Aromatic Amine-DNA Lesions: Mutagenicity and Repair

描述（由申请人提供）：多环芳香胺、杂环胺和硝基芳烃是环境致癌物，存在于许多熟食和烧烤食品中，特别是肉类、燃料燃烧产物（如柴油机尾气、烟草烟雾、烹饪油烟、咖啡、茶和香料）以及污染的空气和水。当这些化学物质的代谢物形成 DNA 损伤并在复制过程中引起突变时，就会引发癌症。在众多的 DNA 加合物中，为了生物监测和评估个人接触环境致癌物的风险，必须确定最危险的加合物。通过关注那些体内最持久的加合物，生物监测将得到极大的改善。我们专注于一组不同大小和形状的芳香胺、杂环胺和硝基芳烃衍生的 DNA 加合物，这些加合物源自这些代谢激活的环境致癌物。它们已在人体细胞和体液以及动物细胞和组织中被鉴定出来。我们将研究 dG-N2 的 DNA 加合物，这些加合物在很大程度上被忽视，但在动物研究中经常持续存在，以及 dG-C8 的加合物，动物研究表明在许多情况下具有修复敏感性。我们的中心假设是，那些完全逃脱核苷酸切除修复（NER）的加合物是关键的，因为它们会逐渐在我们的 DNA 中积累并导致癌症引发的突变。我们的长期目标是确定控制修复阻力和敏感性的加合物的性质，并识别那些抵抗 NER 的加合物。我们的三个具体目标测试了以下假设：鸟嘌呤的连接位点、芳香环系统的大小和形状以及加合物的序列背景是决定其 NER 敏感性的关键因素。我们将利用创新的分子建模方法来阐明 DNA 损伤的特性，并确定导致修复抵抗性或敏感性的特征。我们将与我们的长期合作者 N. Geacintov 携手合作，他将使用人类 HeLa 细胞提取物对我们的加合物进行 NER 研究。我们的基本假设是，损伤引起的 DNA 双链体局部稳定是决定给定损伤的 NER 抗性的基本特性。先前的工作已经证明，使用双链体的熔点作为稳定性指标，修复抗性加合物要么导致轻微的稳定性下降，要么稳定修饰的双链 DNA。相比之下，引起 NER 的 DNA 损伤是热不稳定的。我们将研究未复合 DNA 中的加合物以及与核小体（细胞环境中基本 DNA 组织单位）中的组蛋白复合时的加合物。我们的研究将提供下一代暴露和患癌症风险的生物标志物，通过我们对 NER 机制的了解，促进更好的 NER 耐药化疗药物的设计，并提高我们对环境中存在的多环芳香胺、杂环胺和硝基芳烃衍生的加合物进行基因毒性筛查的能力。

DESCRIPTION (provided by applicant): Polycyclic aromatic amines, heterocylic amines and nitroarenes are environmental carcinogens that are present in many cooked and broiled foods, notably meats, products of fuel combustion such as diesel exhaust, tobacco smoke, cooking oil fumes, coffee, tea and spices, and polluted air and water. Cancer is initiated when metabolites of these chemicals form DNA lesions that cause mutations during replication. Among the plethora of DNA adducts, it is essential to identify the most hazardous ones for purposes of biomonitoring and assessing the exposure risk of individuals to environmental carcinogens. Biomonitoring will be greatly improved by concentrating on those adducts that are the most persistent ones in vivo. We are focusing on a group of aromatic amine-, heterocyclic amine- and nitroarene-derived DNA adducts of varying sizes and shapes that stem from these metabolically activated environmental carcinogens. They have been identified in human cells and fluids, and in animal cells and tissues. We will investigate DNA adducts to dG-N2 that have been largely overlooked, but are often persistent in animal studies and adducts to dG-C8, for which animal studies suggest repair susceptibility in a number of cases. Our central hypothesis is that those adducts that entirely escape nucleotide excision repair (NER) are critical ones, as they will gradually accumulate in our DNA and cause cancer-initiating mutations. Our long-term goal is to determine the properties of adducts that govern repair resistance and susceptibility, and identify those adducts that resist NER. Our three Specific Aims test the hypothesis that the linkage site to guanine, the size and shape of the aromatic ring system and the sequence context of the adducts are the key factors that determine their NER susceptibility. We will utilize innovative molecular modeling approaches to elucidate the properties of the DNA lesions and determine the characteristics responsible for repair resistance or susceptibility. We will work hand-in-hand with our long-term collaborator N. Geacintov, who will perform NER studies with human HeLa cell extracts for our adducts. Our underlying hypothesis is that lesion-induced local stabilization of the DNA duplexes is the fundamental property that determines the NER resistance of a given lesion. Prior work has demonstrated, using melting points of duplexes as indicators of stability, that repair resistant adducts either cause minor stability decreases or stabilize modified double-stranded DNA. In contrast, DNA lesions that elicit NER are thermally destabilizing. We will investigate the adducts in uncomplexed DNA as well as when complexed with histone proteins in nucleosomes, the fundamental DNA-organization unit in the cellular environment. Our studies will provide the next-generation of biomarkers for exposure and risk of developing cancer, facilitate design of better NER-resistant chemotherapeutics through our gained understanding of NER mechanisms, and advance our capability for genotoxic screening of adducts derived from the polycyclic aromatic amines, heterocylic amines and nitroarenes present in our environment.