Interaction of (+-)Benzo(A)Pyrene-7 beta ,8 alpha -Diol-9 alpha ,10 alpha -Epoxide with Fractionated Eukaryotic DNA

摘要

Chemically unreactive polycyclic aromatic hydrocarbons (PAH) exert their carcinogenic and mutagenic effects only after they are metabolized to chemically reactive species. These reactive metabolites can undergo covalent interactions with cellular RNA, DNA, and protein as well as with synthetic copolymers of nucleic acids and proteins. Studies of the binding of metabolites of benzo(a)pyrene to DNA have provided evidence that benzo(a)pyrene-7,8-diol-9,10-epoxide is responsible for most of the bound adducts, and that this interaction is primarily with the guanine residues (90%) and secondarily to adenine residues (2 to 5%). The significance of the interaction of benzo(a)pyrene-diol-epoxide with guanine, to the mechanism of chemical carcinogenesis, is not understood. In view of the apparent importance of this carcinogen-DNA interaction, we were interested in determining several parameters of this reaction that might contribute to an understanding of the mechanism of chemical carcinogenesis. Since the carcinogen is known to react with the guanine residues in DNA, one of our major aims was to determine if there are any hot spots in eukaryotic DNA where the diol-epoxide shows a preferential binding. It is well known that the eukaryotic genome is quite complex and consists of localized regions of (G+C)-rich and (A+T)-rich DNA sequences. These specific DNA sequences will enable detailed studies of the role of (G+C)-content as well as sequence specificity in the interaction of carcinogens with DNA. Our ability to carry out the present studies on the interaction of carcinogens with various fractions of mouse and calf DNA was facilitated by the recent development of techniques in our laboratory for the enrichment of (G+C)-rich and (A+T)-rich DNA sequences. A preliminary report is herewith presented on the interaction of benzo(a)pyrene-diol-epoxide with fractionated mouse and calf DNA. (ERA citation 04:024603)