Open AccessFollitropin 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
Author(s) -
Suire Sabine,
Maurel MarieChristine,
Guillou Florian
Publication year - 1996
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1996.0052u.x
Subject(s) - creb , microbiology and biotechnology , binding site , enhancer , transcription factor , promoter , biology , response element , transcription (linguistics) , gene , gene expression , biochemistry , linguistics , philosophy
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 α and δ 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/EBPα allowed the cAMP‐inducible expression. The K a of CREB bZIP (254–327), a deleted form of CREB, for the CRE site (3.92 × 10 8 M −1 ) and for the PRII site (1.38 × 10 8 M −1 ) were determined using the surface plasmon resonance (SPR) method. The K a values were similar, although the derived kinetics were different: higher k a and k d 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 COUPTF and may explain the transcriptional regulation of Tf by follitropin, via cAMP.