Molecular basis of aflatoxin-induced mutagenesis-role of the aflatoxin B₁-formamidopyrimidine adduct

Aflatoxin B₁ (AFB₁) is a known carcinogen associated with early-onset hepatocellular carcinoma (HCC) and is thought to contribute to over half a million new HCCs per year. Although some of the fundamental risk factors are established, the molecular basis of AFB₁-induced mutagenesis in primate cells has not been rigorously investigated. To gain insights into genome instability that is produced as a result of replicating DNAs containing AFB₁ adducts, site-specific mutagenesis assays were used to establish the mutagenic potential of the persistent ring-opened AFB₁ adduct, AFB₁-formamidopyrimidine (AFB₁-FAPY). This lesion was highly mutagenic, yielding replication error frequencies of 97%, with the predominant base substitution being a G to T transversion. This transversion is consistent with previous mutational data derived from aflatoxin-associated HCCs. In vitro translesion synthesis assays demonstrated that polymerase (pol) ζ was the most likely candidate polymerase that is responsible for the G to T mutations induced by this adduct.