DNA polymerase v (POLN or pol v) is a newly discovered A family polymerase that generates a high error rate when incorporating nucleotides opposite dG; its translesion DNA synthesis (TLS) capability has only been demonstrated for high fidelity replication bypass of thymine glycol lesions. In the current investigation, we describe a novel TLS substrate specificity of pol v, demonstrating that it is able to bypass exceptionally large DNA lesions whose linkages are through the DNA major groove. Specifically, pol v catalyzed efficient and high fidelity TLS past peptides linked to N6-dA via a reduced Schiff base linkage with a ã-hydroxypropano-dA. Additionally, pol v could bypass DNA interstrand cross-links with linkage between N 6-dAs in complementary DNA strands. However, the chemically identical DNA-peptide and DNA interstrand cross-links completely blocked pol v when they were located in the minor groove via a N2-dG linkage. Furthermore, we showed that pol v incorporated a nucleotide opposite the 1,N 6-etheno-dA (ådA) in an error-free manner and (+)-trans-anti-benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxidedA [(+)-BPDE-dA] in an error-prone manner, albeit with a greatly reduced capability. Collectively, these data suggest that although pol v bypass capacity cannot be generalized to all major groove DNA adducts, this polymerase could be involved in TLS when genomic replication is blocked by extremely large major groove DNA lesions. In view of the recent observation that pol v may have a role in cellular tolerance to DNA cross-linking agents, our findings provide biochemical evidence for the potential functioning of this polymerase in the bypass of some DNA-protein and DNA-DNA cross-links.
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