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:1.11.1.6 (catalase)
55,569 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The expression of human immunodeficiency virus type 1 (HIV) is enhanced after T cell activation due to the interaction of cell-encoded nuclear factors with binding sites in the viral long terminal repeats (LTR). We studied the minimal signal transduction requirements for induction of HIV transcription during T cell activation. Monoclonal antibodies (mAb) against the T cell receptor/CD3 complex induced interleukin (IL) 2 production as well as HIV-LTR-directed gene expression in Jurkat T cells. Addition of cyclosporin A or buffering of intracellular Ca2+ changes did not abolish this LTR-directed gene expression but did block IL 2 production. In contrast, interference with protein kinase C (PKC) activation did inhibit both IL 2 production and LTR-driven gene expression. Under all conditions HIV-LTR-directed gene expression correlated with gene expression induced by the NF-kB binding enhancer, but not by the NF-AT or OCT-1 binding sites. In accordance with observations by Verweij, Geerts and Aarden on the CD28 co-stimulatory activation of IL2 transcription via an NF-kB-like activity, stimulation of the CD2, CD28 and CD44 accessory molecules was tested to mimick physiological activation signals independent of T cell receptor triggering. mAb directed against CD2 and CD44 only marginally induced the LTR. Next, non-mitogenic stimulation by mAb against CD28 clearly induced the HIV-LTR- and NF-kB- but not NF-AT- and OCT-1-driven chloramphenicol acetyltransferase CAT expression, showing a direct effect on gene expression via this receptor. Taken together, this report shows that non-mitogenic T cell activation signals are sufficient to induce HIV transcription. The finding that these signals may be delivered by receptors that are not dependent on antigen-specific activation may have important implications for our understanding of HIV pathogenesis.
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PMID:Non-mitogenic T cell activation signals are sufficient for induction of human immunodeficiency virus transcription. 184 14

Activation of T lymphocytes infected with the human immunodeficiency virus-1 (HIV-1) results in enhancement of viral replication mediated in part by activation of cellular NF kappa B capable of binding directly to sequences in the viral long terminal repeat, or LTR. Together with CD4+ T cells, macrophages constitute a major target for infection by HIV-1. Unlike lymphocytes, however, stimulation of mononuclear phagocytes is not associated with cell division and proliferation. Human monocyte-derived macrophages transfected with HIV-LTR-CAT constructs demonstrated down-regulation of CAT activity after stimulation with bacterial lipopolysaccharide (LPS) that mapped to a region distinct from NF kappa B binding sites. In contrast, fresh monocytes and the promonocytic U937 cell line both demonstrated up-regulation of HIV-LTR-CAT expression by LPS. Differentiation of U937 by PMA to establish a nondividing phenotype resulted in down-regulation of transfected HIV-LTR-CAT activity by LPS similar to that in mature macrophages. Human monocyte-derived macrophages infected with HIV-1 in vitro demonstrated a decrease in viral p24 release after incubation in LPS that was comparable to the negative regulation that occurred in the transient transfection assays. Factors controlling HIV replication may differ in dividing and nondividing hematopoietic cells and may contribute to restricted viral expression in nondividing cells.
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PMID:Activation of human monocyte--derived macrophages with lipopolysaccharide decreases human immunodeficiency virus replication in vitro at the level of gene expression. 190 15

We have isolated a rat cDNA, named FE65, hybridizing to an mRNA of about 2,300 nucleotides present in rat brain, undetectable in rat liver and very poorly represented in other tissues. An mRNA of the same size is present in human neuroblastoma cells and is absent from other human cell lines. The FE65 cDNA contains an open reading frame (ORF) coding for a polypeptide of 499 amino acids in which 143 residues can be aligned with the DNA binding domain of the integrases encoded by mammalian immunodeficiency viruses. The remaining part of the FE65 ORF is not homologous with the correspondent regions of the integrases; the first 206 residues of the FE65 ORF show numerous negative charges and a short sequence not dispensable for the function of the transactivating acidic domain of the jun family transcriptional factors. A plasmid which expresses FE65 amino acids 1-232 fused to the yeast GAL4 DNA binding domain was co-transfected with a plasmid containing five GAL4 binding sites upstream of a minimal Adenovirus promoter controlling the expression of the CAT gene. This experiment showed that the fused protein GAL4-FE65 is able to obtain a 30-40 fold increase of the CAT gene expression compared to the expression observed in the presence of the GAL4 DNA binding domain alone. Two types of FE65 mRNA are present in rat brain, differing only for six nucleotides. We demonstrate that this is the consequence of a neuron-specific alternative splicing of a six-nucleotide miniexon, which is also present in the human genome, in an intron/exon context very similar to that of the rat FE65 gene.
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PMID:A rat brain mRNA encoding a transcriptional activator homologous to the DNA binding domain of retroviral integrases. 192 10

Transcriptional activation of gene expression directed by the long terminal repeat (LTR) of the human immunodeficiency virus type 1 (HIV-1) requires both the Tat activation response element (TAR) and the Tat protein. Mutants lacking a functional tat gene are not able to replicate. An approach we have used to suppress HIV-1 gene expression is based on the controlled overexpression of multimerized TAR sequences, which results in the sequestration of one or more components of the Tat response. Since Tat has no known cellular analog, a modified HIV-1 LTR, which is highly induced by the presence of Tat, was used to promote the expression of the multimerized TAR (poly-TAR) specifically in the presence of Tat. Cotransfection of an HIV-1 LTR-controlled poly-TAR plasmid with LTR-Tat and LTR-CAT plasmids inhibited the level of the reporter gene activity (CAT) as much as 97%. The downregulation of HIV-1 gene expression observed was dependent on the quantity of transfected poly-TAR as well as the number of tandem TAR repeats expressed per unit transcript. Similar constructs lacking either LTR upstream sequences or the TAR sequence had no significant effect, suggesting that the competitive effect was mediated at the RNA level and that it was the nascent RNA, rather than DNA, that was recognized by the Tat protein. Tat-regulated production of the poly-TAR transcript provides a means for dissecting the mechanism of Tat-mediated trans-activation of the HIV-1 LTR. The ability to regulate a viral inhibitory gene so that it is expressed only when needed should prove useful in devising an antiviral strategy through gene therapy.
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PMID:Tat-regulated production of multimerized TAR RNA inhibits HIV-1 gene expression. 203 68

We have previously shown that PC6, a natural product extracted from cones of Pinus parviflora Sieb et Zucc, can inhibit the replication of human immunodeficiency virus type 1 (HIV-1) in CD4+ T cells and in monocyte/macrophage cell lines. Here, we show by immunoprecipitation of HIV-1 proteins with a specific pooled serum that PC6 inhibited the expression of all HIV-1 proteins in CEM cells. PC6 did not affect the posttranslational processing of the HIV-1 proteins. Northern, Southern, and kinetics analyses revealed that PC6 inhibited HIV-1 reverse and forward transcription in CEM cells. Transient transfection of CEM cells with HIV-1 long terminal repeat (LTR) linked CAT DNA also showed that PC6 inhibited LTR-driven gene expression at the transcriptional level.
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PMID:Inhibition of human immunodeficiency virus forward and reverse transcription by PC6, a natural product from cones of pine trees. 206 32

The rev gene of human immunodeficiency virus type 1 (HIV-1) encodes a 116 amino acid nuclear regulatory protein (Rev) that increases the cytoplasmic expression of viral mRNAs containing the Rev response element (RRE) and coding for the structural proteins, Gag and Env. To identify the functional domains of Rev, amino acid deletion and chain termination mutations were introduced in the Rev coding region. The ability of these mutants to increase the cytoplasmic expression of a Rev-test plasmid (pSV-AR), containing the RRE cloned into the 3' noncoding region of the CAT gene in plasmid pSV2CAT, was examined in transient expression assays in HeLa cells. Our results indicate that three distinct regions mapping within the N-terminal 98 amino acids of Rev are essential for its activity. The subcellular localization of the various Rev proteins was examined in COS cells by indirect immunofluorescence. Rev was found to localize predominantly in the nucleolus of transfected cells. All mutant Rev proteins, with the exception of a deletion mutant (rev delta 41-44) lacking four Arg residues of a highly basic domain, were found to localize in the nucleolus. Mutant rev delta 41-44 exhibited weak diffuse fluorescence in the nucleus with a tendency to accumulate in the cytoplasm. A 15 amino acid region encompassing this basic domain (38-52) when fused to the Escherichia coli beta-galactosidase gene efficiently directed the fusion gene product to the nucleus and nucleolus, suggesting a role for this domain in the nucleolar localization of Rev.
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PMID:Functional domains of the HIV-1 rev gene required for trans-regulation and subcellular localization. 210 12

The nef gene product of human immunodeficiency virus type 1 (HIV-1) has been implicated as a negative factor for viral replication and is suspected to play an important role in the maintenance of viral latency. However, there seems to be evidence both for and against the negative effect of nef gene product. In the present report, we reevaluated the function of the nef gene by means of transient CAT assays with two human T cell lines. In most of the experiments, carefully controlled triplicate studies were carried out. We observed that not only the nef-expression plasmid, but also an effector plasmid containing the nef cDNA sequence in a reverse orientation, not expressing the Nef protein, showed a similar extent of repression of the HIV-1 promoter activity. We also examined the repressive effect of the nef cDNA with deletion mutants of HIV-1 long terminal repeat and heterologous promoters. The results led us to conclude that the apparent "repressor"-like action of the nef cDNA itself could be explained by competition for certain transcription factors required for HIV-1 gene expression by identical sequences also present in the nef cDNA.
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PMID:Repressive effect of the nef cDNA of human immunodeficiency virus type 1 on the promoter activity of the viral long terminal repeat. 212 37

We have used a specific phosphatase inhibitor, okadaic acid, to examine the role of two phosphatases, PP1 and PP2A, in the induction of NF-kappa B and the long terminal repeat of the human immunodeficiency virus type 1 (HIV-LTR). Treatment of Jurkat cells with okadaic acid induced NF-kappa B in nuclear extracts. The rate of induction by okadaic acid was delayed compared to the induction of NF-kappa B by phorbol myristate acetate (PMA). The induction of NF-kappa B by okadaic acid was enhanced by cycloheximide or phytohemagglutinin (PHA). In contrast to PMA, okadaic acid appeared to induce NF-kappa B independently of protein kinase C (PKC). That the NF-kappa B induced by okadaic acid was functional was demonstrated by the marked increase in CAT activity that occurred in Jurkat, BJA-B, and U251 cells that were transfected with HIV-LTR-CAT and treated with okadaic acid. The increase in CAT activity triggered by okadaic acid was dependent on the presence of the NF-kappa B sites in the long terminal repeat of HIV as assessed by deletion and mutation analysis. Similarly to its effect on the induction of NF-kappa B, PHA added together with okadaic acid resulted in a further increase in CAT activity. Somewhat surprisingly, the addition of PMA inhibited the increase in CAT activity in response to okadaic acid, which suggests that the activation of PKC may also induce inhibitory factors.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Induction of nuclear factor-kappa B and the human immunodeficiency virus long terminal repeat by okadaic acid, a specific inhibitor of phosphatases 1 and 2A. 217 54

Human hepatitis B virus (HBV) X-gene, previously shown to be capable of trans-activating heterologous regulatory elements of the human beta-interferon gene, the human immunodeficiency virus type I (HIV-1) long terminal repeat (LTR), the simian virus 40 (SV40), and HBV, has the capacity to code for a 17-kDa polypeptide (designated pX17). We now report that pX17 synthesized in Escherichia coli can activate transcription controlled by the HIV-1 LTR using a protoplast fusion technique. Protoplasts of E. coli-containing presynthesized X-protein were fused with lymphocytic H938 cells harboring an integrated copy of a plasmid with the CAT gene under control of the HIV-1 LTR (HIV-1 LTR CAT) and a marked increase in the steady state expression of the CAT mRNA was observed. When the same fused cells were treated with the protein synthesis inhibitor cyclohexamide, the pX17-dependent activation of the HIV-1 LTR was abolished. This result indicates that the X-protein expressed in E. coli is biologically active and suggests that the HBV X-protein-mediated trans-activation of the HIV-1 LTR in this system requires de novo cellular protein synthesis.
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PMID:Transcriptional activation of the human immunodeficiency virus type 1 long terminal repeat by hepatitis B virus X-protein requires de novo protein synthesis. 219

Lipopolysaccharide (LPS) potently stimulates human immunodeficiency virus type 1-long terminal repeat (HIV-1-LTR) CAT constructs transfected into monocyte/macrophage-like cell lines but not a T cell line. This effect appears to be mediated through the induction of nuclear factor kappa B (NF-kappa B). Electrophoretic mobility shift assays demonstrate that LPS induces a DNA binding activity indistinguishable from NF-kappa B in U937 and THP-1 cells. LPS is also shown to dramatically increase HIV-1 production from a chronically infected monocyte/macrophage-like cloned cell line, U1, which produces very low levels of HIV-1 at baseline. The stimulation of viral production from this cell line occurs only if these cells are treated with granulocyte/macrophage colony-stimulating factor (GM-CSF) before treatment with LPS. This stimulation of HIV-1 production is correlated with an increase in the level of HIV-1 RNA and and activation of NF-kappa B. LPS is not able to induce HIV-1 production in a cloned T cell line. The effect of LPS on HIV-1 replication occurs at picogram per milliliter concentrations and may be clinically significant in understanding the variability of the natural history of HIV-1 infection.
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PMID:Lipopolysaccharide is a potent monocyte/macrophage-specific stimulator of human immunodeficiency virus type 1 expression. 219 97


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