DNA double-strand breaks (DSBs) occur after exposing cells to ionizing radiation or under the action of various antitumor antibiotics. They can be also generated in the course cell processes, such as meiosis and mating type switching in yeast. The most preferential mechanism for the correction of DNA DSB in yeasts is recombinational repair controlled by RAD52 group genes. The role of recombinational repair in mating type switching of fission yeast cells was examined on the example of genes of this group, rhp51 + and rhp55 +. We constructed homothallic strains of genotypes h 90 rhp51 and h 90 rhp55, and found that mutant cells yielded colonies with the mottled phenotype. In addition, h 90 cells with deletions in these genes were shown to segregate heterothallic iodine-negative colonies h − and h +. The genome region, responsible for the switching process in these segregants, was analyzed by DNA hybridization. As shown in this analysis, h + segregants had the h +N or h 90 configuration of the mat region, whereas h −, the h 90 configuration. Segregants h +N contained DNA duplication in the mat region. DNA rearrangements were not detected at the mating type locus, but the level of DNA DSB formation was drastically decreased in these segregants. Thus, our results show that genes rhp51 + and rhp55 + are involved not only in the repair of induced DNA DSB, but also in the mechanism of mating type switching in fission yeast.
Russian Journal of Genetics – Springer Journals
Published: Apr 19, 2006
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