title: DNA polymerase ζ limits chromosomal damage and promotes cell survival following aflatoxin exposure.
abstract: Routine dietary consumption of foods that contain aflatoxins is the second leading cause of environmental carcinogenesis worldwide. Aflatoxin-driven mutagenesis is initiated through metabolic activation of aflatoxin B1(AFB1) to its epoxide form that reacts with N7 guanine in DNA. The resulting AFB1-N7-dG adduct undergoes either spontaneous depurination or imidazole-ring opening yielding formamidopyrimidine AFB1(AFB1-Fapy-dG). Because this latter adduct is known to persist in human tissues and contributes to the high frequency G-to-T mutation signature associated with many hepatocellular carcinomas, we sought to establish the identity of the polymerase(s) involved in processing this lesion. Although our previous biochemical analyses demonstrated the ability of polymerase ζ (pol ζ) to incorporate an A opposite AFB1-Fapy-dG and extend from this mismatch, biological evidence supporting a unique role for this polymerase in cellular tolerance following aflatoxin exposure has not been established. Following challenge with AFB1, survival of mouse cells deficient in pol ζ (Rev3L-/-) was significantly reduced relative to Rev3L+/-cells or Rev3L-/-cells complemented through expression of the wild-type human REV3L. Furthermore, cell-cycle progression of Rev3L-/-mouse embryo fibroblasts was arrested in late S/G2 following AFB1exposure. These Rev3L-/-cells showed an increase in replication-dependent formation of γ-H2AX foci, micronuclei, and chromosomal aberrations (chromatid breaks and radials) relative to Rev3L+/-cells. These data suggest that pol ζ is essential for processing AFB1-induced DNA adducts and that, in its absence, cells do not have an efficient backup polymerase or a repair/tolerance mechanism facilitating survival.
authors.affiliation: Cancer Biology Program, Oregon Health & Science University, Portland, OR 97239.|Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239.
authors.forename: Ying-Chih
authors.initials: YC
authors.lastname: Lin
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239.
authors.forename: Nichole
authors.initials: N
authors.lastname: Owen
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239.
authors.forename: Irina G
authors.initials: IG
authors.lastname: Minko
authors.affiliation: Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957.
authors.forename: Sabine S
authors.initials: SS
authors.lastname: Lange
authors.forename: Junya
authors.initials: J
authors.lastname: Tomida
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, TN 37235.
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, TN 37235.|Department of Biochemistry, Vanderbilt University, Nashville, TN 37235.|Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN 37235.|Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37235.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Stone
authors.affiliation: Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957.|The University of Texas Graduate School of Biomedical Sciences, Houston, TX 77030.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Wood
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239.|Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: McCullough
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239; lloydst@ohsu.edu.|Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239.|Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97239.
authors.forename: R Stephen
authors.initials: RS
authors.lastname: Lloyd
mesh_terms: D016604:Aflatoxin B1 / Q000031:analogs & derivatives / Q000235:genetics / Q000633:toxicity; D000348:Aflatoxins / Q000633:toxicity; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects; D002869:Chromosome Aberrations / Q000187:drug effects; D003562:Cytidine / Q000031:analogs & derivatives / Q000235:genetics / Q000633:toxicity; D018736:DNA Adducts / Q000187:drug effects / Q000235:genetics; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000235:genetics*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D051379:Mice; D016296:Mutagenesis / Q000187:drug effects / Q000235:genetics; D009154:Mutation
chemical_list: D016604:Aflatoxin B1; D000348:Aflatoxins; D003562:Cytidine; D018736:DNA Adducts; D004268:DNA-Binding Proteins; D004259:DNA-Directed DNA Polymerase; C000611057:8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1; C425929:DNA polymerase zeta; C118285:REV3L protein, human; C486862:REV3L protein, mouse
keywords: aflatoxin; environmental toxins; hepatocellular carcinogenesis; mutagenesis; translesion DNA synthesis