Regulatory Signaling in Repair of Environmentally Induced DNA Damage

描述（由申请人提供）：暴露于普遍存在的环境致癌物，如聚芳烃和紫外线，是人类疾病的原因。人们普遍认为基因突变是癌症发展的重要一步。很明显，这种突变部分是由易出错的DNA聚合酶引入的。为了应对许多环境基因毒素，真核细胞已经进化出了复制受损DNA的替代方法，通过由DNA Pol h、Pol k、Pol i和Rev1组成的跨损伤合成（TLS）聚合酶。TLS聚合酶被招募到停滞的复制叉，在那里它们介导受损DNA的复制。TLS是一种复制DNA的核心机制，DNA已被暴露于环境致癌物中而被修改，但TLS本身是一个容易出错的过程。此外，TLS聚合酶的异常利用大大增加了诱变的易感性。因此，TLS聚合酶的适当调控和功能是保护基因组完整性的关键机制。本研究将研究在环境基因毒素的作用下，TLS聚合酶在DNA损伤位点的募集机制。特别是，我们将验证cdc7介导的Rad18磷酸化促进Rad18- polh复合物的形成并促进绕过太阳紫外线诱导的DNA损伤的假设。此外，我们将确定Rad18在响应uv诱导（Polh）或BPDE诱导（PolK） DNA损伤时确保选择合适的TLS聚合酶的机制。这些实验将确定TLS聚合酶、Rad18和Cdc7之间相互作用的重要性，并将有助于阐明TLS聚合酶的调节机制。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基因毒素如何促进诱变。

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.