Vitamin-D-dependent transcriptional regulation of the intestinal plasma membrane calcium pump

The vitamin D hormone, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], was shown to increase intestinal plasma membrane calcium pump (PMCA) gene expression. The present study was done to determine whether gene transcription is involved in this process. Nuclei were isolated from duodena of vitamin-D-deficient chicks given 1,25(OH)2D3 intracardially at various times before experiment. The abundance of PMCA RNA in the nuclear and total cellular fractions, measured by a ribonuclease protection assay, was significantly increased above control values at 1.5 hr. and maximized at 3 hr. post-dose. As shown, cross-contamination of nuclear PMCA RNA by cytosolic RNA cannot account for these results. These studies are the first to show that 1,25(OH)2D3 regulates expression of a plasma membrane calcium pump gene by increasing the rate of transcription.