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)

Transcription of the complete mouse mammary tumor virus (MMTV) proviral genome in mouse cells is controlled by a strong promoter in its long terminal repeat. In the mouse T lymphoma EL4, there is a second, activation-dependent transcriptional initiation site within the envelope (env) gene, from which a short mRNA is generated, encoding the open reading frame of the long terminal repeat. We now report the isolation of a segment of the MMTV env gene (called META, for MMTV env transcriptional activator) which has the expected transcription-activating properties seen in EL4.E1 cells. Namely, it induces activation-dependent, T-lymphocyte-specific transcription of a chloramphenicol acetyltransferase reporter gene. It is active in mouse or human T-helper lymphocyte lines when they are stimulated to transcribe lymphokine genes but is inactive in unstimulated T-helper cells, fibroblasts, a cytotoxic T-lymphocyte line, and a mastocytoma cell line. Its activity is inhibited by cyclosporin A, a specific inhibitor of lymphokine transcription. Several forms of the META have been isolated from EL4.E1 cells, a mouse T-helper cell hybridoma, and from BALB/c spleen cells. Linked to the heterologous thymidine kinase promoter, a 400-bp portion of it is an inducible, orientation-independent, and cyclosporin A-sensitive transcriptional activator in T-helper cells.
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PMID:An activation-dependent, T-lymphocyte-specific transcriptional activator in the mouse mammary tumor virus env gene. 132 Jan 98

Antigen triggering of the T-cell receptor results in an accumulation of activated GTP-bound p21ras protein. To assess the role of ras protein in T-cell activation we have cotransfected the murine thymoma line EL4 with a construct capable of expressing a constitutively active, oncogenic form of Ha-ras and a reporter construct containing the human interleukin-2 promoter fused upstream of the bacterial gene for chloramphenicol acetyltransferase. We show that the ras oncoprotein contributes to interleukin-2 promoter activation. Its pattern of synergism with a calcium ionophore or the lymphokine interleukin-1 indicates that it replaces a signal mediated by protein kinase C. Interleukin-2 promoter activity in the presence of ras oncoprotein was inhibited by H7, a potent inhibitor of protein kinase C, but not by HA1004, an inhibitor of cyclic nucleotide-dependent kinase, suggesting that protein kinase C mediates the ras effect. In addition, we show that in these cells, expression of activated ras results in activation of a synthetic promoter containing several copies of an NF kappa B binding site.
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PMID:Interleukin-2 promoter activation in T-cells expressing activated Ha-ras. 153 20

We have used an interleukin-2 (IL-2) promoter-CAT fusion gene to study activation of IL-2 gene expression by IL-1, phytohemagglutinin (PHA), phorbol myristate acetate (PMA), and calcium ionophore in the murine thymoma line EL4 and the human lymphoma line Jurkat. The two cell lines respond differently to combinations of these stimuli. IL-1 in combination with suboptimal concentration of PMA induced chloramphenicol acetyltransferase (CAT) activity in EL4. In Jurkat cells, IL-1 failed to synergize with PMA or PHA. Cotransfection with the IL-2/CAT gene and a construct capable of expressing murine T-cell type IL-1 receptors converted Jurkat cells to IL-1 responsiveness. IL-1 in combination with PHA but not with PMA resulted in induction of CAT activity in these cells. Induction of IL-2/CAT activity by all stimuli in both cell lines was blocked by the presence of EGTA in the culture medium. EGTA did not inhibit IL-1/PMA activation of an SV40 early promoter-CAT fusion gene in either EL4 or Jurkat cells; therefore, calcium was not required for IL-1 or PMA signal transduction. Jurkat cells were shown to differ from EL4 in their requirement for calcium mobilization. Two different calcium-dependent pathways of gene activation were distinguished, both of which were blocked by the immunosuppressive drug cyclosporin A.
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PMID:Cyclosporin A blocks calcium-dependent pathways of gene activation. 165 71

