Regulation of the ligation step of non-homologous end-joining

Project leader: Miroslav Chovanec
Project duration: 2014 - 2017

As DNA double-strand breaks (DSB) are the most toxic DNA lesion, their repair is essential to maintain genome stability and cell viability. Non-homologous end-joining (NHEJ) is one of the two main pathways that have evolved to repair DSB. Central to NHEJ is the DNA ligase IV complex, which catalyzes the ligation step of the process and involves the Lif1 protein in yeast. We have revealed the SUMOylation of Lif1 and identified lysine 301 as the major conjugation site. We suggest that Lif1 SUMOylation represents a new regulatory mechanism that regulates NHEJ. Moreover, Lif1 undergoes cyclin-dependent kinase-dependent phosphorylation at serine 261 and this modification also controls NHEJ. Thus, Lif1 undergoes both SUMOylation and phosphorylation, the two modifications that regulate NHEJ. Here, we intent to verify a possibility of cross-talk between Lif1 SUMOylation and phosphorylation during the regulation of NHEJ using the Lif1 substituted alleles and various biochemical and genetic methods.