Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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The reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) is present in virions and infected cells as an heterodimer (p66/p51). A new class of potent and selective HIV-1 inhibitors, the tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO) derivatives, were found to exert their antiviral activity by interacting with monomeric HIV-1 RT (p66) in a way different from that of previously studied RT inhibitors such as azidothymidine 5'-triphosphate. Upon examination of the kinetic properties of the heterodimeric HIV-1 RT and its inhibition by TIBO compounds, a positive cooperativity between the subunits of the enzyme with regard to the 2'-deoxynucleoside 5'-triphosphates and the template/primer was observed. The cooperativity with respect to the template/primer may result from a progressive dimerization in the presence of increasing concentrations of the template/primer, a process referred to as polysteric linkage. Because the cooperativity of p66/p51 was abolished in the presence of TIBO, these compounds behave as allosteric inhibitors.
Mol Pharmacol 1992 Jan
PMID:Allosteric inhibition of human immunodeficiency virus type 1 reverse transcriptase by tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione compounds. 137 Jul 7

The in vitro fidelity of reverse transcriptase from human immunodeficiency virus type I (HIV-1 RT) upon copying an RNA template was measured using the phi Xam 16 reversion assay. A phi X174 sequence harboring the amber 16 codon was cloned into a transcription vector. RNA obtained from transcription by bacteriophage T7 RNA polymerase was used as a template for RNA-directed DNA synthesis by HIV-1 RT. An imbalance of dNTP concentrations during the reverse transcription step served to distinguish between errors that arose from the transcription step and errors from reverse transcription. The frequency of dGTP.U mismatches was determined to be 1/360, while dGTP.rA mismatches formed at a rate of 1/4600. These are 20-fold and sevenfold higher, respectively, than the error rates determined for the same sequence with a DNA template. Due to a high background of errors in the RNA template originating from the transcription step only upper limits for the frequency of three other mismatches can be given. The data indicate that the reverse transcription step of the HIV-1 replication cycle contributes significantly to the generation of mutant viruses.
J Mol Biol 1992 Feb 05
PMID:Fidelity of human immunodeficiency virus type I reverse transcriptase in copying natural RNA. 137 12

2',3'-Dideoxyuridine (ddU) is ineffective at controlling human immunodeficiency virus type 1 (HIV-1) infection in human T cells, because it is not biotransformed to the active 5'-triphosphate. The metabolic block resides in the poor substrate affinity of ddU for cellular nucleoside kinases. This problem cannot be overcome by supplying the preformed nucleotides, because such compounds are unable to penetrate cells. To circumvent the requirement of ddU for enzymic phosphorylation, we have prepared bis(pivaloyloxymethyl) 2',3'-dideoxyuridine 5'-monophosphate (piv2 ddUMP), as a potential membrane-permeable prodrug of ddUMP, and investigated its metabolism and anti-HIV activity in two human T cell lines, one with wild-type thymidine kinase activity (MT-4) and the other deficient in thymidine kinase activity (CEM-tk-). The 5'-mono-, di-, and triphosphates of ddU were formed in both cell lines after exposure to piv2-ddUMP. In contrast, phosphorylated metabolites were not observed in cells treated with ddU or ddUMP alone. piv2-ddUMP also reduced the cytopathic effects of HIV-1 in MT-4 cells (ED50, 4.75 microM) and inhibited virus production in culture fluid (ED50, 20 microM). In addition, piv2-ddUMP protected CEM-tk- cells from HIV-1 infection, as demonstrated by inhibition of intracellular p24 antigen levels (ED50, 3 microM) and reverse transcriptase activity in culture medium (Ed50, 2.5 microM). Based on these findings, we propose that the "masked nucleotide" strategy may make available for development nucleoside analogues hitherto considered inactive because of failure to undergo biotransformation to the corresponding 5'-monophosphates. Moreover, by circumventing metabolic dependency on nucleoside kinases, the strategy may overcome acquired resistance to nucleoside analogues caused by the loss or depletion of nucleoside kinases.
Mol Pharmacol 1992 Mar
PMID:Membrane-permeable dideoxyuridine 5'-monophosphate analogue inhibits human immunodeficiency virus infection. 137 82

