Regulation of Transcriptional Elongation by HIV-1 TAT

HIV-1 TAT 对转录延伸的调节

• 批准号: 7190551
• 负责人: QIANG ZHOU
• 金额: $ 34.12万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-08-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7190551
• 关键词: Affect; Affinity; Binding; Biological Assay; Catalytic Domain; Cell Differentiation process; Cell Lineage; Cell physiology; Cells; Cleaved cell; Complement; Complex; Condition; Coupled; Cyclin-Dependent Kinases; Cyclins; DNA; DNA Synthesis Inhibition; Data; Differentiation Inducer; Disruption; Dissociation; Elongation Factor; Family; Future; G1 Arrest; Gene Expression; Genetic Transcription; Goals; HIV; HIV-1; Helper-Inducer T-Lymphocyte; Hexamethylene Bisacetamide; Human; In Vitro; Investigation; Laboratories; Mediating; Mediation; Messenger RNA; Modeling; Molecular; Mutagenesis; Nuclear; Phase; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphotransferases; Play; Polymerase; Positive Transcriptional Elongation Factor B; Process; Properdin; Protein Dephosphorylation; Protein phosphatase; Proteins; RNA; RNA Interference; RNA Polymerase II; Reaction; Regulation; Reporting; Role; Signal Pathway; Small Nuclear RNA; Small Nuclear Ribonucleoproteins; Staging; Stress; Structure; Substrate Specificity; System; Tars; Transcription Elongation; Transcriptional Regulation; Undifferentiated; Viral; biological adaptation to stress; cell growth; cell type; controlled release; cyclin T1; factor EF-P; improved; in vivo; inhibitor/antagonist; negative elongation factor; prevent; programs; protein phosphatase inhibitor-1; reconstitution; research study; scaffold; tat Protein; three dimensional structure; transcription factor

DESCRIPTION (provided by applicant): The human transcription elongation factor P-TEFb, consisting of a CDK9/cyclin T heterodimer, promotes both general and HIV-specific elongation by phosphorylating RNA polymerase II and overcoming pausing by negative elongation factors. It is also a co-factor for the HIV-1 Tat protein, whose recruitment of P-TEFb to the nascent viral mRNA is essential for HIV replication. The PI's laboratory has recently identified the 7SK snRNA and hexamethylene bisacetamide (HMBA)-inducible protein 1 (HEXlM1) as two P-TEFb-associated nuclear factors. Their interactions with P-TEFb require the phosphorylation of P-TEFb on possibly the conserved CDK9 T-loop. P-TEFb loses its kinase and transcriptional activities when associated with 7SK and HEXlM1 to form the 7SK snRNP. With 7SK bridging the HEXlM1:P-TEFb interaction, HEXIM1 inhibits the P-TEFb kinase. Both 7SK and HEXIM1 are dissociated from P-TEFb when cells respond to stresses caused by a global inhibition of transcription. Consistent with its inhibition of PTEFb, HEXlM1 strongly suppresses HIV-1 transcription in vivo. Our data support a model in which the phosphorylated P-TEFb is targeted for inhibition by the coordinated actions of HEXlM1 and 7SK. This proposal seeks to elucidate the mechanism by which HEXlM1/7SK inhibit the P-TEFb kinase through structure-function analyses of the 7SK snRNP. Experiments will also be performed to investigate whether 7SK plays a direct, active role in the inhibitory action beyond its mediation of the HEXlM1:P-TEFb binding. In addition, the effect of reducing HEXlM1 expression by RNAi on CTD phosphorylation and HIV-1 transcription will be analyzed. Because HEXlM1 is induced by HMBA, a potent inducer of cell differentiation, the roles of HEXlM1 and P-TEFb in controlling this key process will be examined. The preliminary data so far implicate a role of protein phosphatase-1 (PP-1) in activating HIV-1 transcription and dissociating 7SK/HEXIM1 from P-TEFb in vitro. A major effort will be devoted to the investigation of a possible role of PP-1 in regulating the stress-induced disruption of the 7SK snRNP and activation of P-TEFb in vivo. Our ultimate goal is to elucidate the molecular mechanisms controlling eukaryotic gene expression at the stage of elongation. Investigation of how the activity of P-TEFb, a key elongation factor and Tat co-factor, is regulated by HEXlM1/7SK and how this regulation affects HIV-1 transcription and cellular gene expression will be very informative in this regard.

描述（由申请人提供）：人类转录延伸因子P-TEFb，由CDK9/cyclin T异源二聚体组成，通过磷酸化RNA聚合酶II和克服负延伸因子的暂停来促进一般和hiv特异性延伸。它也是HIV-1 Tat蛋白的辅助因子，其向新生病毒mRNA募集P-TEFb对HIV复制至关重要。PI的实验室最近确定了7SK snRNA和六亚甲基双乙酰胺（HMBA）诱导蛋白1 （HEXlM1）是两个p - tefb相关的核因子。它们与P-TEFb的相互作用需要P-TEFb在可能保守的CDK9 t环上磷酸化。当P-TEFb与7SK和HEXlM1结合形成7SK snRNP时，会失去其激酶和转录活性。通过7SK桥接HEXlM1:P-TEFb相互作用，HEXIM1抑制P-TEFb激酶。当细胞响应由转录全局抑制引起的应激时，7SK和HEXIM1都与P-TEFb分离。与其抑制PTEFb一致，HEXlM1在体内强烈抑制HIV-1转录。我们的数据支持一个模型，其中磷酸化的P-TEFb被HEXlM1和7SK的协同作用靶向抑制。