Delineation of New Mechanisms Of DNA Double Strand Break Repair

DNA damage is frequently induced in cells by both endogenous and exogenous agents. DNA damage, particular double strand breaks (DSBs) may lead to genomic instability, and the progression of cancer, aging, neurodegeneration, and other human diseases. The cell employs two major DSB repair pathways, including homologous recombination (HR) and Non-homologous end joining (NHEJ), but the detailed mechanisms of DSB repair remain to be further revealed. In the first part of this study, we characterized a plasmid-based assay to investigate NHEJ repair in Xenopus egg extracts. Our data argued for a preference for the precise repair by the NHEJ machinery and also highlighted the variable nature of end processing that is rigorously in line with the structure of DSB ends. In the second part of this study, we identified that several phosphatase subunits, including protein phosphatase 1 (PP1) and phosphatase 1 nuclear targeting subunit (PNUTS), were associated with DSBs in vitro and in vivo. Especially, we concluded that PNUTS and PP1 fine-tune the dynamic phosphorylation of DNA-PKcs to mediate NHEJ after DNA damage. In the third part of the study, we characterized a new kinesin member, Kif2c, as a new factor involved in DSB repair. Furthermore, our results indicated that Kif2c facilitated DSB mobility and modulates DSB dynamics. Collectively, these studies utilized comprehensive experimental approaches to identify and characterize new factors and mechanisms involved in DSB repair