Base sequence selectivity in the binding of 7(R),8(S)-dihydroxy-9(S),10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene to...

The effect of nucleotide sequence on the binding of 7(R),8(S)-dihydroxy-9(S),10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE] to the exocyclic amino group of deoxyguanosine was investigated in duplexes formed by self-complementary oligodeoxyribonucleotide decamers which contained two deoxyguanosines (dGs) within unique sequences. A 35S-postlabeling procedure was developed for analysis of (+)-anti-BPDE adducts as dinucleotides containing 5'-(+)-anti-BPDE-dG adducts. This allows identification of the 3' neighbor of the reacted guanine and permits quantitation of the binding of (+)-anti-BPDE to each specific guanine in the oligodeoxyribonucleotide duplexes. Of all the central dG-containing sequences studied, dG surrounded by deoxycytidines (CGC) reacted to the greatest extent: over 4-fold more (+)-anti-BPDE bound to this central dG compared to the least reactive deoxyguanosine (AGT). (+)-anti-BPDE exhibited a preference for binding to a central deoxyguanosine when either the 5' or 3' neighbor was deoxyguanosine. The binding of (+)-anti-BPDE to oligodeoxyribonucleotide duplexes containing different numbers of consecutive dGs was analyzed in order to determine how the length of these sequences influences binding. Increases in the length of consecutive deoxyguanosine residues from 3 to 5 had little effect on the quantity of (+)-anti-BPDE bound to dG above that expected from the presence of a neighboring dG and an increase in the number of dG residues available for reaction. The results obtained with these oligodeoxyribonucleotide duplexes were consistent with the data available for the reaction of (+)-anti-BPDE with DNA, indicating that these duplexes are a valuable model for studying the effect of base sequence on the interaction of BPDE isomers with DNA. The dinucleotide postlabeling technique developed for these studies, with appropriate oligodeoxyribonucleotides and chromatographic conditions, will be useful for determining the effect of base sequence on the binding of other hydrocarbon diol epoxides as well as other reactive hydrocarbon metabolites to deoxyguanosine or deoxyadenosine in oligodeoxyribonucleotide duplexes and fragments of DNA.