Telomerase-Mediated Telomere Addition In Vivo Requires DNA Primase and DNA Polymerases α and δ

Diede, Scott J.; Gottschling, Daniel E.

doi:10.1016/s0092-8674(00)81670-0

Cited by 351 publications

(436 citation statements)

References 80 publications

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“…The CUT and CUT' fragments were elongated if the DNA contained the TG 81 sequence at the end, consistent with the observation that the TG 81 sequence acts as a telomere seed and promotes telomere addition at the DNA end (Diede and Gottschling, 1999). However, detection of the CUT or CUT' fragment became weaker over the course of the experiment if the DNA contained no TG sequence at the end.…”

Section: The 81-base Pair Tg Repeat Inhibits Checkpointsupporting

confidence: 85%

“…DNA samples were collected at various times and examined by Southern blot analysis. DSBs were generated within 1 h after HO expression, as evidenced by the appearance of the cleaved fragments (CUT and CUT') and the disappearance of the intact DNA fragment (PRE).The CUT and CUT' fragments were elongated if the DNA contained the TG 81 sequence at the end, consistent with the observation that the TG 81 sequence acts as a telomere seed and promotes telomere addition at the DNA end (Diede and Gottschling, 1999). However, detection of the CUT or CUT' fragment became weaker over the course of the experiment if the DNA contained no TG sequence at the end.…”

supporting

confidence: 70%

“…The resulting DNA fragment was cloned into HindIII-XhoI-digested pSD155 (Diede and Gottschling, 1999) to generate pTG-HO. To create the pTG-HO-CA plasmid, the 81-base pair TG sequence was first added into the TG-HO cassette by PCR.…”

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: The 81-base Pair Tg Repeat Inhibits Checkpointsupporting

confidence: 85%

supporting

confidence: 70%

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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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“…rfc1-1 cells have elongated telomeres (Adams and Holm 1996), suggesting poor coordination of telomeric C-rich strand synthesis by the lagging strand machinery and G-rich strand synthesis by telomerase in these cells (Diede and Gottschling 1999). To rule out the possibility that hyperelongated telomeres were the cause of the Sphase delay in asf1⌬ rfc1-1 cells, telomere lengths were assayed.…”

Section: Asf1 and Rfc Function Together To Promote S-phase Progressionmentioning

confidence: 99%

Histone deposition protein Asf1 maintains DNA replisome integrity and interacts with replication factor C

Franco¹,

Lam²,

Burgers³

et al. 2005

Genes Dev.

128

125

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Chromatin assembly and DNA replication are temporally coupled, and DNA replication in the absence of histone synthesis causes inviability. Here we demonstrate that chromatin assembly factor Asf1 also affects DNA replication. In budding yeast cells lacking Asf1, the amounts of several DNA replication proteins, including replication factor C (RFC), proliferating cell nuclear antigen (PCNA), and DNA polymerase (Pol ), are reduced at stalled replication forks. In contrast, DNA polymerase ␣ (Pol ␣) accumulates to higher than normal levels at stalled forks in asf1⌬ cells. Using purified, recombinant proteins, we demonstrate that RFC directly binds Asf1 and can recruit Asf1 to DNA molecules in vitro. We conclude that histone chaperone protein Asf1 maintains a subset of replication elongation factors at stalled replication forks and directly interacts with the replication machinery.[Keywords: Chromatin assembly; histone deposition; DNA replication; genome stability] Supplemental material is available at http://www.genesdev.org. In eukaryotes, DNA is assembled into a nucleoprotein complex called chromatin. The fundamental repeating unit of chromatin is the nucleosome, which consists of 146 bp of DNA wrapped around an octamer of core histone proteins, comprised of two H2A/H2B dimers flanking an inner (H3/H4) 2 tetramer. In vivo, histone deposition can occur by DNA replication-coupled or replication-independent mechanisms (for review, see Franco and Kaufman 2004). In either case, histone deposition is mediated by specialized assembly proteins. The best characterized replication-coupled chromatin assembly factor is chromatin assembly factor-1 (CAF-1), an evolutionarily conserved protein complex that binds histone H3 and H4 and delivers them to replicating DNA through an interaction with proliferating cell nuclear antigen (PCNA), the DNA polymerase processivity protein (for review, see Asf1, another evolutionarily conserved histone chaperone, functions during both replication-coupled and replication-independent chromatin assembly. Asf1 bound to histones H3/H4 stimulates histone deposition by CAF-1 in vitro (Tyler et al. 1999;Sharp et al. 2001), and Asf1 physically interacts with the p60/Cac2 subunit of CAF-1 (Tyler et al. 2001;Krawitz et al. 2002;Mello et al. 2002). In yeast, Asf1 and the Hir proteins directly interact and function together to promote heterochromatic gene silencing (Kaufman et al. 1998;Sharp et al. 2001;Sutton et al. 2001;Krawitz et al. 2002). Consistent with a role in multiple deposition pathways, Asf1 copurifies with both CAF-1 and Hir protein complexes in human cell extracts (Tagami et al. 2004).Asf1 also contributes to genome stability during S phase in a manner distinct from both CAF-1 and the Hir proteins. Unlike yeast cells lacking CAF-1 or Hir proteins, cells lacking Asf1 are sensitive to the DNA synthesis inhibitor hydroxyurea (HU) and the DNA topoisomerase I inhibitor camptothecin (CPT), and display synthetic genetic interactions with DNA synthesis genes including the initiation/elongation factor C...

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“…41 In contrast, de novo telomere formation becomes efficient if a tract of 81 telomeric TG [1][2][3] repeats is inserted adjacent to the HO recognition site. 42 These sequences provide a "seed" for subsequent extension of the telomeric end by the telomerase enzyme. Insertion of a small number of TG-rich sequences at 1.6 kb or 10 kb from the HO-induced DSB can also enhance de novo telomere formation, but the frequency of such events remains very low (∼1%).…”

Section: Introductionmentioning

confidence: 99%

Opening the DNA repair toolbox: Localization of DNA double strand breaks to the nuclear periphery

Oza¹,

Peterson²

2010

Cell Cycle

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E fficient repair of DNA double strand breaks is essential for cells to avoid increased mutation rates, genomic instability, and even cell death. Consequently, cells have evolved multiple mechanisms for rapidly repairing these DNA lesions, including error-free homologous recombination as well as error-prone pathways such as nonhomologous end joining. What happens to DSBs that are repaired inefficiently or not at all? Recently, several studies in budding yeast have shown that these more recalcitrant DSBs are localized to the nuclear periphery through interactions between the nuclear envelope protein, Mps3, and proteins associated with DSB chromatin. Why these DSBs are tethered to the nuclear periphery is still not clear, though the current view is that alternative repair pathways may be activated at the periphery in a final attempt to repair the lesion. In this Extra View, we discuss these recent reports, and we show that the Est1 component of the telomerase machinery plays an essential role in anchoring DSB chromatin to the nuclear envelope protein, Mps3.

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Telomerase-Mediated Telomere Addition In Vivo Requires DNA Primase and DNA Polymerases α and δ

Cited by 351 publications

References 80 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

Histone deposition protein Asf1 maintains DNA replisome integrity and interacts with replication factor C

Opening the DNA repair toolbox: Localization of DNA double strand breaks to the nuclear periphery

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