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

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

The functional exchangeability of the rev gene was assessed in transient transfection experiments by using in vitro-constructed rev and gag mutants of the following three primate lentiviruses: human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus from the African green monkey (SIV AGM). Cotransfection into SW480 cells of the rev and gag mutants derived from the DNA of each infectious virus resulted in the generation of progeny particles as determined by reverse transcriptase assay. rev gene mutants of HIV-2 and SIV AGM were also complemented by all gag mutants derived from the three viruses. In contrast, no evidence of complementation was obtained following cotransfection of the HIV-1 rev mutant and the gag mutant of HIV-2 or SIV AGM.
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PMID:Complementation of the rev gene mutation among human and simian lentiviruses. 218 9

A monoclonal antibody-based enzyme immunoassay (EIA) has been developed for detection of human T-cell lymphotropic virus type I (HTLV-I) core protein. The monoclonal antibody (clone 6.11) specifically recognizes the p19 gag gene-encoded protein of the virus. The EIA was over 100 times more sensitive than reverse transcriptase measurement and was capable of responding to less than 500 pg of whole-virus lysate. The assay exhibited type specificity in that HTLV-II antigens failed to produce a positive signal. In addition, a panel of other viruses demonstrated no antigenic cross-reactivity. These included herpesviruses, measles virus, human immunodeficiency viruses, and others. Viral p19 was followed during the course of density gradient ultracentrifugation in the presence of detergent, where it was noted to associate with viral membrane proteins. In comparison, reverse transcriptase activity localized in fractions of higher density containing envelope-free cores. Of clinical interest, the EIA was used to detect HTLV-I antigen in the viral cultures of patients with HTLV-I-associated myelopathies and from symptom-free individuals with proviral integration.
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PMID:Immunodetection of human T-cell lymphotropic virus type I core protein in biological samples by using a monoclonal antibody immunoassay. 219 Oct 15

A synthetic DNA fragment encoding a protease precursor of the human immunodeficiency virus type 2 (HIV2) was cloned and expressed in bacteria and yeast. A recombinant plasmid encoding a hybrid polypeptide consisting of human superoxide dismutase and an HIV2 protease precursor of 113 amino acids was constructed for regulated intracellular expression in bacteria. Induction of this plasmid produced an autoprocessed form of the retroviral enzyme possessing the correct molecular weight. Overexpression and secretion of the protease from yeast was achieved with an expression vector encoding the yeast pheromone alpha-factor signal/leader sequence fused to a protease precursor of 115 amino acids. Amino-terminal sequence analysis confirmed that the viral enzyme exported from yeast was correctly processed from its precursor by cleavage of the predicted Ala-Pro peptide bond located at the NH2 terminus of the protease in the pol open reading frame. No additional amino acid residues were required at the COOH terminus of the protease for this autoproteolytic event. The HIV2 protease expressed in bacteria and yeast was active in an in vitro assay when tested on the HIV1 polyprotein precursor, myristylated Pr53gag. Two synthetic peptides representing junction sequences in the HIV1 gag-pol precursor were used to assay purified HIV2 protease. The enzyme exhibited a kcat/KM of 23.2 min-1 mM-1 on the HIV1 matrix-capsid junction peptide and a kcat/KM of 71.4 min-1 mM-1 on the protease-reverse transcriptase junction peptide. These rates show that the HIV2 enzyme is efficient at hydrolyzing the HIV1 peptide junctions, revealing the analogous nature of the substrate specificities of the two enzymes.
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PMID:Recombinant HIV2 protease processes HIV1 Pr53gag and analogous junction peptides in vitro. 219 46

Hepatitis B virus DNA replicates via its own polymerase that also acts as reverse transcriptase (Summers and Mason, 1982). This enzyme is encoded by a 3.5 Kb mRNA transcript covering the whole genome. Since the same transcript also codes for the core protein, and since the core open reading frame (ORF) is located upstream of the pol ORF, it has been suggested that the polymerase is first produced as a core-pol fusion protein that subsequently undergoes cleavage. This is already known to be the case with retrovirus reverse transcriptase, for which a gag-pol fusion protein is made first and the latter protein is liberated by proteolytic cleavage. We investigated this problem using mutants that were modified at the translation initiation codon for the core and precore ORF. Our findings suggested that polymerase translation occurred from the internal AUG codon independently of core protein synthesis, and that obligatory production of the core-pol fusion protein is accordingly unlikely.
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PMID:Translation of hepatitis B virus DNA polymerase from the internal AUG codon, not from the upstream AUG codon for the core protein. 222 32

We have shown that 6D5 cells infected with the HIV-1 strain HTLV-III451 (6D5(451)) secreted viral envelope proteins gp160 and gp120 into the culture medium. Single cell cloning of 6D5(451) cells separated three distinct phenotypes. All clones secreted unprocessed env protein gp160 along with gp120. Only one phenotype produced infectious virus and contained normally processed gag proteins. The second phenotype was associated with nonproducer cells expressing only the env gene but no extracellular particles. The third phenotype synthesized Pr53gag but no reverse transcriptase, nor did it process the gag precursor. Only immature particles could be seen in the culture. Cells of the first and the third phenotypes produced two sizes of gp160, the normal and one with a small truncation at the C-terminus. Phenotype 2 only produced the smaller gp160. In all cases the gp160 that was secreted into the medium was the truncated molecule.
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PMID:Differential viral gene expression and its effect on the biological properties of the cell clones of an HIV-1-infected cell line. 235 62

