Probable E3 ubiquitin-protein ligase that acts as a negative regulator of double-strand breaks (DSBs) repair following DNA damage. 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. Localizes to sites of double-strand breaks (DSBs) following DNA damage. The MIU motif (motif interacting with ubiquitin) mediates the interaction with both 'Lys-48'- and 'Lys-63'-linked ubiquitin chains. The UMI motif also mediates interaction with ubiquitin. The specificity for different types of ubiquitin is mediated by juxtaposition of ubiquitin-binding motifs (MIU and UMI motifs) with LR motifs (LRMs) (By similarity). Belongs to the RNF169 family.