Induction of the cytoplasmic 'petite' mutation in pso mutants of Saccharomyces cerevisiae by photoaddition of furocoumarins or by ultraviolet radiation.
The induction of the cytoplasmic 'petite' mutation (or rho-) after photoaddition of either 8-methoxypsoralen (8-MOP) or 3-carbethoxypsoralen (3-CPs), after 254 nm u.v. and after 6-N-hydroxyaminopurine treatment was examined in three pso mutants in comparison to wild-type Saccharomyces cerevisiae. In three pso mutants which are defective in the induction of nuclear reverse and forward mutations, the photoaddition of 8-MOP enhanced the induction of rho-. This was true for cells in both exponential and stationary phases of growth. After photoaddition of 3-CPs in both growth phases the frequency of rho- was enhanced in pso3-1 whereas pso1-1 showed the same response as the wild-type. In pso2-1 the frequency of rho- was reduced. After treatment with 254 nm u.v. in the stationary phase of growth, rho- induction was increased in pso1-1 and pso3-1 cells as compared to wild-type cells. However, when treated in the exponential phase of growth all three pso mutants showed reduced rho- frequency. The data indicate that the defect in the repair of furocoumarins plus light-induced lesions controlled by nuclear genes (pso) interferes to various extents with the fate of mitochondrial lesions. The frequency of rho- mutants induced in the pso mutants by an analogue of adenine, 6-N-hydroxyaminopurine, was similar to that observed in the wild-type strain, suggesting that this drug may also act at the mitochondrial level as a direct mutagen in yeast.
Da Silva
K V
KV
Departamento de Fisiologia, Farmacologia e Biofísica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil.
Henriques
J A
JA
D004307:Dose-Response Relationship, Radiation; D011564:Furocoumarins / Q000494:pharmacology*; D008027:Light; D008730:Methoxsalen / Q000494:pharmacology*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D013045:Species Specificity; D014466:Ultraviolet Rays
D011564:Furocoumarins; C017104:3-carbethoxypsoralen; D008730:Methoxsalen