Regulation of DNA double-strand break repair mechanism choice

Project leader: Miroslav Chovanec
Project duration: 2011 - 2014

Double-strand breaks (DSB) are considered to be one of the most toxic DNA lesions. If left unrepaired and misrepaired, they pose a threat to genome stability and cell viability. Two main mechanisms, homologous recombination (HR) and non-homologous end-joining (NHEJ), have evolved in cells to repair DSB. In yeast, single-strand annealing (SSA) is one of the HR subpathways. Recently, we discovered mechanism, dependent on Nej1-Srs2 interaction, which mediates cross-talk between HR and NHEJ, promoting NHEJ/SSA-like repair. We showed that Srs2 was recruited to DSB in Nej1-dependent manner. Both Srs2 and Nej1 were required for repair of DSB by mechanism reminiscent of SSA. As the absence of Rad51 suppressed the SSA-defect in srs2/nej1 cells, we suggested that Nej1 recruits Srs2 to DSB to promote NHEJ/SSA-like repair by dismantling inappropriately formed Rad51 filaments. Here, we plan to characterize the Nej1-Srs2 complex in more detail. Our previous experiments revealed Srs2-interacting region in Nej1, thereby we intend to map Nej1-interacting region in Srs2. As we found Lif1 also interacting with Srs2, mapping of interacting domains within Lif1-Srs2 complex will also be performed. We also aim to address the questions whether Nej1 interacts with Srs2 in the absence of Lif1 and vice versa and whether Nej1-Lif1 interaction per se is needed for the Nej1-Srs2 and Lif1-Srs2 complexes assembly. We will also clarify a fact that Lif1 interacting region in Srs2 overlaps with that of Rad51.