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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Influenza B/LEE/40, B/Rome/1/67, B/Hong Kong/8/73, and B/Victoria/98926/70 viruses have a similar polypeptide composition as analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. These viruses are composed of six or seven polypeptides, depending on whether one or two high-molecular-weight polypeptides are resolved, ranging in molecular weights from 27,000 to 90,400. Three of these polypeptides, namely the heavy and light hemagglutinin chains and the neuraminidase, have attached carbohydrate. Highly purified influenza B/LEE/40 and B/Rome/1/67 virus preparations have RNA-dependent RNA polymerase activity equivalent to the incorporation of 100 and 30 pmol, respectively, of (3)H-UMP per mg of virus protein per h at 37 C, which is demonstrated only in detergent-treated virus suspensions. However, no RNA-dependent DNA polymerase enzyme activity was detected in the two viruses although virus suspensions were "activated" by heat, alpha-chymotrypsin, and detergents. Other enzymatic activities were associated with purified preparations of influenza B virus and were attributed to minor contamination of virus with host cell enzymes. Thus, nucleoside and deoxynucleoside phosphohydrolase enzymes were active in the absence of detergents and catalyzed the release of 1,200 and 1,800 nmol of P(i) per mg of virus protein in 30 min at 37 C from ATP and dATP substrates. Thin-layer chromatography indicated that the products of the phosphohydrolase enzymes of influenza B/LEE/40 were mainly nucleoside diphosphate and monophosphate. The latter enzymes were tightly bound to influenza B/LEE/40 virus and could not be removed completely by repeated centrifugation, including centrifugation of the virus to equilibrium in density gradients of 25 to 40% (wt/vol) cesium chloride. A low degree of RNase (approximately 0.01 mug% contamination) and phosphatase (10-30 nmol of P(i) released per mg of virus protein per 30 min) activity was detected in some, but not all, influenza B/LEE/40 virus preparations.
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PMID:Polypeptide composition of Influenza B viruses and enzymes associated with the purified virus particles. 435 55

Two paramyxovirus isolates recovered from the peripheral blood leukocytes of a patient with subacute sclerosing panencephalitis were characterized by biological, immunological, and molecular techniques. Both virus isolates possessed neuraminidase activity but demonstrated reduced hemagglutination potential. Neutralization titrations showed that the viruses were clearly related to, but were distinct from, simian virus 5. Characterization of purified virus preparations by SDS-PAGE showed that the structural polypeptides of the viruses were similar to those of simian virus 5, but distinct differences were noted as well. In addition, the virus isolates were found to differ from one another, particularly with regard to the major putative transcriptase protein (L).
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PMID:Characterization of nonmeasles paramyxovirus isolates from a patient with subacute sclerosing panencephalitis. 733 93

Influenza viruses are spherical, about 1000 A in diameter, and consist of an as yet undefined central structure containing the eight negative-sense RNA molecules of the genome (1) in association with the transcriptase required for mRNA synthesis, an abundant nucleoprotein, and an equally abundant matrix protein. This core is surrounded by a membrane derived from the cell surface in a budding process by which newly formed viruses are released from the infected cell. During infection cell membranes are modified by the incorporation of newly synthesized virus membrane proteins, and the finally released viruses contain exclusively two different types of virus-specified glycoprotein, hemagglutinin and neuraminidase, and a proton channel protein, M2. All three of these molecules have been studied extensively, particularly the glycoproteins, and in this paper information on their structures and functions will be summarized and related to modifications in cellular membranes that occur during virus infection.
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PMID:Influenza viruses and cell membranes. 755 5

Infective trypomastigote forms of Trypanosoma cruzi express an oligomeric trans-sialidase that contains a long stretch of 12-amino-acid repeats at the C terminus, while the insect epimastigote forms having a monomeric trans-sialidase without repeats. Here we show that messenger RNAs encoding trans-sialidases containing the repeats are not present in epimastigotes but are abundant in trypomastigotes. In contrast, mRNA species encoding the conserved N-terminal domain are detected in epimastigotes. A cDNA clone derived from epimastigote mRNA was isolated and characterized. It predicts a repeat-minus amino-acid sequence that has 84% identity to the conserved N-terminal domain of trypomastigote trans-sialidase, and contains some of the necessary amino acids for the catalytic activity, as shown by fusion experiments. Transcripts corresponding to this clone were detected in epimastigotes and in trypomastigotes by reverse-transcriptase and polymerase chain reaction. In addition, the lack of repeats is not due to RNA processing because the corresponding gene without repeats was amplified from the parasite DNA. These results suggest that a distinct set of genes encode the repeat-minus trans-sialidase, and only these trans-sialidase genes are expressed in epimastigote forms.
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PMID:Trypanosoma cruzi trans-sialidase gene lacking C-terminal repeats and expressed in epimastigote forms. 763 18

