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)

Infection with wild-type adenovirus 5, but not with a mutant lacking the E1A gene, prevented the induction by interferon (IFN) alpha of chloramphenicol acetyltransferase (CAT) activity in HeLaM cell lines that had been permanently transfected with chimeric CAT reporter genes driven by the transcriptional regulatory regions of the IFN-responsive genes 561 and 6-16. Similar inhibition of IFN-inducible CAT activity was observed in cells that were cotransfected with the same reporter genes and plasmids expressing either the E1A 289- or 243-amino acid protein. These proteins also prevented the induction of CAT activity by IFN-gamma from a cotransfected HLA-DR alpha-CAT gene. Experiments with E1A mutants mapped the inhibitory activity to amino acid residues 38-65 of these proteins. In a HeLa cell line permanently expressing the E1A 289-amino acid protein, the replication of vesicular stomatitis virus and encephalomyocarditis virus was not inhibited by IFN-alpha, suggesting a global blockade of IFN responses. In accord with this theory, induction of 561, 1-8, and (2'-5')oligoadenylate synthetase mRNAs by IFN was blocked in these cells at the transcriptional level. The observed transcriptional inhibition could be attributed to the lack of formation of the crucial IFN-stimulated gene factor 3 (ISGF3) transcriptional complex. As shown by mobility shift assays, this complex was not formed in the nuclear extracts of IFN-treated adenovirus-infected cells or IFN-treated E1A-producing cells. These nuclear extracts were deficient in both ISGF3 alpha and ISGF3 gamma subunits. However, they did not block the formation of ISGF3 complex from exogenously added components.
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PMID:Inhibition of interferon-inducible gene expression by adenovirus E1A proteins: block in transcriptional complex formation. 165 51

The antiviral/antiproliferative/antitumor properties of interferon (IFN) are potentiated by a febrile temperature (Heron, I., and Berg, K. (1978) Nature 274, 508-510; Fleischmann, W. R., Fleischmann, C. M., Jr., and Gindhart, T. D. (1986) Cancer Res. 46, 1722-1726; Groveman, D. S., Borden, E. C., Merritt, J. A., Robins, H. I., Steeves, R., and Bryan, G. T. (1984) Cancer Res. 44, 5517-5521). To investigate the role of 2',5'-oligoadenylate (2-5A) synthetase in linking temperature with these biological functions of IFN, antiviral activities and expression of the 2-5A synthetase gene were measured simultaneously in control and type I IFN-treated HL-60 and WISH cells at the selected elevated temperature of 39.5 degrees C +/- 0.5 degrees C (herein referred to as hyperthermia). In both cell lines, the IFN-mediated antiviral effect was enhanced 3-10-fold. Concurrently, enzymatic assays and immunoblot analyses with an anti-40-kDa synthetase antibody clearly gave a 2-3-fold increase of synthetase above that observed at the normal cell culture temperature (37 degrees C). These results suggest that potentiation of 2-5A synthetase must partially account for the enhanced antiviral activity of IFN at the higher cell culture temperature. The supranormal elevation of 2-5A synthetase was accompanied by a parallel increase in the steady-state concentration of 2-5A synthetase mRNA, which is likely to contribute to the observed increase in enzyme level. Transient reporter gene expression studies using plasmid constructs carrying 2-5A synthetase gene promoter linked in tandem with chloramphenicol acetyltransferase showed that IFN-inducible chloramphenicol acetyltransferase activity was not influenced by hyperthermia, suggesting that transcription activation is an unlikely explanation for the observed 2-5A synthetase mRNA level increases. Messenger RNA stability assays showed that the half-life (t1/2) of 2-5A synthetase mRNA was extended from 2 to 4 h at 39.5 degrees C. Under identical conditions, the t1/2 of poly(A)+ RNA remained unchanged whereas the t1/2 of beta-actin mRNA was reduced. Taken together, these results are consistent with the interpretation that selective stabilization of 2-5A synthetase mRNA at the elevated temperature is a major factor contributing to the potentiation of antiviral activity of IFN by hyperthermia.
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PMID:Modulation of antiviral activity of interferon and 2',5'-oligoadenylate synthetase gene expression by mild hyperthermia (39.5 degrees C) in cultured human cells. 170 57

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

We have reported that interferon-alpha inhibits HPV-18 mRNA in HeLa cells. Here we examine mechanisms by which IFN could modulate HPV expression. In northern blot experiments, we observed that interferon-alpha 2b treatment reduced HPV-18 mRNA levels in a time- and dose-dependent manner, with a maximal effect achieved at 48 h. Simultaneously, induction of 2-5A synthetase mRNA was verified as indicative of IFN action. The IFN regulatory effect on HPV-18 mRNA at 48 h required de novo protein synthesis. We performed run-on experiments to determine whether the IFN regulatory effect was at the transcriptional level. HPV-18 endogenous transcription was repressed using 200 and 1000 IU/ml. Interferon treatment did not affect HPV-18 mRNA stability, at least under our experimental conditions. To verify whether HPV-18 enhancer sequences were involved in the interferon effect, we transfected a construct containing the chloramphenicol acetyltransferase driven by the HPV-18 upstream regulatory region. The enzyme activity was unmodified on human keratinocytes and HeLa cells by interferon exposition. Our data demonstrate that interferon-alpha downregulates HPV-18 mRNA levels on HeLa cells by repressing nascent viral transcripts, possibly through regulatory cellular flanking regions.
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PMID:Interferon-alpha elicits downregulation of human papillomavirus 18 mRNA in HeLa cells by selective repression of endogenous viral transcription. 755 18