DUAL PROMOTERS OF MOUSE MU-OPIOID RECEPTOR GENE

Two transcriptional initiation sites, distal and proximal, located at approximately 500 bp apart in mouse mu-opioid receptor gene were ident ified recently. Using deletional and transfection analyses, the distal or proximal promoter alone displayed similar activity in neuronal cel ls constitutively expressing mu-opioid receptors (SH-SY-5Y). The prese nce of both promoters did not result in an increase in activity. Howev er, when distal promoter linked with 3'-downstream sequences without t he proximal promoter region, the distal promoter activity was abolishe d. Transfection analysis using various cell lines further suggested th at only the proximal promoter preferentially directed the neuronal sub type expression. To verify the physiological importance of each promot er, the ratio of mu-receptor transcripts initiated by either promoter was examined by quantitative RT-PCR using mouse adult brain mRNA. We f ound that receptor mRNA was predominantly initiated by the proximal pr omoter. These studies suggested that the proximal promoter was the maj or functional promoter. (C) 1997 Academic Press.