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

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human immunodeficiency virus type 1-specific Vpu protein is a small integral membrane phosphoprotein that induces degradation of the virus receptor CD4 in the endoplasmic reticulum and, independently, increases the release of progeny virions from infected cells. To address the importance of Vpu for virus replication in primary human cells such as peripheral blood mononuclear cells (PBMC) and monocyte-derived macrophages (MDM), we used three different sets of monocyte-tropic molecular clones of human immunodeficiency virus type 1: a primary isolate, AD8+, and two chimeric variants of the T-cell-tropic isolate NL4-3 carrying the env determinants of either AD8+ or SF162 monocyte-tropic primary isolates. Isogenic variants of these chimeric viruses were constructed to express either wild-type Vpu or various mutants of Vpu. The effects of these mutations in the vpu gene on virus particle secretion from infected MDM or PBMC were assessed by determination of the release of virion-associated reverse transcriptase into culture supernatants, Western blot (immunoblot) analysis of pelleted virions, and steady-state or pulse-chase metabolic labeling. Wild-type Vpu increased virus release four- to sixfold in MDM and two- to threefold in PBMC, while nonphosphorylated Vpu and a C-terminal truncation mutant of Vpu were partially active on virus release in primary cells. These results demonstrate that Vpu regulates virus release in primary lymphocyte and macrophage cultures in a similar manner and to a similar extent to those previously observed in HeLa cells or CD4+ T-cell lines. Thus, our findings provide evidence that Vpu functions in a variety of human cells, both primary cells and continuous cell lines, and mutations in Vpu affect its biological activity independent of the cell type and virus isolate used.
...
PMID:Augmentation of virus secretion by the human immunodeficiency virus type 1 Vpu protein is cell type independent and occurs in cultured human primary macrophages and lymphocytes. 749 79

Aurothioglucose and aurothiomalate have anti-HIV-1 activity in vitro. Antiviral activity requires the formation of a reactive intermediate with a molar equivalent amount of a thiol ligand. This activates gold(I) ligand exchange between the reactive species bis(thiolato)gold(I) and acidic thiol groups exposed on the surface of proteins. Bis(thioglucose)gold(I) (bisAuTG) which is formed by the reaction of molar equivalent amounts of aurothioglucose and 1-thio-beta-D-glucose completely protected MT-4 and CEM cells against HIV-1NL4-3-induced cytopathogenicity. Although bisAuTG is an inhibitor of human immunodeficiency virus-1 (HIV-1) reverse transcriptase in a cell-free assay, its antiviral effect is due to modification of a surface component of the virion. The HIV-1 strain NL4-3 is 200-fold more sensitive to inhibition of infectivity by bisAuTG than are the strains MN, RF, and SF-2. HIV-1NL4-3 has a unique cysteine residue close to the amino terminus of its gp41 envelope glycoprotein (residue 532 of gp160) which we hypothesize is the target of bisAuTG binding. Mutation of that residue alters HIV-1NL4-3 infectivity and dominantly suppresses virus assembly when coexpressed with the wild-type NL4-3 genome. We show that bisAuTG treatment releases gp120 from the surface of cells expressing wild-type HIV-1NL4-3 envelope glycoprotein, but it does not release gp120 if Cys532 is mutationally altered to Ala. Thus, the antiviral effect of bisAuTG on HIV-1NL4-3 is due to an effect on the association of gp120 with gp41.
...
PMID:Aurothiolates inhibit HIV-1 infectivity by gold(I) ligand exchange with a component of the virion surface. 842 3

