DNA Lesion Structures: Mutagenicity and Repair

描述（由申请人提供）：本研究的广泛和长期目标是在分子水平上确定 DNA 损伤引发癌症的病因，而 DNA 损伤是由人类广泛接触的环境和内源性化学物质产生的。总体假设是：（1）受损DNA的具体形成对于决定其是否被修复至关重要； (2) 如果修复失败，复制聚合酶内的 DNA 构象决定是否发生阻塞、正常或诱变旁路； (3)如果正常复制受到阻碍，则改变的DNA将遇到一种或多种旁路聚合酶，改变的DNA的特定构象将决定是否发生可能引发癌症的突变。 PI 将通过确定两组损伤的结构、动态和热力学特性来测试这些假设：(1) 一系列源自致癌芳香胺/酰胺的系列，呈现烟草烟雾、汽车尾气和熟食，能够进行沃森-克里克配对和堆叠；(2) 严重扭曲的组，无法进行沃森-克里克配对，堆叠受损；其中包括由一种著名的激素替代药物引起的病变，以及由内源性和外源性活性氧产生的病变。具体目标 1 将确定双链 DNA 损伤的详细结构和热力学特性，作为加合物结构和导致加合物阻碍复制聚合酶的热力学因素的函数，并描述可能允许突变或正常绕过损伤的因素，而 Y 家族旁路聚合酶的保真度降低。与公共卫生的相关性：这项工作将在分子水平上精确定义源自致癌环境物质的含 DNA 病变的具体结构和能量特征，从而提供区分非常有害的化学物质和良性化学物质的分子标志。这些研究将促进致癌物损伤 DNA 生物监测的进展，因为 DNA 损伤的结构和热力学特性将提供一种区分高基因毒性损伤和良性损伤的方法。

DESCRIPTION (provided by applicant): The broad and long term goals of this research is to determine on a molecular level the etiology of cancer initiation by DNA damage, produced by environmental and endogenous chemicals to which the human population is widely exposed. The overall hypotheses are: (1) The specific formation of damaged DNA is critical in determining if it is repaired or not; (2) if repair fails, the DNA conformation within a replicative polymerase determines whether blockage, normal or mutagenic bypass occurs; (3) if normal replication is impeded, then the altered DNA will encounter one or more bypass polymerases, and the specific conformation of the altered DNA will determine whether a mutation which may initiate cancer occurs. The PI will test these hypotheses by determining structural, dynamic and thermodynamic properties for two groups of lesions: (1) a series derived from carcinogenic aromatic amines/amide presenting tobacco smoke, automobile exhaust and cooked foods that are capable of Watson-Crick pairing and stacking, and (2) a severely distorting group incapable of Watson-Crick pairing, with impaired stacking; these include a lesion derived from a prominent hormone replacement drug, and one produced by endogenous and exogenous reactive oxygen species. Specific aim 1 will determine detailed structural and thermodynamic properties of the lesions in duplex DNA as a function of adduct structure and thermodynamic factors that cause the adducts to impede replicative polymerases, and to delineate factors which could permit mutagenic or normal bypass of the lesions with lowered fidelity in Y-family bypass polymerases. Relevance to public health: this work will define precisely on a molecular level, the specific structural and energetic characteristics of DNA-containing lesions derived from carcinogenic environmental substances, and thus provided the molecular hallmarks that distinguish very harmful chemicals from benign ones. These studies will facilitate advances in biomonitoring of carcinogen - damaged DNA, since the structural and thermodynamic properties of the DNA lesions would provide a method for distinguishing highly genotoxic lesions from more benign ones.