When mouse-adapted influenza virus A/PR/8/34 (A/PR8) (10 PFU/cell) was adsorbed to Madin-Darby canine kidney (MDCK) cells at 4 degrees C for 1 h and incubated at 37 degrees C, release of the virus from the cells was detected in the medium from 4 h after incubation and reached to plateau at 8 h. However, 5,7,4'-trihydroxy-8-methoxyflavone (F36) from the roots of Scutellaria baicalensis significantly reduced this single-cycle replication of A/PR8 from 4 h to 12 h after incubation by dose-dependent manner and the dose which decrease the virus titer one tenth was 11 microM. F36 (50 microM) did not inhibit the adsorption of A/PR8 to MDCK cells, but reduced release of the virus in the medium, when it was added at 0 or 2 h after the incubation. The cell-associated virus determined by sialidase activity was also reduced by F36 treatment at 0 or 2 h. F36 also inhibited the fusion of A/PR8 with liposomes containing bovine brain mixed gangliosides at pH 5.0. However, F36 little affected on the elongation activity of the viral RNA-dependent RNA polymerase in vitro. These results suggest that F36 reduces the replication of A/PR8 by inhibiting the fusion of the virus with endosome/lysosome membrane which occurs at early stage of virus infection cycle. Whereas, when F36 was added to the MDCK cells infected with A/PR8 at 3 or 4 h after incubation, release of the virus in the medium was reduced but the cell-associated virus was increased in comparison with control.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mode of action of the anti-influenza virus activity of plant flavonoid, 5,7,4'-trihydroxy-8-methoxyflavone, from the roots of Scutellaria baicalensis. 774 18

We investigated effects of isoscutellarein-8-methylether (5,7,4'-trihydroxy-8-methoxyflavone, F36) from the roots of Scutellaria baicalensis on the single-cycle replication of mouse-adapted influenza viruses A/Guizhou/54/89 (H3N2 subtype) and B/Ibaraki/2/85 in Madin-Darby canine kidney (MDCK) cells. The agent suppressed replication of these viruses from 6 to 12 h after incubation in a dose-dependent manner by 50% at 20 microM and 90% at 40 microM, respectively. F36 (50 microM) reduced the release of B/Ibaraki virus in the medium by 90-93% when it was added to the MDCK cells at 0 to 4 h after incubation. The cell-associated virus determined by sialidase activity was also reduced by the treatment at 0 to 4 h. F36 (120 microM) inhibited the low pH-dependent membrane fusion of both the viruses with the liposome containing mixed gangliosides from bovine brain. However, the agent little affected the hemagglutination and RNA-dependent RNA polymerase activities of these viruses in vitro. These results suggest that F36 inhibits the replication of A/Guizhou and B/Ibaraki viruses at least partly by inhibiting the fusion of viral envelopes with the endosome/lysosome membrane which occurs at the early stage of the virus infection cycle. F36 (0.5 mg/kg) showed no antiviral activity against A/Guizhou and B/Ibaraki viruses in mice when administered intranasally 5 min prior to virus inoculation, whereas it significantly inhibited their proliferation in the mouse lung when administered intranasally 7 times (total 3.5 mg/kg) from 18 h before to 54 h after virus infection.
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PMID:Antiviral activity of plant flavonoid, 5,7,4'-trihydroxy-8-methoxyflavone, from the roots of Scutellaria baicalensis against influenza A (H3N2) and B viruses. 774 1

Reverse transcriptase (RT) PCR assays have been developed to improve the diagnosis of avian influenza A. RT-PCR using primers complementary to a conserved region of the matrix protein was assessed as being suitable for the detection of influenza A virus RNA from poultry as well as from pigs, horses and humans, regardless of the haemagglutinin (HA) and neuraminidase (NA) subtype. Therefore, this RT-PCR is a valuable tool to confirm the initial diagnosis of any influenza A infection. As a second approach, experiments were performed to identify the HA gene encoding the post-translational cleavage site of potentially highly pathogenic AIV isolates by RT-PCR. The principal aim was to design one universal primer pair for each virus subtype, H5 and H7, respectively, which allows the detection of all strain variants using only one consistent method. To realize this objective, it was necessary to develop 'wobble' primers. AIV RNAs from seven H5 and 11 H7 subtype viruses included in the investigations were specifically recognized by RT-PCR using these primers. This method therefore provides a rapid, subtype-specific diagnosis and subsequent sequencing of H5 and H7 avian influenza viruses.
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PMID:Type- and subtype-specific RT-PCR assays for avian influenza A viruses (AIV). 1086 Nov 98

