Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucocorticoids inhibit basal and hormone-induced phosphoenolpyruvate carboxykinase (PEPCK) gene transcription in adipocytes whereas beta-adrenergic agonists and fibrates are stimulatory. Here we show that dexamethasone inhibits the induction of PEPCK mRNA by isoprenaline or clofibrate in 3T3-F442A adipocytes. RU 38486 antagonizes dexamethasone effect, suggesting the involvement of the glucocorticoid receptor. In H4IIE hepatoma cells, glucocorticoids enhance PEPCK gene transcription through a complex region which encompasses an element, AF1, with a direct repeat 1-type sequence. Mutations in the AF1 sequence abolish binding of nuclear factors from liver and from 3T3-F442A adipocytes. We transiently transfected 3T3-F442A cells with a wild type or an AF1-mutated PEPCK-CAT construct comprising -2100 to +69 base pairs of the promoter fused to the chloramphenicol acetyltransferase (CAT) gene. With both constructs, CAT activity is decreased by dexamethasone and is increased by isoprenaline or by clofibrate. However, dexamethasone is unable to inhibit clofibrate induction of CAT activity in cells transfected with the AF1-mutated construct whereas it prevents isoprenaline action on both constructs. Hence, although a single hormone can repress stimulations originating from different intracellular routes, sites in the promoter which mediate inhibition of a specific stimulation are distinct.
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PMID:Glucocorticoids use a positive liver element to repress fibrate-induced adipose transcription of the phosphoenolpyruvate carboxykinase gene. 909 12

We analysed the glucocorticoid receptor (GR) function and its ability to modulate cell-cell interactions between the PA-III rat prostate cancer and UMR 106 osteoblast-like rat osteosarcoma cells as an in vitro model for studying GR function in PA-III cell-induced tumor and blastic reaction in rat bone. Intact GR was detected by ligand binding assays, DNA band-shift, and GR trans-activation analysis of PA-III and UMR 106 cells transiently transfected with the mouse mammary tumor virus thymidine kinase-chloramphenicol acetyltransferase reporter gene. Dexamethasone and transforming growth factor beta 1 (TGFbeta1) inhibited the growth of PA-III and UMR 106 cells. Dexamethasone's inhibition of PA-III and UMR 106 cells was reversed by anti-TGFbeta1 antibody and exogenous insulin-like growth factor I (IGF-I). Exogenous IGF-I, urokinase-type plasminogen activator (uPA), UMR 106 conditioned media (CM) and PA-III CM stimulated the proliferation of PA-III and UMR 106 cells. The mitogenic activity exerted by uPA and PA-III CM in UMR 106 cells was completely neutralized by anti-IGF-I specific antibody. In addition, dexamethasone up-regulated TGFbeta1 mRNA and down-regulated uPA mRNA expression in PA-III cells without affecting TGFbeta1 and uPA mRNA expression in UMR 106 cells. These data suggested that TGFbeta1, uPA, and IGF-I mediate at least in part cell-cell interactions and GR function in PA-III prostate cancer and UMR 106 osteosarcoma cells.
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PMID:Glucocorticoid receptor function possibly modulates cell-cell interactions in osteoblastic metastases on rat skeleton. 917 22

Steroid hormone receptors and Stat factors comprise two distinct families of inducible transcription factors. Activation of a member of each family, namely the glucocorticoid receptor by glucocorticoids and Stat5 by prolactin, is required for the efficient induction of the expression of milk protein genes in the mammary epithelium. We have studied the mode of interaction between Stat5 and the glucocorticoid receptor in the activation of beta-casein gene transcription. The functional role of potential half-palindromic glucocorticoid receptor-binding sites mapped previously in the promoter region was investigated. beta-Casein gene promoter chloramphenicol acetyltransferase constructs containing mutations and deletions in these sites were tested for their responsiveness to the synergistic effect of prolactin and dexamethasone employing COS-7 cells or HC11 mammary epithelial cells. Synergism depended on promoter regions containing intact binding sites for the glucocorticoid receptor and Stat5. The carboxyl-terminal transactivation domains of Stat5a and Stat5b were not required for this synergism. Our results suggest that in lactogenic hormone response elements glucocorticoid receptor molecules bound to nonclassical half-palindromic sites gain competence as transcriptional activators by the interaction with Stat5 molecules binding to vicinal sites.
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PMID:Promoter-dependent synergy between glucocorticoid receptor and Stat5 in the activation of beta-casein gene transcription. 925 24

