Regulatory Signaling in Repair of Environmentally Induced DNA Damage

描述(申请人提供)：暴露于普遍存在的环境致癌物质，如多环芳烃和紫外线，是人类疾病的原因。人们普遍认为，基因突变是癌症发展过程中的重要一步。很明显，这种突变部分是由容易出错的DNA聚合酶引起的。作为对多种环境基因毒素的响应，真核细胞已经进化出复制受损DNA的替代方法，通过跨损伤合成(TLS)聚合酶，由DNA Pol h、Pol k、Pol I和Rev1组成。TLS聚合酶被招募到停滞的复制分叉上，在那里它们介导复制通过受损的DNA。TLS是复制因暴露于环境致癌物而改变的DNA的中心机制，但TLS本身就是一个容易出错的过程。此外，TLS聚合酶的异常利用极易诱发突变。因此，TLS聚合酶的适当调节和功能是保护基因组完整性的关键机制。本研究将研究环境基因毒素对TLS聚合酶在DNA损伤部位募集的调控机制。特别是，我们将测试这一假设，即Cdc7介导的Rad18的磷酸化促进Rad18-Polh复合体的形成，并有助于绕过太阳紫外线诱导的DNA损伤。此外，我们还将确定Rad18确保在紫外线诱导(Polh)或BPDE诱导(Polk)DNA损伤时选择合适的TLS聚合酶的机制。这些实验将确定TLS聚合酶Rad18和CDC7之间相互作用的意义，并有助于阐明调控TLS聚合酶的机制。我们的研究结果将提供正常复制和损伤诱导复制之间的新联系，并将有助于解释环境遗传毒素如何促进突变。

DESCRIPTION (provided by applicant): Exposure to ubiquitous environmental carcinogens, such as poly aromatic hydrocarbons and UV light, is cause of human disease. It is well accepted that genetic mutations are an important step in the development of cancer. It has become clear that such mutations are introduced in part by error-prone DNA polymerases. In response to many environmental genotoxins, eukaryotic cells have evolved alternative methods of replicating damaged DNA, via the Trans-lesion synthesis (TLS) Polymerases, consisting of DNA Pol h, Pol k, Pol i, and Rev1. The TLS polymerases are recruited to stalled replication forks, where they mediate replication past damaged DNA. TLS is a central mechanism of replicating DNA that has been modified by exposure to environmental carcinogens, but the TLS is an inherently error-prone process. In addition, aberrant utilization of the TLS polymerases greatly predisposes to mutagenesis. Proper regulation and function of the TLS polymerases is thus a crucial mechanism of protecting genomic integrity. This research will study the mechanisms that regulate recruitment of TLS polymerases to sites of DNA damage in response to environmental genotoxins. In particular, we will test the hypothesis that Cdc7-mediated phosphorylation of Rad18 promotes formation of Rad18-Polh complexes and facilitates bypass of solar UV-induced DNA lesions. In addition, we will determine the mechanisms by which Rad18 ensures selection of the appropriate TLS polymerase in response to UV-induced (Polh) or BPDE- induced (PolK) DNA damage. These experiments will determine the significance of interactions between the TLS polymerases, Rad18, and Cdc7 and will help elucidate the mechanisms responsible for regulating TLS polymerases. Results of our studies will provide a novel link between normal and damage-induced replication and will help explain how environmental genotoxins contribute to mutagenesis.