title: Abrogation of the Chk1-Pds1 checkpoint leads to tolerance of persistent single-strand breaks in Saccharomyces cerevisiae.
abstract: In budding yeast, Apn1, Apn2, Tpp1, and Rad1/Rad10 are important enzymes in the removal of spontaneous DNA lesions. apn1 apn2 rad1 yeast are inviable due to accumulation of abasic sites and strand breaks with 3' blocking lesions. We found that tpp1 apn1 rad1 yeast exhibited slow growth but frequently gave rise to spontaneous slow growth suppressors that segregated as single-gene mutations. Using a candidate gene approach, we identified several tpp1 apn1 rad1 suppressors. Deleting uracil glycosylase suppressed both tpp1 apn1 rad1 and apn1 apn2 rad1 growth defects by reducing the abasic site burden. Mutants affecting the Chk1-Pds1 metaphase-anaphase checkpoint only suppressed tpp1 apn1 rad1 slow growth. In contrast, most S-phase checkpoint mutants were synthetically lethal in a tpp1 apn1 rad1 background. Epistasis analyses showed an additive effect between chk1 and ung1, indicating different mechanisms of suppression. Loss of Chk1 partially restored cell-growth parameters in tpp1 apn1 rad1 yeast, but at the same time exacerbated chromosome instability. We propose a model in which recombinational repair during S phase coupled with failure of the metaphase-anaphase checkpoint allows for tolerance of persistent single-strand breaks at the expense of genome stability.
authors.affiliation: Department of Pathology, University of Michigan Medical School, Ann Arbor, 48109-0602, USA.
authors.forename: Anandi S
authors.initials: AS
authors.lastname: Karumbati
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wilson
mesh_terms: D000705:Anaphase; D018797:Cell Cycle Proteins / Q000235:genetics*; D002455:Cell Division; D049109:Cell Proliferation; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics*; D004260:DNA Repair; D045643:DNA Repair Enzymes; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D004843:Epistasis, Genetic; D005434:Flow Cytometry; D016195:G2 Phase; D017353:Gene Deletion; D016681:Genome, Fungal; D005838:Genotype; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics*; D009708:Nucleotidases / Q000378:metabolism; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics*; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D064249:Securin; D051981:Uracil-DNA Glycosidase
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C578004:PDS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D064249:Securin; D011494:Protein Kinases; D000071877:Checkpoint Kinase 1; D004720:Endonucleases; C069266:RAD1 protein, S cerevisiae; D009708:Nucleotidases; C039170:deoxynucleotide 3'-phosphatase; D045647:DNA Glycosylases; D051981:Uracil-DNA Glycosidase; C468953:APN2 protein, S cerevisiae; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D045643:DNA Repair Enzymes