Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dopamine beta-hydroxylase catalyzes the final step in noradrenaline synthesis and is expressed exclusively in noradrenergic and adrenergic cells. In order to identify elements within the dopamine beta-hydroxylase (DBH) gene which contribute to the regulation of tissue-specific expression, we have analyzed the expression of the rat DBH promoter by transient transfection in both DBH-expressing and non-expressing cell lines. We have found that 1 kilobase of the DBH promoter can direct expression of the luciferase reporter gene in the DBH-expressing PC12, CATH.a, and SK-N-SH cell lines, but not in the non-DBH-expressing C6 glioma or CA77 cell lines. This activity was localized to a region between -133 and -173 upstream of the transcription start site. This element, however, also directed expression in non-DBH-expressing cell lines, but was inhibited when sequences between -212 and -388 were included. This inhibitory region contains sequences homologous to a silencer element recently identified in the human DBH gene, and shares homology with other previously identified silencer elements. Gel retardation experiments demonstrate that the rat DBH inhibitory region and the silencer elements found in the rat sodium type II channel and SCG10 genes bind a similar factor. The region between -133 and -173, which contains a consensus cyclic AMP response element (CRE), was also found to be responsive to cAMP in both DBH-expressing and non-expressing cells. Inclusion of sequences between -173 and -190 diminished the cAMP induction in PC12 cells, and nearly abolished the induction in C6 and CA77 cells, suggesting the presence of an additional negative element which inhibits cAMP induction in non-DBH expressing cells. DNA binding assays using antibodies to CRE binding protein-related transcription factors identified ATF-1 binding to the rat DBH-CRE, and further suggest that inhibition of cAMP regulation may be due to inhibition of ATF-1 binding by an additional factor, which binds to the DBH promoter immediately upstream of the CRE. These results demonstrate the importance of both positive and negative regulatory elements in the regulation of tissue-specific expression of the rat DBH gene.
 ...
PMID:Positive and negative elements contribute to the cell-specific expression of the rat dopamine beta-hydroxylase gene. 901 68

We previously isolated a 1.3-kb genomic fragment in the 5'-flanking region of the murine neuropeptide Y (NPY) Y1 receptor gene, which is able to drive the expression of LacZ reporter gene in neuronal cells. We determined the ability of deletion mutants of this region to modulate transcription of the heterologous luciferase gene in the Y1 receptor-expressing neuroblastoma/ glioma NG108-15 cells and the Y1 receptor-deficient 293 cells. Results suggest the presence of a cell type-specific core promoter (-399 to -218 from the initiator ATG) and, upstream, of two positive and two negative regulatory elements. Sequence analysis of the Y1 receptor promoter identified two decameric sequences corresponding to consensus binding sites for nuclear factor-kappa B/Rel proteins. Gel shift analysis indicated that a 29-bp oligonucleotide comprising the two putative kappa B sites, which we refer to as Y1-kappa B sequence, specifically binds kappa B-related complexes in nuclear extracts from rat brain areas, NG108-15 cells, and the murine T cell clone A.E7. In nuclear extracts from A.E7 and NG108-15 cells, the Y1-kappa B sequence specifically binds an additional complex whose molecular nature remains to be elucidated. Through transient transfection studies, we also demonstrated that the Y1-kappa B sequence acts as an enhancer element, inferring its potential role in regulation of the Y1 receptor gene expression.
 ...
PMID:Regulation of mouse neuropeptide Y Y1 receptor gene transcription: a potential role for nuclear factor-kappa B/Rel proteins. 901 43

omega-Conotoxin-sensitive N-type Ca2+ channels, unlike dihydropyridine-sensitive L-type channels, are exclusively expressed in nervous tissues. To understand the molecular basis for neuron-specific expression of the N-type channel, we have isolated genomic clones encoding the human alpha1B subunit gene, localized to the long arm of chromosome 9 (9q34) by fluorescence in situ hybridization, and characterized its 5'-upstream region. The proximal promoter of the alpha1B subunit gene lacks a typical TATA box, is highly GC-rich, and contains several sequences for transcription factor binding. Primer extension experiments revealed the presence of two transcription start sites. In vitro transfection study of the alpha1B subunit-luciferase fusion gene showed that the 4.0-kb 5'-flanking region of the alpha1B gene functions as an efficient promoter in neuronal cells but not in glioma or nonneuronal cells, consistent with the patterns of the endogenous alpha1B gene expression in these cells. Deletion analysis of alpha1B subunit-luciferase fusion gene constructs further revealed the presence of several cis-acting regulatory elements, including a potential repressor located in the distal upstream region (-3992 to -1788) that may be important for the neuron-specific expression of the N-type Ca2+ channel alpha1B subunit gene.
 ...
PMID:Isolation and characterization of the 5'-upstream region of the human N-type calcium channel alpha1B subunit gene. Chromosomal localization and promoter analysis. 903 May 75

