Abstract
Repair of DNA double-strand break (DSB) is an evolutionary conserved Rad51-mediated mechanism. In yeasts, Rad51 paralogs, Saccharomyces cerevisiae Rad55-Rad57 and Schizosaccharomyces pombe Rhp55-Rhp57 are mediators of the nucleoprotein RadS1 filament formation. As shown in this work, a novel RAD51Sp-dependent pathway of DSB repair acts in S. pombe parallel to the pathway mediated by Rad51 paralogs. A new gene dds20+ that controls this pathway was identified. The overexpression of dds20+ partially suppresses defects of mutant rhp55delta in DNA repair. Cells of dds20delta manifest hypersensitivity to a variety of genotoxins. Epistatic analysis revealed that dds20+ is a gene of the recombinational repair group. The role of Dds20 in repair of spontaneous damages occurring in the process of replication and mating-type switching remains unclear. The results obtained suggest that Dds20 has functions beyond the mitotic S phase. The Dds20 protein physically interacts with Rhp51 (Rad51Sp). Dds20 is assumed to operate at early recombinational stages and to play a specific role in the Rad51 protein filament assembly differing from that of Rad51 paralogs.
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