Mechanisms of HTLV-I Tax-mediated NF-kB activation

HTLV-I Tax 介导的 NF-kB 激活机制

• 批准号: 8210991
• 负责人: EDWARD W HARHAJ
• 金额: $ 26.09万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-01 至 2014-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8210991
• 关键词: Adult; Automobile Driving; Binding; Binding Proteins; CD4 Positive T Lymphocytes; Cancer Biology; Cell Death; Cell Survival; Cells; Collaborations; Complex; Cytoprotection; Data; Deubiquitination; Disease; Enzymes; Event; Family; Feedback; Future; Gene Expression; Genes; Genome; Goals; Golgi Apparatus; Golgi Targeting; Health; Human T-Cell Leukemia Virus Type I tax Protein; Human T-Cell Leukemia Viruses; Human T-lymphotropic virus 1; Integration Host Factors; Investigation; Lead; Light; Link; Lipopolysaccharides; Lysine; MAPK8 gene; Malignant Neoplasms; Mediating; Molecular; Molecular Target; Movement; NF-kappa B; Oncogene Proteins; Phosphotransferases; Play; Polyubiquitin; Polyubiquitination; Principal Investigator; Proteins; Role; Signal Pathway; Signal Transduction; Signaling Protein; Study Section; T-Cell Leukemia; T-Lymphocyte; Taxes; Transformed Cell Line; Ubiquitin; Ubiquitin-Conjugating Enzymes; Ubiquitination; Viral; Viral Genes; activating transcription factor; base; cell immortalization; cell transformation; cytokine; multicatalytic endopeptidase complex; mutant; novel; protein degradation; protein function; therapy design; transcription factor; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): Human T cell leukemia virus type I (HTLV-I) is linked to the genesis of adult T cell leukemia (ATL), an aggressive CD4+ T cell malignancy. Tax is an oncoprotein encoded by the HTLV-I genome that regulates viral and cellular gene expression. Tax promotes cell transformation, in part, by activating the NF-kB/Rel transcription factor family. Tax requires NF-kB for the immortalization of primary T cells and HTLV-I transformed cells are dependent on NF-kB for their survival, thereby providing a strong rationale for studying the mechanisms used by Tax to activate NF-kB. Tax activates NF-kB by promoting persistent IkB kinase (IKK) activation although the mechanisms are poorly understood. Our supporting studies indicate that polyubiquitination is a key post- translational regulator of Tax activation of NF-kB. Tax activation of NF-kB correlates with ubiquitin-dependent relocalization of IKK to the Golgi apparatus. Tax is polyubiquitinated via Lys 63-linked ubiquitin chains and requires the ubiquitin conjugating enzyme Ubc13 for Tax ubiquitination and NF-kB activation. Ubiquitination of Tax does not promote its degradation, but rather regulates its interaction with the IKK regulatory subunit IKKg. In addition, we have determined that the Tax interacting cellular protein TAX1BP1 is a key negative regulator of cytokine-mediated NF-kB signaling by functioning as an essential subunit for the ubiquitin-editing enzyme A20. We hypothesize that Tax targets TAX1BP1 as part of a mechanism to promote persistent NF-kB activation. In this proposal, we will further investigate how ubiquitination regulates the targeting of Tax and IKK into the Golgi. We will also further delineate the requirements and the identification of host factors regulating Tax ubiquitination. Finally, we will determine the mechanisms used by Tax to inactivate TAX1BP1 and the A20 ubiquitin-editing complex. Our objectives for this proposal will be satisfied by completion of the following specific aims: (1) Determine the mechanisms of Tax-mediated relocalization of IKK; (2) investigate the molecular determinants of Tax ubiquitination and NF-kB activation and (3) determine the role of Tax binding to TAX1BP1 in NF-kB activation. These studies will shed light on how a retroviral oncoprotein usurps host ubiquitination/deubiquitination machinery to persistently activate transcription factors that promote cell transformation. PUBLIC HEALTH RELEVANCE: The HTLV-I Tax oncoprotein is a potent activator of the NF-kB/Rel transcription factor family. Tax requires NF-kB for the immortalization of T cells, and NF-kB is also required for the survival of HTLV-1 transformed cell lines. The focus of the proposal is to determine the molecular mechanisms used by Tax to activate NF-kB, specifically we will further establish the determinants of Tax ubiquitination and examine the role of Tax interaction with the cellular protein TAX1BP1.

描述（由申请人提供）：人类T细胞白血病病毒I型（HTLV-I）与成人T细胞白血病（ATL）的发生有关，ATL是一种侵袭性CD4+ T细胞恶性肿瘤。Tax是一种由HTLV-I基因组编码的癌蛋白，可调节病毒和细胞基因表达。税收促进细胞转化，部分是通过激活NF-kB/Rel转录因子家族。Tax需要NF-kB来实现原代T细胞的永生化，HTLV-I转化的细胞依赖NF-kB才能存活，因此为研究Tax激活NF-kB的机制提供了强有力的理论依据。税收通过促进持续IkB激酶（IKK）激活激活NF-kB，尽管机制尚不清楚。我们的支持研究表明，多泛素化是翻译后NF-kB激活的关键调节因子。NF-kB的税收激活与泛素依赖的IKK到高尔基体的重新定位相关。Tax通过Lys 63连接的泛素链被泛素化，并且需要泛素偶联酶Ubc13来实现Tax泛素化和NF-kB激活。Tax的泛素化并不促进其降解，而是调节其与IKK调控亚基IKKg的相互作用。此外，我们已经确定，通过作为泛素编辑酶A20的重要亚基，Tax相互作用的细胞蛋白TAX1BP1是细胞因子介导的NF-kB信号传导的关键负调控因子。我们假设Tax靶向TAX1BP1作为促进NF-kB持续激活机制的一部分。在本研究中，我们将进一步研究泛素化如何调控Tax和IKK进入高尔基体的靶向。我们还将进一步描述调节税收泛素化的宿主因子的要求和识别。最后，我们将确定Tax用来灭活TAX1BP1和A20泛素编辑复合体的机制。通过完成以下具体目标，我们将满足本提案的目标：(1)确定税收介导的IKK再定位机制；(2)研究Tax泛素化和NF-kB活化的分子决定因素；(3)确定Tax与TAX1BP1结合在NF-kB活化中的作用。这些研究将揭示逆转录病毒癌蛋白如何篡夺宿主泛素化/去泛素化机制，持续激活促进细胞转化的转录因子。公共卫生相关性：HTLV-I Tax癌蛋白是NF-kB/Rel转录因子家族的有效激活剂。T细胞的永生化需要NF-kB， HTLV-1转化细胞系的存活也需要NF-kB。该提案的重点是确定税收激活NF-kB的分子机制，特别是我们将进一步确定税收泛素化的决定因素，并研究税收与细胞蛋白TAX1BP1相互作用的作用。