The glucocorticoid receptor (GR) is a ligand-regulated transcription factor that in its unactivated form resides primarily in the cytoplasm. After being bound by steroid, the GR undergoes a conformational change and translocates to the nucleus, where it influences gene transcription. Because the GR mediates negative feedback exerted by circulating glucocorticoid hormones on the hypothalamic-pituitary-adrenal (HPA) axis, it has been hypothesized that abnormalities in GR expression and/or function may underlie the HPA axis hyperactivity described in patients with major depression. In further support of this hypothesis, animal studies have shown that long term in vivo treatment with antidepressants enhances glucocorticoid feedback inhibition, possibly through a direct effect on the GR. To examine this latter possibility, we evaluated translocation of the GR from the cytoplasm to the nucleus after 24-hr in vitro treatment of L929 cells (mouse fibroblasts) with the tricyclic antidepressant desipramine (0.1-10 microM) in the presence or absence of the synthetic steroid dexamethasone. In addition, GR-mediated gene transcription was measured with the use of L929 cells stably transfected with the mouse mammary tumor virus-chloramphenicol acetyltransferase reporter gene. Desipramine was found to (i) induce GR translocation from the cytoplasm to the nucleus in the absence of steroids (with no effect alone on GR-mediated gene transcription) and (ii) potentiate dexamethasone-induced GR translocation and dexamethasone-induced GR-mediated gene transcription. Treatment with desipramine for 24-96 hr had no effect on the expression of GR protein as measured by cytosolic radioligand receptor binding. We suggest that one important aspect of the effects of antidepressants in vivo may be to facilitate GR-mediated feedback inhibition on the HPA axis, by facilitating GR translocation and function, and thereby reverse glucocorticoid hypersecretion in depression.
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PMID:Steroid-independent translocation of the glucocorticoid receptor by the antidepressant desipramine. 938 19

Cytochrome P450 (CYP) 3A23 is transcriptionally regulated in rat liver by such glucocorticoids as dexamethasone (DEX) and by such antiglucocorticoids as pregnenolone 16 alpha-carbonitrile (PCN). Based on studies of CYP3A23 gene fragments expressed in primary cultures of adult rat hepatocytes and tested for DNA-protein interactions, we have proposed that the mechanism of CYP3A23 induction by these steroid hormones involves the glucocorticoid receptor or a protein induced by glucocorticoids indirectly interacting with proteins constitutively bound to an enhancer element consisting of a direct repeat of 7-bp separated by two nucleotides in the 5'-flanking region of the CYP3A23 gene (L. Quattrochi et al., J. Biol. Chem. 270, 28,917, 1995). In the present study, we prepared and transiently expressed in cultured rat hepatocytes 20-bp double-stranded (ds)-oligonucleotides containing this direct repeat or various mutations of this direct repeat inserted into a chloramphenicol acetyltransferase (CAT) reporter plasmid. We found that both repeats were necessary for induction of CAT by either DEX or PCN. Analysis of proteins bound to CYP3A23 enhancer through the use of uv cross-linking revealed two rat liver nuclear proteins with molecular masses of approximately 130 and 100 kDa, as well as several proteins of molecular masses between 45 and 60 kDa, that specifically bind to the 20-bp ds-oligonucleotide CYP3A23 enhancer. Methylation interference assays determined that all guanine residues within the direct repeats of this oligonucleotide are important for protein binding. Mutations of these guanine residues abolished binding of nuclear proteins and eliminated DEX or PCN inducibility of CAT. These data suggest that constitutively bound proteins, interacting with the CYP3A23 enhancer possibly as a heterodimeric complex, play a role in the glucocorticoid inducibility of CYP3A23.
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PMID:Characterization of DNA-binding proteins required for glucocorticoid induction of CYP3A23. 944 12

