E3 ubiquitin-protein ligase involved in DNA damage response by promoting DNA resection and homologous recombination (PubMed:26502055, PubMed:26502057). Recruited to sites of double-strand breaks following DNA damage and specifically promotes double-strand break repair via homologous recombination (PubMed:26502055, PubMed:26502057). Two different, non-exclusive, mechanisms have been proposed. According to a report, regulates the choice of double-strand break repair by favoring homologous recombination over non-homologous end joining (NHEJ): acts by mediating ubiquitination of XRCC5/Ku80, leading to remove the Ku complex from DNA breaks, thereby promoting homologous recombination (PubMed:26502055). According to another report, cooperates with UBE2Ds E2 ubiquitin ligases (UBE2D1, UBE2D2, UBE2D3 or UBE2D4) to promote homologous recombination by mediating ubiquitination of RBBP8/CtIP (PubMed:26502057). Together with NLK, involved in the ubiquitination and degradation of TCF/LEF (PubMed:16714285). Also exhibits auto-ubiquitination activity in combination with UBE2K (PubMed:16714285). May act as a negative regulator in the Wnt/beta-catenin-mediated signaling pathway (PubMed:16714285). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts with NLK (PubMed:16714285). Interacts with XRCC5/Ku80 (PubMed:26502055). Interacts with RBBP8/CtIP (PubMed:26502057). Recruited at DNA damage sites (PubMed:26502055). Localizes to sites of double-strand break: localization to double-strand break sites is mediated by the zinc fingers (PubMed:26502055, PubMed:26502057). The zinc finger domains (C2H2-type and C2HC-type zinc fingers) bind DNA and mediate recruitment to double-strand break sites. They show strong preference for DNA with 5'- or 3'-single-stranded overhangs, while they do not bind blunt-ended double-stranded DNA or poly(ADP-ribose) (PAR) polymers. Auto-ubiquitinated.