Role of WISp39 and Ubiquitination in p21 Function

描述(申请人提供)：p21WAF1/CIP1蛋白是一个关键的p53转录靶点，它是电离辐射后细胞周期停滞所必需的。P21-/-小鼠的组织细胞肉瘤、血管瘤/血管肉瘤和B细胞淋巴瘤的发生提示了p21在癌症中的重要性。P21的缺失也增加了腺瘤性息肉病线圈引发的胃肠道肿瘤，增加了化学诱导的皮肤癌，并与Rb和p18等其他抑癌基因的缺失协同作用。P21也被证明在自身免疫和干细胞再繁殖中发挥重要作用。 因此，我们必须了解控制p21蛋白水平的调控途径。虽然许多研究已经研究了转录调控在p21功能中的重要性，但翻译后调控的作用尚不清楚。翻译后机制对p21蛋白水平的调节是这项资助的重点。 在初步结果中，我们描述了一种稳定p21蛋白水平的新蛋白WISp39(P39)的鉴定。WISp39的作用就像一个接头蛋白，它通过其C端的TPR结构域招募Hsp90来稳定p21。我们建议详细研究Hsp90结合的TPR蛋白在调节p21稳定性和功能中的作用。 我们将使用组织培养模型和全动物模型来分析p39介导的p21稳定性的分子和功能特征。通过建立p39-/-小鼠，我们将在整个动物模型中评估p39在检查点控制中对p21稳定性以及肿瘤发生和发展的功能后果。最后，我们将研究非泛素化p21对细胞周期的影响以及细胞对DNA损伤的反应。

DESCRIPTION (provided by applicant): p21WAF1/CIP1 protein is a critical p53 transcriptional target, which is required for cell cycle arrest after ionizing radiation. The development of histiocytic sarcomas, hemangiomas/hemangiosarcomas and B cell lymphomas in p21 -/- mice suggests the importance of p21 in cancer. Loss of p21 also increases Adenomatous Polyposis Coil initiated gastrointestinal tumors, increases chemical induced skin carcinoma and cooperates with loss of other tumor suppressors like Rb and p18. p21 has also been shown to play an important role in autoimmunity and stem cell repopulation. It is therefore critical that we understand the regulatory pathways which control p21 protein levels. Although numerous studies have investigated the importance of transcriptional regulation in p21 function, the role of post translational regulation remains less clear. The regulation of p21 proteins levels by post translational mechanisms is the focus of this grant. In preliminary results we describe the identification of a novel protein WISp39 (p39) which stabilizes p21 protein levels. WISp39 acts like an adaptor protein which recruits Hsp90 (via its C-terminal TPR domain) in order to stabilize p21. We propose to investigate in detail the role of Hsp90 binding TPR proteins in regulating p21 stability and function. We will analyze the molecular and functional characteristics of p39 mediated p21 stability using both tissue culture models and whole animal models. By generating p39 -/- mice we will evaluate the functional consequences of p39 on p21 stability in checkpoint control, and tumor generation and development in a whole animal model. Finally we will study the effect of non-ubiquitinated p21 on cell cycle and the cellular response to DNA damage.