Error-prone DNA polymerase specifically involved in DNA repair (PubMed:11013228, PubMed:11387224). Plays an important role in translesion synthesis, where the normal high-fidelity DNA polymerases cannot proceed and DNA synthesis stalls (PubMed:11013228, PubMed:11387224, PubMed:14630940, PubMed:15199127). Favors Hoogsteen base-pairing in the active site (PubMed:15254543). Inserts the correct base with high-fidelity opposite an adenosine template (PubMed:15254543). Exhibits low fidelity and efficiency opposite a thymidine template, where it will preferentially insert guanosine (PubMed:11013228). May play a role in hypermutation of immunoglobulin genes (PubMed:12410315). Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but may not have lyase activity (PubMed:11251121, PubMed:14630940). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Binds nucleotide much more tightly and catalyzes nucleotide insertion much more efficiently in the presence of Mg(2+) than in the presence of Mn(2+). Interacts with POLH (PubMed:12606586). Interacts with REV1 (By similarity). Interacts with ubiquitin (By similarity). Binding to ubiquitin mediates localization to replication forks after UV-induced DNA damage. Ubiquitous. Highly expressed in testis. The catalytic core consists of fingers, palm and thumb subdomains, but the fingers and thumb subdomains are much smaller than in high-fidelity polymerases; residues from five sequence motifs of the Y-family cluster around an active site cleft that can accommodate DNA and nucleotide substrates with relaxed geometric constraints, with consequently higher rates of misincorporation and low processivity. Ubiquitin-binding motif 1 and ubiquitin-binding motif 2 regulate POLI protein monoubiquitination and localization to nuclear foci after UV-induced DNA damage. Monoubiquitinated. Protein monoubiquitination prevents POLI binding to ubiquitin via the ubiquitin-binding motif 1 and ubiquitin-binding motif 2. Belongs to the DNA polymerase type-Y family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.