Human Translesion Synthesis Polymerases polκ and polη Perform Error-Free Replication across -dG Methyleugenol and Estragole DNA Adducts.

The secondary metabolites of polypropanoids, methyleugenol (MEG), and estragole (EG), found in many herbs and spices, are commonly used as food flavoring agents and as ingredients in cosmetics. MEG and EG have been reported to cause hepatocarcinogenicity in rodents, human livers, and lung cells. The formation of -dG and -dA DNA adducts is primarily attributed to the carcinogenicity of these compounds. Therefore, these compounds have been classified as "possible human carcinogens" by the International Agency for Research on Cancer and "reasonably anticipated to be a human carcinogen" by the National Toxicology Program. Herein, we report the synthesis of the -MEG-dG and -EG-dG modified oligonucleotides to study the mutagenicity of these DNA adducts. Our studies show that -MEG-dG and -EG-dG could be bypassed by human translesion synthesis (TLS) polymerases hpolκ and hpolη in an error-free manner. The steady-state kinetics of dCTP incorporation by hpolκ across -MEG-dG and -EG-dG adducts show that the catalytic efficiencies (/) were ∼2.5- and ∼4.4-fold higher, respectively, compared to the unmodified dG template. A full-length primer extension assay demonstrates that hpolκ exhibits better catalytic efficiency than hpolη. Molecular modeling and dynamics studies capturing pre-insertion, insertion, and post-insertion steps reveal the structural features associated with the efficient bypass of the -MEG-dG adduct by hpolκ and indicate the reorientation of the adduct in the active site allowing the successful insertion of the incoming nucleotide. Together, these results suggest that though hpolκ and hpolη perform error-free TLS across MEG and EG during DNA replication, the observed carcinogenicity of these adducts could be attributed to the involvement of other low fidelity polymerases.