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）（一种侵袭性 CD4+ T 细胞恶性肿瘤）的发生有关。 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。 Tax 部分通过激活 NF-kB/Rel 转录因子家族来促进细胞转化。 Tax需要NF-kB来实现原代T细胞的永生化，并且HTLV-I转化细胞的生存依赖于NF-kB，从而为研究Tax激活NF-kB的机制提供了强有力的理论依据。 Tax 通过促进 IkB 激酶 (IKK) 持续激活来激活 NF-kB，但其机制尚不清楚。我们的支持研究表明多聚泛素化是 NF-kB Tax 激活的关键翻译后调节因子。 NF-kB 的税务激活与 IKK 泛素依赖性重定位至高尔基体相关。 Tax 通过 Lys 63 连接的泛素链进行多泛素化，需要泛素结合酶 Ubc13 来实现 Tax 泛素化和 NF-kB 激活。 Tax 的泛素化不会促进其降解，而是调节其与 IKK 调节亚基 IKKg 的相互作用。此外，我们还确定，Tax 相互作用细胞蛋白 TAX1BP1 作为泛素编辑酶 A20 的重要亚基，是细胞因子介导的 NF-kB 信号转导的关键负调节因子。我们假设 Tax 以 TAX1BP1 为目标，作为促进 NF-kB 持续激活机制的一部分。在本提案中，我们将进一步研究泛素化如何调节 Tax 和 IKK 靶向高尔基体。我们还将进一步明确规范税收泛素化的要求和宿主因素的识别。最后，我们将确定 Tax 用于灭活 TAX1BP1 和 A20 泛素编辑复合体的机制。我们的提案目标将通过完成以下具体目标来实现： (1) 确定 IKK 税收介导的重新定位机制； (2) 研究 Tax 泛素化和 NF-kB 激活的分子决定因素，(3) 确定 Tax 与 TAX1BP1 结合在 NF-kB 激活中的作用。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，以持续激活促进细胞转化的转录因子。公共健康相关性：HTLV-I Tax 癌蛋白是 NF-kB/Rel 转录因子家族的有效激活剂。 Tax 需要 NF-kB 来实现 T 细胞的永生化，HTLV-1 转化细胞系的存活也需要 NF-kB。该提案的重点是确定Tax激活NF-kB的分子机制，具体来说，我们将进一步建立Tax泛素化的决定因素，并研究Tax与细胞蛋白TAX1BP1相互作用的作用。