Context-specific Functions of CDK8

CDK8 的上下文特定功能

• 批准号: 9002041
• 负责人: Jun-yuan Ji
• 金额: $ 30.64万
• 依托单位: TEXAS A&M UNIVERSITY HEALTH SCIENCE CTR
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-02-25 至 2018-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9002041
• 关键词: Address; Animal Model; Binding Proteins; Biological; Cardiovascular Diseases; Colorectal Cancer; Complex; Cues; Cyclin-Dependent Kinases; DNA Binding; Data; Defect; Development; Diabetes Mellitus; Disease; Drosophila genus; Drosophila melanogaster; Ecdysone; Eukaryota; Fatty acid glycerol esters; Feedback; Gene Expression; Gene Targeting; Genes; Genetic Transcription; Goals; Growth; Health; Homeostasis; Homologous Gene; Human; Insulin; Insulin Signaling Pathway; Larva; Link; Lipids; Malignant Neoplasms; Malignant neoplasm of liver; Mediating; Mediator of activation protein; Metabolism; Modeling; Molecular; Mutate; Nuclear Receptors; Nutrient; Obesity; Organism; Pathway interactions; Phenotype; Phosphorylation; Phosphotransferases; Physiological; Play; Proteins; RNA Polymerase II; RXR; Receptor Signaling; Recruitment Activity; Regulation; Regulatory Element; Research; Risk; Role; Signal Pathway; Signal Transduction; Staging; Sterols; Threonine; Time; Trans-Activators; Transcription Coactivator; Transcriptional Regulation; Up-Regulation; Work; cancer therapy; cancer type; cyclin C; ecdysteroid receptor; in vivo; insulin signaling; leukemia; lipid biosynthesis; lipid metabolism; loss of function mutation; melanoma; mutant; novel; programs; protein function; response; steroid hormone receptor; transcription factor; tumorigenesis

DESCRIPTION (provided by applicant): The highly conserved co-factor Mediator Complex, comprising up to 30 subunits, serves as a molecular bridge between transcriptional activators and the core transcription machinery, and is thought to be required for most RNA polymerase II-dependent transcription. As the only known enzymatic subunit of Mediator complex, CDK8 (Cyclin-Dependent Kinase 8) can either positively or negatively regulate transcription. However, whether CDK8 acts as an activator or repressor at every gene, or whether it acts differently at different classes of genes, is a key unexplored field that would dramatically refine our view of how Mediator facilitates transcription. Furthermore, understanding the function and regulation of CDK8 is critical to elucidate how dysregulation of both CDK8 and its regulatory partner CycC (Cyclin C) contributes to a variety of human cancers. Depletion of CDK8 effectively blocks the growth of melanoma and colorectal cancer, which underscores the centrality of CDK8 in gene expression and demonstrates why CDK8 is considered an attractive and promising target for cancer treatment. Currently, how dysregulation of CDK8-CycC contributes to tumorigenesis is poorly understood. To determine the normal and dysregulated functions of these proteins, it is essential to identify the downstream effectors and upstream regulators of CDK8-CycC. Analyses of function and regulation of CDK8 have been hampered by the lack of phenotypes for CDK8 activity in multicellular organisms. We have solved this challenge by using Drosophila, which provides unparalleled sophistication in manipulating CDK8 activity in vivo. We have recently identified two important downstream transactivators of CDK8, SREBP (Sterol Regulatory Element-Binding Protein) and the EcR (Ecdysteroid Receptor), which play essential roles in regulating lipogenesis and developmental maturation, respectively. Our analyses suggest that CDK8 inhibits SREBP-dependent transcription but activates EcR-activated gene expression. Thus, the objective of this proposal is to determine how CDK8 plays fundamentally different roles in modulating the activities of SREBP and EcR. Specifically, we will elucidate how CDK8 regulates SREBP- and EcR-mediated transcription by determining the molecular mechanism underlying the interactions between CDK8 and both SREBP and EcR, and the effects of SREBP and EcR phosphorylation by CDK8 in vivo. We will also examine the physiological regulation of CDK8-CycC by the insulin-signaling pathway and analyze the role of CDK8 in coordinating lipid homeostasis and developmental timing. This study will significantly advance our understanding of how CDK8 plays distinct roles in lipogenesis and development. Because CDK8 and CycC are well conserved in eukaryotes, the molecular mechanisms that we identify in Drosophila are highly likely to provide working models in human studies. The importance of this project is highlighted by the fact that dysregulation of lipid homeostasis durin development is closely linked to diseases such as diabetes, obesity, cardiovascular diseases, and certain types of cancers.

描述（由申请人提供）：高度保守的共同因子中介复合物，包括多达30个亚基，用作转录激活剂和核心转录机械之间的分子桥，被认为是大多数RNA聚合酶II依赖性转录所必需的。作为介体复合物的唯一已知的酶亚基，CDK8（Cyclin依赖性激酶8）可以正面或负调节转录。但是，CDK8是在每个基因上充当激活因子还是阻遏物，还是在不同类别的基因上的作用不同，是一个关键的未开发领域，它将大大改善我们对介体如何促进转录的看法。此外，了解CDK8的功能和调节对于阐明CDK8及其调节伴侣CYCC（Cyclin c）的失调如何有助于各种人类癌症。 CDK8的耗竭有效地阻断了黑色素瘤和结直肠癌的生长，这突显了CDK8在基因表达中的中心性，并证明了为什么CDK8被认为是癌症治疗的有吸引力且有希望的靶标。当前，CDK8-CYCC的失调如何促进肿瘤发生率很少。为了确定这些蛋白质的正常和失调功能，必须识别CDK8-CYCC的下游效应子和上游调节剂。由于缺乏多细胞生物中CDK8活性的表型，CDK8功能和调节的分析受到了阻碍。我们通过使用果蝇解决了这一挑战，果蝇在操纵CDK8活性时提供了无与伦比的复杂性。我们最近已经确定了CDK8，SREBP（固醇调节元素结合蛋白）和ECR（ecdysteroid受体）的两个重要下游瞬变，它们在调节脂肪生成和发育成熟方面起着重要作用。我们的分析表明，CDK8抑制了SREBP依赖性转录，但激活了ECR激活的基因表达。因此，该提案的目的是确定CDK8在调节SREBP和ECR的活动中扮演根本不同的作用。具体而言，我们将阐明CDK8如何通过确定CDK8与SREBP和ECR之间相互作用的分子机制来调节SREBP和ECR介导的转录，以及SREBP和ECR磷酸化在VIVO中的影响。我们还将通过胰岛素信号途径检查CDK8-CYCC的生理调节，并分析CDK8在协调脂质稳态和发育时机中的作用。这项研究将大大提高我们对CDK8如何在脂肪生成和发育中发挥不同作用的理解。由于CDK8和CYCC在真核生物中是充分保守的，因此我们在果蝇中鉴定的分子机制极有可能在人类研究中提供工作模型。该项目的重要性是通过以下事实强调了脂质稳态发展的失调与糖尿病，肥胖，心血管疾病和某些类型的癌症等疾病密切相关。