Assuntos
Mutagênese , Micologia/métodos , Saccharomyces cerevisiae/genética , Antibacterianos/farmacologia , Membrana Celular/metabolismo , Parede Celular/metabolismo , DNA Fúngico/efeitos dos fármacos , DNA Fúngico/genética , DNA Fúngico/efeitos da radiação , DNA Mitocondrial/genética , DNA Mitocondrial/efeitos da radiação , Resistência Microbiana a Medicamentos/genética , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Genes Fúngicos/efeitos dos fármacos , Genes Fúngicos/efeitos da radiação , Mutagênicos/farmacologia , Consumo de Oxigênio/genética , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/efeitos da radiação , TemperaturaRESUMO
A putative tolerance, induced by heat shock (HS), to the lethal and mutagenic effects of 8-methoxypsoralen (8-MOP) photoaddition and hyperthermia was analyzed in Saccharomyces cerevisiae using the wild-type strain N123 and the isogenic DNA repair-deficient mutant pso3-1. In wild-type cells, the HS (38 degrees C for 1 h) did not modify either the survival or the mutation frequency observed after 8-MOP photoaddition, even though it conferred protection against the lethal effect of hyperthermia (50 degrees C). In the pso3-1 mutant, HS induced an increase of the survival, and a decrease of the mutation frequency, after 8-MOP photoaddition and it also protected against the lethal effect of hyperthermia. The responses induced by HS were specific for 8-MOP photoaddition, since they were not observed after 254 nm ultraviolet-light damage. These results indicate that the protection conferred by HS depends of the type of lesion, and operates through the induction of different repair processes. In the pso3-1 mutant, HS could channel the repair intermediates to and error-free repair pathway.
Assuntos
Genes Fúngicos/efeitos dos fármacos , Temperatura Alta , Metoxaleno/farmacologia , Saccharomyces cerevisiae/crescimento & desenvolvimento , Reparo do DNA/genética , Relação Dose-Resposta à Radiação , Genes Fúngicos/efeitos da radiação , Cinética , Mutagênese , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos da radiação , Raios UltravioletaRESUMO
Spontaneous mitotic recombination was examined in the haploid pso4-1 mutant of Saccharomyces cerevisiae and in the corresponding wild-type strain. Using a genetic system involving a duplication of the his4 gene it was shown that the pso4-1 mutation decreases at least fourfold the spontaneous rate of mitotic recombination. The frequency of spontaneous recombination was reduced tenfold in pso4-1 strains, as previously observed in the rad52-1 mutant. However, whereas the rad52-1 mutation specifically reduces gene conversion, the pso4-1 mutation reduces both gene conversion and reciprocal recombination. Induced mitotic recombination was also studied in pso4-1 mutant and wild-type strains after treatment with 8-methoxypsoralen plus UVA and 254 nm UV irradiation. Consistent with previous results, the pso4-1 mutation was found strongly to affect recombination induction.
Assuntos
Conversão Gênica , Genes Fúngicos , Mutação , Recombinação Genética , Saccharomyces cerevisiae/genética , Raios Ultravioleta , DNA Fúngico/genética , Relação Dose-Resposta à Radiação , Genes Fúngicos/efeitos dos fármacos , Genes Fúngicos/efeitos da radiação , Genótipo , Haploidia , Metoxaleno/farmacologia , Mitose/genética , Mapeamento por Restrição , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos da radiaçãoRESUMO
Two different UVA irradiation systems were initially biologically calibrated with two haploid yeast strains proficient and deficient, respectively, in nucleotide excision repair. The number of DNA lesions introduced into the cell's genome by the photoactivated bifunctional furocoumarin 8-MOP was then calculated by means of the applied UVA exposure doses. At LD37 the repair-proficient wild type had about 14 ICL and 34 furan-side monoadducts in its DNA, while doubly blocked repair mutant rad3-12 pso1-1 had 2 ICL and 3 monoadducts. Locus-specific reversion of lys1-1 followed two-hit kinetics in the repair-proficient wild type and one-hit kinetics in an excision-deficient rad2-20 mutant, as would be expected if ICL was the main type of mutagenic lesion in the wild type and monoadducts the main mutagenic lesion type in the excision-deficient strain. Quantitative comparison of 8-MOP + UVA-induced ICL with those induced by bifunctional mustard revealed the former to have a much higher genotoxicity.