Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Micromolar concentrations of aluminum sulfate consistently stimulated [3H]thymidine incorporation into DNA and increased cellular alkaline phosphatase activity (an osteoblastic differentiation marker) in osteoblast-line cells of chicken and human. The stimulations were highly reproducible, and were biphasic and dose-dependent with the maximal stimulatory dose varied from experiment to experiment. The mitogenic doses of aluminum ion also stimulated collagen synthesis in cultured human osteosarcoma TE-85 cells, suggesting that aluminum ion might stimulate bone formation in vitro. The effects of mitogenic doses of aluminum ion on basal osteocalcin secretion by normal human osteoblasts could not be determined since there was little, if any, basal secretion of osteocalcin by these cells. 1,25 Dihydroxyvitamin D3 significantly stimulated the secretion of osteocalcin and the specific activity of cellular alkaline phosphatase in the human osteoblasts. Although mitogenic concentrations of aluminum ion potentiated the 1,25 dihydroxyvitamin D3-dependent stimulation of osteocalcin secretion, they significantly inhibited the hormone-mediated activation of cellular alkaline phosphatase activity. Mitogenic concentrations of aluminum ion did not stimulate cAMP production in human osteosarcoma TE 85 cells, indicating that the mechanism of aluminum ion does not involve cAMP. The mitogenic activity of aluminum ion is different from that of fluoride because (a) unlike fluoride, its mitogenic activity was unaffected by culture medium changes; (b) unlike fluoride, its mitogenic activity was nonspecific for bone cells; and (c) aluminum ion interacted with fluoride on the stimulation of the proliferation of osteoblastic-line cells, and did not share the same rate-limiting step(s) as that of fluoride. PTH interacted with and potentiated the bone cell mitogenic activity of aluminum ion, and thereby is consistent with the possibility that the in vivo osteogenic actions of aluminum ion might depend on PTH. In summary, low concentrations of aluminum ion could act directly on osteoblasts to stimulate their proliferation and differentiation by a mechanism that is different from fluoride.
Mol Cell Biochem 1991 Jul 10
PMID:Aluminum stimulates the proliferation and differentiation of osteoblasts in vitro by a mechanism that is different from fluoride. 192 12

Expression of the human osteocalcin promoter is negatively regulated by glucocorticoids in vivo. In vitro DNase I and exonuclease III footprinting analysis showed binding of purified glucocorticoid receptor in close proximity to and overlapping with the TATA box of the osteocalcin gene. These results imply competition or interference with binding of the TATA box-binding transcription factor IID as a mechanism of repression of this gene by glucocorticoids. In support of this notion, point mutation analysis of the receptor binding site indicated that flanking nucleotides and not the TATA box motif per se were important for receptor interaction. Moreover, DNA binding competition assays showed specific binding of the receptor only to the TATA box region of the osteocalcin gene and not to the corresponding region of an immunoglobulin heavy-chain promoter.
Mol Cell Biol 1991 Jun
PMID:The glucocorticoid receptor binds to a sequence overlapping the TATA box of the human osteocalcin promoter: a potential mechanism for negative regulation. 203 39

The syndrome of hereditary resistance to 1,25-dihydroxyvitamin D3 is due to defective function of the vitamin D receptor (VDR). The recent cloning and nucleotide sequence determination of the human VDR chromosomal gene have enabled a direct evaluation of the genetic basis for this disease in affected patients. In this report we employed polymerase chain reaction techniques to amplify the gene exons that encode the DNA-binding domain of the VDR from two 1,25-dihydroxyvitamin D3-resistant patients whose receptors displayed defective binding to nonspecific DNA. Although their families were apparently unrelated, each patient displayed an identical homozygous point mutation within the third exon, a mutation that causes substitution of a glutamine for an arginine residue highly conserved within the entire steroid receptor superfamily. We introduced this base change into the normal VDR cDNA via site-directed mutagenesis, transfected an expression vector containing this cDNA into cells, and examined the functional properties of the resultant VDR expression product. The produced mutant receptor bound 1,25-dihydroxyvitamin D3 with normal affinity, but displayed weak affinity for the nuclear fraction and for heterologous DNA. More importantly, the protein was inactive in promoting transcription in a cotransfection assay employing a chloramphenicol acetyltransferase gene reporter fused down-stream of the VDR-inducible osteocalcin gene promoter-enhancer. These results provide the genetic and functional basis for the phenotype of rickets in this inherited disease.
Mol Endocrinol 1990 Apr
PMID:A unique point mutation in the human vitamin D receptor chromosomal gene confers hereditary resistance to 1,25-dihydroxyvitamin D3. 217 43