Phosphoenolpyruvate carboxykinase (PEPCK) exerts a glyceroneogenic function in adipocytes in which transcription of its gene is increased by unsaturated fatty acids and fibrates. We used cultured rat adipose tissue fragments and 3T3-F442A adipocytes to show that the antidiabetic thiazolidinedione BRL 49653, a ligand and an activator of the gamma isoform of peroxisome proliferator activated receptors (PPARgamma), is a potent inducer of PEPCK mRNA. In 3T3-F442A adipocytes, the effect of BRL 49653 is rapid and concentration dependent, with a maximum reached at 1 microM and a half-maximum at 10-100 nM. PEPCK mRNA is similarly induced by the natural ligand of PPARgamma, the 15-deoxy-delta(12-14) prostaglandin J2. These observations strongly suggest that PPARgamma is a primary regulator of PEPCK gene expression in adipocytes. Dexamethasone at 10 nM repress induction of PEPCK mRNA by 1 microM BRL 49653, 0.32 mM oleate, or 1 mM clofibrate, in a cycloheximide-independent manner. The antiglucocorticoid RU 38486 prevents dexamethasone action, demonstrating involvement of the glucocorticoid receptor. Stable transfectants of 3T3-F442A adipocytes bearing -2100 to +69 base pairs of the PEPCK gene promoter fused to the chloramphenicol acetyltransferase (CAT) gene respond to 1 microM BRL 49653 or 1 mM clofibrate by a large increase in CAT activity, which is prevented by the simultaneous addition of 10 nM dexamethasone. Hence, in adipocytes, glucocorticoids act directly through the 5'-flanking region of the PEPCK gene to repress, in a dominant fashion, the stimulation of PEPCK gene transcription by thiazolidinediones and fibrates.
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PMID:Glucocorticoids repress induction by thiazolidinediones, fibrates, and fatty acids of phosphoenolpyruvate carboxykinase gene expression in adipocytes. 951 57

Hormone response elements (HREs) are considered enhancers, activating transcription in a relatively position- and orientation-independent fashion. Upon binding to an HRE, steroid receptors presumably contact coactivators and/or proteins associated with the transcription initiation complex. As a receptor target site is moved further from a fixed position such as the TATA box, not only will the spatial separation of the receptor with respect to its interaction partners change, so will the orientation due to the rotation of the DNA helix. Additional constraints may be imposed by the assembly of DNA into chromatin. Therefore, we have endeavored to test rigorously the assertion that HRE action is position independent. We have constructed a series of 42 chloramphenicol acetyltransferase expression vectors that contain a single progesterone/glucocorticoid receptor-binding site separated from a TATA box by 4 to 286 bp. The enhancer activity of the HRE was assessed after transient transfection of progesterone receptor-expressing fibroblasts. We find that the position of the HRE has a dramatic influence on induction by progestins. When closely juxtaposed to the TATA box, the HRE was unable to support a hormone response, perhaps due to direct steric hindrance with the transcription initiation complex. Full activity was gained by moving the HRE 10 bp further from the TATA sequence. As the HRE was moved incrementally further, activity remained near maximal over the next 26 bp. HRE activity then declined over the subsequent 26 bp and remained low for another 2.5 helical turns. Surprisingly, a narrow window of HRE activity occurred at an HRE-TATA box separation of 90-100 bp. Little or no hormone-induced transcriptional activity was observed when the HRE was positioned further from the TATA box. The addition of a second HRE or a basal (nuclear factor-1) element failed to relieve this constraint. A similar series of experiments was carried out in a mammary carcinoma cell line that expressed high levels of both glucocorticoid and progestin receptors. Data in these cells indicate that glucocorticoids and progestins supported a similar HRE position-activity profile, but this pattern of HRE activity was quite distinct from that seen in fibroblasts. This may be indicative of cell type-specific interactions between steroid receptors and adapter/coactivator proteins or cell type-specific activities such as acetylases or deacetylases participating in the steroid response.
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PMID:Extreme position dependence of a canonical hormone response element. 962 64

We have examined the human androgen receptor (hAR) for its ability to activate AR-dependent transcription of a transgene in a ligand-independent manner. The transcriptional activity was determined by analysis of chloramphenicol acetyltransferase (CAT) activity in T47D cells cotransfected with a plasmid expressing the hAR and a natural AR-regulated promoter (the MVDP androgen-dependent enhancer) ligated to the reporter CAT gene. In this study, the effects of the protein kinase C (PKC) activator 12-O-tetradecanoyphorbol-13 acetate (TPA) on AR activity were tested. We demonstrated that in the absence of androgen, TPA enhanced AR-mediated transactivation by 10-12-fold. This effect was specific of the PKC pathway since stimulation to the PKA pathway did not activate the unliganded AR. This ligand-independent pathway can function through another androgen-regulated promoter as shown by the use of the mouse mammary tumor virus MMTV-CAT reporter. The human glucocorticoid receptor (hGR) and the rabbit progesterone receptor (rPR) could not be activated by TPA, indicating that the effects are not universal for steroid receptors. A reporter plasmid containing the MVDP androgen response element (ARE) in front of the thymidine kinase promoter ligated to the CAT gene was activated by DHT but not by TPA, indicating that the context of the natural promoter is critical for ligand-independent activation of the AR. Exogenous c-jun enhanced transcriptional activation by the AR in a ligand-dependent manner, but had no effect in the absence of DHT. Base pair substitutions in both AR-binding (5'-TGTTCT-3' to 5'-TTTTTT-3') and NF1-binding (5'-GTGGCTG-3' to 5'-GTTTTTG-3') sites resulted in a loss of TPA responsiveness. Our results suggest that ligand-independent activation of the AR by TPA results from interaction of unliganded AR with other proteins in the transcription machinery.
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PMID:Phorbol ester causes ligand-independent activation of the androgen receptor. 978 Feb 30

