Interaction of the 1α,25-dihydroxyvitamin D3 receptor at the distal promoter region of the bone-specific osteocalcin gene requires nucleosomal remodelling (original) (raw)
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Steroids, 2001
The vitamin D response element in the bone tissue-specific osteocalcin gene has served as a prototype for understanding molecular mechanisms regulating physiologic responsiveness of vitamin D-dependent genes in bone cells. We briefly review factors which contribute to vitamin D transcriptional control. The organization of the vitamin D response element (VDRE), the multiple activities of the vitamin D receptor transactivation complex, and the necessity for protein-protein interactions between the VDR-RXR heterodimer activation complex and DNA binding proteins at other regulatory elements, including AP-1 sites and TATA boxes, provide for precise regulation of gene activity in concert with basal levels of transcription. We present evidence for molecular mechanisms regulating vitamin D-dependent mediated transcription of the osteocalcin gene that involve chromatin structure of the gene and nuclear architecture. Modifications in nucleosomal organization, DNase I hypersensitivity and localization of vitamin D receptor interacting proteins in subnuclear domains are regulatory components of vitamin D-dependent gene transcription. A model is proposed to account for the inability of vitamin D induction of the osteocalcin gene in the absence of ongoing basal transcription by competition of the YY1 nuclear matrix-associated transcription factor for TFIIB-VDR interactions. Activation of the VDR-RXR complex at the OC VDRE occurs through modifications in chromatin mediated in part by interaction of OC gene regulatory sequences with the nuclear matrix-associated Cbfa1 (Runx2) transcription factor which is required for osteogenesis.
Journal of Cellular Physiology, 2010
1α,25-dihydroxy vitamin D 3 (Vitamin D 3 ) has an important role during osteoblast differentiation as it directly modulates the expression of key bone-related genes. Vitamin D 3 binds to the Vitamin D 3 receptor (VDR), a member of the superfamily of nuclear receptors, which in turn interacts with transcriptional activators to target this regulatory complex to specific sequence elements within gene promoters. Increasing evidence demonstrates that the architectural organization of the genome and regulatory proteins within the eukaryotic nucleus support gene expression in a physiological manner. Previous reports indicated that the VDR exhibits a punctate nuclear distribution that is significantly enhanced in cells grown in the presence of Vitamin D 3 . Here, we demonstrate that in osteoblastic cells, the VDR binds to the nuclear matrix in a vitamin D 3dependent manner. This interaction of VDR with the nuclear matrix occurs rapidly after vitamin D 3 addition and does not require a functional VDR DNA binding domain. Importantly, nuclear matrix-bound VDR colocalizes with its transcriptional coactivator DRIP205/TRAP220/MED1 which is also matrix-bound. Together these results indicate that after ligand stimulation the VDR rapidly enters the nucleus and associates with the nuclear matrix preceding vitamin D 3transcriptional upregulation.
The Journal of Steroid Biochemistry and Molecular Biology, 2010
The architectural organization of the genome and regulatory proteins within the nucleus supports gene expression in a physiologically regulated manner. In osteoblastic cells ligand activation induces a nuclear punctate distribution of the 1␣,25-dihydroxy vitamin D3 (1␣,25(OH) 2 D 3 ) receptor (VDR) and promotes its interaction with transcriptional coactivators such as SRC-1, NCoA-62/Skip, and DRIP205. Here, we discuss evidence demonstrating that in osteoblastic cells VDR binds to the nuclear matrix fraction in a 1␣,25(OH) 2 D 3 -dependent manner. This interaction occurs rapidly after exposure to 1␣,25(OH) 2 D 3 and does not require a functional VDR DNA binding domain. The nuclear matrix-bound VDR molecules colocalize with the also nuclear matrix-associated coactivator DRIP205. We propose a model where the rapid association of VDR with the nuclear matrix fraction represents an event that follows 1␣,25(OH) 2 D 3dependent nuclear localization of VDR, but that precedes 1␣,25(OH) 2 D 3 -dependent transcriptional upregulation at target genes.
