Rev1 plays central roles in mammalian DNA-damage tolerance in response to UV irradiation.

Rev1, a Y-family DNA polymerase, is involved in the tolerance of DNA damage by translesion DNA synthesis (TLS). Previous studies have shown that the C-terminal domain (CTD) and ubiquitin (Ub)-binding (UBM) domains of Rev1 play important roles in UV-damage tolerance, but how these domains contribute to the process remains unclear. In this study, we created Ub mutations in a proliferating cell nuclear antigen (PCNA)-Ub fusion that differentially affect its interaction with Rev1 and Polη and found that UV-damage tolerance depends on its interaction with Rev1 but not Polη. We also created Rev1-UBM mutations altering its interaction with a PCNA-Ub fusion and Rev1-CTD mutations affecting its interaction with Polη and the Rev7 subunit of Polζ. We thus demonstrated that elevated expression of Rev1 alone is sufficient to confer enhanced UV-damage tolerance and that this tolerance depends on its physical interaction with monoubiquitinated PCNA and Polζ but is independent of Polη. Collectively, these studies reveal central roles played by Rev1 in coordinating UV-damage response pathway choice in mammalian cells.