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)

The peripherin gene, which encodes a neuronal-specific intermediate filament protein, is transcriptionally induced with a late time course when nerve growth factor (NGF) stimulates PC12 cells to differentiate into neurons. We have studied its transcriptional regulation in order to better understand the neuronal-specific end steps of the signal transduction pathway of NGF. By 5' deletion mapping of the peripherin promoter, we have localized two positive regulatory elements necessary for full induction by NGF: a distal positive element and a proximal constitutive element within 111 bp of the transcriptional start site. In addition, there is a negative regulatory element (NRE; -179 to -111), the deletion of which results in elevated basal expression of the gene. Methylation interference footprinting of the NRE defined a unique sequence, GGCAGGGCGCC, as the binding site for proteins present in nuclear extracts from both undifferentiated and differentiated PC12 cells. However, DNA mobility shift assays using an oligonucleotide probe containing the footprinted sequence demonstrate a prominent retarded complex in extracts from undifferentiated PC12 cells which migrates with slower mobility than do the complexes produced by using differentiated PC12 cell extract. Transfection experiments using peripherin-chloramphenicol acetyltransferase constructs in which the footprinted sequence has been mutated confirm that the NRE has a functional, though not exclusive, role in repressing peripherin expression in undifferentiated and nonneuronal cells. We propose a two-step model of activation of peripherin by NGF in which dissociation of a repressor from the protein complex at the NRE, coupled with a positive signal from the distal positive element, results in depression of the gene.
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PMID:Nerve growth factor-induced derepression of peripherin gene expression is associated with alterations in proteins binding to a negative regulatory element. 158 54

Depression is often characterized by increased cortisol secretion caused by hyperactivity of the hypothalamic-pituitary-adrenal axis and by nonsuppression of cortisol secretion following dexamethasone administration. This hyperactivity of the hypothalamic-pituitary-adrenal axis could result from a reduced glucocorticoid receptor (GR) activity in neurons involved in its control. To investigate the effect of reduced neuronal GR levels, we have blocked cellular GR mRNA processing and/or translation by introduction of a complementary GR antisense RNA strand. Two cell lines were transfected with a reporter plasmid carrying the chloramphenicol acetyltransferase (CAT) gene under control of the mouse mammary tumor virus long terminal repeat (a glucocorticoid-inducible promoter). This gene construction permitted assay of the sensitivity of the cells to glucocorticoid hormones. Cells were also cotransfected with a plasmid containing 1,815 bp of GR cDNA inserted in the reverse orientation downstream from either a neurofilament gene promoter element or the Rous sarcoma virus promoter element. Northern (RNA) blot analysis demonstrated formation of GR antisense RNA strands. Measurement of the sensitivity of CAT activity to exogeneous dexamethasone showed that although dexamethasone increased CAT activity by as much as 13-fold in control incubations, expression of GR antisense RNA caused a 2- to 4-fold decrease in the CAT response to dexamethasone. Stable transfectants bearing the GR antisense gene fragment construction demonstrated a 50 to 70% decrease of functional GR levels compared with normal cells, as evidenced by a ligand-binding assay with the type II glucocorticoid receptor-specific ligand [3H]RU 28362. These results validate the use of antisense RNA to GR to decrease cellular response to glucocorticoids.
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PMID:Decreased glucocorticoid receptor activity following glucocorticoid receptor antisense RNA gene fragment transfection. 199 14

