Follitropin action on the transferrin gene in Sertoli cells is mediated by cAMP-responsive-element-binding-protein and antagonized by chicken ovalbumin-upstream-promoter-transcription factor.
The transcription of the transferrin (Tf) gene is induced by follitropin via cAMP in rat Sertoli cells. We previously demonstrated that the cAMP-responsive-element-binding protein (CREB) interacts on the proximal region II (PRII) of the human Tf promoter (Suire et al., 1995). The PRII region is identified as essential for cAMP inducibility of the Tf promoter and contains a CCAAT box. This unexpected result led us to study the relation that exists between CREB and the PRII site. In the liver, CCAAT/enhancer-binding (C/EBP) proteins act at the PRII site. Although these factors are absent in Sertoli cells, their overexpression in Sertoli cells disturbs basal and induced transcription. C/EBP alpha and delta were able to stimulate the basal transcription driven by the -100 to +39 region, placed upstream of the chloramphenicol acetyltransferase (CAT) gene. However, only C/EBP alpha allowed the cAMP-inducible expression. The Ka of CREB bZIP (254-327), a deleted form of CREB, for the CRE site (3.92 x 10(8)M-1) and for the PRII site (1.38 x 10(8)M-1) were determined using the surface plasmon resonance (SPR) method. The Ka values were similar, although the derived kinetics were different: higher ka and kd of CREB for the PRII site were found compared with the CRE site. Since we observed important dissociation kinetics, we hypothesized that the binding of CREB to the PRII site is stabilized by CREB-binding protein (CBP) or by chicken-ovalbumin-upstream-promoter transcription factor (COUP-TF) binding to PRI site near to PRII. However, we observed that the overexpression of CBP in Sertoli cells did not potentiate the basal and cAMP-stimulated activity of CREB of the -100 to +39Tf-CAT construct. In basal and cAMP-stimulated conditions, COUP-TF appeared to repress the transcription driven by the -100 to +39 region in a specific manner. These results demonstrate a direct action of CREB on hTf promoter, which is antagonized by COUP-TF and may explain the transcriptional regulation of Tf by follitropin, via cAMP.
Suire
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Institut National de la Recherche Agronomique Station de Physiologie de la Reproduction des Mammiferes Domestiques, INRA/CNRS URA 1291, Nouzilly, France.
Maurel
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MC
Guillou
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D000818:Animals; D003994:Bucladesine / Q000037:antagonists & inhibitors; D051838:COUP Transcription Factor I; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005640:Follicle Stimulating Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008297:Male; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D012708:Sertoli Cells / Q000187:drug effects* / Q000378:metabolism; D013057:Spectrum Analysis; D014157:Transcription Factors / Q000378:metabolism*; D014168:Transferrin / Q000235:genetics*
D051838:COUP Transcription Factor I; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C497589:NR2F1 protein, human; C497591:Nr2f1 protein, rat; D009838:Oligodeoxyribonucleotides; D014157:Transcription Factors; D014168:Transferrin; D003994:Bucladesine; D005640:Follicle Stimulating Hormone