The human vitamin D receptor (VDR) has been cloned recently. Two cDNAs comprising the full-length VDR were spliced, cloned into a mammalian expression vector, and transiently expressed in COS-1 cells. The protein product exhibited properties consistent with that observed for receptor in human cells. A series of 5'- and 3'-deletions of the full-length VDR cDNA was prepared and evaluated. Native DNA binding was localized to a peptide fragment (residues 1-114) whose most prominent feature is the cysteine rich region proven to represent the DNA binding domain in other steroid receptors. Steroid binding-competence required synthesis of a peptide that initiated C-terminal to the DNA-binding domain at residue 114 and which contained the remaining 313 residues. To determine the location of elements within the receptor necessary for transcription, an osteocalcin gene promoter-chloramphenicol acetyltransferase reporter gene was cotransfected together with wild type or mutant VDR cDNAs and the latter's effect on chloramphenicol acetyltransferase activity was assessed. Cotransfection of wild type receptor alone resulted in efficient transcription of the reporter plasmid. However, synthesis of a peptide containing the DNA binding domain as well as 76 residues carboxy terminal to this region exhibited some degree of activity, albeit constitutive. These results suggest that the functional domains of the VDR are similar to that of other steroid receptors and that these domains participate in the transcriptional regulation of the human osteocalcin gene.
Mol Endocrinol 1989 Apr
PMID:Functional domains of the human vitamin D3 receptor regulate osteocalcin gene expression. 254 79

The human osteocalcin gene is regulated in mammalian osteoblasts by 1,25(OH)2D3-dependent and -independent mechanisms. The sequences responsible for this activity have been mapped to within the -1339 region of the gene. We show here that this enhancer region functions analogously in Saccharomyces cerevisiae cells engineered to produce active 1,25(OH)2D3 receptor. When fused to the proximal promoter elements of the yeast iso-1-cytochrome c gene, the enhancer demonstrated substantial promoter activity. This activity was elevated further by 1,25(OH)2D3 when the reporter constructs were assayed in cells containing the 1,25(OH)2D3 receptor. This system affords a model for 1,25(OH)2D3 action and represents a simple assay system that will enable definition of the important cis-acting regulatory sequences within the osteocalcin gene and identification of their cognate transcription factors.
Mol Cell Biol 1989 Aug
PMID:Reconstitution of the vitamin D-responsive osteocalcin transcription unit in Saccharomyces cerevisiae. 255 96

Rats were raised in the absence of vitamin D in utero and throughout post-fetal life and neither 1,25-dihydroxyvitamin D3 nor related metabolites were detected in serums. No changes were observed in the relative amount of extractable noncollagenous bone proteins (NCP) in rachitic compared to vitamin-D-repleted animals. As expected, the relative levels of the mineral-bound, serum-derived albumin and alpha 2HS glycoprotein were unaffected in bones of rachitic animals. Interestingly, the vitamin D deficiency also did not have dramatic effects on several bone cell-derived noncollagenous proteins including: bone proteoglycans I & II, bone sialoprotein II osteonectin, and osteocalcin. In contrast to the proteoglycans, the bone sialoprotein II and osteonectin were found in the nonmineral compartment of the rachitic animals, presumably bound to the wide osteoid seam.
Mol Cell Biochem 1987 Apr
PMID:Noncollagenous bone proteins in experimental rickets in the rat. 360 Jun 17

Gamma-carboxyglutamic acid is an amino acid with a dicarboxylic acid side chain. This amino acid, with unique metal binding properties, confers metal binding character to the proteins into which it is incorporated. This amino acid has been discovered in blood coagulation proteins (prothrombin, Factor X, Factor IX, and Factor VII), plasma proteins of unknown function (Protein C, Protein S, and Protein Z), and proteins from calcified tissue (osteocalcin and bone-Gla protein). It has also been observed in renal calculi, atherosclerotic plaque, and the egg chorioallantoic membrane, among other tissues. Gamma-carboxyglutamic acid is synthesized by the post-translational modification of glutamic acid residues. This reaction, catalyzed by a hepatic carboxylase, requires reduced vitamin K, oxygen, and carbon dioxide. The function of gamma-carboxyglutamic acid is uncertain. In prothrombin gamma-carboxyglutamic acid residues bound to metal ions participate as an intramolecular non-covalent bridge to maintain protein conformation. Additionally, these amino acids participate in the calcium-dependent molecular assembly of proteins on membrane surfaces through intermolecular bridges involving gamma-carboxyglutamic acid and metal ions.
Mol Cell Biochem 1981 Sep 25
PMID:Gamma-carboxyglutamic acid. 645 61

