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)

Cytokine modulation of elastin gene expression was examined by assay of elastin mRNA abundance and by transient transfections of cultured human skin fibroblasts and rat aortic smooth muscle cells with elastin promoter/reporter gene (chloramphenicol acetyltransferase, CAT) constructs. Incubation of cells with human recombinant tumor necrosis factor-alpha (TNF-alpha) markedly suppressed the elastin mRNA levels in a time- and dose-dependent manner by up to 91%. TNF-alpha also suppressed the expression of the elastin promoter/CAT construct by up to 70% in transiently transfected cells, indicating regulation at the transcriptional level. This suppression was temporally preceded by rapid and transient up-regulation of c-jun and c-fos genes. The down-regulatory effect of TNF-alpha on elastin promoter activity was abolished by co-transfections with a synthetic double-stranded AP-1 oligomer. Furthermore, co-transfection of the elastin promoter construct with c-jun and c-fos expression plasmids resulted in a marked decrease in the promoter activity. Elucidation of the cis-regulatory elements in the elastin promoter by 5' deletion construct analysis implicated a region -290 to -198 containing one AP-1 binding site. The functional role of this AP-1 site was further tested by gel retardation assays which indicated formation of a DNA-protein complex specific for TNF-alpha treated cells. This complex could be partially dissociated by a competing oligomer containing the consensus AP-1 binding site. These observations suggest that the inhibitory effects of TNF-alpha on elastin gene expression involve the transcription factor AP-1. Interferon-gamma also suppressed the elastin gene expression at the mRNA level by approximately 52%, but it had no effect on the elastin promoter activity, suggesting post-transcriptional mechanisms. These results indicate that mediators released from inflammatory cells can modulate elastin gene expression, and such modulation may play a role in diseases characterized by altered accumulation of elastic fibers in tissues.
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PMID:Tumor necrosis factor-alpha down-regulates human elastin gene expression. Evidence for the role of AP-1 in the suppression of promoter activity. 128 83

Previous studies have shown that 1-beta-D-arabinofuranosylcytosine (ara-C) induces transcription of the c-jun immediate early response gene in human myeloid leukemia cells. The present work has examined the mechanisms responsible for this effect. Deleted forms of the c-jun promoter were linked to the chloramphenicol acetyltransferase (CAT) gene and transfected into KG-1 cells. The results demonstrate that ara-C-induced c-jun transcription is mediated by an element between positions -74 and -20 upstream to the start site. Electrophoretic mobility shift assays with the fragment f(-74/-20) showed an increase in binding with nuclear proteins from ara-C-treated cells as compared with untreated cells. Competition with an oligonucleotide containing the AP-1 consensus sequence indicated that ara-C stimulates binding of nuclear proteins at the AP-1 site in the c-jun promoter. These findings were confirmed in other gel shift studies with the collagenase enhancer AP-1 consensus sequence and with a DNA fragment containing an altered AP-1 site. The binding of JUN/AP-1 was maximal at 1 hour of ara-C treatment and decreased to baseline levels at 12 hours. The finding that ara-C induces AP-1 binding in the absence of protein synthesis indicated that this agent activates already synthesized JUN/AP-1. To confirm these findings, the AP-1 consensus sequence was introduced 5' to the heterologous SV40 promoter. The results show that AP-1 enhances SV40 promoter activity in ara-C-treated cells. Taken together, these findings indicate that: (1) enhancement of JUN/AP-1 activity in ara-C-treated cells involves a posttranslational modification of JUN/AP-1; and (2) binding of activated JUN/AP-1 to the AP-1 site in the c-jun promoter confers ara-C inducibility of this gene.
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PMID:Activation of the AP-1 transcription factor by arabinofuranosylcytosine in myeloid leukemia cells. 1101 49

