Delineation of the intronless nature of the genes for the human and hamster beta 2-adrenergic receptor and their putative promoter regions

Abstract

The beta 2-adrenergic receptor is the first adenylate cyclase-coupled receptor to be cloned. We provide here a detailed characterization of its complete gene in both the human and hamster which reveals several unusual and provocative features. The genes are present in a single copy, are intronless, and are bounded by homologous 18-bp (base pair) direct repeats. These findings suggest that the beta 2-adrenergic receptor may have arisen as a processed gene for another related gene. Genomic Southern blots done at reduced stringency in fact reveal additional weak signals. The human and hamster gene sequences 5' to the principal site of transcription initiation are highly homologous and share many characteristics of promoters for housekeeping genes. Moreover, there is present in the human genome a long (777 bp) open reading frame which is in frame with the beta-adrenergic receptor coding block and which ends only 234 bp 5' to the initiator methionine of the receptor. An unusual cDNA has been found, transcribed from a putative second more 5' promoter which contains the 5' half of the beta-adrenergic receptor as well as 1065-bp 5' to the receptor coding region, including the entire upstream long open reading frame (sufficient to encode a putative protein of Mr approximately 28,000).