Human osteosarcoma and fibrosarcoma cell lines were investigated for alterations in oncogenes, tumor suppressor genes, and growth factors, all of which have been implicated in tumor formation. Characterization of oncogenes that are involved in osteosarcoma formation, including the c-fos and c-myc oncogenes, indicated that all six osteosarcoma cell lines examined had 5- to 20-fold amplification of the c-myc oncogene, whereas neither of two fibrosarcoma cell lines c-myc amplification. Interestingly, only three of six osteosarcoma cell lines displayed altered c-myc immediate-early gene function. c-fos was found to be normal, both at the gene and functional levels, in all six osteosarcoma and both fibrosarcoma cell lines tested. Characterization of two tumor suppressor genes, p53 and RB1, that have been implicated in osteosarcoma formation indicated that p53 was altered in five of six osteosarcoma cell lines, whereas RB1 was altered in only two or six of these cell lines. Neither RB1 nor p53 was found to be altered in the fibrosarcoma cell lines tested. An additional transformation marker, autocrine growth-factor production, was observed in all six osteosarcoma cell lines and both fibrosarcoma cell lines examined. Finally, the differentiation state of the osteosarcoma cell lines was investigated via the bone differentiation markers alkaline phosphates and osteocalcin. Alkaline phosphatase activity was observed in four of six osteosarcoma cell lines but not in the two fibrosarcoma cell lines examined. The alkaline phosphatase activity was a result of the expression of the bone/liver/kidney alkaline phosphatase isoform. High-level osteocalcin expression was observed in one of the osteosarcoma cell lines but not in the two fibrosarcoma cell lines examined, although all cell lines demonstrated low-level osteocalcin expression. Together, these data demonstrate that relatively undifferentiated osteosarcomas commonly display c-myc amplification, p53 and RB1 mutation, and autocrine growth-factor production, all of which may play a role in osteosarcomagenesis.
Mol Carcinog 1995 Nov
PMID:Analysis of oncogenes, tumor suppressor genes, autocrine growth-factor production, and differentiation state of human osteosarcoma cell lines. 757 9

The nuclear vitamin D receptor (VDR) binds the 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) hormone with high affinity and elicits its actions to stimulate gene expression in target cells by binding to the vitamin D-responsive element (VDRE). VDREs in such positively controlled genes as osteocalcin, osteopontin, beta 3 integrin and vitamin D-24-OHase are direct hexanucleotide repeats with a spacer of three nucleotides. The present studies of VDR/VDRE interaction utilized full-length human vitamin D receptor (hVDR) that was overexpressed in E. coli, purified to near homogeneity (> 95%), and its authenticity confirmed by demonstrating high affinity hormone binding and reactivity to monoclonal antibody 9A7 gamma. The expressed hVDR displays strict dependence on the family of retinoid X receptors (RXRs) for binding to the vitamin D-responsive element (VDRE) in the rat osteocalcin gene. Similar overexpression in E. coli of the DNA binding domain (delta 134), containing only residues 4-133 of hVDR, generated a receptor species that possesses intrinsic DNA binding activity. Both full-length and delta 134 hVDRs retain similar DNA binding specificities when tested with several natural hormone responsive elements, indicating that the N-terminal zinc finger region determines hVDR-DNA sequence selectivity. The C-terminal region of the molecule is required for hormone binding and confers the receptor with the property of very high affinity DNA binding, via heterodimerization between hVDR and RXR. A natural ligand for the RXR co-receptor, 9-cis retinoic acid, suppresses both VDR-RXR binding to the VDRE and 1,25(OH)2D3 stimulated transcription, indicating that 9-cis retinoic acid recruits RXR away from VDR to instead form RXR homodimers.
J Steroid Biochem Mol Biol 1995 Jun
PMID:Receptor mediated genomic action of the 1,25(OH)2D3 hormone: expression of the human vitamin D receptor in E. coli. 762 14

Small changes in the concentrations and/or combinations of trans-acting factors can result in profound alterations in gene expression. Synergistic interaction between different classes of transcription factors bound to distinct sites within a promoter/enhancer region is one mechanism by which this can occur. Reflecting this, hormone response elements, DNA recognition sites for steroid/nuclear receptors, are often found in promoter regions organized as multiple copies or are clustered among binding sites for other trans-acting factors. To systematically examine the potential interactions between one such receptor, the vitamin D3 receptor (VDR), and other nonreceptor transcription factors, we constructed a series of reporter plasmids containing one copy of the osteopontin (Spp1) vitamin D response element (VDRE), consisting of two direct repeats spaced by 3 base pairs, and one binding site for the transcription factors SP1, NF-1, Oct-1, or AP-1. We also generated reporters either under the control of two copies of Spp1 VDRE, or a distinct VDRE from the human osteocalcin gene promoter. The various reporters were used to transiently transfect HeLa or CV-1 cells in the presence and absence of 1,25-dihydroxyvitamin D3. Our results show that VDR transactivates 12-20 times more strongly from two Spp1-VDREs than from one, indicating that VDR synergizes with itself. VDR also synergizes with the other nonreceptor factors, since we observe a 6- to 12-fold degree of synergistic induction after ligand addition, depending on the particular factor. The functional basis for the transcriptional synergism appears to be at the level of cooperative DNA binding, at least for VDR alone and VDR-Oct-1, as demonstrated in vitro by gel mobility shift assays using purified factors. Consistent with this, we show that the minimal requirement for transcriptional synergism in vivo by VDR is its DNA-binding domain.
Mol Endocrinol 1994 Dec
PMID:Transcriptional synergism between the vitamin D3 receptor and other nonreceptor transcription factors. 770 50


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