cAMP activates transcription of the human glucocorticoid receptor gene promoter.
Glucocorticoids and cAMP regulate, either in a synergistic or additive fashion, the transcription of multiple genes, although some antagonistic effects of dexamethasone on cAMP-activated transcription have been described. The increased glucocorticoid receptor (GR) mediated response of some cell types, as a result of augmented cAMP, has been considered to be mainly due to an increased stability of GR mRNA, although other plausible explanations should not be ruled out. We studied the possibility that GR transcription itself could be affected by cAMP levels. HeLa cells were transfected with human GR (hGR) promoter constructs and their transcriptional activity determined after inducing a cAMP increase with forskolin. We found that forskolin almost doubled the transcriptional activity of the promoter construct spanning -2995 to +38 of the hGR, whereas no significant variations were observed with shorter chimeras containing sequences downstream -979. Shift mobility showed binding of CREB in vitro to a putative cAMP responsive element located at -1000, suggesting that hGR may be upregulated by cAMP at the transcriptional level, thus adding a new mechanism ascribable to this second messenger, which in conjunction with the cAMP-induced GR mRNA increased stability, would lead to a more precise control of the amount of GR protein within the cell.
Peñuelas
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I
Department of Biochemistry and Molecular Biology, University of Navarra School of Medicine, Pamplona, Spain. ipenuelas@unav.es
Encío
I J
IJ
López-Moratalla
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N
Santiago
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E
D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000235:genetics*; D005938:Glucocorticoids / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000235:genetics; D011965:Receptors, Glucocorticoid / Q000819:agonists / Q000235:genetics*; D015533:Transcriptional Activation; D014162:Transfection
D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D005576:Colforsin; D000242:Cyclic AMP