Interleukin-1 (IL-1) is known to synergize with phorbol esters in the induction of interleukin-2 (IL-2) expression in T-lymphoid leukemia cells and proliferation of mouse thymocytes. We used a plasmid construct containing the bacterial gene for chloramphenicol acetyltransferase under the control of the human IL-2 promoter to study the nature of this synergism in the murine thymoma cell line EL4. Although IL-1 induction of the IL-2 promoter in these cells required costimulus with phorbol myristate acetate, the signal induced by IL-1 was qualitatively different. We provide evidence to support the hypothesis that the phorbol ester signal is mediated by protein kinase C, and we show that the IL-1 signal is not. That IL-1 and phorbol myristate acetate represent different stimuli was shown by their response to protein kinase C inhibitors, capacity to synergize with increased intracellular free calcium, and requirement for protein synthesis. In addition we show that pretreatment with IL-1 can prime EL4 cells to subsequent activation by concentrations of phorbol esters not normally sufficient to induce IL-2 expression. Pretreated cells remained primed for at least 40 h after removal of the IL-1. Neither phorbol myristate acetate nor a calcium ionophore was capable of preactivating EL4 cells.
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PMID:A role for protein kinase C activity in interleukin-1 (IL-1) induction of IL-2 gene expression but not in IL-1 signal transduction. 169 59

We have examined the mechanisms by which interferon (IFN)-gamma and IFN-alpha regulate the expression of 2'-5'-oligoadenylate synthetase (2-5A synthetase) and class I major histocompatibility complex antigens in murine T cells and in cell types of other histological origin. When treated with IFN-alpha both fibroblasts and T cell lines displayed a marked increase of the 2-5A synthetase activity and of the corresponding mRNA. The augmentation of the enzyme activity in T cells was induced by IFN-alpha at the transcriptional level, as determined by nuclear run-on analysis. In contrast IFN-gamma was capable of increasing 2-5A synthetase activity only in fibroblasts, but not in T cells. Nuclear run-on assays revealed that the 2-5A synthetase gene in T cells is not transcriptionally activated by IFN-gamma. After IFN-alpha and -gamma treatment we also observed a significant increase in class I gene expression in fibroblasts and T cell lines as measured both on the cell surface and by cytoplasmic RNA accumulation. In the case of the T cell line, DO1110, the observed increase in the steady-state levels of class I transcripts was a consequence of a high rate of H-2 gene transcription as demonstrated by run-on analysis. However, the molecular mechanisms involved in this IFN-dependent H-2 gene transcriptional activation are different between IFN-alpha and IFN-gamma. When the T cell lines DO1110, L12-R4 and EL4 were transfected with a plasmid containing a reporter gene (chloramphenicol acetyltransferase) under the control of a regulatory IFN-responsive DNA element of 237 bp or 1.4 kb, IFN-alpha was able to activate the transcription of these constructs. In contrast, IFN-gamma did not recognize the IFN-responsive element which, by itself, activated transcription of the reporter gene in response to IFN-gamma in other cellular types of non-T cell origin. Therefore, in the T cell lines examined, IFN-gamma increases the H-2 gene expression by acting on DNA elements located upstream of the regulatory segment used in this study or downstream of the cap site. This suggests a possible cell specificity in the activation of an IFN-responsive element, that in turn may regulate the IFN-inducible gene expression in a cell-specific fashion. Thus, the differential biological activities of IFN-gamma on T cells could be generated by a differential gene activation at the transcriptional level.
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PMID:Cell and type specificity of interferon action. Unusual characteristics of the transcriptional control of gene expression by interferon-gamma in T cells. 211 96