Adhesive interactions are important modulators of cellular phenotype. Previously, we demonstrated that quiescent, suspension-arrested cells are not equivalent to density-arrested cells in their patterns of gene expression (Dhawan, J., and Farmer, S.R. (1990) J. Biol. Chem. 265, 9015-9021). In particular, pro-alpha 1(I) collagen expression depended strongly on the extent of cell adhesion. In this paper, we demonstrate that the adhesion-induced rise in collagen gene expression is due to regulation at multiple levels. Steady state levels of pro-alpha 1(I) collagen mRNA increased up to 10-fold by 6 h after replating suspended cells, and this rise is blocked by inhibition of protein synthesis. Transcription of the pro-alpha 1(I) collagen gene was measured by run-on assay as well as by activation of a rat alpha 1(I) promoter-chloramphenicol acetyltransferase reporter gene construct. Both assays reveal a 5-fold depression of pro-alpha 1(I) collagen gene transcription in suspended cells. Reattachment of suspended cells resulted in the activation of alpha 1(I) gene transcription by 2-h postreplating, reaching a 3-5-fold level of induction by 18 h. The pro-alpha 1(I) collagen mRNA was substantially more labile in suspended cells than in adherent cells (t1/2 values of approximately 2 h in nonadherent cells and greater than 8 h in exponentially growing or density-arrested cells). Furthermore, reattachment of suspended cells for 18 h resulted in a stabilization of collagen mRNA. We conclude that cell adhesion regulates pro-alpha 1(I) collagen gene expression selectively and at transcriptional and posttranscriptional sites.
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PMID:Cell adhesion regulates pro-alpha 1(I) collagen mRNA stability and transcription in mouse fibroblasts. 202 61

Glucocorticoids have previously have shown to decrease Type I collagen synthesis in vivo and in fibroblast cell culture. Several studies have demonstrated that glucocorticoids decrease Type I procollagen gene expression. These latter studies have included uridine incorporation into pro alpha 1 (I) and pro alpha 2 (I) mRNAs and nuclear run-off experiments. Using the ColCat 3.6 plasmid, which contains part of the 5' flanking region of the pro alpha 1 (I) collagen gene and the reporter gene, chloramphenicol acetyltransferase, the present studies demonstrate by stable transfection of fetal rat skin fibroblasts that dexamethasone down regulates the promoter activity of the pro alpha 1 (I) collagen gene. The glucocorticoid-mediated down-regulation of procollagen gene expression was demonstrated using the ColCat 3.6, 2.4, 1.7, or 0.9 plasmid. In addition, competitive oligonucleotide transfection experiments and site specific mutation of the glucocorticoid response element (GRE) in the whole ColCat 3.6 plasmid did not eliminate the effect. The possibility existed that another cis-element in the 5' flanking region of the pro alpha 1 (I) collagen gene was also required for the collagen glucocorticoid-mediated down-regulation of procollagen gene expression, since TGF-beta has been shown to stimulate in a decrease of transforming growth factor-beta (TGF-beta) secretion into the media. Gel mobility studies demonstrated that glucocorticoid treatment of rat skin fibroblasts decreased glucocorticoid receptor binding to the GRE and TGF-beta activator protein to the TGF-beta element which were brought back to control values by coordinate exogenous TGF-beta treatment. Thus the interaction of these TGF-beta molecules with cellular membrane receptors and subsequent transduction is dramatically decreased resulting in less signals to regulate collagen gene expression. These data indicate that glucocorticoids coordinately regulate procollagen gene expression through both the GRE and TGF-beta elements. Depression of procollagen gene expression by glucocorticoids through the TGF-beta element is mediated by decreased TGF-beta secretion, possibly involving a secondary effect on regulatory protein(s) encoded by noncollagenous protein gene(s). The present studies provide the basis for a novel mechanism of glucocorticoid-mediator regulation of eukaryotic genes containing the TGF-beta element.
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PMID:Glucocorticoids coordinately regulate type I collagen pro alpha 1 promoter activity through both the glucocorticoid and transforming growth factor beta response elements: a novel mechanism of glucocorticoid regulation of eukaryotic genes. 856 55

