Serum response elements activate and cAMP responsive elements inhibit expression of transcription factor Egr-1 in synovial fibroblasts of rheumatoid arthritis patients.
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.
Department of Rheumatology and Clinical Immunology, University Hospital Freiburg, Germany.
W K
WK
Aicher
A
A
Dinkel
B
B
Grimbacher
C
C
Haas
E V
EV
Seydlitz-Kurzbach
H H
HH
Peter
H
H
Eibel
D001172:Arthritis, Rheumatoid / Q000235:genetics*; D015415:Biomarkers; D002461:Cell Line, Transformed; D000242:Cyclic AMP / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D051766:Early Growth Response Protein 1; D005260:Female; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation; D006801:Humans; D017874:Immediate-Early Proteins; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis / Q000235:genetics; D020218:Response Elements; D026362:Serum Response Factor; D013582:Synovial Fluid / Q000166:cytology; D013583:Synovial Membrane / Q000166:cytology*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
D015415:Biomarkers; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D016760:Proto-Oncogene Proteins c-fos; D026362:Serum Response Factor; D014157:Transcription Factors; D000242:Cyclic AMP