The Role of ATF3 in the DNA Damage Response

描述(申请人提供)：细胞对DNA损伤的反应是一种早期的抗癌屏障，通过激活肿瘤抑制因子P53来维持基因组的完整性。先前的研究表明，ATF3是一种即刻早期基因，作为细胞对广泛DNA损伤的反应的一部分，通过与肿瘤抑制因子结合来促进P53的激活。虽然ATF3在各种癌症中表达下调，但ATF3的缺失会损害DNA损伤反应，导致肿瘤发生。这项建议的目的是阐明ATF3在DNA损伤反应和肿瘤抑制中的调节作用，重点是了解ATF3在面对致癌挑战时调节P53活性的机制。初步研究表明，ATF3不仅调节P53的稳定性和反式激活活性，而且发现ATF3与其他P53网络蛋白包括E3泛素连接酶MDM2和组蛋白乙酰转移酶p300、Tip60和hMOF有关。因此，我们假设这些相互作用可能是ATF3在DNA损伤反应中调节p53肿瘤抑制活性的机制背后的原因。在目标1中，将测试一个假设，即ATF3和MDM2之间的相互作用通过调节MDM2与p53的结合和/或其对p53泛素化的催化活性来促进p53的稳定。此外，我们将利用MDM2基因敲除小鼠来表征ATF3-MDM2反馈环对p53调控的贡献。在目标2中，我们将检验一个假设，即ATF3通过促进P53与其转录辅助调节因子的相互作用来调节P53的反式激活活性。为此，将确定ATF3对p300、Tip60和hMOF催化的P53乙酰化的影响，以及随后的表观遗传学改变和对激活P53靶基因表达至关重要的转录调节因子的招募。在目标3中，我们将使用基因工程动物模型评估ATF3对肿瘤抑制的贡献。还将培育ATF3缺陷小鼠，并测试其对吸烟致癌物诱发肺癌的敏感性。总之，这些研究将提供证据，支持ATF3在P53介导的DNA损伤反应和肿瘤抑制中发挥不可或缺的作用。鉴于DNA损伤反应不足是癌症发生和发展的驱动力，从拟议的研究中获得的基本新知识将使ATF3成为癌症预防和/或治疗的有希望的靶点。

DESCRIPTION (provided by applicant): The cellular response to DNA damage is an early anti-cancer barrier that maintains the genomic integrity by activating the tumor suppressor p53. Previous studies show that ATF3, an immediate-early gene which is rapidly induced as a part of cellular response to a wide-range of DNA damage, promotes p53 activation by binding to the tumor suppressor. Whereas ATF3 expression is down-regulated in various cancers, loss of ATF3 impairs the DNA damage response and results in tumorigenesis. The goal of this proposal is to elucidate the role of ATF3 in regulation of the DNA damage response and tumor suppression with a focus on understanding of the mechanisms by which ATF3 regulates p53 activity in face of oncogenic challenges. Preliminary studies show that ATF3 regulates not only the stability but also the trans-activation activity of p53, and also discover a link of ATF3 with other p53 network proteins including E3 ubiquitin ligase MDM2 and histone acetyltransferases p300, Tip60 and hMOF. We therefore hypothesize that these interactions could be behind the mechanisms by which ATF3 regulates p53 tumor suppressor activity in the DNA damage response. In Aim #1, a hypothesis that the interaction between ATF3 and MDM2 contributes to p53 stabilization by regulating the binding of MDM2 to p53 and/or its catalytic activity towards p53 ubiquitination will be tested. In addition, we will characterize the contribution of the ATF3-MDM2 feedback loop to p53 regulation using Mdm2-knockout mice. In Aim #2, we will test a hypothesis that ATF3 regulates p53 trans-activation activity by promoting the interactions of p53 with its transcriptional co-regulators. Towards this aim, effects of ATF3 on p53 acetylation catalyzed by p300, Tip60 and hMOF, and subsequent epigenetic alterations and recruitments of transcriptional regulators that are essential for activation of p53- target gene expression will be determined. In Aim #3, we will assess the contribution of ATF3 to tumor suppression using genetically-engineered animal models. ATF3-deficient mice will also be bred and tested for its susceptibility to lung carcinogenesis induced by smoke carcinogens. Together these studies will render evidence supporting an indispensable role of ATF3 in p53-mediated DNA damage response and tumor suppression. Given that inadequate DNA damage response is a driving force for cancer initiation and progression, the fundamental new knowledge obtained from the proposed studies will establish ATF3 as a promising target for preventive and/or therapeutic treatments of cancer.