Toxicity and Biosensing Properties of C8-Aryl-Deoxyguanosine Adducts

亲电试剂对DNA的共价修饰是化学致癌的第一步。 如果这些修饰不被修复，它们会损害DNA复制的保真度，导致突变和可能的癌症。 一些修饰的DNA碱基也发挥有益的作用，并作为治疗剂和传感器来检测光，pH值或金属离子。 某些单链DNA寡核苷酸还充当称为适体的核酸配体，其以高亲和力和特异性结合分子靶标，如蛋白质和小分子。用添加化学多样性的修饰碱基替换正常核碱基可以增强适体对其分子靶标的亲和力。在这个NSERC资助的研究项目中，我们的重点是在C8位点被芳基残基修饰的2 '-脱氧鸟苷（dG）。该资助的第1部分侧重于DNA底物中C8-芳基-dG加合物的毒理学。 关于它们的毒理学性质（致突变性）知之甚少，因此设计实验来表征DNA聚合酶如何处理C8-芳基-dG加合物。 C8-芳基-dG加合物也易于进一步氧化过程，其可导致DNA交联形成。 DNA交联可以杀死细胞，并且是许多抗癌剂的治疗基础。 实验将确定C8-芳基-dG加合物在DNA的螺旋环境中的氧化反应性，以表征这些损伤诱导DNA交联形成的潜力。 该资助的第2部分考察了各种适体结构中C8-芳基-dG加合物的生物传感特性。 我们的目标是将C8-芳基-dG加合物掺入适体中以增强适体与分子靶标的结合亲和力，并在靶标与修饰的适体结合时提供荧光信号。 适体在医学和农业中具有广泛的应用，生物技术公司现在专门从事适体的合成和设计。 扩展DNA的化学性质用于体外选择可以增强靶结合并允许选择更广泛的靶。在靶结合时促进和提供开启发射的化学多样的C8-芳基-dG加合物将是非常有用的。

Covalent modification of DNA by electrophiles is an initial step in chemical carcinogenesis. If these modifications are not repaired, they compromise the fidelity of DNA replication, leading to mutations and possibly cancer. Some modified DNA bases also play beneficial roles and serve as therapeutics, and sensors to detect light, pH or metal ions. Certain single-strand DNA oligonucleotides also act as nucleic acid ligands called aptamers that bind to molecular targets, such as proteins and small molecules, with high affinity and specificity. Replacement of the normal nucleobases with modified bases that add chemical diversity can enhance aptamer affinity for its molecular target. In this NSERC-funded research program our focus is on 2'-deoxyguanosine (dG) that has been modified at the C8-site by aryl residues. Part 1 of this grant focuses on the toxicology of C8-aryl-dG adducts in DNA substrates. Little is known about their toxicological properties (mutagenicity) and so experiments are designed to characterize how DNA polymerase enzymes process C8-aryl-dG adducts. C8-aryl-dG adducts are also prone to further oxidative processes that can lead to DNA cross-link formation. DNA cross-links can kill cells and are a therapeutic basis for many anticancer agents. Experiments will determine the oxidative reactivity of C8-aryl-dG adducts in the helical environment of DNA to characterize the potential of these lesions to induce DNA cross-link formation. Part 2 of this grant examines the biosensing properties of C8-aryl-dG adducts in various aptamer structures. Our goal is to incorporate C8-aryl-dG adducts into aptamers to enhance aptamer binding affinity to the molecular target and provide a fluorescent signal when the target binds to the modified aptamer. Aptamers have a wide range of applications in medicine and agriculture with biotechnology companies now specializing in aptamer synthesis and design. Expanding the chemistry of DNA for in vitro selection can enhance target binding and permit a wider range of targets to be selected. Chemically diverse C8-aryl-dG adducts that promote and provide turn-on emission upon target binding would be highly useful.