27

    Telomeric DNA repeats are lost as normal somatic cells replicate. When telomeres reach a critically short length, a DNA damage signal is initiated, inducing cell senescence. Some studies have indicated that telomere length correlates with mortality, suggesting that telomere length contributes to human life span; however, other studies report no correlation, and thus the issue remains controversial. Domestic dogs show parallels in telomere biology to humans, with similar telomere length, telomere attrition, and absence of somatic cell telomerase activity. Using this model, we find that peripheral blood mononuclear cell (PBMC) telomere length is a strong predictor of average life span among 15 different breeds (p < 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. PMID:23260664

  7. RAP1 stimulates single- to double-strand association of yeast telomeric DNA: implications for telomere-telomere interactions.

    PubMed Central

    Gilson, E; Müller, T; Sogo, J; Laroche, T; Gasser, S M

    1994-01-01

    Repressor Activator Protein 1 (RAP1) of Saccharomyces cerevisiae is an abundant nuclear protein implicated in telomere length maintenance, transactivation, and in the establishment of silent chromatin domains. The RAP1 binding site 5' of the yeast HIS4 gene is also a region of hyperrecombination in meiosis. We report here that as RAP1 binds its recognition consensus, it appears to untwist double-stranded DNA, which we detect as the introduction of a negative supercoil in circularization assays. Coincident with the RAP1-dependent untwisting, we observe stimulation of the association of a single-stranded yeast telomeric sequence with its homologous double-stranded sequence in a supercoiled plasmid. This unusual distortion of the DNA double helix by RAP1 may contribute to the RAP1-dependent enhancement of recombination rates and promote non-duplex strand interactions at telomeres. Images PMID:7816621

  8. Decreasing initial telomere length in humans intergenerationally understates age-associated telomere shortening

    PubMed Central

    Holohan, Brody; De Meyer, Tim; Batten, Kimberly; Mangino, Massimo; Hunt, Steven C; Bekaert, Sofie; De Buyzere, Marc L; Rietzschel, Ernst R; Spector, Tim D; Wright, Woodring E; Shay, Jerry W

    2015-01-01

    Telomere length shortens with aging, and short telomeres have been linked to a wide variety of pathologies. Previous studies suggested a discrepancy in age-associated telomere shortening rate estimated by cross-sectional studies versus the rate measured in longitudinal studies, indicating a potential bias in cross-sectional estimates. Intergenerational changes in initial telomere length, such as that predicted by the previously described effect of a father’s age at birth of his offspring (FAB), could explain the discrepancy in shortening rate measurements. We evaluated whether changes occur in initial telomere length over multiple generations in three large datasets and identified paternal birth year (PBY) as a variable that reconciles the difference between longitudinal and cross-sectional measurements. We also clarify the association between FAB and offspring telomere length, demonstrating that this effect is substantially larger than reported in the past. These results indicate the presence of a downward secular trend in telomere length at birth over generational time with potential public health implications. PMID:25952108

  9. The yeast telomere length regulator TEL2 encodes a protein that binds to telomeric DNA.

    PubMed Central

    Kota, R S; Runge, K W

    1998-01-01

    TEL2 is required for telomere length regulation and viability in Saccharomyces cerevisiae. To investigate the mechanism by which Tel2p regulates telomere length, the majority (65%) of the TEL2 ORF was fused to the 3'-end of the gene for maltose binding protein, expressed in bacteria and the purified protein used in DNA binding studies. Rap1p, the major yeast telomere binding protein, recognizes a 13 bp duplex site 5'-GGTGTGTGGGTGT-3' in yeast telomeric DNA with high affinity. Gel shift experiments revealed that the MBP-Tel2p fusion binds the double-stranded yeast telomeric Rap1p site in a sequence-specific manner. Analysis of mutated sites showed that MBP-Tel2p could bind 5'-GTGTGTGG-3' within this 13 bp site. Methylation interference analysis revealed that Tel2p contacts the 5'-terminal guanine in the major groove. MBP-Tel2p did not bind duplex telomeric DNA repeats from vertebrates, Tetrahymena or Oxytricha. These results suggest that Tel2p is a DNA binding protein that recognizes yeast telomeric DNA. PMID:9490802

  10. Decreasing initial telomere length in humans intergenerationally understates age-associated telomere shortening.

    PubMed

    Holohan, Brody; De Meyer, Tim; Batten, Kimberly; Mangino, Massimo; Hunt, Steven C; Bekaert, Sofie; De Buyzere, Marc L; Rietzschel, Ernst R; Spector, Tim D; Wright, Woodring E; Shay, Jerry W

    2015-08-01

    Telomere length shortens with aging, and short telomeres have been linked to a wide variety of pathologies. Previous studies suggested a discrepancy in age-associated telomere shortening rate estimated by cross-sectional studies versus the rate measured in longitudinal studies, indicating a potential bias in cross-sectional estimates. Intergenerational changes in initial telomere length, such as that predicted by the previously described effect of a father's age at birth of his offspring (FAB), could explain the discrepancy in shortening rate measurements. We evaluated whether changes occur in initial telomere length over multiple generations in three large datasets and identified paternal birth year (PBY) as a variable that reconciles the difference between longitudinal and cross-sectional measurements. We also clarify the association between FAB and offspring telomere length, demonstrating that this effect is substantially larger than reported in the past. These results indicate the presence of a downward secular trend in telomere length at birth over generational time with potential public health implications. PMID:25952108

  11. Medaka fish exhibits longevity gender gap, a natural drop in estrogen and telomere shortening during aging: a unique model for studying sex-dependent longevity

    PubMed Central

    2013-01-01

    for studying the direct effect of increased estrogen on telomere length and longevity without the breast cancer complications reported in rodents. The findings strongly support the notion that O. latipes is a unique non-mammalian model for validation of estrogenic influence on telomere and longevity in vertebrates. This laboratory model fish is of potential significance for deciphering the ostensibly conserved mechanism(s) of sex-associated longevity in vertebrates. PMID:24364913

  12. Erectile dysfunction.

    PubMed

    Yafi, Faysal A; Jenkins, Lawrence; Albersen, Maarten; Corona, Giovanni; Isidori, Andrea M; Goldfarb, Shari; Maggi, Mario; Nelson, Christian J; Parish, Sharon; Salonia, Andrea; Tan, Ronny; Mulhall, John P; Hellstrom, Wayne J G

    2016-01-01

    Erectile dysfunction is a multidimensional but common male sexual dysfunction that involves an alteration in any of the components of the erectile response, including organic, relational and psychological. Roles for nonendocrine (neurogenic, vasculogenic and iatrogenic) and endocrine pathways have been proposed. Owing to its strong association with metabolic syndrome and cardiovascular disease, cardiac assessment may be warranted in men with symptoms of erectile dysfunction. Minimally invasive interventions to relieve the symptoms of erectile dysfunction include lifestyle modifications, oral drugs, injected vasodilator agents and vacuum erection devices. Surgical therapies are reserved for the subset of patients who have contraindications to these nonsurgical interventions, those who experience adverse effects from (or are refractory to) medical therapy and those who also have penile fibrosis or penile vascular insufficiency. Erectile dysfunction can have deleterious effects on a man's quality of life; most patients have symptoms of depression and anxiety related to sexual performance. These symptoms, in turn, affect his partner's sexual experience and the couple's quality of life. This Primer highlights numerous aspects of erectile dysfunction, summarizes new treatment targets and ongoing preclinical studies that evaluate new pharmacotherapies, and covers the topic of regenerative medicine, which represents the future of sexual medicine. PMID:27188339

  13. Cross-Species Interaction between Rapidly Evolving Telomere-Specific Drosophila Proteins

    PubMed Central

    Vedelek, Balázs; Blastyák, András; Boros, Imre M.

    2015-01-01

    Telomere integrity in Drosophila melanogaster is maintained by a putative multisubunit complex called terminin that is believed to act in analogy to the mammalian shelterin complex in protecting chromosome ends from being recognized as sites of DNA damage. The five proteins supposed to form the terminin complex are HP1-ORC associated protein, HP1-HOAP interacting protein, Verrocchio, Drosophila Telomere Loss/Modigliani and Heterochromatic Protein 1. Four of these proteins evolve rapidly within the Drosophila genus. The accelerated evolution of terminin components may indicate the involvement of these proteins in the process by which new species arise, as the resulting divergence of terminin proteins might prevent hybrid formation, thus driving speciation. However, terminin is not an experimentally proven entity, and no biochemical studies have been performed to investigate its assembly and action in detail. Motivated by these facts in order to initiate biochemical studies on terminin function, we attempted to reconstitute terminin by co-expressing its subunits in bacteria and investigated the possible role of the fast-evolving parts of terminin components in complex assembly. Our results suggest formation of stable subcomplexes of terminin, but not of the whole complex in vitro. We found that the accelerated evolution is restricted to definable regions of terminin components, and that the divergence of D. melanogaster Drosophila Telomere Loss and D. yakuba Verrocchio proteins does not preclude their stable interaction. PMID:26566042

  14. Comparison of telomere length and association with progenitor cell markers in lacrimal gland between Sjögren syndrome and non-Sjögren syndrome dry eye patients

    PubMed Central

    Kawashima, Motoko; Maida, Yoshiko; Kamoi, Mizuka; Ogawa, Yoko; Shimmura, Shigeto; Masutomi, Kenkichi; Tsubota, Kazuo

    2011-01-01

    Purpose Indicators of aging such as disruption of telomeric function due to shortening may be more frequent in dysfunctional lacrimal gland. The aims of this study were to 1) determine the viability of quantitative fluorescence in situ hybridization of telomeres (telo-FISH) for the assessment of telomere length in lacrimal gland in Sjögren and non- Sjögren syndrome patients; and 2) investigate the relationship between progenitor cell markers and telomere length in both groups. Methods Quantitative fluorescence in situ hybridization with a peptide nucleic acid probe complementary to the telomere repeat sequence was performed on frozen sections from human lacrimal gland tissues. The mean fluorescence intensity of telomere spots was automatically quantified by image analysis as relative telomere length in lacrimal gland epithelial cells. Immunostaining for p63, nucleostemin, ATP-binding cassette, sub-family G, member 2 (ABCG2), and nestin was also performed. Results Telomere intensity in the Sjögren syndrome group (6,785.0±455) was significantly lower than that in the non-Sjögren syndrome group (7,494.7±477; p=0.02). Among the samples from the non-Sjögren syndrome group, immunostaining revealed that p63 was expressed in 1–3 acinar cells in each acinar unit and continuously in the basal layer of duct cells. In contrast, in the Sjögren syndrome group, p63 and nucleostemin showed a lower level of expression. ABCG2 was expressed in acinar cells in both sjogren and non-Sjogren syndrome. Conclusions The results of this study indicate that 1) telo-FISH is a viable method of assessing telomere length in lacrimal gland, and 2) telomere length in Sjögren syndrome is shorter and associated with lower levels of expression of p63 and nucleostemin than in non-Sjögren syndrome. PMID:21655359

  15. The effect of Ku on telomere replication time is mediated by telomere length but is independent of histone tail acetylation

    PubMed Central

    Lian, Hui-Yong; Robertson, E. Douglas; Hiraga, Shin-ichiro; Alvino, Gina M.; Collingwood, David; McCune, Heather J.; Sridhar, Akila; Brewer, Bonita J.; Raghuraman, M. K.; Donaldson, Anne D.

    2011-01-01

    DNA replication in Saccharomyces cerevisiae proceeds according to a temporal program. We have investigated the role of the telomere-binding Ku complex in specifying late replication of telomere-proximal sequences. Genome-wide analysis shows that regions extending up to 80 kb from telomeres replicate abnormally early in a yku70 mutant. We find that Ku does not appear to regulate replication time by binding replication origins directly, nor is its effect on telomere replication timing mediated by histone tail acetylation. We show that Ku instead regulates replication timing through its effect on telomere length, because deletion of the telomerase regulator Pif1 largely reverses the short telomere defect of a yku70 mutant and simultaneously rescues its replication timing defect. Consistent with this conclusion, deleting the genome integrity component Elg1 partially rescued both length and replication timing of yku70 telomeres. Telomere length–mediated control of replication timing requires the TG1–3 repeat-counting component Rif1, because a rif1 mutant replicates telomeric regions early, despite having extended TG1–3 tracts. Overall, our results suggest that the effect of Ku on telomere replication timing results from its impact on TG1–3 repeat length and support a model in which Rif1 measures telomere repeat length to ensure that telomere replication timing is correctly programmed. PMID:21441303

  16. Telomere Length Regulation and Telomeric Chromatin Require the Nonsense-Mediated mRNA Decay Pathway

    PubMed Central

    Lew, Jodi E.; Enomoto, Shinichiro; Berman, Judith

    1998-01-01

    Rap1p localization factor 4 (RLF4) is a Saccharomyces cerevisiae gene that was identified in a screen for mutants that affect telomere function and alter the localization of the telomere binding protein Rap1p. In rlf4 mutants, telomeric silencing is reduced and telomere DNA tracts are shorter, indicating that RLF4 is required for both the establishment and/or maintenance of telomeric chromatin and for the control of telomere length. In this paper, we demonstrate that RLF4 is allelic to NMD2/UPF2, a gene required for the nonsense-mediated mRNA decay (NMD) pathway (Y. Cui, K. W. Hagan, S. Zhang, and S. W. Peltz, Mol. Cell. Biol. 9:423–436, 1995, and F. He and A. Jacobson, Genes Dev. 9:437–454, 1995). The NMD pathway, which requires Nmd2p/Rlf4p together with two other proteins, (Upf1p and Upf3p), targets nonsense messages for degradation in the cytoplasm by the exoribonuclease Xrn1p. Deletion of UPF1 and UPF3 caused telomere-associated defects like those caused by rlf4 mutations, implying that the NMD pathway, rather than an NMD-independent function of Nmd2p/Rlf4p, is required for telomere functions. In addition, telomere length regulation required Xrn1p but not Rat1p, a nuclear exoribonuclease with functional similarity to Xrn1p (A. W. Johnson, Mol. Cell. Biol. 17:6122–6130, 1997). In contrast, telomere-associated defects were not observed in pan2, pan3, or pan2 pan3 strains, which are defective in the intrinsic deadenylation-dependent decay of normal (as opposed to nonsense) mRNAs. Thus, loss of the NMD pathway specifically causes defects at telomeres, demonstrating a physiological requirement for the NMD pathway in normal cell functions. We propose a model in which the NMD pathway regulates the levels of specific mRNAs that are important for telomere functions. PMID:9742129

  17. mRNA deadenylation and telomere disease

    PubMed Central

    Mason, Philip J.; Bessler, Monica

    2015-01-01

    Dyskeratosis congenita (DC) is an inherited BM failure disorder that is associated with mutations in genes involved with telomere function and maintenance; however, the genetic cause of many instances of DC remains uncharacterized. In this issue of the JCI, Tummala and colleagues identify mutations in the gene encoding the poly(A)-specific ribonuclease (PARN) in individuals with a severe form of DC in three different families. PARN deficiency resulted in decreased expression of genes required for telomere maintenance and an aberrant DNA damage response, including increased levels of p53. Together, the results of this study support PARN as a DC-associated gene and suggest a potential link between p53 and telomere shortening. PMID:25893598

  18. Essential role of the Cdk2 activator RingoA in meiotic telomere tethering to the nuclear envelope

    PubMed Central

    Mikolcevic, Petra; Isoda, Michitaka; Shibuya, Hiroki; del Barco Barrantes, Ivan; Igea, Ana; Suja, José A.; Shackleton, Sue; Watanabe, Yoshinori; Nebreda, Angel R.

    2016-01-01

    Cyclin-dependent kinases (CDKs) play key roles in cell cycle regulation. Genetic analysis in mice has revealed an essential role for Cdk2 in meiosis, which renders Cdk2 knockout (KO) mice sterile. Here we show that mice deficient in RingoA, an atypical activator of Cdk1 and Cdk2 that has no amino acid sequence homology to cyclins, are sterile and display meiotic defects virtually identical to those observed in Cdk2 KO mice including non-homologous chromosome pairing, unrepaired double-strand breaks, undetectable sex-body and pachytene arrest. Interestingly, RingoA is required for Cdk2 targeting to telomeres and RingoA KO spermatocytes display severely affected telomere tethering as well as impaired distribution of Sun1, a protein essential for the attachment of telomeres to the nuclear envelope. Our results identify RingoA as an important activator of Cdk2 at meiotic telomeres, and provide genetic evidence for a physiological function of mammalian Cdk2 that is not dependent on cyclins. PMID:27025256

  19. Individual Telomere Lengths in Chronic Myeloid Leukemia12

    PubMed Central

    Samassekou, Oumar; Ntwari, Aimé; Hébert, Josée; Yan, Ju

    2009-01-01

    Chronic myeloid leukemia (CML) is a neoplasia characterized by proliferation of a myeloid cell lineage and chromosome translocation t(9;22) (q34;q11.2). As in the case of most cancers, the average telomere length in CML cells is shorter than that in normal blood cells. However, there are currently no data available concerning specific individual telomere length in CML. Here, we studied telomere length on each chromosome arm of CML cells. In situ hybridization with peptide nucleic acid probes was performed on CML cells in metaphase. The fluorescence intensity of each specific telomere was converted into kilobases according to the telomere restriction fragment results for each sample. We found differences in telomere length between short arm ends and long arm ends. We observed recurrent telomere length changes as well as telomere length maintenance and elongation in some individual telomeres. We propose a possible involvement of individual telomere length changes to some chromosomal abnormalities in CML. We suggest that individual telomere length maintenance is chromosome arm-specific associated with leukemia cells. PMID:19881950

  20. Shelterin complex and associated factors at human telomeres

    PubMed Central

    Diotti, Raffaella

    2011-01-01

    The processes regulating telomere function have major impacts on fundamental issues in human cancer biology. First, active telomere maintenance is almost always required for full oncogenic transformation of human cells, through cellular immortalization by endowment of an infinite replicative potential. Second, the attrition that telomeres undergo upon replication is responsible for the finite replicative life span of cells in culture, a process called senescence, which is of paramount importance for tumor suppression in vivo. The process of telomere-based senescence is intimately coupled to the induction of a DNA damage response emanating from telomeres, which can be elicited by both the ATM and ATR dependent pathways. At telomeres, the shelterin complex is constituted by a group of six proteins which assembles quantitatively along the telomere tract, and imparts both telomere maintenance and telomere protection. Shelterin is known to regulate the action of telomerase, and to prevent inappropriate DNA damage responses at chromosome ends, mostly through inhibition of ATM and ATR. The roles of shelterin have increasingly been associated with transient interactions with downstream factors that are not associated quantitatively or stably with telomeres. Here, some of the important known interactions between shelterin and these associated factors and their interplay to mediate telomere functions are reviewed. PMID:21738835

  1. Determination of Arabidopsis thaliana telomere length by PCR.

    PubMed

    Vaquero-Sedas, María I; Vega-Palas, Miguel A

    2014-01-01

    In humans, telomere length studies have acquired great relevance because the length of telomeres has been related to natural processes like disease, aging and cancer. However, very little is known about the influence of telomere length on the biology of wild type plants. The length of plant telomeres has been usually studied by Terminal Restriction Fragment (TRF) analyses. This technique requires high amounts of tissue, including multiple cell types, which might be the reason why very little is known about the influence of telomere length on plant natural processes. In contrast, many of the human telomere length studies have focused on homogenous cell populations. Most of these studies have been performed by PCR, using telomeric degenerated primers, which allow the determination of telomere length from small amounts of human cells. Here, we have adapted the human PCR procedure to analyze the length of Arabidopsis thaliana telomeres. This PCR approach will facilitate the analysis of telomere length from low amounts of tissue. We have used it to determine that CG and non CG DNA methylation positively regulates Arabidopsis telomere length. PMID:24986269

  2. Determination of Arabidopsis thaliana telomere length by PCR

    PubMed Central

    Vaquero-Sedas, María I.; Vega-Palas, Miguel A.

    2014-01-01

    In humans, telomere length studies have acquired great relevance because the length of telomeres has been related to natural processes like disease, aging and cancer. However, very little is known about the influence of telomere length on the biology of wild type plants. The length of plant telomeres has been usually studied by Terminal Restriction Fragment (TRF) analyses. This technique requires high amounts of tissue, including multiple cell types, which might be the reason why very little is known about the influence of telomere length on plant natural processes. In contrast, many of the human telomere length studies have focused on homogenous cell populations. Most of these studies have been performed by PCR, using telomeric degenerated primers, which allow the determination of telomere length from small amounts of human cells. Here, we have adapted the human PCR procedure to analyze the length of Arabidopsis thaliana telomeres. This PCR approach will facilitate the analysis of telomere length from low amounts of tissue. We have used it to determine that CG and non CG DNA methylation positively regulates Arabidopsis telomere length. PMID:24986269

  3. Assessing Telomere Length Using Surface Enhanced Raman Scattering

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  4. The role of telomere dynamics in aging and cancer

    NASA Astrophysics Data System (ADS)

    Blagoev, Krastan; Goodwin, Edwin

    2006-03-01

    Telomere length changes are far more dynamic than previously thought. In addition to a gradual loss of ˜100 base pairs per telomere in each cell division, losses as well as gains may occur within a single cell cycle. We are investigating how telomere exchange, extension, and deletion affect the proliferative potential of telomerase-negative somatic cells. Experimental techniques are being devised to detect dynamic telomere processes and quantify both the frequency and length changes of each. In parallel, a ``dynamic telomere model'' is being used that incorporates telomere dynamics to study how the telomere size distribution evolves with time. This is an essential step towards understanding the role that telomere dynamics play in the normal aging of tissues and organisms. The model casts light on relationships not otherwise easily explained by a deterministic ``mitotic clock,'' or to what extent the shortest initial telomere determines the onset of senescence. We also expect to identify biomarkers that will correlate with aging better than average telomere length and to shed light on the transition to unlimited growth found in telomerase-negative tumor cells having the ALT (alternative lengthening of telomeres) phenotype, and to evaluate strategies to suppress the growth of these tumors.

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

    PubMed Central

    Gao, Jin; Munch, Stephan B.

    2015-01-01

    Given finite resources, intense investment in one life history trait is expected to reduce investment in others. Although telomere length appears to be strongly tied to age in many taxa, telomere maintenance requires energy. We therefore hypothesize that telomere maintenance may trade off against other life history characters. We used natural variation in laboratory populations of Atlantic silversides (Menidia menidia) to study the relationship between growth, fecundity, life expectancy, and relative telomere length. In keeping with several other studies on fishes, we found no clear dependence of telomere length on age. However, we did find that more fecund fish tended to have both reduced life expectancy and shorter telomeres. This result is consistent with the hypothesis that there is a trade-off between telomere maintenance and reproductive output. PMID:25938489

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

    PubMed

    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. PMID:27154402

  7. ATM kinase is required for telomere elongation in mouse and human cells

    PubMed Central

    Lee, Stella Suyong; Bohrson, Craig; Pike, Alexandra Mims; Wheelan, Sarah Jo; Greider, Carol Widney

    2015-01-01

    Summary Short telomeres induce a DNA damage response, senescence and apoptosis; thus, maintaining telomere length equilibrium is essential for cell viability. Telomerase addition of telomere repeats is tightly regulated in cells. To probe pathways that regulate telomere addition, we developed the ADDIT assay to measure new telomere addition at a single telomere in vivo. Sequence analysis showed telomerase specific addition of repeats onto a new telomere occurred in just 48 hr. Using the ADDIT assay, we found that ATM is required for addition of new repeats onto telomeres in mouse cells. Evaluation of bulk telomeres, in both human and mouse cells, showed that blocking ATM inhibited telomere elongation. Finally, the activation of ATM through the inhibition of PARP1 resulted in increased telomere elongation, supporting the central role of the ATM pathway in regulating telomere addition. Understanding this role of ATM may yield new areas for possible therapeutic intervention in telomere-mediated disease. PMID:26586427

  8. Telomere Length: A Review of Methods for Measurement

    PubMed Central

    Montpetit, Alison J.; Alhareeri, Areej A.; Montpetit, Marty; Starkweather, Angela R.; Elmore, Lynne W.; Filler, Kristin; Mohanraj, Lathika; Burton, Candace W.; Menzies, Victoria S.; Lyon, Debra E.; Collins, Judith B.; Teefey, Joseph M.; Jackson-Cook, Colleen K.

    2014-01-01

    Background The exciting discovery that telomere shortening is associated with many health conditions, and that telomere lengths can be altered in response to social and environmental exposures, has underscored the need for methods to accurately and consistently quantify telomere length. Objectives The purpose of this paper is to provide a comprehensive summary that compares and contrasts the current technologies used to assess telomere length. Discussion Multiple methods have been developed for the study of telomeres. These techniques include quantification of telomere length by terminal restriction fragmentation—which was one of the earliest tools used for length assessment—making it the gold standard in telomere biology. Quantitative-PCR provides the advantage of being able to use smaller amounts of DNA, thereby making it amenable to epidemiology studies involving large numbers of people. An alternative method uses fluorescent probes to quantify not only mean telomere lengths, but also chromosome-specific telomere lengths; however, the downside of this approach is that it can only be used on mitotically active cells. Additional methods that permit assessment of the length of a subset of chromosome-specific telomeres, or the subset of telomeres that demonstrate shortening, are also reviewed. Conclusion Given the increased utility for telomere assessments as a biomarker in physiological, psychological and biobehavioral research, it is important that investigators become familiar with the methodological nuances of the various procedures used for measuring telomere length. This will ensure that they are empowered to select an optimal assessment approach to meet the needs of their study designs. Gaining a better understanding of the benefits and drawbacks of various measurement techniques is important not only in individual studies, but also to further establish the science of telomere associations with biobehavioral phenomena. PMID:24977726

  9. Gustatory dysfunction

    PubMed Central

    Maheswaran, T.; Abikshyeet, P.; Sitra, G.; Gokulanathan, S.; Vaithiyanadane, V.; Jeelani, S.

