Accepted_test

Cells use several mechanisms to repair DNA double - strand breaks (DSB): homologous recombination (HR), single-strand annealing (SSA), canonical and alternative pathways of non-homologous end joining (NHEJ). The key event in recombination repair of DNA double strand breaks (DSB) is the formation of the Rad51 nucleoprotein filament. An important role in the regulation of the assembly, stabilization, and disassembly of Rad51 filaments is played by the Rad51 paralogs. Drosophila is a classical multicellular eukaryotic model for studies of DNA damage repair at the organismal level, but our knowledge of the functions of Rad51 paralogs in this organism is lagging behind. Here we show that the rad201^G1 mutation, discovered in 1981 is a Rad51D allele. The rad201^G1 mutants are sensitive to ionizing irradiation and to cisplatin, but not to MMS. A live analysis of the kinetics of radiation - induced DNA damages repair in nuclei of isolated larval brains has shown that it is delayed in Rad51D mutant. In order directly determine which repair pathways affected in Drosophila Rad51D mutant we employed the single DSB DR-white reporter system to quantitate the frequencies of different DSB repair products in the male germline and analyzed the proportion of HR and NHEJ events in somatic cells using NGS sequencing. We have found that Rad51D is required for DSB repair by mechanism of homologous recombination in the germline as well as somatic cells.