Spot35/calbindin-D28k is transcriptionally induced by 1,25-dihydroxyvitamin D3 in the intestine and kidney but not the brain. The structural organization of the mouse calbindin-D28k gene has now been determined and its transcriptional activation examined. Two direct repeat motifs homologous to other vitamin D-responsive elements were identified at positions -2295 to -2281 and -1160 to -1146. Undirectional deletion analyses of the 5' flanking region indicated that the sequence between -1339 and -1038 conferred vitamin D sensitivity on a reporter construct. Furthermore, the proximal (AGGTGAtgaAAGTCA), but not the distal (AGGTGAacaGGTTCA), direct repeat enhanced 1,25(OH)2D3-stimulated transcription in an orientation-dependent manner when placed upstream of the heterologous SV40 promoter. In conclusion, the proximal direct repeat plays a critical role in mediating the vitamin D-induced expression of calbindin-D28k in the kidney.