A model DNA microarray has been prepared and shown to facilitate typing and subtyping of human influenza A and B viruses. Reverse transcriptase PCR was used to prepare cDNAs encoding approximately 500-bp influenza virus gene fragments, which were then cloned, sequenced, reamplified, and spotted to form a glass-bound microarray. These target DNAs included multiple fragments of the hemagglutinin, neuraminidase, and matrix protein genes. Cy3- or Cy5-labeled fluorescent probes were then hybridized to these target DNAs, and the arrays were scanned to determine the probe binding site(s). The hybridization pattern agreed perfectly with the known grid location of each target, and the signal-to-background ratio varied from 5 to 30. No cross-hybridization could be detected beyond that expected from the limited degree of sequence overlap between different probes and targets. At least 100 to 150 bp of homology was required for hybridization under the conditions used in this study. Combinations of Cy3- and Cy5-labeled DNAs can also be hybridized to the same chip, permitting further differentiation of amplified molecules in complex mixtures. In a more realistic test of the technology, several sets of multiplex PCR primers that collectively target influenza A and B virus strains were identified and were used to type and subtype several previously unsequenced influenza virus isolates. The results show that DNA microarray technology provides a useful supplement to PCR-based diagnostic methods.
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PMID:Typing and subtyping influenza virus using DNA microarrays and multiplex reverse transcriptase PCR. 1115 30

Influenza is worldwide one of the deadliest infectious diseases. Lethal influenza mutants can unpredictably arise, as in the 1918 pandemic, or in the 1997 Hong Kong influenza outbreak. Vaccines are today the only protective prophylactic agents, and development of potent new anti-influenza drugs of therapeutic effectiveness appears urgent. It is the aim of the present review, to summarize and discuss the different investigational approaches to this goal. In Medline- and several internet virology database-searches, numerous citations were compiled, and selected according to their relevance to the different topics discussed. The antiviral agents are classified according to their target in the viral replication cycle: proteolytic activation of haemagglutinin, attachment of the virus to specific cell-surface receptors, endocytosis and fusion with the endosomal membrane, uncoating of the nucleocapsid, multiplication, i.e. synthesis of viral RNA and mRNA, and release of the new virus generation from the host cell surface. Potential drugs, directed towards each of these replication steps are described with respect to their mechanism of action, antiviral activity, toxic side effects and induction of resistance. The most promising candidates for safe and potent new influenza drugs, are antiviral agents, directed towards a virus-specific, well conserved target, such as inhibitors of virus-cell fusion, inhibitors of RNA transcriptase and endonuclease, and inhibitors of neuraminidase. It can be hoped that in the near future potent and therapeutically effective anti-influenza drugs will be available.
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PMID:Influenza chemotherapy: a review of the present state of art and of new drugs in development. 1120 14

The cell density-dependent growth inhibition of human SK-N-MC neuroblastoma cells is initiated by increased ganglioside sialidase activity leading to elevated cell surface presentation of ganglioside GM1, a ligand of galectin-1. We herein show that the extent of the cell surface expression of the galectin coincides with marked increases of the sialidase activity. Reverse transcriptase-polymerase chain reaction analysis excludes a regulation at the transcriptional level. Exposure of cells to purified galectin-1 reveals its carbohydrate-dependent activity to reduce cell proliferation. Assays to detect DNA fragmentation biochemically and cytometrically and to block caspases render it unlikely that galectin-1 acts as a classical proapoptotic factor on these cells. Because the chimeric galectin-3 shares binding sites and binding parameters with galectin-1 for these cells, we tested whether this galectin will elicit the same response as the homodimeric cross-linking galectin-1. Evidently, galectin-3 fails to affect cell growth by itself but interferes with galectin-1 upon coincubation. Its proteolytically truncated variant, the C-terminal lectin domain with impaired capacity to form aggregates when surface bound, has only weak binding properties. Thus, the way in which the galectin-1 interacts topologically with an apparently common set of ligands relative to galectin-3 is crucial for eliciting post-binding events. We conclude that galectin-1 is a probable effector in the sialidase-dependent growth control in this system. Moreover, the experiments with galectin-3 reveal functional divergence, most probably based on different topologies of presentation of homologous carbohydrate-binding sites.
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PMID:Negative regulation of neuroblastoma cell growth by carbohydrate-dependent surface binding of galectin-1 and functional divergence from galectin-3. 1145 61


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