1,25-dihydroxyvitamin D-3 induction of the tissue-type plasminogen activator gene is mediated through its multihormone-responsive enhancer

Tissue-type plasminogen activator (t-PA) is a positive modulator of the pla sminogen-plasmin system, which is involved in bone remodeling, In the prese nt study, 1,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3] was found to stimulate t-PA gene expression in ROS17/2.8 osteosarcoma cells, Transient transfecti on analysis and in vitro DNA binding studies identified two vitamin D-respo nsive elements (VDRE) in the human t-PA enhancer, The first VDRE (bp -7175 to -7146) comprised an inverted palindrome separated by 9 bp (IP9) overlapp ing a palindrome separated by 3 bp. The second VDRE (bp -7315 to -7302) is an IP2 element overlapping the previously identified retinoic acid-responsi ve element. 1,25(OH)(2)D-3 treatment of primary osteoblasts derived from t- PAlacZ transgenic mice containing 9 kb of 5' sequence of the human t-PA gen e increased the number of lacZ-positive cells, fitting with the probability model of enhancer function. (C) 1999 Federation of European Biochemical So cieties.