Biological consequences of E.coli RecA protein expression in the repair defective pso4-1 and rad51::URA3 mutants of S. cerevisiae after treatment with N-methyl-N'-nitro-N-nitrosoguanidine.

RecA protein of E.coli is a multifunctional protein participating in genetic recombination, recombinational repair and mutagenesis. We used E.coli recA gene as a probe for complementation of repair defects after treatment of N-methyl-N'-nitro-N-nitrosoguanidine in the pso4-1 and rad51::URA3 mutants of S. cerevisiae. We tried to find the role of the RecA protein in S. cerevisiae mutants defective in different repair pathways. The RecA protein had no effect on survival of haploid and diploid pso4-1 mutants, but it had a significant effect on MNNG induced mutagenesis, which was increased to the wild type level. No effect of the RecA protein on survival was observed in rad51::URA3 mutant after MNNG treatment. However, in this case the RecA protein decreased the induced mutagenesis. We can suppose that the RecA protein, with its multifunctional enzymatic activity, can bind to special intermediates and initiate function of different repair pathways depending on repair defects of the mutants studied.