The cyclopentenone PGs (PGA and PGJ series) inhibit tumor cell proliferation in vitro and tumorigenesis in vivo via mechanisms that are at present poorly understood. The C6 rat glioma cell line synthesizes and secretes insulin-like growth factor-I (IGF-I), which is believed to act as an autocrine factor for these cells. PGA2 inhibits the proliferation of the C6 cells and causes an increase in the fraction of cells in the G1 phase of the cell cycle. The inhibition of cell proliferation by PGA2 is accompanied by a decrease in the abundance of IGF-I messenger RNA (mRNA). This regulation of IGF-I gene expression is specific, as the abundance of hypoxanthine-guanine phosphoribosyl transferase (HPRT) and ubiquitin mRNA is not significantly affected by PGA2. The repression of IGF-I gene expression is observed at PGA2 concentrations as low as 10 microM and is evident within 4 h after treatment of the C6 cells with PGA2. In addition to specifically regulating the expression of the IGF-I gene, PGA2 also decreases the abundance of cyclin D1 mRNA and increases the abundance of Waf1 mRNA. The inhibition of cell proliferation by PGA2 is partially reversed by coaddition of IGF-I, indicating partial dominance of IGF-I action over PGA2 action. To investigate the molecular basis for the regulation of IGF-I gene expression by PGA2, we developed a sensitive RT-PCR assay for IGF-I nuclear transcripts. A similar assay was developed for quantifying HPRT transcripts, which were used as a control. Treatment of the C6 cells with 20 microM PGA2 resulted in approximately a 6-fold decrease in IGF-I mRNA and IGF-I nuclear transcripts. In contrast, HPRT mRNA and nuclear transcript levels were not significantly affected by PGA2. These results indicate that the decrease in IGF-I mRNA abundance that occurs in response to PGA2 is caused largely by a decrease in IGF-I nuclear transcript levels. To identify the cis-acting element that mediates the effect of PGA2 on IGF-I transcription, C6 cells were transiently transfected with IGF-I/luciferase expression constructs in which luciferase transcription is driven by IGF-I P1 promoter fragments extending from -1711 to -328 or from -1114 to +328 relative to the beginning of exon 1. Treatment of cells with PGA2 in these transient transfection assays did not decrease luciferase activity. These results suggest that the cis-acting regulatory element required for the response to PGA2 is located outside the -1711 to +328 promoter interval.
 ...
PMID:Prostaglandin A2 specifically represses insulin-like growth factor-I gene expression in C6 rat glioma cells. 904 99

Basic fibroblast growth factor (FGF-2) is abundant in the developing and adult brain and has been linked with the origin and growth of neuronal and glial cells. Glial cells produce high levels of FGF-2, stimulating autocrine growth as well as the survival and function of neurons in a paracrine manner. Abnormal levels of FGF-2 have been linked with Alzheimer's, Huntington's, and Parkinson's diseases. Recent evidence has suggested that a component of the mitogenic response of glial cells is exerted on FGF-2 at the transcriptional level. To assess transcriptional regulation of this potent growth factor, we cloned a 1.4-kb genomic fragment containing the rat FGF-2 promoter region. DNA blotting results indicated that the rat FGF-2 gene exists as a single copy in the genome. The promoter region contains no TATA box but appears to rely instead on multiple GC-rich start sites (P0, P1, and P2) for transcription initiation in rat brain as well as C6 glioma cells. One of these sites (P0) was located within four nucleotides of the reported 5' end of the rat brain cDNA and constituted part of a consensus Egr-1 binding site (5'-GCGGGGGCG-3'). Transcription from this site could be stimulated in C6 glioma cells in response to phorbol ester treatment. The induction of a "new" site (P1) with phorbol ester also suggested a mechanism to explain the discrepancy between the reported "starts" for the ovarian versus brain cDNAs. A hybrid luciferase gene directed by rat FGF-2 5'-flanking DNA (-1,058/+54) was expressed in rat glioma C6, heart myoblast H9c2, and human astrocytoma U87-MG cells after gene transfer. The level of transfected FGF-2 promoter activity was higher in glial cells (C6 and U87-MG) compared with nonglial (H9c2) cells. Also, expression of this hybrid FGF-2/luciferase gene was increased in response to phorbol ester or serum treatment of C6 cells. Deletion analysis revealed the presence of both positive and negative regulatory regions that are involved in the transcriptional control of rat FGF-2 gene by mitogenic stimuli.
 ...
PMID:Cloning of the rat fibroblast growth factor-2 promoter region and its response to mitogenic stimuli in glioma C6 cells. 904 34

