title: Recruitment of Rad51 and Rad52 to short telomeres triggers a Mec1-mediated hypersensitivity to double-stranded DNA breaks in senescent budding yeast.
abstract: Telomere maintenance is required for chromosome stability, and telomeres are typically replicated by the action of telomerase. In both mammalian tumor and yeast cells that lack telomerase, telomeres are maintained by an alternative recombination mechanism. Here we demonstrated that the budding yeast Saccharomyces cerevisiae type I survivors derived from telomerase-deficient cells were hypersensitive to DNA damaging agents. Assays to track telomere lengths and drug sensitivity of telomerase-deficient cells from spore colonies to survivors suggested a correlation between telomere shortening and bleomycin sensitivity. Our genetic studies demonstrated that this sensitivity depends on Mec1, which signals checkpoint activation, leading to prolonged cell-cycle arrest in senescent budding yeasts. Moreover, we also observed that when cells equipped with short telomeres, recruitments of homologous recombination proteins, Rad51 and Rad52, were reduced at an HO-endonuclease-catalyzed double-strand break (DSB), while their associations were increased at chromosome ends. These results suggested that the sensitive phenotype may be attributed to the sequestration of repair proteins to compromised telomeres, thus limiting the repair capacity at bona fide DSB sites.
authors.affiliation: Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Lin
authors.forename: Chia-Ching
authors.initials: CC
authors.lastname: Chang
authors.forename: Chui-Wei
authors.initials: CW
authors.lastname: Wong
authors.forename: Shu-Chun
authors.initials: SC
authors.lastname: Teng
mesh_terms: D001761:Bleomycin / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D004720:Endonucleases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005816:Genetic Complementation Test; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051135:Rad51 Recombinase / Q000378:metabolism*; D051721:Rad52 DNA Repair and Recombination Protein / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000201:enzymology*; D013997:Time Factors
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C497197:RAD52 protein, S cerevisiae; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; D001761:Bleomycin; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D019098:Telomerase; D004720:Endonucleases