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This Article Accepted manuscript (PDF) All Versions of this Article: JME-08-0015v1 41/4/239    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Johansson Haque, K. Articles by Okret, S. Search for Related Content PubMed PubMed Citation Articles by Johansson Haque, K. Articles by Okret, S.

K Johansson Haque, Biosciences and Nutrition, Karolinska Institutet, Stockholm, 141 86 Huddinge, Sweden
E Palanichamy, Biosciences and Nutrition, Karolinska Institutet, Stockholm, Sweden
S Okret, Biosciences and Nutrition, Karolinska Institutet, Stockholm, Sweden

Correspondence: Krishan Johansson Haque, Email: krishan.johansson.haque{at}ki.se

Abstract

Glucocorticoids (GCs) are known to inhibit mitogen-activated protein kinase (MAPK) signaling. This has been suggested to involve induced expression of the MAPK phosphatase 1 (MKP-1), which dephosphorylates and inactivates MAPKs. However, the mechanism for the transcriptional activation by GCs of MKP-1 or the identification of a GC-responsive region in the gene has so far not been described. To identify GC receptor (GR) binding to the human MKP-1 promoter in vivo we used a chromatin immunoprecipitation (ChIP) assay and found GR to bind to a region approximately -1.4 kb upstream of the transcription start site. Using promoter deletion constructs, we identified a GC-responsive region between position -1266 and -1380 bp of the MKP-1 promoter. However, no direct binding of GR to this GC-responsive region was detected in an electrophoretic mobility shift assay (EMSA). Instead we identified binding of CCAAT enhancer-binding protein (C/EBP)β to a region between -1311 to -1304 bp in the MKP-1 promoter by EMSA and ChIP. Furthermore, mutation of the C/EBP binding site resulted in a dramatic loss of GC-inducible reporter gene expression, demonstrating the GC responsiveness of the MKP-1 gene to be located to a binding site for C/EBP in the MKP-1 promoter. Also, given that a GR mutant (GRLS7), incapable of transactivating through glucocorticoid-responsive elements (GREs), still was able to bind to the MKP-1 gene in vivo and induce MKP-1 mRNA expression following treatment with GCs, suggests the mode of GC activation to be mediated by a tethering mechanism involving the GR and the MKP-1 promoter-bound C/EBPβ.