Telomerase subunit overexpression suppresses telomere-specific checkpoint activation in the yeast yku80 mutant.
Ku is a conserved heterodimeric DNA-binding protein that plays critical roles in DNA repair and telomere homeostasis. In Saccharomyces cerevisiae, deletion of YKU70 or YKU80 results in an inability to grow at 37 degrees C. This is suppressed by overexpression of several components of telomerase (EST1, EST2 and TLC1). We show that overexpression of EST2 or TLC1 in yku80 mutants does not restore efficient DNA repair, or restore normal telomere function, as measured by telomere length, single-stranded G-rich strand or transcriptional silencing. Instead, yku80 mutants activate a Rad53p-dependent DNA-damage checkpoint at 37 degrees C and this is suppressed by overexpression of EST2 or TLC1. Indeed, deletion of genes required for Rad53p activation also suppresses the yku80 temperature sensitivity. These results suggest that activation of the DNA-damage checkpoint in yku mutants at 37 degrees C does not result from reduced telomere length per se, but reflects an alteration of the telomere structure that is recognized as damaged DNA.
Wellcome Trust and Cancer Research Campaign, Institute of Cancer and Developmental Biology, University of Cambridge, Cambridge CB2 1QR, UK.
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Jackson
D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004265:DNA Helicases; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D015870:Gene Expression; D005800:Genes, Fungal; D000072200:Ku Autoantigen; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics*; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D012313:RNA; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D019098:Telomerase / Q000737:chemistry / Q000235:genetics*; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D013696:Temperature
D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; C520769:YKU70 protein, S cerevisiae; C520770:YKU80 protein, S cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae; C422952:telomerase RNA; D012313:RNA; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases; C067022:RAD53 protein, S cerevisiae; C099024:EST1 protein, S cerevisiae; C509185:EST2 protein, S cerevisiae; D019098:Telomerase; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen