Chemical and biochemical properties of C8-Aryl-Purine DNA adducts

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Attachment of a foreign substance (xenobiotic) to DNA to form a covalent DNA adduct (addition product) may induce mutations causing cancer formation, or facilitate cell death and block or reverse the carcinogenic process. A number of natural products and chemical carcinogens are known to undergo metabolism to form reactive radical species that attach covalently to the C8-site of purine (deoxyguanosine (dG) and deoxyadenosine (dA)) bases to form C8-aryl(Ar)-purine adducts. While C8-Ar-purine adducts are expected to initiate mutations, cancer formation and cell death, very little is known about their chemical and biochemical properties. This lack of knowledge limits our ability to predict how these adducts will contribute to human disease. Thus, the goal of this NSERC-funded project is to fill this gap in our understanding of the consequences of C8-Ar-purine adduct formation. In this phase of our research program we characterize their impact on duplex DNA structure, DNA replication and begin to assess their chemical reactivity. We have established synthetic strategies for the site-specific incorporation of C8-Ar-purine adducts into DNA. Optical spectroscopies are utilized to determine their impact on duplex DNA stability and structure. Included in this aspect of the project is the use of C8-Ar-purine adducts as molecular sensors and as redox-active nucleobases that act as preferential targets of further oxidation within duplex DNA. Primer extension studies utilizing polyacrylamide gel electrophoresis (PAGE) with DNA polymerases to measure insertion of nucleotides opposite a C8-Ar-purine adduct and chain extension from the 3'-terminus are also proposed. As the replication of adduct-modified DNA involves DNA polymerases, these studies will begin to assess the biological impact of C8-Ar-purine adducts, which will be of broad scientific value to researchers in chemistry, biology and medicine.