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（例如聚芳烃和紫外线）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，此类突变部分是由容易出错的 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叉，在那里它们介导复制经过受损的 DNA。 TLS 是复制 DNA 的核心机制，由于接触环境致癌物而发生了改变，但 TLS 本质上是一个容易出错的过程。此外，TLS 聚合酶的异常利用极易导致诱变。因此，TLS 聚合酶的正确调节和功能是保护基因组完整性的关键机制。这项研究将研究调节 TLS 聚合酶募集到 DNA 损伤位点以响应环境基因毒素的机制。特别是，我们将测试以下假设：Cdc7 介导的 Rad18 磷酸化促进 Rad18-Polh 复合物的形成，并有助于绕过太阳紫外线诱导的 DNA 损伤。此外，我们将确定 Rad18 确保选择适当的 TLS 聚合酶来响应 UV 诱导 (Polh) 或 BPDE 诱导 (PolK) DNA 损伤的机制。这些实验将确定 TLS 聚合酶、Rad18 和 Cdc7 之间相互作用的重要性，并将有助于阐明负责调节 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基因毒素如何导致突变。

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.