Characterization of the human beta(1)-adrenergic receptor gene and its transcriptional regulation
The beta$\sb1$-adrenergic receptor is a member of the superfamily of seven transmembrane receptors located in the plasma membrane of mammalian cells. It binds the catecholamines, epinephrine and norepinephrine, and transduces these signals to the interior of the cell. It is an integral part of the sympathetic nervous system. As such, the regulation of its expression is of great interest. The focus of this research was to characterize the gene of the human beta$\sb1$-adrenergic receptor and determine what may be important in the regulation of the gene. To do this a 13 kb genomic clone of the human beta$\sb1$-adrenergic receptor was isolated and its basal transcriptional regulation characterized. One open reading frame which lacks introns encodes the previously isolated human beta$\sb1$-adrenergic receptor cDNA. Several short open reading frames upstream of the receptor coding region may potentially regulate transcription of the gene. Despite significant sequence homology among species, the human transcript(s) are $\sim$4.9 kb compared to the rat, mouse and macaque transcripts which are all $\sim$2.6 kb. Northern blot analysis of human mRNA determined that the human transcript is most highly expressed in the pancreas, liver, heart, kidney, thalamus, adrenal and salivary glands and is subject to developmental regulation in kidney, heart, liver and brain. Primer extension and ribonuclease protection analyses suggest that a major transcriptional start site is located at $-$263 which is distinct from the transcriptional start sites found in other species. Transient expression of luciferase reporter gene constructs in human and rat cell lines indicates that the region from $-$444 to $-$106 possesses the primary promoter, consistent with the transcriptional start site at $-$263. There are two other putative promoters located in the regions $-$3118 to $-$1790 and $-$1112 to $-$964. The putative promoters upstream of $-$444 are responsible for half of the transcription in Hela cells, and may correspond to additional transcriptional start sites. The promoter between $-$1112 and $-$964 appears to be initiate beta$\sb1$-adrenergic receptor transcripts which are differentially expressed compared to the transcripts derived from the major promoter. Strong repressor elements are located in the regions $-$1112 to $-$964, $-$797 to $-$444 and $-$106 to $-$1. Both positive and negative regulatory elements are located in the region from $-$964 to $-$797 with the repressive activity apparently requiring the presence of sequence 5$\sp\prime$ to $-$964. The human beta-adrenergic receptor promoter is stimulated by glucocorticoids and the region responsible for stimulation in U-138MG cells is located between $-$964 and $-$797. The present study establishes that the expression and transcriptional regulation of the human beta$\sb1$-adrenergic receptor gene are distinct from those of the beta$\sb1$-adrenergic receptor genes of other species.
Evanko, Daniel Stephen, "Characterization of the human beta(1)-adrenergic receptor gene and its transcriptional regulation" (1997). ETD Collection for Thomas Jefferson University. AAI9730319.