The transcription factors SP1 and MAZ regulate expression of the parathyroid hormone/parathyroid hormone-related peptide receptor gene

The parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor regulate s extracellular calcium concentrations and is therefore important for miner al homeostasis. ROS 17/2.8 cells, a rat osteoblast-like osteosarcoma cell l ine, express the PTH/PTHrP receptor and provide a good model for examining the transcriptional regulation of its gene. The rat PTH/PTHrP receptor gene has two promoters, U1 and U3, which were shown to be important for its exp ression. Using extracts from ROS 17/2.8 cells, we have demonstrated two reg ions (termed FP1 and FP2) of nuclear protein/DNA interaction within promote r sequences previously shown to be important for the activity of the U3 pro moter. Nuclear extracts from rat 2 fibroblasts, which do not express the PT H/PTHrP receptor, produced one site of protein/DNA interaction which was fo und at a position on the promoter identical to the position of FP1 produced by a ROS 17/2.8 nuclear extract. Mutation of these two sites of protein/DN A interaction resulted in reduced U3 promoter activity. Furthermore, we hav e demonstrated that the transcription factors SP1 and MAZ regulate U3 promo ter expression and have shown their functional significance using mutationa l analysis. These data demonstrate that SP1 and MAZ bind to the PTH/PTHrP r eceptor promoter and that they are involved in cell-specific expression of its gene product.