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)

The genome of infectious bursal disease virus (IBDV) consists of two segments of double-stranded (ds)RNA with molecular weights of 2.2 X 10(6) and 1.9 X 10(6) Da, respectively. After treatment of IBDV particles with proteinase K in the presence of sodium dodecyl sulfate (SDS), linear dsRNA molecules are released from the virus particles. However, after heating of virus particles at 100 degrees for 3 min in 1.5% SDS, without the protease, dsRNA-protein complexes can be seen under the electron microscope: Knob-like proteinaceous structures are linked to the ends of the dsRNA molecules of either size class which are circularized to form individual rings. A 90,000-Da IBDV structural polypeptide, the only protein encoded by the smaller genome segment, has been demonstrated to remain firmly linked to the IBDV genome under these conditions. No functional data exist about this circularizing protein; it is a probable candidate for an RNA-dependent RNA polymerase or an assembly protein for the two dsRNA segments. At high particle concentrations, or when the preparations are allowed to stand for several hours before spreading, these complexes tend to aggregate to form flower-like structures.
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PMID:The two segments of the infectious bursal disease virus genome are circularized by a 90,000-Da protein. 303 77

Poliovirus-specific RNA-dependent RNA polymerase (replicase, 3Dpol) was purified from HeLa cells infected with poliovirus. The purified enzyme preparation contained two proteins of apparent molecular weights 63,000 and 35,000. The 63,000-Mr polypeptide was virus-specific RNA-dependent RNA polymerase, and the 35,000-Mr polypeptide was of host origin. Both polypeptides copurified through five column chromatographic steps. The purified enzyme preparation catalyzed synthesis of covalently linked dimeric RNA products from a poliovirion RNA template. This reaction was absolutely dependent on added oligo(U) primer, and the dimeric product appeared to be made of both plus- and minus-strand RNA molecules. Experiments with 5' [32P]oligo(U) primer and all four unlabeled nucleotides suggest that the viral replicase elongates the primer, copying the poliovirion RNA template (plus strand), and the newly synthesized minus strand snaps back on itself to generate a template-primer structure which is elongated by the replicase to form covalently linked dimeric RNA molecules. Kinetic studies showed that a partially purified preparation of poliovirus replicase contains a nuclease which can cleave the covalently linked dimeric RNA molecules, generating template-length RNA products.
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PMID:Primer-dependent synthesis of covalently linked dimeric RNA molecules by poliovirus replicase. 304 Oct 19

Much work has been done on the isolation, purification, and characterization of the RNA-directed RNA polymerase (EC 2.7.7.48) of cucumber mosaic virus (CMV)-infected cucumbers. Uninfected plants were reported to have no such enzyme, but we recently detected low levels of the activity in cucumber. Since tobacco and cowpea contain such an enzyme that is variably increased in amount by various virus (as well as viroid) infections, we assumed that this would also be the case upon CMV infection of cucumber. However, further purification and characterization of the RNA-directed RNA polymerases from healthy and from infected cucumber suggests that these are different enzymes. The presumed CMV replicase was obtained pure and consists of a major polypeptide of Mr 100,000 and minor components of Mr 110,000 and about 10,000. The Km is 5 microM ([3H]GTP) when tobacco mosaic virus RNA is used as template.
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PMID:RNA-directed RNA polymerases from healthy and from virus-infected cucumber. 345 3

All double-stranded RNA viruses have capsid-associated transcriptase activities. In the yeast viruses, as in reovirus, transcription appears to be the first stage of replication. We have found that the yeast viral transcriptase initiates RNA transcription in vitro and that the resultant plus strand RNA has the 5' terminus ppGp. No pre-existing primers are normally utilized in vitro. Like other double-stranded RNA viruses of eucaryotes, the yeast viruses have a primer-independent capsid-associated transcriptase. Unlike these viruses of higher eucaryotes, the yeast viruses synthesize uncapped mRNAs. Viral particles with only a single major capsid polypeptide are active in transcription and replication, while reovirus particles active in transcription have 5 or 6 polypeptides.
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PMID:Initiation by the yeast viral transcriptase in vitro. 355 91

The complete nucleotide sequence of the Japanese encephalitis virus (JEV) genome RNA was determined. The JEV genome contains 10,976 nucleotides and encodes a single long open reading frame (ORF) of 10,296 nucleotides corresponding to 3432 amino acid residues. This long polypeptide is thought to be cleaved into three structural proteins and several nonstructural proteins of the virus. The genetic location of the three structural proteins was determined by comparing the deduced amino acid sequence from the nucleotide sequence with the N-terminal amino acid sequences that were determined from the three purified structural proteins. The C-terminal region of the ORF may encode a RNA-dependent RNA polymerase which has significant sequence homology with those of other RNA viruses.
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PMID:Complete nucleotide sequence of the Japanese encephalitis virus genome RNA. 368 27

