Probable E3 ubiquitin-protein ligase that acts as a regulator of double-strand breaks (DSBs) repair following DNA damage. Functions in a non-canonical fashion to harness RNF168-mediated protein recruitment to DSB-containing chromatin, thereby contributing to regulation of DSB repair pathway utilization. Once recruited to DSB repair sites by recognizing and binding ubiquitin catalyzed by RNF168, competes with TP53BP1 and BRCA1 for association with RNF168-modified chromatin, thereby favouring homologous recombination repair (HRR) and single-strand annealing (SSA) instead of non-homologous end joining (NHEJ) mediated by TP53BP1. E3 ubiquitin-protein ligase activity is not required for regulation of DSBs repair. 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 DYRK1B. Localizes to sites of double-strand breaks (DSBs) following DNA damage. Recruited to DSBs via recognition of RNF168-dependent ubiquitin products. 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). Phosphorylated by DYRK1A; phosphorylation increases RNF169 ability to block accumulation of TP53BP1 at the DSB sites. Belongs to the RNF169 family.