To extend our analysis of the regulation of human cytomegalovirus (HCMV) early gene expression, we examined a transcription unit located in the terminal repeats of the long segment of the viral genome. This region encodes a major 1.2-kb RNA which is induced at early times in infection but undergoes its largest increase in abundance after the onset of viral DNA replication. To identify the important cis-acting regulatory elements for this gene, two constructs were prepared for use in transient expression assays. One contained 413 bp of the upstream sequence and 43 bp of the leader sequence fused to the gene for chloramphenicol acetyltransferase (CAT). The second construct included 1,722 bp upstream of the start site of the 1.2-kb RNA, the entire transcribed region with an additional 166-bp insert derived from the CAT gene as an assayable marker, and 2,393 bp downstream of the polyadenylation signal. Both constructs were individually transfected into human fibroblast cells, and the cells were infected with HCMV. RNA specified by the hybrid construct was initiated at the correct position and accumulated with the same kinetics as the authentic viral transcript at early times in the infection but did not undergo the increase in abundance at late at late times. By 5'-end-deletion analysis, we determined that the promoter for the 1.2-kb RNA contains a number of cis-acting elements, the most significant of which are the TATA-like sequence CATAAA at -30 and a sequence corresponding to the binding site for the transcription factor AP-1 at -75. Using extracts prepared from HeLa cells as well as from infected and uninfected fibroblasts in gel retardation assays, we obtained evidence for the specific interaction of a cellular factor(s) with the AP-1 binding site. The pattern of binding differed in the HeLa and fibroblast cells but did not change as a function of the HCMV infection. However, the functional importance of the AP-1 binding site and its key role in the regulation of the 1.2-kb RNA was supported by analysis of constructs containing specific point mutations at this site in gel retardation and transient expression assays. Site-specific mutations in the AP-1 consensus sequence, which resulted in the complete loss of binding to cellular factors, eliminated the basal activity and reduced the inducible promoter activity by eightfold.
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PMID:An AP-1 binding site is the predominant cis-acting regulatory element in the 1.2-kilobase early RNA promoter of human cytomegalovirus. 131 36

Visna virus is a pathogenic lentivirus of sheep that is distantly related to the primate lentiviruses, including the human immunodeficiency virus type 1 (HIV-1). Replication of HIV-1 in cell culture requires the expression of a virus-encoded protein, Tat, which is a potent trans-activator of viral gene expression. Visna virus encodes an analogous Tat protein that greatly increases gene expression directed by the visna viral LTR. This report uses a stable vero cell line that constitutively expresses visna virus Tat to investigate the molecular mechanism of action of Tat on viral gene expression. Transient expression assays, using the visna virus LTR to drive transcription of the bacterial gene for chloramphenicol acetyltransferase (CAT), demonstrate that Tat trans-activates gene expression by increasing steady-state mRNA levels. The increase in steady-state mRNA levels is sufficient to account for the increase in protein observed and is due, in part, to an increase in the rate of transcription initiation. Tat mediates the accumulation of mRNA through AP-4 and AP-1 binding sites located in the U3 region of the LTR. Deletion of the upstream AP-1 and AP-4 binding sites results in a residual low level of trans-activation by Tat. Further experiments, using LTRs with R-U5 sequences deleted to +10, demonstrate AP-1 and AP-4 mediated responses to TAT at the RNA level, but no increase was observed in CAT protein.
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PMID:Molecular mechanisms of visna virus Tat: identification of the targets for transcriptional activation and evidence for a post-transcriptional effect. 131 69

Expression from the promoter of the herpes simplex virus type 2 (HSV-2) large subunit of ribonucleotide reductase (ICP10) is stimulated by co-transfection with DNA that encodes the virion protein Vmw65 previously shown to activate in trans the transcription of all IE genes (Wymer et al., 1989). Specific cis response elements involved in ICP10 transcriptional regulation were studied by chloramphenicol acetyltransferase analysis with hybrid ICP10 promoter/CAT structural gene constructions containing wild type or site-directed mutations of the promoter sequences. The data indicate that Vmw65 activation requires an intact TAAT-GARAT motif while complex formation requires an intact Oct-1 element, and the AP-1 consensus elements in the ICP10 promoter are functional in vitro. Thus, expression from the wild type and GA-rich mutant constructions was enhanced 10-20-fold by co-transfection with DNA encoding Vmw65. The GARAT and POU homeobox (PHB) binding motifs were required for Vmw65 mediated activation but the mutant in the POU specific box (PSB) binding motif was activated at higher concentrations of Vmw65 DNA (1.0-3.0 micrograms). The PHB and PSB binding motifs were necessary for complex formation as determined by gel retardation analysis with in vitro synthesized OTF-1 and Vmw65 proteins. The GARAT and GA-rich elements were not required. CAT expression from pICP10-cat was enhanced by co-transfection with jun and fos encoding DNA, and the ICP10 promoter complexed with in vitro synthesized jun protein.
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PMID:Immediate early and functional AP-1 cis-response elements are involved in the transcriptional regulation of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10). 132 Jul 96

