title: 8-Hydroxyguanine, an abundant form of oxidative DNA damage, causes G----T and A----C substitutions.
abstract: Mutations caused by oxidative DNA damage may contribute to human disease. A major product of that damage is 8-hydroxyguanine (oh8Gua). Because of differences in experimental design, the base pairing specificity of oh8G in vivo is not completely resolved. Here, oh8dGTP and DNA polymerase were used in two complementary bacteriophage plaque color assays to examine the mutagenic specificity of oh8Gua in vivo. The first is a reversion assay that detects all three single-base substitutions caused by misreading of guanine analogues inserted at a specific site. oh8Gua at that site gave a mutation frequency of 0.7%. Twenty-two of the 23 mutations were G----T substitutions. The second assay, a forward mutation assay, tests the mispairing potential of any altered nucleotide 1) during incorporation as substrate nucleotide, and 2) after multiple incorporations into a single-stranded DNA gap region of M13mp2. Substituting oh8dGTP for dGTP during polymerization produced 16% mutants; two classes of mutations were observed, both caused by pairing of oh8Gua with A. Seventy-six of 78 mutations were A----C substitutions, and two were G----T substitutions. These assays thus illustrate mutagenic replication of oh8Gua as template causing G----T substitutions and misincorporation of oh8Gua as substrate causing A----C substitutions, both caused by oh8Gua.A mispairs.
authors.affiliation: Gottstein Memorial Cancer Research Laboratory, University of Washington, Seattle 98195.
authors.forename: K C
authors.initials: KC
authors.lastname: Cheng
authors.forename: D S
authors.initials: DS
authors.lastname: Cahill
authors.forename: H
authors.initials: H
authors.lastname: Kasai
authors.forename: S
authors.initials: S
authors.lastname: Nishimura
authors.forename: L A
authors.initials: LA
authors.lastname: Loeb
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D001482:Base Composition; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D004249:DNA Damage; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D009711:Nucleotides / Q000235:genetics; D010084:Oxidation-Reduction
chemical_list: D004269:DNA, Bacterial; D009711:Nucleotides; C024829:8-hydroxyguanine; D006147:Guanine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004259:DNA-Directed DNA Polymerase; D003849:Deoxyguanosine