Aflatoxin B1-induced DNA damage and its repair

Aflatoxin B1 (AFB1)-N7-guanine is the predominant adduct formed upon the reaction of AFB1-8,9-exo-epoxide with guanine residues in DNA. AFB1-N7-guanine can convert to the ring-opened formamidopyrimidine, or the adducted strand can undergo depurination. AFB1-N7-guanine and AFB1-formamidopyrimidine are thought to be predominantly repaired by nucleotide excision repair in bacteria, yeast and mammals. Although AFB1-formamidopyrimidine is removed less efficiently than AFB1-N7-guanine in mammals, both lesions are repaired with equal efficiencies in bacteria, reflecting differences in damage recognition between bacterial and mammalian repair systems. Furthermore, DNA repair activity and modulation of repair by AFB1 seem to be major determinants of susceptibility to AFB1-induced carcinogenesis.