BIOLOGICAL CONSEQUENCES OF ESCHERICHIA-COLI RECA PROTEIN EXPRESSION IN THE REPAIR DEFECTIVE PSO4-1 AND RAD51 URA3 MUTANTS OF SACCHAROMYCES-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 af ter treatment of N-methyl-N'-nitro-N-nitrosoguanidine in the pso4-1 an d rad51::URA3 mutants of S. cerevisiae. We tried to find the role of t he RecA protein in S. cerevisiae mutants defective in different repair pathways. The Reck protein had no effect on survival of haploid and d iploid pso4-1 mutants, hut it had a significant effect on MNNG induced mutagenesis, which was increased to the wild type level. No effect of the Reck 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 Reck protein, with its mu ltifunctional enzymatic activity, can bind to special intermediates an d iniciate function of different repair pathways depending on repair d efects of the mutants studied.