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)

The nature of the interaction between human immunodeficiency virus (HIV) and human cells of astrocytic origin was studied in vitro with cultured glial cells and intact HIV or infectious molecular clones of the virus. Infection of glial cells with intact HIV was characterized by low-level expression of viral transcripts as detected by Northern blotting and in situ hybridization (less than 10 copies of HIV RNA per cell), transient virus replication, absence of viral antigens detectable by immunofluorescence, and complete lack of cytopathic effects. However, the HIV-infected glial cells persistently expressed HIV tatIII gene activity as detected by a chloramphenicol acetyltransferase assay, and HIV transcripts could be detected by in situ hybridization in 20 to 30% of cells up to 4 months after infection, suggesting that the lack of cytopathicity in HIV-exposed cells was not due to transient viral infection. To evaluate whether increased expression and replication of HIV in glial cells would have any effect on cell growth and viability, we established HIV-positive glial cell lines by cotransfection of cells with infectious molecular clones of HIV DNA and a selectable marker gene. Three clones were isolated which produced high levels of viral particles, were strongly positive for HIV antigens by immunofluorescence, and contained greater than 1,000 copies of HIV RNA per cell. These cell lines showed no cytopathic changes (lysis, fusion), and their growth kinetics were similar to HIV- controls, but significant morphological changes were detected (cytoplasmic swelling; increased numbers of rounded, presumably detaching cells). Our results show that astrocytic cells can support a persistent, replicative HIV infection with limited pathogenic effects.
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PMID:Persistent productive infection of human glial cells by human immunodeficiency virus (HIV) and by infectious molecular clones of HIV. 244 7

The role of the hepatitis B virus (HBV) X gene during virus infection has not been defined. We previously showed that expression of the HBV X gene in the human hepatocellular carcinoma cell line HepG2 trans-activates chloramphenicol acetyltransferase gene expression under control of the human immunodeficiency virus 1 (HIV-1) long terminal repeat and we have now identified a specific sequence in the HIV-1 long terminal repeat that is responsive to the HBV X gene. Plasmid constructs with the chloramphenicol acetyltransferase gene regulated by an isolated and twice-repeated 12-base-pair HIV-1 enhancer sequence homologous to the nucleotide sequence that binds the nuclear transcription factor NF-kappa B (the HIV-1 kappa B-like sequence) were trans-activated by the HBV X gene in HepG2 cells, indicating that the kappa B-like enhancer sequence in the HIV-1 long terminal repeat is responsive to the X gene. When eight copies of the HIV-1 kappa B-like sequence were used to regulate beta-globin gene expression, transcription of this gene was activated by the HBV X gene in HepG2 cells and no beta-globin gene transcription was detected in the absence of the HBV X gene. beta-globin gene expression regulated by the activator protein 2 (AP-2) binding sequence was not activated by the HBV X gene. Treatment of HepG2 cells with phorbol ester resulted in modest activation of the HIV-1 kappa B-like enhancer sequence suggesting that an NF-kappa B-like factor was induced in these cells as it is in T lymphocytes by phorbol ester; however, phorbol ester did not demonstrably enhance the activation of the HIV-1 enhancer observed with the HBV X gene. These experiments indicate that the HIV-1 kappa B-like transcriptional enhancer sequence is activated by the HBV X gene and suggest that the HBV X gene might play a role in regulating transcription of a gene under control of a kappa B-like enhancer during HBV infection. Since such a sequence has not been found in the HBV genome and HBV gene expression appears not to be regulated by the HBV X gene, a cellular gene that plays a role in HBV replication could be the target of the X gene during HBV infection.
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PMID:Hepatitis B virus X gene activates kappa B-like enhancer sequences in the long terminal repeat of human immunodeficiency virus 1. 274 Mar 49

cDNAs for genome RNAs of influenza virus A/PR/8/34 were cloned, and portions containing the ATG for initiation codon of translation were inserted into the 5' leader sequence of the chloramphenicol acetyltransferase (CAT) gene in a pSV2cat vector. When transfected cells were super-infected with influenza virus, the CAT activity was found to vary in a time-dependent fashion: A construct containing a cDNA segment for the nonstructural (NS) protein directed the highest activity during the early stage of infection, while a construct containing a cDNA segment for the neuraminidase (NA) directed the highest activity during the late stage of infection. This time-dependent variation in the CAT activity is in good agreement with that of the synthesis rate of respective viral proteins in infected cells. We propose that the translational efficiency of viral mRNA is subjected to temporal control following viral infection, although viral protein synthesis itself is regulated primarily at the level of mRNA synthesis.
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PMID:Translational regulation of influenza virus mRNAs. 285 14

