The Role of ATF3 in the DNA Damage Response

描述（由申请人提供）：对DNA损伤的细胞反应是一种早期抗癌屏障，通过激活肿瘤抑制因子p53来维持基因组完整性。以前的研究表明，ATF 3是一种立即早期基因，作为对广泛DNA损伤的细胞反应的一部分被快速诱导，通过与肿瘤抑制因子结合促进p53活化。尽管在各种癌症中ATF 3表达下调，但ATF 3的缺失损害DNA损伤反应并导致肿瘤发生。该提案的目标是阐明ATF 3在调节DNA损伤反应和肿瘤抑制中的作用，重点是了解ATF 3在面对致癌挑战时调节p53活性的机制。初步研究表明，ATF 3不仅调节p53的稳定性，而且调节p53的反式激活活性，还发现ATF 3与其他p53网络蛋白如E3泛素连接酶MDM 2、组蛋白乙酰转移酶p300、Tip 60和hMOF之间存在联系。因此，我们假设这些相互作用可能是ATF 3在DNA损伤反应中调节p53肿瘤抑制活性的机制。在目标#1中，将测试ATF 3和MDM 2之间的相互作用通过调节MDM 2与p53的结合和/或其对p53泛素化的催化活性而有助于p53稳定化的假设。此外，我们将使用Mdm 2敲除小鼠表征ATF 3-MDM 2反馈回路对p53调节的贡献。在目标#2中，我们将测试一个假设，即ATF 3通过促进p53与其转录辅助调节因子的相互作用来调节p53反式激活活性。为此，将确定ATF 3对由p300、Tip 60和hMOF催化的p53乙酰化的影响，以及随后的表观遗传改变和对p53靶基因表达的激活至关重要的转录调节因子的募集。在目标#3中，我们将使用基因工程动物模型评估ATF 3对肿瘤抑制的贡献。还将培育ATF 3缺陷型小鼠，并测试其对烟雾致癌物诱导的肺癌发生的易感性。这些研究将提供证据支持ATF 3在p53介导的DNA损伤反应和肿瘤抑制中不可或缺的作用。鉴于DNA损伤反应不足是癌症发生和进展的驱动力，从拟议研究中获得的基本新知识将使ATF 3成为预防和/或治疗癌症的有希望的靶点。

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.