Regulation of TIP60 by the ubiquitin-proteasome pathway

描述（申请人提供）：TIP60是一种细胞赖氨酸乙酰转移酶，由于其在基因表达调控、细胞对DNA损伤的反应和肿瘤抑制中的作用而受到越来越多的关注。TIP60乙酰化组蛋白和参与DNA损伤反应的关键细胞蛋白，如p53、p21和ATM激酶。在本研究的前一个周期中，我们发现两种病毒使用病毒编码的癌蛋白，即来自人乳头瘤病毒（HPV）的E6癌蛋白和来自腺病毒的E1b55K+E4Orf6癌蛋白，来促进蛋白酶体对TIP60肿瘤抑制因子的降解。TIP60的降解对于调节病毒基因的表达和调节细胞对DNA损伤的反应是重要的。同时，我们发现细胞去泛素酶USP7可以稳定人类细胞中的TIP60。我们现在建议研究蛋白酶体介导的TIP60降解是否可以用于治疗。Aim 1将验证HPV E6癌蛋白对TIP60的降解是通过TIP60和E6之间的直接蛋白-蛋白相互作用介导的，并且这种降解导致HPV感染细胞和癌症的细胞基因表达、细胞转化和对放疗易感性的变化。我们还将测试TIP60的稳定是否会损害器官型筏培养中病毒角化细胞的复制寿命，从而成为抑制HPV感染的潜在途径。目的2将测试假设，即腺病毒癌蛋白通过利用特定的细胞蛋白来产生病毒特异性E3泛素连接酶来降解TIP60，并证明这一点

DESCRIPTION (provided by applicant): TIP60 is a cellular lysine acetyltransferase that is getting increasing attention because of its role in the regulation of gene expression, in the response of a cell to DNA damage and as a tumor suppressor. TIP60 acetylates histones and critical cellular proteins involved in DNA damage response like p53, p21 and ATM kinase. In the previous cycle of this grant we discovered that two viruses use virally encoded oncoproteins, the E6 oncoprotein from human papilloma virus (HPV) and the E1b55K+E4Orf6 oncoproteins from adenovirus, to promote the degradation of the TIP60 tumor suppressor by proteasomes. The degradation of TIP60 is important for regulating the expression of viral genes and for modulating the cell's response to DNA damage. In parallel, we discovered that a cellular deubiquitinase, USP7, stabilizes TIP60 in human cells. We now propose to investigate whether the proteasome-mediated degradation of TIP60 can be exploited for therapy. Aim 1 will test the hypothesis that the degradation of TIP60 by HPV E6 oncoprotein is mediated by direct protein-protein interactions between TIP60 and E6, and that the degradation leads to changes in cellular gene expression, cell transformation and the susceptibility to radiotherapy of HPV-infected cells and cancers. We will also test whether stabilization of TIP60 impairs the replicative life of the virusin keratinocytes in organotypic raft cultures and thus be a potential avenue of suppressing HPV infection. Aim 2 will test the hypothesis that adenovirus oncoproteins degrade TIP60 by harnessing specific cellular proteins to create a virus-specific E3 ubiquitin ligase, and that this degradation alters viral gene expression programs to facilitate viral replication. This project advances our novel discoveries on the degradation of TIP60 by viral oncoproteins. Success in this project will enhance our understanding of HPV-infected cancers and identify a new mechanism by which adenovirus oncoproteins de-regulate the cellular machinery to facilitate viral infection.