Organization and Expression of the Mouse Spot35/Calbindin-D28k Gene: Identification of the Vitamin D-Responsive Promoter Region

Abstract

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. Unidirectional 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.