CHARACTERIZATION OF THE ALPHA(1B)-ADRENERGIC RECEPTOR GENE PROMOTER REGION AND HYPOXIA REGULATORY ELEMENTS IN VASCULAR SMOOTH-MUSCLE

We previously demonstrated that alpha(1B)-adrenergic receptor (AR) gen e transcription, mRNA, and functionally coupled receptors increase dur ing 3% O-2 exposure in aorta, but not in vena cava smooth muscle cells (SMC), We report here that alpha(1B)AR mRNA also increases during hyp oxia in liver and lung, but not heart and kidney, A single 2.7-kb alph a(1B)AR mRNA was detected in aorta and vena cava during normoxia and h ypoxia, The alpha(1B)AR 5' flanking region was sequenced to -2,460 (re lative to ATG + 1), Transient transfection experiments identify the mi nimal promoter region between -270 and -143 and sequence between -270 and -248 that are required for transcription of the alpha(1B)AR gene i n aorta and vena cava SMC during normoxia and hypoxia, An ATTAAA motif within this sequence specifically binds aorta, vena cava, and DDT1MF- 2 nuclear proteins, and transcription primarily initiates downstream o f this motif at approximately -160 in aorta SMC. Sequence between -837 and -273 conferred strong hypoxic induction of transcription in aorta , but not in vena cava SMC, whereas the cis-element for the transcript ion factor, hypoxia-inducible factor 1, conferred hypoxia-induced tran scription in both aorta and vena cava SMC, These data identify sequenc e required for transcription of the alpha(1B)AR gene in vascular SMC a nd suggest the atypical TATA-box, ATTAAA, may mediate this transcripti on, Hypoxia-sensitive regions of the alpha(1B)AR gene also were identi fied that may confer the differential hypoxic increase in alpha(1B)AR gene transcription in aorta, but not in vena cava SMC.