Reciprocal Regulation of β1-Adrenergic Receptor Gene Transcription by Sp1 and Early Growth Response Gene 1: Induction of EGR-1 Inhibits the Expression of the β1-Adrenergic Receptor Gene
- 1 February 2002
- journal article
- Published by Elsevier in Molecular Pharmacology
- Vol. 61 (2) , 379-390
- https://doi.org/10.1124/mol.61.2.379
Abstract
The beta(1)-adrenergic receptor (beta(1)-AR) plays a key role in regulating heart rate and contractility in response to catecholamines. Our studies have focused on defining the factors that regulate the expression of the beta(1)-AR gene. We determined that a 65-base-pair (bp) region in the beta(1)-AR promoter between bp -394 and bp -330 directs basal transcription. An element located between -377 and -365 can bind Sp1 and Sp3. In Drosophila melanogaster SL2 cells, Sp1 stimulated the expression of the beta(1)-AR promoter, whereas Sp3 was unable to activate transcription. Site-directed mutagenesis indicated that an intact Sp1-binding site is essential for maintaining the activity of the basal promoter. In addition to binding Sp family members, the nucleotides between -381 and -367 can bind the zinc-finger transcription factor Egr-1. The Egr-1 and Sp1 binding sites are partially overlapping and their binding sequence is conserved among mammalian beta(1)-AR genes. The induction of Egr-1 in rat neonatal ventricular myocytes with phorbol-12-myristate-13-acetate or in HeLa S3 cells by regulated expression of Egr-1 in a tetracycline-responsive promoter, suppressed expression from the beta(1)-AR promoter. Overexpression of Sp1 in SK-N-MC cells increased beta(1)-AR mRNA by 2.4-fold, whereas overexpression of Egr-1 reduced beta(1)-AR mRNA by 40%. Coexpression of Egr-1 with Sp1 reduced Sp1-mediated up-regulation of beta(1)-AR mRNA by 60%. Mutagenesis revealed that an intact Sp1-binding site is essential for observing transcriptional repression by Egr-1 and that Egr-1 suppressed the transcription of the beta(1)-AR gene by competing with Sp1 for binding to their overlapping sites. These results reveal a novel physiologically relevant transcriptional mechanism for reciprocal regulation of beta(1)-AR gene expression.Keywords
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