Regulation of Liver-Specific Gene Expression

描述（由申请人提供）：肝细胞核因子4 （HNF4）是核受体（NR）配体依赖性转录因子超家族中高度保守的成员。它是一种重要的基因，在早期发育中起着至关重要的作用，在成人的肝脏、肾脏、胰腺和肠道中也起着至关重要的作用。HNF4与包括糖尿病和血友病在内的几种人类疾病直接相关，与动脉粥样硬化和癌症等其他疾病间接相关。HNF4是肝脏中最丰富的转录因子之一。尽管已经确定了许多与HNF4相关的靶基因，但最近的基因组规模分析表明，还有更多的基因有待确定。例如，最近的研究结果表明，通过选择性剪接和启动子的使用，HNF4的不同亚型的靶基因可能存在差异。此外，已知HNF4是一种重度磷酸化蛋白，并对各种细胞内和细胞外信号作出反应；然而，只有少数磷酸基已被绘制和充分表征。最后，除了在中间代谢中发挥作用外，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，我们提出以下三个具体目标：1)利用基因组尺度分析和体内小鼠模型研究HNF4亚型的功能差异，确定新的HNF4靶基因；2)研究酪氨酸磷酸化在HNF4功能中的作用；3)研究HNF4在调节细胞周期中的作用。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。该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，对于开发合适的治疗方法至关重要。

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.