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)

We have used plasmid clones spanning the region encoding the 132-kDa subunit of the cowpox virus RNA polymerase (CPV rpo 132) to marker rescue each of five vaccinia virus (VV) temperature sensitive (ts) mutants, ts 27, ts 29, ts 32, ts 47, and ts 62, which together constitute a single complementation group. The experiments fine-map the vaccinia mutations to a 1.3-kb region containing the 3' end of the CPV rpo 132 gene. Phenotypic characterization shows that all five mutants are affected to varying extents in their ability to synthesize late viral proteins at the nonpermissive temperature, similar to other ts mutants with lesions in the 22- and the 147-kDa subunits of the VV RNA polymerase. Two mutants, ts 27 and ts 32, exhibit a delay in the synthesis of late viral proteins at both the permissive and the nonpermissive temperatures. We conclude that the five VV mutants affect the 132-kDa subunit of the VV RNA polymerase. Additional genetic experiments demonstrate intragenic complementation between ts 62 and three other members of this complementation group, ts 27, ts 29, and ts 32.
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PMID:Fine structure mapping and phenotypic analysis of five temperature-sensitive mutations in the second largest subunit of vaccinia virus DNA-dependent RNA polymerase. 229 48

The DNA-dependent RNA polymerase of vaccinia virus contains 8 to 10 virus-encoded polypeptides. We have mapped the gene encoding an 18-kilodalton RNA polymerase subunit to D7R, the seventh open reading frame of the HindIII D genomic subfragment. Localization of this gene was achieved by using antibody to the purified RNA polymerase for immunoprecipitation of the in vitro translation products of in vivo-synthesized early mRNA selected by hybridization to cloned DNA fragments. The identification was confirmed by translation of D7R transcripts made in vitro with bacteriophage T7 RNA polymerase. The phenotypes of two previously isolated conditionally lethal temperature-sensitive mutants that map to D7R (J. Seto, L. M. Celenza, R. C. Condit, and E. G. Niles, Virology 160:110-119, 1987) are consistent with an essential role of this subunit in late transcription. This polymerase gene, designated rpo18, predicts a polypeptide of 161 amino acids with a molecular mass of 17,892. The rpo18 gene is transcribed early in infection, even though the 5'-TAAATG-3' motif, which is conserved among many genes of the late class, is present near the RNA start site. Characterization of the 5' end of the early transcript by several different methods, including cDNA cloning, revealed a poly(A) leader with up to 14 adenylate residues, whereas only 3 are present in the corresponding location of the DNA template. Similar but somewhat longer poly(A) leaders have previously been observed in mRNAs of late genes. We noted a TAAATG motif near the initiation site of several other early genes, including the viral DNA polymerase, and carried out additional experiments to demonstrate that their early transcripts also have 5' poly(A) leaders. Thus, formation of the poly(A) leader is not exclusively a late function but apparently depends on sequences around the transcription initiation site.
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PMID:Identification of the vaccinia virus gene encoding an 18-kilodalton subunit of RNA polymerase and demonstration of a 5' poly(A) leader on its early transcript. 233 25

The DNA replication requirement for vaccinia virus late gene expression was mimicked by transfecting a late promoter-controlled reporter gene into infected cells in the presence of a DNA synthesis inhibitor. This late promoter activation block was overcome by cotransfecting either naked linear vaccinia virion DNA or three cloned viral genes encoding trans-activator polypeptides of 17, 26, and 30 kd. These newly identified trans-activator genes were independently transcribed only from replicated or transfected DNA. These data suggest a regulatory cascade in which the parental viral genome serves as a template for the RNA polymerase and early promoter-specific transcription factors that are packaged in the infectious particle; the newly replicated DNA is accessible to sequentially synthesized intermediate promoter- and late promoter-specific trans-activators.
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PMID:Role of DNA replication in vaccinia virus gene expression: a naked template is required for transcription of three late trans-activator genes. 234 16

