A Novel Role for the Fanconi Anemia Pathway in Replication of B[a]P-Adducted DNA

描述(由申请人提供)：这项建议的广泛长期目标是阐明Fanconi贫血(FA)途径在保护细胞免受苯并[a]芘(B[a]P)诱导的DNA损伤的致癌效应中的作用。苯并[a]磷是一种含量丰富且普遍存在的环境致癌物，可在细胞内代谢生成苯并[a]芘二氢二醇环氧化物(BPDE)。BPDE诱导的DNA损伤触发依赖于Rad18(一种E3连接酶)的增殖细胞核抗原的单一泛素化和专门的DNA聚合酶Pol kappa向复制分叉的招募。与复制DNA聚合酶在DNA损伤部位停滞不前不同，Pol kappa可以以BPDE加成的DNA为模板进行DNA合成。Pol kappa介导的TLS使细胞能够耐受BPDE加合物的诱变和致死作用，从而有助于基因组的稳定和肿瘤抑制。然而，Pol kappa调控的分子机制(S)还不完全清楚。我们的初步研究表明，Fanconi贫血(FA)蛋白与Rad18和Pol kappa介导的B[a]P病变的TLS密切相关。本研究的具体目的是：(1)确定BPDE诱导FANCD2(FA途径的可能效应因子)与Pol kappa之间相互作用的分子基础。(2)探讨Rad18激活FA通路的机制。(3)检验FA和TLS通路之间的相互依赖关系。目的1将突变Pol kappa中的泛素结合基序，并确定这些突变对FANCD2结合的影响。此外，我们将测试Pol kappa和FA途径相互作用的蛋白Rev1在介导Pol kappa-FANCD2相互作用中的作用。Aim 2将测试Rad18是直接还是通过调节上游FA核心复合体成分来修饰FANCD2。目的3将确定FANC缺乏是否影响BPDE病变的TLS，反之，TLS缺陷是否影响BPDE对FA通路的激活。我们的研究结果将为FA途径与TLS酶协调响应环境B[a]P(可能还有其他遗传毒素)以维持基因组稳定的机制提供一个新的范例。我们的研究可能有助于识别环境中苯并[a]磷诱发疾病的高危个体。此外，我们的工作可能导致癌症治疗的新药物靶点：与B[a]P类似，许多化疗是遗传毒性的，并激活检查点通路。我们已经证明，缺乏Pol kappa或Rad18会使细胞对苯并[a]磷诱导的死亡敏感。潜在地，靶向FA成分、Rad18、Pol kappa或其他TLS酶的小分子可能会使癌细胞对化疗药物的杀伤敏感。与公共健康相关：苯并[a]芘(B[a]P)是一种丰富的环境污染物，它会破坏DNA，从而导致可导致癌症的遗传密码的永久性变化(称为‘突变’)。我们的结果表明，一组被称为Fanconi贫血蛋白(FANCs)的细胞蛋白在防止环境中B[a]P诱导的突变方面发挥了作用。拟议的实验旨在了解FANCs帮助细胞耐受环境诱导的DNA损伤和预防癌症的机制。

DESCRIPTION (provided by applicant): The broad long-term objective of this proposal is to elucidate the role of the Fanconi Anemia (FA) pathway in protecting cells from the carcinogenic effects of Benzo[a]pyrene (B[a]P)-induced DNA damage. B[a]P is an abundant and ubiquitous environmental carcinogen that is metabolized intracellularly to generate Benzo[a]pyrene Di-hydrodiol-Epoxide (BPDE). BPDE-induced DNA damage triggers Rad18 (an E3 ligase)- dependent mono-ubiquitination of PCNA and recruitment of the specialized DNA polymerase Pol kappa to replication forks. In contrast with replicative DNA polymerases which stall at sites of DNA damage, Pol kappa can perform DNA synthesis using BPDE-adducted DNA as a template. Pol kappa-mediated TLS enables cells to tolerate the mutagenic and lethal effects of BPDE adducts, thereby contributing to genomic stability and tumor suppression. However, the molecular mechanism(s) of Pol kappa regulation are incompletely understood. Our preliminary studies suggest that the Fanconi Anemia (FA) proteins are intimately involved in Rad18 and Pol kappa- mediated TLS of B[a]P lesions. The Specific Aims of this proposal are: (1) To determine the molecular basis for BPDE-induced interaction between FANCD2 (the putative effector of the FA pathway) and Pol kappa. (2) To determine the mechanism by which Rad18 activates the FA pathway. (3) To test the interdependence of the FA and TLS pathways. Aim 1 will mutate ubiquitin binding motifs in Pol kappa and determine the effect of these mutations on FANCD2 association. Additionally, we will test the role of the Pol kappa- and FA pathway-interacting protein REV1 in mediating Pol kappa-FANCD2 interactions. Aim 2 will test whether Rad18 modifies FANCD2 directly or via regulation of upstream FA core complex components. Aim 3 will determine whether FANC- deficiency compromises TLS of BPDE lesions and conversely, whether defective TLS affects activation of the FA pathway by BPDE. Results of our studies will provide a novel paradigm for mechanisms by which the FA pathway is coordinated with TLS enzymes in response to environmental B[a]P (and possibly other genotoxins) to maintain genomic stability. Our studies might help identify individuals that are at high-risk for environmental B[a]P-induced disease. Moreover, our work could lead to novel drug targets for cancer therapy: Similar to B[a]P, many chemotherapies are genotoxic and activate checkpoint pathways. We have shown that Pol kappa- or Rad18-deficiency sensitizes cells to B[a]P-induced death. Potentially, small molecules that target FA components, Rad18, Pol kappa, or other TLS enzymes could sensitize cancer cells to killing by chemotherapeutic agents. PUBLIC HEALTH RELEVANCE: Benzo[a]pyrene (B[a]P) is an abundant environmental pollutant that damages DNA thereby causing permanent changes to the genetic code (termed 'mutations') that can result in cancer. Our results suggest that a group of cellular proteins termed the 'Fanconi Anemia' proteins (FANCs) play a role in preventing environmental B[a]P- induced mutations. The proposed experiments aim to understand the mechanisms by which FANCs help cells tolerate the effects of environmentally-induced DNA damage and protect against cancer.