Aicher W K, Sakamoto K M, Hack A, Eibel H
Department of Orthopedic Surgery, Research Laboratory University of Tübingen Medical Center, Germany.
Rheumatol Int. 1999;18(5-6):207-14. doi: 10.1007/s002960050086.
The early growth response (Egr)-1 gene encoding a zinc-finger transcription factor is transiently induced in many different cell types upon various differentiation signals. However, in synovial fibroblasts of rheumatoid arthritis patients, Egr-1 is constitutively expressed at high levels, and several genes with Egr-1 binding sites in their promoter regions have been associated with disease progression of RA. We analyzed the control of Egr-1 transcription by characterizing those regulatory elements in the Egr-1 promoter that induce Egr-1 expression in fibroblasts. Using reporter gene assays and deletion mutants of the Egr-1 promoter we could demonstrate that Egr-1 transcription is mainly activated by a single serum response element, whereas other transcription factor binding sites, including binding sites for AP-1 or Egr-1, were found to play a minor role. Furthermore, we identified a novel regulatory element in the human Egr-1 promoter similar to a NF kappa-B binding site. Deletion of this element enhanced Egr-1 promoter activity in 3T3 but not in L929 fibroblasts. Stimulation by phorbolester induced only transient Egr-1 expression in 3T3 fibroblasts but a extended expression of Egr-1 in L929 cells. These data suggest that in fibroblasts the most proximal serum response element in the Egr-1 promoter represents the major activation site, whereas binding of the NFkB-like factor may serve as negative regulatory signal for Egr-1 transcription in fibroblasts.
编码锌指转录因子的早期生长反应（Egr）-1基因在多种不同细胞类型中，受到各种分化信号刺激后会被短暂诱导表达。然而，在类风湿性关节炎患者的滑膜成纤维细胞中，Egr-1呈组成性高水平表达，并且在其启动子区域具有Egr-1结合位点的几个基因已被证明与类风湿性关节炎的疾病进展相关。我们通过对Egr-1启动子中那些能在成纤维细胞中诱导Egr-1表达的调控元件进行表征，来分析Egr-1转录的调控机制。利用报告基因检测和Egr-1启动子的缺失突变体，我们证实Egr-1转录主要由单个血清反应元件激活，而其他转录因子结合位点，包括AP-1或Egr-1的结合位点，作用较小。此外，我们在人类Egr-1启动子中鉴定出一个类似于NF-κB结合位点的新型调控元件。缺失该元件会增强3T3细胞而非L929成纤维细胞中的Egr-1启动子活性。佛波酯刺激在3T3成纤维细胞中仅诱导短暂的Egr-1表达，而在L929细胞中诱导Egr-1的持续表达。这些数据表明，在成纤维细胞中，Egr-1启动子中最靠近近端的血清反应元件是主要的激活位点，而类NF-κB因子的结合可能作为成纤维细胞中Egr-1转录的负调控信号。