Eucaryotic transcription factors that stimulate RNA polymerase II by increasing the efficiency of elongation of specifically or randomly initiated RNA chains have been isolated and characterized. We have identified a 30-kilodalton (kDa) vaccinia virus-encoded protein with apparent homology to SII, a 34-kDa mammalian transcriptional elongation factor. In addition to amino acid sequence similarities, both proteins contain C-terminal putative zinc finger domains. Identification of the gene, rpo30, encoding the vaccinia virus protein was achieved by using antibody to the purified viral RNA polymerase for immunoprecipitation of the in vitro translation products of in vivo-synthesized early mRNA selected by hybridization to cloned DNA fragments of the viral genome. Western immunoblot analysis using antiserum made to the vaccinia rpo30 protein expressed in bacteria indicated that the 30-kDa protein remains associated with highly purified viral RNA polymerase. Thus, the vaccinia virus protein, unlike its eucaryotic homolog, is an integral RNA polymerase subunit rather than a readily separable transcription factor. Further studies showed that the expression of rpo30 is regulated by dual early and later promoters.
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PMID:Identification of rpo30, a vaccinia virus RNA polymerase gene with structural similarity to a eucaryotic transcription elongation factor. 239 97

Full-length cDNA copies of mRNAs coding for the matrix (M) proteins of vesicular stomatitis virus and its mutant tsO23(III) were cloned in pBSM13- (BlueScribe). The authenticity of these clones was demonstrated by restriction enzyme mapping, DNA sequencing, and in vitro transcription and translation to identify the two M proteins by Western immunoblotting with epitope-specific monoclonal antibodies. Site-directed mutants were constructed by primer extension of synthetic oligodeoxynucleotides with one or two nucleotide changes to alter the glycine at amino acid 21 of the wild-type (wt) M gene to glutamic acid, alanine, or proline. Similarly, a revertant was created in the M gene of mutant tsO23 by a Glu-21----Gly substitution. A series of wt- and mutant-M-gene chimeras was also constructed to create mutant and revertant clones with Leu----Phe and His----Tyr alterations at amino acids 111 and 227, respectively. We then moved the wt and tsO23 M genes and their site-specific mutants and chimeras cloned in pBSM13- into the eucaryotic expression vector pTF7 directed by the T7 bacteriophage RNA polymerase of the vaccinia virus recombinant vTF1-6,2. Western blot analysis of the M proteins transiently expressed in CV-1 cells by plasmids carrying M genes altered at amino acid 21 revealed that the critical antigenic determinant (epitope 1) is expressed only by the Gly-21 M protein and not by Glu-21, Ala-21, or Pro-21 M proteins. Of particular interest is an apparent conformational change, evidenced by slightly but significantly retarded electrophoretic migration, in plasmid-expressed M proteins with amino acids substituted for glycine at position 21. The glutamic acid at position 21 of tsO23 is not responsible for its temperature-sensitive phenotype, because a tsO23 revertant plasmid with glycine substituted at position 21 fails to rescue tsO23 virus in cells infected at the restrictive temperature; conversely, plasmids expressing wt M protein with substitutions of glutamic acid, alanine, or proline at position 21 are just as effective in marker rescue of tsO23 as is the Gly-21 wt M protein. Marker rescue experiments with wt- and mutant-M-gene chimeras support the hypothesis of K. Morita, R. Vanderoef, and J. Lenard (J. Virol. 61:256-263, 1987) that the temperature-sensitive phenotype of tsO23 is due to a phenylalanine substituted for leucine at amino acid 111, rather than the His-227----Tyr substitution or the Gly-21----Glu substitution, which independently accounts for the loss of epitope 1 in the mutant M protein of tsO23.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Site-specific mutations in vectors that express antigenic and temperature-sensitive phenotypes of the M gene of vesicular stomatitis virus. 245 88

Cytoplasmic extracts made from HeLa cells that have been harvested late after infection with vaccinia virus are capable of specifically transcribing templates containing vaccinia virus late-gene promoters. We applied such an extract to a phosphocellulose column and eluted the proteins with a series of buffers containing successively higher concentrations of NaCl. None of three column fractions alone was capable of specific transcription of a late-gene template. However, specific transcriptase activity could be reconstituted by mixing column fractions, with maximal activity seen when all three fractions were present. The activities present in all fractions were heat labile, resistant to micrococcal nuclease, and present only in extracts from vaccinia virus-infected cells. A quantitative complementation assay was used to further purify one factor, named VLTF-1, over subsequent columns of DEAE-cellulose and hydroxylapatite. VLTF-1 was separated from endogenous RNA polymerase, was a late-promoter-specific transcription factor, and had a sedimentation rate consistent with an apparent Mr of 45,000. The RNA polymerase-containing fraction was not only necessary for transcription with a late-promoter template but alone was capable of specifically transcribing a vaccinia virus early-gene promoter. A further difference between early and late gene transcription in this system was in the ability of the ATP analog beta-8-imidoadenosine-5'-triphosphate (AMP-PNP) to substitute for ATP in supporting specific transcription of only the late-promoter template. The system reconstituted from the various fractions retained the ability to produce the novel poly(A) sequence found on the 5' end of vaccinia virus late messages.
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PMID:Identification of factors specific for transcription of the late class of vaccinia virus genes. 247 68

