Trans-1,2-dihydro-1,2-dihydroxy-6-aminochrysene is metabolized to form a major adduct with deoxyguanosine and produces mutations in the hprt gene of Chinese hamster ovary cells at G:C basepairs.
6-Nitrochrysene can be activated to genotoxic derivatives by two major metabolic pathways: nitroreduction to N-hydroxy-6-aminochrysene, and a combination of ring-oxidation and nitroreduction that involves the intermediate formation of trans-1,2-dihydro-1,2-dihydroxy-6-aminochrysene (6-AC-1,2-dihydrodiol). The DNA adduct formed from this latter pathway was evaluated by reacting individual deoxynucleoside 5'-monophosphates with 6-AC-1,2-dihydrodiol in the presence of liver microsomal enzymes from 3-methylcholanthrene-pretreated rats. Binding was greatest to deoxyguanosine monophosphate and the major deoxyguanosine (dG) adduct co-chromatographed with the single major adduct formed from the microsome-catalyzed reaction of 6-AC-1,2-dihydrodiol with DNA. In order to characterize the mutational changes associated with the 6-AC-1,2-dihydrodiol pathway, we analyzed the mutational spectrum produced by 6-AC-1,2-dihydrodiol in the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene of CHO-K1 cells. cDNA was synthesized from the RNA of 28 6-thioguanine-resistant mutants, the hprt coding region amplified by the polymerase chain reaction, and the DNA products directly sequenced. Twenty independent primary mutations were found: 12 G:C-->T:A transversions, three G:C-->C:G transversions, one G:C-->A:T transition, one A:T-->T:A transversion, two -1 frameshift mutations in sequences containing consecutive guanines, and one 11 bp deletion. All G:C basepair substitutions had the mutated dG on the non-transcribed strand and 86% of the G:C basepair substitutions had one purine 3' to the mutated dG. The pattern of 6-AC-1,2-dihydrodiol-induced basepair substitutions was distinct from the pattern observed in solvent control mutants. These results are consistent with the formation of a promutagenic dG adduct from a metabolite of 6-AC-1,2-dihydrodiol.
Li
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Division of Biochemical, National Center for Toxicological Research, Jefferson, AR 72079.
Heflich
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RH
Delclos
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KB
D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002911:Chrysenes / Q000378:metabolism*; D006224:Cricetinae; D004247:DNA / Q000378:metabolism*; D003849:Deoxyguanosine / Q000378:metabolism*; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008748:Methylcholanthrene; D008862:Microsomes, Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation
D002911:Chrysenes; C057269:6-aminochrysene-1,2-dihydrodiol; D008748:Methylcholanthrene; D004247:DNA; D007041:Hypoxanthine Phosphoribosyltransferase; D003849:Deoxyguanosine