Ten1 functions in telomere end protection and length regulation in association with Stn1 and Cdc13

Grandin, Nathalie

doi:10.1093/emboj/20.5.1173

Cited by 233 publications

(272 citation statements)

References 43 publications

(101 reference statements)

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“…The CDC13-STN1 construct is functional; it suppresses temperature-sensitive growth defect of both cdc13-1 and stn1-13 mutants. The cdc13-1 and stn1-13 strains were obtained from M. Charbonneau (Ecole Normale Superìeure de Lyon, Lyon, France) (Grandin et al, 2001). Epitope tagging of EXO1 and MRE11 was performed by a PCR-based strategy (Knop et al, 1999;Hirano and Sugimoto, 2006).…”

Section: Plasmids and Strainsmentioning

confidence: 99%

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Cdc13 Telomere Capping Decreases Mec1 Association but Does Not Affect Tel1 Association with DNA Ends

Hirano

Sugimoto

2007

MBoC

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Chromosome ends, known as telomeres, have to be distinguished from DNA breaks that activate DNA damage checkpoint. Two large protein kinases, ataxia-teleangiectasia mutated (ATM) and ATM-Rad3-related (ATR), control not only checkpoint activation but also telomere length. In budding yeast, Mec1 and Tel1 correspond to ATR and ATM, respectively. Here, we show that Cdc13-dependent telomere capping attenuates Mec1 association with DNA ends. The telomeric TG repeat sequence inhibits DNA degradation and decreases Mec1 accumulation at the DNA end. The TG-mediated degradation block requires binding of multiple Cdc13 proteins. The Mre11-Rad50-Xrs2 complex and Exo1 contribute to DNA degradation at DNA ends. Although the TG sequence impedes Exo1 association with DNA ends, it allows Mre11 association. Moreover, the TG sequence does not affect Tel1 association with the DNA end. Our results suggest that the Cdc13 telomere cap coordinates Mec1 and Tel1 accumulation rather than simply covering the DNA ends at telomeres. INTRODUCTIONDNA double-strand breaks (DSBs) are induced by exogenous DNA-damaging agents and carcinogens or by endogenous by-products, including reactive oxygen species (Friedberg et al., 2006). The repair of DSBs is crucial for maintaining genome stability. All organisms respond to DSBs by promptly launching the DNA damage response. This response involves the recruitment of DNA repair factors and the activation of signal transduction pathways, often termed DNA damage checkpoint pathways (Zhou and Elledge, 2000). Activation of the checkpoint pathway induces cell cycle arrest and expression of genes required for DNA repair.The checkpoint signals are initiated through two large protein kinases, ataxia-teleangiectasia mutated (ATM) and ATM-Rad3-related (ATR) (Zhou and Elledge, 2000;Abraham, 2001). ATM and ATR are highly conserved among eukaryotes. ATR is closely related to Mec1 in the budding yeast Saccharomyces cerevisiae and Rad3 in the fission yeast Schizosaccharomyces pombe. ATM homologues are termed Tel1 in both budding and fission yeasts. Current evidence indicates that the Mre11-Rad50 -Nbs1 (Xrs2 in budding yeast) complex is the primary sensor that recruits ATR/ Mec1 and ATM/Tel1 to DSBs (Nakada et al., 2003a(Nakada et al., , 2004Falck et al., 2005;You et al., 2005). In budding yeast, there is compelling evidence that the Mre11-Rad50 -Xrs2 (MRX) complex collaborates with exonuclease 1 (Exo1) in the generation of single-stranded DNA (ssDNA) at DSB ends (Krogh and Symington, 2004). ATM/Tel1 interacts with the C terminus of Nbs1/Xrs2 to localize to DNA ends (Nakada et al., 2003a;Falck et al., 2005;You et al., 2005). Meanwhile, the ssDNA that is generated at the DSB is covered with replication protein A (RPA) (Wold, 1997;Krogh and Symington, 2004). RPA-covered DNA recruits ATR/Mec1 to a region near the DSB end (Zou and Elledge, 2003;Nakada et al., 2005). ATM and ATR activate the downstream kinases CHK1 and CHK2 with assistance of checkpoint mediators, including 53BP1, BRCA1, and MDC1 (Zhou and Elledge, 2000;Bakke...

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Section: Plasmids and Strainsmentioning

confidence: 99%

“…One explanation could be that localization of multiple Stn1 proteins to telomeres is important for DNA end protection. Stn1 collaborates with Ten1 in telomere end protection (Grandin et al, 2001). Alternatively, Ten1 might localize to DNA ends that are covered with multiple Cdc13 proteins.…”

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confidence: 99%

Cdc13 Telomere Capping Decreases Mec1 Association but Does Not Affect Tel1 Association with DNA Ends

Hirano

Sugimoto

2007

MBoC

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“…In S. cerevisiae, the trimeric protein complex composed of Cdc13, Stn1, and Ten1 plays a critical role in the protection of chromosome ends from nucleolytic degradation, and the complex serves both positive and negative roles in the access of telomerase to the telomere during late S phase (24,27,66). The Ku70/Ku80 heterodimer, while essential for nonhomologous end joining, also plays a key role both in the recruitment of telomerase to the telomere and in the protection of ends from degradation (9,25,65,74).…”

mentioning

confidence: 99%

Murine Pif1 Interacts with Telomerase and Is Dispensable for Telomere Function In Vivo