We have evaluated the susceptibility to human immunodeficiency virus (HIV)-1 infection of in vitro grown megakaryopoietic progenitors/precursors and maturing megakaryocytes (MKs), based on the following approach: (1) human hematopoietic progenitor cells (HPCs), stringently purified from peripheral blood and grown in serum-free liquid suspension culture supplemented with thrombopoietin (Tpo), generated a relatively large number of >/= 98% to 99% pure megakaryocytic precursors and then mature-terminal MKs; (2) at different days of culture (ie, 0, 5, 8, 10) the cells were inoculated with 0.1 to 1.0 multiplicity of infection (m.o.i.) of the lymphotropic NL4-3 or 0.1 m.o.i. of the monocytotropic BaL-1 HIV-1 strain; (3) finally, the presence of viral mRNA and proteins was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR)/in situ hybridization and antigen capture assays, respectively, on day 2 to 12 of culture. MKs derived from day 0 and day 5 BaL-1-challenged cells do not support viral replication as assessed by p24 enzyme-linked immunosorbent assay (ELISA) and RT-PCR. On the contrary, HIV transcripts and proteins were clearly detected in all NL4-3 infection experiments by RT-PCR and p24 assay, respectively, with the highest viral expression in day 5 to 8 challenged MKs. In situ hibridization studies indicate that the percentage of HIV+ MKs varies from at least 1% and 5% for day 0 and day 5 infected cells, respectively. Production of an infectious viral progeny, evaluated by the capability of culture supernatants from day 5 NL4-3-challenged MKs to infect C8166 T-lymphoblastoid cell line, was consistently observed (viral titer, approximately 5 x 10(3) tissue culture infectious dose50/mL/10(6) cells). Exposure of MKs to saturating concentration of anti-CD4 OKT4A monoclonal antibody (MoAb), which recognizes the CD4 region binding with the gp120 envelope glycoprotein, markedly inhibited HIV infection, as indicated by a reduction of p24 content in the supernatants: because the inhibitory effect was incomplete, it is apparent that the infection is only partially CD4-dependent, suggesting that an alternative mechanism of viral entry may exist. Morphologic analysis of day 12 MKs derived from HPCs infected at day 0 showed an impaired megakaryocytic differentiation/maturation: the percentage of mature MKs was markedly reduced, in that approximately 80% of cells showed only one nuclear lobe and a pale cytoplasm with few granules. Conversely, megakaryocytic precursors challenged at day 5 to 8 generated fully mature day 10 to 12 MKs showing multiple nuclear segmentation. Thus, the inhibitory effect of HIV on the megakaryopoietic gene program relates to the differentiation stage of cells subjected to the viral challenge. Finally, HPCs treated with 20 or 200 ng/mL of recombinant Tat protein, analyzed at different days of culture, showed an impaired megakaryocytopoiesis comparable to that observed in HIV-infected cells, thus suggesting that Tat is a major mediator in the above described phenomena. These results shed light on the pathogenesis of HIV-related thrombocytopenia; furthermore, they provide a model to investigate the effects of HIV on megakaryocytic differentiation and function.
...
PMID:Productive human immunodeficiency virus-1 infection of purified megakaryocytic progenitors/precursors and maturing megakaryocytes. 945 52

Twenty-two new alkenyldiarylmethanes (ADAMs) were synthesized and evaluated for inhibition of HIV-1 replication. The most potent compound proved to be methyl 3',3"-dichloro-4',4"-dimethoxy-5', 5"-bis(methoxycarbonyl)-6,6-diphenyl-5-hexenoate (ADAM II), which displayed an EC50 of 13 nM for inhibition of the cytopathic effect of HIV-1RF in CEM-SS cells. ADAM II inhibited HIV-1 reverse transcriptase with an IC50 of 0.3 microM but was inactive as an inhibitor of HIV-1 attachment/fusion to cells, protease, integrase, and the nucleocapsid protein. Molecular target-based and cell-based assays revealed that ADAM II acted biologically as a nonnucleoside reverse transcriptase inhibitor (NNRTI). ADAM II inhibited replication of a wide variety of laboratory, clinical, and clade-representative isolates of HIV-1 in T cell lines and cultures of peripheral blood mononuclear cells or monocyte/macrophages. Mutations that conferred resistance to ADAM II clustered at residues 101, 103, 108, 139, 179, 181, and 188, which line the nonnucleoside binding pocket of HIV-1 reverse transcriptase. However, HIV-1 NL4-3 strain expressing a mutation at residue 100 of reverse transcriptase, and an AZT-resistant virus, displayed increased sensitivity to ADAM II. Thus, ADAM II could serve as an adjunct therapy to AZT and NNRTIs that select for L100I resistance mutations.
...
PMID:New alkenyldiarylmethanes with enhanced potencies as anti-HIV agents which act as non-nucleoside reverse transcriptase inhibitors. 962 49

