Jain Sudhir, Li Yanna, Patil Sai, Kumar Ashok
Pathology Dept., New York Medical College, Valhalla, NY 10595, USA.
Am J Physiol Cell Physiol. 2007 Jul;293(1):C401-10. doi: 10.1152/ajpcell.00433.2006. Epub 2007 May 2.
Angiotensinogen (AGT) is the precursor of one of the most important vasoactive hormone angiotensin II and this gene locus is associated with human essential hypertension. AGT is an acute phase protein and its gene expression is regulated by IL-6. Previous studies have identified three potential STAT-3 binding sites (APREs) located between -160 and -280 of the hAGT gene promoter but only APRE-1 (located between -271 and -279) was shown to be a bonafide enhancer for IL-6-induced promoter activity. We show here that APRE-2, located between -236 and -247, is indeed an HNF-1alpha-binding site and plays an important role in basal and IL-6 induced promoter activity of this gene. Our chromatin immunoprecipitation (ChIP) assay shows that HNF-1alpha binds to this region of the hAGT gene promoter and its recruitment is increased in the presence of IL-6 in Hep3B cells. We also show that the promoter activity of a deletion construct containing only 223 bp of the hAGT gene promoter (that contains only APRE-3) is increased after IL-6 treatment. Our ChIP assay shows that IL-6 treatment recruits STAT-3 to APRE-3 and suggests that this is also an IL6 responsive element. We have previously shown that GR binds to the proximal promoter of the hAGT gene. Since GR physically interacts with STAT-3, we propose that transcription factors GR, STAT-3, and HNF-1alpha that bind to the nucleotide sequence located between -160 and -280 of the hAGT gene promoter are responsible for IL-6 induced promoter activity of this gene.
血管紧张素原（AGT）是最重要的血管活性激素之一血管紧张素II的前体，该基因位点与人类原发性高血压相关。AGT是一种急性期蛋白，其基因表达受白细胞介素-6（IL-6）调控。先前的研究已确定在hAGT基因启动子的-160至-280之间有三个潜在的信号转导和转录激活因子3（STAT-3）结合位点（急性期反应元件，APREs），但只有APRE-1（位于-271至-279之间）被证明是IL-6诱导的启动子活性的真正增强子。我们在此表明，位于-236至-247之间的APRE-2实际上是肝细胞核因子1α（HNF-1α）结合位点，并在该基因的基础及IL-6诱导的启动子活性中起重要作用。我们的染色质免疫沉淀（ChIP）分析表明，HNF-1α与hAGT基因启动子的该区域结合，并且在Hep3B细胞中存在IL-6的情况下其募集增加。我们还表明，仅包含hAGT基因启动子223 bp（仅包含APRE-3）的缺失构建体的启动子活性在IL-6处理后增加。我们的ChIP分析表明，IL-6处理将STAT-3募集至APRE-3，并表明这也是一个IL-6反应元件。我们先前已表明糖皮质激素受体（GR）与hAGT基因的近端启动子结合。由于GR与STAT-3发生物理相互作用，我们提出，与hAGT基因启动子-160至-280之间的核苷酸序列结合的转录因子GR、STAT-3和HNF-1α负责该基因的IL-6诱导的启动子活性。
