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)

We report here the discovery of HMBP, a protein in nuclei of human T-helper lymphocytes and other human cell types, which binds with enhanced affinity to a promoter element in the HIV-1 long terminal repeat when that element is methylated at CpGs, the target site of the human DNA methyltransferase. This promoter element contains three (degenerate) binding sites for Sp1, a general activator of transcription. Gel shift assays and footprinting experiments indicate that HMBP binding overlaps two of these methylated Sp1 sites. Although HMBP binds these methylated Sp1 sites, it does not bind consensus Sp1 sites. Competition studies, differences in binding site specificities, binding conditions, and, in some cases, chromatographic separation further distinguish HMBP from Sp1 and from each of four previously identified methylated-DNA binding proteins. HMBP binds hemimethylated DNA in a strand dependent manner. These binding characteristics suggest that HMBP may recognize newly replicated DNA and thereby play a role in differentiation. If HMBP is able to compete with Sp1 for binding at methylated, non-consensus Sp1 sites in vivo and repress transcription, it may play a role in AIDS latency.
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PMID:A nuclear protein with enhanced binding to methylated Sp1 sites in the AIDS virus promoter. 828 30

Recently, we have shown that the human immunodeficiency virus (HIV-1) long terminal repeat (LTR) directed chloramphenicol acetyltransferase (CAT) gene is efficiently expressed in human hepatoblastoma HepG2 cells and these cells can support productive HIV-1 replication. In this study we show that HepG2 cells contain a nuclear factor that binds to the HIV-1 trans-activating region (TAR), which we named HepG2-derived TAR binding protein (HTBP). Gel retardation assays using synthetic oligonucleotide probes carrying different mutations in the TAR region and competition DNA mobility-shift experiments using these oligonucleotides revealed the binding site encompassing between +7 and +13 nucleotides (5'-TCTGGTT-3') in the HIV-1 LTR. An in vivo CAT competition assay using -65HIV-1 LTR CAT as a reporter plasmid and various competitor plasmids containing these mutated oligonucleotides also demonstrated that HTBP can influence the HIV-1 LTR-directed CAT gene expression in HepG2 cells by interaction with a specific sequence in the TAR region.
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PMID:Identification of a human immunodeficiency virus type 1 TAR binding protein in human hepatoblastoma HepG2 cells that trans-activates HIV-1 LTR-directed gene expression. 828 41

The V3 loop of the HIV (human immunodeficiency virus)-1 envelope glycoprotein gp120 likely plays a role in HIV-1 infectivity. Although the amino acid sequence of the V3 loop is hypervariable, it contains a conserved region, Gly-Pro-Gly-Arg, that shows similarity to the active-site Gly-Pro-Cys-Arg sequence of inter-alpha-trypsin and trypstatin proteinase inhibitors. The purpose of the present work was to identify proteinases recognizing substrates with basic amino acids in the P1 substrate site that are present in MOLT-4 cells, a human CD4-positive T helper lymphocyte cell line, and to characterize these enzymes in terms of substrate, pH and ionic-strength preferences, size and susceptibility to various inhibitors, including 24- and 36-amino-acid-long V3 loop peptides. Extraction of MOLT-4 cells at low ionic strength solubilized nearly all of the trypsin-like activity, which was separable into five peaks of activity by chromatography on Mono-Q: Peaks 1, 2a, 2b, 3 and 4. All showed a neutral pH optimum, and all except Peak 4 showed optimal activity at high ionic strength. Peak 1 preferred Tos-Gly-Pro-Arg, p-nitroanilide (-pNA) substrate; Peaks 2-4 preferred benzyloxycarbonyl-Val-Leu-Gly-Arg-pNA. Peak 1, a zinc-dependent enzyme with serine and histidine in the active site, exhibited an M(r) of 75,000 on Superose 12 and was poorly inhibited by V3 loop peptides. Peak 2 contained two overlapping peaks, called 2a and 2b, that exhibited properties of zinc-dependent metalloproteinases. Gel filtration of Peak 2 activities revealed a major peak of activity at 81 kDa and a shoulder centred at 240 kDa. Each was modestly inhibited by V3 loop peptides. Peak 3, a zinc-dependent proteinase, exhibited a molecular mass of 100 kDa by gel filtration and was particularly sensitive to inhibition by V3 loop peptides. Peak 4 exhibited a molecular mass of 1100 kDa by gel filtration and was not inhibited by V3 loop peptides. None of these enzymes could be classified as mast-cell tryptase, and material in MOLT-4 cells cross-reactive with anti-(human tryptase) antibodies was not detected. Whether any of the MOLT-4 proteinases described in this study play a role in HIV-1 infectivity remains to be examined.
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PMID:Separation and partial characterization of proteinases with substrate specificity for basic amino acids from human MOLT-4 T lymphocytes: identification of those inhibited by variable-loop-V3 peptides of HIV-1 (human immunodeficiency virus-1) envelope glycoprotein. 831 3

