Regulation of Liver-Specific Gene Expression

描述(申请人提供)：肝细胞核因子4(HNF4)是配体依赖的转录因子核受体(NR)超家族中高度保守的成员。它是一种必不可少的基因，在早期发育中起着关键作用，在成人的肝脏、肾脏、胰腺和肠道中也是如此。HNF4与几种人类疾病直接相关，包括糖尿病和血友病，并间接与其他疾病相关，包括动脉粥样硬化和癌症。HNF4是肝脏中含量最丰富的转录因子之一。虽然已经确定了HNF4的许多靶基因，但最近的基因组规模分析表明，还有更多的基因尚未确定。例如，最近的结果表明，由选择性剪接和启动子使用产生的不同亚型HNF4的靶基因可能存在差异。此外，众所周知，HNF4是一种高度磷酸化的蛋白质，可以对多种细胞内外信号做出反应；然而，只有几个亚磷酸盐被定位并充分表征。最后，除了它在中间代谢中的作用外，越来越多的证据表明，HNF4也可能在调节细胞周期中发挥作用。为了解决这些问题，我们提出了以下三个具体目标：1)利用基因组水平的分析和体内小鼠模型来研究HNF4亚型的功能差异；2)研究酪氨酸磷酸化在HNF4功能中的作用；以及3)研究HNF4在细胞周期调节中的作用。拟议的实验将使用广泛的现代技术继续研究HNF4在肝脏特异性基因表达中的作用。这一结果将进一步加深我们对组织特异性基因调控机制的理解。它们还将提供有关与HNF4有关的各种人类疾病的宝贵信息。最后，作为潜在的药物靶点，更全面地了解HNF4靶向的基因，以及靶向HNF4的信号通路，将对开发适当的治疗方法至关重要。 项目简介：我们的研究与公共健康相关，因为它试图破译基因在肝脏和肠道中启动的机制。这不仅对于了解糖尿病、肥胖症、动脉粥样硬化和癌症等疾病的原因至关重要，而且对于设计治疗这些疾病的新疗法也至关重要。

DESCRIPTION (provided by applicant): Hepatocyte nuclear factor 4 (HNF4) is a highly conserved member of the nuclear receptor (NR) superfamily of ligand-dependent transcription factors. It is an essential gene, playing a critical role in early development, as well as in the adult in the liver, kidney, pancreas and intestine. HNF4 has been directly linked to several human diseases including diabetes and hemophilia and indirectly linked to others including atherosclerosis and cancer. HNF4 is one of the most abundant transcription factors in the liver. Whereas many target genes have been identified for HNF4, recent genome-scale analyses indicate that there are many more yet to be identified. Recent results indicate, for example, that there may be differences in the target genes of the different isoforms of HNF4 generated by alternative splicing and promoter usage. Furthermore, HNF4 is known to be a heavily phosphorylated protein and to respond to a variety of intra- and extracellular signals; however, only a few of the phosphosites have been mapped and fully characterized. Finally, in addition to its role in intermediary metabolism, there is a growing body of evidence indicating that HNF4 may also play a role in regulating the cell cycle. In order to address these issues, we propose the following three Specific Aims: 1) Identify new target genes for HNF4 using genome-scale analysis and an in vivo mouse model to examine the functional differences in HNF4 isoforms; 2) Investigate the role of tyrosine phosphorylation in HNF4 function; and 3) Investigate the role of HNF4 in regulating the cell cycle. The proposed experiments will continue the investigation of the role of HNF4 in liver-specific gene expression using a broad array of modern techniques. The results will further our understanding of the mechanisms of tissue-specific gene regulation. They will also provide invaluable information regarding a variety of human diseases that are linked to HNF4. Finally, as a potential drug target, a more comprehensive knowledge of the genes targeted by HNF4, as well as the signaling pathways that target HNF4, will be essential to developing appropriate therapies. Project Narrative: Our research is relevant to public health because it attempts to decipher the mechanisms by which genes are turned on in the liver and gut. This is critical not only for understanding the causes of diseases such as diabetes, obesity, atherosclerosis and cancer, but also for designing new therapies to treat those diseases.