title: The post-replication repair RAD18 and RAD6 genes are involved in the prevention of spontaneous mutations caused by 7,8-dihydro-8-oxoguanine in Saccharomyces cerevisiae.
abstract: 7,8-dihydro-8-oxoguanine (8-oxoG) is an abundant and mutagenic lesion produced in DNA exposed to free radicals and reactive oxygen species. In Saccharomyces cerevisiae, the OGG1 gene encodes the 8-oxoG DNA N-glycosylase/AP lyase (Ogg1), which is the functional homologue of the bacterial Fpg. Ogg1-deficient strains are spontaneous mutators that accumulate GC to TA transversions due to unrepaired 8-oxoG in DNA. In yeast, DNA mismatch repair (MMR) and translesion synthesis (TLS) by DNA polymerase eta also play a role in the prevention of the mutagenic effect of 8-oxoG. In the present study, we show the RAD18 and RAD6 genes that are required to initiate post-replication repair (PRR) are also involved in the prevention of mutations by 8-oxoG. Consistently, a synergistic increase in spontaneous CanR and Lys+ mutation rates is observed in the absence of Rad6 or Rad18 proteins in ogg1 mutant strains. Spectra of CaR mutations in ogg1 rad18 and ogg1 rad6 double mutants show a strong bias in the favor of GC to TA transversions, which are 137- and 189-fold higher than in the wild-type, respectively. The results also show that Poleta (RAD30 gene product) plays a critical role on the prevention of mutations at 8-oxoG, whereas Polzeta (REV3 gene product) does not. Our current model suggests that the Rad6-Rad18 complex targets Poleta at DNA gaps that result from the MMR-mediated excision of adenine mispaired with 8-oxoG, allowing error-free dCMP incorporation opposite to this lesion.
authors.affiliation: CEA, Département de Radiobiologie et Radiopathologie, UMR217 CNRS Radiobiologie Moléculaire et Cellulaire, BP6, 92265-Fontenay aux Roses, France.
authors.forename: Marcelo
authors.initials: M
authors.lastname: de Padula
authors.forename: Guenaelle
authors.initials: G
authors.lastname: Slezak
authors.forename: Patricia
authors.initials: P
authors.lastname: Auffret van Der Kemp
authors.forename: Serge
authors.initials: S
authors.lastname: Boiteux
mesh_terms: D020137:Base Pair Mismatch; D045647:DNA Glycosylases / Q000235:genetics; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004259:DNA-Directed DNA Polymerase / Q000502:physiology; D005800:Genes, Fungal; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000502:physiology*; D000099270:Y-Family DNA Polymerases
chemical_list: D045647:DNA Glycosylases; D004268:DNA-Binding Proteins; D004259:DNA-Directed DNA Polymerase; D006147:Guanine; D029701:Saccharomyces cerevisiae Proteins; D044763:Ubiquitin-Conjugating Enzymes; C453560:7,8-dihydro-8-oxoguanine; C063607:RAD18 protein, S cerevisiae; C471606:RAD6 protein, S cerevisiae; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases