title: Bypass of Mutagenic O(6)-Carboxymethylguanine DNA Adducts by Human Y- and B-Family Polymerases.
abstract: The generation of chemical alkylating agents from nitrosation of glycine and bile acid conjugates in the gastrointestinal tract is hypothesized to initiate carcinogenesis. O(6)-carboxymethylguanine (O(6)-CMG) is a product of DNA alkylation derived from nitrosated glycine. Although the tendency of the structurally related adduct O(6)-methylguanine to code for the misincoporation of TTP during DNA replication is well-established, the impact of the presence of the O(6)-CMG adduct in a DNA template on the efficiency and fidelity of translesion DNA synthesis (TLS) by human DNA polymerases (Pols) has hitherto not been described. Herein, we characterize the ability of the four human TLS Pols η, ι, κ, and ζ and the replicative Pol δ to bypass O(6)-CMG in a prevalent mutational hot-spot for colon cancer. The results indicate that Pol η replicates past O(6)-CMG, incorporating dCMP or dAMP, whereas Pol κ incorporates dCMP only, and Pol ι incorporates primarily dTMP. Additionally, the subsequent extension step was carried out with high efficiency by TLS Pols η, κ, and ζ, while Pol ι was unable to extend from a terminal mismatch. These results provide a first basis of O(6)-CMG-promoted base misincorporation by Y- and B-family polymerases potentially leading to mutational signatures associated with colon cancer.
authors.affiliation: Department of Health Sciences and Technology, ETH Zürich , Schmelzbergstrasse 9, 8092 Zürich, Switzerland.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Räz
authors.affiliation: Center for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield , Sheffield S3 7HF, United Kingdom.
authors.forename: Hannah R
authors.initials: HR
authors.lastname: Dexter
authors.affiliation: Center for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield , Sheffield S3 7HF, United Kingdom.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Millington
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU) , Erling Skjalgssons gate 1, 7491 Trondheim, Norway.
authors.forename: Barbara
authors.initials: B
authors.lastname: van Loon
authors.affiliation: Center for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield , Sheffield S3 7HF, United Kingdom.
authors.forename: David M
authors.initials: DM
authors.lastname: Williams
authors.affiliation: Department of Health Sciences and Technology, ETH Zürich , Schmelzbergstrasse 9, 8092 Zürich, Switzerland.
authors.forename: Shana J
authors.initials: SJ
authors.lastname: Sturla
mesh_terms: D018736:DNA Adducts / Q000737:chemistry* / Q000378:metabolism* / Q000633:toxicity; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000633:toxicity; D006801:Humans; D009153:Mutagens / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D009154:Mutation; D015538:Nitrosation; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics
chemical_list: D018736:DNA Adducts; C117307:KRAS protein, human; D009153:Mutagens; D006147:Guanine; C008449:O-(6)-methylguanine; D004259:DNA-Directed DNA Polymerase; D016283:Proto-Oncogene Proteins p21(ras)