Radiation activation of the ATM protein

描述(申请人提供)：ATM蛋白参与检测和修复遗传毒性损伤。ATM功能的丧失会使细胞对电离辐射敏感，并与癌症发病率的增加有关。因此，ATM蛋白与肿瘤的发病机制和肿瘤对放射治疗的敏感性密切相关。将这些基因毒性损伤的检测与ATM激活联系起来的信号转导途径尚不清楚。我们现在已经证明，Tip60组蛋白乙酰转移酶对于暴露在电离辐射下的细胞中ATM蛋白的激活是必不可少的。作为对电离辐射的响应，Tip60‘S组蛋白乙酰转移酶的活性增加，导致ATM的乙酰化和ATM的激酶活性上调。ATM和Tip60是含有EPD支架蛋白的新型DNA修复复合体的组成部分。长期目标是验证Tip60组蛋白乙酰转移酶是ATM蛋白的关键上游调节因子的假设。在特定目标1中，将鉴定ATM复合体的单个蛋白质组分，并确定支配ATM-epc1-Tip60复合体形成的分子相互作用。在特定的目标2中，我们将确定Tip60被DNA损伤激活的机制，并检验Tip60的色素域与DNA损伤部位的组蛋白直接相互作用的假设。此外，我们将确定Tip60在ATM招募到DNA损伤部位中的作用。在具体目标3中，我们将鉴定ATM上被Tip60乙酰化的赖氨酸残基(S)，确定乙酰化是如何激活ATM的，并研究ATM乙酰化的丢失如何影响细胞检测和修复DNA损伤的能力。因此，该提议将描述一种新定义的信号转导途径，在该途径中，DNA损伤的检测与下游信号事件的激活通过乙酰化联系在一起。了解基因毒性事件激活ATM的机制将为ATM如何抑制肿瘤形成提供关键见解；并将提供有关ATM在癌症中失活如何使个人容易患癌症的信息。此外，Tip60及其相关蛋白是开发可改变哺乳动物细胞IR反应的治疗剂的潜在靶点。这些新疗法的开发可以显著提高放射治疗的临床疗效。

DESCRIPTION (provided by applicant): The ATM protein is involved in the detection and repair of genotoxic lesions. Loss of ATM function sensitizes cells to ionizing radiation, and is associated with an increased incidence of cancer. The ATM protein is therefore intimately involved in both tumor pathogenesis and tumor sensitivity to radiation therapy. The signal transduction pathway linking the detection of these genotoxic lesions to the activation of ATM is not known. We have now shown that the Tip60 Histone acetyltransferase is essential for the activation of the ATM protein in cells exposed to ionizing radiation. In response to ionizing radiation, Tip60's histone acetyltransferase activity is increased, leading to acetylation of ATM and upregulation of ATM's kinase activity. ATM and Tip60 are components of a novel DNA repair complex containing the epd scaffold protein. The long term aim is to test the hypothesis that the Tip60 Histone acetyltransferase is the key upstream regulator of the ATM protein. In Specific Aim 1, the individual protein components of the ATM complex will be identified, and the molecular interactions which govern the formation of the ATM-epc1-Tip60 complex will be determined. In Specific Aim 2, we will determine the mechanism by which Tip60 is activated by DNA damage, and test the hypothesis that the chromodomain of Tip60 interacts directly with histones at sites of DNA damage. Further, we will determine the role of Tip60 in the recruitment of ATM to sites of DNA damage. In Specific Aim 3, we will identify the lysine residue(s) on ATM which are acetylated by Tip60, determine how acetylation activates ATM, and examine how loss of ATM acetylation affects the ability of cells to detect and repair DNA lesions. This proposal will therefore characterize a newly defined signal transduction pathway in which the detection of DNA lesions is linked to the activation of downstream signaling events through acetylation. Understanding the mechanism by which genotoxic events activate ATM will provide key insights into how ATM suppresses tumor formation; and will provide information on how the inactivation of ATM in cancer predisposes individuals to cancer. Further, Tip60 and its associated proteins are potential targets for developing therapeutic agents which can modify the IR response of mammalian cells. The development of such novel therapeutics could significantly improve the clinical efficacy of radiation therapy.