MOLECULAR-STRUCTURE AND EXPRESSION OF RAT BRADYKININ B2 RECEPTOR GENE- EVIDENCE FOR ALTERNATIVE SPLICING

Bradykinin is a potent vasodilatory peptide hormone involved in a broa d range of physiological actions. While it acts through at least two t ypes of receptors which are named B1 and B2, most of its effects are m ediated via activation of the B2 receptor. The gene for this receptor was isolated hom a rat genomic library and shown to span more than 28 kilobases, including four introns. The relative positions of the exons were mapped and all exons, intron-exon boundaries, and 5'- and 3'-fla nking regions were sequenced. While the 5'-untranslated region of the mRNA is distributed on all four exons, the coding and the 3'-untransla ted region are located entirely on the fourth exon. Characterization o f the region upstream to the transcriptional start site detected by pr imer extension analysis shows that the bradykinin B2 receptor promoter contains no typical TATA or CCAAT boxes. Nevertheless, the promoter s equence was shown to be functional in NG108-15 cells transfected with a construct bearing 1.1 kilobases of 5'-flanking sequence fused to a l uciferase reporter gene. Reverse transcription-polymerase chain reacti on analysis detected two different bradykinin B2 receptor mRNAs contai ning or lacking exon 3 in all rat tissues tested, providing evidence f or alternative splicing of the 5'-untranslated sequence.