P53-Mediated G1/M Checkpoint Controls Altered by PPM1D

描述（由申请人提供）：P53介导的G1/M检查点控制被PPM 1D改变p53肿瘤抑制蛋白是一种序列特异性转录因子，其调节细胞对遗传毒性应激和其他形式的细胞应激的反应。PPM 1D（正式称为Wip 1）以p53依赖性方式响应遗传毒性应激而转录激活。它编码一种蛋白磷酸酶，靶向破坏p38 MAPK-p53信号通路的应激诱导激酶p38 MAPK。这与p53蛋白N-末端磷酸化模式的改变相关。N端磷酸化对p53蛋白作为转录因子发挥作用是重要的。我们和其他人已经表明，PPM 1D的强制外源性表达减弱了对DNA损伤剂的凋亡反应。在由于基因扩增而组成性过表达的人肿瘤细胞中，降低PPM 1D可增强对化疗剂的凋亡反应。这与变化有关，本研究的目的是阐明PPM 1D在调节p53转录活性中的作用及其机制。我们的假设是PPM 1D阻断p38 MAPK-p53信号通路，影响p53介导的细胞周期检查点调控和/或凋亡相关基因的转录。或凋亡。具体目的如下：1）确定PPM 1D介导的p38 MAPK-p53信号转导的中断是否改变了p53蛋白与下游靶基因的p53应答元件之间的相互作用。2)确定PPM 1D介导的p38 MAPK-p53信号转导的中断是否改变了p53蛋白与转录辅激活因子的相互作用。3)鉴定和表征PPM 1D介导的p38 MAPK-p53信号通路破坏改变其表达的基因。摘要：PPM 1D是p53网络中的一个新成员，目前我们对它知之甚少。PPM 1D基因通常在携带野生型p53基因的人乳腺癌、卵巢癌和神经母细胞瘤中扩增。该项目将提供有关PPM 1D在参与细胞周期控制和凋亡的p53网络中所起作用的新信息，并阐明这种作用的机制基础。

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.