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)

An RNA-dependent RNA polymerase activity has been found associated with Uukuniemi virions. The enzyme activity is expressed only after disrupting the virions with the nonionic detergent Triton X-100 and is absolutely dependent on Mn2+, whereas Mg2+ is not required, a finding that distinguishes this polymerase from those of other enveloped minus-strand RNA viruses. Within the range pH 7.2 to 8.5 no distinct optimum was found. The optimum temperature was between 37 and 40 C. The reaction was not inhibited by actinomycin D, rifampin, or DNase, whereas RNase was completely inhibitory. The partially RNase-resistant product consisted of rather small-sized RNA, which contained sequences complementary to Uukuniemi virus RNA as shown by hybridization to the template L, M, and S RNA species of Uukuniemi virus.
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PMID:Uukuniemi virus contains an RNA polymerase. 0 May 17

Two newly synthesized pyrimidine derivatives were found to possess antiviral activity against Mengovirus in Fogh and Lund (FL) cells and in a cell-free system. The inhibitory effect on RNA-dependent RNA polymerase of Mengovirus-infected FL cells was assayed using 14C-UTP as precursor. Addition of 50 or 100 muM of the inhibitors in a cell-free system of crude enzyme and nucleoside triphosphate medium for 60 min incubation at 37 degrees C resulted in about 40 to 60% lower counting rates for drug-treated reaction mixtures. The analysis of the polymerase synthesis product (virus RNA extracted from the cell-free reaction mixture and deproteinized by the phenol-SDS method) was carried out by means of agarose-acrylamide gel electrophoresis. The main finding was a reduction of single-stranded Mengovirus RNA (RNase-sensitive and LiCl-precipitable). The rates of synthesis of the replicative intermediate (LiCl-precipitable) and the replicative form of RNA (LiCl-soluble) were not significantly influenced.
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PMID:Effects of pyrimidine derivatives on RNA-dependent RNA polymerase of mengovirus-infected Fogh and Lund (FL) cells. 18 80

A soluble RNA-dependent RNA polymerase was isolated from poliovirus-infected HeLa cells and was shown to copy poliovirus RNA in vitro. The enzyme was purified from a 200,000-X-g supernatant of a cytoplasmic extract of infected cells. The activity of the enzyme was measured throughout the purification by using a polyadenylic acid template and oligouridylic acid primer. The enzyme was partially purified by ammonium sulfate precipitation, glycerol gradient centrifugation, and phosphocellulose chromatography. The polymerase precipitated in a 35% saturated solution of ammonium sulfate, sedimented at about 7S on a glycerol gradient, and eluted from phosphocellulose with 0.15 M KC1. The polymerase was purified about 40-fold and was shown to be totally dependent on exogenous RNA for activity and relatively free of contaminating nuclease. The partially purified polymerase was able to use purified polio virion RNA as well as a template. Under the reaction conditions used, the polymerase required an oligouridylic acid primer and all four ribonucleside triphosphates for activity. The optimum ratio of oligouridylic acid molecules to poliovirus RNA molecules for priming activity was about 16:1. A nearest-neighbor analysis of the in vitro RNA product shows it to be heteropolymeric. Annealing the in vitro product with poliovirus RNA product shows it to be heteropolymeric. Annealing the in vitro product with poliovirus RNA rendered it resistant to RNase digestion, thus suggesting that the product RNA was complementary to the virion RNA template.
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PMID:Isolation of a soluble and template-dependent poliovirus RNA polymerase that copies virion RNA in vitro. 23 68

An RNA-dependent RNA polymerase activity has been found copurifying with measles virus infectivity and complement-fixing antigen in three Vero cell-grown variants of measles virus: the attenuated Edmonston B strain, the natural non-attenuated Edmonston strain, and a subacute sclerosing panencephalitis isolate, IP-3. Incubation of purified measles virions with immunoglobulin G derived from sera of monkeys hyperimmunized against measles specifically removes activity sedimenting in the density region of measles virions. The requirements of the reaction, which is RNase sensitive, are similar to those reported for other paramyxovirus-associated activities, including detergent, divalent cation, ribonucleoside triphosphates, and a reducing agent. The size classes of RNA synthesized correspond to those found in measles-infected cells, including 50, 35, and 16 to 20S. The product RNA of the Edmonston B virus-stimulated reaction was rendered RNase resistant by annealing with RNA extracted from purified Edmonston B virions. RNA from uninfected Vero cells was ineffective in the annealing reaction.
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PMID:Characterization of an RNA-dependent RNA polymerase activity associated with measles virus. 64 73

