PP2A and Aurora differentially modify Cdc13 to promote telomerase release from telomeres at G2/M phase

Shen, Zih-Jie; Hsu, Pang-Hung; Su, Yu-Tai; Yang, Cheng‐Ta; Kao, Li Ting; Tseng, Shun‐Fu; Tsai, Ming‐Daw; Teng, Shu-Chun

doi:10.1038/ncomms6312

Cited by 25 publications

(26 citation statements)

References 70 publications

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“…Even though the function of protein kinases in telomere biology has been widely studied, the role of phosphatases remains mostly unexplored. Contrary to this trend, budding yeast Pph22 phosphatase was recently shown to regulate the phosphorylation of Cdc13 in a cell cycle-dependent manner (Shen et al, 2014). The dephosphorylation of specific Cdc13 residues by Pph22 reverses the interaction of Cdc13 with Est1 and, consequently, disengages telomerase from telomeres (Shen et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

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Ssu72 phosphatase is a conserved telomere replication terminator

et al. 2019

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Telomeres, the protective ends of eukaryotic chromosomes, are replicated through concerted actions of conventional DNA polymerases and elongated by telomerase, but the regulation of this process is not fully understood. Telomere replication requires (Ctc1/Cdc13)‐Stn1‐Ten1, a telomeric ssDNA‐binding complex homologous to RPA. Here, we show that the evolutionarily conserved phosphatase Ssu72 is responsible for terminating the cycle of telomere replication in fission yeast. Ssu72 controls the recruitment of Stn1 to telomeres by regulating Stn1 phosphorylation at Ser74, a residue located within its conserved OB‐fold domain. Consequently, ssu72∆ mutants are defective in telomere replication and exhibit long 3′‐ssDNA overhangs, indicative of defective lagging‐strand DNA synthesis. We also show that hSSU72 regulates telomerase activation in human cells by controlling recruitment of hSTN1 to telomeres. These results reveal a previously unknown yet conserved role for the phosphatase SSU72, whereby this enzyme controls telomere homeostasis by activating lagging‐strand DNA synthesis, thus terminating the cycle of telomere replication.

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Section: Discussionmentioning

confidence: 99%

“…Contrary to this trend, budding yeast Pph22 phosphatase was recently shown to regulate the phosphorylation of Cdc13 in a cell cycle-dependent manner (Shen et al, 2014). Even though the function of protein kinases in telomere biology has been widely studied, the role of phosphatases remains mostly unexplored.…”

Section: Discussionmentioning

confidence: 99%

Ssu72 phosphatase is a conserved telomere replication terminator

et al. 2019

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“…Even though the function of protein kinases in telomere biology has been widely studied, the role of phosphatases remains relatively less explored. Contrary to this trend, budding yeast Pph22 phosphatase was recently shown to regulate the phosphorylation of Cdc13 in a cell cycle-dependent manner 46 . The dephosphorylation of specific Cdc13 residues by Pph22 reverses the interaction of Cdc13 with Est1 and, consequently, disengages telomerase from telomeres 46 .…”

Section: Discussionmentioning

confidence: 96%

“…Contrary to this trend, budding yeast Pph22 phosphatase was recently shown to regulate the phosphorylation of Cdc13 in a cell cycle-dependent manner 46 . The dephosphorylation of specific Cdc13 residues by Pph22 reverses the interaction of Cdc13 with Est1 and, consequently, disengages telomerase from telomeres 46 . However, to date, there are no known phosphatases that regulate telomere length in fission yeast or higher eukaryotes.…”

