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，由于其在调节基因表达、细胞对DNA损伤的反应以及作为肿瘤抑制因子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。在这笔赠款的前一个周期中，我们发现两种病毒使用病毒编码的癌蛋白，来自人乳头瘤病毒(HPV)的E6癌蛋白和腺病毒的E1b55K+E4Orf6癌蛋白，通过蛋白酶体促进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。与此同时，我们发现一种细胞去泛素酶USP7可以稳定人类细胞中的Tip60。我们现在建议调查蛋白酶体介导的Tip60降解是否可以用于治疗。目的1验证HPV E6癌蛋白对Tip60的降解是由Tip60与E6之间直接的蛋白质-蛋白质相互作用介导的，这种降解导致HPV感染细胞和肿瘤的细胞基因表达、细胞转化和放射敏感性的改变。我们还将测试Tip60的稳定性是否会损害器官型移植物培养中角质形成细胞的复制寿命，从而成为抑制HPV感染的潜在途径。目的2将验证腺病毒癌蛋白通过利用特定的细胞蛋白产生病毒特异性的E3泛素连接酶来降解Tip60的假设，并且这 降解会改变病毒的基因表达程序，以促进病毒复制。该项目推进了我们在病毒癌蛋白降解Tip60方面的新发现。该项目的成功将加深我们对HPV感染癌症的了解，并确定一种新的机制，即腺病毒癌蛋白通过去调节细胞机制来促进病毒感染。

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.