Toxicity and Biosensing Properties of C8-Aryl-Deoxyguanosine Adducts

亲电体对DNA的共价修饰是化学致癌的第一步。如果不修复这些修饰，它们会损害DNA复制的保真度，导致突变，甚至可能导致癌症。一些修饰的DNA碱基也起到了有益的作用，可以用作治疗药物，以及检测光线、pH或金属离子的传感器。某些单链DNA寡核苷酸还充当核酸配体，称为适体，与蛋白质和小分子等分子靶标结合，具有很高的亲和力和特异性。用增加化学多样性的修饰碱基取代正常的碱基可以提高适体对其分子靶标的亲和力。在这个由NSERC资助的研究计划中，我们的重点是2‘-脱氧鸟苷(DG)，它在C8位被芳基残基修饰。这笔赠款的第一部分侧重于DNA底物中C8-芳基-DG加合物的毒理学。人们对它们的毒理学特性(致突变性)知之甚少，因此设计了实验来表征DNA聚合酶如何处理C8-芳基-DG加合物。C8-芳基-DG加合物也容易发生进一步的氧化过程，从而导致DNA交联的形成。DNA交联物可以杀死细胞，是许多抗癌药物的治疗基础。实验将确定C8-芳基-DG加合物在DNA螺旋环境中的氧化反应活性，以表征这些损伤诱导DNA交联形成的可能性。这项资助的第二部分考察了C8-芳基-DG加合物在各种适配子结构中的生物传感特性。我们的目标是将C8-芳基-DG加合物引入适体，以增强适体与分子靶标的结合亲和力，并在靶标与修饰适体结合时提供荧光信号。适配子在医药和农业中有广泛的应用，生物技术公司现在专门从事适配子的合成和设计。扩大DNA的化学成分用于体外选择可以增强靶标结合，并允许更广泛的靶标选择。化学上不同的C8-芳基-DG加合物在靶结合时促进和提供开启发射将是非常有用的。

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.