Corrects defective DNA strand-break repair and sister chromatid exchange following treatment with ionizing radiation and alkylating agents (By similarity). Involved in DNA demethylation pathway by stimulating cytosine methylation (5-meC) excision, gap tailoring, and DNA ligation. Homodimer. Interacts with polynucleotide kinase (PNK), DNA polymerase-beta (POLB) and DNA ligase III (LIG3) (By similarity). Interacts with ZDP and ROS1. Binds to various forms of double-stranded DNA (e.g. methylated, unmethylated, with single-nucleotide gap flanked by 3'-phosphate or 5'-phosphate ends). Accumulates at sites of DNA damage. Reduced capacity to complete DNA demethylation initiated by ROS1.