Identification of a vitamin D responsive element in the promoter of the rat cytochrome P450(24) gene.
AUTOR(ES)
Hahn, C N
RESUMO
Mitochondrial cytochrome P450(24) expression in the vitamin D-degradation pathway is induced by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. The molecular basis of this enzyme regulation was investigated by isolating the rat P450(24) gene and examining the 5'-flanking region for possible cis-acting regulatory elements involved in the induction process. Constructs containing different lengths of 5'-flanking region of the gene were linked to a luciferase reporter gene and transiently co-transfected with a human vitamin D receptor (hVDR) expression vector (pRSV-hVDR) into COS-1 cells. These experiments showed that the flanking region from -298 to -122 directed a 24-fold increase in luciferase activity in response to 1,25-(OH)2D3 provided that the cells were co-transfected with pRSV-hVDR. Within this region, the sequence from position -171 to -123 conferred 1,25-(OH)2D3 responsiveness to both the native P450(24) promoter and the heterologous thymidine kinase promoter. Mutagenesis revealed that the sequence from position -150 to -136 is required for induction by 1,25-(OH)2D3 and that this sequence shares similarity to other vitamin D responsive elements (VDREs) reported for other genes. Gel shift mobility assays showed this region specifically bound a nuclear protein complex from 1,25-(OH)2D3 treated COS-1 cells that had been co-transfected with pRSV-hVDR. The retarded band was specifically competed with the well characterized VDRE from the mouse osteopontin gene. A VDRE at position -150 to -136 in the promoter of the rat P450(24) gene is identified in this study and found to be important in mediating the enhanced expression of the gene by 1,25-(OH)2D3.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=523703Documentos Relacionados
- Identification of a vitamin D-response element in the rat calcidiol (25-hydroxyvitamin D3) 24-hydroxylase gene.
- Identification of a cyclic-AMP-responsive element within the rat somatostatin gene.
- In situ protein-DNA interactions at a dioxin-responsive enhancer associated with the cytochrome P1-450 gene.
- Location of regulatory elements responsible for drug induction in the rat cytochrome P-450c gene.
- Identification of an estrogen-responsive element from the 5'-flanking region of the rat prolactin gene.