Mechanisms of p53 activation during stress response (MPI)

描述（由申请人提供）：野生型p53在应激反应中的稳定和激活对其抑瘤功能至关重要。矛盾的是，突变型p53在肿瘤中也高度稳定，并通过功能获得促进转移和治疗抵抗。阐明调节p53稳定性和激活的机制可能提供针对野生型或突变型p53的新治疗策略。MDM2和MDMX是p53泛素化、DNA结合和转录活性的主要调节因子。我们最近的研究表明，atm依赖的MDM2和MDMX在环结构域附近的磷酸化对于p53的稳定和激活是重要的。我们发现这些磷酸化事件抑制了MDM2环结构域的同二聚化，抑制了MDM2环与酸性结构域的分子内相互作用，抑制了MDMX酸性结构域与p53结合结构域的分子内相互作用。我们还发现MDM2酸性结构域是RING结构域E3连接酶活性的重要激活因子。这些发现导致假设不同的信号通路靶向MDM2和MDMX分子内相互作用来稳定和激活p53。为了进一步研究应激反应中p53的激活机制，我们拟开展以下实验。(1)确定MDM2酸性结构域的功能和作用机制。(2)研究胁迫信号对MDM2结构域相互作用的调控。(3)测试靶向分子内相互作用的新策略(4)表征MDM2和MDMX结构域相互作用的结构和动力学。本实验将使我们对p53调控的认识达到一个新的水平，探索MDM2和MDMX的分子内调控机制，并为研究和靶向MDM2和MDMX制定新的策略。

DESCRIPTION (provided by applicant): Wild type p53 stabilization and activation in response to stress is critical for its tumor suppressor function. Paradoxically, mutant p53 is also highly stabilized in tumors and promotes metastasis and therapy resistance through gain-of-function. Elucidating the mechanisms that regulate p53 stability and activation may provide novel therapeutic strategies that target wild type or mutant p53. MDM2 and MDMX are major regulators of p53 ubiquitination, DNA binding, and transcriptional activity. Our recent study suggested that ATM-dependent phosphorylation of MDM2 and MDMX near the RING domains are important for stabilization and activation of p53. We found that these phosphorylation events inhibit the homo-dimerization of MDM2 RING domain, inhibit the intra- molecular interaction between the MDM2 RING and acidic domains, and inhibit the intra-molecular interaction between MDMX acidic and p53 binding domains. We also identified the MDM2 acidic domain as an important activator of the RING domain E3 ligase activity. These findings led to the hypothesis that various signaling pathways target the intra-molecular interactions in MDM2 and MDMX to stabilize and activate p53. The following experiments are proposed to further study the mechanisms of p53 activation during stress response. (1) Determine the function and mechanism of the MDM2 acidic domain. (2) Investigate the regulation of MDM2 domain interactions by stress signals. (3) Test a novel strategy of targeting intra-molecular interactions (4) Characterize the structure and dynamics of the MDM2 and MDMX domain interactions. The proposed experiments will lead to a new level of understanding of p53 regulation, explore novel intra- molecular regulatory mechanisms of MDM2 and MDMX, and develop new strategies for investigating and targeting MDM2 and MDMX.