    2014-01-01

    Tastes in humans provide a vital tool for screening soluble chemicals for food evaluation, selection, and avoidance of potentially toxic substances. Taste or gustatory dysfunctions are implicated in loss of appetite, unintended weight loss, malnutrition, and reduced quality of life. Dental practitioners are often the first clinicians to be presented with complaints about taste dysfunction. This brief review provides a summary of the common causes of taste disorders, problems associated with assessing taste function in a clinical setting and management options available to the dental practitioner. PMID:25210380

  10. ARSENIC EFFECTS ON TELOMERE AND TELOMERASE ACTIVITY

    EPA Science Inventory

    Arsenic effects on telomere and telomerase activity. T-C. Zhang, M. T. Schmitt, J. Mo, J. L. Mumford, National Research Council and U.S Environmental Protection Agency, NHEERL, Research Triangle Park, NC 27711
    Arsenic is a known carcinogen and also an anticancer agent for acut...

  11. Expansion of Interstitial Telomeric Sequences in Yeast.

    PubMed

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

    2015-11-24

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

  12. A loopy view of telomere evolution

    PubMed Central

    de Lange, Titia

    2015-01-01

    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. PMID:26539211

  13. Memory dysfunction.

    PubMed

    Amici, Serena

    2012-01-01

    Memory is the cognitive ability that allows to acquire, store and recall information; its dysfunction is called amnesia and can be a presentation of unilateral ischemic stroke in the territory of the posterior cerebral and anterior choroidal artery as well as subarachnoid hemorrhage. PMID:22377863

  14. Ejaculatory dysfunction.

    PubMed

    Phillips, Elizabeth; Carpenter, Christina; Oates, Robert D

    2014-02-01

    Ejaculatory dysfunction may occur after many different disorders ranging from traumatic spinal cord injury to diabetes mellitus. With an understanding of the many facets and nuances of the ejaculatory apparatus, both anatomic and neurologic, the well-versed clinician can proceed along a safe, efficient, and appropriate treatment algorithm to help affected men and their partners achieve parenthood. PMID:24286771

  15. Erectile Dysfunction

    MedlinePlus

    ... or vascular problems, will have a more difficult time returning to pre-treatment function. Management of Erectile Dysfunction When a man is sexually aroused, the erectile nerves running alongside the penis stimulate the ... blood to rush in. At the same time, tiny valves at the base of the penis ...

  16. Sensory Dysfunction

    MedlinePlus

    ... to Web version Sensory Dysfunction Overview Why are smell and taste important? Your senses of smell and taste let you fully enjoy the scents ... bitter and sour. Flavor involves both taste and smell. For example, because a person is able to ...

  17. Telomere length in human liver diseases.

    PubMed

    Urabe, Y; Nouso, K; Higashi, T; Nakatsukasa, H; Hino, N; Ashida, K; Kinugasa, N; Yoshida, K; Uematsu, S; Tsuji, T

    1996-10-01

    To determine the role of telomere-mediated gene stability in hepatocarcinogenesis, we examined the telomere length of human liver with or without chronic liver diseases and hepatocellular carcinomas (HCC). The mean telomere restriction fragment (TRF) length of normal liver (n = 13), chronic hepatitis (n = 11), liver cirrhosis (n = 24) and HCC (n = 24) was 7.8 +/- 0.2, 7.1 +/- 0.3, 6.4 +/- 0.2 and 5.2 +/- 0.2 kb, respectively (mean +/- standard error). TRF length decreased with a progression of chronic liver diseases and that in HCC was significantly shorter than that in other chronic liver diseases (p < 0.05). The ratios of TRF length of HCC to that of corresponding surrounding liver of well differentiated (n = 7), moderately differentiated (n = 10) and poorly differentiated (n = 4) HCCs were 0.83 +/- 0.06, 0.75 +/- 0.05 and 0.98 +/- 0.09, respectively. The ratio of poorly differentiated HCC was significantly higher than that of moderately differentiated HCC (p < 0.05). A comparison between the size and telomere length ratio of moderately differentiated HCCs revealed a decrease of the ratio with size until it reached 50 mm in diameter. In contrast, the ratio increased as the size enlarged over 50 mm. These findings suggest that the gene stability of the liver cells mediated by the telomere is reduced as chronic liver disease progresses and that telomerase is activated in poorly differentiated HCC and moderately differentiated HCC over 50 mm in diameter. PMID:8938628

  18. Telomere fusion in Drosophila: The role of subtelomeric chromatin.

    PubMed

    Marzullo, Marta; Gatti, Maurizio

    2015-07-01

    Drosophila telomeres are maintained by transposition to chromosome ends of the HeT-A, TART and TAHRE retrotransposons, collectively designated as HTT. Although all Drosophila telomeres terminate with HTT arrays and are capped by the terminin complex, they differ in the type of subtelomeric chromatin. The HTT sequences of YS, YL, XR, and 4L are juxtaposed to constitutive heterochromatin, while the HTTs of the other telomeres are linked to either the TAS repeat-associated chromatin (XL, 2L, 2R, 3L, 3R) or to the specialized 4R chromatin. We found that mutations in pendolino (peo) cause (telomeric fusions) that preferentially involve the heterochromatin-associated telomeres (Ha-telomeres), a telomeric fusion pattern never observed in the other 10 telomere-capping mutants characterized so far. Peo, is homologous to the E2 variant ubiquitin-conjugating enzymes and is required for DNA replication. Our analyses lead us to hypothesize that DNA replication in Peo-depleted cells results in specific fusigenic lesions concentrated in Ha-telomeres. These data provide the first demonstration that subtelomeres can affect telomere fusion. PMID:26786804

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

    PubMed Central

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

    2014-01-01

    Summary Telomere length maintenance is a requisite feature of cellular immortalization and a hallmark of human cancer. While most human cancers express telomerase activity, approximately 10-15% employ a recombination-dependent telomere maintenance pathway known as Alternative Lengthening of Telomeres (ALT) that is characterized by multi-telomere clusters and associated promyelocytic leukemia protein bodies. Here, we show that a DNA double-strand break (DSB) response at ALT telomeres triggers long-range movement and clustering between chromosome termini, resulting in homology-directed telomere synthesis. Damaged telomeres initiate increased random surveillance of nuclear space before displaying rapid directional movement and association with recipient telomeres over micron-range distances. This phenomenon required Rad51 and the Hop2-Mnd1 heterodimer, which are essential for homologous chromosome synapsis during meiosis. These findings implicate a specialized homology searching mechanism in ALT dependent telomere maintenance and provide a molecular basis underlying the preference for recombination between non- sister telomeres during ALT. PMID:25259924

  20. Telomere maintenance and the etiology of adult glioma.

    PubMed

    Walsh, Kyle M; Wiencke, John K; Lachance, Daniel H; Wiemels, Joseph L; Molinaro, Annette M; Eckel-Passow, Jeanette E; Jenkins, Robert B; Wrensch, Margaret R

    2015-11-01

    A growing body of epidemiologic and tumor genomic research has identified an important role for telomere maintenance in glioma susceptibility, initiation, and prognosis. Telomere length has long been investigated in relation to cancer, but whether longer or shorter telomere length might be associated with glioma risk has remained elusive. Recent data address this question and are reviewed here. Common inherited variants near the telomerase-component genes TERC and TERT are associated both with longer telomere length and increased risk of glioma. Exome sequencing of glioma patients from families with multiple affected members has identified rare inherited mutations in POT1 (protection of telomeres protein 1) as high-penetrance glioma risk factors. These heritable POT1 mutations are also associated with increased telomere length in leukocytes. Tumor sequencing studies further indicate that acquired somatic mutations of TERT and ATRX are among the most frequent alterations found in adult gliomas. These mutations facilitate telomere lengthening, thus bypassing a critical mechanism of apoptosis. Although future research is needed, mounting evidence suggests that glioma is, at least in part, a disease of telomere dysregulation. Specifically, several inherited and acquired variants underlying gliomagenesis affect telomere pathways and are also associated with increased telomere length. PMID:26014050

  1. Significant Correlation of Species Longevity with DNA Double Strand Break-Recognition but not with Telomere Length

    PubMed Central

    Lorenzini, Antonello; Johnson, F. Brad; Oliver, Anthony; Tresini, Maria; Smith, Jasmine S.; Hdeib, Mona; Sell, Christian; Cristofalo, Vincent J.; Stamato, Thomas D.

    2009-01-01

    Summary The identification of the cellular mechanisms responsible for the wide differences in species lifespan remains one of the major unsolved problems of the biology of aging. We measured the capacity of nuclear protein to recognize DNA double strand breaks (DSB) and telomere length of skin fibroblasts derived from mammalian species that exhibit wide differences in longevity. Our results indicate DNA DSB recognition increases exponentially with longevity. Further, an analysis of the level of Ku80 protein in human, cow, and mouse suggests that Ku levels vary dramatically between species and these levels are strongly correlated with longevity. In contrast mean telomere length appears to decrease with increasing longevity of the species, although not significantly. These findings suggest that an enhanced ability to bind to DNA-ends may be important for longevity. A number of possible roles for increased levels of Ku and DNA-PKcs are discussed. PMID:19896964

  2. Telomeres, Age and Reproduction in a Long-Lived Reptile

    PubMed Central

    Plot, Virginie; Criscuolo, François; Zahn, Sandrine; Georges, Jean-Yves

    2012-01-01

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

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

    PubMed Central

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

    2015-01-01

    Objective Patients with acromegaly exhibit reduced life expectancy and increased prevalence of age-related diseases, such as diabetes, hypertension, and cardiovascular disease. However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases. Methods We measured telomere length in patients with acromegaly using quantitative PCR method. The effect of GH and IGF-I on telomere length and cellular senescence was examined in human skin fibroblasts. Results Patients with acromegaly exhibited shorter telomere length than age-, sex-, smoking-, and diabetes-matched control patients with non-functioning pituitary adenoma (0.62 ± 0.23 vs. 0.75 ± 0.35, respectively, P = 0.047). In addition, telomere length in acromegaly was negatively correlated with the disease duration (R2 = 0.210, P = 0.003). In vitro analysis revealed that not GH but IGF-I induced telomere shortening in human skin fibroblasts. Furthermore, IGF-I-treated cells showed increased senescence-associated β-galactosidase activity and expression of p53 and p21 protein. IGF-I-treated cells reached the Hayflick limit earlier than GH- or vehicle-treated cells, indicating that IGF-I induces cellular senescence. Conclusion Shortened telomeres in acromegaly and cellular senescence induced by IGF-I can explain, in part, the underlying mechanisms by which acromegaly exhibits an increased morbidity and mortality in association with the excess secretion of IGF-I. PMID:26448623

  4. A Hypomorphic Mutation Reveals a Stringent Requirement for the ATM Checkpoint Protein in Telomere Protection During Early Cell Division in Drosophila

    PubMed Central

    Morciano, Patrizia; Zhang, Yi; Cenci, Giovanni; Rong, Yikang S.

    2013-01-01

    Using Drosophila as a model system, we identified a stringent requirement for the conserved function of Ataxia Telangiectasia Mutated (ATM) in telomere protection during early embryonic development. Animals homozygous for a hypomorphic mutation in atm develop normally with minimal telomere dysfunction. However, mutant females produce inviable embryos that succumb to mitotic failure caused by covalent fusions of telomeric DNA. Interestingly, although the atm mutation encodes a premature stop codon, it must not have eliminated the production of the mutant protein, and the mutant protein retains kinase activity upon DNA damage. Moreover, although the embryonic phenotype of this mutation resembles that of hypomorphic mutations in the MRN complex, the function of MRN appears normal in the atm embryos. In contrast, there is a prominent reduction of the level of HipHop, an essential member of the Drosophila capping complex. How ATM functions in telomere protection remains poorly understood. The amenability of Drosophila embryos to molecular and biochemical investigations ensures that this newly identified mutation will facilitate future studies of ATM in telomere maintenance. PMID:23604076

  5. A hypomorphic mutation reveals a stringent requirement for the ATM checkpoint protein in telomere protection during early cell division in Drosophila.

    PubMed

    Morciano, Patrizia; Zhang, Yi; Cenci, Giovanni; Rong, Yikang S

    2013-06-01

    Using Drosophila as a model system, we identified a stringent requirement for the conserved function of Ataxia Telangiectasia Mutated (ATM) in telomere protection during early embryonic development. Animals homozygous for a hypomorphic mutation in atm develop normally with minimal telomere dysfunction. However, mutant females produce inviable embryos that succumb to mitotic failure caused by covalent fusions of telomeric DNA. Interestingly, although the atm mutation encodes a premature stop codon, it must not have eliminated the production of the mutant protein, and the mutant protein retains kinase activity upon DNA damage. Moreover, although the embryonic phenotype of this mutation resembles that of hypomorphic mutations in the MRN complex, the function of MRN appears normal in the atm embryos. In contrast, there is a prominent reduction of the level of HipHop, an essential member of the Drosophila capping complex. How ATM functions in telomere protection remains poorly understood. The amenability of Drosophila embryos to molecular and biochemical investigations ensures that this newly identified mutation will facilitate future studies of ATM in telomere maintenance. PMID:23604076

  6. Insights into Cdc13 Dependent Telomere Length Regulation

    SciTech Connect

    M Mason; E Skordalakes

    2011-12-31

    Cdc13 is a single stranded telomere binding protein that specifically localizes to the telomere ends of budding yeasts and is essential for cell viability. It caps the ends of chromosomes thus preventing chromosome end-to-end fusions and exonucleolytic degradation, events that could lead to genomic instability and senescence, the hallmark of aging. Cdc13 is also involved in telomere length regulation by recruiting or preventing access of telomerase to the telomeric overhang. Recruitment of telomerase to the telomeres for G-strand extension is required for continuous cell division, while preventing its access to the telomeres through capping the chromosome ends prevents mitotic events that could lead to cell immortality, the hall mark of carcinogenesis. Cdc13 and its putative homologues human CTC1 and POT1 are therefore key to many biological processes directly associated with life extension and cancer prevention and can be viewed as an ideal target for cancer and age related therapies.

  7. RNA-template dependent de novo telomere addition.

    PubMed

    Fuhrmann, Gloria; Jönsson, Franziska; Weil, Patrick Philipp; Postberg, Jan; Lipps, Hans J

    2016-08-01

    De novo addition of telomeric sequences can occur at broken chromosomes and must be well controlled, which is essential during programmed DNA reorganization processes. In ciliated protozoa an extreme form of DNA-reorganization is observed during macronuclear differentiation after sexual reproduction leading to the elimination of specific parts of the germline genome. Regulating these processes involves small noncoding RNAs, but in addition DNA-reordering, excision and amplification require RNA templates deriving from the parental macronucleus. We show that these putative RNA templates can carry telomeric repeats. Microinjection of RNA templates carrying modified telomeres into the developing macronucleus leads to modified telomeres in vegetative cells, providing strong evidence, that de novo addition of telomeres depends on a telomere-containing transcript from the parental macronucleus. PMID:26786510

  8. DNA Repair at Telomeres: Keeping the Ends Intact

    PubMed Central

    Webb, Christopher J.; Wu, Yun; Zakian, Virginia A.

    2013-01-01

    The molecular era of telomere biology began with the discovery that telomeres usually consist of G-rich simple repeats and end with 3′ single-stranded tails. Enormous progress has been made in identifying the mechanisms that maintain and replenish telomeric DNA and the proteins that protect them from degradation, fusions, and checkpoint activation. Although telomeres in different organisms (or even in the same organism under different conditions) are maintained by different mechanisms, the disparate processes have the common goals of repairing defects caused by semiconservative replication through G-rich DNA, countering the shortening caused by incomplete replication, and postreplication regeneration of G tails. In addition, standard DNA repair mechanisms must be suppressed or modified at telomeres to prevent their being recognized and processed as DNA double-strand breaks. Here, we discuss the players and processes that maintain and regenerate telomere structure. PMID:23732473

  9. Telomere maintenance through recruitment of internal genomic regions.

    PubMed

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

    2015-01-01

    Cells surviving crisis are often tumorigenic and their telomeres are commonly maintained through the reactivation of telomerase. However, surviving cells occasionally activate a recombination-based mechanism called alternative lengthening of telomeres (ALT). Here we establish stably maintained survivors in telomerase-deleted Caenorhabditis elegans that escape from sterility by activating ALT. ALT survivors trans-duplicate an internal genomic region, which is already cis-duplicated to chromosome ends, across the telomeres of all chromosomes. These 'Template for ALT' (TALT) regions consist of a block of genomic DNA flanked by telomere-like sequences, and are different between two genetic background. We establish a model that an ancestral duplication of a donor TALT region to a proximal telomere region forms a genomic reservoir ready to be incorporated into telomeres on ALT activation. PMID:26382656

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

    PubMed

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

    1998-11-01

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

  11. Telomere shortening in neurological disorders: an abundance of unanswered questions.

    PubMed

    Eitan, Erez; Hutchison, Emmette R; Mattson, Mark P

    2014-05-01

    Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer's and Parkinson's patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders. PMID:24698125

  12. Telomere Shortening in Neurological Disorders: An Abundance of Unanswered Questions

    PubMed Central

    Eitan, Erez; Hutchison, Emmette R.; Mattson, Mark P.

    2014-01-01

    Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer’s and Parkinson’s patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders. PMID:24698125

  13. Telomeric Repeats Facilitate CENP-ACnp1 Incorporation via Telomere Binding Proteins

    PubMed Central

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

    2013-01-01

    The histone H3 variant, CENP-A, is normally assembled upon canonical centromeric sequences, but there is no apparent obligate coupling of sequence and assembly, suggesting that centromere location can be epigenetically determined. To explore the tolerances and constraints on CENP-A deposition we investigated whether certain locations are favoured when additional CENP-ACnp1 is present in fission yeast cells. Our analyses show that additional CENP-ACnp1 accumulates within and close to heterochromatic centromeric outer repeats, and over regions adjacent to rDNA and telomeres. The use of minichromosome derivatives with unique DNA sequences internal to chromosome ends shows that telomeres are sufficient to direct CENP-ACnp1 deposition. However, chromosome ends are not required as CENP-ACnp1 deposition also occurs at telomere repeats inserted at an internal locus and correlates with the presence of H3K9 methylation near these repeats. The Ccq1 protein, which is known to bind telomere repeats and recruit telomerase, was found to be required to induce H3K9 methylation and thus promote the incorporation of CENP-ACnp1 near telomere repeats. These analyses demonstrate that at non-centromeric chromosomal locations the presence of heterochromatin influences the sites at which CENP-A is incorporated into chromatin and, thus, potentially the location of centromeres. PMID:23936074

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

    PubMed

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

    2013-01-01

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

  15. Unraveling secrets of telomeres: one molecule at a time

    PubMed Central

    Lin, Jiangguo; Kaur, Parminder; Countryman, Preston; Opresko, Patricia L.; Wang, Hong

    2016-01-01

    Telomeres play important roles in maintaining the stability of linear chromosomes. Telomere maintenance involves dynamic actions of multiple proteins interacting with long repetitive sequences and complex dynamic DNA structures, such as G-quadruplexes, T-loops and t-circles. Given the heterogeneity and complexity of telomeres, single-molecule approaches are essential to fully understand the structure-function relationships that govern telomere maintenance. In this review, we present a brief overview of the principles of single-molecule imaging and manipulation techniques. We then highlight results obtained from applying these single-molecule techniques for studying structure, dynamics and functions of G-quadruplexes, telomerase, and shelterin proteins. PMID:24569170

  16. Air Pollution Stress and the Aging Phenotype: The Telomere Connection.

    PubMed

    Martens, Dries S; Nawrot, Tim S

    2016-09-01

    Aging is a complex physiological phenomenon. The question why some subjects grow old while remaining free from disease whereas others prematurely die remains largely unanswered. We focus here on the role of air pollution in biological aging. Hallmarks of aging can be grouped into three main categories: genomic instability, telomere attrition, and epigenetic alterations leading to altered mitochondrial function and cellular senescence. At birth, the initial telomere length of a person is largely determined by environmental factors. Telomere length shortens with each cell division and exposure to air pollution as well as low residential greens space exposure is associated with shorter telomere length. Recent studies show that the estimated effects of particulate air pollution exposure on the telomere mitochondrial axis of aging may play an important role in chronic health effects of air pollution. The exposome encompasses all exposures over an entire life. As telomeres can be considered as the cellular memories of exposure to oxidative stress and inflammation, telomere maintenance may be a proxy for assessing the "exposome". If telomeres are causally related to the aging phenotype and environmental air pollution is an important determinant of telomere length, this might provide new avenues for future preventive strategies. PMID:27357566

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

    PubMed

    Cukusic Kalajzic, Andrea; Vidacek, Nikolina Skrobot; Huzak, Miljenko; Ivankovic, Milena; Rubelj, Ivica

    2014-01-01

    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. PMID:24643066

  18. SMARCAL1 maintains telomere integrity during DNA replication.

    PubMed

    Poole, Lisa A; Zhao, Runxiang; Glick, Gloria G; Lovejoy, Courtney A; Eischen, Christine M; Cortez, David

    2015-12-01

    The SMARCAL1 (SWI/SNF related, matrix-associated, actin-dependent, regulator of chromatin, subfamily A-like 1) DNA translocase is one of several related enzymes, including ZRANB3 (zinc finger, RAN-binding domain containing 3) and HLTF (helicase-like transcription factor), that are recruited to stalled replication forks to promote repair and restart replication. These enzymes can perform similar biochemical reactions such as fork reversal; however, genetic studies indicate they must have unique cellular activities. Here, we present data showing that SMARCAL1 has an important function at telomeres, which present an endogenous source of replication stress. SMARCAL1-deficient cells accumulate telomere-associated DNA damage and have greatly elevated levels of extrachromosomal telomere DNA (C-circles). Although these telomere phenotypes are often found in tumor cells using the alternative lengthening of telomeres (ALT) pathway for telomere elongation, SMARCAL1 deficiency does not yield other ALT phenotypes such as elevated telomere recombination. The activity of SMARCAL1 at telomeres can be separated from its genome-maintenance activity in bulk chromosomal replication because it does not require interaction with replication protein A. Finally, this telomere-maintenance function is not shared by ZRANB3 or HLTF. Our results provide the first identification, to our knowledge, of an endogenous source of replication stress that requires SMARCAL1 for resolution and define differences between members of this class of replication fork-repair enzymes. PMID:26578802

  19. Maternal and genetic factors determine early life telomere length

    PubMed Central

    Asghar, Muhammad; Bensch, Staffan; Tarka, Maja; Hansson, Bengt; Hasselquist, Dennis

    2015-01-01

    In a broad range of species—including humans—it has been demonstrated that telomere length declines throughout life and that it may be involved in cell and organismal senescence. This potential link to ageing and thus to fitness has triggered recent interest in understanding how variation in telomere length is inherited and maintained. However, previous studies suffer from two main drawbacks that limit the possibility of understanding the relative importance of genetic, parental and environmental influences on telomere length variation. These studies have been based on (i) telomere lengths measured at different time points in different individuals, despite the fact that telomere length changes over life, and (ii) parent–offspring regression techniques, which do not enable differentiation between genetic and parental components of inheritance. To overcome these drawbacks, in our study of a songbird, the great reed warbler, we have analysed telomere length measured early in life in both parents and offspring and applied statistical models (so-called ‘animal models') that are based on long-term pedigree data. Our results showed a significant heritability of telomere length on the maternal but not on the paternal side, and that the mother's age was positively correlated with their offspring's telomere length. Furthermore, the pedigree-based analyses revealed a significant heritability and an equally large maternal effect. Our study demonstrates strong maternal influence on telomere length and future studies now need to elucidate possible underlying factors, including which types of maternal effects are involved. PMID:25621325

  20. The pif1 helicase, a negative regulator of telomerase, acts preferentially at long telomeres.

    PubMed

    Phillips, Jane A; Chan, Angela; Paeschke, Katrin; Zakian, Virginia A

    2015-04-01

    Telomerase, the enzyme that maintains telomeres, preferentially lengthens short telomeres. The S. cerevisiae Pif1 DNA helicase inhibits both telomerase-mediated telomere lengthening and de novo telomere addition at double strand breaks (DSB). Here, we report that the association of the telomerase subunits Est2 and Est1 at a DSB was increased in the absence of Pif1, as it is at telomeres, suggesting that Pif1 suppresses de novo telomere addition by removing telomerase from the break. To determine how the absence of Pif1 results in telomere lengthening, we used the single telomere extension assay (STEX), which monitors lengthening of individual telomeres in a single cell cycle. In the absence of Pif1, telomerase added significantly more telomeric DNA, an average of 72 nucleotides per telomere compared to the 45 nucleotides in wild type cells, and the fraction of telomeres lengthened increased almost four-fold. Using an inducible short telomere assay, Est2 and Est1 no longer bound preferentially to a short telomere in pif1 mutant cells while binding of Yku80, a telomere structural protein, was unaffected by the status of the PIF1 locus. Two experiments demonstrate that Pif1 binding is affected by telomere length: Pif1 (but not Yku80) -associated telomeres were 70 bps longer than bulk telomeres, and in the inducible short telomere assay, Pif1 bound better to wild type length telomeres than to short telomeres. Thus, preferential lengthening of short yeast telomeres is achieved in part by targeting the negative regulator Pif1 to long telomeres. PMID:25906395

  1. Isolation of telomere DNA from Neurospora crassa.

    PubMed Central

    Schechtman, M G

    1987-01-01

    The most distal known gene on Neurospora crassa linkage group VR, his-6, was cloned. A genomic walk resulted in isolation of the telomere at VR. It was obtained from a library in which the endmost nucleotides of the chromosome had not been removed by nuclease treatment before being cloned, and mapping indicates that the entire chromosome end has probably been cloned. Sequences homologous to the terminal 2.5 kilobases of DNA from VR from these Oak Ridge N. crassa strains are found at other sites in the genome. To characterize these sites, I crossed an Oak Ridge-derived his-6 strain with a wild-type strain of different genetic background (Mauriceville) and characterized the hybridization patterns seen in the progeny. It appears that the sequences homologous to the VR terminus are found at genetically different sites in the two parental strains, and no hybridization to the VR telomere from Mauriceville was detected. The other genomic copies identified in the Oak Ridge parent were not telomeres. I suggest that any repeating sequence blocks found immediately adjacent to the VR terminus in Oak Ridge strains must be small and that the repeating element identified in that background may be an N. crassa transposable element integrated near the the chromosome end at VR. Images PMID:2890097

  2. ATRX represses alternative lengthening of telomeres.

    PubMed

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

    2015-06-30

    The unlimited proliferation of cancer cells requires a mechanism to prevent telomere shortening. Alternative Lengthening of Telomeres (ALT) is an homologous recombination-mediated mechanism of telomere elongation used in tumors, including osteosarcomas, soft tissue sarcoma subtypes, and glial brain tumors. Mutations in the ATRX/DAXX chromatin remodeling complex have been reported in tumors and cell lines that use the ALT mechanism, suggesting that ATRX may be an ALT repressor. We show here that knockout or knockdown of ATRX in mortal cells or immortal telomerase-positive cells is insufficient to activate ALT. Notably, however, in SV40-transformed mortal fibroblasts ATRX loss results in either a significant increase in the proportion of cell lines activating ALT (instead of telomerase) or in a significant decrease in the time prior to ALT activation. These data indicate that loss of ATRX function cooperates with one or more as-yet unidentified genetic or epigenetic alterations to activate ALT. Moreover, transient ATRX expression in ALT-positive/ATRX-negative cells represses ALT activity. These data provide the first direct, functional evidence that ATRX represses ALT. PMID:26001292

  3. The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length.

    PubMed

    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. PMID:27449056

  4. The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length

    PubMed Central

    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.

