CCAAT/enhancer-binding proteins regulate expression of the human steroidogenic acute regulatory protein (StAR) gene
CCAAT/enhancer-binding proteins regulate expression of the human steroidogenic acute regulatory protein (StAR) gene
复制标题
DOI：
10.1074/jbc.274.37.26591
复制
发表时间：
1999-09-10
影响因子：
4.8
通讯作者：
Strauss, JF
中科院分区：
文献类型：
--
作者：
Christenson, LK;Johnson, PF;Strauss, JF
两个假定的CCAAT/增强子结合蛋白（C/EBP）响应元件被确定在近端启动子的人类固醇生成急性调节蛋白（星星）基因，编码一个关键的蛋白调节类固醇激素的合成。C/EBP α和β的表达增加了COS-1和HepG 2细胞中星星启动子的活性。将C/EBP α或-β和类固醇生成因子1（一种cAMP调节星星表达所需的转录因子）共转染到COS-1中，增强了8-溴腺苷3 '：5'-环一磷酸（8-Br-cAMP）刺激的启动子活性。当假定的C/EBP响应元件被单独或一起突变时，导致人颗粒体-叶黄素细胞中的基础星星启动子活性显著下降，但8-Br-cAMP对启动子活性的倍数刺激不受影响。重组C/EBP α和β与两个鉴定的序列结合，但不与突变元件结合。人颗粒体-叶黄素细胞核提取物也结合这些元素，但不结合突变序列。针对C/EBP β的抗体，而不是C/EBP α，使与更远端元件相关的核蛋白复合物超移。由核提取物与近端元件形成的复合物不被任一抗体超移。Western blot分析显示，在人颗粒蛋白细胞核提取物中存在C/EBPa和C/EBP β。8-Br-cAMP处理使C/EBP β水平上调3倍。我们的研究证明了C/EBP β以及尚未鉴定的蛋白质在星星基因表达调控中的作用，这些蛋白质可以与C/EBP反应元件结合，并提出了C/EBP β参与cAMP调控星星基因转录的机制。
Two putative CCAAT/enhancer-binding protein (C/EBP) response elements were identified in the proximal promoter of the human steroidogenic acute regulatory protein (StAR) gene, which encodes a key protein-regulating steroid hormone synthesis. Expression of C/EBP alpha and -beta increased StAR promoter activity in COS-l and HepG2 cells. Cotransfection of C/EBP alpha or -beta and steroidogenic factor 1, a transcription factor required for cAMP regulation of StAR expression, into COS-1 augmented 8-bromoadenosine 3':5'-cyclic monophosphate (8-Br-cAMP)-stimulated promoter activity. When the putative C/EBP response elements were mutated, individually or together, a pronounced decline in basal StAR promoter activity in human granulosa-lutein cells resulted, but the fold stimulation of promoter activity by 8-Br-cAMP was unaffected. Recombinant C/EBP alpha and -beta bound to the two identified sequences but not the mutated elements. Human granulosa-lutein cell nuclear extracts also bound these elements but not the mutated sequences. An antibody to C/EBP beta, but not C/EBP alpha, supershifted the nuclear protein complex associated with the more distal element. The complex formed by nuclear extracts with the proximal element was not supershifted by either antibody. Western blot analysis revealed the presence of C/EBPa and C/EBP beta in human granulosalutein cell nuclear extracts. C/EBP beta levels were up-regulated 3-fold by 8-Br-cAMP treatment. Our studies demonstrate a role for C/EBP beta as well as yet to be identified proteins, which can bind to C/EBP response elements, in the regulation of StAR gene expression and suggest a mechanism by which C/EBP beta participates in the cAMP regulation of StAR gene transcription.