Synergistic activation of the prolactin promoter by vitamin D receptor and GHF-1: role of the coactivators, CREB-binding protein and steroid hormone receptor coactivator-1 (SRC-1).
PRL gene expression is dependent on the presence of the pituitary-specific transcription factor GHF-1/Pit-1, which is transcribed in a highly restricted manner in cells of the anterior pituitary. In pituitary GH3 cells, vitamin D increases the levels of PRL transcripts and stimulates the PRL promoter. We have analyzed the role of GHF-1 and of the vitamin D receptor (VDR) to confer vitamin D responsiveness to the PRL promoter. For this purpose we have used nonpituitary HeLa cells, which do not express GHF-1. We found that VDR activates the PRL promoter both in a ligand-dependent and -independent manner through a sequence located between positions -45/-27 in the proximal 5'-flanking region. This sequence also confers VDR and vitamin D responsiveness to a heterologous promoter. In the context of the PRL gene, VDR requires the presence of GHF-1 to activate the promoter. Truncation of the last 12 C-terminal amino acids of VDR, which contain the ligand-dependent activation function (AF2), abolishes regulation by vitamin D, suggesting that binding of coactivators to this region mediates ligand-dependent stimulation of the PRL promoter by the receptor. Indeed, expression of the coactivators, steroid hormone receptor coactivator-1 (SRC-1) and CREB-binding protein (CBP), significantly enhances the stimulatory effect of vitamin D mediated by the wild-type VDR but not by the AF2 mutant receptor. Furthermore, CBP also increases the activation of the PRL promoter by GHF-1 and the ligand-independent activation by both wild-type and mutant VDR.
Castillo
A I
AI
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Jimenez-Lara
A M
AM
Tolon
R M
RM
Aranda
A
A
D000818:Animals; D001483:Base Sequence; D050882:CREB-Binding Protein; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D005668:Furylfuramide / Q000378:metabolism; D006367:HeLa Cells / Q000378:metabolism; D051548:Histone Acetyltransferases; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D056920:Nuclear Receptor Coactivator 1; D010911:Pituitary Neoplasms / Q000235:genetics / Q000378:metabolism; D011388:Prolactin / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051381:Rats; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D047488:Retinoid X Receptors; D015534:Trans-Activators / Q000378:metabolism*; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014807:Vitamin D / Q000378:metabolism
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C494187:POU1F1 protein, human; C494186:Pou1f1 protein, rat; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D015534:Trans-Activators; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D005668:Furylfuramide; D014807:Vitamin D; D011388:Prolactin; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494365:Crebbp protein, rat; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1