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The abundant DNA adduct -methyl deoxyguanosine contributes to miscoding during replication by human DNA polymerase η.

Njuma OJ, Su Y, Guengerich FP
J Biol Chem. 2019 294 (26): 10253-10265

PMID: 31101656 · PMCID: PMC6664181 · DOI:10.1074/jbc.RA119.008986

Aside from abasic sites and ribonucleotides, the DNA adduct -methyl deoxyguanosine ( -CH dG) is one of the most abundant lesions in mammalian DNA. Because -CH dG is unstable, leading to deglycosylation and ring-opening, its miscoding potential is not well-understood. Here, we employed a 2'-fluoro isostere approach to synthesize an oligonucleotide containing an analog of this lesion ( -CH 2'-F dG) and examined its miscoding potential with four Y-family translesion synthesis DNA polymerases (pols): human pol (hpol) η, hpol κ, and hpol ι and Dpo4 from the archaeal thermophile We found that hpol η and Dpo4 can bypass the -CH 2'-F dG adduct, albeit with some stalling, but hpol κ is strongly blocked at this lesion site, whereas hpol ι showed no distinction with the lesion and the control templates. hpol η yielded the highest level of misincorporation opposite the adduct by inserting dATP or dTTP. Moreover, hpol η did not extend well past an -CH 2'-F dG:dT mispair. MS-based sequence analysis confirmed that hpol η catalyzes mainly error-free incorporation of dC, with misincorporation of dA and dG in 5-10% of products. We conclude that -CH 2'-F dG and, by inference, -CH dG have miscoding and mutagenic potential. The level of misincorporation arising from this abundant adduct can be considered as potentially mutagenic as a highly miscoding but rare lesion.

© 2019 Njuma et al.

MeSH Terms (8)

Deoxyguanosine DNA-Directed DNA Polymerase DNA Adducts DNA Damage DNA Repair DNA Replication Humans Molecular Structure

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