RNF169 limits 53BP1 deposition at DSBs to stimulate single-strand annealing repair

Significance 53BP1 restrains DNA end resection, and its dosage imbalance upsets DNA double-strand break (DSB) repair pathway choice. Here, by monitoring 53BP1 distribution on DSB-flanking chromatin, we have established a dose-dependent role of the RING finger protein RNF169 in limiting 53BP1 DSB deposition. Moreover, we found that forced expression of RNF169 overcomes 53BP1 activity and stimulates mutagenic DSB repair via the single-strand annealing pathway. Our findings suggest that aberrant expression of RNF169 may represent a deleterious factor in DSB repair control and in maintenance of genome stability.
Unrestrained 53BP1 activity at DNA double-strand breaks (DSBs) hampers DNA end resection and upsets DSB repair pathway choice. RNF169 acts as a molecular rheostat to limit 53BP1 deposition at DSBs, but how this fine balance translates to DSB repair control remains undefined. In striking contrast to 53BP1, ChIP analyses of AsiSI-induced DSBs unveiled that RNF169 exhibits robust accumulation at DNA end-proximal regions and preferentially targets resected, RPA-bound DSBs. Accordingly, we found that RNF169 promotes CtIP-dependent DSB resection and favors homology-mediated DSB repair, and further showed that RNF169 dose-dependently stimulates single-strand annealing repair, in part, by alleviating the 53BP1-imposed barrier to DSB end resection. Our results highlight the interplay of RNF169 with 53BP1 in fine-tuning choice of DSB repair pathways.