A fraction containing membrane-bound tobacco mosaic virus RNA replicase was isolated form tobacco mosaic virus-infected tobacco callus cultures. The replicase activity reached a maximum 60 h after inoculation and then declined. The enzyme activity was insensitive to actinomycin D and DNase. The corresponding fraction from healthy callus contained essentially no activity. The viral RNA synthesis in vitro proceeded linearly for 30 min and required the four nucleotide triphosphates and Mg2+ ions. Mn2+ was a poor substitute for Mg2+. During RNA synthesis the product was at least 70% resistant to RNase in 2X SSC (0.15 M NaCl plus 0.015 M sodium citrate), but completely digested by RNase in 0.1X SSC. Analysis of the product by polns) that appeared to be replicative form and a partially RNase-resistant structure similar to replicative intermediate form. Washing the membrane-bound replicase with Mg2+-deficient buffer solubilized enzyme. The solubulized enzyme was further purified by DEAE-Sephadex column chromatography. The DEAE-purified enzyme was nearly completely dependent upon tobacco mosaic virus RNA for activity. Analysis of the product on a sucrose gradient revealed a double-stranded RNA with sedimentation of 16S and smaller heterogeneous RNase-sensitive products.
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PMID:In vitro replication of tobacco mosaic virus RNA in tobacco callus cultures: solubilization of membrane-bound replicase and partial purification. 83 35

The triggering mechanism for interferon synthesis in mouse peritoneal macrophages and chick embryo (CE) cells by Newcastle disease virus (NDV) exposed to hydroxylamine or homologous antiserum was investigated in relation to the intracellular fate of these agents. Inactivation of NDV at 22 degrees C by I M-hydroxylamine proceeded with first-order kinetics, whereas the interferon-inducing capacity of hydroxylamine-treated virus in macrophages was unimpaired. In contrast to infective NDV, hydroxylamine-inactivated virus produced interferon in CE cells, and such a virus still had partial RNA-dependent RNA polymerase activity. Hydroxylamine-inactivated NDV was adsorbed to and uncoated in both normal and chloroquine diphosphate treated cells, but no viral double-stranded RNA was detected. Hydroxylamine treatment of virion-extracted RNA and neutralization of intact virions by antibody abolished the capacity of the virus to induce interferon. Infective as well as neutralized NDV interacted with macrophages to the same degree, but association between NDV and CE cells was prevented by antibody-coating. In macrophages, the RNA of neutralized NDV became more sensitive to RNase than RNA of infective NDV, but this process was inhibited in chloroquine diphosphate-treated cells. These results suggest that interferon induction by NDV involves components of the virion which are present up to the regular uncoating process.
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PMID:Viral factors required for interferon induction by Newcastle disease virus in mouse macrophages and chicken embryo cells. 94 45

Ribonucleic acid (RNA)-dependent RNA polymerase activity was demonstrated in the microsomal and ribosomal fraction from the spleen cells of immunized mice. The enzyme activity was solubilized by Triton X-100 from the fraction and partially purified by Biogel A 1.5 m column chromatography. The RNA-dependent RNA polymerase activity was eluted in a single peak from the column. High activity was demonstrated with an RNA polymerase activity was eluted in a single peak from the column. High activity was demonstrated with an RAN preparation (iotaRNA) as template made from the spleens of immunized mice but very low activity was found with an RNA preparation made from the spleens of normal mice. Incorporation of 3H-UTP markedly decreased in the presence of RNase but not in the presence of DNase. DNA preparations made from the spleens of immunized mice were inactive as template for this enzyme. The iotaRNA preparation was fractionated by sucrose density gradient centrifugation. A fraction corresponding to 12-13 S was most active as a template. It was followed by a fraction corresponding to 6-7 S. Sucrose gradient analysis of the 3H-UTP-labeled product was attempted. Some properties of this enzyme are described.
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PMID:Ribonucleic acid-dependent ribonucleic acid polymerase in the immune response. 123 May 9

