POU transcription factors Brn-3a and Brn-3b interact with the estrogen receptor and differentially regulate transcriptional activity via an estrogen response element.
The estrogen receptor (ER) modulates transcription by forming complexes with other proteins and then binding to the estrogen response element (ERE). We have identified a novel interaction of this receptor with the POU transcription factors Brn-3a and Brn-3b which was independent of ligand binding. By pull-down assays and the yeast two-hybrid system, the POU domain of Brn-3a and Brn-3b was shown to interact with the DNA-binding domain of the ER. Brn-3-ER interactions also affect transcriptional activity of an ERE-containing promoter, such that in estradiol-stimulated cells, Brn-3b strongly activated the promoter via the ERE, while Brn-3a had a mild inhibitory effect. The POU domain of Brn-3b which interacts with the ER was sufficient to confer this activation potential, and the change of a single amino acid in the first helix of the POU homeodomain of Brn-3a to its equivalent in Brn-3b can change the mild repressive effect of Brn-3a to a stimulatory Brn-3b-like effect. These observations and their implications for transcriptional regulation by the ER are discussed.
Budhram-Mahadeo
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Department of Molecular Pathology, The Windeyer Institute of Medical Sciences, University College Medical School, London, United Kingdom.
Parker
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Latchman
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DS
D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D007532:Isoleucine / Q000378:metabolism; D008970:Molecular Weight; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011960:Receptors, Estrogen / Q000378:metabolism*; D050818:Transcription Factor Brn-3; D050819:Transcription Factor Brn-3A; D050820:Transcription Factor Brn-3B; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D014633:Valine / Q000378:metabolism
D004268:DNA-Binding Proteins; C494188:POU4F1 protein, human; C494190:POU4F2 protein, human; D011960:Receptors, Estrogen; D050818:Transcription Factor Brn-3; D050819:Transcription Factor Brn-3A; D050820:Transcription Factor Brn-3B; D014157:Transcription Factors; D007532:Isoleucine; D004247:DNA; D014633:Valine