UBE2O and USP7 co-regulate RECQL4 ubiquitinylation and homologous recombination-mediated DNA repair

The human RecQ DNA helicase, RECQL4, plays a pivotal role in maintaining genomic stability by regulating the DNA double-strand breaks (DSBs) repair pathway, and is, thus, involved in the regulation of aging and cancer onset. However, the regulatory mechanisms of RECQL4, especially its post-translational modifications, have not been fully illustrated. Here, we report that the E2/E3 hybrid ubiquitin-conjugating enzyme, UBE2O, physically interacts with RECQL4, and mediates the multi-monoubiquitinylation of RECQL4, subsequently leading to its proteasomal degradation. Functionally, we showed that UBE2O inhibits homologous recombination (HR)-mediated DSBs repair, and this inhibition depends on its E2 catalytic activity and RECQL4 expression. Mechanistically, we showed that UBE2O attenuates the interaction of RECQL4 and DNA damage repair proteins, the MRE11-RAD50-NBS1 complex and CtIP. Furthermore, we show that deubiquitinylase USP7 interacts with both UBE2O and RECQL4, and in that it antagonizes UBE2O-mediated regulation of RECQL4 stability and function. Collectively, we found a novel regulatory mechanism of ubiquitin-mediated regulation of RECQL4 in HR-mediated DSBs repair process.