The protein kinase inhibitor 2-aminopurine (2-AP) greatly stimulated expression in human promonocytes-macrophages of plasmid constructs carrying various reporter genes (chloramphenicol acetyltransferase, lacZ, firefly luciferase [luc], and Salmonella typhimurium histidinol dehydrogenase [his]) driven by the human immunodeficiency virus type 1 (HIV-1) long terminal repeat. Adenine, adenosine, and caffeine were also effective inducers, but other purine or pyrimidine derivatives were ineffective. Experiments with mutant derivatives of the HIV-1 long terminal repeat revealed no specific eukaryotic promoter elements necessary for 2-AP induction but indicated the need for some minimum combination of such elements. Induction of HIV-1-directed gene expression appeared not to require action of the transcription factor NF-kappa B. The mechanism of induction was investigated by using the luc and his genes linked to the HIV-1 long terminal repeat. 2-AP induced marked, steady rises in mRNA accumulation from both transfected and chromosomally integrated HIV-1 constructs but no increases from an endogenous gene encoding gamma-actin or glucose 6-phosphate dehydrogenase. Thus, induction is selective and not an artifact induced by transfecting DNA into cells. In run-on transcription experiments, the rates of transcription initiation of both transfected and integrated copies of the his gene increased about sixfold in cells treated with 2-AP. Thus, while increased initiation accounted for a portion of 2-AP induction, it could not cause the far greater increase in steady-state mRNA levels. 2-AP induction did not change mRNA decay rates and differed from the phorbol ester (phorbol myristate acetate)-induced activation of the protein kinase C-NF-kappa B pathway in its time course and in its requirement for new protein synthesis. Gel retardation assays showed that unlike phorbol myristate acetate induction, 2-AP induction is enhancer independent. Whereas many previous studies have implicated the activation of various protein kinases in gene induction, we here describe a mechanism of gene activation that appears to involve protein kinase inhibition as a component of the induction response.
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PMID:Inducible transcriptional activation of the human immunodeficiency virus long terminal repeat by protein kinase inhibitors. 835 80

We report that thyroid hormone (T3) receptor (T3R) can activate the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR). Purified chick T3R-alpha 1 (cT3R-alpha 1) binds as monomers and homodimers to a region in the LTR (nucleotides -104 to -75 [-104/-75]) which contains two tandem NF-kappa B binding sites and to a region (-80/-45) which contains three Sp1 binding sites. In contrast, human retinoic acid receptor alpha (RAR-alpha) and mouse retinoid X receptor beta (RXR-beta) do not bind to these elements. However, RXR-beta binds to these elements as heterodimers with cT3R-alpha 1 and to a lesser extent with RAR-alpha. Gel mobility shift assays also revealed that purified NF-kappa B p50/65 or p50/50 can bind to one but not both NF-kappa B sites simultaneously. Although the binding sites for p50/65, p50/50, and T3R, or Sp1 and T3R, overlap, their binding is mutually exclusive, and with the inclusion of RXR-beta, the major complex is the RXR-beta-cT3R-alpha 1 heterodimer. The NF-kappa B region of the LTR and the NF-kappa B elements from the kappa light chain enhancer both function as T3 response elements (TREs) when linked to a heterologous promoter. The TREs in the HIV-1 NF-kappa B sites appear to be organized as a direct repeat with an 8- or 10-bp gap between the half-sites. Mutations within the NF-kappa B motifs which eliminate binding of cT3R-alpha 1 also abolish stimulation by T3, indicating that cT3R-alpha 1 binding to the Sp1 region does not independently mediate activation by T3. The Sp1 region, however, is converted to a functionally strong TRE by the viral tat factor. These studies indicate that the HIV-1 LTR contains both tat-dependent and tat-independent TREs and reveal the potential for T3R to modulate other genes containing NF-kappa B- and Sp1-like elements. Furthermore, they indicate the importance of other transcription factors in determining whether certain T3R DNA binding sequences can function as an active TRE.
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PMID:The NF-kappa B and Sp1 motifs of the human immunodeficiency virus type 1 long terminal repeat function as novel thyroid hormone response elements. 839 43