Section: Discussionmentioning

confidence: 96%

SSU72 phosphatase is a telomere replication terminator

Escandell

Carvalho

Gallo-Fernández

et al. 2018

Preprint

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14Telomeres, the protective ends of eukaryotic chromosomes, are replicated through 15 concerted actions by conventional DNA polymerases and telomerase, though the 16 regulation of this process is not fully understood. Telomere replication requires (C)-17 Stn1-Ten1, a telomere ssDNA-binding complex that is homologous to RPA. Here, we 18 show that the evolutionarily conserved phosphatase Ssu72 is responsible for 19 terminating the cycle of telomere replication in fission yeast. Ssu72 controls the 20 recruitment of Stn1 to telomeres by regulating Stn1 phosphorylation at S74, a 21 residue that lies within the conserved OB fold domain. Consequently, ssu72∆ 22 mutants are defective in telomere replication and exhibit long 3' overhangs, which 23 are indicative of defective lagging strand DNA synthesis. We also show that hSSU72 24 regulates telomerase activation in human cells by controlling the recruitment of 25 hSTN1 to telomeres. Thus, in this study, we demonstrate a previously unknown yet 26 conserved role for the phosphatase SSU72, whereby this enzyme controls telomere 27 homeostasis by activating lagging strand DNA synthesis, thus terminating the cycle 28 of telomere replication. 29 Keywords: Fission yeast; Telomere; CST; SSU72; lagging strand synthesis 30 93 phosphorylation, thus reducing telomeric ssDNA and inhibiting telomerase 94 recruitment. 95 96 6 Results 97Ssu72 is a negative regulator of telomere elongation 98 We carried out a genome-wide screen for regulators of telomere homeostasis 99 in S. pombe using a commercially available whole-genome deletion library (Bioneer 100 corporation). This library allowed us to identify new non-essential genes involved in 101 telomere homeostasis in fission yeast (Figure 1A). Of the genes identified from the 102 screen, we selected the highly conserved phosphatase ssu72+ (SPAC3G9.04) as 103 the most promising candidate for further characterization. We generated a deletion 104 mutant (ssu72∆) as well as a point mutant devoid of phosphatase activity (ssu72-105 C13S) and found that these two mutants possess longer telomeres ( Figure 1B). 106 Additionally, we found that Ssu72 localized to telomeres in a cell cycle-dependent 107 manner. We performed cell cycle synchronization using a cdc25-22 block-release 108 method in a ssu72-myc tagged strain and measured Ssu72 binding to telomeres by 109 chromatin immunoprecipitation (ChIP). Cell cycle phases and synchronization 110 efficiency were measured using the cell septation index. Ssu72-myc is recruited to 111 telomeres in late S phase and declines later in the cell cycle ( Figure 1C). 112 Interestingly, Ssu72 is recruited to telomeres at approximately the same time as the 113 arrival of the lagging strand machinery at chromosome ends 17 . 114 ssu72∆ cells displayed increased (~1 Kb) telomere lengths compared to wild-115 type telomeres (~300 bp) ( Figure 1B). We set out to understand the nature of 116 telomere elongation in the ssu72 mutant background. To test if the telomere 117 elongation was dependent on telomerase...

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“…Certain evidence suggests that Cdc13 is phosphorylated by the Tel1/Mec1 checkpoint kinases to promote the Cdc13-Est1 interaction [82,83] (Figure 3C). Indeed, in vitro, Tel1 phosphorylates Cdc13 at the positions 225, 249 and 255 [82].…”

Section: Cdc13-est1 As the Major Telomerase Recruitment Pathway In Lamentioning

confidence: 99%

Telomerase in Space and Time: Regulation of Yeast Telomerase Function at Telomeres and DNA Breaks

Vasianovich¹,

Krallis²,

Wellinger³

2020

Telomerase and Non-Telomerase Mechanisms of Telomere Maintenance

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A development of new strategies against telomerase-associated disorders, such as dyskeratosis congenita, aplastic anemia or cancer, relies on a detailed understanding of telomerase life cycle and the multiple layers of its regulation. Saccharomyces cerevisiae is a prime model to study telomerase function and it has already revealed many conserved pathways for telomerase biology. In this chapter, we review the current knowledge of the regulatory pathways that control telomerase function in budding yeast. In particular, we discuss the cell cycle-dependent assembly of telomerase and its recruitment to telomeres. We also focus on the mechanisms that target telomerase to short telomeres. Finally, we discuss possible pathways that inhibit telomerase function at DNA double-strand breaks, thus limiting deleterious de novo telomere addition events.

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PP2A and Aurora differentially modify Cdc13 to promote telomerase release from telomeres at G2/M phase

Cited by 25 publications

References 70 publications

Ssu72 phosphatase is a conserved telomere replication terminator

Ssu72 phosphatase is a conserved telomere replication terminator

SSU72 phosphatase is a telomere replication terminator

Telomerase in Space and Time: Regulation of Yeast Telomerase Function at Telomeres and DNA Breaks

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