Functional role of VDR in the activation of p27^Kip1 by the VDR/Sp1 complex

Abstract

Our previous study demonstrate that vitamin D3 induces the binding of vitamin D3 receptor (VDR) to Sp1 transcription factor and stimulates p27Kip1 expression via the Sp1 consensus sequences in the promoter. Both VDR and Sp1 are transcriptional activators, it is unclear which protein functions as the transcription component of the VDR/Sp1 complex. To address this issue, we constructed the AF-2 deletion mutant of VDR and tested the effect of vitamin D3 on p27Kip1 expression. In consistent with our previous results, we found that expression of wild-type VDR in SW620 colon cancer cells, which expressed very low level of endogenous VDR, increased vitamin D3-stimulated p27Kip1 promoter activity and protein expression. On the contrary, expression of AF-2 deletion mutant had little effect. DNA affinity precipitation assay (DAPA) showed that both wild-type and deletion mutant of VDR bound to the DNA probe corresponding to the Sp1 binding site in the p27Kip1 promoter in a vitamin D3-dependent manner indicating deletion of AF-2 domain does not affect the interaction between VDR and Sp1. Chromatin immunoprecipitation (CHIP) assay also confirmed that VDR and its AF-2 deletion mutant bound to p27Kip1 promoter in vivo. We found that deletion of AF-2 domain abolished the interaction of coactivators SRC-1 and DRIP205 with VDR. Taken together, our results suggest that VDR functions as the transactivation component of the VDR/Sp1 complex to trigger gene expression.

Myeloid cell differentiation in response to calcitriol for expressionCD11bandCD14is regulated by myeloid zinc finger-1 protein downstream of phosphatidylinositol 3-kinase

“…After silencing of MZF-1, as described in the legend to tion factors. Moreover, just as it has become clear that multiple transcription factors may interact with each other to modulate the expression of a wide variety of genes [52,53], this is also likely to be the case for CD11b and CD14 [54,55].…”

Actions of 1,25(OH)2-vitamin D3 on the cellular cycle depend on VDR and p38 MAPK in skeletal muscle cells

“…With respect to p27 Kip1 , the VDR functions as the transactivation component of the VDR-Sp1 complex to trigger the expression of its gene (Cheng et al 2006). Also, 1,25D-upregulation of CKI p27 Kip1 is blocked by a p38 inhibitor (Miura et al 2005).…”

Interplay of Posttranslational Modifications in Sp1 Mediates Sp1 Stability during Cell Cycle Progression

“…[11][12][13] In addition to several oncogenes such as vascular endothelial growth factor, urokinase plasminogen activator, urokinase plasminogen activator receptor, and epithelial growth factor receptor, many tumor suppressor genes, such as p27 kip1 , p21 WAF1/CIP1 , p16 INK4 , and pp2a-c, are also induced by Sp1. [14][15][16][17][18][19][20] Further, many pro-apoptotic gene promoters, including fas, fas ligand, fax, and caspase 3, have been found to contain Sp1-binding elements. [21][22][23] Previous studies have revealed that upregulation of Sp1 transcriptional activity leads to Sp1 accumulation during tumorigenesis.…”