Mechanisms of p53 activation during stress response

应激反应中p53的激活机制 P53在应激反应中的稳定和激活是其肿瘤抑制因子的关键 功能DNA损伤通过激活ATM诱导p53积聚。我们最近发现了多个 MDM2（一种促进p53的E3连接酶）RING结构域附近的新ATM磷酸化位点 泛素化突变分析表明，这些位点以冗余方式调节p53， DNA损伤后的稳定性阻断MDM2磷酸化可防止DNA转染后p53稳定化 损害MDM2的磷酸化特异性阻断p53多聚泛素化，但不阻断单聚泛素化。 泛素化我们还发现MDM2与组蛋白甲基转移酶相互作用，诱导p53 C 末端赖氨酸甲基化。因此，MDM2是ATM稳定的重要信号靶标， 第53页。此外，MDM2通过新的机制调节p53转录活性。的 本文拟通过以下实验进一步研究应激过程中p53的激活机制 反应(1)通过MDM2磷酸化确定p53稳定化的机制， DNA损伤。(2)研究MDM2结合蛋白稳定p53的机制 在非遗传毒性压力下。(3)研究MDM2介导的p53活性调节 赖氨酸甲基化(4)检测MDM 2磷酸化在p53肿瘤中的体内作用 镇压这些实验将有助于更好地理解新的机制， 激活p53，并且对于开发在癌症中靶向MDM2的新策略至关重要。 0

Mechanisms of p53 activation during stress response P53 stabilization and activation in response to stress is critical for its tumor suppressor function. DNA damage induces p53 accumulation by activating ATM. We recently identified multiple novel ATM phosphorylation sites near the RING domain of MDM2, an E3 ligase that promotes p53 ubiquitination. Mutational analyses showed that these sites act in a redundant fashion to regulate p53 stability after DNA damage. Blocking MDM2 phosphorylation prevents p53 stabilization after DNA damage. Phosphorylation of MDM2 specifically blocks p53 poly-ubiquitination but not mono- ubiquitination. We also found that MDM2 interacts with histone methyltransferases and induces p53 C terminal lysine methylation. Therefore, MDM2 is an important signaling target in ATM stabilization of p53. Furthermore, MDM2 regulates p53 transcriptional activity through novel mechanisms. The following experiments are proposed to further study the mechanisms of p53 activation during stress response. (1) Determine the mechanism of p53 stabilization by MDM2 phosphorylation after DNA damage. (2) Investigate the mechanism of p53 stabilization by MDM2-binding proteins during non-genotoxic stress. (3) Investigate the regulation of p53 activity by MDM2-mediated lysine methylation. (4) Test the in vivo function of MDM2 phosphorylation in p53 tumor suppression. These experiments will lead to better understanding of the novel mechanisms that activate p53, and are critical for developing novel strategies of targeting MDM2 in cancer. 0