Analysis of bleomycin‐induced mutagenic functions related to the PSO4 (= XS9) gene of saccharomyces cerevisiae

Abstract

In the present work we analyse some properties of the pso4-1 (= xs9) mutant of the yeast Saccharomyces cerevisiae, which is blocked in both reverse mutation and recombination. We have applied the "apparent survival test" as a method to characterize putative inducible error-prone repair activities related to the PSO4 gene. As the mutagenic agent we have used bleomycin, which is an antitumour radiomimetic antibiotic. Survival, reverse mutation yield, and reverse mutation frequency were determined as a function of bleomycin concentrations (1-60 micrograms/ml) in the logarithmic phase of growth. It is shown that the PSO4 gene product is poorly involved in bleomycin sensitivity and that reverse mutation induced by this mutagen is dramatically reduced in the pso4-1 lys2 mutant strain, as compared with the isogenic SC7K (lys2) strain. M(x) functions exhibit linear-quadratic courses for both the SC7K (lys2) and the pso4-1 lys2 strains. The apparent survival functions display "humps" in both strains, corresponding to the resistant components of the survival functions. These facts suggest that the mutagenicity of bleomycin depends on at least one inducible error-prone repair pathway and that the PSO4 gene product could act as a mutation triggering factor.

Effects of bleomycin on growth kinetics and survival of Saccharomyces cerevisiae: a model of repair pathways

“…This biphasic response could be due to the induction of repair enzymes. Interestingly, in our laboratory it has been recently shown that the resistant component of these curves depends at least in part on BLM-inducible repair (39). Moreover, the RAD6 gene is induced by DNA damage during the log phase of growth (21).…”

“…In different lines of eukaryotic cells, BLM produces inhibition of DNA synthesis (10) as well as cell cycle G2 delay (19,38). With phages, bacteria, and yeast cells, it was demonstrated that this drug is recombinogenic and mutagenic (11,23,39,42). Analysis of BLM-induced mutagenesis in repackaged lambda phage suggests SOS repair dependence (33).…”

“…We have recently shown that BLM induces at least one error-prone type of repair in S. cerevisiae and that the PS04 (XS9) gene acts as a mutation-triggering factor (39). Furthermore, the combination of UV light and BLM produces different degrees of sensitization depending on dose ranges, suggesting overlapping lesion specificity of the involved repair pathways (excision and recombination) (1).…”

Analysis of radioprotection and antimutagenic effects of Ilex paraguariensis infusion and its component rutin

“…Thereafter, the number of revertants lys → LYS were scored ( 12 , 13 ). Mutation frequency M(x,y) and mutation yield Y(x,y) were calculated as: M(x,y) = Nm / Ns; Y(x,y) = Nm / No, where Nm is the number of mutants per mL, No is the number of treated cells per mL, x the absorbed dose, and y the dose of modulators ( 16 , 19 , 20 ).…”

Efecto radioprotector del ácido tánico y vinos de la var Vitis vinífera L. cv Tannat en Saccharomyces cerevisiae.

“…No: número de células tratadas por mL, Nm: número de mutantes por mL, x: dosis absorbida de rayos gamma, y: dosis de los productos naturales (31,35,36) .…”