Activation of the mouse oxytocin promoter by the orphan receptor ROR alpha

Although an increasing number of nuclear orphan receptors have recently bee n identified, the number of known naturally occurring genes that are direct ly regulated by orphan receptors is still small. We have shown previously t hat the gene encoding the neuropeptide oxytocin (OT) is negatively regulate d by the orphan receptors chicken ovalbumin upstream transcription factor I (COUP-TFI) and II. Here we show that the mouse OT gene promoter is activat ed by ROR alpha, a representative of the ROR/RZR orphan receptor subfamily. Using promoter/chloramphenicol acetyltransferase reporter constructs in he terologous transfection assays, we determined that ROR alpha action induces a <6-fold increase in promoter activity. By 5' and 3' deletion analysis, D Nase footprint analysis and electrophoretic mobility shift assays, we found that ROR alpha action is mediated by two 14bp regions centered at 160 and 180 nucleotides upstream of the transcriptional initiation site. Both sites contain significant sequence identities with an established ROR recognitio n sequence, Mutations in either or both of these sites reduce significantly ROR alpha-induced activation of the OT promoter. In view of the strong tra nscriptional activation exerted by ROR alpha on the OT gene promoter and th e widespread distribution of different members of the ROR/RZR family, inter actions between ROR/RZR isoforms and the OT gene may form part of the multi factorial regulatory mechanisms that control OT gene expression in differen t tissues.