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

Catechol-O-methyltransferase (COMT, EC 2.1.1.6) is a ubiquitous enzyme that is crucial to the metabolism of carcinogenic catechols and catecholamines. Regulation of human COMT gene expression may be important in the pathophysiology of various human disorders including estrogen-induced cancers, Parkinson's disease, depression, and hypertension. The gender difference in human COMT activity and variations in rat COMT activity during the estrous cycle led us to explore whether estrogen can regulate human COMT gene transcription. Our Northern analyses showed that physiological concentrations of 17-beta-estradiol (10(-9)-10(-7) M) could decrease human 1. 3-kilobase COMT mRNA levels in MCF-7 cells in a time- and dose-dependent manner through an estrogen receptor-dependent mechanism. Two DNA fragments immediately 5' to the published human COMT gene proximal and distal promoters were cloned. Sequence analyses revealed several half-palindromic estrogen response elements and CCAAT/enhancer binding protein sites. By cotransfecting COMT promoter-chloramphenicol acetyltransferase reporter genes with human estrogen receptor cDNA and pSV-beta-galactosidase plasmids into COS-7 cells, we showed that 17-beta-estradiol could down-regulate chloramphenicol acetyltransferase activities, and COMT promoter activities dose-dependently. Functional deletion analyses of COMT promoters also showed that this estrogenic effect was mediated by a 280 base pair fragment with two putative half-palindromic estrogen response elements in the proximal promoter and a 323-base pair fragment with two putative CCAAT/enhancer binding protein sites in the distal promoter. Our findings provide the first evidence and molecular mechanism for estrogen to inhibit COMT gene transcription, which may shed new insight into the role of estrogen in the pathophysiology of different human disorders.
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PMID:Characterization and implications of estrogenic down-regulation of human catechol-O-methyltransferase gene transcription. 1038 81

Antidepressant drugs are thought to counteract effects of hypercortisolemia, frequently associated with depression, by lowering cortisol level and by modifying the function of glucocorticoid receptors (GR). Indeed, classical antidepressants inhibit corticosteroid-induced gene transcription in cell cultures. The aim of the present study was to investigate effects of new generation antidepressant drugs on GR function in mouse fibroblast cells (L929), stably transfected with mouse mammary tumor virus-chloramphenicol acetyltransferase (MMTV-CAT) plasmid (LMCAT cells). It has been found that reboxetine (at 10 and 30 microM), venlafaxine, citalopram and mirtazapine (at 30 microM), but not milnacipran, in statistically significant manner inhibited corticosterone-induced gene transcription. However, the effects of new generation antidepressant drugs were weaker than those evoked by imipramine, which was active already at 3 microM concentration. Further studies on the mechanism of antidepressant action on GR function revealed that protein kinase C, but not mitogen-activated protein kinases (MAPK), glycogen synthase kinase (GSK-3) and protein kinase B (PKB, Akt) play a role in this phenomenon.
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PMID:Effects of some new antidepressant drugs on the glucocorticoid receptor-mediated gene transcription in fibroblast cells. 1638 95

The aim of the present study was to investigate effects of some classical and new antidepressants on functional activity of the glucocorticoid receceptor (GR) induced by low corticosterone concentration in mouse fibroblast cells stably transfected with mouse mammary tumor virus-chloramphenicol acetyltransferase plasmid (LMCAT cells). We found that the transcriptional activity of GR stimulated by 50 nM corticosterone was strongly attenuated by imipramine, desipramine, fluoxetine and tianeptine in a concentration-dependent way, whereas reboxetine had only a weak effect and venlafaxine was inactive. Further study revealed that the inhibitor of c-Jun N-terminal kinase - mitogen-activated protein kinase (JNK-MAPK), SP600125 (0.1 microM), reversed the imipramine-induced suppression of GR function, whereas the inhibitor of extracellular signal-regulated kinase (ERK)-MAPK, PD 98059 (15 microM), potentiated the antidepressant action. No effect of selective inhibitors of p38-MAPK, phosphatidylinositol 3-kinase (PI3-K)/Akt, and glycogen synthase kinase (GSK-3) on the imipramine-induced inhibition of GR function was detected. These data indicate that the functional activity of GR evoked by low corticosterone concentration in LMCAT cells is efficiently inhibited by tricyclic antidepressants. Moreover, it was found that JNK- and ERK-MAPK were oppositely involved in the regulation of the imipramine-induced inhibition of the GR functional activity. Thus, the present study supports the notion that the interaction of antidepressants with GR may play a role in attenuating pathological hyperactivity of HPA axis in depression.
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PMID:Effect of some antidepressants on the low corticosterone concentration-induced gene transcription in LMCAT fibroblast cells. 1844 95