Carcinogen-DNA Adducts: Topology, Conformation and Repair (Renewal)

一类非平面、扭曲的多环芳烃(PAHs)，称为峡区 化合物，是极强的致癌物质；它们包括最近被引用的二苯并[a，L]芘 是目前发现的致瘤性最强的PAH。这些污染物以燃烧的形式排放到环境中。 各种燃料的产品，它们污染粮食作物。它们的生物活性处于最低水平 浓缩物存在于食物和城市空气中，对广大人群有害。中国古代文化的起源 峡湾多环芳烃的非凡致癌能力仍不清楚。然而，它最近被展示出来 它们在代谢活化后产生的几个笨重的DNA加合物是二醇环氧化物 抵抗核苷酸切除修复(NER)，这是抵御此类DNA损伤的主要细胞防御系统。 对这些加合物的DNA修复的抵抗被认为是肿瘤非凡致瘤性的关键原因 母体化学物质，因为它们会导致引发癌症的突变。然而，每个环境峡湾 多环芳烃产生一种立体异构体鸟嘌呤和腺嘌呤DNA加合物的复杂混合物。此外， 每种加合物的NER敏感性可能因DNA碱基序列不同而不同。在如此众多的损害中，关键是 导致癌症的修复耐药基因仍未确定。我们广泛而长期的目标是，在 与我们的实验合作者N.Geacintov教授合作，鉴定耐NER的加合物及其 使用创新和最先进的建模方法的特征：我们假设NER阻力是 由多环芳烃修饰的DNA的结构、动力学和热力学性质决定。峡湾多环芳烃 被选中进行详细研究的是二苯并[a，L]芘，苯并[g]黄原烯和苯并[c]菲；我们 研究它们通过已建立的二醇环氧化物代谢活化途径产生的加合物。这些 多环芳烃分别代表6、5和4环的芳香族体系，这一范围最适合诱导肿瘤。 我们的目标是研究我们选择的序列中三个母体多环芳烃的许多二元醇环氧化物加合物 假设将改变他们对NER的敏感性。我们的进一步目标是确定特征属性和 当在核小体的组蛋白环境中组织时，病变的NER敏感性 细胞环境中染色质结构的基本单位。这是向澄清的关键的第一步 染色质背景下复杂的NER机制的功能。我们将与我们的 实验合作者N.Geacintov教授：NER数据与人类细胞提取液，包括病变- 包含核小体将为我们的发现与实验直接联系提供锚 观察，我们的分析将指向重要的预测，这些预测将在他的实验室中进行测试。我们的 研究将提供暴露于多环芳烃的下一代生物标志物，促进更好的NER- 通过我们对NER机制的了解，获得耐药化疗药物，并促进我们的 对环境中存在的多环芳烃衍生的加合物进行遗传毒性筛选的能力。

A category of non-planar, twisted polycyclic aromatic hydrocarbons (PAHs), termed fjord region compounds, are extremely potent tumorigens; they include dibenzo[a,l]pyrene which has recently been cited as the most tumorigenic PAH yet identified. These pollutants are released into the environment as combustion products of a variety of fuels, and they contaminate food crops. They are biologically active at the low concentrations present in foods and urban air and are hazardous to the population at large. The origin of the extraordinary carcinogenic potencies of fjord PAHs remains unknown. However, it has recently been shown that several of the bulky DNA adducts that they produce after metabolic activation to diol epoxides, are resistant to nucleotide excision repair (NER), the principal cellular defense against such DNA lesions. Resistance to DNA repair of these adducts is deemed a critical cause for the extraordinary tumorigenicity of the parent chemicals, as they cause the mutations which initiate cancer. However, each environmental fjord PAH gives rise to a complex mixture of stereoisomeric guanine and adenine DNA adducts. Furthermore, the NER susceptibility of each such adduct may vary with DNA base sequence. In this multitude of lesions, the key repair-resistant ones that lead to cancer remain unidentified. Our broad, long-term objective is, working in tandem with our experimental collaborator Prof. N. Geacintov, to identify the NER-resistant adducts and their characteristics using innovative and state-of-the-art modeling methods: we hypothesize that NER-resistance is governed by the structural, dynamic and thermodynamic properties of the PAH-modified DNA. The fjord PAHs selected for detailed study are dibenzo[a,l]pyrene, benzo[g]chrysene, and benzo[c]phenanthrene; we investigate their adducts produced via the well established diol epoxide metabolic activation pathway. These PAHs represent aromatic systems of 6, 5, and 4 rings, respectively, a range optimal for the induction of tumors. We aim to investigate the many diol epoxide adducts of the three parent PAHs in selected sequences that we hypothesize will alter their NER-susceptibilities. We further aim to determine the characteristic properties and NER susceptibilities of lesions when organized within the histone protein environment of the nucleosome, the basic unit of chromatin structure in the cellular environment. This is an essential first step towards elucidating the functioning of the complex NER machinery in the context of chromatin. We will work hand-in-hand with our experimental collaborator Prof. N. Geacintov: NER data with human cell extracts and including lesion- containing nucleosomes will provide anchors for directly linking our findings with the experimental observations, and our analyses will point to important predictions that will be tested in his laboratory. Our studies will provide the next-generation of biomarkers for PAH exposure, 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 PAHs present in our environment.