Error-prone replication bypass of the primary aflatoxin B1 DNA adduct, AFB1-N7-Gua.
Hepatocellular carcinomas (HCCs) are the third leading cause of cancer deaths worldwide. The highest rates of early onset HCCs occur in geographical regions with high aflatoxin B1 (AFB1) exposure, concomitant with hepatitis B infection. Although the carcinogenic basis of AFB1 has been ascribed to its mutagenic effects, the mutagenic property of the primary AFB1-DNA adduct, AFB1-N7-Gua, in mammalian cells has not been studied extensively. Taking advantage of the ability to create vectors containing a site-specific DNA adduct, the mutagenic potential was determined in primate cells. This adduct was highly mutagenic following replication in COS-7 cells, with a mutation frequency of 45%. The spectrum of mutations was predominantly G to T base substitutions, a result that is consistent with previous mutation data derived from aflatoxin-associated HCCs. To assess which DNA polymerases (pol) might contribute to the mutational outcome, in vitro replication studies were performed. Unexpectedly, replicative pol δ and the error-prone translesion synthesis pol ζ were able to accurately bypass AFB1-N7-Gua. In contrast, replication bypass using pol κ was shown to occur with low fidelity and could account for the commonly detected G to T transversions.
From the Cancer Biology Program, Oregon Institute of Occupational Health Sciences, and.
Ying-Chih
YC
Lin
the Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, and.
Liang
L
Li
the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
Alena V
AV
Makarova
the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
Peter M
PM
Burgers
the Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, and.
Michael P
MP
Stone
Oregon Institute of Occupational Health Sciences, and Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon 97239, lloydst@ohsu.edu.
R Stephen
RS
Lloyd
D016604:Aflatoxin B1 / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D019556:COS Cells; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000235:genetics*; D002522:Chlorocebus aethiops; D018736:DNA Adducts / Q000235:genetics* / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics*; D017354:Point Mutation
D018736:DNA Adducts; C072611:aflatoxin B1-DNA adduct; D016604:Aflatoxin B1; D004259:DNA-Directed DNA Polymerase
DNA Polymerase; DNA Replication; Environmental Carcinogenesis; Genomic Instability; Hepatocellular Carcinoma; Site-directed Mutagenesis; Site-specific DNA Adduct; Translesion DNA Synthesis