title: The PSO4 gene is responsible for an error-prone recombinational DNA repair pathway in Saccharomyces cerevisiae.
abstract: The induction of mitotic gene conversion and crossing-over in Saccharomyces cerevisiae diploid cells homozygous for the pso4-1 mutation was examined in comparison to the corresponding wild-type strain. The pso4-1 mutant strain was found to be completely blocked in mitotic recombination induced by photoaddition of mono- and bifunctional psoralen derivatives as well as by mono- (HN1) and bifunctional (HN2) nitrogen mustards or 254 nm UV radiation in both stationary and exponential phases of growth. Concerning the lethal effect, diploids homozygous for the pso4-1 mutation are more sensitive to all agents tested in any growth phase. However, this effect is more pronounced in the G2 phase of the cell cycle. These results imply that the ploidy effect and the resistance of budding cells are under the control of the PSO4 gene. On the other hand, the pso4-1 mutant is mutationally defective for all agents used. Therefore, the pso4-1 mutant has a generalized block in both recombination and mutation ability. This indicates that the PSO4 gene is involved in an error-prone repair pathway which relies on a recombinational mechanism, strongly suggesting an analogy between the pso4-1 mutation and the RecA or LexA mutation of Escherichia coli.
authors.affiliation: Universidade Federal do Rio Grande do Sul, Departamento de Genética, Porto Alegre, Brazil.
authors.forename: H H
authors.initials: HH
authors.lastname: de Andrade
authors.forename: E K
authors.initials: EK
authors.lastname: Marques
authors.forename: A C
authors.initials: AC
authors.lastname: Schenberg
authors.forename: J A
authors.initials: JA
authors.lastname: Henriques
mesh_terms: D003434:Crossing Over, Genetic; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D004171:Diploidy; D011564:Furocoumarins / Q000494:pharmacology; D005785:Gene Conversion; D005800:Genes, Fungal; D006720:Homozygote; D008730:Methoxsalen / Q000494:pharmacology; D008938:Mitosis; D009154:Mutation; D009588:Nitrogen Mustard Compounds / Q000494:pharmacology; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D011564:Furocoumarins; D009588:Nitrogen Mustard Compounds; C017104:3-carbethoxypsoralen; D008730:Methoxsalen