CYP2C9是重要的肝代谢酶，对内、外源物的代谢具有重要作用。中介体(Med) 是连接核受体与RNA聚合酶II (Pol-II)的桥梁，在基因调控中发挥重要作用。前期研究发现糖皮质激素诱导下，中介体亚基Med25与糖皮质激素受体GRα结合，促进CYP2C9的转录表达。本项目针对Med25是否是GRα的必要共激活因子参与对CYP2C9的调控这一关键问题，研究Med25对GRα介导的CYP2C9的调控机制及其在肝脏代谢中的作用。通过免疫沉淀、ChIP分析、共聚焦显微镜观察等阐明Med25与GRα相互结合并招募Pol-II；利用基因转录活性分析与基因沉默技术等明确Med25在调控CYP2C9表达及肝脏代谢中的作用；质谱分析确定Med25磷酸化位点并阐明Med25磷酸化的作用。明确Med25是GRα介导的调控CYP2C9过程中必要的共激活因子，为相关代谢疾病的预防与治疗提供可能的药物新靶点。

CYP2C9 is an important hepatic metabolizing enzyme playing vital roles in the metabolism of xenobiotics as well as endogenous compounds. Mediator complex (Med) acts as a molecular bridge interacts with nuclear receptor and RNA polymerase II (Pol-II), which plays an important role in the gene transcription. Our preliminary work shows that Med25, a subunit of Mediator complex, interacts with glucocorticoid receptor α (GRα) and promotes the transcriptional regulation of CYP2C9 expression by glucocorticoid stimulation. This study will focus on the pivotal point whether Med25 is an essential coactivator of GRα involved in the transcriptional regulation of CYP2C9 expression, and investigate the role and mechanism of Med25 in the regulation of CYP2C9 expression and liver metabolism. We will employ many methods such as immunoprecipitation, chromatin immunoprecipitation (ChIP) assay and confocal microscope technologies to demonstrate Med25 interacts with GRα and recruits Pol-II. By gene reporter assay and silencing Med25, we will determine the role of Med25 in the regulation of CYP2C9 expression and liver metabolism. We will further determine the phosphorylation sites of Med25 through mass spectrometric analysis, and clarify the role of phosphorylation of Med25 in the gene regulation. This study will clarify that Med25 is a vital coactivator of GRα involved in the regulation of CYP2C9 expression, and provide a new possible molecular target of prevention and clinical therapy of some related metabolism diseases.