title: The pol3-t hyperrecombination phenotype and DNA damage-induced recombination in Saccharomyces cerevisiae is RAD50 dependent.
abstract: The DNA polymerase delta (POL3/CDC2) allele pol3-t of Saccharomyces cerevisiae has previously been shown to be sensitive to methylmethanesulfonate (MMS) and has been proposed to be involved in base excision repair. Our results, however, show that the pol3-t mutation is synergistic for MMS sensitivity with MAG1, a known base excision repair gene, but it is epistatic with rad50Delta, suggesting that POL3 may be involved not only in base excision repair but also in a RAD50 dependent function. We further studied the interaction of pol3-t with rad50Delta by examining their effect on spontaneous, MMS-, UV-, and ionizing radiation-induced intrachromosomal recombination. We found that rad50Delta completely abolishes the elevated spontaneous frequency of intrachromosomal recombination in the pol3-t mutant and significantly decreases UV- and MMS-induced recombination in both POL3 and pol3-t strains. Interestingly, rad50Delta had no effect on gamma-ray-induced recombination in both backgrounds between 0 and 50 Gy. Finally, the deletion of RAD50 had no effect on the elevated frequency of homologous integration conferred by the pol3-t mutation. RAD50 is possibly involved in resolution of replication forks that are stalled by mutagen-induced external DNA damage, or internal DNA damage produced by growing the pol3-t mutant at the restrictive temperature.
authors.affiliation: Laboratory of Gene and Molecular Therapy, Institute of Clinical Physiology, CNR, 56124 Pisa, Italy. alvaro.galli@ifc.cnr.it
authors.forename: Alvaro
authors.initials: A
authors.lastname: Galli
authors.forename: Kurt
authors.initials: K
authors.lastname: Hafer
authors.forename: Tiziana
authors.initials: T
authors.lastname: Cervelli
authors.forename: Robert H
authors.initials: RH
authors.lastname: Schiestl
mesh_terms: D000483:Alleles; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D004258:DNA Polymerase III / Q000235:genetics* / Q000378:metabolism; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004843:Epistasis, Genetic / Q000187:drug effects; D005720:Gamma Rays; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D010641:Phenotype; D011829:Radiation Dosage; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D004268:DNA-Binding Proteins; D009153:Mutagens; C086930:RAD50 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D008741:Methyl Methanesulfonate; D004258:DNA Polymerase III