Patients with human immunodeficiency virus-type 1-immune thrombocytopenic purpura (HIV-1-ITP) have elevated polyethylene glycol (PEG)-precipitable immune complexes (ICs) composed of IgG, IgM, and complement that are threefold to sevenfold higher than in healthy control subjects. These complexes contain anti-F (ab')2 as well as anti-idiotype antibodies versus anti-HIV-1gp120. Because anti-F (ab')2 and anti-idiotype antibodies correlate with thrombocytopenia (r = .83 [J Clin Invest 77:1756, 1986] and r = .90 [J Clin Invest 89:356, 1992], respectively) we studied the binding of ICs to platelets and monocytes as well as their role in platelet-monocyte rosette formation. ICs bind to platelets in a saturation-dependent manner (optimum at 10 micrograms/mL; 0.5% of serum conc). Binding to platelets could not be inhibited with platelet saturating concentrations of aggregated IgG or with monoclonal antibody (MoAb) IV.3 versus FcR gamma II. Platelet binding could be inhibited with Fab anti-C3, anti-Clq, or anti-C4 by 57%, 40%, and 46% respectively, not with control Fab (P < .001). Monocytes from HIV-1-ITP patients form rosettes with normal platelets 16.8 +/- 5.2 rosettes/100 monocytes compared with 4.8 +/- 0.8 control monocytes plus normal platelets (P = .009). Gel-washed HIV-1-ITP platelets formed 19 +/- 2.0 rosettes with U937 cells compared to 6.3 +/- 1.0 for normal platelets (P = 0.001). Arming of U937 cells with HIV-1-ITP ICs (5 micrograms/mL) formed 36.7 +/- 2.5 rosettes compared with 10.6 +/- 1.2 for control ICs (P < .01). Rosetting of armed U937 cells could be inhibited with MoAbs versus the alpha chains of CD11a (LFA-1), 11b (Mac-1), or 11c (p150,95) by 67%, 70%, and 61%, respectively (P < .007), whereas binding of ICs to U937 cells was unaffected. Isotype-matched control as well as MoAbs versus antigens on U937 cells (CD13, CD33) or the anti-FcR gamma II receptor had no effect. However, Fab fragments of polyclonal anti-C3 inhibited rosette formation by 78% (P < .01); control Fab had no effect. Thus, platelet-monocyte rosette formation is not Fc dependent. It is complement receptor dependent and requires the cooperation of all three leuCAM integrins.
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PMID:Role of leuCAM integrins and complement in platelet-monocyte rosette formation induced by immune complexes of human immunodeficiency virus-type 1-immune thrombocytopenic purpura patients. 848 17

