9-cisretinoic acid accelerates calcitriol-induced osteocalcin production and promotes degradation of both vitamin D receptor and retinoid X receptor in human osteoblastic cells

2003 ◽  
Vol 89 (6) ◽  
pp. 1164-1176 ◽  
Author(s):  
Tiina Jääskeläinen ◽  
Sanna Ryhänen ◽  
Pekka H. Mäenpää
Keyword(s):  
Vitamin D ◽  
Vitamin D Receptor ◽  
Retinoid X Receptor ◽  
Osteoblastic Cells ◽  
Human Osteoblastic Cells ◽  
Osteocalcin Production

The Vitamin D Receptor Represses Transcription of the Pituitary Transcription Factor Pit-1 Gene without Involvement of the Retinoid X Receptor

2006 ◽  
Vol 20 (4) ◽  
pp. 735-748 ◽  
Author(s):  
Samuel Seoane ◽  
Roman Perez-Fernandez
Keyword(s):  
Vitamin D ◽  
Transcription Factor ◽  
Vitamin D Receptor ◽  
Retinoid X Receptor ◽  
Breast Adenocarcinoma ◽  
Mobility Shift ◽  
Histone Deacetylase 1 ◽  
Protein Levels ◽  
Repressive Effect ◽  
Mcf 7

Abstract Pituitary transcription factor-1 (Pit-1) plays a key role in cell differentiation during organogenesis of the anterior pituitary, and as a transcriptional activator for the pituitary GH and prolactin genes. However, Pit-1 is also expressed in nonpituitary cell types and tissues. In breast tumors, Pit-1 mRNA and protein levels are increased with respect to normal breast, and in MCF-7 human breast adenocarcinoma cells, Pit-1 increases GH secretion and cell proliferation. We report here that 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] administration to MCF-7 cells induces a significant decrease in Pit-1 mRNA and protein levels. By deletion analyses, we mapped a region (located between −147 and −171 bp from the transcription start site of the Pit-1 gene) that is sufficient for the repressive response to 1,25-(OH)2D3. Gel mobility shift and chromatin immunoprecipitation assays confirmed the direct interaction between the vitamin D receptor (VDR) as homodimer (without the retinoid X receptor), and the Pit-1 promoter, supporting the view that Pit-1 is a direct transcriptional target of VDR. Our data also indicate that recruitment of histone deacetylase 1 is involved in this repressive effect. This ligand-dependent Pit-1 gene inhibition by VDR in the absence of the retinoid X receptor seems to indicate a new mechanism of transcriptional repression by 1,25-(OH)2D3.

scholarly journals 1α,25(OH)2D3-Induced Transrepression by Vitamin D Receptor through E-Box-Type Elements in the Human Parathyroid Hormone Gene Promoter

2007 ◽  
Vol 21 (2) ◽  
pp. 334-342 ◽  
Author(s):  
Mi-sun Kim ◽  
Ryoji Fujiki ◽  
Akiko Murayama ◽  
Hirochika Kitagawa ◽  
Kazuyoshi Yamaoka ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Receptor ◽  
Gene Promoter ◽  
Negative Regulation ◽  
Retinoid X Receptor ◽  
Gene Promoters ◽  
Histone Deacetylase 2 ◽  
E Box ◽  
Renal Tubule Cell ◽  
Precise Molecular Mechanism