Proceedings of the National Academy of Sciences, 1992
The observation that vitamin D-mediated enhancement of osteocalcin (OC) gene expression is dependent on and reciprocally related to the level of basal gene expression suggests that an interaction of the vitamin D responsive element (VDRE) with basal regulatory elements of the OC gene promoter contributes to both basal and vitamin D-enhanced transcription. Protein-DNA interactions at the VDRE of the rat OC gene (nudeotides -466 to -437) are reflected by direct sequence-specific and antibody-sensitive binding of the endogenous vitamin D receptor present in ROS 17/2.8 osteosarcoma nuclear protein extracts. In addition, a vitamin D-responsive increase in OC gene transcription is accompanied by enhanced non-vitamin D receptor-mediated protein-DNA interactions in the "TATA" box region (nucleotides -44 to +23), which also contains a potential glucocorticoid responsive element. Evidence for proximity of the VDRE with the basal regulatory elements is provided by two features of nuclear architecture. (a) Nuclear matrix attachment elements in the rat OC gene promoter that bind nuclear matrix proteins with sequence specificity may impose structural constraints on promoter conformation. (ii) Limited micrococcal nuclease digestion and Southern blot analysis indicate that three nucleosomes can be accommodated in the sequence spanning the OC gene VDRE,
Journal of Cellular Physiology, 2008
Binding of 1a,25-dihydroxy vitamin D 3 to the C-terminal ligand-binding domain (LBD) of its receptor (VDR) induces a conformational change that enables interaction of VDR with transcriptional coactivators such as members of the p160/SRC family or the DRIP (vitamin D receptor-interacting complex)/Mediator complex. These interactions are critical for VDR-mediated transcriptional enhancement of target genes. The p160/SRC members contain intrinsic histone acetyl transferase (HAT) activities that remodel chromatin at promoter regulatory regions, and the DRIP/Mediator complex may establish a molecular bridge between the VDR complex and the basal transcription machinery. Here, we have analyzed the rate of recruitment of these coactivators to the bone-specific osteocalcin (OC) gene in response to short and long exposures to 1a,25-dihydroxy vitamin D 3 . We report that in intact osteoblastic cells VDR, in association with SRC-1, rapidly binds to the OC promoter in response to the ligand. The recruitment of SRC-1 correlates with maximal transcriptional enhancement of the OC gene at 4 h and with increased histone acetylation at the OC promoter. In contrast to other 1a,25-dihydroxy vitamin D 3 -enhanced genes, binding of the DRIP205 subunit, which anchors the DRIP/Mediator complex to the VDR, is detected at the OC promoter only after several hours of incubation with 1a,25-dihydroxy vitamin D 3 , concomitant with the release of SRC-1. Together, our results support a model where VDR preferentially recruits SRC-1 to enhance bone-specific OC gene transcription.
Nucleic Acids Research, 2011
A global understanding of the actions of the nuclear hormone 1a,25-dihydroxyvitamin D 3 (1a,25(OH) 2 D 3 ) and its vitamin D receptor (VDR) requires a genomewide analysis of VDR binding sites. In THP-1 human monocytic leukemia cells we identified by ChIP-seq 2340 VDR binding locations, of which 1171 and 520 occurred uniquely with and without 1a,25(OH) 2 D 3 treatment, respectively, while 649 were common. De novo identified direct repeat spaced by 3 nucleotides (DR3)-type response elements (REs) were strongly associated with the ligand-responsiveness of VDR occupation. Only 20% of the VDR peaks diminishing most after ligand treatment have a DR3type RE, in contrast to 90% for the most growing peaks. Ligand treatment revealed 638 1a,25(OH) 2 D 3 target genes enriched in gene ontology categories associated with immunity and signaling. From the 408 upregulated genes, 72% showed VDR binding within 400 kb of their transcription start sites (TSSs), while this applied only for 43% of the 230 downregulated genes. The VDR loci showed considerable variation in gene regulatory scenarios ranging from a single VDR location near the target gene TSS to very complex clusters of multiple VDR locations and target genes. In conclusion, ligand binding shifts the locations of VDR occupation to DR3-type REs that surround its target genes and occur in a large variety of regulatory constellations.
Proceedings of The National Academy of Sciences, 1990
The regulation of osteocalcin gene expression by 1,25-dihydroxyvitamin D3 is mediated by the vitamin D receptor and a cis-acting DNA response element that has been identified within the 5' region of the osteocalcin promoter. In this report, we show that vitamin D receptors derived from nuclear extracts of mammalian cells bind directly to this cis-acting element in vitro and do so in a manner requiring hormone. Vitamin D receptors derived from reticulocyte lysate translations in vitro or from extracts of a Saccharomyces cerevisiae strain that expresses the recombinant protein also bind the osteocalcin responsive element, but only when nuclear extracts of mammalian cells are provided. The vitamin-Dreceptor-DNA-binding accessory factor is isolated by salt extraction, labile to temperature, and sensitive to tryptic digestion. These studies suggest that the high-affinity interaction of the vitamin D receptor with the osteocalcin vitamin D response element in vitro requires both 1,25-dihydroxyvitamin D3 and an accessory protein derived from the mammalian cell nucleus.
The Journal of Steroid Biochemistry and Molecular Biology, 2007
Binding of 1α,25-dihydroxy vitamin D3 to the C-terminal domain (LBD) of its receptor (VDR), induces a conformational change that enables interaction of VDR with transcriptional coactivators such as the members of the p160/SRC family or the DRIP (Vitamin D Interacting Complex)/ Mediator complex. These interactions are critical for VDR-mediated transcriptional enhancement of target genes. Recent reports indicate that nuclear receptors, including VDR, interact with p160/ SRC members and the DRIP/Mediator complex in a sequential, cyclical, and mutually exclusive manner when bound to a target promoter, exhibiting also a high exchange rate. Here, we present an overview of how these coactivators are recruited to the bone-specific osteocalcin (OC) gene in response to short and long exposures to 1α,25-dihydroxy vitamin D3. We find that in intact osteoblastic cells VDR and SRC-1 rapidly bind to the OC promoter in response to the ligand. This recruitment correlates with transcriptional enhancement of the OC gene and with increased histone acetylation at the OC promoter. In contrast, binding of the DRIP205 subunit, which anchors the DRIP/Mediator complex to the VDR, is detected at the OC promoter after several hours of incubation with 1α,25-dihydroxy vitamin D3. Together, our results indicate that VDR preferentially recruits SRC-1 to enhance basal bone-specific OC gene transcription. We propose a model where specific protein-DNA and protein-protein interactions that occur within the context of the OC gene promoter in osteoblastic cells stabilize the preferential association of the VDR-SRC-1 complex.