Promoter Analysis of the Rat β₁-Adrenergic Receptor Gene Identifies Sequences Involved in Basal Expression

Abstract

The beta1-adrenergic receptor (beta1-AR) mediates several functions of catecholamines in the heart, including the stimulation of heart rate and contractility. The expression of the rat beta1-AR gene was assessed by transiently transfecting chimeric genes containing the beta1-AR promoter, driving the luciferase reporter gene into various cell lines. beta1-AR/luciferase vectors containing 3 kb of the 5'-flanking region and extending to -126 relative to the start site of translation were expressed at high levels in ventricular myocytes, SK-N-MC cells, and HepG2 cells. The addition of 26 nucleotides from -125 to -100 to the -3311 beta1-AR/luciferase chimeric gene reduced expression in myocytes and SK-N-MC cells while eliminating expression in HepG2 cells. This element is located 125 base-pairs 3' to the transcriptional start site. The mutation of four nucleotides between -121 and -118 diminished the inhibitory effect of this element. The inhibitory activity of the -125 to -100 sequence was completely dependent on promoter context and positioning. In addition to this 3' element, sequences between -3311 and -2740 in the 5'-flanking region of the beta1-AR gene were required for the full transcriptional suppression. Using DNase I footprinting and gel mobility assays, it was determined that within the 26-bp region, rat heart nuclear proteins bound to two sites between nucleotides -123 and -112 and -106 and -100. Therefore, appropriate basal expression of the beta1-AR gene involves widely separated sequences 3' and 5' to the transcriptional start site.

Thyroid Hormone Regulates Carnitine Palmitoyltransferase Iα Gene Expression through Elements in the Promoter and First Intron

“…T3-responsive elements have been described that are 3Ј to the transcriptional start site in several genes. Transcription of the ␤ 1 -adrenergic receptor gene is stimulated by T3 in cardiac ventricular myocytes (41). We have demonstrated that although the TRE of the ␤ 1 -adrenergic receptor gene is located 3Ј to the transcriptional start site, the induction by T3 is dependent on promoter elements located more that 2,000 base pairs upstream (41).…”

“…Transcription of the ␤ 1 -adrenergic receptor gene is stimulated by T3 in cardiac ventricular myocytes (41). We have demonstrated that although the TRE of the ␤ 1 -adrenergic receptor gene is located 3Ј to the transcriptional start site, the induction by T3 is dependent on promoter elements located more that 2,000 base pairs upstream (41). The NRGN gene in the human brain is regulated by T3 through a TRE located in the first intron of the gene (42).…”

Zinc Protoporphyrin Regulates Cyclin D1 Expression Independent of Heme Oxygenase Inhibition

“…Decreased Sp1 or enhanced Egr1 binding could lead to either transcriptional activation or repression, respectively. For example, Egr1 acts as a negative regulator and represses Sp1-mediated activation of some genes including protein-tyrosine phosphatase 1B, Met, Epstein-Barr virus C, and ␤ 1 -adrenergic receptor (40,42,44,45). In another circumstance, Egr1 competes with Sp1 protein for an overlapping region in the promoter of platelet-derived growth factor A and functions as a positive activator (46).…”

Role of Early Growth Response-1 (Egr-1) in Interleukin-13-induced Inflammation and Remodeling

“…The present studies suggest that the effects of IL-13 in these disorders can be beneficially controlled with interventions that control Egr-1. This can be accomplished a numbers of ways because Egr-1 is activated via a complex process that involves Egr-1 phosphorylation, Egr-1-SP-1 binding, and competition between Egr-1 and SP-1 for GC-rich cis-elements in the promoters of target genes (29). Additional investigations of the biology of and therapeutic utility of Egr-1 interventions in IL-13-and Th-2-mediated disorders is warranted.…”