Y-family DNA polymerases and cellular responses to benzo[a]pyrene

描述（由申请人提供）：最近的进展表明，在高等真核细胞中，环境致癌物诱导的几乎所有突变的产生中都涉及易错DNA聚合酶。这些数据支持了基于这些蛋白质活性的选择性调节的癌症化学预防的前景，基于降低突变频率将降低癌症发病率的假设。然而，使用新开发的小鼠模型（其中这些聚合酶中的一种或另一种缺乏）进行的致癌研究产生了意想不到的结果。具体而言，个别聚合酶的缺陷可能导致在突变频率降低的情况下癌症发病率大大提高。这一意外的结果与致癌的体细胞突变假说不一致，并突出了这样一个事实，即我们对聚合酶的细胞功能的认识存在重大差距。这些研究是用紫外线辐射进行的，这些酶在化学诱变剂引起的诱变和致癌作用中的作用在很大程度上尚未探索。本申请提出检验这样的假设，即由环境致癌物苯并[a]芘（即BPDE）的活化形式在DNA中诱导的致突变跨损伤合成过去的加合物依赖于Y家族DNA聚合酶eta和/或iota。这将在三个特定目的中进行检查：目的1，确定BPDE诱导的成纤维细胞内源性hprt基因突变的频率和谱，所述成纤维细胞来源于切除修复缺陷小鼠的同基因品系，所述小鼠为野生型或pol、eta和/或iota组合缺陷。目的2，研究聚合酶缺乏对BPDE诱导的细胞周期检查点、细胞凋亡和基因表达的影响。目的3、研究B[a]P诱导的同基因、聚合酶缺陷小鼠肺腺瘤/腺癌的发生率和多样性。这项提案将填补我们对癌症如何由常见环境致癌物引发的知识的关键空白。这项工作的公共卫生意义是，化学致癌物诱导的突变与癌症，特别是肺癌的发展有关。这项研究的最终目标是了解这些化学物质是如何导致癌症的，以便设计预防这种疾病的策略。

DESCRIPTION (provided by applicant): Recent advances implicate error-prone DNA polymerases in the generation of virtually all mutations induced by environmental carcinogens in higher eukaryotic cells. These data have supported the promise of cancer chemoprevention based on the selective modulation of the activity of these proteins, based on the assumption that reducing the mutant frequency will reduce the incidence of cancer. However, carcinogenesis studies using newly-developed mouse models in which one or another of these polymerases is deficient have yielded unexpected results. Specifically, deficiency in individual polymerases may result in greatly enhanced cancer incidence in the face of reduced mutation frequencies. This unexpected result is not consistent with the somatic mutation hypothesis of carcinogenesis, and highlights the fact that there are critical gaps in our knowledge of the cellular function of this universe of polymerases. These studies have been done with ultraviolet radiation, and the role of these enzymes in mutagenesis and carcinogenesis by chemical mutagens remains largely unexplored. This application proposes to examine the hypothesis that mutagenic translesion synthesis past adducts induced in DNA by the activated form of the environmental carcinogen benzo[a]pyrene (i.e. BPDE) is dependent on the Y-family DNA polymerases eta and/or iota. This will be examined in three Specific Aims: Aim 1, To determine the frequency and spectrum of mutations induced by BPDE in the endogenous hprt gene of fibroblasts derived from isogenic strains of excision repair-deficient mice that are wild-type or combinatorially deficient in pol, eta, and/or iota. Aim 2, To examine the effect of polymerase deficiency on BPDE-induced cell cycle checkpoints, apoptosis and gene expression in these same cells. Aim 3, To examine the incidence and multiplicity of lung adenomas/adenocarcinomas induced by B[a]P in the isogenic, polymerase-deficient mice. This proposal will fill critical gaps in our knowledge of how cancer is initiated by a common environmental carcinogen. The public health implication of this work is that mutations induced by chemical carcinogens are implicated in the development of cancer, particularly lung cancer. The ultimate goal of this research is to understand how these chemicals cause cancer in order to design strategies to prevent the disease.