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)

Human coronavirus RNA, prepared by extraction of purified virions with phenol-chloroform, consists of a major 15 to 55S class and a minor 4S class of RNA fragments. Polyadenylic acid [poly (A)] sequences are present in 15 to 55S but not in 4S RNA, suggesting different functions for each class. A stretch of poly (A) of approximately 19 adenosine monophosphate residues was obtained in sizing experiments after digesting OC-43 RNA with pancreatic and T1 ribonucleases. An OC-43 virion RNA transcriptase could not be detected with systems optimal for detecting the transcriptases of influenza and Newcastle disease virus.
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PMID:Presence of genomic polyadenylate and absence of detectable virion transcriptase in human coronavirus OC-43. 64 31

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

The nucleotide sequence of the L gene of Marburg virus, strain Musoke, has been determined. The L gene has a single long open reading frame encoding a polypeptide of 2330 amino acids (MW 267,175) that represents the viral RNA-dependent RNA polymerase. The putative transcription start signal (3'CUACCUAUAAUU 5') and the termination signal (3' UAAUUCUUUUU 5') of the gene could be identified. Computer-assisted comparison of the L protein with L proteins of other nonsegmented negative-stranded RNA viruses (Paramyxoviridae: Sendai virus, Newcastle disease virus, human parainfluenza 3 virus, measles virus, human respiratory syncytial virus; Rhabdoviridae: vesicular stomatitis virus, rabies virus) revealed significant homologies primarily in the N-terminal half of the proteins. We have identified three common conserved boxes (A, B, and C) among filo-, paramyxo-, and rhabdovirus L proteins, which are probably involved in the polymerase function. The L proteins can be divided into an N-terminal half, which seems to accommodate the common enzymatic sites, and a C-terminal half carrying virus specific peculiarities. The data presented here suggest a common evolutionary history for all nonsegmented negative-stranded RNA viruses and show that filoviruses are more closely related to paramyxo- than to rhabdoviruses.
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PMID:The nucleotide sequence of the L gene of Marburg virus, a filovirus: homologies with paramyxoviruses and rhabdoviruses. 154 52

We have now completed the rabies genome structure by the cloning and the sequencing of the entire L gene and the 5' untranscribed region. The L gene encodes a single open reading frame 2142 amino acids in length (244,206 Da) that corresponds to the viral RNA-dependent RNA polymerase. In contrast with other isofunctional proteins, the rabies polymerase exhibits a high degree of homology with the vesicular stomatitis virus polymerase, and a lesser degree, although significant, with those of Sendai virus and Newcastle disease virus, which suggests a differential evolution of the different cistrons. We have observed several strongly conserved stretches which may designate the independent functional domains of this multifunctional protein. In addition to the conservation of related transcription signals (N. Tordo et al. (1986) Proc. Natl. Acad. Sci. USA 83, 3914-3918.), this highlights the striking selective pressure on elements involved in transcription and replication mechanisms, and provides further evidence for a common ancestry of Rhabdoviridae and Paramyxoviridae families. The terminal complementarity observed in the rabies genome suggests the conservation of important genomic signals.
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PMID:Completion of the rabies virus genome sequence determination: highly conserved domains among the L (polymerase) proteins of unsegmented negative-strand RNA viruses. 340 52

Heterologous viral interference is induced by Sindbis virus against vesicular stomatitis virus (VSV) in a manner analogous to intrinsic interference with Newcastle disease virus replication. Interference in both systems (i) depends upon early expression of the inducing virus genome, (ii) shows similar kinetics of induction, (iii) does not involve interferon action, and (iv) appears to be manifest as an all-or-none effect. VSV can be added to the list of viruses blocked by intrinsic interference. Sindbis virus-induced intrinsic interference with VSV replication is not mediated through homotypic interference by defective interfering particles; rather, T-particle and B-particle synthesis is inhibited. Significantly, intrinsic interference has no effect on primary transcription directed by the virion-associated transcriptase in VSV-challenged cells. However, Sindbis virus appears to induce interference with the VSV-RNA synthesized subsequent to primary transcription, namely, that which is dependent on protein synthesis. Thus, the target of intrinsic interference appears to be a reaction subsequent to primary transcription but prior to the appearance of protein synthesis-dependent VSV RNA, secondary transcription.
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PMID:Mechanism of Sindbis virus-induced intrinsic interference with vesicular stomatitis virus replication. 436 26

The temperature-sensitive defects of virus mutants isolated from L cells persistently infected with Newcastle disease virus (NDV) were analyzed. Genetic grouping of the mutants by complementation tests was attempted by using several different methods, including yield analysis, RNA synthesis, and heterozygote formation at 42 to 43 C, the nonpermissive temperature. In each case, specific interference prevented detection of complementation. This interference was shown to occur prior to or at the level of virus RNA synthesis. Temperature-shift experiments with five different NDV(pi) clones showed that virus replication begun at 37 C could not be completed at the nonpermissive temperature. The activity of the NDV-specific RNA-dependent RNA polymerase in the cytoplasm of infected chicken embryo cells was not stable and could not be demonstrated directly. However, indirect measurement of RNA polymerase activity at the nonpermissive temperature was accomplished by studying the kinetics of virus-specific RNA synthesis in infected cells after temperature shift. Two types of response were obtained: with three NDV(pi) clones, virus-specific RNA synthesis ceased immediately upon transfer of infected cells to 42 to 43 C, whereas in cells infected with two other NDV(pi) clones, RNA synthesis continued for several hours at this temperature. These results suggested that there may be two types of ts defects in NDV(pi), both associated with virus-specific RNA polymerase activity.
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PMID:Temperature-sensitive defect of mutants isolated from L cells persistently infected with Newcastle disease virus. 479 30