Several newly discovered potent and selective non-nucleoside inhibitors of human immunodeficiency virus-1 reverse transcriptase (RT) are undergoing evaluation in clinical trials. We studied the potential for development of viral resistance to one of the prototype compounds, BI-RG-587, a dipyridodiazepinone derivative. Human immunodeficiency virus-1 resistant to BI-RG-587 emerged after only one cycle of in vitro infection in the presence of the drug. Resistant virus was cross-resistant to the non-nucleoside tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-thione derivative R82150 but remained susceptible to 2',3'-dideoxynucleosides and phosphonoformate. Both native (virion-associated) and recombinant RT derived from resistant virus were insensitive to BI-RG-587 and R82150. Nucleotide sequence analysis of multiple drug-resistant and -sensitive recombinant RT clones identified a single predicted amino acid change common to all resistant clones (tyrosine-181----cysteine). These studies suggest that the viral resistance to non-nucleoside RT inhibitors may develop in vivo. This possibility should be carefully monitored in clinical trials of these compounds.
Mol Pharmacol 1992 Mar
PMID:In vitro selection and molecular characterization of human immunodeficiency virus-1 resistant to non-nucleoside inhibitors of reverse transcriptase. 137 83

The envelope protein of the feline immunodeficiency virus (FIV) was analyzed using several epitope prediction programs based on profiles of hydrophilicity, antigenicity, and probability of residues to lie on the protein surface. Tentative homologies with the immunodominant epitope sites in simian virus (SIV) or human immunodeficiency virus (HIV) such as the V3 loop, the site of cleavage between surface envelope protein (SU) and transmembrane envelope protein (TM), and sites of N-glycosylation were thus identified. Five peptides corresponding to potential epitopes were synthesized. Four out of five peptides (P99, P100, P101, P103) were from the FIV surface envelope protein (SU). The last one (P102) was from the FIV transmembrane envelope protein TM. Three of these peptides (P99, P100, and P102) were recognized in ELISA by almost all the sera from infected cats. The peptide from TM (102) was recognized by sera from both naturally infected and inoculated cats, whereas peptides P99 and P100 (from SU) were recognized mainly by sera from naturally infected cats. On the basis of these results we propose that peptides P99, and P100 from SU and P102 from TM constitute epitopes on the FIV env protein.
Mol Immunol 1992 May
PMID:Localisation of three epitopes of the env protein of feline immunodeficiency virus. 137 40

Recently, several classes of compounds have been shown to be potent, selective, and specific inhibitors of human immunodeficiency virus type 1 replication in vitro. These include the tetrahydroimidazo[4,5,1-jk][1,4]-benzodiazepin-2(1H)-one and -thione (TIBO) and the 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) derivatives. Both the TIBO and HEPT derivatives specifically inhibit human immunodeficiency virus type 1 reverse transcriptase (RT). From a comparative study of the characteristics of RT inhibition by TIBO and HEPT, and from the competition between TIBO and HEPT for RT inhibition, we infer that both classes of compounds, although structurally unrelated, are targeted at the same site of the enzyme. Detailed functional and kinetic analyses indicate that this target site is functionally and possibly also spatially related to the substrate binding site.
Mol Pharmacol 1992 May
PMID:Common features in the interaction of tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione and 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives with the human immunodeficiency virus type 1 reverse transcriptase. 137 20

Primer tRNA regions involved in the interactions between human immunodeficiency virus reverse transcriptase (HIV RT) and tRNA(Lys) were studied by digestion of primer with pancreatic ribonuclease in the presence or absence of HIV RT. The acceptor stem of tRNA(Lys) is not noticeably protected against nuclease action in the presence of HIV RT, while this enzyme clearly protects part of the anticodon and dihydrouridine loops of tRNA(Lys). The acceptor stem of primer tRNA was digested by RNase A only in the presence of the retroviral enzyme, suggesting a partial destabilization of this region by the HIV RT. Synthetic oligoribonucleotides, corresponding to the anticodon and the dihydrouridine loops, inhibited strongly reverse transcription, confirming the strong interaction of these tRNA regions with the enzyme.
J Mol Biol 1992 Jul 05
PMID:Preferential interaction of human immunodeficiency virus reverse transcriptase with two regions of primer tRNA(Lys) as evidenced by footprinting studies and inhibition with synthetic oligoribonucleotides. 137 51

