Aicher W K, Dinkel A, Grimbacher B, Haas C, Seydlitz-Kurzbach E V, Peter H H, Eibel H
Department of Rheumatology and Clinical Immunology, University Hospital Freiburg, Germany.
Int Immunol. 1999 Jan;11(1):47-61. doi: 10.1093/intimm/11.1.47.
Analyzing the induction kinetics and promoter elements regulating the expression of the transcription factor Egr-1, we found elevated levels of Egr-1-encoding mRNA in synovial fibroblasts of rheumatoid arthritis (RA) patients when compared to controls. By contrast, synovial lymphocytes and macrophages do not show an elevated Egr-1 transcription. Therefore, the overexpression of Egr-1 may serve as a diagnostic marker to characterize synovial fibroblasts of RA patients. To study the regulatory mechanisms controlling Egr-1 expression we analyzed the function of transcription factor binding sites located in the Egr-1 promoter. Individual transcription factor binding sites within the Egr-1 promoter were specifically mutated and Egr-1 promoter activity was tested using reporter gene constructs. Our experiments demonstrate that serum response elements are the main positive regulators and binding to a cAMP responsive element represents the major negative regulator for Egr-1 expression in synovial fibroblasts. In addition, we functionally defined a new element, which was not yet described in the human Egr-1 promoter and which serves as a second negative regulatory element for Egr-1 expression. Therefore increased serum response factor activity or failure of Egr-1 repressing signals may account for Egr-1 overexpression in RA synovial fibroblasts.
通过分析转录因子Egr-1表达的诱导动力学和调控启动子元件，我们发现，与对照组相比，类风湿关节炎（RA）患者滑膜成纤维细胞中编码Egr-1的mRNA水平升高。相比之下，滑膜淋巴细胞和巨噬细胞未显示Egr-1转录升高。因此，Egr-1的过表达可能作为一种诊断标志物来表征RA患者的滑膜成纤维细胞。为了研究控制Egr-1表达的调控机制，我们分析了位于Egr-1启动子中的转录因子结合位点的功能。Egr-1启动子内的各个转录因子结合位点被特异性突变，并使用报告基因构建体测试Egr-1启动子活性。我们的实验表明，血清反应元件是主要的正调控因子，而与cAMP反应元件的结合是滑膜成纤维细胞中Egr-1表达的主要负调控因子。此外，我们从功能上定义了一个新元件，该元件在人类Egr-1启动子中尚未被描述，并且作为Egr-1表达的第二个负调控元件。因此，血清反应因子活性增加或Egr-1抑制信号失败可能是RA滑膜成纤维细胞中Egr-1过表达的原因。
