Function of Hepatocyte-enriched Transcription Factors

肝细胞富集转录因子的功能

• 批准号: 6558929
• 负责人: FRANK GONZALEZ
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6558929
• 关键词: animal genetic material tag; chemical carcinogen; cytochrome P450; developmental genetics; enhancer binding protein; enzyme activity; enzyme induction /repression; gene expression; gene mutation; genetic promoter element; genetic regulation; genetically modified animals; laboratory mouse; liver cells; liver function; northern blottings; toxin metabolism; transcription factor; western blottings

Xenobiotic-metabolizing enzymes are responsible for metabolism and inactivation of all clinically used drugs. They are also involved in the metabolic activation or inactivation of toxins, mutagens and chemical carcinogens. Marked differences in levels of expression of these enzymes have been found in humans and these differences could contribute to interindividual differences in sensitivities to drugs and carcinogens. Variable gene expression could account for some differences in levels of expression of xenobiotic-metabolizing enzymes. Most of these enzymes are expressed in the liver and their genes are under control of different hepatocyte transcription factors. Several families of transcription factors are preferentially expressed in the liver and control liver-specific gene expression. Typically, in vitro techniques, including transfections of reporter gene constructs and DNA binding assays, are used to study gene regulation. However, it is difficult to directly demonstrate that results obtained using in vitro studies actually reflect gene expression in the intact animal. Studies to determine whether hepatocyte-enriched factors are involved in regulating gene expression in vivo can be done by using gene knockouts to disrupt expression of transcription factors and then determine the effects of transcription factor loss on target gene expression. To investigate the role of liver-enriched transcription factors in control of P450 gene expression and expression of other genes involved in liver function, null mice are being produced. Conditional gene disruption is required since embryonic disruption of transcription factor genes frequently results in embryonic lethality or early neonatal death. Conditional-null mice produced using the Cre-LoxP method were developed for the transcription factors HNF-1alpha, HNF-4alpha and C/EBPalpha. Phenotypes were observed and gene expression patterns determined using Northern blot and Western blot analyses. The data indicate that mice lacking expression of these transcription factors develop severe phenotypes including diabetes, dwarfism, hyperbilirubinemia, hypercholestemia and hypolipidemia.

异生素代谢酶负责所有临床使用药物的代谢和失活。它们还参与毒素、诱变剂和化学致癌剂的代谢激活或失活。在人类中发现这些酶的表达水平存在显着差异，这些差异可能导致个体间对药物和致癌物敏感性的差异。可变的基因表达可以解释外源代谢酶表达水平的一些差异。大多数这些酶在肝脏中表达，它们的基因受不同肝细胞转录因子的控制。几个转录因子家族优先在肝脏中表达并控制肝脏特异性基因的表达。通常，体外技术，包括报告基因构建体的转染和 DNA 结合测定，用于研究基因调控。然而，很难直接证明体外研究获得的结果实际上反映了完整动物中的基因表达。确定肝细胞富集因子是否参与体内基因表达调节的研究可以通过使用基因敲除破坏转录因子的表达，然后确定转录因子丢失对靶基因表达的影响来完成。为了研究富含肝脏的转录因子在控制 P450 基因表达和涉及肝功能的其他基因表达中的作用，正在生产无效小鼠。需要条件性基因破坏，因为转录因子基因的胚胎破坏经常导致胚胎致死或新生儿早期死亡。使用 Cre-LoxP 方法产生的条件无效小鼠是针对转录因子 HNF-1α、HNF-4α 和 C/EBPα 开发的。使用Northern印迹和Western印迹分析观察表型并确定基因表达模式。数据表明，缺乏这些转录因子表达的小鼠会出现严重的表型，包括糖尿病、侏儒症、高胆红素血症、高胆固醇血症和低脂血症。