Interleukin 8 (IL-8) is a novel cytokine which possesses neutrophil chemotactic and activating activities in addition to chemotactic activity for basophils and T lymphocytes. It has been shown that IL-8 is produced by a variety of human somatic cells including monocytes/macrophages, dermal fibroblasts, vascular endothelial cells, keratinocytes, mesangeal cells, and several types of tumor cell lines. We have examined here whether or not human gastric cancer cell lines produce IL-8 in vitro. The production of IL-8 protein was detected by enzyme-linked immunosorbent assay in the culture supernatants derived from eight of nine human gastric cancer cell lines stimulated with either interleukin 1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF alpha), or TNF alpha plus interferon gamma (IFN gamma). In some of the gastric cancer cell lines such as MKN 45 and KATO, TNF alpha plus IFN gamma synergistically induced the production of IL-8. In MKN 45 cells, synergistic increase of the steady state level of IL-8 mRNA by TNF alpha plus IFN gamma was not inhibited by cycloheximide treatment. Scatchard analysis revealed that IFN gamma changed neither the number nor the affinity constant of TNF alpha binding sites on a gastric cancer cell line, suggesting that the synergism was a post-receptor event. Furthermore, synergistic induction of chloramphenicol acetyltransferase activity by TNF alpha plus IFN gamma was observed in MKN 45 that were transiently transfected with chimeric chloramphenicol acetyltransferase reporter genes driven by the transcriptional regulatory region of human IL-8 gene. Through the mutation of the regulatory region of the IL-8 gene, both AP-1- and NF-kB-like factor binding elements were presumed to be involved in conferring the responsiveness to TNF alpha plus IFN gamma. Moreover, gel retardation analyses revealed that TNF alpha and IFN gamma synergistically induced the binding of NF-kB like as well as AP-1 like proteins bound to these sites. These results indicated that IFN gamma synergistically enhanced TNF alpha-induced IL-8 production in a human gastric cancer cell line through synergistic activation of transcription factors without up-regulating TNF alpha receptor.
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PMID:Tumor necrosis factor alpha and interferon gamma synergistically induce interleukin 8 production in a human gastric cancer cell line through acting concurrently on AP-1 and NF-kB-like binding sites of the interleukin 8 gene. 133 Oct 59

Several endocrine hormones which influence liver metabolism are known to increase in activity during the acute phase of injury or inflammation. We determined whether these hormones have the potential to influence acute-phase protein production in human and rat hepatoma cells. Catecholamines, glucagon, growth hormone, triiodothyronine, and cyclic nucleotides individually or in combination did not modulate the basal or the interleukin-1 (IL-1)-, IL-6-, and dexamethasone-stimulated levels of acute-phase plasma proteins. Insulin, however, was found to be a rapid, nonspecific, and dose-dependent inhibitor of the cytokine and glucocorticoid stimulation of acute-phase protein gene expression and to exert its effect at the transcriptional level. The insulin inhibition applied to all cytokines tested but to various degrees, depending upon the particular acute-phase gene. Insulin resulted in an early and prominent increase in the transcription of genes encoding the AP-1 components of JunA, JunB, and c-Fos, as has been observed for other growth factors. However, the effect of insulin on C/EBP beta was unexpected and paradoxical: while insulin completely inhibited the transcriptional activation of the C/EBP beta gene in cytokine- and dexamethasone-treated cells, the level of cytoplasmic C/EBP beta RNA was elevated. Quantitation of C/EBP beta mRNA by Northern (RNA) blot analysis and of C/EBP beta DNA binding activity by Southwestern (DNA-protein) blot analysis showed that insulin, when combined with cytokines and dexamethasone, stimulated both the mRNA and DNA binding activity by a factor of 1.6 compared with that of cells treated with cytokines and dexamethasone alone. Transient transfection of H-35 and HepG2 cells with a chloramphenicol acetyltransferase (CAT) gene expression vector containing the C/EBP beta response element also resulted in a 1.5-fold increase of C/EBP beta-mediated transcription in insulin-treated cells. Transfection of CAT gene constructs containing increasing lengths of heptaglobin gene 5' flanking sequences indicated that insulin inhibition of IL-6 stimulation required the presence of the region from -4100 to -1030. These results suggest that insulin has the potential to control the transcription of acute-phase genes by at least two separate mechanisms.
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PMID:Insulin is a prominent modulator of the cytokine-stimulated expression of acute-phase plasma protein genes. 137 89