Snow

Mateyak

Paderova

et al. 2007

Molecular and Cellular Biology

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Pif1 is a 5 -to-3 DNA helicase critical to DNA replication and telomere length maintenance in the budding yeast Saccharomyces cerevisiae. ScPif1 is a negative regulator of telomeric repeat synthesis by telomerase, and recombinant ScPif1 promotes the dissociation of the telomerase RNA template from telomeric DNA in vitro. In order to dissect the role of mPif1 in mammals, we cloned and disrupted the mPif1 gene. In wild-type animals, mPif1 expression was detected only in embryonic and hematopoietic lineages. mPif1 ؊/؊ mice were viable at expected frequencies, displayed no visible abnormalities, and showed no reproducible alteration in telomere length in two different null backgrounds, even after several generations. Spectral karyotyping of mPif1 ؊/؊ fibroblasts and splenocytes revealed no significant change in chromosomal rearrangements. Furthermore, induction of apoptosis or DNA damage revealed no differences in cell viability compared to what was found for wild-type fibroblasts and splenocytes. Despite a novel association of mPif1 with telomerase, mPif1 did not affect the elongation activity of telomerase in vitro. Thus, in contrast to what occurs with ScPif1, murine telomere homeostasis or genetic stability does not depend on mPif1, perhaps due to fundamental differences in the regulation of telomerase and/or telomere length between mice and yeast or due to genetic redundancy with other DNA helicases.Homeostatic telomere length is achieved by a balance between the extension of the 3Ј telomeric repeats by telomerase or by homologous recombination between telomeric tracts and telomere erosion due to incomplete DNA replication or nucleolytic degradation (30). Telomerase acts to lengthen telomeres via the reverse transcription of an RNA template (encoded by TERC in mammals or TLC1 in Saccharomyces cerevisiae) by a telomerase reverse transcriptase (TERT or Est2, respectively) (30). In the absence of telomerase, telomeric repeats can also be maintained via homologous recombination (12). Excessive telomere lengthening is usually curtailed by cis-inhibitory telomere binding factors, such as Rif1 and Rap1 in S. cerevisiae and TRF1 in humans, or by the action of nucleases (30). In particular instances, telomeric tracts undergo saltatory attrition via the excision of telomeric DNA circles, thus preventing unregulated telomere lengthening (12,40,73).This equilibrium is not simply a push and pull between factors that strictly promote or oppose telomere extension. In S. cerevisiae, the trimeric protein complex composed of Cdc13, Stn1, and Ten1 plays a critical role in the protection of chromosome ends from nucleolytic degradation, and the complex serves both positive and negative roles in the access of telomerase to the telomere during late S phase (24,27,66). The Ku70/Ku80 heterodimer, while essential for nonhomologous end joining, also plays a key role both in the recruitment of telomerase to the telomere and in the protection of ends from degradation (9,25,65,74). Several DNA helicases and nucleases are also known to play ...

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“…The Cdc13p-mediated telosomic complex contains proteins including Stn1p, Ten1p, Est1p, Pol1p, Zds2p, Sir4p and Imp4p [11,12,14,15]. Imp4p was identified from yeast two-hybrid screening experiments using Cdc13p as the bait.…”

Section: Discussionmentioning

confidence: 99%

“…In S. cerevisiae, Rap1p binds to the doublestranded telomeric DNA and Cdc13p binds specifically to the single-stranded portion of the telomeres [7][8][9][10]. These two proteins serve as a core for other proteins to form a multiple protein-DNA complex in telomeres [11][12][13][14][15]. Together they participate in multiple functions on telomeres, such as end protection and replication.…”

Section: Introductionmentioning

confidence: 99%

The U3 small nucleolar ribonucleoprotein component Imp4p is a telomeric DNA-binding protein

Hsieh¹,

Tu²,

Lee³

et al. 2007

Biochemical Journal

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Imp4p is a component of U3 snoRNP (small nucleolar ribonucleoprotein) involved in the maturation of 18S rRNA. We have shown that Imp4p interacts with Cdc13p, a single-stranded telomere-binding protein involved in telomere maintenance. To understand the role of Imp4p in telomeres, we purified recombinant Imp4p protein and tested its binding activity towards telomeric DNA using electrophoretic mobility-shift assays. Our results showed that Imp4p bound specifically to single-stranded telomeric DNA in vitro. The interaction of Imp4p to telomeres in vivo was also demonstrated by chromatin immunoprecipitation experiments. Significantly, the binding of Imp4p to telomeres was not limited to yeast proteins, since the hImp4 (human Imp4) also bound to vertebrate single-stranded telomeric DNA. Thus we conclude that Imp4p is a novel telomeric DNA-binding protein that, in addition to its role in rRNA processing, might participate in telomere function.

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Ten1 functions in telomere end protection and length regulation in association with Stn1 and Cdc13

Cited by 233 publications

References 43 publications

Cdc13 Telomere Capping Decreases Mec1 Association but Does Not Affect Tel1 Association with DNA Ends

Cdc13 Telomere Capping Decreases Mec1 Association but Does Not Affect Tel1 Association with DNA Ends

Murine Pif1 Interacts with Telomerase and Is Dispensable for Telomere Function In Vivo

The U3 small nucleolar ribonucleoprotein component Imp4p is a telomeric DNA-binding protein

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