Mapping of (+/-)-anti-benzo[a]pyrene diol epoxide adducts to human c-Ha-ras1 protooncogene.
The relative reactivity of the chemical carcinogen (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+/-)-anti-BPDE] to the guanine bases of the first two coding exons of the human c-Ha-ras1 protooncogene is determined to test if (+/-)-anti-BPDE reactivity is correlated with mutations reported for human c-Ha-ras1 protooncogene activation. Plasmid DNA containing the sequence for the human c-Ha-ras1 gene is modified with (+/-)-anti-BPDE to provide approximately 1 covalent adduct per 250 bp. High-resolution mapping of the covalent adducts is achieved by laser-induced photolysis of 32P-labeled restriction fragments of the BPDE-modified plasmid DNA. The (+/-)-anti-BPDE binding profiles to exons 1 and 2 of the human c-Ha-ras1 protooncogene show enhanced reactivity to guanine-rich regions. The guanine bases of oncogene-activating codons 12 (GGC) and 13 (GGT) are 5 times more reactive than the least reactive guanine analyzed within this region of the gene. The guanine base of oncogene-activating codon 61 (CAG) exhibits intermediate reactivity relative to the guanines analyzed within this region of the gene. Although preferential chemical reactivity plays a role in the activation of the c-Ha-ras1 protooncogene, the in vivo activation of the c-Ha-ras1 protooncogene by (+/-)-anti-BPDE is a complex process, with other important factors involved in the chemically induced activation.
Dittrich
K A
KA
Department of Chemistry, University of Rochester, New York 14627-0216.
Krugh
T R
TR
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002874:Chromosome Mapping; D003062:Codon / Q000235:genetics / Q000502:physiology; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005091:Exons / Q000502:physiology; D005786:Gene Expression Regulation; D011905:Genes, ras / Q000235:genetics / Q000502:physiology*; D006147:Guanine / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010777:Photochemistry; D011519:Proto-Oncogenes / Q000235:genetics* / Q000502:physiology
D003062:Codon; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D006147:Guanine; D004247:DNA