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

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

doi:10.1093/emboj/cdg155

Cited by 55 publications

(73 citation statements)

References 54 publications

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“…This may be similar to the proposed role of TRF2 in mammalian primary cells (29). The existence of a Rap1p-independent counting mechanism has been recently proposed (7).…”

Section: Discussionsupporting

confidence: 80%

The Rap1p-Telomere Complex Does Not Determine the Replicative Capacity of Telomerase-Deficient Yeast

Smolikov

Krauskopf

2003

Molecular and Cellular Biology

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Telomeres are nucleoprotein structures that cap the ends of chromosomes and thereby protect their stability and integrity. In the presence of telomerase, the enzyme that synthesizes telomeric repeats, telomere length is controlled primarily by Rap1p, the budding yeast telomeric DNA binding protein which, through its C-terminal domain, nucleates a protein complex that limits telomere lengthening. In the absence of telomerase, telomeres shorten with every cell division, and eventually, cells enter replicative senescence. We have set out to identify the telomeric property that determines the replicative capacity of telomerase-deficient budding yeast. We show that in cells deficient for both telomerase and homologous recombination, replicative capacity is dependent on telomere length but not on the binding of Rap1p to the telomeric repeats. Strikingly, inhibition of Rap1p binding or truncation of the C-terminal tail of Rap1p in Kluyveromyces lactis and deletion of the Rap1p-recruited complex in Saccharomyces cerevisiae lead to a dramatic increase in replicative capacity. The study of the role of telomere binding proteins and telomere length on replicative capacity in yeast may have significant implications for our understanding of cellular senescence in higher organisms.

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“…This may be similar to the proposed role of TRF2 in mammalian primary cells (29). The existence of a Rap1p-independent counting mechanism has been recently proposed (7).…”

Section: Discussionsupporting

confidence: 80%

The Rap1p-Telomere Complex Does Not Determine the Replicative Capacity of Telomerase-Deficient Yeast

Smolikov

Krauskopf

2003

Molecular and Cellular Biology

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“…Indeed, even telomeres composed entirely of vertebrate-type repeats are kept stable during mitotic growth (18,20,21). Remarkably, on these telomeres, the hallmark telomere binding protein Rap1p appears to be replaced with Tbf1p, and there is some evidence to show that this latter protein can maintain a telomere length regulatory mechanism (19,20). However, it remained unclear how this mechanism could ensure telomere capping and stability in this situation.…”

Section: Discussionmentioning

confidence: 99%

“…Previous results showed that telomeric vertebratetype repeats in yeast are bound by Tbf1p, but no Rap1p or Rif2p associations are detectable (21). Furthermore, the homeostasis of overall telomere length has been proposed to be regulated by a mechanism that somehow accounts for the actual number of Rap1p and, in particular, Rif-proteins present at telomeres (17), but evidence for Rap1p-independent telomere length control mechanisms exists (20). The near-WT length of mixed ScVSctelomeres that contain about 50% fewer yeast repeats than an average WT Sc-telomere suggests that Rap1p binding at the subtelomere-telomere transition and at the distal-most repeats is crucial for allowing normal telomere homeostasis.…”

Section: Discussionmentioning

confidence: 99%

Telomerase Is Required to Protect Chromosomes with Vertebrate-type T2AG3 3′ Ends in Saccharomyces cerevisiae