    2016-01-01

    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. PMID:27449056

  5. Senescence-Induced Oxidative Stress Causes Endothelial Dysfunction.

    PubMed

    Bhayadia, Raj; Schmidt, Bernhard M W; Melk, Anette; Hömme, Meike

    2016-02-01

    Age is a risk factor for cardiovascular disease, suggesting a causal relationship between age-related changes and vascular damage. Endothelial dysfunction is an early pathophysiological hallmark in the development of cardiovascular disease. Senescence, the cellular equivalent of aging, was proposed to be involved in endothelial dysfunction, but functional data showing a causal relationship are missing.Endothelium-dependent vasodilation was measured in aortic rings ex vivo. We investigated aortas from aged C57Bl/6 mice (24-28 months), in which p16 (INK4a) and p19 (ARF) expression, markers of stress-induced senescence, were significantly induced compared to young controls (4-6 months). To reflect telomere shortening in human aging, we investigated aortas from telomerase deficient (Terc(-/-)) mice of generation 3 (G3). Endothelium-dependent vasodilation in aged wildtype and in Terc(-/-) G3 mice was impaired. A combination of the superoxide dismutase mimetic 1-Oxyl-2,2,6, 6-tetramethyl-4-hydroxypiperidine (TEMPOL) and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin significantly improved endothelium-dependent vasodilation in aged wildtype and Terc(-/-) G3 mice compared to untreated controls. We show that both, aging and senescence induced by telomere shortening, cause endothelial dysfunction that can be restored by antioxidants, indicating a role for oxidative stress. The observation that cellular senescence is a direct signalling event leading to endothelial dysfunction holds the potential to develop new targets for the prevention of cardiovascular disease. PMID:25735595

  6. Dysfunctional voiding.

    PubMed

    Chiozza, M L

    2002-01-01

    Wetting may be considered the Cinderella of paediatric medicine. Before discussing dysfunctional voiding, the milestones of the normal development of continence in the child and the definitions used to describe this topic are presented. Bladder storage requires (1): accommodation of increasing volumes of urine at low intravesical pressure and with appropriate sensation; (2): a bladder outlet that is closed and not modified during increase in intra-abdominal pressure; (3): absence of involuntary bladder contractions. Development of continence in the child involves three independent factors maturing concomitantly: (1) development of normal bladder capacity; (2) maturation of urethral sphincter function; (3) development of neural control over bladder-sphincter function. All these processes are discussed. Abnormalities of any of these maturational sequences, which run parallel and overlapping, may result in clinically evident abnormalities of bladder sphincter control. Although dysfunctional voiding (DV) in children is very common its prevalence has not been well studied and, to date, and its origin is not well known. In a correct evaluation of functional voiding we must take into account different elements: the bladder capacity (that increases during the first 8 years of life roughly 30 ml per year), the micturition frequency, post-void residual volumes, bladder dynamics, urinary flow rates. Thus the correct assessment of children with lower urinary tract dysfunction should include a detailed history. Signs of DV range from urge syndrome to complex incontinence patterns during the day and the night. In addition to incontinence problems, children may have frequency, urgency, straining to void, weak or interrupted urinary stream, urinary tract infections (UTIs) and chronic constipation with or without encopresis. DV are also referred in enuretic children who wet the bed more than one time per night and have a functional bladder capacity lower than attended for age

  7. Human telomeric G-quadruplex: thermodynamic and kinetic studies of telomeric quadruplex stability

    PubMed Central

    Chaires, Jonathan B.

    2010-01-01

    Summary Thermodynamic and kinetic studies complement high-resolution structures of G-quadruplexes. Such studies are essential for a thorough understanding of the mechanisms that govern quadruplex folding and conformational changes in quadruplexes. This perspective article reviews representative thermodynamic and kinetic studies of the folding of human telomeric quadruplex structures. Published thermodynamic data vary widely and are inconsistent. Possible reasons for these inconsistencies are discussed. The key issue of whether or not such folding reactions are a simple two-state process is examined. A tentative energy balance for the folding of telomeric quadruplexes in Na+ and K+ solution, and for conformational transition between these forms will be presented. PMID:19951355

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

    PubMed

    Maeda, Junko; Yurkon, Charles R; Fujisawa, Hiroshi; Kaneko, Masami; Genet, Stefan C; Roybal, Erica J; Rota, Garrett W; Saffer, Ethan R; Rose, Barbara J; Hanneman, William H; Thamm, Douglas H; Kato, Takamitsu A

    2012-01-01

    Canine osteosarcoma (OSA) is known to present with highly variable and chaotic karyotypes, including hypodiploidy, hyperdiploidy, and increased numbers of metacentric chromosomes. The spectrum of genomic instabilities in canine OSA has significantly augmented the difficulty in clearly defining the biological and clinical significance of the observed cytogenetic abnormalities. In this study, eight canine OSA cell lines were used to investigate telomere fusions by fluorescence in situ hybridization (FISH) using a peptide nucleotide acid probe. We characterized each cell line by classical cytogenetic studies and cellular phenotypes including telomere associated factors and then evaluated correlations from this data. All eight canine OSA cell lines displayed increased abnormal metacentric chromosomes and exhibited numerous telomere fusions and interstitial telomeric signals. Also, as evidence of unstable telomeres, colocalization of γ-H2AX and telomere signals in interphase cells was observed. Each cell line was characterized by a combination of data representing cellular doubling time, DNA content, chromosome number, metacentric chromosome frequency, telomere signal level, cellular radiosensitivity, and DNA-PKcs protein expression level. We have also studied primary cultures from 10 spontaneous canine OSAs. Based on the observation of telomere aberrations in those primary cell cultures, we are reasonably certain that our observations in cell lines are not an artifact of prolonged culture. A correlation between telomere fusions and the other characteristics analyzed in our study could not be identified. However, it is important to note that all of the canine OSA samples exhibiting telomere fusion utilized in our study were telomerase positive. Pending further research regarding telomerase negative canine OSA cell lines, our findings may suggest telomere fusions can potentially serve as a novel marker for canine OSA. PMID:22916246

  9. Telomere length in inherited bone marrow failure syndromes.

    PubMed

    Alter, Blanche P; Giri, Neelam; Savage, Sharon A; Rosenberg, Philip S

    2015-01-01

    Telomeres are long DNA repeats and a protein complex at chromosome ends that are essential for genome integrity. Telomeres are very short in patients with dyskeratosis congenita due to germline mutations in telomere biology genes. We compared telomere length in patients with Fanconi anemia, Diamond-Blackfan anemia and Shwachman-Diamond syndrome with telomere length in dyskeratosis congenita. Telomere length was measured in six leukocyte subsets by automated multicolor flow fluorescence in situ hybridization, and age-adjusted using Z-scores (-2.326 = 1(st) percentile) were created. We examined individual data, and used canonical variate analysis for group comparisons and outlier detection. Most dyskeratosis congenita telomere lengths were below the 1(st) percentile, while only 2 Fanconi anemia and one each Diamond-Blackfan anemia and Shwachman-Diamond syndrome were that low. However, Fanconi anemia, Diamond-Blackfan anemia and Shwachman-Diamond syndrome clustered in the bottom half of the normal range. Canonical variate analysis separated dyskeratosis congenita widely from the other three syndromes by the first canonical variable (89.7% of the variance); the second variable (10.0%) separated Diamond-Blackfan anemia, Shwachman-Diamond syndrome, and Fanconi anemia from each other. Overall, unlike in dyskeratosis congenita, telomere lengths in patients with non-dyskeratosis congenita inherited bone marrow failure syndromes were usually in the normal range, albeit shorter than in unaffected individuals. Clinicaltrials.gov identifier: 00027274. PMID:25304614

  10. Stress induced telomere shortening: longer life with less mutations?

    PubMed Central

    2014-01-01

    Background Mutations accumulate as a result of DNA damage and imperfect DNA repair machinery. In higher eukaryotes the accumulation and spread of mutations is limited in two primary ways: through p53-mediated programmed cell death and cellular senescence mediated by telomeres. Telomeres shorten at every cell division and cell stops dividing once the shortest telomere reaches a critical length. It has been shown that the rate of telomere attrition is accelerated when cells are exposed to DNA damaging agents. However the implications of this mechanism are not fully understood. Results With the help of in silico model we investigate the effect of genotoxic stress on telomere attrition and apoptosis in a population of non-identical replicating cells. When comparing the populations of cells with constant vs. stress-induced rate of telomere shortening we find that stress induced telomere shortening (SITS) increases longevity while reducing mutation rate. Interestingly, however, the effect takes place only when genotoxic stresses (e.g. reactive oxygen species due to metabolic activity) are distributed non-equally among cells. Conclusions Our results for the first time show how non-equal distribution of metabolic load (and associated genotoxic stresses) combined with stress induced telomere shortening can delay aging and minimize mutations. PMID:24580844

  11. Telomere Dynamics in Human Cells Reprogrammed to Pluripotency

    PubMed Central

    Suhr, Steven T.; Chang, Eun Ah; Rodriguez, Ramon M.; Wang, Kai; Ross, Pablo J.; Beyhan, Zeki; Murthy, Shashanka; Cibelli, Jose B.

    2009-01-01

    Background Human induced pluripotent stem cells (IPSCs) have enormous potential in the development of cellular models of human disease and represent a potential source of autologous cells and tissues for therapeutic use. A question remains as to the biological age of IPSCs, in particular when isolated from older subjects. Studies of cloned animals indicate that somatic cells reprogrammed to pluripotency variably display telomere elongation, a common indicator of cell “rejuvenation.” Methodology/Principal Findings We examined telomere lengths in human skin fibroblasts isolated from younger and older subjects, fibroblasts converted to IPSCs, and IPSCs redifferentiated through teratoma formation and explant culture. In IPSCs analyzed at passage five (P5), telomeres were significantly elongated in 6/7 lines by >40% and approximated telomere lengths in human embryonic stem cells (hESCs). In cell lines derived from three IPSC-teratoma explants cultured to P5, two displayed telomeres shortened to lengths similar to input fibroblasts while the third line retained elongated telomeres. Conclusions/Significance While these results reveal some heterogeneity in the reprogramming process with respect to telomere length, human somatic cells reprogrammed to pluripotency generally displayed elongated telomeres that suggest that they will not age prematurely when isolated from subjects of essentially any age. PMID:19956585

  12. Telomere length in inherited bone marrow failure syndromes

    PubMed Central

    Alter, Blanche P.; Giri, Neelam; Savage, Sharon A.; Rosenberg, Philip S.

    2015-01-01

    Telomeres are long DNA repeats and a protein complex at chromosome ends that are essential for genome integrity. Telomeres are very short in patients with dyskeratosis congenita due to germline mutations in telomere biology genes. We compared telomere length in patients with Fanconi anemia, Diamond-Blackfan anemia and Shwachman-Diamond syndrome with telomere length in dyskeratosis congenita. Telomere length was measured in six leukocyte subsets by automated multicolor flow fluorescence in situ hybridization, and age-adjusted using Z-scores (−2.326 = 1st percentile) were created. We examined individual data, and used canonical variate analysis for group comparisons and outlier detection. Most dyskeratosis congenita telomere lengths were below the 1st percentile, while only 2 Fanconi anemia and one each Diamond-Blackfan anemia and Shwachman-Diamond syndrome were that low. However, Fanconi anemia, Diamond-Blackfan anemia and Shwachman-Diamond syndrome clustered in the bottom half of the normal range. Canonical variate analysis separated dyskeratosis congenita widely from the other three syndromes by the first canonical variable (89.7% of the variance); the second variable (10.0%) separated Diamond-Blackfan anemia, Shwachman-Diamond syndrome, and Fanconi anemia from each other. Overall, unlike in dyskeratosis congenita, telomere lengths in patients with non-dyskeratosis congenita inherited bone marrow failure syndromes were usually in the normal range, albeit shorter than in unaffected individuals. clinicaltrials.gov identifier: 00027274 PMID:25304614

  13. A role for heterochromatin protein 1γ at human telomeres

    PubMed Central

    Canudas, Silvia; Houghtaling, Benjamin R.; Bhanot, Monica; Sasa, Ghadir; Savage, Sharon A.; Bertuch, Alison A.; Smith, Susan

    2011-01-01

    Human telomere function is mediated by shelterin, a six-subunit complex that is required for telomere replication, protection, and cohesion. TIN2, the central component of shelterin, has binding sites to three subunits: TRF1, TRF2, and TPP1. Here we identify a fourth partner, heterochromatin protein 1γ (HP1γ), that binds to a conserved canonical HP1-binding motif, PXVXL, in the C-terminal domain of TIN2. We show that HP1γ localizes to telomeres in S phase, where it is required to establish/maintain cohesion. We further demonstrate that the HP1-binding site in TIN2 is required for sister telomere cohesion and can impact telomere length maintenance by telomerase. Remarkably, the PTVML HP1-binding site is embedded in the recently identified cluster of mutations in TIN2 that gives rise to dyskeratosis congenita (DC), an inherited bone marrow failure syndrome caused by defects in telomere maintenance. We show that DC-associated mutations in TIN2 abrogate binding to HP1γ and that DC patient cells are defective in sister telomere cohesion. Our data indicate a novel requirement for HP1γ in the establishment/maintenance of cohesion at human telomeres and, furthermore, may provide insight into the mechanism of pathogenesis in TIN2-mediated DC. PMID:21865325

  14. Socioecological variables predict telomere length in wild spotted hyenas.

    PubMed

    Lewin, Nora; Treidel, Lisa A; Holekamp, Kay E; Place, Ned J; Haussmann, Mark F

    2015-02-01

    Telomeres are regarded as important biomarkers of ageing and serve as useful tools in revealing how stress acts at the cellular level. However, the effects of social and ecological factors on telomere length remain poorly understood, particularly in free-ranging mammals. Here, we investigated the influences of within-group dominance rank and group membership on telomere length in wild adult spotted hyenas (Crocuta crocuta). We found large effects of both factors; high-ranking hyenas exhibited significantly greater mean telomere length than did subordinate animals, and group membership significantly predicted mean telomere length within high-ranking females. We further inquired whether prey availability mediates the observed effect of group membership on telomere length, but this hypothesis was not supported. Interestingly, adult telomere length was not predicted by age. Our work shows for the first time, to the best of our knowledge, the effects of social rank on telomere length in a wild mammal and enhances our understanding of how social and ecological variables may contribute to organismal senescence. PMID:25716089

  15. Telomeres, Early-Life Stress and Mental Illness

    PubMed Central

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

    2015-01-01

    Telomeres are structures of tandem TTAGGG repeats at the ends of chromosomes which preserve the encoding DNA by serving as a disposable brake to terminate DNA duplication during chromosome replication. In this process, the telomere itself shortens with each cell division, and can consequently be thought of as a cellular “clock” reflecting the age of a cell and the time until senescence. Telomere shortening, and changes in levels of telomerase, the enzyme that maintains telomeres, occur in the context of certain somatic diseases and in response to selected physical stressors. Emerging evidence indicates that telomeres shorten with exposure to psychosocial stress (including early-life stress [ELS]), and perhaps in association with some psychiatric disorders. These discoveries suggest that telomere shortening might be a useful biomarker for the overall stress response of an organism to various pathogenic conditions. In this regard, telomeres and their response to both somatic and psychiatric illness could serve as a unifying biomarker of stress response that crosses the brain/body distinction often made in medicine. Prospective studies will help to clarify whether this biomarker has broad utility in psychiatry and medicine in the evaluation of responses to psychosocial stressors. The possibility that telomere shortening can be slowed or reversed by psychiatric and psychosocial interventions could represent an opportunity for developing novel preventative and therapeutic approaches. PMID:25832516

  16. Structure of mammalian respiratory complex I.

    PubMed

    Zhu, Jiapeng; Vinothkumar, Kutti R; Hirst, Judy

    2016-08-18

    Complex I (NADH:ubiquinone oxidoreductase), one of the largest membrane-bound enzymes in the cell, powers ATP synthesis in mammalian mitochondria by using the reducing potential of NADH to drive protons across the inner mitochondrial membrane. Mammalian complex I (ref. 1) contains 45 subunits, comprising 14 core subunits that house the catalytic machinery (and are conserved from bacteria to humans) and a mammalian-specific cohort of 31 supernumerary subunits. Knowledge of the structures and functions of the supernumerary subunits is fragmentary. Here we describe a 4.2-Å resolution single-particle electron cryomicroscopy structure of complex I from Bos taurus. We have located and modelled all 45 subunits, including the 31 supernumerary subunits, to provide the entire structure of the mammalian complex. Computational sorting of the particles identified different structural classes, related by subtle domain movements, which reveal conformationally dynamic regions and match biochemical descriptions of the 'active-to-de-active' enzyme transition that occurs during hypoxia. Our structures therefore provide a foundation for understanding complex I assembly and the effects of mutations that cause clinically relevant complex I dysfunctions, give insights into the structural and functional roles of the supernumerary subunits and reveal new information on the mechanism and regulation of catalysis. PMID:27509854

  17. Assembly of telomeric chromatin to create ALTernative endings.

    PubMed

    O'Sullivan, Roderick J; Almouzni, Genevieve

    2014-11-01

    Circumvention of the telomere length-dependent mechanisms that control the upper boundaries of cellular proliferation is necessary for the unlimited growth of cancer. Most cancer cells achieve cellular immortality by up-regulating the expression of telomerase to extend and maintain their telomere length. However, a small but significant number of cancers do so via the exchange of telomeric DNA between chromosomes in a pathway termed alternative lengthening of telomeres, or ALT. Although it remains to be clarified why a cell chooses the ALT pathway and how ALT is initiated, recently identified mutations in factors that shape the chromatin and epigenetic landscape of ALT telomeres are shedding light on these mechanisms. In this review, we examine these recent findings and integrate them into the current models of the ALT mechanism. PMID:25172551

  18. Computing the Length of the Shortest Telomere in the Nucleus

    NASA Astrophysics Data System (ADS)

    Dao Duc, K.; Holcman, D.

    2013-11-01

    The telomere length can either be shortened or elongated by an enzyme called telomerase after each cell division. Interestingly, the shortest telomere is involved in controlling the ability of a cell to divide. Yet, its dynamics remains elusive. We present here a stochastic approach where we model this dynamics using a Markov jump process. We solve the forward Fokker-Planck equation to obtain the steady state distribution and the statistical moments of telomere lengths. We focus specifically on the shortest one and we estimate its length difference with the second shortest telomere. After extracting key parameters such as elongation and shortening dynamics from experimental data, we compute the length of telomeres in yeast and obtain as a possible prediction the minimum concentration of telomerase required to ensure a proper cell division.

  19. Keeping It in the Family: ATRX Loss Promotes Persistent Sister Telomere Cohesion in ALT Cancer Cells.

    PubMed

    Roake, Caitlin M; Artandi, Steven E

    2015-09-14

    In this issue of Cancer Cell, Ramamoorthy and Smith report that cancer cells that maintain their chromosome ends through alternative lengthening of telomeres (ALT) display persistent sister telomere cohesion. This delayed resolution of sister telomere cohesion depends upon the loss of ATRX and its histone-sequestering function and is associated with increased recombination between sister telomeres. PMID:26373274

  20. QTL mapping and candidate gene analysis of telomere length control factors in maize (Zea mays L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Telomere length is under genetic control and important for essential telomere functions. Failure to regulate telomere length homeostasis contributes to cancers and aging-related diseases in animals, but the effects of telomere length defects in plants remains poorly understood. To learn more about t...

  1. Characterization of telomeres and telomerase expression in Xiphophorus.

    PubMed

    Downs, Kevin P; Shen, Yingjia; Pasquali, Amanda; Beldorth, Ion; Savage, Markita; Gallier, Katelyn; Garcia, Tzintzuni; Booth, Rachell E; Walter, Ronald B

    2012-01-01

    Research investigating telomere lengths and telomerase expression in vertebrates has progressively become important due to the association of these two biological endpoints with cellular aging and cancer in humans. Studies that rely upon the traditional use of laboratory mice have been faced with limitations largely due to inbred mice possessing large telomeres and ubiquitous expression of telomerase. Recently, a number of small fish species have been shown to provide potentially informative models for examining the role of telomeres and telomerase within intact vertebrate animals. Xiphophorus fishes represent a new world live-bearing genus that has not previously been assessed for telomere length or telomerase expression. To add to the knowledge base of telomere and telomerase biology in vertebrates we assessed telomere length and telomerase expression among several species of Xiphophorus. The telomere lengths in several organs (gill, brain, eyes, testis, ovary and liver) in three species (Xiphophorus hellerii, Xiphophorus maculatus, Xiphophorus couchianus) and also in F(1) interspecies hybrids were approximately 2-6 kb. This size was consistent within the same organs of the same species, as well as between species and F(1) hybrids. Despite possessing relatively short telomere lengths compared to humans, the consistency of size among Xiphophorus species and organs may allow experimental detection of telomere shortening. The relative expression of telomerase reverse transcriptase (TERT) was determined by quantitative real-time PCR. Expression levels of TERT was measured in seven organs (ovary, testis, liver, gill, brain, heart, skin) from X. maculatus, X. hellerii and in control and ultraviolet light (UVB) exposed skin samples from X. maculatus, X. hellerii, and F(1) interspecies hybrids. TERT gene expression was significantly higher in ovary and testis, while all other organs showed low relative TERT expression. Detectable increases in TERT expression were found

  2. Finding a place in the SUN: telomere maintenance in a diverse nuclear landscape.

    PubMed

    Ebrahimi, Hani; Cooper, Julia Promisel

    2016-06-01

    Telomeres function in the context of a complex nuclear milieu in which telomeres tend to occupy distinct subnuclear regions. Indeed, regulation of the subnuclear positioning of telomeres is conserved from yeast to human, raising the age-old question: to what extent is location important for function? In mitotically dividing cells, the positioning of telomeres affects their epigenetic state and influences telomere processing and synthesis. In meiotic cells, telomere location is important for homologue pairing, centromere assembly and spindle formation. Here we focus on recent insights into the functions of telomere positioning in maintaining genome integrity. PMID:27064212

  3. Integration of Telomere Length Dynamics into Systems Biology Framework: A Review.

    PubMed

    Nersisyan, Lilit

    2016-01-01

    Telomere length dynamics plays a crucial role in regulation of cellular processes and cell fate. In contrast to epidemiological studies revealing the association of telomere length with age, age-related diseases, and cancers, the role of telomeres in regulation of transcriptome and epigenome and the role of genomic variations in telomere lengthening are not extensively analyzed. This is explained by the fact that experimental assays for telomere length measurement are resource consuming, and there are very few studies where high-throughput genomics, transcriptomics, and/or epigenomics experiments have been coupled with telomere length measurements. Recent development of computational approaches for assessment of telomere length from whole genome sequencing data pave a new perspective on integration of telomeres into high-throughput systems biology analysis framework. Herein, we review existing methodologies for telomere length measurement and compare them to computational approaches, as well as discuss their applications in large-scale studies on telomere length dynamics. PMID:27346946

  4. Integration of Telomere Length Dynamics into Systems Biology Framework: A Review

    PubMed Central

    Nersisyan, Lilit

    2016-01-01

    Telomere length dynamics plays a crucial role in regulation of cellular processes and cell fate. In contrast to epidemiological studies revealing the association of telomere length with age, age-related diseases, and cancers, the role of telomeres in regulation of transcriptome and epigenome and the role of genomic variations in telomere lengthening are not extensively analyzed. This is explained by the fact that experimental assays for telomere length measurement are resource consuming, and there are very few studies where high-throughput genomics, transcriptomics, and/or epigenomics experiments have been coupled with telomere length measurements. Recent development of computational approaches for assessment of telomere length from whole genome sequencing data pave a new perspective on integration of telomeres into high-throughput systems biology analysis framework. Herein, we review existing methodologies for telomere length measurement and compare them to computational approaches, as well as discuss their applications in large-scale studies on telomere length dynamics. PMID:27346946

  5. Interstitial telomeric sequences in human chromosomes cluster with common fragile sites, mutagen sensitive sites, viral integration sites, cancer breakpoints, proto-oncogenes and breakpoints involved in primate evolution

    SciTech Connect

    Adekunle, S.S.A.; Wyandt, H.; Mark, H.F.L.

    1994-09-01

    Recently we mapped the telomeric repeat sequences to 111 interstitial sites in the human genome and to sites of gaps and breaks induced by aphidicolin and sister chromatid exchange sites detected by BrdU. Many of these sites correspond to conserved fragile sites in man, gorilla and chimpazee, to sites of conserved sister chromatid exchange in the mammalian X chromosome, to mutagenic sensitive sites, mapped locations of proto-oncogenes, breakpoints implicated in primate evolution and to breakpoints indicated as the sole anomaly in neoplasia. This observation prompted us to investigate if the interstitial telomeric sites cluster with these sites. An extensive literature search was carried out to find all the available published sites mentioned above. For comparison, we also carried out a statistical analysis of the clustering of the sites of the telomeric repeats with the gene locations where only nucleotide mutations have been observed as the only chromosomal abnormality. Our results indicate that the telomeric repeats cluster most with fragile sites, mutagenic sensitive sites and breakpoints implicated in primate evolution and least with cancer breakpoints, mapped locations of proto-oncogenes and other genes with nucleotide mutations.