Transcriptional regulation of the interleukin-5 (IL-5) gene in T lymphocytes appears to be of central importance in the control of the eosinophilia characteristic of allergic responses and certain parasite infections. Previous studies of IL-5 gene regulation have been hampered by the lack of a transfection assay, which detects the antigen-responsive enhancer in the IL-5 promoter. Here we show that stable transfection of the Th2 clone D10.G4.1 and the T lymphoma EL4.23 with chloramphenicol acetyltransferase reporter gene constructs carrying the region to -3859 gives inducible expression with the known regulatory characteristics of the endogenous IL-5 gene. To facilitate detailed analysis of the promoter region, 3.9 kb of DNA sequence immediately up stream of the start of transcription was determined and the minimum upstream region required for inducible expression was further localized, by stable transfection studies in EL4.23 cells, to the region up to -1016. A CTF/NF1 site in the upstream enhancer at -940 to -928 was shown to be required for regulated inducible expression. Mutation of this sequence motif abolished inducibility and also prevented binding of the sequence to a nuclear protein(s). A TCATTT-containing element in the proximal promoter region was also demonstrated to be essential for inducible expression of the IL-5 gene, similar to the role of this conserved element in the transcriptional regulation of the granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 genes.
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PMID:Localization of the inducible enhancer in the mouse interleukin-5 gene that is responsive to T-cell receptor stimulation. 771 77

Recombinant human interleukin-1 (IL-1) alpha and beta were found to activate a latent cytosolic form of the transcription factor NF kappa B in rat C6 glioma. IL-1 beta was 10 times more potent than IL-1 alpha for this activity and both were inhibited by the IL-1 receptor antagonist. The activation was detectable from 20 min and remained sustained for up to 24 h. The electrophoretic mobility of the activated complex was shown to be different from that of the corresponding complexes in another IL-1-responsive cell line, the murine thymoma line EL4.NOB-1. C6 cells, when transiently transfected with five NF kappa B consensus sequence repeats linked to the reporter gene chloramphenicol acetyltransferase (CAT), demonstrated increased CAT activity in response to IL-1 beta treatment. The activation of NF kappa B in glial cells may thus represent an early step in IL-1 signalling in brain and is likely to have consequences for IL-1-induced gene expression in these cells.
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PMID:Interleukin-1 activates transcription factor NF kappa B in glial cells. 837 49

Activation of the murine c-myc promoter by murine c-Myb protein was examined in several cell lines by using a transient expression system in which Myb expression vectors activate the c-myc promoter linked to a chloramphenicol acetyltransferase reporter gene or a genomic beta-globin gene. S1 nuclease protection analyses confirmed that the induction of c-myc by c-Myb was transcriptional and affected both P1 and P2 start sites in a murine T-cell line, EL4, and a myelomonocytic line, WEHI-3. Mutational analyses of the c-myc promoter revealed that two distinct regions could confer Myb responsiveness in two T-cell lines, a distal site upstream of P1 and a proximal site within the first noncoding exon. In contrast, only the proximal site was required for other cell lineages examined. Five separate Myb-binding sites were located in this proximal site and found to be important for c-Myb trans activation. DNA binding was necessary for c-myc activation, as shown by the loss of function associated with mutation of Myb's DNA-binding domain and by trans-dominant repressor activity of the DNA binding, trans-activation-defective mutant. The involvement of additional protein factors was addressed by inhibiting protein synthesis with cycloheximide in a conditional expression system in which the activity of presynthesized Myb was under the control of estrogen. These experiments indicate that de novo synthesis of additional proteins was not necessary for c-myc trans activation. Together these data reveal two cell lineage-dependent pathways by which c-Myb regulates c-myc; however, both pathways are mechanistically indistinguishable in that direct DNA binding by Myb is required for activating c-myc whereas neither de novo protein synthesis nor other labile proteins are necessary.
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PMID:Mechanism of c-myc regulation by c-Myb in different cell lineages. 847 46

