Aromatic Amine-DNA Lesions: Mutagenicity and Repair

描述（由申请人提供）：多环芳香族胺、杂环胺和硝基arenes是存在于许多煮熟和烤熟食品中的环境致癌物，特别是肉类、燃料燃烧产物，如柴油废气、烟草烟雾、烹饪油烟、咖啡、茶和香料，以及被污染的空气和水。当这些化学物质的代谢物形成DNA损伤导致复制过程中的突变时，癌症就开始了。在众多的DNA加合物中，为了生物监测和评估个人对环境致癌物的暴露风险，确定最危险的DNA加合物是至关重要的。通过专注于那些在体内最持久的加合物，生物监测将得到极大的改善。我们专注于一组芳香胺、杂环胺和硝基芳烃衍生的不同大小和形状的DNA加合物，这些加合物源于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发现。我们将研究脱氧核糖核酸（dG-N2）的DNA加合物，这在很大程度上被忽视了，但在动物研究中经常持续存在，以及脱氧核糖核酸（dG-C8）的加合物，动物研究表明，在许多情况下，脱氧核糖核酸（dG-C8）具有修复易感性。我们的中心假设是，那些完全逃避核苷酸切除修复（NER）的加合物是关键的加合物，因为它们将逐渐积聚在我们的DNA中并导致致癌突变。我们的长期目标是确定控制修复抗性和易感性的加合物的性质，并确定那些抵抗NER的加合物。我们的三个具体目标验证了鸟嘌呤的连锁位点、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易感性的关键因素的假设。我们将利用创新的分子建模方法来阐明DNA损伤的特性，并确定修复抵抗或易感性的特征。我们将与长期合作伙伴N. Geacintov携手合作，他将对我们的加合物进行人类HeLa细胞提取物的NER研究。我们的基本假设是，病变诱导的DNA双链的局部稳定是决定给定病变的NER抗性的基本特性。先前的工作已经证明，使用双链化合物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降低，要么稳定修饰的双链DNA。相反，引发NER的DNA损伤是热不稳定的。我们将研究未络合DNA中的加合物以及与核小体中的组蛋白络合时的加合物，核小体是细胞环境中基本的DNA组织单位。我们的研究将提供下一代暴露和癌症风险的生物标志物，通过我们对NER机制的理解，促进设计更好的NER耐药化疗药物，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的基因毒性筛选能力。

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.