Oral administration of 2'-deoxy-3'-oxa-4'-thiocytidine (BCH-10652), a nucleoside analog structurally similar to lamivudine (3TC), caused dose-dependent inhibition of viral replication in SCID-hu Thy/Liv mice infected with human immunodeficiency virus type 1 NL4-3 and with an NL4-3 clone containing the M184V mutation in reverse transcriptase that confers resistance to 3TC. These experiments demonstrate the utility of this mouse model for evaluating drug resistance and for performing direct comparisons between antiviral compounds in vivo.
...
PMID:Antiviral activity of 2'-deoxy-3'-oxa-4'-thiocytidine (BCH-10652) against lamivudine-resistant human immunodeficiency virus type 1 in SCID-hu Thy/Liv mice. 1068 60

Combinations of anti-HIV agents including one or two reverse transcriptase inhibitors with a protease inhibitor are potent and effective. However, toxicities, costs and the emergence of drug-resistant organisms have compromised their long-term efficacy in people. A next, likely, target for anti-HIV therapy is HIV-1 integrase. Viral integration, catalyzed by integrase, is absolutely required for HIV replication. L-chicoric acid is a potent and selective inhibitor of HIV-1 integrase that also inhibits HIV-1 replication in cell culture. As a first step in understanding the potential role for integrase inhibitors in clinical medicine, the activities of L-chicoric acid alone and in combination with 2', 3'-dideoxycytidine, zidovudine, and a protease inhibitor, nelfinavir, were tested in vitro against molecular clones of HIV-1 resistant to reverse transcriptase inhibitors. L-chicoric acid was equally effective against a wild-type clone of HIV-1, HIV(NL4-3), or against HIV-1 resistant to either zidovudine or dideoxycytidine. L-chicoric acid was largely synergistic with zidovudine and synergistic with both dideoxycytidine and nelfinavir.
...
PMID:Combinations of reverse transcriptase, protease, and integrase inhibitors can be synergistic in vitro against drug-sensitive and RT inhibitor-resistant molecular clones of HIV-1. 1086 60

Viral-based vectors can provide an efficient delivery mechanism for stable expression of antisense RNA. To enhance and propagate the antiviral effect of antisense RNA, two novel human immunodeficiency virus type 1 (HIV-1)-based vector DNAs, designated as pMAG7 and pMAG19, were constructed which contained HIV-1 cis-acting packaging elements and produced multigenic HIV-1 antisense RNA that could target the entire pol, env, vif, vpu, vpr, rev, and tat and portions of gag and nef. The two DNAs were identical except that pMAG19 had additional gag coding sequences. Cotransfection of pMAG DNA and infectious, cloned HIV-1 DNA in 293 cells inhibited virus production (81%-98% reduction in reverse transcriptase activity) of various T cell-tropic and macrophage-tropic clade B isolates, such as NL4-3, YU-2, and JR-CSF. In addition, virion-associated pMAG antisense RNA was detected in residual virus particles produced by pNL4-3 in the presence of pMAG7 DNA, and the antisense sequences were stably transferred by infection of 174 x CEM cells. The results suggest that pMAG DNA may confer broad protection against HIV-1 by reducing initial virus burden due to antisense RNA and subsequent virus spread by propagation of antisense sequences along with wild-type virus.
...
PMID:Inhibition of human immunodeficiency virus type 1 by packageable, multigenic antisense RNA. 1090 51

Polyanionic dendrimers were synthesized and evaluated for their antiviral effects. Phenyldicarboxylic acid (BRI6195) and naphthyldisulfonic acid (BRI2923) dendrimers were found to inhibit the replication of human immunodeficiency virus type 1 (HIV-1; strain III(B)) in MT-4 cells at a EC(50) of 0.1 and 0.3 microg/ml, respectively. The dendrimers were not toxic to MT-4 cells up to the highest concentrations tested (250 microg/ml). These compounds were also effective against various other HIV-1 strains, including clinical isolates, HIV-2 strains, simian immunodeficiency virus (SIV, strain MAC(251)), and HIV-1 strains that were resistant to reverse transcriptase inhibitors. HIV strains containing mutations in the envelope glycoprotein gp120 (engendering resistance to known adsorption inhibitors) displayed reduced sensitivity to the dendrimers. The compounds inhibited the binding of wild-type virus and recombinant virus (containing wild-type gp120) to MT-4 cells at concentrations comparable to those that inhibited the replication of HIV-1(III(B)) in these cells. Cellular uptake studies indicated that BRI2923, but not BRI6195, permeates into MT-4 and CEM cells. Accordingly, the naphtyldisulfonic acid dendrimer (BRI2923) proved able to inhibit later steps of the replication cycle of HIV, i.e., reverse transcriptase and integrase. NL4.3 strains resistant to BRI2923 were selected after passage of the virus in the presence of increasing concentrations of BRI2923. The virus mutants showed 15-fold reduced sensitivity to BRI2923 and cross-resistance to known adsorption inhibitors. However, these virus mutants were not cross-resistant to reverse transcriptase inhibitors or protease inhibitors. We identified several mutations in the envelope glycoprotein gp120 gene (i.e., V2, V3, and C3, V4, and C4 regions) of the BRI2923-resistant NL4.3 strains that were not present in the wild-type NL4.3 strain, whereas no mutations were found in the reverse transcriptase or integrase genes.
...
PMID:Polyanionic (i.e., polysulfonate) dendrimers can inhibit the replication of human immunodeficiency virus by interfering with both virus adsorption and later steps (reverse transcriptase/integrase) in the virus replicative cycle. 1104 59