Suramin, a polysulphonated naphthylurea, has antiproliferative, anticancer, and anti-HIV activities and has been shown to prevent binding of a variety of growth factors to their respective receptors. In the current study we have investigated the effects of suramin on binding of interleukin-4 (IL-4) to its receptors and IL-4-induced biological response. We found that suramin prevented the binding of 125I-labeled IL-4 to its receptor in a dose-dependent manner. The concentration of suramin that caused 50% inhibition of IL-4 binding (IC50) ranged between 55 and 70 microM. This effect was observed on two human renal cell carcinoma cell lines (PM-RCC and WS-RCC), a human T lymphoma cell line (H9), and a human premyeloid cell line (TF-1). Cross-linking experiments provided direct evidence that suramin prevented binding of 125I-labeled IL-4 to its receptors. Radiolabeled IL-4 specifically cross-linked with major proteins of approximately 145 and 65-70 kDa in both PM-RCC and H9 cell lines. Suramin prevented cross-linking to both affinity cross-linked IL-4 binding proteins. Gel filtration results indicated that suramin caused aggregation of 125I-labeled IL-4. Suramin had a cytostatic rather than cytotoxic effect on H9 cells, and it inhibited IL-4-induced proliferation of TF-1 cells. These data indicate that suramin may be a useful drug in the abrogation of IL-4-induced effects, and this property should be further explored in IL-4-mediated pathologic states.
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PMID:Suramin blocks binding of interleukin-4 to its receptors on human tumor cells and interleukin-4-induced mitogenic response. 853 28

Circular exon sequences can be generated by splicing permuted intron-exon (PIE) sequences. The Anabaena pre-tRNA group I self-splicing PIE sequence was modified to generate circular forms of the HIV-TAR and the high affinity region of the HIV-RRE (RBE). RNA products containing TAR and the RBE were purified from splicing reactions and demonstrated to be circular. The circular form of these sequences was shown to be resistant to nuclease degradation in cellular extracts. Gel shift assays demonstrate that the circular form of the RBE is specifically bound by a Rev derived peptide. These data suggest that PIE-circularization of RNA may be an effective way to express small stable RNAs designed for therapeutics (eg-decoys).
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PMID:Generation of nuclease resistant circular RNA decoys for HIV-Tat and HIV-Rev by autocatalytic splicing. 864 55

Circular exon sequences can be generated by splicing permuted intron-exon (PIE) sequences. The Anabaena pre-tRNA group I self-splicing PIE sequence was modified to generate circular forms of the HIV-TAR and the high affinity region of the HIV-RRE (RBE). RNA products containing TAR and the RBE were purified from splicing reactions and demonstrated to be circular. The circular form of these sequences was shown to be resistant to nuclease degradation in cellular extracts. Gel shift assays demonstrate that the circular form of the RBE is specifically bound by a Rev derived peptide. These data suggest that PIE-circularization of RNA may be an effective way to express small stable RNAs designed for therapeutics (eg. decoys).
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PMID:Generation of nuclease resistant circular RNA decoys for HIV-Tat and HIV-Rev by autocatalytic splicing. 864 95

Human immunodeficiency virus type 1 (HIV-1) variants with resistance mutations in the reverse transcriptase (RT) gene appear during drug therapy with the nucleoside analogue 2',3'-dideoxy-3'-thiacytidine (3TC). These resistance mutations alter the methionine (Met) residue of the conserved YMDD motif, which is part of the catalytic core of the RT enzyme. Isoleucine (Ile) variants are initially observed, followed by the appearance and eventual outgrowth of viruses encoding valine (Val). Similar replication kinetics were measured for wild-type and 3TC-resistant HIV-1 viruses in tissue culture infections of a T cell line, but we measured reduced polymerase activity for the two mutant RT enzymes compared with the wild-type enzyme (Ile = 43% and Val = 67%). Gel analysis of the reverse transcription products revealed that both 3TC-resistant RT mutants produce significantly shorter cDNA molecules than the wild-type enzyme [Met (wt)>Val>Ile], indicating that 3TC-resistant RT polymerases are less processive enzymes. Interestingly, these enzyme defects were more pronounced under limiting dNTP concentrations and we therefore assayed virus replication in primary cells that contain relatively low dNTP levels. Under these conditions, we measured significantly reduced replication kinetics for the 3TC-resistant HIV-1 variants [Met (wt)>Val>Ile]. If the level of virus replication can be similarly reduced in 3TC-treated patients that develop drug-resistant HIV-1 variants, this may be of considerable clinical benefit.
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PMID:Reduced replication of 3TC-resistant HIV-1 variants in primary cells due to a processivity defect of the reverse transcriptase enzyme. 867 Sep 8


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