Virions of Newcastle disease virus (NDV) were disrupted with Triton X-100 in the presence of high salt and nucleocapsids were isolated by ultracentrifugation. The nucleocapsids had very low transcriptase activity and contained only NP as a prominent protein constituent, the bulk of L and P proteins not being retained. The L and P proteins were isolated by sequential treatment of the virions with low- and high-salt detergent followed twice by successive chromatography on phosphocellulose column and examined for their effect on RNA synthesis in a standard transcriptase system using the nucleocapsids as template. When both L and P proteins were added to the template, the RNA synthetic activity was greatly stimulated. P protein alone could not enhance but rather suppressed the activity. L protein exhibited stimulation to some extent but due to residual small amount of P protein in both L protein fraction and the template it has not been elucidated whether L protein could function as a polymerase by itself. These results indicate that both L and P proteins are required to reconstitute a fully active transcriptive complex with a functional template. Attempts have been made to isolate intracellular transcriptive complex from NDV-infected MDBK cells and to determine the protein species involved. The active complex has been recovered neither from cytoplasmic extract obtained by hypotonic disruption nor from Triton X-100 soluble fraction of the cells. However, we could isolate the complex from an extract by double detergents (Tween 40 and deoxycholate) solubilization. The complex contained L, P, and NP as virus specific proteins and several cellular proteins. These results support the concept that both L and P proteins are required for NDV-RNA synthesis and suggest further that the intracellular transcriptive complex may be associated with some cellular structure resistant to Triton X-100 but sensitive to the double detergents, presumably cytoskeletal frame work.
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PMID:Transcriptive complex of Newcastle disease virus. I. Both L and P proteins are required to constitute an active complex. 668 7

Recombinant lentogenic Newcastle disease virus (NDV) of the vaccine strain Clone-30 was reproducibly generated after simultaneous expression of antigenome-sense NDV RNA and NDV nucleoprotein, phosphoprotein and RNA-dependent RNA polymerase from plasmids transfected into cells stably expressing T7 RNA polymerase. For this purpose, the genome of Clone-30, comprising 15186 nt, was cloned and sequenced prior to assembly into a full-length cDNA clone under control of a T7 RNA polymerase promoter. Recombinant virus was amplified by inoculation of transfection supernatant into the allantoic cavity of embryonated specific-pathogen-free (SPF) chicken eggs. Two marker restriction sites comprising a total of five nucleotide changes artificially introduced into noncoding regions were present in the progeny virus. The recombinant NDV was indistinguishable from the parental wild-type virus with respect to its growth characteristics in cell culture and in embryonated eggs. Moreover, an intracerebral pathogenicity index of 0.29 was obtained for both viruses as determined by intracerebral inoculation of day-old SPF chickens, proving that the recombinant NDV is a faithful copy of the parental vaccine strain of NDV.
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PMID:Generation of recombinant lentogenic Newcastle disease virus from cDNA. 1058 61

The inhibition by interferons of viral replication was studied with cell-free preparations of the enzyme RNA synthetase derived from calf kidney cells infected with influenza virus and from chick embryo fibroblasts infected with Newcastle disease virus. Calf, mouse, and chicken interferons inhibited these enzymes with the same characteristic species specificity observed in tissue culture. A mechanism of action is proposed.
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PMID:INTERFERONS: SELECTIVITY AND SPECIFICITY OF ACTION IN CELL-FREE SYSTEMS. 1416 46

Nucleotide sequence was determined for the RNA-dependent RNA polymerase (L) gene of 16 Newcastle disease virus (NDV) isolates from diverse geographic and chronological origins. The observed consensus amino acid sequence conformed to the six domains previously identified among paramyxovirus L proteins, and the putative 749QGDNQ753 active site was strictly conserved among all isolates. Analysis of predicted amino acid sequences allowed us to identify a sequencing error in the previously reported L genes for NDV. The correct sequences reported herein provided a more accurate alignment with predicted l-amino acid sequences of other paramyxoviruses. Comparison of L gene coding sequences among isolates revealed that synonymous substitutions dominated non-synonymous substitutions, as observed previously with other NDV genes. However, the overall substitution rate was lower than other genes examined making the L gene the most conserved of the NDV genome. Phylogenetic analysis of L genes among NDV isolates was consistent with previous results that suggested the existence of two major lineages. One group contained strains isolated in North America prior to 1970 and included virulent and vaccine strains, while the second group included virulent viruses isolated worldwide. A comparison of the NDV L coding sequences to other Paramyxoviridae illustrated the unique clustering of the avian-specific paramyxoviruses, further justifying the newly created Avulavirus genus.
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PMID:RNA-dependent RNA polymerase gene analysis of worldwide Newcastle disease virus isolates representing different virulence types and their phylogenetic relationship with other members of the paramyxoviridae. 1517 94


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