We examined E1A gene expression by two evolutionarily divergent human adenoviruses, type 5 (subgroup C) and type 3 (subgroup B). Adenovirus type 3 (Ad3)-infected A549 cells contained much larger amounts of E1A-specific RNA than adenovirus type 5 (Ad5)-infected cells, from very early (3 h) through the late stages (20 h) after infection. The appearance of such abundant Ad3 E1A transcripts was delayed after infection of Ad5 E1A-expressing 293 cells, suggesting a down regulation of the Ad3 E1A gene by Ad5 E1A gene products. In a reciprocal manner, coinfection of A549 cells led to typically early and intense Ad3 E1A transcription and strongly inhibited transcription of the Ad5 E1A gene. Transient expression assays were developed so that the autoregulation of the E1A gene could be studied apart from the more complex background of infected cells. The DNA sequence surrounding the transcription start site of the Ad3 E1A gene was placed 5' to the sequence which encodes the bacterial chloramphenicol acetyltransferase gene. Cotransfection of HeLa cells with Ad3 or Ad5 E1A-expression plasmids increased the expression of the Ad3 E1A promoter-driven chloramphenicol acetyltransferase gene. Taken together, these results suggest dual autoregulatory features of adenovirus E1A gene expression. The positive and negative effects appear to be temporally distinguished under different conditions, both in viral infection and in transient assays with plasmid-cloned genes.
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PMID:Autoregulation of adenovirus E1A gene expression. 293 96

The requirements for expression of genes under the control of early (alkaline exonuclease) and late (VP5) herpes simplex virus type 1 (HSV-1) gene promoters were examined in a transient expression assay, using the bacterial chloramphenicol acetyltransferase gene as an expression marker. Both promoters were induced, resulting in the production of high levels of the enzyme upon low-multiplicity infection by HSV-1. S1 nuclease analysis of hybrids between RNA isolated from infected cells containing HSV-1 promoter constructs and marker gene DNA demonstrated normal transcriptional initiation of the marker gene directed by the viral promoters. Viral DNA sequences no more than 125 bases 5' of the putative transcriptional cap site were sufficient for maximum activity of the late promoter. In contrast to expression controlled by the early gene, the late promoter was not active at a measurable level in uninfected cells until DNA sequences between 75 and 125 bases 5' of the transcriptional cap site were deleted. Cotransfection of cells with the expression marker controlled by HSV promoters and a cosmid containing HSV alpha (immediate-early) genes indicated that full expression of both early and late promoters requires the same virus-induced host cell modifications. Inhibition of viral DNA synthesis results in an increased rate of transient expression of marker genes under control of either early or late promoters in contrast to the situation in normal virus infection. These data provide evidence that the normal course of expression of late HSV genes involves negative modulation of potentially active promoters in the infected cell.
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PMID:Virus-induced modification of the host cell is required for expression of the bacterial chloramphenicol acetyltransferase gene controlled by a late herpes simplex virus promoter (VP5). 299 49

A detailed analysis of the expression of the bacterial chloramphenicol acetyltransferase gene controlled by the herpes simplex virus major capsid protein (VP5) promoter showed that this promoter can be functionally separated into an 80-base core region, which has the minimal information required to serve as a pol II promoter but which is not fully activated by viral superinfection or by cotransfections with plasmids bearing functional alpha (immediate-early) genes, and an approximately 100-base regulatory region upstream of the core, which allowed full induction of VP5 promoter-driven chloramphenicol acetyltransferase activity but which repressed the ability of the VP5 core promoter to be cis activated by the simian virus 40 enhancer. This was in distinct contrast to the situation with the alkaline exonuclease promoter (a model early promoter) and defined the regions of this promoter which can be used to study the interaction between viral promoters and putative regulatory proteins induced by viral infection.
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PMID:A single regulatory region modulates both cis activation and trans activation of the herpes simplex virus VP5 promoter in transient-expression assays in vivo. 302 80

In mouse cells induced with virus infection or dsRNA, the relative levels of alpha-4 interferon mRNA were higher than the levels of alpha-1 and alpha-6 mRNAs; the ratio between relative levels of alpha-4 and alpha-1 or alpha-6 mRNA was, however, dependent on the cell type. Recombinant plasmids, in which the expression of chloramphenicol acetyltransferase (CAT) gene was directed by the promoter regions of alpha-1, alpha-4 or alpha-6 interferon genes were constructed and their inducible expression was studied either in transient assay or in permanently transfected mouse cells. The highest levels of CAT activity and CAT mRNA were observed with alpha-4 CAT plasmid, while the expression of alpha-1 CAT was consistently higher than that coded by alpha-6 CAT plasmid; the ratio between CAT activities coded by alpha-4 CAT and alpha-1 CAT was dependent on cell type. However, in heterologous Vero cells, the transfected alpha-1 and alpha-4 genes were expressed constitutively, and the levels of mRNAs were comparable. These results show that the difference in the relative levels of individual alpha-1 and alpha-4 mRNAs reflects the transcriptional inducibility of the respective promoter regions.
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PMID:Differential and cell type specific expression of murine alpha-interferon genes is regulated on the transcriptional level. 339 85