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

    SciTech Connect

    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.

  7. Correlation of Chromosomal Instability, Telomere Length and Telomere Maintenance in Microsatellite Stable Rectal Cancer: A Molecular Subclass of Rectal Cancer

    PubMed Central

    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

    Introduction 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. Experimental Design 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. Results 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). Conclusions 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. PMID:24278232

  8. Telomeres Cluster De Novo before the Initiation of Synapsis: A Three-dimensional Spatial Analysis of Telomere Positions before and during Meiotic Prophase

    PubMed Central

    Bass, Hank W.; Marshall, Wallace F.; Sedat, John W.; Agard, David A.; Cande, W. Zacheus

    1997-01-01

    We have analyzed the progressive changes in the spatial distribution of telomeres during meiosis using three-dimensional, high resolution fluorescence microscopy. Fixed meiotic cells of maize (Zea mays L.) were subjected to in situ hybridization under conditions that preserved chromosome structure, allowing identification of stage-dependent changes in telomere arrangements. We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres. Quantitative measurements on the spatial arrangements of telomeres revealed that, as cells passed through premeiotic interphase and into leptotene, there was an increase in the frequency of large telomere-to-telomere distances and a decrease in the bias toward peripheral localization of telomeres. By leptotene, there was no obvious evidence of telomere grouping, and the large, singular nucleolus was internally located, nearly concentric with the nucleus. At the end of leptotene, telomeres clustered de novo at the nuclear periphery, coincident with a displacement of the nucleolus to one side. The telomere cluster persisted throughout zygotene and into early pachytene. The nucleolus was adjacent to the cluster at zygotene. At the pachytene stage, telomeres rearranged again by dispersing throughout the nuclear periphery. The stagedependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions. Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over. PMID:9105032

  9. Multiple Pathways Suppress Telomere Addition to DNA Breaks in the Drosophila Germline

    PubMed Central

    Beaucher, Michelle; Zheng, Xiao-Feng; Amariei, Flavia; Rong, Yikang S.

    2012-01-01

    Telomeres protect chromosome ends from being repaired as double-strand breaks (DSBs). Just as DSB repair is suppressed at telomeres, de novo telomere addition is suppressed at the site of DSBs. To identify factors responsible for this suppression, we developed an assay to monitor de novo telomere formation in Drosophila, an organism in which telomeres can be established on chromosome ends with essentially any sequence. Germline expression of the I-SceI endonuclease resulted in precise telomere formation at its cut site with high efficiency. Using this assay, we quantified the frequency of telomere formation in different genetic backgrounds with known or possible defects in DNA damage repair. We showed that disruption of DSB repair factors (Rad51 or DNA ligase IV) or DSB sensing factors (ATRIP or MDC1) resulted in more efficient telomere formation. Interestingly, partial disruption of factors that normally regulate telomere protection (ATM or NBS) also led to higher frequencies of telomere formation, suggesting that these proteins have opposing roles in telomere maintenance vs. establishment. In the ku70 mutant background, telomere establishment was preceded by excessive degradation of DSB ends, which were stabilized upon telomere formation. Most strikingly, the removal of ATRIP caused a dramatic increase in telomeric retrotransposon attachment to broken ends. Our study identifies several pathways thatsuppress telomere addition at DSBs, paving the way for future mechanistic studies. PMID:22446318

  10. Replication factor C recognizes 5'-phosphate ends of telomeres.

    PubMed

    Uchiumi, F; Ohta, T; Tanuma, S

    1996-12-01

    Telomere structure is suggested to be important for chromosome and cell integrity and thereby for cell senescence and immortality. In a search for cDNA encoding proteins that bind specifically to telomere repeat sequences, we used random primer-labeled telomere probes to screen a lambda gt11 Jurkat cDNA library. The clone obtained encodes the central region of the large subunit of replication factor C (RFC), a known activator of DNA polymerase delta. Electrophoretic mobility shift analyses of the binding ability of RFC-glutathione S-transferase (GST) fusion protein to telomere probes revealed that RFC recognizes preferentially 5'-phosphoryl (P) groups but not 3'-hydroxyl (OH) groups at the ends of double-stranded telomere repeats. This structure-specific binding of RFC is supported by the observations that it binds to 3'-OH/5'-P ends in telomere repeats produced by DNase gamma, but not to those produced by 3'-P/5'-OH ends for DNase alpha. These findings suggest a novel function for RFC in telomere stability or turnover. PMID:8954124

  11. Telomere analysis by fluorescence in situ hybridization and flow cytometry.

    PubMed Central

    Hultdin, M; Grönlund, E; Norrback, K; Eriksson-Lindström, E; Just, T; Roos, G

    1998-01-01

    Determination of telomere length is traditionally performed by Southern blotting and densitometry, giving a mean telomere restriction fragment (TRF) value for the total cell population studied. Fluorescence in situ hybridization (FISH) of telomere repeats has been used to calculate telomere length, a method called quantitative (Q)-FISH. We here present a quantitative flow cytometric approach, Q-FISHFCM, for evaluation of telomere length distribution in individual cells based on in situ hybridization using a fluorescein-labeled peptide nucleic acid (PNA) (CCCTAA)3probe and DNA staining with propidium iodide. A simple and rapid protocol with results within 30 h was developed giving high reproducibility. One important feature of the protocol was the use of an internal cell line control, giving an automatic compensation for potential differences in the hybridization steps. This protocol was tested successfully on cell lines and clinical samples from bone marrow, blood, lymph nodes and tonsils. A significant correlation was found between Southern blotting and Q-FISHFCMtelomere length values ( P = 0.002). The mean sub-telomeric DNA length of the tested cell lines and clinical samples was estimated to be 3.2 kbp. With the Q-FISHFCMmethod the fluorescence signal could be determined in different cell cycle phases, indicating that in human cells the vast majority of telomeric DNA is replicated early in S phase. PMID:9685479

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

    PubMed

    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. PMID:26028466

  13. Telomere attrition in beta and alpha cells with age.

    PubMed

    Tamura, Yoshiaki; Izumiyama-Shimomura, Naotaka; Kimbara, Yoshiyuki; Nakamura, Ken-Ichi; Ishikawa, Naoshi; Aida, Junko; Chiba, Yuko; Matsuda, Yoko; Mori, Seijiro; Arai, Tomio; Fujiwara, Mutsunori; Poon, Steven Ss; Ishizaki, Tatsuro; Araki, Atsushi; Takubo, Kaiyo; Ito, Hideki

    2016-06-01

    We have reported telomere attrition in β and α cells of the pancreas in elderly patients with type 2 diabetes, but it has not been explored how the telomere lengths of these islet cells change according to age in normal subjects. To examine the telomere lengths of β and α cells in individuals without diabetes across a wide range of ages, we conducted measurement of the telomere lengths of human pancreatic β and α cells obtained from 104 autopsied subjects without diabetes ranging in age from 0 to 100 years. As an index of telomere lengths, the normalized telomere-centromere ratio (NTCR) was determined for β (NTCRβ) and α (NTCRα) cells by quantitative fluorescence in situ hybridization (Q-FISH). We found NTCRβ and NTCRα showed almost the same levels and both decreased according to age (p < 0.001 for both). NTCRs decreased more rapidly with age and were more widely distributed (p = 0.036 for NTCRβ, p < 0.001 for NTCRα) in subjects under 18 years of age than in subjects over 18 years. There was a positive correlation between NTCRβ and NTCRα only among adult subjects (p < 0.001). In conclusion, the telomeres of β and α cells become shortened with normal aging process. PMID:27216158

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

    PubMed Central

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

    PubMed

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

    2016-07-01

    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

  16. Telomerase Efficiently Elongates Highly Transcribing Telomeres in Human Cancer Cells

    PubMed Central

    Arora, Rajika; Lorenzi, Luca E.; Azzalin, Claus M.

    2012-01-01

    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. PMID:22558207

  17. A Model of Canine Leukocyte Telomere Dynamics

    PubMed Central

    Benetos, Athanase; Kimura, Masayuki; Labat, Carlos; Buchoff, Gerald M.; Huber, Shell; Labat, Laura; Lu, Xiaobin; Aviv, Abraham

    2011-01-01

    Summary Recent studies have found associations of leukocyte telomere length (TL) with diseases of aging and with longevity. However, it is unknown whether birth leukocyte TL or its age-dependent attrition— the two factors that determine leukocyte TL dynamics— explains these associations, since acquiring this information entails monitoring individuals over their entire life course. We tested in dogs a model of leukocyte TL dynamics, based on the following premises: (i) TL is synchronized among somatic tissues; (ii) TL in skeletal muscle, which is largely post-mitotic, is a measure of TL in early development; (iii) the difference between TL in leukocytes and muscle (ΔLMTL) is the extent of leukocyte TL shortening since early development. Using this model, we observed in 83 dogs (ages 4–42 months) no significant change with age in TLs of skeletal muscle and a shorter TL in leukocytes than in skeletal muscle (P<0.0001). Age explained 43% of the variation in ΔLMTL (P<0.00001) but only 6% of the variation in leukocyte TL (P=0.035) among dogs. Accordingly, muscle TL and ΔLMTL provide the two essential factors of leukocyte TL dynamics in the individual dog. When applied to humans, the partition of the contribution of leukocyte TL during early development versus telomere shortening afterward might provide information about whether the individual’s longevity is calibrated to either one or both factors that define leukocyte TL dynamics. PMID:21917112

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

    PubMed

    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. PMID:25266121

  19. Mathematical model of alternative mechanism of telomere length maintenance

    NASA Astrophysics Data System (ADS)

    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.

  20. Telomere structure and telomerase in health and disease

    PubMed Central

    GOMEZ, DANIEL E.; ARMANDO, ROMINA G.; FARINA, HERNÁN G.; MENNA, PABLO LORENZANO; CERRUDO, CAROLINA S.; GHIRINGHELLI, P. DANIEL; ALONSO, DANIEL F.

    2012-01-01

    Telomerase is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences. Telomerase activity is exhibited in gametes and stem and tumor cells. In human somatic cells, proliferation potential is strictly limited and senescence follows approximately 50–70 cell divisions. In most tumor cells, on the contrary, replication potential is unlimited. The key role in this process of the system of the telomere length maintenance with involvement of telomerase is still poorly studied. Undoubtedly, DNA polymerase is not capable of completely copying DNA at the very ends of chromosomes; therefore, approximately 50 nucleotides are lost during each cell cycle, which results in gradual telomere length shortening. Critically short telomeres cause senescence, following crisis and cell death. However, in tumor cells the system of telomere length maintenance is activated. Much work has been done regarding the complex telomere/telomerase as a unique target, highly specific in cancer cells. Telomeres have additional proteins that regulate the binding of telomerase. Telomerase, also associates with a number of proteins forming the sheltering complex having a central role in telomerase activity. This review focuses on the structure and function of the telomere/telomerase complex and its altered behavior leading to disease, mainly cancer. Although telomerase therapeutics are not approved yet for clinical use, we can assume that based on the promising in vitro and in vivo results and successful clinical trials, it can be predicted that telomerase therapeutics will be utilized soon in the combat against malignancies and degenerative diseases. The active search for modulators is justified, because the telomere/telomerase system is an extremely promising target offering possibilities to decrease or increase the viability of the cell for therapeutic purposes. PMID:22941386

  1. HTLV-1 positive and negative T cells cloned from infected individuals display telomerase and telomere genes deregulation that predominate in activated but untransformed CD4+ T cells.

    PubMed

    Zane, Linda; Sibon, David; Capraro, Valérie; Galia, Perrine; Karam, Maroun; Delfau-Larue, Marie-Hélène; Gilson, Eric; Gessain, Antoine; Gout, Olivier; Hermine, Olivier; Mortreux, Franck; Wattel, Eric

    2012-08-15

    Untransformed HTLV-1 positive CD4(+) cells from infected individuals are selected for expressing tax and displaying morphological features consistent with telomere dysfunctions. We show that in resting HTLV-1 positive CD4(+) cells cloned from patients, hTERT expression parallels tax expression and cell cycling. Upon activation, these cells dramatically augment tax expression, whereas their increase in telomerase activity is about 20 times lower than that of their uninfected counterpart. Activated HTLV-1 positive CD4(+) but not uninfected CD4(+) or CD8(+) clones also repress the transcription of TRF1, TPP1, TANK1, POT1, DNA-PKc and Ku80. Both infected and uninfected lymphocytes from infected individuals shared common telomere gene deregulations toward a pattern consistent with premature senescence. ATLL cells displayed the highest telomerase activity (TA) whereas recovered a telomere gene transcriptome close to that of normal CD4(+) cells. In conclusion HTLV-1-dependent telomere modulations seem involved in clonal expansion, immunosuppression, tumor initiation and progression. PMID:21717459

  2. ORNL FISH Telomere Segmentation GUI and Instruction Manual

    Energy Science and Technology Software Center (ESTSC)

    2002-12-01

    The ORNL FISH Telomere Segmentation GUI takes images of cellular chromosomes and telomeres obtained through Fluorescent in-situ Hybridization and automatically labels the pixels that belong to the chromosomes and telomeres, which are cellular structures of interest to cancer researchers. The process of labeling the pixels is called segmentation. The resulting segmentation can be edited through the use of an extensive graphical user-interface or GUI, saved, and exported to a data file suitable for use withmore » data analysis programs such as Microsoft Excel.« less

  3. Mammalian cardiolipin biosynthesis.

    PubMed

    Mejia, Edgard M; Nguyen, Hieu; Hatch, Grant M

    2014-04-01

    Cardiolipin is a major phospholipid in mitochondria and is involved in the generation of cellular energy in the form of ATP. In mammalian and eukaryotic cells it is synthesized via the cytidine-5'-diphosphate-1,2-diacyl-sn-glycerol phosphate pathway. This brief review will describe some of the more recent studies on mammalian cardiolipin biosynthesis and provide an overview of regulation of cardiolipin biosynthesis. In addition, the important role that this key phospholipid plays in disease processes including heart failure, diabetes, thyroid hormone disease and the genetic disease Barth Syndrome will be discussed. PMID:24144810

  4. Telomere shortening and telomere position effect in mild ring 17 syndrome

    PubMed Central

    2014-01-01

    Background Ring chromosome 17 syndrome is a rare disease that arises from the breakage and reunion of the short and long arms of chromosome 17. Usually this abnormality results in deletion of genetic material, which explains the clinical features of the syndrome. Moreover, similar phenotypic features have been observed in cases with complete or partial loss of the telomeric repeats and conservation of the euchromatic regions. We studied two different cases of ring 17 syndrome, firstly, to clarify, by analyzing gene expression analysis using real-time qPCR, the role of the telomere absence in relationship with the clinical symptoms, and secondly, to look for a new model of the mechanism of ring chromosome transmission in a rare case of familial mosaicism, through cytomolecular and quantitative fluorescence in-situ hybridization (Q-FISH) investigations. Results The results for the first case showed that the expression levels of genes selected, which were located close to the p and q ends of chromosome 17, were significantly downregulated in comparison with controls. Moreover, for the second case, we demonstrated that the telomeres were conserved, but were significantly shorter than those of age-matched controls; data from segregation analysis showed that the ring chromosome was transmitted only to the affected subjects of the family. Conclusions Subtelomeric gene regulation is responsible for the phenotypic aspects of ring 17 syndrome; telomere shortening influences the phenotypic spectrum of this disease and strongly contributes to the familial transmission of the mosaic ring. Together, these results provide new insights into the genotype-phenotype relationships in mild ring 17 syndrome. PMID:24393457

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

    PubMed Central

    Procházková Schrumpfová, Petra; Schořová, Šárka; Fajkus, Jiří

    2016-01-01

    Telomeres, as physical ends of linear chromosomes, are targets of a number of specific proteins, including primarily telomerase reverse transcriptase. Access of proteins to the telomere may be affected by a number of diverse factors, e.g., protein interaction partners, local DNA or chromatin structures, subcellular localization/trafficking, or simply protein modification. Knowledge of composition of the functional nucleoprotein complex of plant telomeres is only fragmentary. Moreover, the plant telomeric repeat binding proteins that were characterized recently appear to also be involved in non-telomeric processes, e.g., ribosome biogenesis. This interesting finding was not totally unexpected since non-telomeric functions of yeast or animal telomeric proteins, as well as of telomerase subunits, have been reported for almost a decade. Here we summarize known facts about the architecture of plant telomeres and compare them with the well-described composition of telomeres in other organisms. PMID:27446102

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

    PubMed

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

    2015-02-27

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

  7. Measuring telomere length and telomere dynamics in evolutionary biology and ecology

    PubMed Central

    Nussey, Daniel H; Baird, Duncan; Barrett, Emma; Boner, Winnie; Fairlie, Jennifer; Gemmell, Neil; Hartmann, Nils; Horn, Thorsten; Haussmann, Mark; Olsson, Mats; Turbill, Chris; Verhulst, Simon; Zahn, Sandrine; Monaghan, Pat

    2014-01-01

    Telomeres play a fundamental role in the protection of chromosomal DNA and in the regulation of cellular senescence. Recent work in human epidemiology and evolutionary ecology suggests adult telomere length (TL) may reflect past physiological stress and predict subsequent morbidity and mortality, independent of chronological age. Several different methods have been developed to measure TL, each offering its own technical challenges. The aim of this review is to provide an overview of the advantages and drawbacks of each method for researchers, with a particular focus on issues that are likely to face ecologists and evolutionary biologists collecting samples in the field or in organisms that may never have been studied in this context before. We discuss the key issues to consider and wherever possible try to provide current consensus view regarding best practice with regard to sample collection and storage, DNA extraction and storage, and the five main methods currently available to measure TL. Decisions regarding which tissues to sample, how to store them, how to extract DNA, and which TL measurement method to use cannot be prescribed, and are dependent on the biological question addressed and the constraints imposed by the study system. What is essential for future studies of telomere dynamics in evolution and ecology is that researchers publish full details of their methods and the quality control thresholds they employ. PMID:25834722

  8. CpG-island promoters drive transcription of human telomeres

    PubMed Central

    Nergadze, Solomon G.; Farnung, Benjamin O.; Wischnewski, Harry; Khoriauli, Lela; Vitelli, Valerio; Chawla, Raghav; Giulotto, Elena; Azzalin, Claus M.

    2009-01-01

    The longstanding dogma that telomeres, the heterochromatic extremities of linear eukaryotic chromosomes, are transcriptionally silent was overturned by the discovery that DNA-dependent RNA polymerase II (RNAPII) transcribes telomeric DNA into telomeric repeat-containing RNA (TERRA). Here, we show that CpG dinucleotide-rich DNA islands, shared among multiple human chromosome ends, promote transcription of TERRA molecules. TERRA promoters sustain cellular expression of reporter genes, are located immediately upstream of TERRA transcription start sites, and are bound by active RNAPII in vivo. Finally, the identified promoter CpG dinucleotides are methylated in vivo, and cytosine methylation negatively regulates TERRA abundance. The existence of subtelomeric promoters, driving TERRA transcription from independent chromosome ends, supports the idea that TERRA exerts fundamental functions in the context of telomere biology. PMID:19850908

  9. The molecular genetics of the telomere biology disorders.

    PubMed

    Bertuch, Alison A

    2016-08-01

    The importance of telomere function for human health is exemplified by a collection of Mendelian disorders referred to as the telomere biology disorders (TBDs), telomeropathies, or syndromes of telomere shortening. Collectively, the TBDs cover a spectrum of conditions from multisystem disease presenting in infancy to isolated disease presentations in adulthood, most notably idiopathic pulmonary fibrosis. Eleven genes have been found mutated in the TBDs to date, each of which is linked to some aspect of telomere maintenance. This review summarizes the molecular defects that result from mutations in these genes, highlighting recent advances, including the addition of PARN to the TBD gene family and the discovery of heterozygous mutations in RTEL1 as a cause of familial pulmonary fibrosis. PMID:26400640

  10. Telomere sister chromatid exchange in telomerase deficient murine cells

    SciTech Connect

    Wang, Yisong; Giannone, Richard J; Liu, Yie

    2005-01-01

    We have recently demonstrated that several types of genomic rearrangements (i.e., telomere sister chromatid exchange (T-SCE), genomic-SCE, or end-to-end fusions) were more often detected in long-term cultured murine telomerase deficient embryonic stem (ES) cells than in freshly prepared murine splenocytes, even through they possessed similar frequencies of critically short telomeres. The high rate of genomic rearrangements in telomerase deficient ES cells, when compared to murine splenocytes, may reflect the cultured cells' gained ability to protect chromosome ends with eroded telomeres allowing them to escape 'end crisis'. However, the possibility that ES cells were more permissive to genomic rearrangements than other cell types or that differences in the microenvironment or genetic background of the animals might consequentially determine the rate of T-SCEs or other genomic rearrangements at critically short telomeres could not be ruled out.

  11. Mutations in Ran system affected telomere silencing in Saccharomyces cerevisiae

    SciTech Connect

    Hayashi, Naoyuki Kobayashi, Masahiko; Shimizu, Hiroko; Yamamoto, Ken-ichi; Murakami, Seishi; Nishimoto, Takeharu

    2007-11-23

    The Ran GTPase system regulates the direction and timing of several cellular events, such as nuclear-cytosolic transport, centrosome formation, and nuclear envelope assembly in telophase. To gain insight into the Ran system's involvement in chromatin formation, we investigated gene silencing at the telomere in several mutants of the budding yeast Saccharomyces cerevisiae, which had defects in genes involved in the Ran system. A mutation of the RanGAP gene, rna1-1, caused reduced silencing at the telomere, and partial disruption of the nuclear Ran binding factor, yrb2-{delta}2, increased this silencing. The reduced telomere silencing in rna1-1 cells was suppressed by a high dosage of the SIR3 gene or the SIT4 gene. Furthermore, hyperphosphorylated Sir3 protein accumulated in the rna1-1 mutant. These results suggest that RanGAP is required for the heterochromatin structure at the telomere in budding yeast.

  12. Mild oxidative stress is beneficial for sperm telomere length maintenance

    PubMed Central

    Mishra, Swetasmita; Kumar, Rajeev; Malhotra, Neena; Singh, Neeta; Dada, Rima

    2016-01-01

    AIM: To evaluate telomere length in sperm DNA and its correlation with oxidative stress (normal, mild, severe). METHODS: The study included infertile men (n = 112) and age matched fertile controls (n = 102). The average telomere length from the sperm DNA was measured using a quantitative real time PCR based assay. Seminal reactive oxygen species (ROS) and 8-Isoprostane (8-IP) levels were measured by chemiluminescence assay and ELISA respectively. RESULTS: Average sperm telomere length in infertile men and controls was 0.609 ± 0.15 and 0.789 ± 0.060, respectively (P < 0.0001). Seminal ROS levels in infertile was higher [66.61 ± 28.32 relative light units (RLU)/s/million sperm] than in controls (14.04 ± 10.67 RLU/s/million sperm) (P < 0.0001). The 8-IP level in infertile men was significantly higher (421.55 ± 131.29 pg/mL) than in controls (275.94 ± 48.13 pg/mL) (P < 0.001). When correlated to oxidative stress, in normal range of oxidative stress (ROS, 0-21.3 RLU/s/million sperm) the average telomere length in cases was 0.663 ± 0.14, in mild oxidative stress (ROS, 21.3-35 RLU/s/million sperm) it was elevated (0.684 ± 0.12) and in severe oxidative stress (ROS > 35 RLU/s/million sperm) average telomere length was decreased to 0.595 ± 0.15. CONCLUSION: Mild oxidative stress results in lengthening of telomere length, but severe oxidative stress results in shorter telomeres. Although telomere maintenance is a complex trait, the study shows that mild oxidative stress is beneficial in telomere length maintenance and thus a delicate balance needs to be established to maximize the beneficial effects of free radicals and prevent harmful effects of supra physiological levels. Detailed molecular evaluation of telomere structure, its correlation with oxidative stress would aid in elucidating the cause of accelerated telomere length attrition. PMID:27376021

  13. Telomere Fragment Induced Amnion Cell Senescence: A Contributor to Parturition?

    PubMed Central

    Polettini, Jossimara; Behnia, Faranak; Taylor, Brandie D.; Saade, George R.; Taylor, Robert N.; Menon, Ramkumar

    2015-01-01

    Oxidative stress (OS)-induced senescence of the amniochorion has been associated with parturition at term. We investigated whether telomere fragments shed into the amniotic fluid (AF) correlated with labor status and tested if exogenous telomere fragments (T-oligos) could induce human and murine amnion cell senescence. In a cross-sectional clinical study, AF telomere fragment concentrations quantitated by a validated real-time PCR assay were higher in women in labor at term compared to those not in labor. In vitro treatment of primary human amnion epithelial cells with 40 μM T-oligos ([TTAGGG]2) that mimic telomere fragments, activated p38MAPK, produced senescence-associated (SA) β-gal staining and increased interleukin (IL)-6 and IL-8 production compared to cells treated with complementary DNA sequences (Cont-oligos, [AATCCC]2). T-oligos injected into the uteri of pregnant CD1 mice on day 14 of gestation, led to increased p38MAPK, SA-β-gal (SA β-gal) staining in murine amniotic sacs and higher AF IL-8 levels on day 18, compared to saline treated controls. In summary, term labor AF samples had higher telomere fragments than term not in labor AF. In vitro and in situ telomere fragments increased human and murine amnion p38MAPK, senescence and inflammatory cytokines. We propose that telomere fragments released from senescent fetal cells are indicative of fetal cell aging. Based on our data, these telomere fragments cause oxidative stress associated damages to the term amniotic sac and force them to release other DAMPS, which, in turn, provide a sterile immune response that may be one of the many inflammatory signals required to initiate parturition at term. PMID:26397719

  14. [Telomeres and telomerase as targeted therapies in cancer treatment].

