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 (PubMed:22492721, PubMed:30773093). 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 (PubMed:30104380, PubMed:30773093). 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 (PubMed:22733822 and PubMed:22492721). 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) (PubMed:22742833). Phosphorylated by DYRK1A; phosphorylation increases RNF169 ability to block accumulation of TP53BP1 at the DSB sites. Belongs to the RNF169 family.