Defective ureagenesis in mice carrying a liver-specific disruption of he-datocvte nuclear factor 4α (HNF4α) -: HNF4α regulates ornithine transcarbamylase in vivo
Defective ureagenesis in mice carrying a liver-specific disruption of he-datocvte nuclear factor 4α (HNF4α) -: HNF4α regulates ornithine transcarbamylase in vivo
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DOI：
10.1074/jbc.m203126200
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发表时间：
2002-07-12
影响因子：
4.8
通讯作者：
Gonzalez, FJ
中科院分区：
文献类型：
--
作者：
Inoue, Y;Hayhurst, GP;Gonzalez, FJ
肝细胞核因子 4α (HNF4α) 调节许多优先在肝脏中表达的基因的表达。 HNF4α缺失小鼠在胚胎发生过程中死亡，无法分析其在成年体内的功能。为了解决这个问题，我们培育了肝脏特异性 HNF4α 缺失小鼠。缺乏肝脏 HNF4α 表达的小鼠表现出血清氨增加和血清尿素减少。尿素生成的这种破坏可以通过肝鸟氨酸转氨甲酰酶（OTC）的表达和活性显着降低来解释。为了确定参与小鼠 OTC 基因转录调控的分子机制，对 OTC 启动子区域进行了分析。序列分析揭示了小鼠 OTC 启动子区域中存在两个假定的 HNF4α 结合位点。通过使用瞬时转染分析，确定高水平的启动子活性依赖于 HNF4α 结合位点和 HNF4α 的表达。此外，发现近端 HNF4α 结合位点比远端更重要。一种用于反式激活 OTC 启动子。这些数据表明，HNF4α 通过直接调节体内 OTC 基因对于尿素稳态至关重要。
Hepatocyte nuclear factor 4alpha (HNF4alpha) regulates the expression of many genes preferentially expressed in liver. HNF4alpha-null mice die during embryogenesis precluding the analysis of its function in the adult. To circumvent this problem, liver-specific HNF4alpha-null mice were produced. Mice lacking hepatic HNF4alpha expression exhibited increased serum ammonia and reduced serum urea. This disruption in ureagenesis may be explained by a marked decrease in expression and activity of hepatic ornithine transcarbamylase (OTC). To determine the molecular mechanisms involved in transcriptional regulation of the mouse OTC gene, the OTC promoter region was analyzed. Sequence analysis revealed the presence of two putative HNF4alpha-binding sites in the mouse OTC promoter region. By using transient transfection analysis, it was established that high levels of promoter activity were dependent on both HNF4alpha-binding sites and the expression of HNF4alpha. Furthermore, the proximal HNF4alpha-binding site was found to be more important than the distal. one for transactivating OTC promoter. These data demonstrate that HNF4alpha is critical for urea homeostasis by direct regulation of the OTC gene in vivo.