Aromatic Amine-DNA Lesions: Mutagenicity and Repair

说明(申请人提供)：多环芳胺、杂环胺和硝基芳烃是许多烹调和烧烤食品中存在的环境致癌物质，特别是肉类、燃料燃烧的产物，如柴油废气、烟草烟雾、烹饪油烟、咖啡、茶和香料，以及受污染的空气和水。当这些化学物质的代谢物形成DNA损伤，在复制过程中导致突变时，癌症就会发生。在过多的DNA加合物中，识别最危险的加合物对于生物监测和评估个人暴露于环境致癌物的风险至关重要。通过集中于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，这些加合物源于这些代谢激活的环境致癌物。已经在人类细胞和体液以及动物细胞和组织中发现了它们。我们将研究DG-N2的DNA加合物，这些DNA加合物在很大程度上被忽视，但在动物研究中经常是持久的，以及DG-C8的加合物，动物研究表明，在一些情况下，修复易感性。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，因为它们将逐渐积累在我们的DNA中，并导致致癌突变。我们的长期目标是确定支配修复抵抗和易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验证了这一假设，即鸟嘌呤的连接位置、芳环体系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模拟方法来阐明DNA损伤的属性，并确定与修复抵抗或敏感性有关的特征。我们将与我们的长期合作伙伴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抵抗的基本属性。以前的工作已经证明，使用双链的熔点作为稳定性的指示剂，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，引发NER的DNA损伤在温度上是不稳定的。我们将研究未复合DNA中的加合物，以及与核小体中的组蛋白复合时的加合物，核小体是细胞环境中基本的DNA组织单位。我们的研究将提供暴露和癌症风险的下一代生物标志物，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胺、杂环胺和硝基芳烃衍生的加合物进行基因毒性筛选的能力。

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.