    PubMed

    Souiden, Y; Bouraoui, A; Chaieb, K; Mahdouani, K

    2010-09-01

    Advances in chromosome dynamics have increased our understanding of the significant role of telomeres and telomerase in cancer. Telomerase is expressed in almost all cancer cells but is inactive in most normal somatic cells. Therefore, telomerase is an important target for the design of therapeutic agents that might have minimal side effects. Herein, we evaluate current approaches to telomerase/telomere-targeted therapy, discuss the benefits and disadvantages, and speculate on the future direction of telomerase inhibitors as cancer therapeutics. PMID:20663741

  15. Telomere Dynamics and Homeostasis in a Transmissible Cancer

    PubMed Central

    Ujvari, Beata; Pearse, Anne-Maree; Taylor, Robyn; Pyecroft, Stephen; Flanagan, Cassandra; Gombert, Sara; Papenfuss, Anthony T.; Madsen, Thomas; Belov, Katherine

    2012-01-01

    Background Devil Facial Tumour Disease (DFTD) is a unique clonal cancer that threatens the world's largest carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii) with extinction. This transmissible cancer is passed between individual devils by cell implantation during social interactions. The tumour arose in a Schwann cell of a single devil over 15 years ago and since then has expanded clonally, without showing signs of replicative senescence; in stark contrast to a somatic cell that displays a finite capacity for replication, known as the “Hayflick limit”. Methodology/Principal Findings In the present study we investigate the role of telomere length, measured as Telomere Copy Number (TCN), and telomerase and shelterin gene expression, as well as telomerase activity in maintaining hyperproliferation of Devil Facial Tumour (DFT) cells. Our results show that DFT cells have short telomeres. DFTD TCN does not differ between geographic regions or between strains. However, TCN has increased over time. Unlimited cell proliferation is likely to have been achieved through the observed up-regulation of the catalytic subunit of telomerase (TERT) and concomitant activation of telomerase. Up-regulation of the central component of shelterin, the TRF1-intercating nuclear factor 2 (TINF2) provides DFT a mechanism for telomere length homeostasis. The higher expression of both TERT and TINF2 may also protect DFT cells from genomic instability and enhance tumour proliferation. Conclusions/Significance DFT cells appear to monitor and regulate the length of individual telomeres: i.e. shorter telomeres are elongated by up-regulation of telomerase-related genes; longer telomeres are protected from further elongation by members of the shelterin complex, which may explain the lack of spatial and strain variation in DFT telomere copy number. The observed longitudinal increase in gene expression in DFT tissue samples and telomerase activity in DFT cell lines might indicate a

  16. Molecular adaptation of telomere associated genes in mammals

    PubMed Central

    2013-01-01

    Background 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. Results 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. Conclusion 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. PMID:24237966

  17. Mammalian development in space

    NASA Technical Reports Server (NTRS)

    Ronca, April E.

    2003-01-01

    Life on Earth, and thus the reproductive and ontogenetic processes of all extant species and their ancestors, evolved under the constant influence of the Earth's l g gravitational field. These considerations raise important questions about the ability of mammals to reproduce and develop in space. In this chapter, I review the current state of our knowledge of spaceflight effects on developing mammals. Recent studies are revealing the first insights into how the space environment affects critical phases of mammalian reproduction and development, viz., those events surrounding fertilization, embryogenesis, pregnancy, birth, postnatal maturation and parental care. This review emphasizes fetal and early postnatal life, the developmental epochs for which the greatest amounts of mammalian spaceflight data have been amassed. The maternal-offspring system, the coordinated aggregate of mother and young comprising mammalian development, is of primary importance during these early, formative developmental phases. The existing research supports the view that biologically meaningful interactions between mothers and offspring are changed in the weightlessness of space. These changes may, in turn, cloud interpretations of spaceflight effects on developing offspring. Whereas studies of mid-pregnant rats in space have been extraordinarily successful, studies of young rat litters launched at 9 days of postnatal age or earlier, have been encumbered with problems related to the design of in-flight caging and compromised maternal-offspring interactions. Possibilities for mammalian birth in space, an event that has not yet transpired, are considered. In the aggregate, the results indicate a strong need for new studies of mammalian reproduction and development in space. Habitat development and systematic ground-based testing are important prerequisites to future research with young postnatal rodents in space. Together, the findings support the view that the environment within which young

  18. Molecular mechanisms of activity and derepression of alternative lengthening of telomeres.

    PubMed

    Pickett, Hilda A; Reddel, Roger R

    2015-11-01

    Alternative lengthening of telomeres (ALT) involves homology-directed telomere synthesis. This multistep process is facilitated by loss of the ATRX or DAXX chromatin-remodeling factors and by abnormalities of the telomere nucleoprotein architecture, including altered DNA sequence and decreased TRF2 saturation. Induction of telomere-specific DNA damage triggers homology-directed searches, and NuRD-ZNF827 protein-protein interactions provide a platform for the telomeric recruitment of homologous recombination (HR) proteins. Telomere lengthening proceeds by strand exchange and template-driven DNA synthesis, which culminates in dissolution of HR intermediates. PMID:26581522

  19. Telomere mean length in patients with diabetic retinopathy

    PubMed Central

    Sharma, Rupali; Gupta, Amod; Thungapathra, M.; Bansal, Reema

    2015-01-01

    Telomere regression has been shown to be associated with several complex disorders like diabetes mellitus, cancer, cataract etc. Diabetic retinopathy develops as a complication of chronic hyperglycemia leading to increased oxidative stress that may potentially lead to shortening of telomeres. We sought to determine whether there is any association between telomere mean length (TML) of peripheral blood monocytes with the presence and severity of diabetic retinopathy. The study involved 120 subjects, comprising 27 non-insulin dependent diabetes mellitus (NIDDM) without any diabetic retinopathy (NDR), 45 NIDDM subjects with non-proliferative diabetic retinopathy (NPDR), 12 NIDDM subjects with proliferative diabetic retinopathy (PDR) and 36 healthy controls. Determination of TML of the study subjects was performed by Southern hybridization using telomere probe. Among the biochemical parameters, HBA1c showed a negative correlation with shortened telomeres in the PDR subjects. However, telomere length was positively correlated with high density lipo protein (HDL) in the control subjects. The control group had significantly greater TML as compared to the rest of the groups and the NDR subjects with NPDR and PDR had substantially decreased TML than the NIDDM subjects without retinopathy. PMID:26670612

  20. Human Rap1 modulates TRF2 attraction to telomeric DNA.

    PubMed

    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. PMID:25675958

  1. Human Rap1 modulates TRF2 attraction to telomeric DNA

    PubMed Central

    Janoušková, Eliška; Nečasová, Ivona; Pavloušková, Jana; Zimmermann, Michal; Hluchý, Milan; Marini, 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 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. PMID:25675958

  2. Telomere Transcripts Target Telomerase in Human Cancer Cells.

    PubMed

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

    2016-01-01

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

  3. The heritability of leucocyte telomere length dynamics

    PubMed Central

    Hjelmborg, Jacob B; Dalgård, Christine; Möller, Soren; Steenstrup, Troels; Kimura, Masayuki; Christensen, Kaare; Kyvik, Kirsten O; Aviv, Abraham

    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 unique environmental factors, estimated at 72% (95% CI 56% to 84%) affected LTL attrition rate with no indication of shared environmental effects. Conclusions This is the first study that estimated heritability of LTL and also its age-dependent attrition. As LTL attrition is much slower in adults than in children and given that having a long or a short LTL is largely determined before adulthood, our findings suggest that heritability and early life environment are the main determinants of LTL throughout the human life course. Thus, insights into factors that influence LTL at birth and its dynamics during childhood are crucial for understanding the role of telomere genetics in human ageing and longevity. PMID:25770094

  4. Telomeric Trans-Silencing in Drosophila melanogaster: Tissue Specificity, Development and Functional Interactions between Non-Homologous Telomeres

    PubMed Central

    Josse, Thibaut; Maurel-Zaffran, Corinne; de Vanssay, Augustin; Teysset, Laure; Todeschini, Anne-Laure; Delmarre, Valerie; Chaminade, Nicole; Anxolabéhère, Dominique; Ronsseray, Stéphane

    2008-01-01

    Background The study of P element repression in Drosophila melanogaster led to the discovery of the telomeric Trans-Silencing Effect (TSE), a homology-dependent repression mechanism by which a P-transgene inserted in subtelomeric heterochromatin (Telomeric Associated Sequences, “TAS”) has the capacity to repress in trans, in the female germline, a homologous P-lacZ transgene located in euchromatin. TSE can show variegation in ovaries, displays a maternal effect as well as an epigenetic transmission through meiosis and involves heterochromatin and RNA silencing pathways. Principal Findings Here, we analyze phenotypic and genetic properties of TSE. We report that TSE does not occur in the soma at the adult stage, but appears restricted to the female germline. It is detectable during development at the third instar larvae where it presents the same tissue specificity and maternal effect as in adults. Transgenes located in TAS at the telomeres of the main chromosomes can be silencers which in each case show the maternal effect. Silencers located at non-homologous telomeres functionally interact since they stimulate each other via the maternally-transmitted component. All germinally-expressed euchromatic transgenes tested, located on all major chromosomes, were found to be repressed by a telomeric silencer: thus we detected no TSE escaper. The presence of the euchromatic target transgene is not necessary to establish the maternal inheritance of TSE, responsible for its epigenetic behavior. A single telomeric silencer locus can simultaneously repress two P-lacZ targets located on different chromosomal arms. Conclusions and Significance Therefore TSE appears to be a widespread phenomenon which can involve different telomeres and work across the genome. It can explain the P cytotype establishment by telomeric P elements in natural Drosophila populations. PMID:18813361

  5. Specific Localization of the Drosophila Telomere Transposon Proteins and RNAs, Give Insight in Their Behavior, Control and Telomere Biology in This Organism

    PubMed Central

    López-Panadès, Elisenda; Gavis, Elizabeth R.; Casacuberta, Elena

    2015-01-01

    Drosophila telomeres constitute a remarkable exception to the telomerase mechanism. Although maintaining the same cytological and functional properties as telomerase maintain telomeres, Drosophila telomeres embed the telomere retrotransposons whose specific and highly regulated terminal transposition maintains the appropriate telomere length in this organism. Nevertheless, our current understanding of how the mechanism of the retrotransposon telomere works and which features are shared with the telomerase system is very limited. We report for the first time a detailed study of the localization of the main components that constitute the telomeres in Drosophila, HeT-A and TART RNAs and proteins. Our results in wild type and mutant strains reveal localizations of HeT-A Gag and TART Pol that give insight in the behavior of the telomere retrotransposons and their control. We find that TART Pol and HeT-A Gag only co-localize at the telomeres during the interphase of cells undergoing mitotic cycles. In addition, unexpected protein and RNA localizations with a well-defined pattern in cells such as the ovarian border cells and nurse cells, suggest possible strategies for the telomere transposons to reach the oocyte, and/or additional functions that might be important for the correct development of the organism. Finally, we have been able to visualize the telomere RNAs at different ovarian stages of development in wild type and mutant lines, demonstrating their presence in spite of being tightly regulated by the piRNA mechanism. PMID:26068215

  6. PML is required for telomere stability in non-neoplastic human cells.

    PubMed

    Marchesini, M; Matocci, R; Tasselli, L; Cambiaghi, V; Orleth, A; Furia, L; Marinelli, C; Lombardi, S; Sammarelli, G; Aversa, F; Minucci, S; Faretta, M; Pelicci, P G; Grignani, F

    2016-04-01

    Telomeres interact with numerous proteins, including components of the shelterin complex, whose alteration, similarly to proliferation-induced telomere shortening, initiates cellular senescence. In tumors, telomere length is maintained by Telomerase activity or by the Alternative Lengthening of Telomeres mechanism, whose hallmark is the telomeric localization of the promyelocytic leukemia (PML) protein. Whether PML contributes to telomeres maintenance in normal cells is unknown. We show that in normal human fibroblasts the PML protein associates with few telomeres, preferentially when they are damaged. Proliferation-induced telomere attrition or their damage due to alteration of the shelterin complex enhances the telomeric localization of PML, which is increased in human T-lymphocytes derived from patients genetically deficient in telomerase. In normal fibroblasts, PML depletion induces telomere damage, nuclear and chromosomal abnormalities, and senescence. Expression of the leukemia protein PML/RARα in hematopoietic progenitors displaces PML from telomeres and induces telomere shortening in the bone marrow of pre-leukemic mice. Our work provides a novel view of the physiologic function of PML, which participates in telomeres surveillance in normal cells. Our data further imply that a diminished PML function may contribute to cell senescence, genomic instability, and tumorigenesis. PMID:26119943

  7. Meiotic Telomere Protein Ndj1p Is Required for Meiosis-Specific Telomere Distribution, Bouquet Formation and Efficient Homologue Pairing

    PubMed Central

    Trelles-Sticken, Edgar; Dresser, Michael E.; Scherthan, Harry

    2000-01-01

    We have investigated the requirements for NDJ1 in meiotic telomere redistribution and clustering in synchronized cultures of Saccharomyces cerevisiae. On induction of wild-type meiosis, telomeres disperse from premeiotic aggregates over the nuclear periphery, and then cluster near the spindle pole body (bouquet arrangement) before dispersing again. In ndj1Δ meiocytes, telomeres are scattered throughout the nucleus and fail to form perinuclear meiosis-specific distribution patterns, suggesting that Ndj1p may function to tether meiotic telomeres to the nuclear periphery. Since ndj1Δ meiocytes fail to cluster their telomeres at any prophase stage, Ndj1p is the first protein shown to be required for bouquet formation in a synaptic organism. Analysis of homologue pairing by two-color fluorescence in situ hybridization with cosmid probes to regions on III, IX, and XI revealed that disruption of bouquet formation is associated with a significant delay (>2 h) of homologue pairing. An increased and persistent fraction of ndj1Δ meiocytes with Zip1p polycomplexes suggests that chromosome polarization is important for synapsis progression. Thus, our observations support the hypothesis that meiotic telomere clustering contributes to efficient homologue alignment and synaptic pairing. Under naturally occurring conditions, bouquet formation may allow for rapid sporulation and confer a selective advantage. PMID:11018056

  8. Mammalian Septins Nomenclature

    PubMed Central

    Macara, Ian G.; Baldarelli, Richard; Field, Christine M.; Glotzer, Michael; Hayashi, Yasuhide; Hsu, Shu-Chan; Kennedy, Mary B.; Kinoshita, Makoto; Longtine, Mark; Low, Claudia; Maltais, Lois J.; McKenzie, Louise; Mitchison, Timothy J.; Nishikawa, Toru; Noda, Makoto; Petty, Elizabeth M.; Peifer, Mark; Pringle, John R.; Robinson, Phillip J.; Roth, Dagmar; Russell, S.E. Hilary; Stuhlmann, Heidi; Tanaka, Manami; Tanaka, Tomoo; Trimble, William S.; Ware, Jerry; Zeleznik-Le, Nancy J.; Zieger, Barbara

    2002-01-01

    There are 10 known mammalian septin genes, some of which produce multiple splice variants. The current nomenclature for the genes and gene products is very confusing, with several different names having been given to the same gene product and distinct names given to splice variants of the same gene. Moreover, some names are based on those of yeast or Drosophila septins that are not the closest homologues. Therefore, we suggest that the mammalian septin field adopt a common nomenclature system, based on that adopted by the Mouse Genomic Nomenclature Committee and accepted by the Human Genome Organization Gene Nomenclature Committee. The human and mouse septin genes will be named SEPT1–SEPT10 and Sept1–Sept10, respectively. Splice variants will be designated by an underscore followed by a lowercase “v” and a number, e.g., SEPT4_v1. PMID:12475938

  9. Mammalian sweet taste receptors.

    PubMed

    Nelson, G; Hoon, M A; Chandrashekar, J; Zhang, Y; Ryba, N J; Zuker, C S

    2001-08-10

    The sense of taste provides animals with valuable information about the quality and nutritional value of food. Previously, we identified a large family of mammalian taste receptors involved in bitter taste perception (the T2Rs). We now report the characterization of mammalian sweet taste receptors. First, transgenic rescue experiments prove that the Sac locus encodes T1R3, a member of the T1R family of candidate taste receptors. Second, using a heterologous expression system, we demonstrate that T1R2 and T1R3 combine to function as a sweet receptor, recognizing sweet-tasting molecules as diverse as sucrose, saccharin, dulcin, and acesulfame-K. Finally, we present a detailed analysis of the patterns of expression of T1Rs and T2Rs, thus providing a view of the representation of sweet and bitter taste at the periphery. PMID:11509186

  10. Ribosomal protein S6 kinase 1 signaling regulates mammalian lifespan

    PubMed Central

    Selman, Colin; Tullet, Jennifer M.A.; Wieser, Daniela; Irvine, Elaine; Lingard, Steven J.; Choudhury, Agharul I.; Claret, Marc; Al-Qassab, Hind; Carmignac, Danielle; Ramadani, Faruk; Woods, Angela; Robinson, Iain C.A.; Schuster, Eugene; Batterham, Rachel L.; Kozma, Sara C.; Thomas, George; Carling, David; Okkenhaug, Klaus; Thornton, Janet M.; Partridge, Linda; Gems, David; Withers, Dominic J.

    2016-01-01

    Caloric restriction (CR) protects against aging and disease but the mechanisms by which this affects mammalian lifespan are unclear. We show in mice that deletion of the nutrient-responsive mTOR (mammalian target of rapamycin) signaling pathway component ribosomal S6 protein kinase 1 (S6K1) led to increased lifespan and resistance to age-related pathologies such as bone, immune and motor dysfunction and loss of insulin sensitivity. Deletion of S6K1 induced gene expression patterns similar to those seen in CR or with pharmacological activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), a conserved regulator of the metabolic response to CR. Our results demonstrate that S6K1 influences healthy mammalian lifespan, and suggest therapeutic manipulation of S6K1 and AMPK might mimic CR and provide broad protection against diseases of aging. PMID:19797661

  11. Rheotaxis guides mammalian sperm

    PubMed Central

    Miki, Kiyoshi; Clapham, David E

    2013-01-01

    Background In sea urchins, spermatozoan motility is altered by chemotactic peptides, giving rise to the assumption that mammalian eggs also emit chemotactic agents that guide spermatozoa through the female reproductive tract to the mature oocyte. Mammalian spermatozoa indeed undergo complex adaptations within the female (the process of capacitation) that are initiated by agents ranging from pH to progesterone, but these factors are not necessarily taxic. Currently, chemotaxis, thermotaxis, and rheotaxis have not been definitively established in mammals. Results Here, we show that positive rheotaxis, the ability of organisms to orient and swim against the flow of surrounding fluid, is a major taxic factor for mouse and human sperm. This flow is generated within 4 hours of sexual stimulation and coitus in female mice; prolactin-triggered oviductal fluid secretion clears the oviduct of debris, lowers viscosity, and generates the stream that guides sperm migration in the oviduct. Rheotaxic movement is demonstrated in capacitated and uncapacitated spermatozoa in low and high viscosity medium. Finally, we show that a unique sperm motion we quantify using the sperm head's rolling rate reflects sperm rotation that generates essential force for positioning the sperm in the stream. Rotation requires CatSper channels, presumably by enabling Ca2+ influx. Conclusions We propose that rheotaxis is a major determinant of sperm guidance over long distances in the mammalian female reproductive tract. Coitus induces fluid flow to guide sperm in the oviduct. Sperm rheotaxis requires rotational motion during CatSper channel-dependent hyperactivated motility. PMID:23453951

  12. Sexual Dysfunction and Infertility

    MedlinePlus

    ... American Society for Reproductive Medicine Sexual dysfunction and infertility What is sexual dysfunction and how common is ... and 40% of women. For couples dealing with infertility, it is even more common. Often, people ignore ...

  13. Enforced telomere elongation increases the sensitivity of human tumour cells to ionizing radiation

    PubMed Central

    Fairlie, Jennifer; Harrington, Lea

    2015-01-01

    More than 85% of all human cancers possess the ability to maintain chromosome ends, or telomeres, by virtue of telomerase activity. Loss of functional telomeres is incompatible with survival, and telomerase inhibition has been established in several model systems to be a tractable target for cancer therapy. As human tumour cells typically maintain short equilibrium telomere lengths, we wondered if enforced telomere elongation would positively or negatively impact cell survival. We found that telomere elongation beyond a certain length significantly decreased cell clonogenic survival after gamma irradiation. Susceptibility to irradiation was dosage-dependent and increased at telomere lengths exceeding 17 kbp despite the fact that all chromosome ends retained telomeric DNA. These data suggest that an optimal telomere length may promote human cancer cell survival in the presence of genotoxic stress. PMID:25484304

  14. Social Isolation Shortens Telomeres in African Grey Parrots (Psittacus erithacus erithacus)

    PubMed Central

    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 (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. PMID:24705445

  15. Loss of ATRX Suppresses Resolution of Telomere Cohesion to Control Recombination in ALT Cancer Cells.

    PubMed

    Ramamoorthy, Mahesh; Smith, Susan

    2015-09-14

    The chromatin-remodeler ATRX is frequently lost in cancer cells that use ALT (alternative lengthening of telomeres) for telomere maintenance, but its function in telomere recombination is unknown. Here we show that loss of ATRX suppresses the timely resolution of sister telomere cohesion that normally occurs prior to mitosis. In the absence of ATRX, the histone variant macroH2A1.1 binds to the poly(ADP-ribose) polymerase tankyrase 1, preventing it from localizing to telomeres and resolving cohesion. The resulting persistent telomere cohesion promotes recombination between sister telomeres, while it suppresses inappropriate recombination between non-sisters. Forced resolution of sister telomere cohesion induces excessive recombination between non-homologs, genomic instability, and impaired cell growth, indicating the ATRX-macroH2A1.1-tankyrase axis as a potential therapeutic target in ALT tumors. PMID:26373281

  16. Variations in telomere maintenance and the role of telomerase inhibition in gastrointestinal cancer

    PubMed Central

    Heeg, Steffen

    2015-01-01

    Immortalization is an important step toward the malignant transformation of human cells and is critically dependent upon telomere maintenance. There are two known mechanisms to maintain human telomeres. The process of telomere maintenance is either mediated through activation of the enzyme telomerase or through an alternative mechanism of telomere lengthening called ALT. While 85% of all human tumors show reactivation of telomerase, the remaining 15% are able to maintain telomeres via ALT. The therapeutic potential of telomerase inhibitors is currently investigated in a variety of human cancers. Gastrointestinal tumors are highly dependent on telomerase as a mechanism of telomere maintenance, rendering telomeres as well as telomerase potential targets for cancer therapy. This article focuses on the molecular mechanisms of telomere biology and telomerase activation in gastrointestinal cancers and reviews strategies of telomerase inhibition and their potential therapeutic use in these tumor entities. PMID:26675332

  17. Stress and telomere shortening among central Indian conservation refugees.

    PubMed

    Zahran, Sammy; Snodgrass, Jeffrey G; Maranon, David G; Upadhyay, Chakrapani; Granger, Douglas A; Bailey, Susan M

    2015-03-01

    Research links psychosocial stress to premature telomere shortening and accelerated human aging; however, this association has only been demonstrated in so-called "WEIRD" societies (Western, educated, industrialized, rich, and democratic), where stress is typically lower and life expectancies longer. By contrast, we examine stress and telomere shortening in a non-Western setting among a highly stressed population with overall lower life expectancies: poor indigenous people--the Sahariya--who were displaced (between 1998 and 2002) from their ancestral homes in a central Indian wildlife sanctuary. In this setting, we examined adult populations in two representative villages, one relocated to accommodate the introduction of Asiatic lions into the sanctuary (n = 24 individuals), and the other newly isolated in the sanctuary buffer zone after their previous neighbors were moved (n = 22). Our research strategy combined physical stress measures via the salivary analytes cortisol and α-amylase with self-assessments of psychosomatic stress, ethnographic observations, and telomere length assessment [telomere-fluorescence in situ hybridization (TEL-FISH) coupled with 3D imaging of buccal cell nuclei], providing high-resolution data amenable to multilevel statistical analysis. Consistent with expectations, we found significant associations between each of our stress measures--the two salivary analytes and the psychosomatic symptom survey--and telomere length, after adjusting for relevant behavioral, health, and demographic traits. As the first study (to our knowledge) to link stress to telomere length in a non-WEIRD population, our research strengthens the case for stress-induced telomere shortening as a pancultural biomarker of compromised health and aging. PMID:25730846

  18. Cytogenetic telomere and telomerase studies in lumbo-sacral chordoma

    SciTech Connect

    Schwartz, H.S.; Dahir, G.A.; Miller, L.K.

    1994-09-01

    Lumbo-sacral chordomas are rare skeletal sarcomas that originate from the remnant notochord. There are approximately 35 lumbo-sacral chordomas reported annually in the U.S.A. The understanding of this rare human cancer is limited to observations of its clinical behavior and embryonic link. We performed chromosome and molecular analyses from five surgically harvested chordomas in an effort to document genetic abnormalities and to further understand its tumor biology. Cytogenetically, four of five patients had entirely normal chromosomes. One patient had several abnormalities seen in one of 100 cells including a translocation with breakpoints at bands 5q13 and 7q22, loss of one X chromosome and an extra chromosome 14. There was no evidence of monosomy X or trisomy 14 seen with interphase in situ hybridization using biotin-labeled alpha satellite chromosome specific probes for chromosome 14/22 and X. Telomere integrity is required to protect termini from illegitimate recombination. Typically telomeric reduction occurs in senescent fibroblasts in vivo aging and several human solid tumors. A telomeric probe (TTAGGG){sub 50} was hybridized to genomic DNA isolated from chordoma cells and digested with Hinf I which allows the telomeric DNA to remain intact. The tumor DNA was paired with leukocyte DNA from age-matched controls and revealed telomere elongation in all four patients studied with molecular genetic techniques. Telomerase activity is required to maintain telomere integrity and is not present in normal somatic cells. It is determined by visualizing the sizes of the electrophoresis gel-separated radioactive telomeric fragments assembled during incubation of cytoplasmic extracts containing telomerase. Telomerase activity was detected when compared with HeLa cells, a positive control. In addition, no telomerase activity was detected from the chordoma patient`s fibroblasts.

