Identification and characterization of a novel promoter of the mouse mu opioid receptor gene (Oprm) that generates eight splice variants.

Our previous studies isolated and characterized eight splicing variants containing exon 11 as the first coding exon. The location of exon 11 about 10 kb upstream from exon 1 dual promoters implied another promoter to drive expression of the exon 11 variants. I now identify the second promoter in the 5'-flanking region of exon 11. One major transcriptional start point was determined. Sequence analysis indicated that the 5'-flanking region of the exon 11 contained a putative TATA box, several CAAT boxes and a number of cis-acting elements. Functional analysis suggested that exon 11 promoter activity was most evident in neuronal-like cells. A basal core region containing the TATA box, a negative region and a positive region were identified. Electrophoretic mobility shift assays with the nuclear extracts from NIE-115 cells revealed several protein complexes that likely contained TATA box-associated factors, NF-1-like and cMyc-Max-like proteins, respectively. It also showed that a TATA-binding protein specifically bound to the TATA box fragment. Mutation analysis suggested that the TATA box in the basal core region played a fundamental role in the exon 11 promoter, whereas the NF-1 site acted as a positive element.