Human immunodeficiency virus type 1 (HIV-1) variants resistant to protease (PR) and reverse transcriptase (RT) inhibitors may display impaired infectivity and replication capacity. The individual contributions of mutated HIV-1 PR and RT to infectivity, replication, RT activity, and protein maturation (herein referred to as "fitness") in recombinant viruses were investigated by separately cloning PR, RT, and PR-RT cassettes from drug-resistant mutant viral isolates into the wild-type NL4-3 background. Both mutant PR and RT contributed to measurable deficits in fitness of viral constructs. In peripheral blood mononuclear cells, replication rates (means +/- standard deviations) of RT recombinants were 72.5% +/- 27.3% and replication rates of PR recombinants were 60.5% +/- 33.6% of the rates of NL4-3. PR mutant deficits were enhanced in CEM T cells, with relative replication rates of PR recombinants decreasing to 15.8% +/- 23.5% of NL4-3 replication rates. Cloning of the cognate RT improved fitness of some PR mutant clones. For a multidrug-resistant virus transmitted through sexual contact, RT constructs displayed a marked infectivity and replication deficit and diminished packaging of Pol proteins (RT content in virions diminished by 56.3% +/- 10.7%, and integrase content diminished by 23.3% +/- 18.4%), a novel mechanism for a decreased-fitness phenotype. Despite the identified impairment of recombinant clones, fitness of two of the three drug-resistant isolates was comparable to that of wild-type, susceptible viruses, suggestive of extensive compensation by genomic regions away from PR and RT. Only limited reversion of mutated positions to wild-type amino acids was observed for the native isolates over 100 viral replication cycles in the absence of drug selective pressure. These data underscore the complex relationship between PR and RT adaptive changes and viral evolution in antiretroviral drug-resistant HIV-1.
...
PMID:Individual contributions of mutant protease and reverse transcriptase to viral infectivity, replication, and protein maturation of antiretroviral drug-resistant human immunodeficiency virus type 1. 1123 55

We previously reported that two insertions of 15 amino acids in the beta3-beta4 hairpin loop of fingers subdomain of HIV-1(NL4-3) RT confer an increased polymerase processivity. The processivity of human immunodeficiency virus (HIV) reverse transcriptase (RT) is thought to influence the fidelity of HIV-1 RT, which tends to create errors at template sites with high termination probability. Employing the two insertion variants of HIV-1 RT (FE20 and FE103), we examined the relationship between processivity, overall fidelity and error specificity. Although the overall mutation rate was unaffected by increased processivity, one of the mutants, FE103, generated significantly fewer frameshift errors. The other mutant, FE20, generated errors at hotspots not previously observed for HIV-1 RT. Our results indicate that an increase in the polymerase processivity of HIV-1 RT does not necessarily result in a decreased mutation rate and confirm that changes in processivity alter the sequence context in which the errors are made. Furthermore, our results also reveal that the mutation frequency obtained via in vitro gap-filling reactions with wild-type HIV-1(NL4-3) RT is only 2-fold higher than that obtained via a single cycle infection assay using the same, wild-type HIV-1(NL4-3) RT sequence as part of the helper pol function [Mansky and Temin: J Virol 69:5087-5094;1995].
...
PMID:The effect of increased processivity on overall fidelity of human immunodeficiency virus type 1 reverse transcriptase. 1128 51


1 2 3 4 5 Next >>

---