We have made a computer-assisted search for homology among polymerases or putative polymerases of various viruses and a transposable element, the Drosophila copia-like element 17.6. The search revealed that the putative polymerase (second open reading frame) of the copia-like element 17.6 bears close resemblance in overall structural organization to the pol gene product of Moloney murine leukaemia virus (M-MuLV): they show significant homology to each other at both the N- and C-terminal portions, suggesting that the 17.6 putative polymerase carries two enzymatic activities, related to reverse transcriptase and DNA endonuclease. The putative polymerase of cauliflower mosaic virus (CaMV) shows striking homology with the putative polymerase of 17.6 over almost its entire length, but it lacks the DNA endonuclease-related sequence. Furthermore, it was shown that the N-terminal ends of the M-MuLV pol product and the CaMV and 17.6 putative polymerases exhibit strong sequence homology with the gag-specific protease (p15) of Rous sarcoma virus (RSV) as well as the amino acid sequence predicted from the gag/pol spacer sequence of human adult T-cell leukaemia virus (HTLV). These p15-related sequences contain a highly conserved stretch of amino acids which show a close similarity with sequences around the active site amino acids Asp-Thr-Gly of the acid protease family, suggesting that they have an activity similar to acid protease. On the basis of the alignment of reverse transcriptase-related sequences, a dendrogram representing phylogenetic relationships among all the viruses compared together with 17.6 was constructed and its evolutionary implication is discussed.
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PMID:Close structural resemblance between putative polymerase of a Drosophila transposable genetic element 17.6 and pol gene product of Moloney murine leukaemia virus. 240 86

Murine leukemia virus (MuLV) genome encodes a protease (Y. Yoshinaka, I. Katoh, T.D. Copeland, and S. Oroszlan (1985), Proc. Natl. Acad. Sci. USA 82, 1618-1622), which has been shown to cause maturation, specified as morphological conversion from "immature" to "mature" form of virus cores. To examine whether "immature" particles have infectivity or not, we constructed mutant DNAs with deletions in the protease region. The NIH/3T3 cells transfected with mutant DNAs produced "immature" particles, having immature morphology and containing Pr65gag, a polyprotein precursor of core proteins. The specific infectivity of the extracellularly released and purified particles was shown to be greatly reduced based on reverse transcriptase activity and protein content as compared with the "mature" particles obtained from wild-type DNA-transfected cells. The mutant genomes encoded functionally normal surface glycoprotein, gp70. These results strongly suggest that maturation of MuLV from "immature" to "mature" form of virus particles is indispensable to virus infectivity. The importance of processing of gag and pol, as well as transmembrane protein precursors by the viral protease is discussed.
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PMID:Murine leukemia virus maturation: protease region required for conversion from "immature" to "mature" core form and for virus infectivity. 241 Oct 50

A mutant of the Bryan high-titer strain of Rous sarcoma virus defective in reverse transcriptase is known as type alpha (BH-RSV alpha). BH-RSV alpha virion particles do not contain any polymerase-related proteins but they direct the synthesis of a normal sized Pr180 gag-pol polyprotein precursor in infected cells. Using a bioassay for polymerase gene function that is based on the requirement of viral replication for transformation of transfected chicken cells, we have localized the defect to the 2.5 kb EcoRI-KpnI DNA fragment containing more than 90% of the polymerase gene by comparison with the corresponding DNA fragment from the wild-type polymerase-positive BH-RSV, called type beta. In vitro recombination experiments with the polymerase gene of Schmidt-Ruppin RSV allowed us to map the defect to the 0.86 kb XbaI-BglII DNA fragment of the BH-RSV alpha polymerase. DNA sequence analysis of the entire polymerase gene of BH-RSV alpha and beta has revealed one point mutation that maps within that XbaI-BglII fragment and substitutes leucine in BH-RSV alpha for glutamine in the wild-type BH-RSV beta.
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PMID:Polymerase-defective mutant of the Bryan high-titer strain of Rous sarcoma virus. 242 Dec 48

We have found human DNA to contain a number of sequences related to simian sarcoma associated virus (SSAV). One of these sequences was isolated from a human genomic library. The molecular clone, termed S71, contains regions homologous to SSAV gag and pol fragments and SSAV LTR. Furthermore, hybridization experiments and DNA sequencing revealed distinct homologies to the reverse transcriptase coding region of several other retroviruses including baboon endogenous virus (BaEV) and murine leukemia viruses (MuLV) as well as retrovirus-like elements. Some sequence homology was also found with the C-type retrovirus-related multicopy human clone 4-1. S71 is present in only one copy per human genome equivalent and exhibits an EcoRI restriction fragment length polymorphism.
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PMID:Isolation of an SSAV-related endogenous sequence from human DNA. 243 42

Avarol and avarone are two antimitotic and antimutagenic agents that preferentially inhibit proliferation of T-cell leukemia lines in vitro. This report shows that these compounds have a dose-dependent inhibitory effect on the replication of the etiologic agent of acquired immune deficiency syndrome (AIDS), human T-lymphotropic retrovirus (HTLV-III)/lymphadenopathy-associated virus, in human H9 cells in vitro. Both compounds show a significant cytoprotective effect on HTLV-IIIB-infected H9 cells at concentrations as low as 0.1 microgram/ml (0.3 microM). Both avarone and avarol block in a dose-dependent manner the expression of the p24 and p17 gag proteins of HTLV-III in H9 cells after virus infection and block viral replication, as judged by approximately 80% inhibition of reverse transcriptase activity. These results strongly suggest that these compounds may prove to be useful in the treatment of patients with AIDS and AIDS-related complex.
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PMID:Inhibition of replication of the etiologic agent of acquired immune deficiency syndrome (human T-lymphotropic retrovirus/lymphadenopathy-associated virus) by avarol and avarone. 243 42


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