Ubiquitin specific peptidases as redox sensor in oncogene-induced p53 signaling

泛素特异性肽酶作为癌基因诱导的 p53 信号传导中的氧化还原传感器

• 批准号: 9015747
• 负责人: Xiongbin Lu
• 金额: $ 0.61万
• 依托单位: UNIVERSITY OF TX MD ANDERSON CAN CTR
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2017-06-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9015747
• 关键词: Biological Process; Breast Cancer Model; Breast Epithelial Cells; CHEK1 gene; CHEK2 gene; Cells; Cysteine; DNA Damage; Deubiquitination; Event; Exhibits; Expression Library; Goals; Health; Malignant - descriptor; Malignant Neoplasms; Mediating; Metabolic; Mitochondria; Molecular; Oncogene Activation; Oncogenes; Oncogenic; Oxidation-Reduction; Pathway interactions; Peptide Hydrolases; Phosphorylation; Physiological; Play; Premalignant Cell; Protein Kinase; Protein p53; Proteins; Reactive Oxygen Species; Regulation; Role; Serine; Signal Transduction; Site; Stress; TP53 gene; Threonine; Translating; Ubiquitin; Ubiquitination; base; cDNA Library; cancer initiation; genome-wide analysis; inhibitor/antagonist; mutant; novel; oxidation; protein degradation; response; senescence; sensor; tumor initiation; ubiquitin-protein ligase

 DESCRIPTION (provided by applicant): Oncogene-induced senescence (OIS) is a major anti-cancer barrier that inhibits malignant transformation of precancerous cells, in which the p53 signaling plays a central role. Previous studies have shown that p53 induction in precancerous cells is attributed to the ATM-mediated DNA damage response (DDR). Several protein kinases in the DDR, including ATM, CHK1 and CHK2, phosphorylate p53 at multiple serine/threonine sites, which has long been considered to stabilize and activate p53. However, we and other groups found that phosphorylation-deficient p53 mutant exhibited similar protein stability as the wildtype p53, suggesting that DDR-induced phosphorylation events may not be the only major factor for the p53 induction in response to oncogenic stress. The goal of this application is to unravel the oncogene-induced p53 response in mechanistic detail. P53 is tightly controlled at physiological levels by ubiquitination-mediated protein degradation. Much has been studied on the p53-targeting E3 ubiquitin ligases, such as Mdm2, ARF-BP1, and COP1, little is known about the deubiquitination of p53. In a genome-wide screen using a cDNA library of ubiquitin specific peptidases (USPs), we searched for potential USPs for p53 deubiquitination. Intriguingly, as many as 16 USPs significantly inhibited p53, while only 4 USPs moderately increased p53 activity. This result indicated that USPs probably modulate p53 activity primarily through promoting p53 inhibitors, such as E3 ubiquitin ligases. Since all of the p53-targeting E3 ubiquitin ligases are also degraded by auto-ubiquitination, a potential mechanism is that USPs negatively regulate p53 levels via deubiquitination and stabilization of the p53- targeting E3 ligases. This is true in the previously identified USP7-Mdm2-p53 regulatory loop, and is also supported by our current finding that USP4 inhibits p53 by deubiquitination and stabilization of ARF-BP1. Furthermore, p53 is induced upon oncogenic stress even in the absence of detectable DNA damage, suggesting a DDR-independent induction of p53. In this study, we show that oncogene-induced reactive oxygen species (ROS) inactivate the enzymatic activity of USPs through oxidation of crucial cysteine residues in their catalytic pockets, resulting in destabilization of the p53-targeting E3 ligases and consequential stabilization of p53. Based on these results, we propose that USPs function as redox sensor to translate oncogenic stress into the p53 signaling during cancer initiation.

 描述（由申请人提供）：癌基因诱导的衰老（OIS）是抑制癌前细胞恶性转化的主要抗癌屏障，其中p53信号传导起核心作用。以往的研究表明，p53在癌前细胞中的诱导归因于ATM介导的DNA损伤反应（DDR）。DDR中的几种蛋白激酶，包括ATM、CHK 1和CHK 2，在多个丝氨酸/苏氨酸位点磷酸化p53，这长期以来被认为是稳定和激活p53。然而，我们和其他研究小组发现，磷酸化缺陷型p53突变体表现出与野生型p53相似的蛋白质稳定性，这表明DDR诱导的磷酸化事件可能不是致癌应激诱导p53的唯一主要因素。本申请的目的是解开癌基因诱导的p53反应的机制细节。P53通过泛素化介导的蛋白质降解在生理水平上受到严格控制。针对p53的E3泛素连接酶如Mdm 2、ARF-BP 1和COP 1已被广泛研究，但对p53的去泛素化作用知之甚少。在一个全基因组的筛选中，使用泛素特异性肽酶（USP）的cDNA文库，我们寻找p53去泛素化的潜在USP。有趣的是，多达16个USP显著抑制p53，而只有4个USP适度增加p53活性。这一结果表明，USP可能主要通过促进p53抑制剂如E3泛素连接酶来调节p53活性。由于所有的p53靶向E3泛素连接酶也被自身泛素化降解，一个潜在的机制是USP通过去泛素化和稳定p53靶向E3连接酶来负调节p53水平。这在先前鉴定的USP 7-Mdm 2-p53调节环中是真实的，并且也得到我们目前发现的USP 4通过去泛素化和ARF-BP 1的稳定化抑制p53的支持。此外，即使在没有可检测到的DNA损伤的情况下，p53在致癌应激后也被诱导，这表明p53的DDR非依赖性诱导。在这项研究中，我们表明，癌基因诱导的活性氧（ROS）通过氧化其催化口袋中的关键半胱氨酸残基，导致p53靶向E3连接酶的不稳定性和p53的稳定性的USP的酶活性。基于这些结果，我们提出USPs作为氧化还原传感器，在癌症发生过程中将致癌应激转化为p53信号。