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

    PubMed

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

    1997-01-01

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

  20. A retrospective examination of mean relative telomere length in the Tasmanian Familial Hematological Malignancies Study

    PubMed Central

    BLACKBURN, NICHOLAS B.; CHARLESWORTH, JAC C.; MARTHICK, JAMES R.; TEGG, ELIZABETH M.; MARSDEN, KATHERINE A.; SRIKANTH, VELANDAI; BLANGERO, JOHN; LOWENTHAL, RAY M.; FOOTE, SIMON J.; DICKINSON, JOANNE L.

    2015-01-01

    Telomere length has a biological link to cancer, with excessive telomere shortening leading to genetic instability and resultant malignant transformation. Telomere length is heritable and genetic variants determining telomere length have been identified. Telomere biology has been implicated in the development of hematological malignancies (HMs), therefore, closer examination of telomere length in HMs may provide further insight into genetic etiology of disease development and support for telomere length as a prognostic factor in HMs. We retrospectively examined mean relative telomere length in the Tasmanian Familial Hematological Malignancies Study using a quantitative PCR method on genomic DNA from peripheral blood samples. Fifty-five familial HM cases, 191 unaffected relatives of familial HM cases and 75 non-familial HM cases were compared with 758 population controls. Variance components modeling was employed to identify factors influencing variation in telomere length. Overall, HM cases had shorter mean relative telomere length (P=2.9×10−6) and this was observed across both familial and non-familial HM cases (P=2.2×10−4 and 2.2×10−5, respectively) as well as additional subgroupings of HM cases according to broad subtypes. Mean relative telomere length was also significantly heritable (62.6%; P=4.7×10−5) in the HM families in the present study. We present new evidence of significantly shorter mean relative telomere length in both familial and non-familial HM cases from the same population adding further support to the potential use of telomere length as a prognostic factor in HMs. Whether telomere shortening is the cause of or the result of HMs is yet to be determined, but as telomere length was found to be highly heritable in our HM families this suggests that genetics driving the variation in telomere length is related to HM disease risk. PMID:25351806

  1. Telomere damage induced by the G-quadruplex ligand RHPS4 has an antitumor effect

    PubMed Central

    Salvati, Erica; Leonetti, Carlo; Rizzo, Angela; Scarsella, Marco; Mottolese, Marcella; Galati, Rossella; Sperduti, Isabella; Stevens, Malcolm F.G.; D’Incalci, Maurizio; Blasco, Maria; Chiorino, Giovanna; Bauwens, Serge; Horard, Béatrice; Gilson, Eric; Stoppacciaro, Antonella; Zupi, Gabriella; Biroccio, Annamaria

    2007-01-01

    Functional telomeres are required for the replicability of cancer cells. The G-rich strand of telomeric DNA can fold into a 4-stranded structure known as the G-quadruplex (G4), whose stabilization alters telomere function limiting cancer cell growth. Therefore, the G4 ligand RHPS4 may possess antitumor activity. Here, we show that RHPS4 triggers a rapid and potent DNA damage response at telomeres in human transformed fibroblasts and melanoma cells, characterized by the formation of several telomeric foci containing phosphorylated DNA damage response factors γ-H2AX, RAD17, and 53BP1. This was dependent on DNA repair enzyme ATR, correlated with delocalization of the protective telomeric DNA–binding protein POT1, and was antagonized by overexpression of POT1 or TRF2. In mice, RHPS4 exerted its antitumor effect on xenografts of human tumor cells of different histotype by telomere injury and tumor cell apoptosis. Tumor inhibition was accompanied by a strong DNA damage response, and tumors overexpressing POT1 or TRF2 were resistant to RHPS4 treatment. These data provide evidence that RHPS4 is a telomere damage inducer and that telomere disruption selectively triggered in malignant cells results in a high therapeutic index in mice. They also define a functional link between telomere damage and antitumor activity and reveal the key role of telomere-protective factors TRF2 and POT1 in response to this anti-telomere strategy. PMID:17932567

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

    PubMed

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

    2016-07-01

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

  3. Telomere length abnormalities and telomerase RNA component expression in gastroenteropancreatic neuroendocrine tumors.

    PubMed

    Kim, Hee Sung; Lee, Hye Seung; Nam, Kyung Han; Choi, Jiwoon; Kim, Woo Ho

    2015-06-01

    Telomere lengths in normal human cells are tightly regulated within a narrow range. Telomere length abnormalities are prevalent genetic alterations in malignant transformation. We studied telomere length abnormalities, telomerase RNA component (TERC) expression, alpha-thalassemia X-linked mental retardation (ATRX) expression, and death domain-associated protein (DAXX) expression in gastroenteropancreatic neuroendocrine tumors (GEP-NETs). We used tissue microarrays to perform telomere fluorescent in situ hybridization (FISH) and TERC in situ hybridization in 327 formalin-fixed paraffin-embedded tissues of GEP-NETs. Telomere length abnormalities were detected in 35% of 253 informative cases by using telomere FISH. Ten cases had altered lengthening of telomeres (ALT), an ALT-positive phenotype (4%), and 79 cases had telomere shortening (31%). The ALT-positive phenotype was significantly associated with tumors of pancreatic origin (7/10) and loss of ATRX or DAXX protein (8/10). Telomere shortening was significantly associated with low TERC expression. In the survival analysis, loss of ATRX or DAXX protein was associated with a decreased overall survival. Multivariate regression analysis showed that lymph node metastasis and high TERC expression were independent prognostic factors of reduced overall survival (OS) for patients with GEP-NETs. Our results showed that telomere lengthening (the ALT-positive phenotype) and telomere shortening accompanied by low TERC levels are two types of clinically significant telomere abnormalities in GEP-NETs. PMID:26026117

  4. Homologous recombination-dependent repair of telomeric DSBs in proliferating human cells.

    PubMed

    Mao, Pingsu; Liu, Jingfan; Zhang, Zepeng; Zhang, Hong; Liu, Haiying; Gao, Song; Rong, Yikang S; Zhao, Yong

    2016-01-01

    Telomeres prevent chromosome ends from being recognized as double-stranded breaks (DSBs). Meanwhile, G/C-rich repetitive telomeric DNA is susceptible to attack by DNA-damaging agents. How cells balance the need to protect DNA ends and the need to repair DNA lesions in telomeres is unknown. Here we show that telomeric DSBs are efficiently repaired in proliferating cells, but are irreparable in stress-induced and replicatively senescent cells. Using the CRISPR-Cas9 technique, we specifically induce DSBs at telomeric or subtelomeric regions. We find that DSB repair (DSBR) at subtelomeres occurs in an error-prone manner resulting in small deletions, suggestive of NHEJ. However, DSBR in telomeres involves 'telomere-clustering', 3'-protruding C-rich telomeric ssDNA, and HR between sister-chromatid or interchromosomal telomeres. DSBR in telomeres is suppressed by deletion or inhibition of Rad51. These findings reveal proliferation-dependent DSBR in telomeres and suggest that telomeric HR, which is normally constitutively suppressed, is activated in the context of DSBR. PMID:27396625

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

    PubMed

    Vítková, Magda; Král, Jirí; Traut, Walther; Zrzavý, Jan; Marec, Frantisek

    2005-01-01

    The (TTAGG)n sequence is supposed to be an ancestral DNA motif of telomeres in insects. Here we examined the occurrence of TTAGG telomeric repeats in other arthropods and their close relatives by Southern hybridization of genomic DNAs and fluorescence in-situ hybridization (FISH) of chromosomes with (TTAGG)n probes or, alternatively, with the 'vertebrate' telomeric probe, (TTAGGG)n. Our results show that the (TTAGG)n motif is conserved in entognathous hexapods (Diplura and Collembola), crustaceans (Malacostraca, Branchiura, Pentastomida, and Branchiopoda), myriapods (Diplopoda and Chilopoda), pycnogonids, and most chelicerates (Palpigradi, Amblypygi, Acari, Opiliones, Scorpiones, Pseudoscorpiones, and Solifugae) but not in spiders (Araneae). The presence of TTAGG repeats in these groups suggests that the sequence is an ancestral motif of telomeres not only in insects but in Arthropoda. We failed, however, to detect the TTAGG repeats in close relatives of the arthropods, Tardigrada and Onychophora. But while Onychophora had the 'vertebrate' (TTAGGG)n motif instead, the Tardigrada did not. The (TTAGG)n motif probably evolved from the (TTAGGG)n motif. Based on our and compiled data, we presume that the 'vertebrate' motif (TTAGGG)n is an ancestral motif of telomeres in bilaterian animals and possibly also in the superclade including animals, fungi and amoebozoans. PMID:15861304

  6. Covalent ligation studies on the human telomere quadruplex

    PubMed Central

    Qi, Jianying; Shafer, Richard H.

    2005-01-01

    Recent X-ray crystallographic studies on the human telomere sequence d[AGGG(TTAGGG)3] revealed a unimolecular, parallel quadruplex structure in the presence of potassium ions, while earlier NMR results in the presence of sodium ions indicated a unimolecular, antiparallel quadruplex. In an effort to identify and isolate the parallel form in solution, we have successfully ligated into circular products the single-stranded human telomere and several modified human telomere sequences in potassium-containing solutions. Using these sequences with one or two terminal phosphates, we have made chemically ligated products via creation of an additional loop. Circular products have been identified by polyacrylamide gel electrophoresis, enzymatic digestion with exonuclease VII and electrospray mass spectrometry in negative ion mode. Optimum pH for the ligation reaction of the human telomere sequence ranges from 4.5 to 6.0. Several buffers were also examined, with MES yielding the greatest ligation efficiency. Human telomere sequences with two phosphate groups, one each at the 3′ and 5′ ends, were more efficient at ligation, via pyrophosphate bond formation, than the corresponding sequences with only one phosphate group, at the 5′ end. Circular dichroism spectra showed that the ligation product was derived from an antiparallel, single-stranded guanine quadruplex rather than a parallel single-stranded guanine quadruplex structure. PMID:15933211

  7. Telomere shortening in the colonial coral Acropora digitifera during development.

    PubMed

    Tsuta, Hiroki; Shinzato, Chuya; Satoh, Nori; Hidaka, Michio

    2014-03-01

    To test whether telomere length can be used in estimating the age of colonial corals, we used terminal restriction fragment (TRF) length analysis to compare the telomere lengths of the coral Acropora digitifera at three developmental stages: sperm, planula larvae, and polyps of adult colonies. We also compared the mean TRF lengths between branches at the center and periphery of tabular colonies of A. digitifera. A significant difference was observed in the mean TRF lengths in sperm, planulae, and polyps. The mean TRF length was longest in sperm and shortest in polyps from adult colonies. These results suggest that telomere length decreases during coral development and may be useful for estimating coral age. However, the mean TRF length of branches at the center of a table-form colony tended to be longer than that of peripheral branches, although this difference was not statistically significant. This suggests that both the chronological age of polyps and cell proliferation rate influence telomere length in polyps, and that estimating coral age based on telomere length is not a simple endeavor. PMID:24601774

  8. Internal genomic regions mobilized for telomere maintenance in C. elegans

    PubMed Central

    Kim, Chuna; Sung, Sanghyun; Lee, Junho

    2016-01-01

    ABSTRACT Because DNA polymerase cannot replicate telomeric DNA at linear chromosomal ends, eukaryotes have developed specific telomere maintenance mechanisms (TMMs). A major TMM involves specialized reverse transcriptase, telomerase. However, there also exist various telomerase-independent TMMs (TI-TMMs), which can arise both in pathological conditions (such as cancers) and during evolution. The TI-TMM in cancer cells is called alternative lengthening of telomeres (ALT), whose mechanism is not fully understood. We generated stably maintained telomerase-independent survivors from C. elegans telomerase mutants and found that, unlike previously described survivors in worms, these survivors “mobilize” specific internal sequence blocks for telomere lengthening, which we named TALTs (templates for ALT). The cis-duplication of internal genomic TALTs produces “reservoirs” of TALTs, whose trans-duplication occurs at all chromosome ends in the ALT survivors. Our discovery that different TALTs are utilized in different wild isolates provides insight into the molecular events leading to telomere evolution. PMID:27073737

  9. Internal genomic regions mobilized for telomere maintenance in C. elegans.

    PubMed

    Kim, Chuna; Sung, Sanghyun; Lee, Junho

    2016-01-01

    Because DNA polymerase cannot replicate telomeric DNA at linear chromosomal ends, eukaryotes have developed specific telomere maintenance mechanisms (TMMs). A major TMM involves specialized reverse transcriptase, telomerase. However, there also exist various telomerase-independent TMMs (TI-TMMs), which can arise both in pathological conditions (such as cancers) and during evolution. The TI-TMM in cancer cells is called alternative lengthening of telomeres (ALT), whose mechanism is not fully understood. We generated stably maintained telomerase-independent survivors from C. elegans telomerase mutants and found that, unlike previously described survivors in worms, these survivors "mobilize" specific internal sequence blocks for telomere lengthening, which we named TALTs (templates for ALT). The cis-duplication of internal genomic TALTs produces "reservoirs" of TALTs, whose trans-duplication occurs at all chromosome ends in the ALT survivors. Our discovery that different TALTs are utilized in different wild isolates provides insight into the molecular events leading to telomere evolution. PMID:27073737

  10. Transposition as a mechanism for maintaining telomere length in Drosophila

    SciTech Connect

    Mason, J.M.; Biessmann, H.

    1993-12-31

    Telomeres are structures at the termini of linear chromosomes that serve to maintain the stability of those ends. Several functions have been attributed to telomeres, at least two of these are vital. The vital functions are (a) to {open_quotes}cap{close_quotes} the natural chromosome ends in order to distinguish them from broken ends and, thus, to protect them from recombination, repair, and degradation, and (b) to maintain chromosome length by periodic elongation and, thus, to counteract the inability of DNA polymerases to replicate linear chromosomes completely. While very little is known about capping, the mechanisms of telomere elongation in a number of organisms are being elucidated. Several models for elongation have been proposed. Recent evidence suggests that two of these may operate in different organisms or under different conditions. In many species elongation is accomplished by the interaction of two telomeric DNA repeats. The repeating unit is generally 6-8 basepairs (bp) long and guanine-rich on one strand. The sequence of the repeating unit is evolutionarily conserved, being very similar in ciliated protozoa, flowering plants and vertebrates. The second component is an enzyme, telomerase, that adds more copies of the repeating unit at the terminus. Telomerase resembles reverse transcriptases in structure and carries an associated RNA that is used as a template for the telomere extension.

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

    PubMed Central

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

    2015-01-01

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

  12. Aminoglycoside binding to Oxytricha Nova Telomeric DNA

    PubMed Central

    Ranjan, Nihar; Andreasen, Katrine F.; Kumar, Sunil; Hyde-volpe, David; Arya, Dev P.

    2012-01-01

    Telomeric DNA sequences have been at the center stage of drug design for cancer treatment in recent years. The ability of these DNA structures to form four stranded nucleic acid structures, called G-quadruplexes, has been perceived as target for inhibiting telomerase activity vital for the longevity of cancer cells. Being highly diverse in structural forms, these G-quadruplexes are subjects of detailed studies of ligand–DNA interactions of different classes, which will pave the way for logical design of more potent ligands in future. The binding of aminoglycosides were investigated with Oxytricha Nova quadruplex forming DNA sequence (GGGGTTTTGGGG)2. Isothermal Titration calorimetry (ITC) determined ligand to quadruplex binding ratio shows 1:1 neomycin:quadruplex binding with association constants (Ka ) ~ 105M−1 while paromomycin was found to have a two-fold weaker affinity than neomycin. The CD titration experiments with neomycin resulted in minimal changes in the CD signal. FID assays, performed to determine the minimum concentration required to displace half of the fluorescent probe bound, showed neomycin as the best of the all aminoglycosides studied for quadruplex binding. Initial NMR footprint suggests that ligand-DNA interactions occur in the wide groove of the quadruplex. Computational docking studies also indicate that aminoglycosides bind in the wide groove of the quadruplex. PMID:20886815

  13. Sumoylation in Synaptic Function and Dysfunction

    PubMed Central

    Schorova, Lenka; Martin, Stéphane

    2016-01-01

    Sumoylation has recently emerged as a key post-translational modification involved in many, if not all, biological processes. Small Ubiquitin-like Modifier (SUMO) polypeptides are covalently attached to specific lysine residues of target proteins through a dedicated enzymatic pathway. Disruption of the SUMO enzymatic pathway in the developing brain leads to lethality indicating that this process exerts a central role during embryonic and post-natal development. However, little is still known regarding how this highly dynamic protein modification is regulated in the mammalian brain despite an increasing number of data implicating sumoylated substrates in synapse formation, synaptic communication and plasticity. The aim of this review is therefore to briefly describe the enzymatic SUMO pathway and to give an overview of our current knowledge on the function and dysfunction of protein sumoylation at the mammalian synapse. PMID:27199730

  14. Tired telomeres: Poor global sleep quality, perceived stress, and telomere length in immune cell subsets in obese men and women.

    PubMed

    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

  15. Dual-tagging system for the affinity purification of mammalian protein complexes

    SciTech Connect

    Giannone, Richard J; McDonald, W Hayes; Hurst, Gregory {Greg} B; Huang, Ying; Wu, Jun; Liu, Yie; Wang, Yisong

    2007-01-01

    Although affinity purification coupled with mass spectrometry (MS) provides a powerful tool to study protein-protein interactions, this strategy has encountered numerous difficulties when adapted to mammalian cells. Here we describe a Gateway{reg_sign}-compatible dual-tag affinity purification system that integrates regulatable expression, tetracysteine motifs, and various combinations of affinity tags to facilitate the cloning, detection, and purification of bait proteins and their interacting partners. Utilizing the human telomere binding protein TRF2 as a benchmark, we demonstrate bait protein recoveries upwards of approximately 16% from as little as 1-7 x 10{sup 7} cells and successfully identify known TRF2 interacting proteins, suggesting that our dual-tag affinity purification approach is a capable new tool for expanding the capacity to explore mammalian proteomic networks.

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

    SciTech Connect

    Sugioka-Sugiyama, Rie; Sugiyama, Tomoyasu

    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.

  17. Comprehensive screening of alternative lengthening of telomeres phenotype and loss of ATRX expression in sarcomas.

    PubMed

    Liau, Jau-Yu; Lee, Jen-Chieh; Tsai, Jia-Huei; Yang, Ching-Yao; Liu, Tsung-Lin; Ke, Zhi-Long; Hsu, Hung-Han; Jeng, Yung-Ming

    2015-12-01

    According to cytogenetic aberrations, sarcomas can be categorized as complex or simple karyotype tumors. Alternative lengthening of telomeres is a telomere-maintenance mechanism common in sarcomas. Recently, this mechanism was found to be associated with loss of either α-thalassemia/mental retardation syndrome X-linked (ATRX) or death domain-associated (DAXX) protein. We previously reported that alternative lengthening of telomeres and loss of ATRX expression were common in leiomyosarcoma, angiosarcoma, pleomorphic liposarcoma, and dedifferentiated liposarcoma. In the present study, we screened an additional 245 sarcomas of other types to determine the prevalence of alternative lengthening of telomeres, loss of ATRX/DAXX expression, and their relationship. Undifferentiated pleomorphic sarcomas were frequently alternative lengthening of telomeres positive (65%) and loss of ATRX was seen in approximately half of the alternative lengthening of telomeres-positive tumors. Nineteen of 25 myxofibrosarcomas were alternative lengthening of telomeres-positive, but only one was ATRX deficient. Three of 15 radiation-associated sarcomas were alternative lengthening of telomeres positive, but none of them was ATRX deficient. Alternative lengthening of telomeres and/or loss of ATRX were uncommon in malignant peripheral nerve sheath tumors, gastrointestinal stromal tumors, and embryonal rhabdomyosarcomas. By contrast, none of the 71 gene fusion-associated sarcomas was ATRX deficient or alternative lengthening of telomeres positive. All tumors exhibited preserved DAXX expression. Combining our previous studies and this study, a total of 384 sarcomas with complex karyotypes were examined, 83 of which were ATRX deficient (22%). By telomere-specific fluorescence in situ hybridization, 45% (138/308) were alternative lengthening of telomeres positive, 55% (76/138) of which were ATRX deficient. Loss of ATRX was highly associated with alternative lengthening of telomeres (P<0.001). We

  18. Alternative lengthening of telomeres and loss of ATRX are frequent events in pleomorphic and dedifferentiated liposarcomas.

    PubMed

    Lee, Jen-Chieh; Jeng, Yung-Ming; Liau, Jau-Yu; Tsai, Jia-Huei; Hsu, Hung-Han; Yang, Ching-Yao

    2015-08-01

    Telomerase activation and alternative lengthening of telomeres are two major mechanisms of telomere length maintenance. Soft tissue sarcomas appear to use the alternative lengthening of telomeres more frequently. Loss of α-thalassemia/mental retardation syndrome X-linked (ATRX) or death domain-associated protein 6 (DAXX) expression has been implicated in the pathogenesis of alternative telomere lengthening in pancreatic endocrine neoplasm and glioma. The mechanism leading to the alternative lengthening of telomeres in liposarcoma remains unknown. Whereas alternative telomere lengthening was determined to be an indicator of poor prognosis in liposarcomas as a whole, its prognostic power has not been verified in any subtype of liposarcoma. In this study, we characterized the status of alternative telomere lengthening and expression of ATRX and DAXX in 111 liposarcomas (28 well-differentiated, 52 dedifferentiated, 20 myxoid or round cell, and 11 pleomorphic liposarcomas) by telomere fluorescence in situ hybridization and immunohistochemistry, respectively. Alternative lengthening of telomere was observed in 0% (0/16) of well-differentiated, 30% (14/46) of dedifferentiated, 5% (1/19) of myxoid or round cell, and 80% (8/10) of pleomorphic liposarcomas. Eighteen (16%) and one (1%) tumors were negative for ATRX and DAXX immunostaining, respectively. Remarkably, all cases with loss of either ATRX or DAXX expression had alternative lengthening of telomeres, and 83% (19/23) of tumors that had alternative lengthening of telomeres showed loss of either protein. The correlation between loss of either ATRX or DAXX and alternative telomere lengthening was 100% in dedifferentiated liposarcoma. The presence of alternative telomere lengthening in dedifferentiated liposarcoma suggested poor overall survival (hazard ratio=1.954, P=0.077) and was the most significant indicator of short progression-free survival (hazard ratio=3.119, P=0.003). In conclusion, we found that ATRX loss was

  19. Genome rearrangements caused by interstitial telomeric sequences in yeast

    PubMed Central

    Aksenova, Anna Y.; Greenwell, Patricia W.; Dominska, Margaret; Shishkin, Alexander A.; Kim, Jane C.; Petes, Thomas D.; Mirkin, Sergei M.

    2013-01-01

    Interstitial telomeric sequences (ITSs) are present in many eukaryotic genomes and are linked to genome instabilities and disease in humans. The mechanisms responsible for ITS-mediated genome instability are not understood in molecular detail. Here, we use a model Saccharomyces cerevisiae system to characterize genome instability mediated by yeast telomeric (Ytel) repeats embedded within an intron of a reporter gene inside a yeast chromosome. We observed a very high rate of small insertions and deletions within the repeats. We also found frequent gross chromosome rearrangements, including deletions, duplications, inversions, translocations, and formation of acentric minichromosomes. The inversions are a unique class of chromosome rearrangement involving an interaction between the ITS and the true telomere of the chromosome. Because we previously found that Ytel repeats cause strong replication fork stalling, we suggest that formation of double-stranded DNA breaks within the Ytel sequences might be responsible for these gross chromosome rearrangements. PMID:24191060

  20. Telomere length differences between subcutaneous and visceral adipose tissue in humans

    SciTech Connect

    Lakowa, Nicole; Trieu, Nhu; Flehmig, Gesine; Lohmann, Tobias; Schön, Michael R.; Dietrich, Arne; Zeplin, Philip Helge; Langer, Stefan; Stumvoll, Michael; Blüher, Matthias; Klöting, Nora

    2015-02-13

    Adipocyte hypertrophy and hyperplasia have been shown to be associated with shorter telomere length, which may reflect aging, altered cell proliferation and adipose tissue (AT) dysfunction. In individuals with obesity, differences in fat distribution and AT cellular composition may contribute to obesity related metabolic diseases. Here, we tested the hypotheses that telomere lengths (TL) are different between: (1) abdominal subcutaneous and omental fat depots, (2) superficial and deep abdominal subcutaneous AT (SAT), and (3) adipocytes and cells of the stromal vascular fraction (SVF). We further asked whether AT TL is related to age, anthropometric and metabolic traits. TL was analyzed by quantitative PCR in total human genomic DNA isolated from paired subcutaneous and visceral AT of 47 lean and 50 obese individuals. In subgroups, we analyzed TL in isolated small and large adipocytes and SVF cells. We find significantly shorter TL in subcutaneous compared to visceral AT (P < 0.001) which is consistent in men and subgroups of lean and obese, and individuals with or without type 2 diabetes (T2D). Shorter TL in SAT is entirely due to shorter TL in the SVF compared to visceral AT (P < 0.01). SAT TL is most strongly correlated with age (r = −0.205, P < 0.05) and independently of age with HbA1c (r = −0.5, P < 0.05). We found significant TL differences between superficial SAT of lean and obese as well as between individuals with our without T2D, but not between the two layers of SAT. Our data indicate that fat depot differences in TL mainly reflect shorter TL of SVF cells. In addition, we found an age and BMI-independent relationship between shorter TL and HbA1c suggesting that chronic hyperglycemia may impair the regenerative capacity of AT more strongly than obesity alone. - Highlights: • Telomere lengths (TL) differ between fat depots mainly due to different lengths in SVF. • TL is not associated with gender, BMI and T2D. • The tendency for

  1. Mammalian Endogenous Retroviruses.

    PubMed

    Mager, Dixie L; Stoye, Jonathan P

    2015-02-01

    Over 40% of mammalian genomes comprise the products of reverse transcription. Among such retrotransposed sequences are those characterized by the presence of long terminal repeats (LTRs), including the endogenous retroviruses (ERVs), which are inherited genetic elements closely resembling the proviruses formed following exogenous retrovirus infection. Sequences derived from ERVs make up at least 8 to 10% of the human and mouse genomes and range from ancient sequences that predate mammalian divergence to elements that are currently still active. In this chapter we describe the discovery, classification and origins of ERVs in mammals and consider cellular mechanisms that have evolved to control their expression. We also discuss the negative effects of ERVs as agents of genetic disease and cancer and review examples of ERV protein domestication to serve host functions, as in placental development. Finally, we address growing evidence that the gene regulatory potential of ERV LTRs has been exploited multiple times during evolution to regulate genes and gene networks. Thus, although recently endogenized retroviral elements are often pathogenic, those that survive the forces of negative selection become neutral components of the host genome or can be harnessed to serve beneficial roles. PMID:26104559

  2. Dimensions of religious involvement and leukocyte telomere length.

    PubMed

    Hill, Terrence D; Ellison, Christopher G; Burdette, Amy M; Taylor, John; Friedman, Katherine L

    2016-08-01

    Although numerous studies suggest that religious involvement is associated with a wide range of favorable health outcomes, it is unclear whether this general pattern extends to cellular aging. In this paper, we tested whether leukocyte telomere length varies according to several dimensions of religious involvement. We used cross-sectional data from the Nashville Stress and Health Study (2011-2014), a large probability sample of 1252 black and white adults aged 22 to 69 living in Davidson County, TN, USA. Leukocyte telomere length was measured using the monochrome multiplex quantitative polymerase chain reaction method with albumin as the single-copy reference sequence. Dimensions of religious involvement included religiosity, religious support, and religious coping. Our multivariate analyses showed that religiosity (an index of religious attendance, prayer frequency, and religious identity) was positively associated with leukocyte telomere length, even with adjustments for religious support, religious coping, age, gender, race, education, employment status, income, financial strain, stressful life events, marital status, family support, friend support, depressive symptoms, smoking, heavy drinking, and allostatic load. Unlike religiosity, religious support and religious coping were unrelated to leukocyte telomere length across models. Depressive symptoms, smoking, heavy drinking, and allostatic load failed to explain any of the association between religiosity and telomere length. To our knowledge, this is the first population-based study to link religious involvement and cellular aging. Although our data suggest that adults who frequently attend religious services, pray with regularity, and consider themselves to be religious tend to exhibit longer telomeres than those who attend and pray less frequently and do not consider themselves to be religious, additional research is needed to establish the mechanisms underlying this association. PMID:27174242

  3. Telomere Transcripts Target Telomerase in Human Cancer Cells

    PubMed Central

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

    2016-01-01

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

  4. Stress and telomere shortening among central Indian conservation refugees

    PubMed Central

    Zahran, Sammy; Snodgrass, Jeffrey G.; Maranon, David G.; Upadhyay, Chakrapani; Granger, Douglas A.; Bailey, Susan M.

