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:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cloned cDNA encoding the Sendai virus (SV) hemagglutinin-neuraminidase (HN) envelope glycoprotein was expressed in cultured cells in two ways: (I) infection with HN-expressing recombinant vaccinia virus, or (II) transfection with a plasmid with T7 promoter and termination sequences flanking the HN gene, with intracellular T7 RNA polymerase supplied by coinfection with recombinant vaccinia virus that expresses the enzyme. The HN expressed was indistinguishable from the authentic SV protein in antigenicity, cell surface location, and formation of oligomeric structures. In addition, HN expressed from cDNA functioned normally in both hemadsorption and neuraminidase activities. The usefulness of cDNA expression for analyzing HN structure and function was evaluated by mutating the HN cDNA and observing the consequences for HN protein activity. Since previous work indicated that the lysine residue at position 461 is important for the neuraminidase activity of HN, we used site-directed mutation to produce HN protein with this lysine residue changed to glutamic acid. The mutated HN had neuraminidase activity with significantly increased thermal stability, indicating that residue 461 may be essential to the protein's conformation.
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PMID:Expression of cDNA encoding the Sendai virus hemagglutinin-neuraminidase gene: characterization of wild-type and mutant gene products. 131 81

Vaccinia virus-dependent CAT expression was observed in virus-infected cells cotransfected with a promoterless CAT gene. Restriction endonuclease resection of the CAT plasmid indicated that expression was due to recognition by vaccinia virus RNA polymerase of sequences within the CAT gene itself, probably located within the 5' untranslated region of the gene. This observation is relevant to the design of reverse-genetic systems which use CAT as a reporter gene to detect replication of negative-strand RNA virus pseudogenomes.
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PMID:Tn9 CAT gene contains a promoter for vaccinia virus transcription: implications for reverse-genetic techniques. 131 41

Homeobox-containing genes encode transcription factors that, via the homeodomain, bind specifically to DNA. To study the DNA-binding properties of the murine homeodomain-containing protein, Hox-2.3, a hybrid expression system was used, combining gene expression by recombinant vaccinia virus (reVV) with bacteriophage T7 transcription. Expression was achieved by co-infecting HeLa cells with two reVVs, one expressing the T7-RNA polymerase-encoding gene directed by the VV promoter, P7.5, and another containing the Hox-2.3 coding sequence under control of a T7 promoter [Fuerst et al., Mol. Cell. Biol. 7 (1987) 2538-2544]. Co-infected HeLa cells produced large amounts of full-length Hox-2.3 protein. Cytoplasmic and nuclear extracts from these cells were used to examine DNA-binding specificity in vitro. reVV-produced Hox-2.3 protein bound to oligos that contained one or several copies of the common homeodomain-binding site, 5'-TCA-ATTAAAT, and to a lesser extent to multiple (TAA) repeats. Using Southwestern blot analysis, no Hox-2.3-binding sites were detected in a region of the Hox-2 cluster containing the Hox-2.3, Hox-2.4 and Hox-2.5 genes.
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PMID:DNA-binding activity of the murine homeodomain protein Hox-2.3 produced by a hybrid phage T7/vaccinia virus system. 135 46

We have resolved, by native gel electrophoresis, two intermediates in the transcription of a vaccinia virus early gene by the virus-encoded RNA polymerase. Polymerase holoenzyme containing the vaccinia virus early transcription factor (VETF) forms a complex of VETF bound to the promoter as the first step in a pathway leading to establishment of a committed ternary elongation complex. Formation of the VETF-DNA complex is stimulated by magnesium but is uninfluenced by nucleoside triphosphates. A stable binary complex of RNA polymerase bound to DNA is not detected. Assembly of a gel-stable polymerase-DNA complex depends on conditions permissive for RNA synthesis. Nucleotide omission experiments suggest that at least a tetrameric RNA must be made before a ternary complex is stabilized. RNA analysis indicates that complexes containing nascent transcripts 20 nucleotides long are stable and active. Ternary complex formation requires hydrolyzable ATP. This is consistent with an essential role for the ATPase activity of VETF at a step subsequent to DNA binding, as proposed by Broyles (S. S. Broyles, J. Biol. Chem. 266:15545-15548, 1991). The ternary complex, once formed, is resistant to dissociation by competitor DNA, as well as by salt, Sarkosyl, and heparin. The effects of these inhibitory agents on transcription complex formation suggest that they target different steps in the assembly pathway.
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PMID:Ternary complex formation by vaccinia virus RNA polymerase at an early viral promoter: analysis by native gel electrophoresis. 137 99