Insulin-like growth factors I and II (IGF I and II) are polypeptides with both growth-promoting and insulin-like metabolic effects. Immunoreactive IGF I is present in the retina and both IGF I and II are present in vitreal fluid. The type I and type II IGF receptors are also localized within the neural retina. The presence of IGFs and IGF receptors within the eye suggests a possible growth-promoting effect of IGFs on ocular tissues. IGF may enter the eye from the blood or, alternatively, arise from an ocular cell type which synthesizes and secretes IGF. IGF I and II mRNA synthesis in scleral cells and IGF I synthesis in rat retina suggests endogenous IGF production in the eye. We hypothesized that IGFs and IGF receptors are synthesized by one ocular cell type, the retinal pigment-epithelium (RPE). As a first step in studying IGF production by the RPE, we analyzed expression of the IGF and IGF receptor genes by cultured human RPE cells. Using Northern analysis, RNase protection and reverse-transcriptase polymerase chain reaction (RT-PCR), we found that cultured RPE cells synthesize mRNA for IGF I and the type I and type II IGF receptors.
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PMID:Gene expression of the insulin-like growth factors and their receptors in cultured human retinal pigment epithelial cells. 137 66

DNA-directed RNA polymerase is responsible for gene expression. Despite its importance, many details of its function and higher-order structure still remain unknown. We report here a local sequence similarity between the second largest subunit of RNA polymerase II and bacterial RNases Ba (barnase), Bi, and St. The most remarkable similarity is that the catalytic sites of the RNases are shared with the eukaryotic RNA polymerase II subunits of Drosophila melanogaster and Saccharomyces cerevisiae. Several amino acids conserved among the RNases and the RNase-like domains of the RNA polymerase subunits are located in the neighborhood of the catalytic sites of barnase, whose three-dimensional structure has been resolved. This observation suggests the functional importance of the RNase-like domain of the RNA polymerase subunits and indicates that the RNase-like domain may have RNase activity. The location of the RNase-like domain relative to the region necessary for RNA polymerization is similar to the relative proximity of 5'----3' or 3'----5' exonuclease and the region of polymerase activity of DNA polymerase I. The RNase-like domain might work in proofreading, as in RNA-directed RNA polymerase of influenza virus, or it may contribute to RNA binding through an unknown function.
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PMID:RNase-like domain in DNA-directed RNA polymerase II. 192 68

The 447 male sterility trait in Vicia faba is strictly correlated with the presence of well-defined membranous vesicles or 'cytoplasmic spherical bodies' not found in fertile isogenic maintainer plants, and by the occurrence of a discrete high molecular weight double-stranded RNA. We have purified these cytoplasmic membranous vesicles and find that they contain the dsRNA together with an RNA-dependent RNA polymerase whose activity depends upon the presence of Mg2+, requires the four-nucleoside triphosphates and is unaffected by inhibitors of cellular transcriptases, e.g. alpha-amanitin and Actinomycin D. The dsRNA can be labelled in vitro by incubating the cytoplasmic vesicles with radioactive NTPs, and the RNA synthesized in vitro is also in a double-stranded form as judged by its resistance to RNase digestion at high salt and its behaviour upon CF-11 chromatography. Treatment of the vesicles with a non-ionic detergent releases the dsRNA in the form of a complex with the RNA-dependent RNA polymerase. The enzyme can still carry out the specific synthesis of dsRNA in these solubilized complexes. The cytoplasmic vesicles therefore isolate this vertically transmitted, self-replicating dsRNA from the cellular milieu: the possible mode of action and relevance of this novel genetic element to the 447 cytoplasmic male sterility trait are discussed.
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PMID:The double-stranded RNA associated with the '447' cytoplasmic male sterility in Vicia faba is packaged together with its replicase in cytoplasmic membranous vesicles. 210 29


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