[The xrs2 gene controls recombination repair in yeast]

The XRS2 mutants of Saccharomyces cerevisiae are sensitive to ionizing and UV irradiation, have altered rates of spontaneous and induced mitotic recombination and are defective in meiosis. Haploid xrs2 cells bearing a mutation in RAD51 or RAD52 genes are more sensitive to gamma-rays than respective single mutants. On the other hand, double mutants xrs2-6 and rad50-1 (cdc40-1, radH) have the same radiosensitivity as the single mutants. At the same time, diploid double mutants xrs2-6rad51 (rad52) have no stronger sensitivity than single rad51 or rad52, whilst xrs2-6cdc40-1 mutant is more sensitive than each of the single mutants. These data confirm our previous assumption that XRS2 gene belong to the RAD52 epistatic group. During vegetative growth of xrs2-6 cells the frequency of plasmid-plasmid recombination as well as plasmid and chromosome copies of ADE2 gene are higher than in wt cells, while the efficiency of recombination during transformation is higher in wt cells but not in xrs2-6 cells.