Abstract Although transactivation by the liganded vitamin D receptor (VDR) is well described at the molecular level, the precise molecular mechanism of negative regulation by the liganded VDR remains to be elucidated. We have previously reported a novel class of negative vitamin D response element (nVDRE) called 1αnVDRE in the human 25(OH)D31α-hydroxylase [1α(OH)ase] gene by 1α,25(OH)2D3-bound VDR. This element was composed of two E-box-type motifs that bound to VDIR for transactivation, which was attenuated by liganded VDR. Here, we explore the possible functions of VDIR and E-box motifs in the human (h) PTH and hPTHrP gene promoters. Functional mapping of the hPTH and hPTHrP promoters identified E-box-type elements acting as nVDREs in both the hPTH promoter (hPTHnVDRE; −87 to −60 bp) and in the hPTHrP promoter (hPTHrPnVDRE; −850 to −600 bp; −463 to −104 bp) in a mouse renal tubule cell line. The hPTHnVDRE alone was enough to direct ligand-induced transrepression mediated through VDR/retinoid X receptor and VDIR. Direct DNA binding of hPTHnVDRE to VDIR, but not VDR/retinoid X receptor, was observed and ligand-induced transrepression was coupled with recruitment of VDR and histone deacetylase 2 (HDAC2) to the hPTH promoter. These results suggest that negative regulation of the hPTH gene by liganded VDR is mediated by VDIR directly binding to the E-box-type nVDRE at the promoter, together with recruitment of an HDAC corepressor for ligand-induced transrepression.

scholarly journals YY1 regulates vitamin D receptor/retinoid X receptor mediated transactivation of the vitamin D responsive osteocalcin gene

1997 ◽  
Vol 94 (1) ◽  
pp. 121-126 ◽  
Author(s):  
B. Guo ◽  
F. Aslam ◽  
A. J. van Wijnen ◽  
S. G. E. Roberts ◽  
B. Frenkel ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Receptor ◽  
Retinoid X Receptor ◽  
Osteocalcin Gene

scholarly journals Hereditary 1,25-Dihydroxyvitamin D Resistant Rickets due to a Mutation Causing Multiple Defects in Vitamin D Receptor Function

Endocrinology ◽  
2004 ◽  
Vol 145 (11) ◽  
pp. 5106-5114 ◽  
Author(s):  
Peter J. Malloy ◽  
Rong Xu ◽  
Lihong Peng ◽  
Sara Peleg ◽  
Abdullah Al-Ashwal ◽  
...  
Keyword(s):  
Vitamin D ◽  
Ligand Binding ◽  
Vitamin D Receptor ◽  
Novel Mutation ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Retinoid X Receptor ◽  
Vdr Gene ◽  
Dihydroxyvitamin D3 ◽  
Resistant Rickets

Abstract Hereditary vitamin D-resistant rickets (HVDRR) is an autosomal recessive disease caused by mutations in the vitamin D receptor (VDR). We studied a young Saudi Arabian girl who exhibited the typical clinical features of HVDRR, but without alopecia. Analysis of her VDR gene revealed a homozygous T to C mutation in exon 7 that changed isoleucine to threonine at amino acid 268 (I268T). From crystallographic studies of the VDR ligand-binding domain, I268 directly interacts with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and is involved in the hydrophobic stabilization of helix H12. We recreated the I268T mutation and analyzed its effects on VDR function. In ligand binding assays, the I268T mutant VDR exhibited an approximately 5- to 10-fold lower affinity for [3H]1,25(OH)2D3 compared with the wild-type (WT) VDR. The I268T mutant required approximately a 65-fold higher concentration of 1,25(OH)2D3 to be equipotent in gene transactivation. Both retinoid X receptor heterodimerization and coactivator binding were reduced in the I268T mutant. Analogs of 1,25(OH)2D3 have been proposed as potential therapeutics for patients with HVDRR. Interestingly, in protease sensitivity assays, treatment with the potent vitamin D analog, 20-epi-1,25(OH)2D3, stabilized I268T mutant proteolytic fragments better than 1,25(OH)2D3. Moreover, 20-epi-1,25(OH)2D3 restored transactivation of the I268T mutant to levels exhibited by WT VDR treated with 1,25(OH)2D3. In conclusion, we describe a novel mutation, I268T, in the VDR ligand-binding domain that alters ligand binding, retinoid X receptor heterodimerization, and coactivator binding. These combined defects in VDR function cause resistance to 1,25(OH)2D3 action and result in the syndrome of HVDRR.

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