Two-dimensional gel electrophoresis (IEF and SDS-PAGE) was used to examine virion polypeptide changes associated with switch-on of transcriptase function in reovirus. Results reveal that switch-on is correlated with altered electrophoretic behavior of a specific minor polypeptide (delta 1) which is present in intermediate subviral particles. A second finding is that each of the molecular weight classes of viral polypeptides exists as a series of subspecies with different isoelectric points. This suggests that extensive posttranslational modification of progeny viral polypeptides occurs during particle morphogenesis. These findings have important theoretical and practical implications.
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PMID:Switch-on of transcriptase function in reovirus: analysis of polypeptide changes using 2-D gels. 406 May 93

A Sendai virus-induced transcriptase-template complex was isolated from the cytoplasm of infected cells by combined sedimentation and isopycnic centrifugation. This transcriptive complex banded at 1.27 g/cm(3) in D(2)O-sucrose gradients. It contained two polypeptides, the viral nucleocapsid structure unit (molecular weight, 60,000) and the largest virion polypeptide (molecular weight, 75,000). The buoyant density, chemical composition, and electron microscopic appearance of the transcriptive complex indicate a structure like that of viral nucleocapsids.
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PMID:Sendai virus-induced transcriptase from infected cells: polypeptides in the transcriptive complex. 411 61

A deoxynucleoprotein complex (DNP-1) isolated from simian virus 40 (SV40) after disruption of the virus in an alkaline buffer contains the viral deoxyribonucleic acid (DNA) and four minor structural polypeptides. Dissociation of DNP-I by equilibrium centrifugation in CsCl yields a complex (DNP-II) that contains a small amount of polypeptide tightly bound to the viral DNA. Studies of the template activity of these deoxynucleoprotein complexes in vitro with Escherichia coli transcriptase show that the rate of transcription of DNP-I and DNP-II is 30 and 80%, respectively, compared with that of deproteinized SV40 DNA component I. In dimethyl sulfoxide gradients, the complementary ribonucleic acid (cRNA) synthesized from DNP-I is one-third to one-half the size of the cRNA species from DNA-I and DNP-II. Competition hybridization experiments show that with the E. coli transcriptase only a portion (about one-half) of the SV40 genome is transcribed with DNP-I as template, whereas most or all of the genome is transcribed with DNP-II as template. The template activity of the deoxynucleoprotein complexes with a highly active form II ribonucleic acid polymerase prepared from SV40-infected permissive cells follows similar transcription kinetics. The results indicate that structural nucleoproteins of SV40 bind nonrandomly to the viral DNA and effect the transcription of some subset of its sequences in vitro.
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PMID:Structure and function of the polypeptides in simian virus 40. II. Transcription of subviral deoxynucleoprotein complexes in vitro. 433 39

The endogenous transcriptase present in purified vesicular stomatitis (VS) virions was solubilized with a Triton X-100 high-salt solution. The polymerase activity was purified on glycerol gradients and by phosphocellulose column chromatography; the viral proteins present in the active enzyme fractions were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It was demonstrated that L protein, but not NS protein, was required for in vitro RNA synthesis on the VS viral nucleocapsid template. Solubilized L protein rebinds to the ribonucleoprotein template when the transcription complex is reconstituted, and the RNA synthesized in vitro by purified L protein hybridizes to virion RNA. Cyanogen bromide peptide fingerprints indicate that the large L protein is a unique polypeptide chain. It is concluded that the L protein functions as the transcriptase, and the nucleocapsid NS protein is not essential for in vitro RNA synthesis.
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PMID:L protein requirement for in vitro RNA synthesis by vesicular stomatitis virus. 435 10

Sendai virions, disrupted in 2% Triton X-100 in 1 M KCl, were separated into nucleocapsids and envelope proteins by centrifugation. The nucleocapsids, representing 46% of the virion proteins, had a buoyant density of 1.29 gm/cm(3) in D(2)O sucrose. RNA-dependent transcriptase activity associated with them had a ninefold greater specific activity than transcriptase assayed in unfractionated detergent-disrupted virions. These enzyme-active nucleocapsids contained only two polypeptides, the largest virion polypeptide (molecular weight 75,000) and the nucleocapsid structure unit (molecular weight 60,000). Virion envelope proteins, either glycoproteins or nonglycosylated matrix protein, inhibited nucleocapsid-associated polymerase activity; brief heat denaturation abolished their inhibitory activity. Yeast RNA stimulated nucleocapsid-associated enzyme, suggesting that stimulatory polyanions act at the enzyme-template level.
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PMID:Sendai virion transcriptase complex: polyeptide composition and inhibition by virion envelope proteins. 435 18


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