Transcription of the rat β₁-adrenergic receptor gene: Characterization of the transcript and identification of important sequences

We have characterized the 5′ and 3′ ends of the rat β₁-adrenergic receptor transcript using RNase protection assays and have used transient transfection analysis to identify regions of the β₁-adrenergic gene 5′-flanking sequences which are important for expression. The transcript has multiple start sites, occurring primarily in two clusters at bases -250 and -280, relative to the first base of the initiation codon. Two potential polyadenylation signals at +2450 and +2732 are both functional, although the site at +2732 is preferred both in C6 glioma cells and in heart tissue. Characterization of the gene by transient transfection analysis has identified a region between bases -389 and -325 which is necessary for expression. The specific deletion of a potentially functional inverted CCAAT sequence within this region does not significantly alter activity. In addition to the region from -389 and -325, deletion of the bases between -1 and -159 and between -186 and -211 significantly alters expression. Both of these regions are downstream from the β₁-adrenergic receptor gene start sites and may function either through regulation of transcription or through alteration of the transcript structure.