Bah

Gilson

Wellinger

2011

Journal of Biological Chemistry

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Telomeres containing vertebrate-type DNA repeats can be stably maintained in Saccharomyces cerevisiae cells. We show here that telomerase is required for growth of yeast cells containing these vertebrate-type telomeres. When present at the chromosome termini, these heterologous repeats elicit a DNA damage response and a certain deprotection of telomeres. The data also show that these phenotypes are due only to the terminal localization of the vertebrate repeats because if they are sandwiched between native yeast repeats, no phenotype is observed. Indeed and quite surprisingly, in this latter situation, telomeres are of virtually normal lengths, despite the presence of up to 50% of heterologous repeats. Furthermore, the presence of the distal vertebrate-type repeats can cause increased problems of the replication fork. These results show that in budding yeast the integrity of the 3 overhang is required for proper termination of telomere replication as well as protection.Specialized ribonucleoprotein complexes known as telomeres protect the natural ends of eukaryotic chromosomes. In the budding yeast Saccharomyces cerevisiae, telomeres are composed of an ϳ300-bp double-stranded (ds) 4 tract of irregular repeats, abbreviated TG 1-3 /C 1-3 A, and terminate with a 12-to 14-nt single-stranded (ss) 3Ј overhang made of the TG 1-3 motifs (1-3). In contrast, vertebrate telomeres contain a ds tract containing thousands of T 2 AG 3 /C 3 TA 2 repeats and terminate with a ss 3Ј overhang made of T 2 AG 3 motifs (2, 4, 5).The complete replication of linear eukaryotic chromosomes requires the de novo addition of telomeric repeats to chromosome ends by telomerase, a specialized reverse transcriptase (for reviews, see Refs. 6 -9). The core telomerase components are a reverse-transcriptase catalytic subunit and a RNA moiety. In yeast, these components are known as Est2p and TLC1, respectively (8). The telomerase RNA always contains a short region that is complementary to the G-rich strand of telomeric repeats, and that region is used as a template for repeat addition (7, 9).Telomerase invalidation leads to gradual telomere shortening and ultimately causes cells to stop dividing (7, 9, 10). Nevertheless, cellular backup mechanisms can maintain telomeres in the absence of telomerase and ultimately preserve genome integrity. In this mode of telomere maintenance, which is known as alternative lengthening of telomeres in human cells, and survivor mode in Saccharomyces cerevisiae, telomeric DNA is maintained via homologous recombination-based mechanisms (11,12).By differentiating chromosomal ends from internal ds breaks, telomeres also prevent chromosomal ends from eliciting DNA damage checkpoint activation and protect telomeres from inappropriate DNA repair activity. Binding of the multiprotein complex shelterin is essential for both protecting and maintaining the length of mammalian telomeres (13,14). Rap1p, one of the several proteins associated with similar functions at budding yeast telomeres, binds directly to ds telomeric repeats ...

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“…6C). Previous studies have shown that deletion of either TEL1 (the yeast ATM homolog) or the MRX complex genes RAD50 and MRE11 causes severe telomere shortening (Greenwell et al 1995;Boulton and Jackson 1998), and at least in the case of tel1⌬ a loss of Rap1 counting (Ray and Runge 1999a;Brevet et al 2003). Both Tel1 and MRX are thus thought to be positive regulators of telomerase action, and epistasis analysis would suggest that they act downstream from both RIF1 and RIF2 (Ray and Runge 1999a;Ritchie et al 1999;Ritchie and Petes 2000;Chan et al 2001;Diede and Gottschling 2001;Tsukamoto et al 2001).…”

Section: Telomere Elongation In Pol12-216 Mutants Requires Telomerasementioning

confidence: 99%

Pol12, the B subunit of DNA polymerase α, functions in both telomere capping and length regulation

Grossi¹,

Puglisi²,

Dmitriev³

et al. 2004

Genes Dev.

127

173

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The regulation of telomerase action, and its coordination with conventional DNA replication and chromosome end "capping," are still poorly understood. Here we describe a genetic screen in yeast for mutants with relaxed telomere length regulation, and the identification of Pol12, the B subunit of the DNA polymerase ␣ (Pol1)-primase complex, as a new factor involved in this process. Unlike many POL1 and POL12 mutations, which also cause telomere elongation, the pol12-216 mutation described here does not lead to either reduced Pol1 function, increased telomeric single-stranded DNA, or a reduction in telomeric gene silencing. Instead, and again unlike mutations affecting POL1, pol12-216 is lethal in combination with a mutation in the telomere end-binding and capping protein Stn1. Significantly, Pol12 and Stn1 interact in both two-hybrid and biochemical assays, and their synthetic-lethal interaction appears to be caused, at least in part, by a loss of telomere capping. These data reveal a novel function for Pol12 and a new connection between DNA polymerase ␣ and Stn1. We propose that Pol12, together with Stn1, plays a key role in linking telomerase action with the completion of lagging strand synthesis, and in a regulatory step required for telomere capping.

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

Cited by 55 publications

References 54 publications

The Rap1p-Telomere Complex Does Not Determine the Replicative Capacity of Telomerase-Deficient Yeast

The Rap1p-Telomere Complex Does Not Determine the Replicative Capacity of Telomerase-Deficient Yeast

Telomerase Is Required to Protect Chromosomes with Vertebrate-type T2AG3 3′ Ends in Saccharomyces cerevisiae

Pol12, the B subunit of DNA polymerase α, functions in both telomere capping and length regulation

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