Impact of PAH-DNA Lesions on DNA Repair and Replication

人类暴露于各种环境致癌污染物， 包括化石燃料燃烧产物和香烟烟雾中物质。拜州 苯并[a]芘（B[a]P）是一类潜在致癌物质的最知名代表。 多环芳烃（PAH）。与其他PAH物质一样，B[a]P是 代谢活化为与DNA反应的高反应性和致突变性B[a]P二醛环氧化物 形成加合物。低效率的DNA修复和跨损伤合成的DNA加合物催化 聚合酶，特别是最近发现的旁路聚合酶，是决定是否存在聚合酶的关键因素。 巨大的病变会引起突变并最终导致癌症。然而，这些的分子基础 生物学上重要的现象仍然知之甚少。该项目的主要目标是 阐明（1）人类DNA修复酶识别和切除大体积DNA的机制 加合物，如衍生自B[a]P二醇环氧化物的那些，和（2）分子结构因子， 涉及由代表性旁路聚合酶（Dpo 4， pol _和pol_q）。这些问题是解决使用定义明确的DNA序列与网站- 由B[a]P二醇环氧化物与环外氨基结合而产生的特异性结合损伤 DNA中的腺嘌呤（dA）和鸟嘌呤（dG）。具体目标一。确定DNA结构因子 以及引起立体化学上的有效或无效的核粒切除修复的构象。 使用可变碱基序列背景作为工具来调节定义的B[a]P-dG和B[a]P-dA病变 DNA的局部结构特性。具体目标2。确定并比较差异， 参与大体积B[a]P-dG和B[a]P-dA跨病变旁路保真度和效率的机制 通过Y家族旁路聚合酶在不同碱基序列背景下的损伤。现代计算和 基于NMR结构研究的建模技术将被用来深入了解加合物 构象性质和特定的DNA扭曲附近的加合物，作为 通过核苷酸切除修复蛋白识别和去除损伤的信号。分子 采用动态模拟方法研究碱基序列和加合物 立体化学依赖性跨病变旁路术 已知调节跨损伤合成的背景。

The human population is exposed to a variety of environmental cancer-causing pollutants that include fossil fuel combustion products and substances in cigarette smoke. The bay region benzo[a]pyrene (B[a]P) is the best known representative of a class of potentially carcinogenic compounds, the polycyclic aromatic hydrocarbons (PAH). Like other PAH substances, B[a]P is metabolically activated to highly reactive and mutagenic B[a]P dial epoxides that react with DNA forming adducts. Inefficient DNA repair and translesion synthesis of DNA adducts catalyzed by polymerases, especially the recently discovered bypass polymerases, are key factors that determine if a buky lesion can give rise to mutations and ultimately to cancer. However, the molecular bases of these biologically important phenomena are still poorly understood. The major objectives of this project are to elucidate (1) the mechanisms by which human DNA repair enzymes recognize and excise bulky DNA adducts such as those derived from B[a]P diol epoxides, and (2) the molecular-structural factors and mechanisms involved in translesion synthesis catalyzed by representative bypass polymerases (Dpo4, pol _, and pol q) in vitro. These questions are addressed using well defined DNA sequences with site- specifically incorporated lesions derived from the binding of B[a]P diol epoxides to the exocyclic amino groups of adenine (dA) and guanine (dG) in DNA. Specific Aim I. Determine the DNA structural factors and adcluct conformations that cause efficient or inefficient nucleoticle excision repair of stereochemically defined B[a]P-dG and B[a]P-dA lesions employing variable base sequence context as a tool to modulate the local structural properties of the DNA. Specific Aim 2. Determine and compare the differences and mechanisms involved in the fidelity and efficiency of translesion bypass of bulky B[a]P-dG and B[a]P-dA lesions in different base sequence contexts by Y family bypass polymerases. Modern computational and modeling techniques, based on NMR structural studies, will be employed to derive insights into adduct conformational properties and specific DNA distortions in the vicinity of the adducts that serve as signals of recognition and removal of the lesions by nucleotide excision repair proteins. Molecular dynamic simulation methods will be employed to investigate base sequence and adduct stereochemistry-dependent translesion bypass with the lesions positioned in different base sequence contexts that are known to modulate translesion synthesis.