Glucocorticoid and androgen receptors have been shown to function through the same palindromic glucocorticoid response element (GRE) and yet have differential effects on gene transcription. In this study, we examined the functional and structural relationship of the androgen and glucocorticoid receptors with the androgen responsive region (ARR) of the probasin (PB) gene containing two androgen receptor binding sites, ARBS-1 and ARBS-2. Transfection studies indicated that one copy of each cis-acting DNA element was essential for maximal androgen-induced chloramphenicol acetyltransferase (CAT) activity and that androgen selectivity was maintained when multiple copies of the minimal wild type (wt) androgen responsive region containing both ARBS-1 and ARBS-2 (-244 to -96) were subcloned in front of the thymidine kinase promoter. Furthermore, replacing the androgen response region with 1, 2 or 3 copies of either ARBS-1 or ARBS-2 restored less than 4% of the biological activity seen with the wt PB ARR. Multiple copies of either ARBS-1 or ARBS-2 did not result in glucocorticoid-induced CAT gene activity. By comparison, 1 or 2 copies of the tyrosine aminotransferase (TAT) GRE, as well as the mouse mammary tumour virus GRE, were strong inducers of CAT activity in response to both androgen and glucocorticoid treatment. In addition, band shift assays demonstrated that although the synthetic glucocorticoid receptor, GR-DNA binding domain (GR-DBD), and the synthetic androgen receptor, AR2, could interact with the TAT GRE (dissociation constants Kd of 63.9 and 14.1 respectively), only AR2 but not GR-DBD binding could be detected on ARBS-1 and ARBS-2. Our findings provide further evidence that androgen-induced regulation of gene transcription can occur through androgen-specific DNA binding sites that are distinct from the common GRE.
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PMID:Selective activation of the probasin androgen-responsive region by steroid hormones. 1034 90

The expression of carbamoyl phosphate synthetase I (CPS) gene is suppressed in the liver of carnitine-deficient juvenile visceral steatosis (JVS) mice at weaning and under starvation at adult age. To clarify the suppression mechanism, we produced CPSL transgenic JVS mice carrying a transgene composed of the chloramphenicol acetyltransferase (CAT) gene with the upstream region (-12 kb to +138) of the rat CPS gene and CPSE transgenic JVS mice carrying a transgene composed of the luciferase gene with minimal promoter (299 bp from -161 to +138) and enhancer (469 bp around -6.3 kb) fragments of the rat gene. The expression of the CAT gene as well as the endogenous CPS was suppressed in CPSL transgenic JVS mice, but luciferase gene expression was not suppressed in CPSE transgenic JVS mice. We isolated the 5'-upstream region of the mouse CPS gene and identified an activator protein-1 (AP-1) site downstream of the minimum enhancer region of both rat and mouse CPS genes. In conjunction with the 313-bp mouse promoter region, the 714-bp mouse enhancer fragment conferred a cell-type-dependent hormone responsiveness. In rat primary cultured hepatocytes, the addition of oleic acid suppressed reporter gene expression induced by dexamethasone in the construct containing the enhancer fragment of 714 bp with the AP-1 site, but not in its AP-1 site mutants or in 519 bp without the AP-1 site. These results strongly suggest that direct protein-protein interaction between AP-1 and glucocorticoid receptor is not involved in the suppression of the CPS gene in JVS mice and that the AP-1 element is the cis-element which is responsible for the suppression.
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PMID:Involvement of a cis-acting element in the suppression of carbamoyl phosphate synthetase I gene expression in the liver of carnitine-deficient mice. 1056 61


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