A transient expression system in which chimeric genes are expressed in cells infected with vaccinia virus was developed. Recombinant plasmids containing the promoter regions of vaccinia virus genes ligated to the coding segment of the prokaryotic chloramphenicol acetyltransferase (CAT) gene were constructed. When the plasmids were introduced into vaccinia virus-infected cells by transfection, the chimeric gene was expressed and significant levels of CAT accumulated. CAT activity was not detected when the same recombinant plasmid was introduced into uninfected cells, nor was activity detected when the vaccinia virus promoter was absent from the plasmid or was replaced by simian virus 40 or Rous sarcoma virus promoters. This specificity indicated that expression is dependent on a cis-acting vaccinia virus promoter region within the recombinant plasmid and diffusible trans-acting transcription factors produced during virus infection. The lack of effect of a simian virus 40 enhancer element inserted upstream of the vaccinia virus promoter region also distinguished this system from systems dependent on RNA polymerase II. Although replication of the recombinant plasmid could not be detected in either uninfected or vaccinia virus-infected cells, an inhibitor of DNA synthesis significantly reduced CAT expression. This result, as well as the kinetics of CAT synthesis, suggests that replication of viral DNA templates can enhance transcription of chimeric genes in recombinant plasmids.
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PMID:Eukaryotic transient expression system dependent on transcription factors and regulatory DNA sequences of vaccinia virus. 385 41

The promoter-regulatory regions from the herpes simplex virus type 1 (HSV-1) gene for the immediate-early, 175,000-molecular-weight (175K) protein and the HSV-2 delayed-early gene for a 38K protein were linked to the readily assayable bacterial gene for the enzyme chloramphenicol acetyltransferase (CAT). Unexpectedly, in measurements of the constitutive expression of the recombinant genes 40 to 50 h after transfection of Vero cells, enzyme levels expressed from the delayed-early 38K-promoter-CAT construct (p38KCAT) were at least as high as those from the immediate-early 175K-promoter-CAT construct (p175KCAT). In contrast, enzyme levels expressed after transfection of a similar recombinant gene containing a second delayed-early promoter region, that of the HSV-1 thymidine kinase gene, were ca. 20-fold lower. The amounts of enzyme expressed from both p38KCAT and p175KCAT could be increased by up to 20- to 40-fold after infection of the transfected cells with HSV. In comparison, virus infection had no significant effect on enzyme levels expressed from recombinant CAT genes containing the simian virus 40 early promoter region, with or without the 72-base-pair enhancer element. Experiments with the temperature-sensitive mutants HSV-1 tsB7 and HSV-1 tsK indicate that induction of expression from p175KCAT was mediated by components of the infecting virus particle, whereas that from p38KCAT required de novo expression of virus immediate-early proteins. In addition, we show that functions required to induce expression from both p175KCAT and p38KCAT could also be provided by infection with pseudorabies virus and cytomegalovirus.
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PMID:Expression of recombinant genes containing herpes simplex virus delayed-early and immediate-early regulatory regions and trans activation by herpesvirus infection. 609 73

Multiple regulatory domains within the -100 region of the beta interferon (IFN-beta) promoter control the inducible response of the IFN gene to virus infection. In this study, we demonstrate that the formation of NF-kappa B-specific complexes on the positive regulatory domain II (PRDII) precedes the onset of detectable IFN-beta transcription in Sendai virus-infected cells. By using NF-kappa B subunit-specific antibodies, a temporal shift in the composition of NF-kappa B subunits in association with the PRDII domain is detected as a function of time after virus infection. Furthermore, a virus-induced degradation of I kappa B alpha (MAD3) protein is observed between 2 and 8 h after infection; at later times, de novo synthesis of I kappa B alpha restores I kappa B alpha to levels found in uninduced cells and correlates with the down regulation of IFN-beta transcription. In cotransfection experiments using various NF-kappa B subunit expression plasmids and two copies of PRDII/NF-kappa B linked to a chloramphenicol acetyltransferase reporter gene, we demonstrate that expression of p65, c-Rel, or p50 or combinations of p50-p65 and p65-c-Rel differentially stimulated PRDII-dependent transcription. Coexpression of I kappa B alpha completely abrogated p65-, c-Rel-, or p65-p50-induced gene activity. When the entire IFN-beta promoter (-281 to +19) was used in coexpression studies, synergistic stimulation of IFN-beta promoter activity was obtained when NF-kappa B subunits were coexpressed together with the IFN regulatory factor 1 (IRF-1) transcription factor. Overexpression of either I kappa B or the IRF-2 repressor was able to abrogate inducibility of the IFN-beta promoter. Thus, multiple regulatory events--including differential activation of DNA-binding NF-kappa B heterodimers, degradation of I kappa B alpha, synergistic interaction between IRF-1 and NF-kappa B, and decreased repression by I kappa B and IRF-2--are all required for the transcriptional activation of the IFN-beta promoter.
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PMID:Viral induction of the human beta interferon promoter: modulation of transcription by NF-kappa B/rel proteins and interferon regulatory factors. 803 74


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