Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A gene encoding the human immunodeficiency virus-1 (HIV-1) TAT protein was chemically synthesized and expressed in HeLa cells and in a cell-free system. To facilitate both the assembly of the synthetic gene and further mutagenesis and gene fusion studies, several unique restriction endonuclease cleavage sites were included in the coding sequence without altering the encoded protein sequence. The synthetic TAT coding sequence was fused to a translation start signal and placed under SV40 early transcriptional control. Co-transfection of the TAT-encoding synthetic gene together with a reporter gene (chloramphenical acetyl transferase or beta-galactosidase) linked to an HIV LTR confirmed that the synthetic gene product exhibits similar activity to TAT expressed from HIV genomic DNA in the transactivation of the LTR. TAT mRNA prepared by cell-free transcription of the synthetic TAT coding sequence was also shown to produce functional TAT following microinjection into HeLa-derived cells containing an integrated reporter gene with the HIV LTR linked to beta-galactosidase.
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PMID:Chemical synthesis and expression of a gene encoding HIV-1 TAT protein. 254

Replication of the human immunodeficiency virus (HIV-1) depends upon the viral TAT protein. TAT stimulates gene expression via a target response sequence (TAR) located within the HIV-1 LTR. As TAR is located in the transcribed region it could act as a signal in either the DNA, the RNA, or both. To test whether TAT acts on transcription and/or posttranscriptionally, we produced TAT in yeast and monitored its activity after microinjection into the nucleus or cytoplasm of Xenopus oocytes. The TAT protein stimulated TAR-dependent expression, but this activation was not inhibited by transcriptional inhibitors. Furthermore, TAR-containing RNA, produced in vitro, was "activated" by TAT after coinjection into oocytes. This activation only occurred, however, when the RNA was injected into the nucleus and not into the cytoplasm. Our data indicate, therefore, that in the Xenopus system TAT acts on presynthesized RNA and that the nucleus is involved in this action.
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PMID:HIV-1 TAT "activates" presynthesized RNA in the nucleus. 254 79

The synthesis of a gene for the HIV TAT protein is described using a novel approach that capitalises on the ability to synthesise oligonucleotides of greater than 100 bp in length. It involves the synthesis of large oligomers covering one strand of the desired gene in its entirety and the use of small complementary bridging and adapter oligonucleotides to direct the assembly and cloning of the large oligomers. After ligation to the cloning vector the partially single stranded intermediate is transformed directly into the recipient bacterial host where the plasmid is repaired. The synthetic tat gene has been expressed in HeLa cells and is shown to trans-activate TAR+ but not TAR- HIV LTR-CAT constructs.
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PMID:Synthesis of a gene for the HIV transactivator protein TAT by a novel single stranded approach involving in vivo gap repair. 328 69

The TAR sequence at the 5'-termini of all HIV-1 mRNA species forms a stable structure that is responsible for both transcriptional and translational regulation of HIV-1. Previously we and others reported that purified TAR RNA synthesized by in vitro transcription could activate two interferon-induced enzymes, the protein kinase (PKR) and 2-5A-synthetase. Because the PKR- and 2-5A-systems block protein synthesis initiation and induce RNA decay, respectively, these findings suggested mechanisms for the control of HIV-1 replication by the interferon system. To determine if contaminating dsRNA from in vitro transcription reactions was responsible for this effect, as suggested by Gunnery et al. 1990, (Proc., Natl. Acad. Sci. USA 87, 8687), we have reexamined these findings using chemically synthesized TAR (nucleotides +1 to +57). TAR RNA is shown here to have an intrinsic ability to activate PKR and 2-5A-synthetase. In contrast, a mutant form of TAR designed to have a disrupted secondary structure did not stimulate either enzyme. Chemically synthesized TAR mimicked other dsRNA species in its ability to activate and inhibit PKR at low and high RNA concentrations, respectively. HIV-1 TAT protein inhibited activation of PKR by HIV-1 TAR RNA suggesting an escape mechanism for the virus.
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PMID:HIV-1 TAR RNA has an intrinsic ability to activate interferon-inducible enzymes. 752 41

Two peptide analogs of the 37-62 sequence region of the HIV TAT protein bind tightly to the surface of A431 breast carcinoma cells. After conjugation to either of two poorly internalized anti-tumor antibody Fab fragments, the analogs enhanced the in vitro cell surface retention and internalization of the Fab fragments to the level of the whole antibodies. This was at the expense of some binding specificity in the case of 1.6 peptides/NRLU-10 Fab, but not in the case of 1.1 peptides/Fab. Enhanced retention may occur by enhanced bivalent binding of the Fab fragments. The internalized fraction of free peptide, but not of the Fab conjugates, is enhanced by chloroquine. The conjugates which were less specific for tumor cell binding may be useful for enhanced retention/internalization of specifically acting agents, for use at specific sites of injection, or against pre-separated target cell populations, while the more specific conjugate may be of interest for further development.
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PMID:Tumor cell retention of antibody Fab fragments is enhanced by an attached HIV TAT protein-derived peptide. 834 70

