P53-Mediated G1/M Checkpoint Controls Altered by PPM1D

描述(申请人提供)：PPM1D改变的p53介导的G1/M检查点控制PPM1D P53肿瘤抑制蛋白是一种序列特异性转录因子，调节细胞对基因毒性应激和其他形式的细胞应激的反应。PPM1D(正式名称为Wip1)是以P53依赖的方式在转录水平上激活的，以响应遗传毒性压力。它编码一种蛋白磷酸酶，靶向应激诱导的蛋白激酶p38MAPK，从而破坏p38MAPK-P53信号通路。这与P53蛋白N端磷酸化模式的改变有关。N-末端的磷酸化是P53蛋白发挥转录因子功能的重要途径。我们和其他人已经证明，强制外源表达PPM1D可以减弱对DNA损伤剂的凋亡反应。减少人类肿瘤细胞中由于基因放大而结构性过度表达的PPM1D增强了对化疗药物的凋亡反应。这个项目的目的是阐明PPM1D在调节p53转录活性方面的机制基础和作用。需要检验的假设是，PPM1D破坏p38MAPK-P53信号通路，影响参与细胞周期检查点控制和/或细胞凋亡的反应基因的转录。具体目的如下：1)确定PPM1D介导的p38MAPK-P53信号的干扰是否改变了P53蛋白与下游靶基因的P53反应元件之间的相互作用。2)确定PPM1D介导的p38MAPK-P53信号的阻断是否改变了P53蛋白与转录共激活因子的相互作用。3)研究PPM1D对p38MAPK-P53信号通路的干扰作用，发现其表达改变的基因。摘要：PPM1D是P53网络中的一个新成员，目前我们对其知之甚少。PPM1D基因通常在含有野生型p53基因的人乳腺、卵巢和神经母细胞瘤中扩增。本项目将提供有关PPM1D在参与细胞周期控制和细胞凋亡的P53网络中所起作用的新信息，并阐明这一作用的机制基础。

DESCRIPTION (provided by applicant): P53-Mediated G1/M Checkpoint Controls Altered by PPM1D The p53 tumor suppressor protein is a sequence-specific transcription factor that modulates the response of cells to genotoxic stress and other forms of cellular stress. PPM1D (formally called Wip1) is transcriptionally-activated in response to genotoxic stress in a p53-dependent manner. It encodes a protein phosphatase that targets the stress induced kinase p38MAPK which disrupts the p38MAPK-p53 signaling pathway. This is correlated with alterations in the pattern of N-terminal phosphorylation on p53 protein. N-terminal phosphorylation is important for p53 protein to function as a transcriptional factor. We and others have shown that forced exogenous expression of PPM1D attenuates the apoptotic response to DNA-damaging agents. Decreasing PPM1D in human tumor cells that constitutively over express it due to gene amplification enhances the apoptotic response to chemotherapeutic agents. This is correlated with changes, in the level of expression of the pro-apoptotic Bax gene.The goal of this project is to elucidate the mechanistic basis and the role that PPM1D plays in modulating the transcriptional activity of p53.The hypothesis to be tested is that disruption of the p38MAPK-p53 signaling pathway by PPM1D affects p53-mediated transcription of responsive genes involved in cell cycle checkpoint control and/or apoptosis. The Specific Aims are the following: 1) To determine if PPM1D-mediated disruption of p38MAPK-p53 signaling alters the interaction between p53 protein and p53-responsive elements of downstream target genes. 2) To determine if PPM1D-mediated disruption of p38MAPK-p53 signaling alters the interaction of p53 protein with transcriptional coactivators. 3) To identify and characterize genes whose expression is altered by PPM1D-mediated disruption of the p38MAPK-p53 signaling pathway. Lay Abstract: PPM1D is a new player in the p53 network about which we know very little at present. The PPM1D gene is often amplified in human breast, ovarian and neuroblastoma tumors that harbor a wild type p53 gene. This project will provide new information regarding the role that PPM1D plays in the p53 network involved in cell cycle control and apoptosis and elucidate the mechanistic basis for this action.