title: Factors influencing the covalent binding of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene to ribonucleic acids.
abstract: The covalent binding of the ultimate carcinogen (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [alpha]pyrene (BPDE) to enriched ovalbumin messenger RNA (mRNAov) of known sequence was examined. Incubation of mRNAov with elevated concentrations of labeled BPDE in TE buffer (0.02 M Tris X HCl, 1 mM EDTA, pH 7.2) containing 0.1 M KCl and 10 mM MgCl2 resulted in approximately 30 BPDEs covalently bound per RNA molecule. Covalent binding in the absence of KCl and MgCl2 resulted in a significant increase in binding to 110 BPDEs bound per molecule or modification of 12% of the total guanosine and adenosine nucleotides present. The nucleoside adducts formed were nearly all guanosine and adenosine in a ratio of 1.6:1.0. It was also observed that digestion of mRNAov with T2 RNase prior to reaction with BPDE resulted in a 52% decrease in guanosine adduct formation and a 93% decrease in adenosine adducts compared with undigested controls. Comparison of the binding of labeled BPDE to 18 S and 28 S ribosomal RNAs and to mRNAov revealed that the guanosine adduct to adenosine adduct ratio and the number of BPDEs bound increased with increasing G-C content. The results reported here show that ionic composition of the medium, G-C content, and the presence of a polymeric state can significantly influence the quantitative and/or qualitative nucleoside BPDE adducts formed.
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D000818:Animals; D001580:Benzopyrenes / Q000378:metabolism*; D002273:Carcinogens / Q000378:metabolism*; D002645:Chickens; D005260:Female; D007700:Kinetics; D010047:Ovalbumin / Q000235:genetics; D010057:Oviducts; D011061:Poly A / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D014316:Tritium
chemical_list: D001580:Benzopyrenes; D002273:Carcinogens; D012333:RNA, Messenger; D014316:Tritium; D011061:Poly A; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D012313:RNA; D010047:Ovalbumin