title: Analysis of site-specific binding of (+/-)-anti-benzo[a]pyrene diol epoxide to restriction fragments of pBR322 DNA via photochemical mapping.
abstract: The binding sites and relative reactivity of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+/-)-anti-BPDE] covalently bound to restriction fragments of pBR322 DNA are determined. (+/-)-anti-BPDE-modified DNA undergoes a photodissociation at the site of these adducts when irradiated with 355-nm laser light, resulting in a scission of the DNA sugar-phosphate backbone producing DNA fragments similar to those of Maxam-Gilbert sequencing reactions. The binding sites of (+/-)-anti-BPDE with each DNA base are determined by sequencing gel analysis of the BPDE-mediated photolysis and laser densitometry of the resulting banding patterns. This technique was used to analyze the binding of (+/-)-anti-BPDE to the 5' and 3' strands of the EcoRI/EcoRV and BamHI/SalI restriction fragments of pBR322 DNA. The reactivity of (+/-)-anti-BPDE to guanine bases within guanine-rich regions of DNA is enhanced by as much as a factor of 17 relative to the least reactive guanines which are flanked by non-guanine bases. The results also show enhanced photocleavage of the backbone corresponding to non-guanine bases in guanine-rich regions. These results suggest either that non-guanine basis in guanine-rich regions are more reactive than identical bases in other regions of the restriction fragment or that photocleavage of the backbone occurs adjacent to a BPDE-modified guanine. The binding profiles of (+/-)-anti-BPDE to pBR322 DNA at a binding density of 0.52 and 0.93 BPDE adduct per strand gave essentially identical binding patterns.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Chemistry, University of Rochester, New York 14627-0216.
authors.forename: K A
authors.initials: KA
authors.lastname: Dittrich
authors.forename: T R
authors.initials: TR
authors.lastname: Krugh
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000737:chemistry / Q000378:metabolism*; D001345:Autoradiography; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D018736:DNA Adducts; D004278:DNA, Superhelical / Q000378:metabolism*; D015246:Deoxyribonuclease EcoRI / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D008969:Molecular Sequence Data; D010777:Photochemistry; D010957:Plasmids; D015183:Restriction Mapping; D013237:Stereoisomerism
chemical_list: D018736:DNA Adducts; D004278:DNA, Superhelical; C043931:benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide-DNA; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D004247:DNA; D015246:Deoxyribonuclease EcoRI; D015252:Deoxyribonucleases, Type II Site-Specific; C027440:GATATC-specific type II deoxyribonucleases