ORGANIZATION AND EXPRESSION OF THE MOUSE SPOT35 CALBINDIN-D28K GENE -IDENTIFICATION OF THE VITAMIN-D-RESPONSIVE PROMOTER REGION

Spot35/calbindin-D28k is transcriptionally induced by 1,25-dihydroxyvi tamin D-3 in the intestine and kidney but not the brain. The structura l organization of the mouse calbindin-D28k gene has now been determine d and its transcriptional activation examined. Two direct repeat motif s homologous to other vitamin D-responsive elements were identified at positions -2295 to 2281 and -1160 to -1146. Unidirectional deletion a nalyses of the 5' flanking region indicated that the sequence between -1339 and -1038 conferred vitamin D sensitivity on a reporter construc t. Furthermore, the proximal (AGGTGAtgaAAGTCA), but not the distal (AG GTGAacaGGTTCA), direct repeat enhanced 1,25(OH)(2)D-3-stimulated trans cription in an orientation-dependent manner when placed upstream of th e heterologous SV40 promoter, in conclusion, the proximal direct repea t plays a critical role in mediating the vitamin D-induced expression of calbindin-D28k in the kidney. (C) 1994 Academic Press, Inc.