T-lymphocyte stimulation requires activation of several protein kinases, including the major phorbol ester receptor protein kinase C (PKC), ultimately leading to induction of lymphokines, such as interleukin-2 (IL-2). The revelant PKC isoforms which are involved in the activation cascades of nuclear transcription factors involved in IL-2 production have not yet been clearly defined. We have examined the potential role of two representative PKC isoforms in the induction of the IL-2 gene, i.e., PKC-alpha and PKC-theta, the latter being expressed predominantly in hematopoietic cell lines, particularly T cells. Similar to that of PKC-alpha, PKC-theta overexpression in murine EL4 thymoma cells caused a significant increase in phorbol 12-myristate 13-acetate (PMA)-induced transcriptional activation of full-length IL-2-chloramphenicol acetyltransferase (CAT) and NF-AT-CAT but not of NF-IL2A-CAT or NF-kappaB promoter-CAT reporter gene constructs. Importantly, the critical AP-1 enhancer element was differentially modulated by these two distinct PKC isoenzymes, since only PKC-theta but not PKC-alpha overexpression resulted in an approximately 2.8-fold increase in AP-1-collagenase promoter CAT expression in comparison with the vector control. Deletion of the AP-1 enhancer site in the collagenase promoter rendered it unresponsive to PKC-theta. Expression of a constitutively active mutant PKC-theta A148E (but not PKC-alpha A25E) was sufficient to induce activation of AP-1 transcription factor complex in the absence of PMA stimulation. Conversely, a catalytically inactive PKC-theta K409R (but not PKC-alpha K368R) mutant abrogated endogenous PMA-mediated activation of AP-1 transcriptional complex. Dominant negative mutant Ha-RasS17N completely inhibited the PKC-O A148E-induced signal, PKC-O. Expression of a constitutively active mutant PKC-O A148E (but not PKC-alpha A25E) was sufficient to induce activation of AP-1 transcription factor complex in the absence of PMA stimulation. Conversely, a catalytically inactive PKC-O K409R (but not PKC-alpha K368R) mutant abrogated endogenous PMA-mediated activation of AP-1 transcriptional complex. Dominant negative mutant Ha-enRasS17N completely inhibited in the PKC-O A148E-induced signal, identifying PKC-theta as a specific constituent upstream of or parallel to Ras in the signaling cascade leading to AP transcriptional activation.
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PMID:Protein kinase C-theta isoenzyme selective stimulation of the transcription factor complex AP-1 in T lymphocytes. 865 60

Transforming growth factor beta1 (TGF-beta1) has been previously shown to modulate interleukin 2 (IL-2) secretion by activated T-cells. In the present studies, we determined that TGF-beta1 induced IL-2 mRNA expression in the murine T-cell line EL4, in the absence of other stimuli. IL-2 mRNA expression was significantly induced by TGF-beta1 (0.1-1 ng/ml) over a relatively narrow concentration range, which led to the induction of IL-2 secretion. Under identical condition, we examined the effect of TGF-beta1 on the activity of nuclear factor AT (NF-AT), nuclear factor kappaB (NF-kappaB), activator protein-1 (AP-1) and octamer, all of which contribute to the regulation of IL-2 gene expression. Electrophoretic mobility shift assays showed that TGF-beta1 markedly increased NF-AT, NF-kappaB and AP-1 binding to their respective cognate DNA binding sites, whereas octamer binding remained constant, as compared with untreated cells. Employing a reporter gene expression system with p(NF-kappaB)3-CAT, p(NF-AT)3-CAT and p(AP-1)3-CAT, TGF-beta1 treatment of transfected EL4 cells induced a dose-related increase in chloramphenicol acetyltransferase activity that correlated well with the DNA binding profile found in the electrophoretic mobility shift assay studies. These results show that TGF-beta1, in the absence of any additional stimuli, up-regulates the activity of key transcription factors involved in IL-2 gene expression, including NF-AT, NF-kappaB and AP-1, to help promote IL-2 mRNA expression by EL4 cells.
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PMID:Transforming growth factor-beta 1 (TGF-beta1) promotes IL-2 mRNA expression through the up-regulation of NF-kappaB, AP-1 and NF-AT in EL4 cells. 986 99


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