The dds20+ Gene Controls a Novel Rad51Sp-Dependent Pathway of Recombinational Repair in Schizosaccharomyces pombe

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 Rad51 filament formation. As shown in this work, a novel Rad51^Sp-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 rhp55Δ in DNA repair. Cells of dds20Δ 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(Rad51^Sp). 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.__________Translated from Genetika, Vol. 41, No. 6, 2005, pp. 736–745.Original Russian Text Copyright © 2005 by Salakhova, Savchenko, Khasanov, Chepurnaya, Korolev, Bashkirov.