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

外来物质(异物)附着在DNA上形成共价DNA加合物(加成产物)可能会诱导突变导致癌症形成，或促进细胞死亡，阻止或逆转致癌过程。已知许多天然产物和化学致癌物通过代谢形成活性自由基物种，这些自由基物种共价连接到嘌呤(脱氧鸟苷(DG)和脱氧腺苷(DA))的C8位，形成C8-芳基(Ar)-嘌呤加合物。虽然C8-Ar-嘌呤加合物预计会引发突变、癌症形成和细胞死亡，但人们对它们的化学和生化性质知之甚少。这种知识的缺乏限制了我们预测这些加合物将如何导致人类疾病的能力。因此，这个由NSERC资助的项目的目标是填补我们对C8-Ar-嘌呤加合物形成后果的了解的这一空白。在我们研究计划的这一阶段，我们表征了它们对双链DNA结构、DNA复制的影响，并开始评估它们的化学反应活性。我们已经建立了将C8-Ar-嘌呤加合物结合到DNA中的合成策略。利用光学光谱来确定它们对双链DNA稳定性和结构的影响。该项目的这一方面包括使用C8-Ar-嘌呤加合物作为分子传感器和氧化还原活性碱基，作为双链DNA中进一步氧化的优先目标。还提出了利用DNA聚合酶的聚丙烯酰胺凝胶电泳法(PAGE)进行引物延伸研究，以测量C8-Ar-嘌呤加合物相对核苷酸的插入和从3‘-末端的链延伸。由于加合物修饰的DNA的复制涉及DNA聚合酶，这些研究将开始评估C8-AR-嘌呤加合物的生物影响，这将对化学、生物和医学研究人员具有广泛的科学价值。

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.