The posttranscriptional regulation of GLUT1 glucose transporter gene expression may be mediated by specific interactions between cytosolic trans-acting factors and regulatory cis-elements within the 3'-untranslated regions (UTRs) of the GLUT1 mRNA. Recent studies demonstrate that experimental and human brain tumors express an 80-kDa protein that reacts with a specific sequence around nucleotide 2,200 within the GLUT1 mRNA 3'-UTR. The 80-kDa protein is selectively expressed in hemangioblastoma, a tumor characterized by overexpression of GLUT1. The enhancer role of this GLUT1 3'-UTR cis-element was confirmed in the present studies using the luciferase expression vector pGL2 and site-directed deletion. Transfection of C6 glioma cells with pGL2 (containing nucleotides 2,100-2,300 of the bovine GLUT1 3'-UTR inserted at the Pfl MI site within the luciferase 3'-UTR) results in a fivefold increase in luciferase gene expression. Deletion of nucleotides 2,181-2,190 of the bovine GLUT1 3'-UTR, i.e., the putative binding site of the 80-kDa protein, completely eliminated the enhancement of luciferase activity in the transfected cells. Luciferase mRNA containing the putative cis-element inserted in the 3'-UTR was transcribed, and after UV crosslinking, this mRNA complexed with the 80-kDa protein in cytosol of either C6 cells or hemangioblastoma. In contrast, this complex was undetected with either luciferase control mRNA or 10 nucleotide-deleted RNA. The present study provides evidence that nucleotides 2,181-2,190 of the bovine GLUT1 mRNA 3'-UTR forms a complex with brain tumor cytosolic proteins that serves to increase GLUT1 gene expression at the posttranscriptional level.
 ...
PMID:Site-directed deletion of a 10-nucleotide domain of the 3'-untranslated region of the GLUT1 glucose transporter mRNA eliminates cytosolic protein binding in human brain tumors and induction of reporter gene expression. 916 56

S100 beta is a calcium-binding protein produced and secreted by glial cells in the central and peripheral nervous systems. S100 beta promotes neuronal differentiation and survival but may be detrimental to cells if overexpressed. The selective overproduction of S100 beta has been implicated in the progression of the neuropathological changes in Alzheimer's disease. In addition, at high concentrations, S100 beta stimulates toxic intracellular pathways in cultured cells. To begin to define the regulation of S100 beta expression, we characterized the human S100 beta promoter and mapped its upstream regulatory elements by using a luciferase reporter system. The functional S100 beta promoter was localized to a region -168/ +697 containing 168 bp upstream of the transcription initiation site of the gene. This minimal promoter was active in a variety of cell types, including those of glial, neuronal, and non-neural origin. The human S100 beta promoter activity is regulated by both positive and negative regulatory elements located upstream in the 5' flanking DNA regions. The regions -788/ -391 and -1012/ -788 contain strong positive, cell type-specific regulatory elements. Negative regulatory elements were mapped to the more distal -4437/ -1012 and -1012/ -788 regions of the gene. The -4437/ -1012 negative element suppressed promoter activity in all cell types examined, except C6 glioma cells. These data demonstrate that the expression of the human S100 beta gene is under complex transcriptional regulation that allows for precise control of the S100 beta level in the nervous system.
 ...
PMID:Transcriptional regulation of the human S100 beta gene. 919 Oct 95

