UHRF1 Controls the Timing of RAD51 Removal During DNA Damage Repair Through Suppressing RFWD3

The RAD51 recombinase is evolutionarily conserved critical for homologous recombination (HR)-mediated repair of DNA double-strand breaks. It binds to single strand DNA to form protein-DNA filaments for homology searching and pairing during HR repair. RFWD3 is an E3 ubiquitin ligase shown to remove RAD51 at the completion of HR repair through ubiquitination and degradation of RAD51. However, it remains elusive what prevents RFWD3 from attacking RAD51 in the absence of DNA damage and early on during the repair process. Here, we show that it is UHRF1 that protects RAD51, and it does so by acting as an E3 ubiquitin ligase of RFWD3 is demonstrated. Interestingly, RAD51 also protects RFWD3 from UHRF1, thereby establishing a negative feedback circuit that regulates the protein levels of RFWD3 and RAD51. Furthermore, it is shown that the ubiquitination of RFWD3 is regulated by phosphorylation status of UHRF1, and that phosphatase PP4 is important for modulating UHRF1 activity. Altogether, these regulatory mechanisms ensure that the recombinase RAD51 is maintained at appropriate levels for HR repair.