title: Yeast MPH1 gene functions in an error-free DNA damage bypass pathway that requires genes from Homologous recombination, but not from postreplicative repair.
abstract: The MPH1 gene from Saccharomyces cerevisiae, encoding a member of the DEAH family of proteins, had been identified by virtue of the spontaneous mutator phenotype of respective deletion mutants. Genetic analysis suggested that MPH1 functions in a previously uncharacterized DNA repair pathway that protects the cells from damage-induced mutations. We have now analyzed genetic interactions of mph1 with a variety of mutants from different repair systems with respect to spontaneous mutation rates and sensitivities to different DNA-damaging agents. The dependence of the mph1 mutator phenotype on REV3 and REV1 and the synergy with mutations in base and nucleotide excision repair suggest an involvement of MPH1 in error-free bypass of lesions. However, although we observed an unexpected partial suppression of the mph1 mutator phenotype by rad5, genetic interactions with other mutations in postreplicative repair imply that MPH1 does not belong to this pathway. Instead, mutations from the homologous recombination pathway were found to be epistatic to mph1 with respect to both spontaneous mutation rates and damage sensitivities. Determination of spontaneous mitotic recombination rates demonstrated that mph1 mutants are not deficient in homologous recombination. On the contrary, in an sgs1 background we found a pronounced hyperrecombination phenotype. Thus, we propose that MPH1 is involved in a branch of homologous recombination that is specifically dedicated to error-free bypass.
authors.affiliation: Department of Molecular Genetics and Preparative Molecular Biology, Institute for Microbiology and Genetics, University of Göttingen, D-37077 Göttingen, Germany.
authors.forename: K Anke
authors.initials: KA
authors.lastname: Schürer
authors.forename: Christian
authors.initials: C
authors.lastname: Rudolph
authors.forename: Helle D
authors.initials: HD
authors.lastname: Ulrich
authors.forename: Wilfried
authors.initials: W
authors.lastname: Kramer
mesh_terms: D015112:4-Nitroquinoline-1-oxide; D003470:Culture Media; D053487:DEAD-box RNA Helicases; D004249:DNA Damage / Q000502:physiology*; D005800:Genes, Fungal / Q000235:genetics; D005838:Genotype; D008741:Methyl Methanesulfonate; D009154:Mutation / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D015363:Quinolones; D020365:RNA Helicases / Q000502:physiology*; D011995:Recombination, Genetic / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*
chemical_list: C120195:4-nitroquinolone-1-oxide; D003470:Culture Media; D015363:Quinolones; D029701:Saccharomyces cerevisiae Proteins; D015112:4-Nitroquinoline-1-oxide; D008741:Methyl Methanesulfonate; C491240:MPH1 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases