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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human foamy virus (HFV) encodes the transcriptional transactivator bel1. The bel1 protein transactivates HFV long terminal repeat (LTR)-directed gene expression by recognizing a region in U3. It also transactivates human immunodeficiency virus type 1 (HIV-1) LTR-directed gene expression in transient transfection assays. To identify the specific region in HIV-1 LTR responsible for bel1 action, we examined the effect of bel1 on chloramphenicol acetyltransferase (CAT) gene expression in transfected cells with a series of mutant HIV-1 LTR/CAT plasmids. The region between -158 and -118 from the transcription initiation site, immediately upstream of the core enhancer element, was identified as responsible for the transactivation by bel1. In addition, bel1 transactivated a heterologous promoter when this region was positioned upstream of it in the sense and antisense orientations. Optimal transactivation of the HIV-1 LTR by bel1 did not require an intact TAR sequence, suggesting that the binding of tat to the TAR sequence is not a prerequisite for bel1 function in HIV-1 LTR-directed gene expression. In the region of the HIV-1 LTR that is necessary for the bel1-mediated transactivation, we have found a sequence which is conserved between HIV-1 and HFV. Our results suggest that the bel1 action on HIV-1 seems to be mediated by a specific DNA sequence which is shared by both the HIV-1 LTR and HFV LTR.
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PMID:Transactivation of human immunodeficiency virus type 1 long terminal repeat-directed gene expression by the human foamy virus bel1 protein requires a specific DNA sequence. 131 28

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

A new method is described for the direct construction of randomly mutagenized genes by applying the polymerase chain reaction (PCR) to an oligonucleotide synthesized using doped nucleotide reservoirs. We have demonstrated the utility of this method by generating a library of mutant HIV-1 tat genes. Several arbitrarily selected, inactive tat clones were sequenced to evaluate the extent of the mutagenesis. Moreover, fourteen recombinants encoding varying levels of transcriptional trans-activator activity were isolated by transient transfection of sub-library pools into a HeLa cell line bearing an HIV-LTR-chloramphenicol acetyltransferase (CAT) reporter gene. Sequence data revealed a spectrum of alterations including nucleotide substitutions, insertions, and deletions, suggesting that mutations arose from both the doped DNA synthesis and the subsequent PCR 'rescue' of full-length product. Sequence comparison between inactive and active Tat clones revealed a selection pressure against amino-acid substitutions within the N-terminal domains of Tat, indicating the importance of this region to trans-activation competence. In addition, single and double missense mutations within the basic-rich, TAR RNA-binding domain were seen to be tolerated within active Tat clones.
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PMID:Random mutagenesis of the human immunodeficiency virus type-1 trans-activator of transcription (HIV-1 Tat). 143 50

A complementation assay is described that can be used with relative safety to quantitate rapidly inhibitory effects of potential anti-HIV-1 drugs on virtually any stage of the HIV-1 life cycle by measurements of chloramphenicol acetyltransferase (CAT) activity. Of particular interest is that this system is also capable of detecting inhibition of the viral trans-activator Rev, an important potential target for drug intervention. Other applications of the system may include studies to identify domains of the envelope glycoprotein that determine infectivity and tropism or that define epitopes recognized by neutralization antibodies.
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PMID:Rapid complementation assay for anti-HIV-1 drug screening and analysis of envelope protein function. 145 18

Transcription from the human immunodeficiency virus type 1 (HIV-1) provirus is activated by a cellular factor, NF kappa B, recognizing the tandemly repeated 10-base-pair sequences, termed the kappa B sequence, present in the enhancer region within the viral long terminal repeat (LTR). Using electrophoretic mobility shift assay (EMSA), which demonstrates specific DNA-protein interaction in vitro, we could demonstrate that reducto-oxidative modulation of NF kappa B dramatically changes its DNA binding activity and that a cellular physiological reducing catalyst, thioredoxin (TRX) also known as adult T cell leukemia derived factor (ADF), fully restored the DNA-binding activity of the oxidized NF kappa B. We also observed that purified TRX/ADF protein could augment gene expression from HIV LTR as demonstrated by transient chloramphenicol acetyltransferase (CAT) assay. These observations confirmed the previous notion that ADF might be an inducing factor of cellular interleukin-2 receptor alpha subunit (IL-2R alpha) through the kappa B sequence that is a common central cis-regulatory element in both IL-2R alpha and HIV gene expression. These observations indicate that reducto-oxidative regulation (or redox regulation) of a cysteine residue(s) on the NF kappa B molecule might play an important role in its specific DNA interaction and that it might provide a clue to the understanding of a pathway of cellular signal transduction to NF kappa B that is independent from the known pathways involving protein phosphorylation.
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PMID:Human thioredoxin/adult T cell leukemia-derived factor activates the enhancer binding protein of human immunodeficiency virus type 1 by thiol redox control mechanism. 149 89

A variety of DNA viruses are known to activate gene expression directed by the long terminal repeat (LTR) of human immunodeficiency virus type 1 (HIV-1). In light of the proposed use of recombinant vaccinia virus for HIV-1 vaccines, evaluation of the role of vaccinia virus in HIV-1 activation is warranted. To investigate whether vaccinia virus induces HIV LTR-directed gene expression, transient expression assays in Jurkat cells persistently infected with vaccinia virus (Jvac) using plasmid DNA containing the LTR linked to the bacterial chloramphenicol acetyltransferase (CAT) gene were performed. CAT activity in Jvac cells was always recorded, although the level appears to fluctuate independently of virus titers. Dual intracytoplasmic staining and fluorescence-activated cell sorter analysis showed that CAT activity was expressed in the infected cells. CAT expression was not due to plasmid replication, since plasmid DNA extracted from Jvac cells 48 h after transfection was restricted only by enzymes which recognize methylated sequences, indicating a prokaryotic source for the DNA. These findings suggest that a factor(s) present in vaccinia virus-infected cells is capable of activating the LTR of HIV-1.
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PMID:Activation of the human immunodeficiency virus type 1 long terminal repeat by vaccinia virus. 154 51

Antisense oligodeoxynucleotide (ODN), which are directed against the splice acceptor site of exon II of the regulatory gene tat of the human immunodeficiency virus type 1 (HIV-1), have been described. These 20-mer ODN's displayed moderate anti-HIV activity in vitro. Using the same antisense ODN (termed ODN-2), which was additionally modified and protected both at the 3'- and the 5'-terminus by two phosphorothioate internucleotide linkages, a strong anti-HIV activity (EC50: 2.7 micrograms/ml) could be measured in the HIV-1/CEM- and HIV-1/HeLa-T4+ cell system. The analogous ODNs which were protected only at one end were either inactive (up to 10 micrograms/ml) or displayed a low antiviral activity. Time kinetic studies revealed that the antisense ODN-2 reduced the release of HIV-1 already after an incubation time of 1 h. By applying S1 nuclease protection procedures, it could be established that the antisense ODN-2 inhibited splicing of high molecular weight transcript to the 2-kb tat mRNA in HIV-1-infected CEM cells. Transfection experiments with pU3R-III chloramphenicol acetyltransferase expression vector in HeLa-T4+ cells revealed that the antisense ODN-2 blocked the Tat protein-mediated transactivation process. In co-transfection experiments using pSV2tat72 or scrape loading studies with purified Tat, the transactivation was restored. These data indicate that the selected antisense ODN-2 displays its anti-HIV effect by blocking the splicing process leading to the functional 2-kb tat mRNA.
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PMID:Antisense oligodeoxynucleotide: inhibitor of splicing of mRNA of human immunodeficiency virus. 156 36

We have analyzed the transcriptional activity of the human immunodeficiency virus type I (HIV-1) LTR promoter in the fission yeast Schizosaccharomyces pombe (S.pombe). The ability of a series of 5'-deleted forms of the HIV-1 LTR promoter to direct transcription of the chloramphenicol acetyltransferase reporter gene was studied. We found that the HIV-1 promoter is functional in S.pombe and that deletion of sequences upstream of the NF-kB binding site previously identified to contain the negative regulatory element (NRE) in mammalian cells, resulted in about thirty-fold increase in transcriptional activity. Sequences in the HIV-1 promoter that bind NF-kB were found to be essential for transcriptional activation in S.pombe. In mammalian cells, transactivation of the HIV-1 LTR requires TAR sequences and the viral Tat protein. In fission yeast, Tat failed to transactivate the HIV-1 LTR, suggesting that S.pombe may lack a cellular factor(s) required for the Tat transactivation process.
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PMID:Transcriptional activity of the human immunodeficiency virus-1 LTR promoter in fission yeast Schizosaccharomyces pombe. 159 18

The induction of human immunodeficiency virus type 1 (HIV-1) gene expression by cytokines was investigated in cells of central nervous system origin. These were human neuroblastoma, glioblastoma, and astrocytoma cell lines, a murine oligodendroglioma and primary murine astrocyte cultures. The cytokines used were tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), IL-6, and interferons alpha and gamma (IFN alpha, gamma). Transient transfection of cells with a chloramphenicol acetyltransferase (CAT) reporter gene under the control of the HIV-1 long terminal repeat (LTR) showed significant augmentation following treatment by particular cytokines. TNF alpha was found to augment HIV LTR-directed CAT activity in all cell types. IL-1 beta also activated the HIV LTR reporter gene in glioblastoma, astrocytoma, and astrocyte cells. IL-6 enhanced HIV gene expression in one example only, the primary astrocyte cultures. The interferons generally suppressed expression from the LTR except IFN gamma which produced a twofold rise in the murine glial cells and IFN alpha augmenting expression in one neuroblastoma cell line. No synergy was observed between pairs of activating cytokines tested. The HIV tat gene product was found to be functional in all cells, cotransfection of a tat expression vector transactivating expression from the LTR, with varying degrees of efficiency. In some cell lines the combination of an activating cytokine and tat resulted in an enhancement above that obtained by cotransfection of tat alone. In others, the level of CAT activity did not significantly change. Analysis of nuclear extracts from cytokine-treated cells further implicated the involvement of NFKB in the induction of HIV-1 gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cytokine augmentation of HIV-1 LTR-driven gene expression in neural cells. 159 55

cis-acting inhibitory region (IR) sequences were identified within the gag/pol gene of the human immunodeficiency virus type 1 (HIV-1) by using a novel feedback-stimulated, rev-independent tat reporter gene to screen HIV-1 sequences in transient expression assays. Two regions, a 1,295-nucleotide segment in the gag gene (IR-1) and a 1,932-nucleotide segment of the pol gene (IR-2), each inhibited reporter gene expression 10- to 20-fold. IR-1 and IR-2 both contained subsequences which inhibited reporter gene expression. Introduction of IR sequences into a heterologous reporter plasmid, pCMV-CAT, resulted in decreased chloramphenicol acetyltransferase expression, suggesting that the inhibitory effect was not restricted to a reporter gene under the control of the HIV-1 promoter. The presence of HIV IR sequences in cis did not alter relative levels of reporter gene RNA; however, fractionation studies revealed IR-containing RNA accumulated in the nucleus. These findings demonstrate that IR sequences within the gag/pol region affect gene expression by altering the cellular distribution of viral RNA.
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PMID:Identification of posttranscriptionally active inhibitory sequences in human immunodeficiency virus type 1 RNA: novel level of gene regulation. 165 66


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