TY - JOUR T1 - Reciprocal Regulation of β<sub>1</sub>-Adrenergic Receptor Gene Transcription by Sp1 and Early Growth Response Gene 1: Induction of EGR-1 Inhibits the Expression of the β<sub>1</sub>-Adrenergic Receptor Gene JF - Molecular Pharmacology JO - Mol Pharmacol SP - 379 LP - 390 DO - 10.1124/mol.61.2.379 VL - 61 IS - 2 AU - Suleiman W. Bahouth AU - Michael J. Beauchamp AU - Kim N. Vu Y1 - 2002/02/01 UR - http://molpharm.aspetjournals.org/content/61/2/379.abstract N2 - The β1-adrenergic receptor (β1-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 β1-AR gene. We determined that a 65-base-pair (bp) region in the β1-AR promoter between bp −394 and bp −330 directs basal transcription. An element located between −377 and −365 can bind Sp1 and Sp3. InDrosophila melanogaster SL2 cells, Sp1 stimulated the expression of the β1-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 β1-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 β1-AR promoter. Overexpression of Sp1 in SK-N-MC cells increased β1-AR mRNA by 2.4-fold, whereas overexpression of Egr-1 reduced β1-AR mRNA by 40%. Coexpression of Egr-1 with Sp1 reduced Sp1-mediated up-regulation of β1-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 β1-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 β1-AR gene expression. ER -