Mouse DNA polymerase kappa has a functional role in the repair of DNA strand breaks

• Polκ accumulates at laser-induced sites of damage via its C-terminus.
• The MSH2- and Rad18-dependent monoubiquitinated PCNA is required for efficient Polκ accumulation.
• Polκ-deficient MEFs are sensitive to H2O2 treatment and have a defect in single-strand break repair and double strand break repair.

The Y-family of DNA polymerases support of translesion DNA synthesis (TLS) associated with stalled DNA replication by DNA damage. Recently, a number of studies suggest that some specialized TLS polymerases also support other aspects of DNA metabolism beyond TLS in vivo. Here we show that mouse polymerase kappa (Polκ) could accumulate at laser-induced sites of damage in vivo resembling polymerases eta and iota. The recruitment was mediated through Polκ C-terminus which contains the PCNA-interacting peptide, ubiquitin zinc finger motif 2 and nuclear localization signal. Interestingly, this recruitment was significantly reduced in MSH2-deficient LoVo cells and Rad18-depleted cells. We further observed that Polκ-deficient mouse embryo fibroblasts were abnormally sensitive to H2O2 treatment and displayed defects in both single-strand break repair and double-strand break repair. We speculate that Polκ may have an important role in strand break repair following oxidative stress in vivo.