Synergistic interactions between transcription factors control expression of the apolipoprotein AI gene in liver cells.
Synergistic interactions between transcription factors control expression of the apolipoprotein AI gene in liver cells.
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转录因子之间的协同相互作用控制载脂蛋白 AI 基因在肝细胞中的表达。
DOI：
10.1128/mcb.11.2.677-687.1991
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发表时间：
1991
影响因子：
5.3
通讯作者：
Karathanasis,SK
中科院分区：
文献类型：
--
作者：
Widom,RL;Ladias,JA;Kouidou,S;Karathanasis,SK
编码载脂蛋白AI（apoAI）的基因主要在肝脏和肠道中表达，apoAI是一种参与血浆中胆固醇和其他脂质转运的血浆蛋白。本实验室的前期工作表明，人apoAI基因5′侧翼区的不同顺式作用元件控制其在人肝癌细胞（HepG 2）和结肠癌细胞（Caco-2）中的表达。肝细胞特异性表达由相对于apoAI基因转录起始位点（+1）的−256至−41 DNA区域内的元件介导。在这项研究中，发现-222到-110 apoAI基因区域对于在HepG 2细胞中表达是必要的和足够的。还发现该DNA区域作为强有力的肝细胞特异性转录增强子发挥作用。凝胶阻滞和DNA酶I保护实验表明，HepG 2细胞含有与该增强子内的特定位点结合的蛋白质，即位点A（−214至−192）、B（−169至−146）和C（−134至−119）。定点诱变，防止这些蛋白结合到个人或这些网站的不同组合，然后通过这些突变体在HepG 2细胞中的功能分析表明，蛋白结合到这些网站中的任何一个在没有结合到其他是不足以表达。以任何组合与这些位点中的任何两个结合足以仅用于低水平的表达。与所有三个位点的结合对于最大表达是必不可少的。这些结果表明，肝细胞中的apoAI基因的转录活性依赖于与其增强子结合的转录因子之间的协同相互作用。
The gene coding for apolipoprotein AI (apoAI), a plasma protein involved in the transport of cholesterol and other lipids in the plasma, is expressed predominantly in liver and intestine. Previous work in our laboratory has shown that differentcis-acting elements in the 5′-flanking region of the human apoAI gene control its expression in human hepatoma (HepG2) and colon carcinoma (Caco-2) cells. Hepatocyte-specific expression is mediated by elements within the −256 to −41 DNA region relative to the apoAI gene transcription start site (+1). In this study it was found that the −222 to −110 apoAI gene region is necessary and sufficient for expression in HepG2 cells. It was also found that this DNA region functions as a powerful hepatocyte-specific transcriptional enhancer. Gel retardation and DNase I protection experiments showed that HepG2 cells contain proteins that bind to specific sites, sites A (−214 to −192), B (−169 to −146), and C (−134 to −119), within this enhancer. Site-directed mutagenesis that prevents binding of these proteins to individual or different combinations of these sites followed by functional analysis of these mutants in HepG2 cells revealed that protein binding to any one of these sites in the absence of binding to the others was not sufficient for expression. Binding to any two of these sites in any combination was sufficient for only low levels of expression. Binding to all three sites was essential for maximal expression. These results indicate that the transcriptional activity of the apoAI gene in liver cells is dependent on synergistic interactions between transcription factors bound to its enhancer.