CHAF1A promotes the translesion DNA synthesis pathway in response to DNA replication stress

The translesion DNA synthesis (TLS) pathway mediated by proliferating cell nuclear antigen (PCNA) monoubiquitination is an essential mechanism by which cancer cells bypass DNA damage caused by DNA replication stress to maintain genomic stability and cell survival. Chromatin assembly factor 1 subunit A (CHAF1A) traditionally promotes histone assembly during DNA replication. Here, we revealed that CHAF1A is a novel regulator of the TLS pathway. High expression of CHAF1A is significantly associated with poor prognosis in cancer patients. CHAF1A promotes fork restart under DNA replication stress and maintains genome integrity. CHAF1A enhances the interaction between PCNA and E3 ubiquitin protein ligase RAD18 and promotes PCNA monoubiquitination, thereby promoting the recruitment of Y-family DNA polymerase Pol η and enhancing cancer cell resistance to stimuli that trigger replication fork blockade. Mechanistically, CHAF1A-mediated PCNA monoubiquitination is independent of CHAF1A-PCNA interaction. CHAF1A interacts with both RAD18 and replication protein A2 (RPA2), mediating RAD18 binding on chromatin in response to DNA replication stress. Taken together, these findings improve our understanding of the mechanisms that regulate the TLS pathway and provide insights into the relationship between CHAF1A and the malignant progression of cancers. ### Competing Interest Statement The authors have declared no competing interest.