Cytotactin is a morphoregulatory molecule of the extracellular matrix affecting cell shape, division, and migration that appears in a characteristic and complex site-restricted pattern during embryogenesis. The promoter region of the gene that encodes chicken cytotactin contains a variety of potential regulatory sequences. These include putative binding sites for homeodomain proteins and a phorbol 12-O-tetradecanoate 13-acetate response element (TRE)/AP-1 element, a potential target for transcription factors thought to be involved in growth-factor signal transduction. To determine the effects of homeobox-containing genes on cytotactin promoter activity, we conducted a series of cotransfection experiments on NIH 3T3 cells using cytotactin promoter-chloramphenicol acetyltransferase (CAT) reporter gene constructs and plasmids driving the expression of mouse homeobox genes Evx-1 and Hox-1.3. cotransfection with Evx-1 stimulated cytotactin promoter activity whereas cotransfection in control experiments with Hox-1.3 had no effect. To localize the sequences required for Evx-1 activation, we tested a series of deletions in the cytotactin promoter. An 89-base-pair region containing a consensus TRE/AP-1 element was found to be required for activation. An oligonucleotide segment containing this TRE/AP-1 site was found to confer Evx-1 inducibility on a simian virus 40 minimal promoter; mutation of the TRE/AP-1 site abolished this activity. To explore the potential role of growth factors in cytotactin promoter activation, chicken embryo fibroblasts, which are known to synthesize cytotactin, were first transfected with cytotactin promoter constructs and cultured under minimal conditions in 1% fetal bovine serum. Although the cells exhibited only low levels of CAT activity under these conditions, cells exposed for 12 h to 10% (vol/vol) fetal bovine serum showed a marked increase in CAT activity. Cotransfection with Evx-1 and cytotactin promoter constructs of cells cultured in 1% fetal bovine serum was sufficient, however, to produce high levels of CAT activity. These findings are consistent with the hypothesis that Evx-1, a homeobox-containing gene, may activate the cytotactin promoter by a mechanism involving a growth-factor signal transduction pathway. More generally, the results support the hypothesis that the place-dependent expression of morphoregulatory molecules may depend upon local cues provided by homeobox genes and their encoded proteins.
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PMID:Activation of the cytotactin promoter by the homeobox-containing gene Evx-1. 137 34

Previous experiments have indicated that the crystallins of the squid lens (S-crystallins) are evolutionarily related to glutathione S-transferases (GST) (EC 2.5.1.18). Here we confirm by peptide sequencing that the crystallins of the lens of the squid Ommastrephes sloani pacificus comprise a family of GST-like proteins. Squid lens extracts showed 400 times less GST activity than those of liver using 1-chloro-2,4-dinitrobenzene as a substrate, suggesting that the abundant GST-like crystallins lack enzymatic activity. Four different cDNAs (pSL20-1, pSL18, pSL11, and pSL4) showed 20-25% similarity in homologous regions with mammalian GST polypeptides. pSL20-1, pSL18, and pSL4 each encode an S-crystallin with a unique internal peptide that is unrelated to mammalian GSTs or any other sequence in GenBank. The S-crystallin family is encoded in a minimum of 9-10 genes, and the exon-intron structures of at least two of these (SL20-1 and SL11) are similar to those of the mammalian GST genes. The SL20-1 gene has six exons, with the its unique internal peptide encoded precisely in exon 4; the SL11 gene lacks a unique internal peptide and has five exons. Experiments using bacterial chloramphenicol acetyltransferase as a reporter gene showed that at least 84 and 111 base pairs of 5'-flanking sequence are needed for function of the SL20-1 and SL11 promoters, respectively, in a transfected rabbit lens epithelial cell line (N/N1003A). Within these regions each has a putative TATA box and an upstream AP-1 site overlapping with antioxidant responsive-like elements, which are regulatory elements in the rat GST Ya and quinone reductase genes responsive to oxidative stress.
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PMID:Characterization of squid crystallin genes. Comparison with mammalian glutathione S-transferase genes. 137 30

A manifestation of Alzheimer's disease is the presence of amyloid depositions in brains of afflicted individuals. A major component of these depositions is the amyloid beta-protein, which is a truncated form of the larger amyloid beta-protein precursor (APP). To investigate the regulation of APP gene expression, the APP promoter and selected deletions were placed 5' to the reporter gene chloramphenicol acetyltransferase. The promoter deletions were transfected into different cell lines that showed variant levels of endogenous APP transcripts. Transient transfection assays showed that 96 base pairs 5' to the transcriptional start site are sufficient for cell type-specific promoter activity. A nuclear factor that binds to this region in a sequence-specific manner was identified by mobility shift electrophoresis, DNase footprinting, and methylation interference. The DNase-protected region covers about 25 base pairs on both strands (position -31 to -55). Mutations within this domain revealed a sequence of 12 base pairs that is crucial for factor binding. This sequence overlaps with the consensus sequences for transcription factors AP-1 and AP-4. However, competition experiments suggest that the nuclear factor that binds to the APP promoter is distinct from both AP-1 and AP-4. Factor binding to the characterized recognition sequence is observed in nuclear extracts originating from human, mouse, and rat cells, suggesting a high degree of conservation.
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PMID:The amyloid beta-protein precursor promoter. A region essential for transcriptional activity contains a nuclear factor binding domain. 138 Sep 60


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