Antiapoptotic Role of Ataxia Telangiectasia and Rad3-Related

描述（由申请人提供）：由于自愿或非自愿暴露于各种环境遗传毒性物质（例如辐射和化学致癌物）而导致的DNA损伤是人类癌症和许多其他人类疾病的主要原因。在DNA损伤的反应中，细胞激活了几种主要的DNA损伤反应（DDR）途径，如DNA损伤检查点、DNA修复和细胞凋亡。ATM （ataxia毛细血管扩张突变）和ATR （ATM和rad3相关）是两种主要的DNA损伤检查点蛋白激酶，它们通过信号传导DNA损伤、激活检查点、阻止细胞周期进程和促进DNA修复以恢复DNA完整性，在DDR中发挥关键作用。ATM和ATR都是属于磷酸肌苷3激酶相关蛋白激酶（PIKK）家族的蛋白激酶，是细胞应激的传感器。然而，有趣的是，来自小鼠模型和人类流行病学研究的大量证据表明，与缺乏ATR促进癌变不同，ATR抑制抑制癌变。考虑到DNA损伤检查点的一般癌症抑制作用，这令人困惑。在本项目中，我们将验证以下假设：(1)除了通过其在细胞核中对中度DNA损伤的检查点调节作用作为肿瘤抑制因子外，细胞质中的ATR还可以在严重DNA损伤时作为线粒体中的抗凋亡蛋白；(2)细胞质中的这种抗凋亡活性是通过ATR以不依赖于检查点的方式直接参与调节DNA损伤诱导的线粒体细胞死亡途径而发生的；(3) ATR从肿瘤抑制因子向抗凋亡蛋白的转化是由胞质ATR的脯氨酸异构体修饰调控的。这种修饰改变了ATR的构象，使其具有抗凋亡作用，从而抑制了癌变。这些假设将在以下具体目标中进行检验。目的1：明确紫外光诱导胞质ATR修饰及其细胞效应；目的2：确定胞质ATR功能受调控的机制；目的3：确定ATR抗线粒体凋亡活性的分子基础。拟议的研究代表了与癌症和其他人类疾病（如神经退行性疾病和心血管疾病）高度相关的创新努力。

DESCRIPTION (provided by applicant): DNA damage due to voluntary or involuntary exposure to various environmental genotoxic agents (e.g. irradiation and chemical carcinogens) is a major cause of human cancers and many other human diseases. In response to DNA damage, cells activate several major DNA damage response (DDR) pathways such as DNA damage checkpoints, DNA repair, and apoptosis. ATM (ataxia telangiectasia mutated) and ATR (ATM and Rad3-related) are the two major DNA damage checkpoint protein kinases which play critical roles in DDR by signaling DNA damage, activating checkpoints, arresting cell cycle progression and facilitating DNA repair to restore DNA integrity. Both ATM and ATR are protein kinases belonging to the phosphoinositide 3-kinase-related protein kinases (PIKK) family and are sensors of cellular stress. Intriguingly, however, a body of evidence from mouse model and human epidemiologic studies show that unlike ATM whose deficiency promotes carcinogenesis, ATR inhibition suppresses carcinogenesis. This is puzzling given the general cancer-suppression role of DNA damage checkpoints. In this project, we will test the hypothesis that (1) besides functioning as a tumor suppressor via its checkpoint regulatory role in the nucleus against moderate DNA damage, ATR in the cytoplasm can function as an anti-apoptotic protein at mitochondria upon severe DNA damage; (2) this anti-apoptotic activity in the cytoplasm occurs via direct involvement of ATR in regulating the DNA damage-induced mitochondria cell death pathways in a checkpoint-independent manner; and (3) this transformation of ATR from tumor suppressor to anti-apoptotic protein is regulated by a prolyl isomeric modification of the cytoplasmic ATR. The modification changes the conformation of ATR, making it anti-apoptotic so that its inhibition suppresses carcinogenesis. These hypotheses will be tested in the following specific aims. Aim 1: To define the UV-induced modification of cytoplasmic ATR and its cellular effects; Aim 2: To determine the mechanisms by which the functions of cytoplasmic ATR are regulated; and Aim 3: To determine the molecular basis of the ATR anti-apoptotic activity at mitochondria. The proposed studies represent an innovative effort highly relevant to cancer and other human diseases such as neurodegenerative and cardiovascular diseases.