RAD51 loading onto chromatin is a key step during the homologous recombination (HR) repair. We recently reported a new mode of RAD51 regulation, which is mediated by TOPORS E3 SUMO ligase and RAD51 SUMOylation. ATM/ATR-induced phosphorylation of TOPORS is necessary for this event, revealing a new role of these master DNA damage response kinases in HR repair.