Deletion ofMEC1suppresses replicative senescence of thecdc13-2mutant inSaccharomyces cerevisiae

In Saccharomyces cerevisiae , telomerase recruitment to telomeres depends on a direct interaction between Cdc13, a protein that binds single-stranded telomeric DNA, and the Est1 subunit of telomerase. The cdc13-2 allele disrupts telomerase association with telomeres, resulting in progressive telomere shortening and replicative senescence. The Mec1/ATR kinase is both a positive and negative regulator of telomerase activity, and is required for the cell cycle arrest in telomerase-deficient senescent cells. In this study, we find that deletion of MEC1 suppresses the replicative senescence of cdc13-2 . This suppression is dependent on telomerase, indicating that Mec1 antagonizes telomerase-mediated telomere extension in cdc13-2 cells to promote senescence.