| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1925533 | Archives of Biochemistry and Biophysics | 2012 | 7 Pages |
CYP24A1 functions in vitamin D target tissues to degrade 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Thus, the concentration of this enzyme and the regulation of its expression is a primary determinant of the overall biological activity of 1,25(OH)2D3 within cells. The principle regulator of CYP24A1 expression is 1,25(OH)2D3 itself, which functions through the vitamin D receptor to upregulate the transcriptional activity of the Cyp24a1 gene. In this report, we explore the mechanism of this regulation using recently developed ChIP-chip and ChIP-seq techniques that permit an unbiased search for enhancer elements that participate in this transcriptional control. Our studies both confirm a regulatory region defined earlier and located proximal to the transcriptional start site (TSS) of mouse Cyp24a1 (−160 and −265 nt) and identify a novel intergenic region located downstream of the transcription unit that contains two enhancers (+35 and +37 kb) that facilitate 1,25(OH)2D3-dependent upregulation of Cyp24a1 expression. Interestingly, while C/EBPβ also binds under basal conditions to a site located immediately upstream of the Cyp24a1 promoter (−345 nt), occupancy by this factor is strikingly increased following 1,25(OH)2D3 treatment. The locations and activities of these regulatory regions that mediate 1,25(OH)2D3 actions were confirmed in mice in vivo. We conclude that the mechanism through which 1,25(OH)2D3 induces the CYP24A1 enzyme, thereby autoregulating its own destruction, involves both promoter-proximal as well as downstream-distal enhancers. These findings highlight new concepts regarding the molecular mechanism of action of 1,25(OH)2D3 and other hormonal regulators.
► 1,25(OH)2D3 regulates the expression of Cyp24a1 through multiple proximal and distal enhancers. ► Activation induces VDR and RXR binding to VDREs located in each of the enhancers. ► 1,25(OH)2D3 co-induces binding of C/EBPβ to the enhancer located near the promoter. ► Similar vitamin D regulated enhancers are utilized in vivo in mouse intestine and kidney.