A molecular cDNA clone (P1 KIN) was isolated that encodes the human RNA-dependent P1/eIF-2 alpha protein kinase. The complete cDNA sequence of the P1 KIN cDNA was determined; the longest open reading frame (ORF) encoded a 551 amino acid protein with a deduced molecular weight of 62055 Da. Transcripts prepared from the P1 KIN cDNA by transcription in vitro with T7 RNA polymerase programmed the cell-free synthesis of a protein indistinguishable by immunoprecipitation and immunoblot gel analyses from the authentic 67-kDa P1 protein synthesized in human U cells treated with interferon (IFN). Furthermore, by use of a sensitive primer extension assay with T7 DNA polymerase, the major site of translation initiation within the deduced ORF of the P1 KIN cDNA was directly identified. Northern RNA gel-blot analysis revealed that the P1 KIN cDNA strongly hybridized to two IFN-induced mRNAs present in both human amnion U cells and HeLa cells; their sizes were 2.5 and 6 kb. Both transcripts were efficiently induced by IFN-alpha, but poorly by IFN-gamma. Polyclonal antibody was prepared against the product of the P1 KIN cDNA expressed in Escherichia coli. In Western blot analysis the antibody recognized a 67-kDa protein induced in human cells by IFN-alpha and, in addition, a 90-kDa protein whose level was not greatly altered by IFN treatment. The IFN-induced 67-kDa protein was found associated with the ribosomal salt-wash fraction of IFN-treated human cells, whereas the 90-kDa protein was predominantly in the S100 soluble fraction. The time course for the induction by IFN-alpha of RNA-dependent protein P1 kinase activity measured by immunoprecipitation was comparable to the time course for protein P1 induction measured by Western immunoblot analysis. The amino acid sequence of P1/eIF-2 alpha protein kinase deduced from the cDNA was 62% identical with the 518-residue murine TIK kinase and contained, within the carboxy-terminal half of the protein, the motifs commonly conserved among protein-serine/threonine kinases. The amino-terminal half of the P1 protein did not possess conserved kinase motifs, but did show extensive homology with vaccinia virus-predicted protein E3L.
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PMID:Mechanism of interferon action: cDNA structure, expression, and regulation of the interferon-induced, RNA-dependent P1/eIF-2 alpha protein kinase from human cells. 137 53

Cytotoxic T lymphocytes (CTL) have been found to mediate protection in vivo against certain virus infections. CTL also may play an important role in control of infection by hepatitis C virus (HCV), but no CTL epitopes have yet been defined in any HCV protein. The nonstructural protein with homology to RNA polymerase should be a relatively conserved target protein for CTL. To investigate the epitope specificity of CTL specific for this protein, we used 28 peptides from this sequence to study murine CTL. Mice were immunized with a recombinant vaccinia virus expressing the HCV nonstructural region corresponding to the flavivirus NS5 gene (RNA polymerase), and the primed spleen cells were restimulated in vitro with peptides. CTL from H-2d mice responded to a single 16-residue synthetic peptide (HCV 2422 to 2437). This relatively conserved epitope was presented by H-2d class I major histocompatibility complex (MHC) molecules to conventional CD4- CD8+ CTL but was not recognized by CTL restricted by H-2b. Moreover, exon shuffle experiments using several transfectants expressing recombinant Dd/Ld and Kd demonstrated that this peptide is seen in association with alpha 1 and alpha 2 domains of the Dd class I MHC molecule. This peptide differs from the homologous segments of this nonstructural region from three other HCV isolates by one residue each. Variant peptides with single amino acid substitutions were made to test the effect of each residue on the ability to sensitize targets. Neither substitution affected recognition. Therefore, these conservative mutations affected peptide interaction neither with the Dd class I MHC molecule nor with the T-cell receptor. Because these CTL cross-react with all four sequenced isolates of HCV in the United States and Japan, if human CTL display similar cross-reactivity, this peptide may be valuable for studies of HCV diagnosis and vaccine development. Our study provides the first evidence that CD8+ CTL can recognize an epitope from the HCV sequence in association with a class I MHC molecule.
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PMID:Induction of cytotoxic T cells to a cross-reactive epitope in the hepatitis C virus nonstructural RNA polymerase-like protein. 137 66

