REV1 is a bifunctional DNA polymerase that maintains genome stability through two primary mechanisms: translesion DNA synthesis (TLS) and coordination of polymerase switching at DNA replication forks. As a molecular adapter protein, REV1 recruits and mediates switches between low-fidelity inserter polymerases and extender polymerases like POLζ at sites of DNA damage, functioning independently of its catalytic activity 1. REV1 possesses deoxycytidyl transferase activity, preferentially incorporating deoxycytidine opposite apurinic/apyrimidinic sites, uracil, and various damaged DNA templates with low fidelity on undamaged DNA 2. The enzyme demonstrates accurate synthesis opposite 8-oxoG and O6-meG lesions with moderate efficiency, and replicates thymine glycol in an error-prone manner 2. REV1's activity is regulated through post-translational modifications and protein interactions, with RAD18-dependent PCNA monoubiquitination promoting gap filling during G2 phase 3. In disease contexts, REV1 contributes to APOBEC3-mediated mutagenesis in cancer cells 4, and its suppression by fumarate binding enhances chemotherapy sensitivity in ovarian cancer 5. Additionally, REV1 has been identified as a novel susceptibility gene for migraine through transcriptome-wide association studies 6.