Because accurate regulation of toxin gene expression is critical for safe and effective gene therapy applications, the authors have examined the regulation of diphtheria toxin A (DTA) fragment expression in human glioma cell lines using two transcriptional control systems derived from Escherichia coli: the tetracycline (Tet) system and the lactose (Lac) system. The Tet system includes a tetracycline-controlled transactivator (tTA), a tTA-responsive minimum human cytomegalovirus (hCMV) promoter controlling the expression of the DTA gene, and tetracycline as an allosteric inhibitor. The Lac system includes the lac repressor (lacR), a lacR-regulated Rous sarcoma virus-long terminal repeat (RSV-LTR) promoter controlling the expression of the DTA gene, and isopropyl-thio-beta-D-galactoside (IPTG) as an allosteric inducer. Expression plasmids encoding either tTA or lacR were transfected into U-87MG and U-343MG glioma cells along with the responsive DTA plasmid. Cell killing was monitored by the ability of the toxin to abolish protein synthesis and was quantitated using a luciferase reporter gene. In the Tet system, tumor cell killing could be regulated by tetracycline up to 120-fold. In contrast, only a twofold IPTG-dependent regulation was obtained using the Lac system because of an incomplete repression of DTA expression in the uninduced state. Replacement of the RSV-LTR promoter with the heavy metal-inducible mouse metallothionein-1 promoter in the lacR-responsive unit, as well as the generation of a clonal glioma cell line expressing lacR, did not significantly enhance regulation of DTA in the Lac system. In conclusion, this study demonstrates that the Tet system is of potential use in gene therapy applications in which regulated expression of a therapeutic gene is an important issue.
 ...
PMID:Regulated expression of the diphtheria toxin A gene in human glioma cells using prokaryotic transcriptional control elements. 920 71

The expression of the gene encoding the rat beta 1-adrenergic receptor is suppressed by glucocorticoids (Kiely et al., 1994). Within the 3.2-kb 5'-flanking region of the promoter, two potential glucocorticoid response elements (GREs) at -950 and -2791 relative to the translational ATG were identified. Characterization of the glucocorticoid-responsive sequences in the 5'-flanking region of the beta 1-adrenergic receptor gene was explored in rat C6 glioma cells and human HepG2 hepatoma cells using transient expression of beta 1-adrenergic receptor-luciferase fusion genes. The ability of glucocorticoids to suppress luciferase expression was not altered when the most 5'-localized GRE was deleted. Deleting the potential GRE at -950, in contrast, abolished glucocorticoid-induced suppression of the beta 1-adrenergic receptor-luciferase gene transcription. A 25-bp element containing the GRE sequence between nucleotides -950 and -926 confers glucocorticoid-dependent inhibition of transcription to a neutral promoter. Gel mobility shift assays with the alpha-subunit of the human glucocorticoid receptor (hGR alpha) expressed in reticulocyte lysates demonstrated specific binding to the 25-bp sequence harboring the putative GRE. We report an inhibitory GRE in the promoter of the rat beta 1-adrenergic receptor gene that is conserved among the rat, human, and mouse genes.
 ...
PMID:Identification of a glucocorticoid repressor domain in the rat beta 1-adrenergic receptor gene. 925 49

The endothelial cell-specific mitogen vascular-endothelial growth factor (VEGF) plays a key role in both physiological and pathological angiogenesis. The up-regulation of VEGF expression in response to reduced oxygen tension occurs through transcriptional and post-transcriptional mechanisms. To investigate the molecular mechanisms of transcriptional activation by hypoxia (1% oxygen), fine mapping of a hypoxia-responsive region of the human VEGF promoter was carried out using luciferase reporter-gene constructs in C6 glioma cells. Here, we report that the binding site of hypoxia-inducible factor 1 (HIF1) is crucial for the hypoxic induction of VEGF gene expression. However, an enhancer subfragment containing the HIF1 binding site was not sufficient to confer full hypoxia responsiveness. Addition of upstream sequences restored the full sensitivity to hypoxia induction. This potentiating effect is due to activator protein 1 binding. The 'potentiating' sequences are unable to confer hypoxia responsiveness on their own. Our results strongly suggest that in C6 glioma cells a complex array of trans-acting factors facilitates full transcriptional induction of VEGF gene expression by hypoxia.
 ...
PMID:Activator-protein-1 binding potentiates the hypoxia-induciblefactor-1-mediated hypoxia-induced transcriptional activation of vascular-endothelial growth factor expression in C6 glioma cells. 935 10


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>