Contribution of homologous recombination and non-homologous end-joining to DNA double-strand break repair after oxidative stress in the budding yeast Saccharomyces cerevisiae

Project leader: Miroslav Chovanec
Project duration: 2006 - 2008

DNA damage induced by oxidative stress includes a number of structural alterations in DNA such as base and sugar damage, apurinic/apyrimidinic sites, DNA-protein cross-links and DNA single- and double-strand breaks (DSB), with DSB being the most deleterious type of DNA damage due to disrupting both DNA strands. Since DSB can affect genomic stability and cell viability, efficient DSB repair pathways have evolved throughout evolution in all living cells. These are comprised of homologous recombination (HR) and non-homologous end-joining (NHEJ). We intent to investigate induction and repair of DSB induced by four oxidizing agents, hydrogen peroxide (H2O2), menadione (MD), bleomycin (BLM) and sodium selenite (SS), in the budding yeast Saccharomyces cerevisiae. Moreover, DSB induction and repair will optionally be examined after treatment by low, non-toxic concentration(s) of SS followed by exposure to H2O2, BLM or MD, as it has been shown that low concentration(s) of the selenium-containg compounds may have an antioxidative activity. The main emphasis will be put on the relative contribution of HR and NHEJ to this process, which will be evaluated using appropriate mutants, the rad52 (HR-defective) and yku70 (NHEJ-defective) single mutants and the rad52 yku70 (both HR- and NHEJ-defective) double mutant. Since our preliminary survival data show a significant difference in sensitivity to mentioned oxidizing agents among these mutants, we are interested in addressing the question whether survival data may correlate with DSB induction in, and/or repair capacity of, the mutant strains used. Particular goal of the present project is to define contribution of HR and NHEJ to repair of DSB generated by each oxidizing agent.

Publications