Bacterial fusion proteins containing portions of the Bunyamwera virus L protein were used as immunogens to prepare antisera in rabbits. Of five fusion proteins injected into rabbits, three yielded sera that reacted with the Bunyamwera virus L protein, detected by Western blotting or immunoprecipitation. Two of these antisera were specific for either the amino- or carboxy-terminal regions of the L protein. The specificity of these antisera was confirmed by their pattern of reactivity with full-length and truncated forms of the L protein. Plasmids containing the L gene cDNA under control of a bacteriophage T7 promoter were transfected into CV-1 cells which had previously been infected with a recombinant vaccinia virus, vTF7-3, that expresses T7 RNA polymerase. Antigenically authentic L protein was expressed. Using a nucleocapsid transfection assay developed previously, we showed that the transiently expressed L protein had RNA synthesis activity. Site-specific mutations were made in the L cDNA-containing plasmid to change certain amino acids in the putative polymerase domain of the L protein. The effects of these amino acid substitutions on the RNA synthesis activity of the L protein were monitored using the nucleocapsid transfection assay. These experiments showed that residues strictly conserved between the L proteins of different viruses in the family Bunyaviridae were obligatorily required for activity, whereas non-conserved residues could be substituted without abolishing RNA synthesis capability. Our results provide direct evidence for the functional significance of particular amino acids in the polymerase domain of a negative-strand virus RNA polymerase.
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PMID:Mutagenesis of the L protein encoded by Bunyamwera virus and production of monospecific antibodies. 140 14

The gene encoding the major replicative protein, NS1, of minute virus of mice (MVM) was transferred into a recombinant vaccinia virus vector in place of the vaccinia thymidine kinase gene. The NS1 gene was placed under control of a bacteriophage T7 promoter and expressed in cells coinfected with another recombinant vaccinia virus, vTF7-3, which encodes the T7 RNA polymerase. Expression of NS1 was further enhanced by the presence of a 5' untranslated region, derived from encephalomyocarditis virus, which allows efficient cap-independent translation. This system was used to produce and analyze wild-type NS1 and two mutant forms of the protein, NS1K405R and NS1K405M, in which the highly conserved lysine codon located in the putative purine triphosphate binding site of NS1 was changed to arginine and methionine, respectively. Full-length NS1 was expressed efficiently in both human and mouse cells infected with each of the three recombinant viruses, and in each case the NS1 was rapidly and efficiently translocated into the nucleus. Wild-type NS1 expressed in this way was biologically active. It was able to trans-activate an MVM P38 promoter located in a host chromosomal site, whereas the two mutant forms of NS1 showed no significant activity in this assay, and it was capable of resolving palindromic junction fragments cloned from multimeric MVM replicative form DNA molecules. These substrates, representing MVM genomic left-end:left-end and right-end:right-end fusions, were resolved in a DNA synthesis-dependent in vitro reaction supplemented with nuclear extracts containing recombinant wild-type NS1. Neither of the two mutant forms of the polypeptide had any detectable activity in this assay.
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PMID:Expression of functional parvoviral NS1 from recombinant vaccinia virus: effects of mutations in the nucleotide-binding motif. 141 12

We have examined the role of ras-related rab proteins in transport from the ER to the Golgi complex in vivo using a vaccinia recombinant T7 RNA polymerase virus to express site-directed rab mutants. These mutations are within highly conserved domains involved in guanine nucleotide binding and hydrolysis found in ras and all members of the ras superfamily. Substitutions in the GTP-binding domains of rab1a and rab1b (equivalent to the ras 17N and 116I mutants) resulted in proteins which were potent trans dominant inhibitors of vesicular stomatitis virus glycoprotein (VSV-G protein) transport between the ER and cis Golgi complex. Immunofluorescence analysis indicated that expression of rab1b121I prevented delivery of VSV-G protein to the Golgi stack, which resulted in VSV-G protein accumulation in pre-Golgi punctate structures. Mutants in guanine nucleotide exchange or hydrolysis of the rab2 protein were also strong trans dominant transport inhibitors. Analogous mutations in rab3a, rab5, rab6, and H-ras did not inhibit processing of VSV-G to the complex, sialic acid containing form diagnostic of transport to the trans Golgi compartment. We suggest that at least three members of the rab family (rab1a, rab1b, and rab2) use GTP hydrolysis to regulate components of the transport machinery involved in vesicle traffic between early compartments of the secretory pathway.
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PMID:GTP-binding mutants of rab1 and rab2 are potent inhibitors of vesicular transport from the endoplasmic reticulum to the Golgi complex. 142 35

The structure of the elongation complex of vaccinia RNA polymerase halted at discrete template positions was examined by DNase I footprinting. The leading edge of the footprint bore a constant relationship to the catalytic template position, being 22-24 nucleotides (nt) in advance on the nontemplate strand and 17 nt on the template strand. DNase hypersensitivity of the nontemplate strand at the leading edge suggested that the DNA might be distorted as it entered the polymerase molecule. The region of DNA unwinding at the transcription bubble extended at least 12 nt 5' from the catalytic center, as indicated by the reactivity of adenosine residues to diethylpyrocarbonate. Cu-phenanthroline-hypersensitive sites located 13 nt 5' and 4 nt 3' of the growing point appeared to demarcate the margins of the bubble. Strand asymmetry of chemical modification within the bubble was consistent with an RNA-DNA hybrid of no more than 10 base pairs.
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PMID:Structural analysis of ternary complexes of vaccinia RNA polymerase. 143 98


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