孤儿核受体hB1F/hLRH-1铰链区一个保守结构域对其转录功能的抑制作用(英文)  

Characterization of a Strong Repression Domain in the Hinge Region of Orphan Nuclear Receptor hB1F/hLRH-1

作　　者：徐平龙[1] 单仕芳[1] 孔玉英[1] 谢幼华[1] 汪垣[1] 

机构地区：[1]中国科学院上海生命科学研究院生物化学与细胞生物学研究所分子生物学国家重点实验室,上海200031

出　　处：《生物化学与生物物理学报》2003年第10期909-916,共8页

基　　金：国家自然科学基金 (No .3 0 10 0 0 88) ;国家高技术研究与发展计划 ( 863计划 ) (No .2 0 0 1AA2 2 12 61) ;科技部基础研究计划 (No .G19990 5 410 5 );上海科委启明星 (No.0 1QA14 0 46)项目资助~~

摘　　要：孤儿核受体hB1F(NR5A2 ,也称之为LRH 1、CPF或FTF)在胆汁酸合成代谢、乙肝病毒基因和部分肝特异性基因表达的调控中起着重要的作用。为理解hB1F激活转录的分子机制 ,对其铰链区潜在的功能结构域进行了分析。利用GAL4 DBD融合的hB1F缺失片段所进行的报告基因分析 ,发现了一个位于铰链区的强烈抑制hB1F反式激活能力的结构域。该结构域核心残基的定点突变导致了hB1F反式激活能力的显著上升 ,而且明显地增强hB1F对乙肝病毒增强子II 核心启动子的转录激活能力。生物信息学分析显示该结构域不存在明显的二级结构 ,但有意思的是 ,其氨基酸序列在核受体FTZ F1亚家族的成员中高度保守 ,且不见于其他蛋白质中。转染分析发现 ,该结构域的抑制活性存在于测试的五个不同细胞株中 ,但抑制的强度表现出明显差异。半定量RT PCR分析表明 ,与SF 1不同 ,该结构域抑制转录活性的强度与潜在的结合因子DP10 3的表达水平之间没有相关性。共转染实验还表明 ,参与hB1F转录活性调控的辅激活子SRC 1和辅抑制子SMRT与该抑制作用不直接相关。实验结果提示 ,孤儿核受体hB1F转录活性可能存在一种新的调控机制。Human hepatitis B virus enhancer II B1 binding factor (hB1F,also known as NR5A2, LRH-1, FTF or CPF) is an orphan nuclear receptor and belongs to the fushi tarazu factor I (FTZ-F1) subfamily. It plays important roles in the transcriptional regulation of a number of genes involved in bile acid biosynthesis pathway, hepatitis B virus (HBV) replication and liver specific regulatory network. Like other nuclear receptors, hB1F is composed of modular functional domains. We characterized a domain in its hinge region that imposes a strong repression on the transcriptional activity of hB1F, which is important for the function of hB1F on regulating the activity of HBV enhancer II/core promoter. Mutations of the core residues in this domain abrogate the repression. Bioinformatic analysis reveals that the amino acid sequence of this region is highly conserved only among members of the FTZ-F1 subfamily. The repression is observed in five cell lines tested, while the degree of the repression varies greatly, which does not parallel with the expression level of the DEAD box protein of 130 kD (DP103), a potential interacting protein of a homologous domain in the steroidogenic factor 1 (SF-1). Moreover, the repression is not affected by the silencing mediator for retinoic acid receptor and thyroid hormone receptor (SMRT) and steroid receptor coactivator 1 (SRC-1). Collectively, these data suggest a novel regulatory mechanism for the transcriptional activity of hB1F.

关 键 词：孤儿核受体 铰链区 抑制结构域 乙肝病毒增强子II 核心启动子 

分 类 号：R346[医药卫生—基础医学]