The ATM/E2F1 Pathway in DNA Damage and Growth Control

描述(申请人提供)：转录因子E2F1在控制细胞增殖和凋亡中起着关键作用。最近，我们在E2F1的调控中发现了一个涉及PI3K/Akt的新的Pocket蛋白非依赖性途径和一个含有BRCT结构域的蛋白TopBP1。我们的初步数据进一步证明，E2F可以受到另一个含有BRCT结构域的蛋白MCPH1/BRIT1的调控。长期以来，PRB家族成员一直被认为是E2F的主要监管者。TopBP1和MCPH1似乎是一类新的E2F调节因子。它们都含有多个BRCT基序，并通过它们的BRCT基序与E2F1的N末端相互作用。TopBP1是负调节因子，而MCPH1是E2F1靶基因在检查点/修复和细胞凋亡中的正调节因子。这两种蛋白质也直接参与DNA损伤检查点的激活。在这项提案中，我们的目标是描述这些调控E2F1蛋白活性和稳定性的新调控的功能和机制。首先，我们将阐明生长因子信号通过TopBP1控制E2F1的机制。其次，我们将确定MCPH1如何调控E2F1。TopBP1和MCPH1如何响应环境和调节E2F1活性也将被研究。最后，我们将研究E2F1蛋白是如何被ATM磷酸化诱导的。在这个项目完成后，我们将阐明E2F1的增殖和促凋亡活性是如何被差异调控的。了解E2F1在生长和DNA损伤中的活性和稳定性的控制，可能为利用E2F1促凋亡活性来提高化疗敏感性提供新的途径。公共卫生相关性：增殖和细胞死亡之间的适当平衡对正常生长至关重要。最近的研究已经确定了E2F1在这种控制中的作用，特别是在DNA损伤方面。在我们的上一次资助期间，我们发现了一类新的E2F1调节器。我们将阐明在肿瘤治疗中增强E2F1诱导的细胞杀伤的调节机制及其临床应用的意义。

DESCRIPTION (provided by applicant): The transcription factor E2F1 plays a pivotal role in the control of cell proliferation and apoptosis. Recently we uncovered a novel pocket proteins-independent pathway involving PI3K/Akt and a BRCT domain-containing protein TopBP1 in the control of E2F1 Our preliminary data further demonstrate E2F can be regulated by another BRCT domain-containing protein, MCPH1/BRIT1. The pRb family members have long been considered to be the major regulators for E2F. TopBP1 and MCPH1 appear to be a new class of E2F regulators. They both contain multiple BRCT motifs and interact with the N- terminus of E2F1 through their BRCT motifs. TopBP1 is a negative regulator, whereas, MCPH1 is a positive regulator of E2F1 target genes in checkpoint/repair and apoptosis. Both proteins are also directly involved in DNA damage checkpoint activation. In this proposal, we aim to characterize the functions and mechanisms of these novel regulations governing E2F1 protein activity and stability. First, We will elucidate the mechanism by which growth factor signalings control E2F1 through TopBP1. Second, We will determine how MCPH1 regulates E2F1. How TopBP1 and MCPH1 respond to environmental milieu and regulate E2F1 activity will also be investigated. Lastly, we will investigate how E2F1 protein is induced in response to ATM phosphorylation. Upon completion of this project, we will elucidate how the proliferative and pro-apoptotic activities of E2F1 are differentially regulated. Understanding the control of E2F1 activity and stability in growth and DNA damage may provide novel approaches in harness E2F1 pro-apoptotic activity to enhance chemosensitivity. PUBLIC HEALTH RELEVANCE: Proper balance between proliferation and cell death is essential for normal growth. Recent studies have established a role for E2F1 in this control, especially upon DNA damage. During our last grant period, we discovered a novel class of E2F1 regulators. We will elucidate the mechanisms of regulation and the implications to clinical application in enhancing E2F1-induced cell killing in cancer therapy.