Benzo(a)pyrene is converted into a potent chemical carcinogen by cellular metabolism. This intermediate is the 7 beta, 8 alpha- dihydroxy-9 alpha,lO alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti-BPDE). The active metabolite occurs as four diastereomers the (+)- and (-)-anti- and (+)- and (-)-syn-BPDEs. The most mutagenic and carcinogenic isomer is the (+)-anti-BPDE. We propose to continue our BPDE-DNA studies on two fronts: (i) elucidation of the physical binding and covalent binding mechanisms of the four BPDE diastereomers to natural and synthetic nucleic acid polymers and (ii) to synthesize completely-defined, BPDE-modified oligonucleotides for chemical and physical studies of covalent complexes. We will analyze covalent adduct formation between the syn-BPDEs and DNA. We will determine the reaction mechanisms for binding BPDEs to dAdo and dCyd binding sites in synthetic and naturally occurring polynucleotides. We will synthesize BPDE- modified oligonucleotides, utilizing all four isomers of the carcinogen. The hydrocarbons will be specifically attached to dGuo, dAdo or dCyd sites. These synthetic molecules will be characterized by spectroscopic and sequencing techniques. These site-specific, carcinogen-modified oligonucleotides will be employed in conformational studies. The change in conformation will be assessed for adducts located at different bases and in different sequences. The physical and chemical properties of these modified oligonucleotides will be defined by fluorescence, CD, NMR, and mass spectroscopies and X-ray crystallographic techniques. Physical and chemical properties of the defined lesions will be correlated with the biological properties of these environmentally important polycyclic aromatic hydrocarbons.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Chemical Pathology Study Section (CPA)
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University of California San Francisco
Schools of Pharmacy
San Francisco
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Wolfe, Alan R; Smith, Timothy J; Meehan, Thomas (2004) Benzo[a]pyrene diol epoxide forms covalent adducts with deoxycytidylic acid by alkylation at both exocyclic amino N(4) and ring imino N-3 positions. Chem Res Toxicol 17:476-91
Vock, E H; Wolfe, A R; Meehan, T (2001) Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin. Mutat Res 478:199-206
Song, Q; Negrete, G R; Wolfe, A R et al. (1998) Synthesis and characterization of bay region halohydrins derived from Benzo[a]pyrene diol epoxide and their role as intermediates in halide-catalyzed cis adduct formation. Chem Res Toxicol 11:1057-66
Meehan, T; Wolfe, A R; Negrete, G R et al. (1997) Benzo[a]pyrene diol epoxide-DNA cis adduct formation through a trans chlorohydrin intermediate. Proc Natl Acad Sci U S A 94:1749-54
Wolfe, A R; Meehan, T (1994) The effect of sodium ion concentration on intrastrand base-pairing in single-stranded DNA. Nucleic Acids Res 22:3147-50
Wolfe, A R; Yamamoto, J; Meehan, T (1994) Chloride ions catalyze the formation of cis adducts in the binding of anti-benzo[a]pyrene diol epoxide to nucleic acids. Proc Natl Acad Sci U S A 91:1371-5
Wolfe, A R; Meehan, T (1992) Use of binding site neighbor-effect parameters to evaluate the interactions between adjacent ligands on a linear lattice. Effects on ligand-lattice association. J Mol Biol 223:1063-87
Yamamoto, J; Subramaniam, R; Wolfe, A R et al. (1990) The formation of covalent adducts between benzo[a]pyrenediol epoxide and RNA: structural analysis by mass spectrometry. Biochemistry 29:3966-72
Shimer Jr, G H; Wolfe, A R; Meehan, T (1988) Equilibrium binding of benzo[a]pyrene tetrol to synthetic polynucleotides: sequence selectivity, thermodynamic properties, and ionic strength dependence. Biochemistry 27:7960-6
Wolfe, A; Shimer Jr, G H; Meehan, T (1987) Polycyclic aromatic hydrocarbons physically intercalate into duplex regions of denatured DNA. Biochemistry 26:6392-6

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