Further characterization of the role of Pso2 in the repair of DNA interstrand cross-link-associated double-strand breaks in Saccharomyces cerevisiae.

DNA interstrand cross-links (ICL) are thought to be one of the most lethal forms of DNA damage. Therefore, they present a colossal challenge for the DNA damage response and repair pathways. In Saccharomyces cerevisiae, ICL repair utilizes factors from all of the three major repair groups: nucleotide excision repair (RAD3 epistasis group), post-replication repair (RAD6 epistasis group) and recombinational repair (RAD52 epistasis group). Moreover, there are additional factors significantly influencing the repair of ICL in this organism. These have been designated PSO1-10 based on the psoralen sensitive phenotype of the corresponding mutants. Phenotype of the pso2 mutant suggests that Pso2 is not involved in incision step of ICL repair, but it rather functions in some downstream event such as processing of DNA ends created during generation of ICL-associated double-strand breaks (DSB). In order to address the question whether function of Pso2 in the repair of ICL-associated DSB could be mediated through protein-protein interactions, we have conducted a comprehensive two-hybrid screen examining a possibility of interaction of Pso2 with Yku70, Yku80, Nej1, Lif1, Dnl4, Rad50, Mre11, Xrs2, Rad51, Rad52, Rad54, Rad55, Rad57, Rad59 and Rdh54. Here we show that Pso2 associates with none of the above DSB repair proteins, suggesting that this protein very likely does not act in the repair of ICL-associated DSB via crosstalk with DSB repair machinery. Instead, its function in this process seems to be rather individual.