    2015-01-01

    Research links psychosocial stress to premature telomere shortening and accelerated human aging; however, this association has only been demonstrated in so-called “WEIRD” societies (Western, educated, industrialized, rich, and democratic), where stress is typically lower and life expectancies longer. By contrast, we examine stress and telomere shortening in a non-Western setting among a highly stressed population with overall lower life expectancies: poor indigenous people—the Sahariya—who were displaced (between 1998 and 2002) from their ancestral homes in a central Indian wildlife sanctuary. In this setting, we examined adult populations in two representative villages, one relocated to accommodate the introduction of Asiatic lions into the sanctuary (n = 24 individuals), and the other newly isolated in the sanctuary buffer zone after their previous neighbors were moved (n = 22). Our research strategy combined physical stress measures via the salivary analytes cortisol and α-amylase with self-assessments of psychosomatic stress, ethnographic observations, and telomere length assessment [telomere–fluorescence in situ hybridization (TEL-FISH) coupled with 3D imaging of buccal cell nuclei], providing high-resolution data amenable to multilevel statistical analysis. Consistent with expectations, we found significant associations between each of our stress measures—the two salivary analytes and the psychosomatic symptom survey—and telomere length, after adjusting for relevant behavioral, health, and demographic traits. As the first study (to our knowledge) to link stress to telomere length in a non-WEIRD population, our research strengthens the case for stress-induced telomere shortening as a pancultural biomarker of compromised health and aging. PMID:25730846

  5. Regulating telomere length from the inside out: the replication fork model

    PubMed Central

    2016-01-01

    Telomere length is regulated around an equilibrium set point. Telomeres shorten during replication and are lengthened by telomerase. Disruption of the length equilibrium leads to disease; thus, it is important to understand the mechanisms that regulate length at the molecular level. The prevailing protein-counting model for regulating telomerase access to elongate the telomere does not explain accumulating evidence of a role of DNA replication in telomere length regulation. Here I present an alternative model: the replication fork model that can explain how passage of a replication fork and regulation of origin firing affect telomere length. PMID:27401551

  6. Telomerized presenescent osteoblasts prevent bone mass loss in vivo.

    PubMed

    Yudoh, K; Nishioka, K

    2004-06-01

    Previously, we showed that human osteoblasts expressing the human telomerase reverse transcriptase (hTERT) gene exhibited specific survival advantages--the result of breaching the replicative senescence barrier and maintaining the phenotypic and functional properties of primary osteoblasts in vitro over the total replicative capacity of primary osteoblasts. We postulated that rejuvenated osteoblasts may have a potential to correct bone loss or osteopenia in age-related osteoporotic diseases. In the present study, we studied whether telomerized presenescent osteoblasts prevent bone mass loss in vivo. After obtaining the informed consent from a patient with osteoarthritis who underwent the arthroplastic knee surgery, osteoblastic cells were isolated from donor bone sample. We transfected the gene encoding hTERT into human osteoblastic cells. Human bone fragments from a donor were incubated with human hTERT-transfected presenescent (in vitro aged) osteoblasts or mock-transfected presenescent osteoblasts in culture medium containing Matrigel. We subcutaneously implanted human bone fragments with telomerized presenescent osteoblasts or primary presenescent osteoblasts as three-dimensional Matrigel xenografts in severe combined immunodeficiency (SCID) mice (each group: six mice) and analyzed the grafts at 6 weeks after implantation. We also determined whether telomerized osteoblasts affect the bone-forming capacity in vivo, using a well-established mouse transplantation model in which ceramic hydroxyapatite/tricalcium phosphate particles are used as carrier vehicle. Telomerized presenescent osteoblasts were rejuvenated, and maintained the functional properties of young osteoblasts in vitro. Bone mineral content (BMC) and bone mineral density (BMD) were measured by ash weight and dual-energy X-ray absorptiometry, respectively. Whereas BMC and BMD of human bone fragments, which were inoculated with aged osteoblasts in SCID mice, decreased with time, telomerized

  7. New prospects for targeting telomerase beyond the telomere.

    PubMed

    Arndt, Greg M; MacKenzie, Karen L

    2016-08-01

    Telomerase activity is responsible for the maintenance of chromosome end structures (telomeres) and cancer cell immortality in most human malignancies, making telomerase an attractive therapeutic target. The rationale for targeting components of the telomerase holoenzyme has been strengthened by accumulating evidence indicating that these molecules have extra-telomeric functions in tumour cell survival and proliferation. This Review discusses current knowledge of the biogenesis, structure and multiple functions of telomerase-associated molecules intertwined with recent advances in drug discovery approaches. We also describe the fertile ground available for the pursuit of next-generation small-molecule inhibitors of telomerase. PMID:27339602

  8. Examining a scaled dynamical system of telomere shortening

    NASA Astrophysics Data System (ADS)

    Cyrenne, Benoit M.; Gooding, Robert J.

    2015-02-01

    A model of telomere dynamics is proposed and examined. Our model, which extends a previously introduced model that incorporates stem cells as progenitors of new cells, imposes the Hayflick limit, the maximum number of cell divisions that are possible. This new model leads to cell populations for which the average telomere length is not necessarily a monotonically decreasing function of time, in contrast to previously published models. We provide a phase diagram indicating where such results would be expected via the introduction of scaled populations, rate constants and time. The application of this model to available leukocyte baboon data is discussed.

  9. Association of Telomere Length with Breast Cancer Prognostic Factors

    PubMed Central

    Têtu, Bernard; Maunsell, Elizabeth; Poirier, Brigitte; Montoni, Alicia; Rochette, Patrick J.; Diorio, Caroline

    2016-01-01

    Introduction Telomere length, a marker of cell aging, seems to be affected by the same factors thought to be associated with breast cancer prognosis. Objective To examine associations of peripheral blood cell-measured telomere length with traditional and potential prognostic factors in breast cancer patients. Methods 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. Results 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. Conclusions 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

  10. Telomere Length Maintenance and Cardio-Metabolic Disease Prevention Through Exercise Training.

    PubMed

    Denham, Joshua; O'Brien, Brendan J; Charchar, Fadi J

    2016-09-01

    Telomeres are tandem repeat DNA sequences located at distal ends of chromosomes that protect against genomic DNA degradation and chromosomal instability. Excessive telomere shortening leads to cellular senescence and for this reason telomere length is a marker of biological age. Abnormally short telomeres may culminate in the manifestation of a number of cardio-metabolic diseases. Age-related cardio-metabolic diseases attributable to an inactive lifestyle, such as obesity, type 2 diabetes mellitus and cardiovascular disease, are associated with short leukocyte telomeres. Exercise training prevents and manages the symptoms of many cardio-metabolic diseases whilst concurrently maintaining telomere length. The positive relationship between exercise training, physical fitness and telomere length raises the possibility of a mediating role of telomeres in chronic disease prevention via exercise. Further elucidation of the underpinning molecular mechanisms of how exercise maintains telomere length should provide crucial information on how physical activity can be best structured to combat the chronic disease epidemic and improve the human health span. Here, we synthesise and discuss the current evidence on the impact of physical activity and cardiorespiratory fitness on telomere dynamics. We provide the molecular mechanisms with a known role in exercise-induced telomere length maintenance and highlight unexplored, alternative pathways ripe for future investigations. PMID:26914269

  11. Genetic Architecture of Natural Variation of Telomere Length in Arabidopsis thaliana

    PubMed Central

    Fulcher, Nick; Teubenbacher, Astrid; Kerdaffrec, Envel; Farlow, Ashley; Nordborg, Magnus; Riha, Karel

    2015-01-01

    Telomeres represent the repetitive sequences that cap chromosome ends and are essential for their protection. Telomere length is known to be highly heritable and is derived from a homeostatic balance between telomeric lengthening and shortening activities. Specific loci that form the genetic framework underlying telomere length homeostasis, however, are not well understood. To investigate the extent of natural variation of telomere length in Arabidopsis thaliana, we examined 229 worldwide accessions by terminal restriction fragment analysis. The results showed a wide range of telomere lengths that are specific to individual accessions. To identify loci that are responsible for this variation, we adopted a quantitative trait loci (QTL) mapping approach with multiple recombinant inbred line (RIL) populations. A doubled haploid RIL population was first produced using centromere-mediated genome elimination between accessions with long (Pro-0) and intermediate (Col-0) telomere lengths. Composite interval mapping analysis of this population along with two established RIL populations (Ler-2/Cvi-0 and Est-1/Col-0) revealed a number of shared and unique QTL. QTL detected in the Ler-2/Cvi-0 population were examined using near isogenic lines that confirmed causative regions on chromosomes 1 and 2. In conclusion, this work describes the extent of natural variation of telomere length in A. thaliana, identifies a network of QTL that influence telomere length homeostasis, examines telomere length dynamics in plants with hybrid backgrounds, and shows the effects of two identified regions on telomere length regulation. PMID:25488978

  12. The Role of Telomere Biology in Bone Marrow Failure and Other Disorders

    PubMed Central

    Savage, Sharon A.; Alter, Blanche P.

    2008-01-01

    Telomeres, consisting of nucleotide repeats and a protein complex at chromosome ends, are essential in maintaining chromosomal integrity. Dyskeratosis congenita (DC) is the inherited bone marrow failure syndrome (IBMFS) that epitomizes the effects of abnormal telomere biology. Patients with DC have extremely short telomere lengths (<1st percentile) and many have mutations in telomere biology genes. Interpretation of telomere length in other IBMFSs is less straightforward. Abnormal telomere shortening has been reported in patients with apparently acquired hematologic disorders, including aplastic anemia, myeolodysplasia, paroxysmal nocturnal hemoglobinuria, and leukemia. In these disorders, the shortest lived cells have the shortest telomeres, suggestive of increased hematopoietic stress. Telomeres are also markers of replicative and/or oxidative stress in other complex disease pathways, such as inflammation, stress, and carcinogenesis. The spectrum of related disorders caused by mutations in telomere biology genes extends beyond classical DC to include marrow failure that does not respond to immunosuppression, idiopathic pulmonary fibrosis, and possibly other syndromes. We suggest that such patients are categorized as having an inherited disorder of telomere biology. Longitudinal studies of patients with very short telomeres but without classical DC are necessary to further understand the long-term sequelae, such as malignancy, osteonecrosis/osteoporosis, and pulmonary and liver disease. PMID:18160098

  13. Coordination of transposon expression with DNA replication in the targeting of telomeric retrotransposons in Drosophila

    PubMed Central

    Zhang, Liang; Beaucher, Michelle; Cheng, Yan; Rong, Yikang S

    2014-01-01

    In Drosophila, a group of retrotransposons is mobilized exclusively to telomeres in a sequence-independent manner. How they target chromosome ends is not understood. Here, we focused on the telomeric element HeT-A and characterized the cell cycle expression and cytological distribution of its protein and RNA products. We determined the timing of telomere replication by creating a single lacO-marked telomere and provide evidence suggesting that transposon expression and recruitment to telomeres is linked to telomere replication. The HeT-A-encoded ORF1p protein is expressed predominantly in S phase, particularly in early S phase. Orf1p binds HeT-A transcripts and forms spherical structures at telomeres undergoing DNA replication. HeT-A sphere formation requires Verrocchio, a putative homolog of the conserved Stn1 telomeric protein. Our results suggest that coupling of telomere elongation and telomere replication is a universal feature, and raise the possibility that transposon recruitment to Drosophila telomeres is mechanistically related to telomerase recruitment in other organisms. Our study also supports a co-adaptive relationship between the Drosophila host and HeT-A mobile elements. PMID:24733842

  14. Impact of chemotherapy on telomere-length in sporadic and familial breast cancer patients

    PubMed Central

    Benitez-Buelga, C.; Sanchez-Barroso, L.; Gallardo, M.; Apellániz-Ruiz, María; Inglada-Pérez, L.; Yanowski, K.; Carrillo, J.; Garcia-Estevez, L.; Calvo, I.; Perona, R.; Urioste, M.; Osorio, A.; Blasco, MA.; Rodriguez-Antona, C.; Benitez, J.

    2015-01-01

    Purpose Recently, we observed that telomeres of BRCA1/2 mutation carriers were shorter than those of controls or sporadic breast cancer patients, suggesting that mutations in these genes might be responsible for this event. Given the contradictory results reported in the literature, we tested whether other parameters, such as chemotherapy, could be modifying telomere-length. Methods We performed a cross-sectional study measuring leukocyte telomere-length of 266 sporadic breasts cancer patients treated with first-line chemotherapy, with a median follow up of 240 days. Additionally, we performed both cross-sectional and longitudinal studies in a series of 236 familial breast cancer patients that included affected and non-affected BRCA1/2 mutation carriers. We have measured in leukocytes from peripheral blood: The telomere-length, percentage of short telomeres (<3Kb), telomerase activity levels and the annual telomere shortening speed. Results In sporadic cases we found that chemotherapy exerts a transient telomere shortening effect (around 2 years) that varies depending on the drug combination. In familial cases, only patients receiving treatment were associated with telomere shortening but they recovered normal telomere-length after a period of two years. Conclusion Chemotherapy affects telomere-length and should be considered in the studies that correlate telomere-length with disease susceptibility. PMID:25528024

  15. Telomere regulation during ageing and tumorigenesis of the grey mouse lemur.

    PubMed

    Trochet, Delphine; Mergui, Xénia; Ivkovic, Ivana; Porreca, Rosa Maria; Gerbault-Seureau, Michèle; Sidibe, Assitan; Richard, Florence; Londono-Vallejo, Arturo; Perret, Martine; Aujard, Fabienne; Riou, Jean-François

    2015-06-01

    Telomere erosion leading to replicative senescence has been well documented in human and anthropoid primates, and provides a clue against tumorigenesis. In contrast, other mammals, such as laboratory mice, with short lifespan and low body weight mass have different telomere biology without replicative senescence. We analyzed telomere biology in the grey mouse lemur, a small prosimian model with a relative long lifespan currently used in ageing research. We report an average telomere length by telomere restriction fragment (TRF) among the longest reported so far for a primate species (25-30 kb), but without detectable overall telomere shortening with ageing on blood samples. However, we demonstrate using universal STELA (Single Telomere Length Amplification) the existence of short telomeres, the increase of which, while correlating with ageing might be related to another mechanism than replicative senescence. We also found a low stringency of telomerase restriction in tissues and an ease to immortalize fibroblasts in vitro upon spontaneous telomerase activation. Finally, we describe the first grey mouse lemur cancer cell line showing a dramatic telomere shortening and high telomerase activity associated with polyploidy. Our overall results suggest that telomere biology in grey mouse lemur is an exception among primates, with at best a physiologically limited replicative telomere ageing and closest to that observed in small rodents. PMID:25882681

  16. Accelerated telomere attrition in children and teenagers with α1-antitrypsin deficiency.

    PubMed

    Escribano, Amparo; Pastor, Sara; Reula, Ana; Castillo, Silvia; Vicente, Silvia; Sanz, Francisco; Casas, Francisco; Torres, María; Fernández-Fabrellas, Estrella; Codoñer-Franch, Pilar; Dasí, Francisco

    2016-08-01

    Numerous studies have shown that oxidative stress accelerates telomere shortening in several lung pathologies. Since oxidative stress is involved in the pathophysiology of α1-antitrypsin deficiency (AATD), we hypothesised that telomere shortening would be accelerated in AATD patients. This study aimed to assess telomere length in AATD patients and to study its association with α1-antitrypsin phenotypes.Telomere length, telomerase activity, telomerase reverse transcriptase (hTERT) expression and biomarkers of oxidative stress were measured in 62 children and teenagers (aged 2-18 years) diagnosed with AATD and 18 controls (aged 3-16 years).Our results show that intermediate-risk (MZ; SZ) and high-risk (ZZ) AATD patients have significantly shorter telomeres and increased oxidative stress than controls. Correlation studies indicate that telomere length was related to oxidative stress markers in AATD patients. Multiple hypothesis testing revealed an association between telomere length, telomerase activity, hTERT expression and AATD phenotypes; high-risk patients showed shorter telomeres, lower hTERT expression and decreased telomerase activity than intermediate-risk and low-risk patients.AATD patients show evidence of increased oxidative stress leading to telomere attrition. An association between telomere and α1-antitrypsin phenotypes is observed suggesting that telomere length could be a promising biomarker for AATD disease progression. PMID:27390278

  17. Genetic architecture of natural variation of telomere length in Arabidopsis thaliana.

    PubMed

    Fulcher, Nick; Teubenbacher, Astrid; Kerdaffrec, Envel; Farlow, Ashley; Nordborg, Magnus; Riha, Karel

    2015-02-01

    Telomeres represent the repetitive sequences that cap chromosome ends and are essential for their protection. Telomere length is known to be highly heritable and is derived from a homeostatic balance between telomeric lengthening and shortening activities. Specific loci that form the genetic framework underlying telomere length homeostasis, however, are not well understood. To investigate the extent of natural variation of telomere length in Arabidopsis thaliana, we examined 229 worldwide accessions by terminal restriction fragment analysis. The results showed a wide range of telomere lengths that are specific to individual accessions. To identify loci that are responsible for this variation, we adopted a quantitative trait loci (QTL) mapping approach with multiple recombinant inbred line (RIL) populations. A doubled haploid RIL population was first produced using centromere-mediated genome elimination between accessions with long (Pro-0) and intermediate (Col-0) telomere lengths. Composite interval mapping analysis of this population along with two established RIL populations (Ler-2/Cvi-0 and Est-1/Col-0) revealed a number of shared and unique QTL. QTL detected in the Ler-2/Cvi-0 population were examined using near isogenic lines that confirmed causative regions on chromosomes 1 and 2. In conclusion, this work describes the extent of natural variation of telomere length in A. thaliana, identifies a network of QTL that influence telomere length homeostasis, examines telomere length dynamics in plants with hybrid backgrounds, and shows the effects of two identified regions on telomere length regulation. PMID:25488978

  18. Hepatocellular telomere shortening correlates with chromosomal instability and the development of human hepatoma.

    PubMed

    Plentz, Ruben R; Caselitz, Martin; Bleck, Joerg S; Gebel, Michael; Flemming, Peer; Kubicka, Stefan; Manns, Michael P; Rudolph, K Lenhard

    2004-07-01

    The telomere hypothesis of cancer initiation indicates that telomere shortening initiates cancer by induction of chromosomal instability. To test whether this hypothesis applies to human hepatocellular carcinoma (HCC), we analyzed the telomere length of hepatocytes in cytological smears of fine-needle biopsies of liver tumors from patients with cirrhosis (n = 39). The tumors consisted of 24 HCC and 15 regenerative nodules as diagnosed by combined histological and cytological diagnostics. In addition, we analyzed the telomere length of hepatocytes in HCC and surrounding noncancerous liver tissue within individual patients in another cohort of 10 patients with cirrhosis. Telomere length analysis of hepatocytes was correlated with tumor pathology and ploidy grade of the tumors, which was analyzed by cytophotometry. Telomeres were significantly shortened in hepatocytes of HCC compared to hepatocytes in regenerative nodules or surrounding noncancerous liver tissue. Hepatocyte telomere shortening in HCC was independent of the patient's age. There was no overlap in mean telomere lengths of individual samples when comparing HCC with regenerative nodules or noncancerous surrounding liver. Within the HCC group, telomeres were significantly shorter in hepatocytes of aneuploid tumors compared to diploid tumors. In conclusion, our data suggest that the telomere hypothesis of cancer initiation applies to human HCC and that cell type-specific telomere length analysis might indicate the risk of HCC development. PMID:15239089

  19. Computel: Computation of Mean Telomere Length from Whole-Genome Next-Generation Sequencing Data

    PubMed Central

    Nersisyan, Lilit; Arakelyan, Arsen

    2015-01-01

    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. PMID:25923330

  20. Targeting the telomere and shelterin complex for cancer therapy: current views and future perspectives

    PubMed Central

    Bilsland, Alan E; Cairney, Claire J; Nicol Keith, W

    2011-01-01

    Abstract Aberrant telomere homeostasis is essential for cell immortality, enabling cells to evade telomere dependent senescence. Disruption of telomere structure and function in cancer cells is highly toxic as shown by detailed pre-clinical evaluation of telomerase inhibitors. Under telomerase inhibition, cells must divide sufficiently frequently to allow one or more telomeres to shorten to an unprotected length. Functioning telomeres are disguised from the DNA damage machinery by DNA remodelling and other activities of the telomere binding complex shelterin. Direct interference with shelterin has been shown to result in cell killing and small molecules directly targeting telomere DNA also have anti-tumour effects partially dependent on shelterin disruption. However, shelterin components have not generally been regarded as therapeutic targets in their own right. In this review, we explore the possibilities for therapeutic targeting of the shelterin complex. PMID:21199331

  1. Telomerase RNA stem terminus element affects template boundary element function, telomere sequence, and shelterin binding

    PubMed Central

    Webb, Christopher J.; Zakian, Virginia A.

    2015-01-01

    The stem terminus element (STE), which was discovered 13 y ago in human telomerase RNA, is required for telomerase activity, yet its mode of action is unknown. We report that the Schizosaccharomyces pombe telomerase RNA, TER1 (telomerase RNA 1), also contains a STE, which is essential for telomere maintenance. Cells expressing a partial loss-of-function TER1 STE allele maintained short stable telomeres by a recombination-independent mechanism. Remarkably, the mutant telomere sequence was different from that of wild-type cells. Generation of the altered sequence is explained by reverse transcription into the template boundary element, demonstrating that the STE helps maintain template boundary element function. The altered telomeres bound less Pot1 (protection of telomeres 1) and Taz1 (telomere-associated in Schizosaccharomyces pombe 1) in vivo. Thus, the S. pombe STE, although distant from the template, ensures proper telomere sequence, which in turn promotes proper assembly of the shelterin complex. PMID:26305931

  2. Getting it done at the ends: Pif1 family DNA helicases and telomeres.

    PubMed

    Geronimo, Carly L; Zakian, Virginia A

    2016-08-01

    It is widely appreciated that the ends of linear DNA molecules cannot be fully replicated by the conventional replication apparatus. Less well known is that semi-conservative replication of telomeric DNA also presents problems for DNA replication. These problems likely arise from the atypical chromatin structure of telomeres, the GC-richness of telomeric DNA that makes it prone to forming DNA secondary structures, and from RNA-DNA hybrids, formed by transcripts of one or both DNA strands. Given the different aspects of telomeres that complicate their replication, it is not surprising that multiple DNA helicases promote replication of telomeric DNA. This review focuses on one such class of DNA helicases, the Pif1 family of 5'-3' DNA helicases. In budding and fission yeasts, Pif1 family helicases impact both telomerase-mediated and semi-conservative replication of telomeric DNA as well as recombination-mediated telomere lengthening. PMID:27233114

  3. The DNA structure and sequence preferences of WRN underlie its function in telomeric recombination events

    PubMed Central

    Edwards, Deanna N.; Machwe, Amrita; Chen, Li; Bohr, Vilhelm A.; Orren, David K.

