Error-prone lesion bypass by human DNA polymerase eta

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Abstract
DNA lesion bypass is an important cellular response to genomic damage during replication. Human DNA polymerase eta (Pol(eta)), encoded by the Xeroderma pigmentosum variant (XPV) gene, is known for its activity of error-free translesion synthesis opposite a TT cis-syn cyclobutane dimer. Using purified human Pol(eta), we have examined bypass activities of this polymerase opposite several other DNA lesions. Human Pol(eta) efficiently bypassed a template 8-oxoguanine, incorporating an A or a C opposite the lesion with similar efficiencies. Human Pol(eta) effectively bypassed a template abasic site, incorporating an A and less frequently a G opposite the lesion. Significant -1 deletion was also observed when the template base 5' to the abasic site is a T. Human Pol(eta) partially bypassed a template (+)-trans-anti-benzo[a]pyrene-N:(2)-dG and predominantly incorporated an A, less frequently a T, and least frequently a G or a C opposite the lesion. This specificity of nucleotide incorporation correlates well with the known mutation spectrum of (+)-trans-anti-benzo[a]pyrene-N:(2)-dG lesion in mammalian cells. These results show that human Pol(eta) is capable of error-prone translesion DNA syntheses in vitro and suggest that Pol(eta) may bypass certain lesions with a mutagenic consequence in humans.