Regulation of p21waf1/cip1 by Rho and Ras signaling

Rho 和 Ras 信号传导对 p21waf1/cip1 的调节

• 批准号: 6729460
• 负责人: MICHAEL FRANCIS OLSON
• 金额: $ 28.21万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-30 至 2004-07-20
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6729460
• 关键词: actins; biological signal transduction; cell growth regulation; cell line; cell proliferation; cyclins; embryo /fetus cell /tissue; genetic transcription; guanine nucleotide binding protein; microinjections; neoplastic transformation; oncoprotein p21; posttranslational modifications; protein degradation; protein quantitation /detection; protein structure function; tissue /cell culture; transfection; yeast two hybrid system

DESCRIPTION (provided by applicant): Ras GTPase proteins (K-Ras, H-Ras, N-Ras) were first identified because of their association with oncogenic transformation. Activating oncogenic Ras mutations have been found in a variety of tumor types with an overall incidence of approximately 30% in human cancers. Despite the robust transforming ability of oncogenic Ras, additional signaling pathways influence the efficiency of Ras-induced oncogenesis. One signaling protein that contributes to oncogenic transformation by Ras is the Rho GTPase. Inhibition of Rho significantly impairs Ras-driven transformation, while active Rho synergistically co-operates with Ras or with the Ras effector protein Raf to promote transformation. In characterizing the basis of Rho and Ras cooperation, we found that Rho suppresses Ras-induction of the cyclin dependent kinase inhibitor p21Waf1/Cip1 (p21), thereby facilitating cell cycle progression. One mechanism of p21 suppression by Rho is through repression of Ras-induced transcriptional activation. While acute high intensity Ras signaling leads to cell cycle arrest due to the transcriptional up-regulation of p21, cells stably transformed by Ras have high levels of active Rho which suppresses p21 transcription thereby permitting cell cycle progression, p21 protein levels are significantly higher in Ras-transformed cells than in untransformed parental cells, despite comparable levels of p21 mRNA due to Rho-mediated transcriptional suppression, suggesting that posttranscriptional mechanisms are responsible for the elevation in protein levels. These findings raise several key questions. 1) What is the post-transcriptional mechanism that raises p21 protein levels in Ras transformed cells? 2) Does Rho activity squelch p21 levels by post-transcriptional means in addition to transcriptional suppression? 3) What is the pathway downstream of Rho that leads to p21 transcriptional suppression? To answer these questions, we will use cell biological and in vitro biochemical methods. Unlike the p16 cyclin dependent kinase inhibitor which is frequently deleted in tumors with Ras mutations, p21 has not been reported to be lost, suggesting that inhibiting Rho function to elevate p21 levels and arrest cell cycle progression potentially would be an effective anti-cancer therapeutic strategy.

描述（由申请人提供）： Ras GT3蛋白（K-Ras、H-Ras、N-Ras）由于其与致癌转化相关而首先被鉴定。激活致癌Ras突变已在多种肿瘤类型中发现，在人类癌症中的总发病率约为30%。尽管致癌Ras具有强大的转化能力，但其他信号传导途径影响Ras诱导的肿瘤发生的效率。一种有助于Ras致癌转化的信号蛋白是Rho GT3。Rho的抑制显著损害Ras驱动的转化，而活性Rho与Ras或Ras效应蛋白Raf协同合作以促进转化。在表征Rho和Ras合作的基础上，我们发现Rho抑制细胞周期蛋白依赖性激酶抑制剂p21 Waf 1/Cip 1（p21）的Ras诱导，从而促进细胞周期进程。Rho抑制p21的一种机制是通过抑制Ras诱导的转录激活。虽然急性高强度Ras信号传导由于p21的转录上调而导致细胞周期停滞，但Ras稳定转化的细胞具有高水平的活性Rho，其抑制p21转录，从而允许细胞周期进展，Ras转化的细胞中的p21蛋白水平显著高于未转化的亲本细胞，尽管由于Rho介导的转录抑制，p21 mRNA的水平相当，这表明转录后机制是蛋白水平升高的原因。这些发现提出了几个关键问题。1)Ras转化细胞中p21蛋白水平升高的转录后机制是什么？2)除了转录抑制外，Rho活性是否通过转录后手段抑制p21水平？3)Rho下游导致p21转录抑制的途径是什么？为了回答这些问题，我们将使用细胞生物学和体外生化方法。与p16细胞周期蛋白依赖性激酶抑制剂（其在具有Ras突变的肿瘤中经常缺失）不同，尚未报道p21丢失，这表明抑制Rho功能以提高p21水平并阻止细胞周期进展可能是有效的抗癌治疗策略。