THE GENOMIC ORGANIZATION OF THE RAT ANGIOTENSIN-II RECEPTOR AT(1B)

Expression of two subtypes of angiotensin type 1 receptor (AT(1A) and AT(1B)) seems to be controlled by different mechanisms. As a step toward the elucidation of difference in the mechanism in their gene expression, the genomic organization of rat angiotensin II type 1B receptor was investigated. Rat genomic DNA fragments were cloned by screening a genomic library with fragments from two cDNA clones (2.3 and 2.2 kb) encoding the rat AT(1B) receptor. Three lambda clones were isolated, and the hybridizing restriction fragments were sequenced. Comparison of the genomic clone DNA and cDNA sequences revealed that the rat AT(1B) receptor gene contains three exons and two introns. Two of the exons encoded 5' untranslated sequences while the third exon contained the entire coding region. The 5'-flanking region contained the typical sequence motifs found in many eukaryotic promoters including a TATA box and a potential SP1 binding site. The transcription initiation site was located at -8 bp upstream the 5' end of the cDNA in the 5'-flanking region.