Cdk1-Dependent Phosphorylation of Cdc13 Coordinates Telomere Elongation during Cell-Cycle Progression

Abstract

Summary Elongation of telomeres by telomerase replenishes the loss of terminal telomeric DNA repeats during each cell cycle. In budding yeast, Cdc13 plays an essential role in telomere length homeostasis, partly through its interactions with both the telomerase complex and the competing Stn1-Ten1 complex. Previous studies in yeast have shown that telomere elongation by telomerase is cell cycle-dependent, but the mechanism underlying this dependence is unclear. In S. cerevisiae, a single cyclin-dependent kinase Cdk1 (Cdc28) coordinates the serial events required for the cell division cycle, but no Cdk1 substrate has been identified among telomerase and telomere-associated factors. Here we show that Cdk1 dependent phosphorylation of Cdc13 is essential for efficient recruitment of the yeast telomerase complex to telomeres by favoring the interaction of Cdc13 with Est1 rather than the competing Stn1-Ten1 complex. These results provide a direct mechanistic link between coordination of telomere elongation and cell cycle progression in vivo.

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

“…Using mass spectrometry (MS) to analyse phosphorylation sites of overexpressed Cdc13-Myc 9 in S. cerevisiae, we identified new phosphorylation sites S314, S324 and S333 on Cdc13 (Fig. 3a) that have not been well studied previously 22,26,27,42 ( Supplementary Fig. 10).…”

“…1a) [22][23][24][25][26][27] . To examine the possibility that recruitment of telomerase by Cdc13 may be repressed by phosphatases, we determined the phosphorylation level of Cdc13 throughout the cell cycle for wild type (WT) and various phosphatase deletion strains.…”

“…It recruits telomerase to its site of action through an electrostatic interaction between Cdc13 and Est1 (refs 20,21). Some recent studies have suggested that Cdk1, Tel1 and Mec1 may phosphorylate the telomerase recruitment domain of Cdc13 to promote this Cdc13-Est1 interaction at the late S phase [22][23][24][25][26][27] .…”

“…Cdc13 binds Est1 to recruit telomerase [35][36][37] , and recent reports have suggested that the phosphorylations on the telomerase recruitment domain of Cdc13 may promote telomerase recruitment 22,26,27 . However, this proposed signalling has been controversial 38,39 .…”

CDK1 differentially regulates G-overhang generation at leading- and lagging-strand telomeres in telomerase-negative cells in G2phase

“…27 In budding yeast, which contains only one CDK, cdc28, Cdc28 is required for the generation of G-overhangs by controlling end resection [28][29][30] as well as by regulating the recruitment of telomerase to telomeres. 31,32 The role of CDK1 in regulating telomere maintenance in human cells is largely elusive.…”