Human immunodeficiency virus (HIV-1) gene expression is activated by the viral TAT protein that interacts with an RNA sequence, TAR, located at the 5' end of all viral mRNAs. TAT functions primarily as a transcriptional activator in mammalian cells. However, in Xenopus oocytes TAT functions primarily as a translational activator. TAR is an RNA structure comprising a partially base-paired stem, a tripyrimidine bulge in the upper stem, and an unpaired six-nucleotide loop. In vitro, TAT binds directly to the bulge with no requirement for the loop. In vivo, however, mutations in the loop abolish TAT activation of transcription and translation, implying a requirement for TAR-binding cellular factors. We now provide genetic evidence for the presence of two TAR-specific cellular factors in Xenopus oocytes. These factors display independent and mutually exclusive interactions with either the loop or the bulge region of TAR. Furthermore, by using in vivo RNA competition assays we show that the cellular factors regulate the accessibility of the TAT binding site. The fact that Xenopus oocytes contain factors that specifically interact with a human viral RNA sequence might indicate that the TAT/TAR interaction is subverting a conserved pathway in the cell.
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PMID:HIV-1 TAR RNA-binding proteins control TAT activation of translation in Xenopus oocytes. 842 67

The trans-activator of transcription or TAT gene from HIV-1 encodes a protein that increases the processivity of transcription from the HIV-1 genome. TAT protein can also affect cellular processes in the absence of its ribonucleic HIV target sequence trans activation response element and may be responsible for some aspects of HIV pathogenesis apart from infectious virus or other viral gene products. We have previously shown that TAT72 decreases CTL activity in TAT72-transgenic mice, and we now demonstrate aberrant regulation of mitogen-elicited IL-2 at both transcriptional and translational levels. In contrast, alloantigen stimulation resulted in increased IL-6 and IL-10 production in the TAT72-transgenic mice. Con A-stimulated cultures of splenic lymphocytes from TAT72-transgenic mice do not undergo clonal proliferation of CD4+ cells as compared with CD8+ cells monitored over 72 h. These results suggest that TAT is sufficient to induce some pathology associated with AIDS and is a potent immunologic manipulator apart from its function as trans-activator.
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PMID:Aberrant regulation of cytokines in HIV-1 TAT72-transgenic mice. 862 96

TAT protein is an essential regulatory protein of the human immunodeficiency virus type 1 (HIV-1). Inhibition of TAT activity blocks the virus cycle, and a drug that blocks TAT is one of the possibilities to cure AIDS. Circular dichroism (CD) was measured for TAT peptides covering the TAT sequence with overlaps. The CD spectrum of each peptide was measured in different solvents to evaluate the ability of each TAT region to form different secondary structures. The most variation or conformational heterogeneity is observed with the two regions adjacent to the TAT basic region. CD data show that the basic region can adopt an extended structure in a full TAT protein, which is not the case for the isolated peptide. TAT sequences from the different HIV-1 isolates were analyzed, and the results showed that the sequences could be gathered into six groups. Molecular modeling was done on the various isolates based on a TAT structure from two-dimensional NMR. After minimization and dynamic steps, the modeled three-dimensional structures were compared. The results showed structural variations of the TAT protein as a function of the HIV-1 isolates. These structural variations were mainly in the two regions adjacent to the basic region, confirming the conformational heterogeneity indicated by the CD measurements. Furthermore, Chou-Fasman analysis shows significant changes in propensities for each secondary structure only for regions III and V. This conformational heterogeneity should be essential for TAT activity and points out that regions III and V are a poor potential target to design a TAT ligand. We propose a target involving TAT structurally conserved regions, accessible whatever the size of the TAT C terminus.
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PMID:Conformational heterogeneity in two regions of TAT results in structural variations of this protein as a function of HIV-1 isolates. 879 35

A change of mitochondrial membrane permeability is essential for apoptosis, leading to translocation of apoptogenic cytochrome c and apoptosis-inducing factor into the cytoplasm. We recently showed that the Bcl-2 family of proteins regulate cytochrome c release and the mitochondrial membrane potential (Deltapsi) by directly modulating the activity of the voltage-dependent anion channel (VDAC) through binding. Here we investigated the biochemical role of the conserved N-terminal homology domain (BH4) of Bcl-x(L), which has been shown to be essential for inhibition of apoptosis, with respect to the regulation of mitochondrial membrane permeability and found that BH4 was required for Bcl-x(L) to prevent cytochrome c release and Deltapsi loss. A study using VDAC liposomes revealed that Bcl-x(L), but not Bcl-x(L) lacking the BH4 domain, inhibited VDAC activity. Furthermore, BH4 oligopeptides of Bcl-2 and Bcl-x(L), but not mutant peptides, were able to inhibit both VDAC activity on liposomes even in the presence of Bax and apoptotic Deltapsi loss in isolated mitochondria. It was also shown that the BH4 domain, fused to the protein transduction domain of HIV TAT protein (TAT-BH4), efficiently prevented apoptotic cell death. These results indicate that the BH4 of Bcl-2/Bcl-x(L) is essential and sufficient for inhibiting VDAC activity, which in turn prevents apoptotic mitochondrial changes, and for preventing apoptotic cell death. Finally, the data suggest that the TAT-BH4 peptide is potentially useful as a therapeutic agent for diseases caused by accelerated apoptosis.
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PMID:BH4 domain of antiapoptotic Bcl-2 family members closes voltage-dependent anion channel and inhibits apoptotic mitochondrial changes and cell death. 1073 88

The protein transduction domain (PTD) embedded in the HIV TAT protein (amino acids 47-57) has been shown to successfully mediate the introduction of heterologous peptides and proteins in excess of Mr 100,000 into mammalian cells in vitro and in vivo. We report here that the modeled structure of the TAT PTD is a strong amphipathic helix. On the basis of this information, we synthesized a series of synthetic PTDs that strengthen the alpha-helical content and optimize the placement of arginine residues. Several PTD peptides possessed significantly enhanced protein transduction potential compared with TAT in vitro and in vivo. These optimized PTDs have the potential to deliver both existing and novel anticancer therapeutics.
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PMID:Synthetic protein transduction domains: enhanced transduction potential in vitro and in vivo. 1121 34


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