E3 ubiquitin-protein ligase involved in DNA damage response by promoting DNA resection and homologous recombination. Recruited to sites of double-strand breaks following DNA damage and specifically promotes double-strand break repair via homologous recombination (By similarity). Together with nlk.2, involved in the ubiquitination and degradation of TCF/LEF. Also exhibits auto-ubiquitination activity in combination with ube2k. 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.2 (via C-terminus) and ube2k. Recruited at DNA damage sites. Localizes to sites of double-strand break: localization to double-strand break sites is mediated by the zinc fingers. 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.