Regulation of the intronic promoter of rat estrogen receptor alpha gene, responsible for truncated estrogen receptor product-1 expression.
We have characterized the intronic promoter of the rat estrogen receptor (ER) alpha gene, responsible for the lactotrope-specific truncated ER product (TERP)-1 isoform expression. Transcriptional regulation was investigated by transient transfections using 5'-deletion constructs. TERP promoter constructs were highly active in MMQ cells, a pure lactotrope cell line, whereas a low basal activity was detected in alphaT3-1 gonadotrope cells or in COS-7 monkey kidney cells. Serial deletion analysis revealed that 1) a minimal -693-bp region encompassing the TATA box is sufficient to allow lactotrope-specific expression; 2) the promoter contains strong positive cis-acting elements both in the distal and proximal regions, and 3) the region spanning the -1698/-1194 region includes repressor elements. Transient transfection studies, EMSAs, and gel shifts demonstrated that estrogen activates the TERP promoter via an estrogen-responsive element (ERE1) located within the proximal region. Mutation of ERE1 site completely abolishes the estradiol-dependent transcription, indicating that ERE1 site is sufficient to confer estrogen responsiveness to TERP promoter. In addition, ERalpha action was synergized by transfection of the pituitary-specific factor Pit-1. EMSAs showed that a single Pit-1 DNA binding element in the vicinity of the TATA box is sufficient to confer response by the TERP promoter. In conclusion, we demonstrated, for the first time, that TERP promoter regulation involves ERE and Pit-1 cis-elements and corresponding trans-acting factors, which could play a role in the physiological changes that occur in TERP-1 transcription in lactotrope cells.
Schausi
Diane
D
Université de Rennes I, Interactions Cellulaires et Moléculaires, Equipe Information et Programmation Cellulaires, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6026, Campus de Beaulieu, 35042 Rennes Cedex, France.
Tiffoche
Christophe
C
Thieulant
Marie-Lise
ML
D024506:5' Flanking Region / Q000235:genetics; D000818:Animals; D001943:Breast Neoplasms; D016466:CHO Cells; D019556:COS Cells; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism*; D047628:Estrogen Receptor alpha; D005786:Gene Expression Regulation / Q000502:physiology; D005816:Genetic Complementation Test; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D011960:Receptors, Estrogen / Q000235:genetics*; D020218:Response Elements / Q000235:genetics; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology; D014407:Tumor Cells, Cultured; D000097577:Homeobox Protein PITX2
D004268:DNA-Binding Proteins; D047628:Estrogen Receptor alpha; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D051761:Paired Box Transcription Factors; D011960:Receptors, Estrogen; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C494187:POU1F1 protein, human; C494186:Pou1f1 protein, rat; C118565:TERP-1; C101485:homeobox protein PITX1