    2015-01-01

    Telomeric abnormalities caused by loss of function of the RecQ helicase WRN are linked to the multiple premature ageing phenotypes that characterize Werner syndrome. Here we examine WRN's role in telomeric maintenance, by comparing its action on a variety of DNA structures without or with telomeric sequences. Our results show that WRN clearly prefers to act on strand invasion intermediates in a manner that favours strand invasion and exchange. Moreover, WRN unwinding of these recombination structures is further enhanced when the invading strand contains at least three G-rich single-stranded telomeric repeats. These selectivities are most pronounced at NaCl concentrations within the reported intranuclear monovalent cation concentration range, and are partly conferred by WRN's C-terminal region. Importantly, WRN's specificity for the G-rich telomeric sequence within this precise structural context is particularly relevant to telomere metabolism and strongly suggests a physiological role in telomeric recombination processes, including T-loop dynamics. PMID:26420422

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

    PubMed

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

    2013-11-15

    Telomeres are nucleoprotein structures that cap the ends of the linear eukaryotic chromosomes, thus protecting their stability and integrity. They play important roles in DNA replication and repair and are central to our understanding of aging and cancer development. In rapidly dividing cells, telomere length is maintained by the activity of telomerase. About 400 TLM (telomere length maintenance) genes have been identified in yeast, as participants of an intricate homeostasis network that keeps telomere length constant. Two papers have recently shown that despite this extremely complex control, telomere length can be manipulated by external stimuli. These results have profound implications for our understanding of cellular homeostatic systems in general and of telomere length maintenance in particular. In addition, they point to the possibility of developing aging and cancer therapies based on telomere length manipulation. PMID:24091626

  5. The paradox of longer sperm telomeres in older men's testes: a birth-cohort effect caused by transgenerational telomere erosion in the female germline.

    PubMed

    Stindl, Reinhard

    2016-01-01

    Longer telomeres in the somatic cells of an individual have been regarded as a marker of youth and biological fitness within a population. Yet, several research groups have reported the surprising findings of longer telomeres in the germ cells of older men, which translated into longer leukocyte telomere length in their offspring. Although all these studies were purely cross-sectional, a longitudinal trend in the aging testes of individual males was taken for granted. Recently, a high-profile study reported a negative birth-cohort effect on leukocyte mean telomere length in human populations, namely the progressive loss of telomeric sequence between healthy human generations. This is what I based my theory of telomere-driven macroevolution on, 12 years ago. On the basis of published data on telomere length inheritance, I identified the source of human intergenerational telomere erosion in the female germline. Accordingly, because of the resulting birth-cohort effect, there is no need for any paradoxical telomere lengthening in older men's gonads to interpret the old-father-long-telomered-offspring data. PMID:26858775

  6. Human regulator of telomere elongation helicase 1 (RTEL1) is required for the nuclear and cytoplasmic trafficking of pre-U2 RNA

    PubMed Central

    Schertzer, Michael; Jouravleva, Karina; Perderiset, Mylene; Dingli, Florent; Loew, Damarys; Le Guen, Tangui; Bardoni, Barbara; de Villartay, Jean-Pierre; Revy, Patrick; Londoño-Vallejo, Arturo

    2015-01-01

    Hoyeraal-Hreidarsson syndrome (HHS) is a severe form of Dyskeratosis congenita characterized by developmental defects, bone marrow failure and immunodeficiency and has been associated with telomere dysfunction. Recently, mutations in Regulator of Telomere ELongation helicase 1 (RTEL1), a helicase first identified in Mus musculus as being responsible for the maintenance of long telomeres, have been identified in several HHS patients. Here we show that RTEL1 is required for the export and the correct cytoplasmic trafficking of the small nuclear (sn) RNA pre-U2, a component of the major spliceosome complex. RTEL1-HHS cells show abnormal subcellular partitioning of pre-U2, defects in the recycling of ribonucleotide proteins (RNP) in the cytoplasm and splicing defects. While most of these phenotypes can be suppressed by re-expressing the wild-type protein in RTEL1-HHS cells, expression of RTEL1 mutated variants in immortalized cells provokes cytoplasmic mislocalizations of pre-U2 and other RNP components, as well as splicing defects, thus phenocopying RTEL1-HHS cellular defects. Strikingly, expression of a cytoplasmic form of RTEL1 is sufficient to correct RNP mislocalizations both in RTEL1–HHS cells and in cells expressing nuclear mutated forms of RTEL1. This work unravels completely unanticipated roles for RTEL1 in RNP trafficking and strongly suggests that defects in RNP biogenesis pathways contribute to the pathology of HHS. PMID:25628358

  7. The mammalian blastocyst.

    PubMed

    Frankenberg, Stephen R; de Barros, Flavia R O; Rossant, Janet; Renfree, Marilyn B

    2016-01-01

    The blastocyst is a mammalian invention that carries the embryo from cleavage to gastrulation. For such a simple structure, it exhibits remarkable diversity in its mode of formation, morphology, longevity, and intimacy with the uterine endometrium. This review explores this diversity in the light of the evolution of viviparity, comparing the three main groups of mammals: monotremes, marsupials, and eutherians. The principal drivers in blastocyst evolution were loss of yolk coupled with evolution of the placenta. An important outcome of blastocyst development is differentiation of two extraembryonic lineages (trophoblast and hypoblast) that contribute to the placenta. While in many species trophoblast segregation is often coupled with blastocyst formation, in marsupials and at least some Afrotherians, these events do not coincide. Thus, many questions regarding the conservation of molecular mechanisms controlling these events are of great interest but currently unresolved. For further resources related to this article, please visit the WIREs website. PMID:26799266

  8. Mammalian phospholipase C.

    PubMed

    Kadamur, Ganesh; Ross, Elliott M

    2013-01-01

    Phospholipase C (PLC) converts phosphatidylinositol 4,5-bisphosphate (PIP(2)) to inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG). DAG and IP(3) each control diverse cellular processes and are also substrates for synthesis of other important signaling molecules. PLC is thus central to many important interlocking regulatory networks. Mammals express six families of PLCs, each with both unique and overlapping controls over expression and subcellular distribution. Each PLC also responds acutely to its own spectrum of activators that includes heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca(2+), and phospholipids. Mammalian PLCs are autoinhibited by a region in the catalytic TIM barrel domain that is the target of much of their acute regulation. In combination, the PLCs act as a signaling nexus that integrates numerous signaling inputs, critically governs PIP(2) levels, and regulates production of important second messengers to determine cell behavior over the millisecond to hour timescale. PMID:23140367

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

    PubMed Central

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

    2014-01-01

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

  10. Traffic noise exposure affects telomere length in nestling house sparrows.

    PubMed

    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. PMID:26382074

  11. Protein landscape at Drosophila melanogaster telomere-associated sequence repeats.

    PubMed

    Antão, José M; Mason, James M; Déjardin, Jérôme; Kingston, Robert E

    2012-06-01

    The specific set of proteins bound at each genomic locus contributes decisively to regulatory processes and to the identity of a cell. Understanding of the function of a particular locus requires the knowledge of what factors interact with that locus and how the protein composition changes in different cell types or during the response to internal and external signals. Proteomic analysis of isolated chromatin segments (PICh) was developed as a tool to target, purify, and identify proteins associated with a defined locus and was shown to allow the purification of human telomeric chromatin. Here we have developed this method to identify proteins that interact with the Drosophila telomere-associated sequence (TAS) repeats. Several of the purified factors were validated as novel TAS-bound proteins by chromatin immunoprecipitation, and the Brahma complex was confirmed as a dominant modifier of telomeric position effect through the use of a genetic test. These results offer information on the efficacy of applying the PICh protocol to loci with sequence more complex than that found at human telomeres and identify proteins that bind to the TAS repeats, which might contribute to TAS biology and chromatin silencing. PMID:22493064

  12. Coevolution of the telomeric retrotransposons across Drosophila species.

    PubMed Central

    Casacuberta, Elena; Pardue, Mary-Lou

    2002-01-01

    As in other eukaryotes, telomeres in Drosophila melanogaster are composed of long arrays of repeated DNA sequences. Remarkably, in D. melanogaster these repeats are produced, not by telomerase, but by successive transpositions of two telomere-specific retrotransposons, HeT-A and TART. These are the only transposable elements known to be completely dedicated to a role in chromosomes, a finding that provides an opportunity for investigating questions about the evolution of telomeres, telomerase, and the transposable elements themselves. Recent studies of D. yakuba revealed the presence of HeT-A elements with precisely the same unusual characteristics as HeT-A(mel) although they had only 55% nucleotide sequence identity. We now report that the second element, TART, is also a telomere component in D. yakuba; thus, these two elements have been evolving together since before the separation of the melanogaster and yakuba species complexes. Like HeT-A(yak), TART(yak) is undergoing concerted sequence evolution, yet they retain the unusual features TART(mel) shares with HeT-A(mel). There are at least two subfamilies of TART(yak) with significantly different sequence and expression. Surprisingly, one subfamily of TART(yak) has >95% sequence identity with a subfamily of TART(mel) and shows similar transcription patterns. As in D. melanogaster, other retrotransposons are excluded from the D. yakuba terminal arrays studied to date. PMID:12136015

  13. Drug addiction is associated with leukocyte telomere length

    PubMed Central

    Yang, Zhaoyang; Ye, Junyi; Li, Candong; Zhou, Daizhan; Shen, Qin; Wu, Ji; Cao, Lan; Wang, Ting; Cui, Daxiang; He, Shigang; Qi, Guoyang; He, Lin; Liu, Yun

    2013-01-01

    Telomeres are protective chromosomal structures that play a key role in preserving genomic stability. Telomere length is known to be associated with ageing and age-related diseases. To study the impairment of telomeres induced by drug abuse, we conducted an association study in the Chinese Han population. Multivariate linear regression analyses were performed to evaluate the correlation of leukocyte telomere length (LTL) with addiction control status adjusted for age and gender. The results showed that drug abusers exhibited significantly shorter LTLs than controls (P = 1.32e−06). The time before relapse also presented an inverse correlation with LTL (P = 0.02). Drug abusers who had used heroin and diazepam displayed a shorter LTL than those taking other drugs (P = 0.018 and P = 0.009, respectively). Drug abusers who had ingested drugs via snuff exhibited longer LTLs than those using other methods (P = 0.02). These observations may offer a partial explanation for the effects of drug addiction on health. PMID:23528991

  14. Analyses and comparisons of telomerase activity and telomere length in human T and B cells: Insights for epidemiology of telomere maintenance

    PubMed Central

    Lin, Jue; Epel, Elissa; Cheon, Joshua; Kroenke, Candyce; Sinclair, Elizabeth; Bigos, Marty; Wolkowitz, Owen; Mellon, Synthia; Blackburn, Elizabeth

    2012-01-01

    Telomeres are the DNA–protein complexes that protect the ends of eukaryotic chromosomes. The cellular enzyme telomerase counteracts telomere shortening by adding telomeric DNA. A growing body of literature links shorter telomere length and lower telomerase activity with various age-related diseases and earlier mortality. Thus, leukocyte telomere length (LTL) and telomerase activity are emerging both as biomarkers and contributing factors for age-related diseases. However, no clinical study has directly examined telomerase activity and telomere length in different lymphocyte subtypes isolated from the same donors, which could offer insight into the summary measure of leukocyte telomere maintenance. We report the first quantitative data in humans examining both levels of telomerase activity and telomere length in four lymphocyte subpopulations from the same donors—CD4+, CD8+CD28+ and CD8+CD28− T cells and B cells, as well as total PBMCs—in a cohort of healthy women. We found that B cells had the highest telomerase activity and longest telomere length; CD4+ T cells had slightly higher telomerase activity than CD8+CD28+ T cells, and similar telomere length. Consistent with earlier reports that CD8+CD28−T cells are replicatively senescent cells, they had the lowest telomerase activity and shortest telomere length. In addition, a higher percentage of CD8+CD28− T cells correlated with shorter total PBMC TL (r = −0.26, p = 0.05). Interestingly, telomerase activities of CD4+ and CD8+CD28+ T cells from the same individual were strongly correlated (r = 0.55, r < 0.001), indicating possible common mechanisms for telomerase activity regulation in these two cell subtypes. These data will facilitate the understanding of leukocyte aging and its relationship to human health. PMID:19837074

  15. The Transcription Factor ATF5 Mediates a Mammalian Mitochondrial UPR.

    PubMed

    Fiorese, Christopher J; Schulz, Anna M; Lin, Yi-Fan; Rosin, Nadine; Pellegrino, Mark W; Haynes, Cole M

    2016-08-01

    Mitochondrial dysfunction is pervasive in human pathologies such as neurodegeneration, diabetes, cancer, and pathogen infections as well as during normal aging. Cells sense and respond to mitochondrial dysfunction by activating a protective transcriptional program known as the mitochondrial unfolded protein response (UPR(mt)), which includes genes that promote mitochondrial protein homeostasis and the recovery of defective organelles [1, 2]. Work in Caenorhabditis elegans has shown that the UPR(mt) is regulated by the transcription factor ATFS-1, which is regulated by organelle partitioning. Normally, ATFS-1 accumulates within mitochondria, but during respiratory chain dysfunction, high levels of reactive oxygen species (ROS), or mitochondrial protein folding stress, a percentage of ATFS-1 accumulates in the cytosol and traffics to the nucleus where it activates the UPR(mt) [2]. While similar transcriptional responses have been described in mammals [3, 4], how the UPR(mt) is regulated remains unclear. Here, we describe a mammalian transcription factor, ATF5, which is regulated similarly to ATFS-1 and induces a similar transcriptional response. ATF5 expression can rescue UPR(mt) signaling in atfs-1-deficient worms requiring the same UPR(mt) promoter element identified in C. elegans. Furthermore, mammalian cells require ATF5 to maintain mitochondrial activity during mitochondrial stress and promote organelle recovery. Combined, these data suggest that regulation of the UPR(mt) is conserved from worms to mammals. PMID:27426517

  16. [Neurogenic erectile dysfunction].

    PubMed

    Ramos, Antonio Sánchez; Durán, Juan Antonio Godino; Oliviero, Antonio

    2010-10-01

    Neurogenic erectile dysfunction is a consequence of alterations in neural pathways, autonomic, somatic, the combination of both or brain components that induce erection. This review aims to explain the physiopathological mechanisms of the most frequent neurological alterations causing erectile dysfunction and sexual disorders. PMID:20978292

  17. Expression profile of telomere-associated genes in multiple myeloma

    PubMed Central

    de la Guardia, Rafael Díaz; Catalina, Purificación; Panero, Julieta; Elosua, Carolina; Pulgarin, Andrés; López, María Belén; Ayllón, Verónica; Ligero, Gertrudis; Slavutsky, Irma; Leone, Paola E

    2012-01-01

    To further contribute to the understanding of multiple myeloma, we have focused our research interests on the mechanisms by which tumour plasma cells have a higher survival rate than normal plasma cells. In this article, we study the expression profile of genes involved in the regulation and protection of telomere length, telomerase activity and apoptosis in samples from patients with monoclonal gammopathy of undetermined significance, smouldering multiple myeloma, multiple myeloma (MM) and plasma cell leukaemia (PCL), as well as several human myeloma cell lines (HMCLs). Using conventional cytogenetic and fluorescence in situ hybridization studies, we identified a high number of telomeric associations (TAs). Moreover, telomere length measurements by terminal restriction fragment (TRF) assay showed a shorter mean TRF peak value, with a consistent correlation with the number of TAs. Using gene expression arrays and quantitative PCR we identified the hTERT gene together with 16 other genes directly involved in telomere length maintenance: HSPA9, KRAS, RB1, members of the Small nucleolar ribonucleoproteins family, A/B subfamily of ubiquitously expressed heterogeneous nuclear ribonucleoproteins, and 14-3-3 family. The expression levels of these genes were even higher than those in human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), which have unlimited proliferation capacity. In conclusion, the gene signature suggests that MM tumour cells are able to maintain stable short telomere lengths without exceeding the short critical length, allowing cell divisions to continue. We propose that this could be a mechanism contributing to MM tumour cells expansion in the bone marrow (BM). PMID:22947336

  18. Genomic Organization of the Drosophila Telomere RetrotransposableElements

    SciTech Connect

    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.

  19. [Pharmacotherapy of erectile dysfunction].

    PubMed

    Kovalev, V A; Koroleva, S V; Kamalov, A A

    2000-01-01

    Among the drugs used to treat erectile dysfunction most common are prostaglandins El, viagra, iochimbin, vasodilators and desaggregants, vitamins, biogenic stimulators, etc. The comparative analysis of their efficacy was made in 360 patients with erectile dysfunction, primarily at subcompensated stage, aged 17-83 years. Organic and psychogenic erectile dysfunctions were diagnosed in 69 and 31% of the patients, respectively. Intracavernous injections of prostaglandin El (Caverject) were effective in 74%, transurethral alprostadil (MUSE) when adjusting the dose--in 38.7% of the patients. Iochimbin in patients with organic and psychogenic forms of erectile dysfunctions was effective in 25 and 40% of patients, respectively. In 26.3 and 19% of such patients the response was obtained after use of the combination including xantinol, nicotinate, trental, biogenic stimulators and adaptogens. Viagra was effective in 60 and 77.3% of patients with psychogenic and organic erectile dysfunctions, respectively. PMID:16856460

  20. Generation of mice with longer and better preserved telomeres in the absence of genetic manipulations

    PubMed Central

    Varela, Elisa; Muñoz-Lorente, Miguel A.; Tejera, Agueda M.; Ortega, Sagrario; Blasco, Maria A.

    2016-01-01

    Although telomere length is genetically determined, mouse embryonic stem (ES) cells with telomeres of twice the normal size have been generated. Here, we use such ES cells with ‘hyper-long' telomeres, which also express green fluorescent protein (GFP), to generate chimaeric mice containing cells with both hyper-long and normal telomeres. We show that chimaeric mice contain GFP-positive cells in all mouse tissues, display normal tissue histology and normal survival. Both hyper-long and normal telomeres shorten with age, but GFP-positive cells retain longer telomeres as mice age. Chimaeric mice with hyper-long telomeres also accumulate fewer cells with short telomeres and less DNA damage with age, and express lower levels of p53. In highly renewing compartments, such as the blood, cells with hyper-long telomeres are longitudinally maintained or enriched with age. We further show that wound-healing rates in the skin are increased in chimaeric mice. Our work demonstrates that mice with functional, longer and better preserved telomeres can be generated without the need for genetic manipulations, such as TERT overexpression. PMID:27252083

  1. The role of telomeres and telomerase in hematologic malignancies and hematopoietic stem cell transplantation

    PubMed Central

    2014-01-01

    Telomeres are specific nucleoprotein structures at the ends of eukaryotic chromosomes. Telomeres and telomere-associated proteins maintain genome stability by protecting the ends of chromosomes from fusion and degradation. In normal somatic cells, the length of the telomeres gradually becomes shortened with cell division. In tumor cells, the shortening of telomeres length is accelerated under the increased proliferation pressure. However, it will be maintained at an extremely short length as the result of activation of telomerase. Significantly shortened telomeres, activation of telomerase, and altered expression of telomere-associated proteins are common features of various hematologic malignancies and are related with progression or chemotherapy resistance in these diseases. In patients who have received hematopoietic stem cell transplantation (HSCT), the telomere length and the telomerase activity of the engrafted donor cells have a significant influence on HSCT outcomes. Transplantation-related factors should be taken into consideration because of their impacts on telomere homeostasis. As activation of telomerase is widespread in tumor cells, it has been employed as a target point in the treatment of neoplastic hematologic disorders. In this review, the characteristics and roles of telomeres and telomerase both in hematologic malignancies and in HSCT will be summarized. The current status of telomerase-targeted therapies utilized in the treatment of hematologic malignancies will also be reviewed. PMID:25139287

  2. Beyond Telomerase: Telomere Instability as a Novel Target for Cancer Therapy

    PubMed Central

    Fadri-Moskwik, Maria; Zhou, Qing; Chai, Weihang

    2016-01-01

    Telomeres are areas of heterochromatin composed of TTAGGG repeats located at the ends of linear chromosomes. They play a critical role in keeping genome stable and preventing premature aging diseases and the development of cancer. Characterizing mechanisms of telomere maintenance and understanding how their deregulation contributes to human diseases are therefore important for developing novel therapies. A key mechanism driving telomere maintenance and replicative immortality in cancer cells is telomere elongation by telomerase, and many emerging potential telomere-based therapies have focused on targeting telomerase components. By contrast, recent studies on telomere maintenance mechanism suggest that disrupting telomere stability by interfering with alternative mechanisms of telomere synthesis or protection may also yield new strategies for the treatment of cancer. This review will focus on emerging regulators of telomere synthesis or maintenance, such as G4 telomeric DNA, the CST complex, the t-loop, and shelterins, and discuss their potential as targets for anti-cancer chemotherapeutic intervention in the future. PMID:27123041

  3. Roles of telomeres and telomerase in cancer, and advances in telomerase-targeted therapies.

    PubMed

    Jafri, Mohammad A; Ansari, Shakeel A; Alqahtani, Mohammed H; Shay, Jerry W

    2016-01-01

    Telomeres maintain genomic integrity in normal cells, and their progressive shortening during successive cell divisions induces chromosomal instability. In the large majority of cancer cells, telomere length is maintained by telomerase. Thus, telomere length and telomerase activity are crucial for cancer initiation and the survival of tumors. Several pathways that regulate telomere length have been identified, and genome-scale studies have helped in mapping genes that are involved in telomere length control. Additionally, genomic screening for recurrent human telomerase gene hTERT promoter mutations and mutations in genes involved in the alternative lengthening of telomeres pathway, such as ATRX and DAXX, has elucidated how these genomic changes contribute to the activation of telomere maintenance mechanisms in cancer cells. Attempts have also been made to develop telomere length- and telomerase-based diagnostic tools and anticancer therapeutics. Recent efforts have revealed key aspects of telomerase assembly, intracellular trafficking and recruitment to telomeres for completing DNA synthesis, which may provide novel targets for the development of anticancer agents. Here, we summarize telomere organization and function and its role in oncogenesis. We also highlight genomic mutations that lead to reactivation of telomerase, and mechanisms of telomerase reconstitution and trafficking that shed light on its function in cancer initiation and tumor development. Additionally, recent advances in the clinical development of telomerase inhibitors, as well as potential novel targets, will be summarized. PMID:27323951

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

    PubMed Central

    Mason, Susan M.; Prescott, Jennifer; Tworoger, Shelley S.; DeVivo, Immaculata; Rich-Edwards, Janet W.

    2015-01-01

    Objective Abuse victimization in childhood is associated with a variety of age-related cardiometabolic diseases, but the mechanisms remain unknown. Telomeres, which form the protective caps at the ends of chromosomes, have been proposed as measures of biological age, and a growing body of research suggests that telomere attrition may help to explain relationships between stress and cardiometabolic degradation. We examined the association between childhood abuse victimization and leukocyte telomere length among 1,135 participants in the Nurses’ Health Study II (NHSII). Methods The NHSII ascertained physical and sexual child abuse histories in 2001. Telomere length was measured in genomic DNA extracted from peripheral blood leukocytes collected between 1996 and 1999. The ratio of telomere repeat copy number to a single gene copy number (T/S) was determined by a modified version of the quantitative real-time PCR telomere assay. Telomere length was log-transformed and corrected for assay variation across batch. We regressed telomere length on childhood abuse exposure variables and covariates using linear regression. Results We observed a reduction in telomere length associated with moderate physical abuse versus no physical abuse, but there was no evidence of a dose-response relationship for increased severity of physical abuse. No associations were noted for sexual abuse. Conclusions We found no evidence of an association between severity of childhood physical or sexual abuse and leukocyte telomere length in the NHSII. PMID:26053088

  5. Glyceraldehyde 3-Phosphate Dehydrogenase-Telomere Association Correlates with Redox Status in Trypanosoma cruzi

    PubMed Central

    Pariona-Llanos, Ricardo; Pavani, Raphael Souza; Reis, Marcelo; Noël, Vincent; Silber, Ariel Mariano; Armelin, Hugo Aguirre; Cano, Maria Isabel Nogueira; Elias, Maria Carolina

    2015-01-01

    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. PMID:25775131

  6. On the origin of Robertsonian fusions in nature: evidence of telomere shortening in wild house mice.

    PubMed

    Sánchez-Guillén, R A; Capilla, L; Reig-Viader, R; Martínez-Plana, M; Pardo-Camacho, C; Andrés-Nieto, M; Ventura, J; Ruiz-Herrera, A

    2015-01-01

    The role of telomere shortening to explain the occurrence of Robertsonian (Rb) fusions, as well as the importance of the average telomere length vs. the proportion of short telomeres, especially in nature populations, is largely unexplored. In this study, we have analysed telomere shortening in nine wild house mice from the Barcelona Rb system with diploid numbers ranging from 29 to 40 chromosomes. We also included two standard (2n=40) laboratory mice for comparison. Our data showed that the average telomere length (considering all chromosomal arms) is influenced by both the diploid number and the origin of the mice (wild vs. laboratory). In detail, we detected that wild mice from the Rb Barcelona system (fused and standard) present shorter telomeres than standard laboratory mice. However, only wild mice with Rb fusions showed a high proportion of short telomeres (only in p-arms), thus revealing the importance of telomere shortening in the origin of the Rb fusions in the Barcelona system. Overall, our study confirms that the number of critically short telomeres, and not a simple reduction in the average telomere length, is more likely to lead to the origin of Rb fusions in the Barcelona system and ultimately in nature. PMID:25491286

  7. The role of telomeres and telomerase in hematologic malignancies and hematopoietic stem cell transplantation.

    PubMed

    Wang, Limengmeng; Xiao, Haowen; Zhang, Xing; Wang, Chong; Huang, He

    2014-01-01

    Telomeres are specific nucleoprotein structures at the ends of eukaryotic chromosomes. Telomeres and telomere-associated proteins maintain genome stability by protecting the ends of chromosomes from fusion and degradation. In normal somatic cells, the length of the telomeres gradually becomes shortened with cell division. In tumor cells, the shortening of telomeres length is accelerated under the increased proliferation pressure. However, it will be maintained at an extremely short length as the result of activation of telomerase. Significantly shortened telomeres, activation of telomerase, and altered expression of telomere-associated proteins are common features of various hematologic malignancies and are related with progression or chemotherapy resistance in these diseases. In patients who have received hematopoietic ste