Characterization of Gene Organization and Promoter Region of the Rat Dopamine D1 Receptor Gene

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Abstract
Genomic and cDNA clones encoding the rat Dl receptor were isolated and sequenced. Comparison of the Dl receptor cDNA and genomic sequences revealed that the rat Dl receptor gene is organized into two exons separated by a small intron in the 5’untranslated region of its mRNA. The transcription start site is located 864 bp upstream from the translational initiation site. The 5′-flanking sequences of the Dl receptor gene do not contain TATA and CAAT canonical sequences, but have a high G + C content, potential cyclic AMP and glucocorticoid response element sequences, and binding sites for transcription factors such as Sp1, Ap1, and Ap2. Transfection studies using the Dl 5′-flanking sequence and CAT gene fusion constructs have demonstrated that (1) the D1 promoter is active in Dl-expressing neuroblastoma NS20Y cells, but inactive in D1-deficient glioma C6 and kidney 293 cells, (2) the information contained within 735 bp of 5′-flanking sequence of the Dl gene appears to be sufficient to confer its cell-specific expression, and (3) the Dl gene promoter responds to cyclic AMP induction, suggesting the existence of an autoregulation mechanism by which the stimulation of Dl receptor exerts a positive feedback on its own gene expression.