Recent evidence suggests that the human immunodeficiency virus type 1 (HIV) trans-activator gene (tat) has transforming properties and may be a causative factor in the development of certain types of cancers, in particular Kaposi's sarcoma (i.e., Vogel J. et al. Nature 335:606-611, 1988). To help elucidate the potential role or roles of the HIV tat gene in neoplastic transformation, cell lines were constructed that constitutively express a functional tat gene product. HeLa cells were coelectroporated with two plasmids, one containing the HIV tat gene in an expression cassette and another containing the dominant selectable marker gene xanthine guanine phosphoribosyltransferase (XGPRT). After XGPRT selection, single-cell clones that expressed a functional tat protein were identified by measuring chloramphenicol acetyltransferase (CAT) activity after electroporating a plasmid containing the CAT gene transcriptionally controlled by HIV trans-activation-responsive region (tar). Phenotypic alterations resulting from the expression of tat were then determined. Control cells and tat-expressing cells grew at similar rates in culture. However, when grown as tumors in nude mice, tat-expressing cells produced a lower percentage of tumors, and the tumors that were produced either regressed, stopped growing, or grew at a very reduced rate compared with cells not expressing tat. These differences may have resulted from a tat-associated reduction in neovascularization in the tumors. A comparison of total cellular proteins by two-dimensional polyacrylamide gel electrophoresis indicated only one reproducible alteration in a polypeptide of approximately 44 kDa and pl of approximately 6.2 associated with tat expression. These cells may be very useful in future in vitro and in vivo studies designed to examine the effects of HIV tat on endothelial and vascular smooth-muscle cells and the role of tat in the etiology of Kaposi's sarcoma.
Mol Carcinog 1992
PMID:Alterations in tumor angiogenesis associated with stable expression of the HIV tat gene. 137 15

We have investigated the feasibility and significance of subtyping of human immunodeficiency virus (HIV) isolates with monoclonal antibodies (mAb) raised against the core proteins of HIV. A panel of 37 mAb tested for reactivity with HIV1 oligopeptides was used to analyse the antigenic relatedness among 14 HIV isolates which included 12 isolates of HIV1 from different geographical origins and 2 isolates of HIV2. Three out of these 37 mAb reacted with conserved epitopes expressed by all 14 HIV isolates tested. These reagents which included 2 mAb reacting with the 285-310 amino acid sequence of p25 and 1 mAb reacting with an epitope of p25 not mapped by the peptides' approach, also reacted with a non-human primate lentivirus. Five mAb reacting either with the 11-25 or 121-132 amino acid sequences of p17 or the 302-320 amino acid sequence of p25 reacted with strain-specific epitopes. The other 29 mAb reacted with polymorphic epitopes and thereby define subfamily and subtype-specific markers.
Mol Immunol 1992 Oct
PMID:Subtyping of human immunodeficiency virus isolates with a panel of monoclonal antibodies: identification of conserved and divergent epitopes on p17 and p25 core proteins. 138 19

Determination of the B-cell epitopes of the nef molecule encoded by the human immunodeficiency virus type 1 (HIV-1) was undertaken using a set of six synthetic peptides. Sequences that were both antigenic and immunogenic and stimulated the production of antibodies recognizing the full length molecule, were considered as B-cell epitopes. Two peptidic sequences were antigenic both in rodents (mice and rats) and in non-human primates (chimpanzee). They were located in the regions 45-69 and 176-206 of the nef molecule. Two additional antigenic sequences were determined, one in chimpanzees, region 79-94, and the second in rodents, region 148-161. Immunogenicity was investigated in the rodents. Only the 45-69 and 176-206 sequences were immunogenic, and specific antibodies present in the sera of the immunized animals reacted with the nef protein. Therefore, each of these two sequences could be considered as containing at least one B-cell epitope. The fine epitopic specificity was determined using subfragments of these two sequences and it was shown that the antigenic determinants were contained in the C-terminal region of each sequence overlapping with the T-cell epitopes. These results raised the importance of vicinity of B- and T-cell determinants and their immunogenicity.
Mol Immunol 1992 Nov
PMID:Determination of B-cell epitopes of nef HIV-I protein: immunogenicity related to their structure. 138 94


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