ZNF451 collaborates with RNF8 to regulate RNF168 localization and amplify ubiquitination signaling to promote DNA damage repair and regulate radiosensitivity

The ubiquitination of histone H2A/H2AX, catalyzed by RNF8/RNF168, is a crucial step in the repair of DNA double-strand breaks (DSBs), playing a significant role in transmitting and amplifying DNA damage response signals. However, the upstream regulatory mechanisms of RNF168 remain unclear. Here, we demonstrate that ZNF451 catalyzes the SUMOylation of RNF168, thereby regulating the ubiquitination of histone H2A/H2AX. Specifically, ZNF451 rapidly responds to radiation-induced DNA damage, accumulating abundantly at damage sites and catalyzing the SUMO2 modification of RNF168. This modification stabilizes RNF168, enhancing its accumulation at damage sites, which increases the ubiquitination levels of downstream histone H2A/H2AX and promotes the DNA damage repair process. Furthermore, we find that ZNF451 and RNF8 jointly regulate RNF168 in a novel manner, exhibiting both competitive and cooperative characteristics. The interaction between RNF168 and either ZNF451 or RNF8 mutually inhibits each other. However, simultaneous loss of ZNF451 and RNF8 markedly impedes the recruitment of RNF168 to damage sites. Whereas, varying expression levels of ZNF451 and RNF8 suggest that both facilitate the interaction between RNF168 and the downstream factor H2AX, but the interaction plateaus beyond a specific threshold. Altogether, these findings reveal that the SUMOylation catalyzed by ZNF451 is involved in regulating RNF168-induced ubiquitin signaling in DSBs repair and suggest that ZNF451 could serve as a potential therapeutic target in tumor radiotherapy.