We have analyzed the structure and stability of RNA synthesized by bacteriophage T7 RNA polymerase in mammalian cells. The T7 polymerase, expressed by a recombinant vaccinia virus, transcribed the Escherichia coli lacZ gene flanked by T7 promoter and terminator signals. The lacZ gene cassette was introduced into infected cells within either a transfected plasmid or a second recombinant vaccinia virus. The T7-lacZ transcripts, which had a half-life of approximately 75 minutes, represented approximately 30% of total cytoplasmic RNA after a 24 hour period. The latter estimation indicated a disparity between the levels of lacZ RNA and beta-galactosidase synthesis. Analysis of the T7 transcripts indicated that they were initiated correctly but that only 5 to 10% contained terminal cap structures, providing an explanation for the low translatability of the RNA. Since the 5' end of the T7 transcripts can form a stem-loop structure that might interfere with capping by vaccinia virus RNA guanylyltransferase, as well as ribosome binding and scanning, a similar vector lacking such sequences was constructed. In vitro experiments demonstrated that T7 RNA polymerase transcribed both templates with similar efficiency and that the RNA lacking the potential to form the stem-loop was capped more rapidly by the purified vaccinia virus enzyme. Nevertheless, when the stem-loop was removed, beta-galactosidase was not expressed in infected cells; moreover, no T7 transcripts could be detected, suggesting that the RNA was not made or more likely was degraded during or shortly after synthesis. There is previous evidence that vaccinia virus RNA guanylyltransferase is associated with the viral transcription complex, thereby allowing RNA synthesis and capping to occur concurrently. We suggest that a lack of coupling between the vaccinia viral RNA guanylyltransferase and bacteriophage T7 RNA polymerase delays capping of T7 transcripts and that, under these conditions, the 5'-terminal double-stranded stem is required to stabilize the nascent RNA against degradation. Although deletion of the 3' palindromic sequence specifying T7 transcriptional termination from the expression cassette resulted in RNA of more heterogeneous lengths, neither the apparent turnover rate nor translation of the RNAs was diminished appreciably.
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PMID:Structure and stability of mRNA synthesized by vaccinia virus-encoded bacteriophage T7 RNA polymerase in mammalian cells. Importance of the 5' untranslated leader. 249 59

Functional elements of a vaccinia virus early promoter were characterized by making a complete set of single nucleotide substitutions, as well as more complex mutations, and assaying their effects on gene expression. Synthetic oligonucleotides, based primarily on the sequence of the 7.5-kD early promoter, were inserted into a plasmid vector containing the lacZ gene of Escherichia coli flanked by sequences from the thymidine kinase (TK) gene of vaccinia virus. The lacZ gene, under control of the synthetic promoter, was introduced into the vaccinia virus genome at the TK locus by homologous recombination, and each of the 331 different recombinant viruses thus obtained was assayed for beta-galactosidase expression. The relative amounts and precise 5' ends of lacZ mRNAs specified by a subset of the recombinants were determined by primer extension. Many promoters were tested for their ability to direct specific transcription in vitro. A generally good correlation was noted between measurements of promoter strength estimated by beta-galactosidase expression, primer extension of in vivo mRNA and transcription in vitro. A relatively simple picture emerged from the analysis. The early promoter consists of a 16 base-pair critical region, in which most single nucleotide substitutions have a major effect on expression, separated by 11 base-pairs of a less critical T-rich sequence from a seven base-pair region within which initiation with a purine usually occurs. For the critical region of the 7.5-kD promoter, AAAAgTaGAAAataTA, any substitution of an upper-case nucleotide reduced expression, usually drastically, whereas certain substitutions of lower-case nucleotides maintained or significantly enhanced expression. On the basis of this analysis, the wide range of activities of natural promoters could be attributed to the presence of one or more non-optimal nucleotides in the critical region. Moreover, single nucleotide substitutions in such promoters had the predicted enhancing effects. Most mutations in the critical region of the 7.5-kD promoter behaved independently, but some nucleotide substitutions compensated for potentially detrimental nucleotides at other positions. Promoters substantially stronger than any natural ones examined were constructed by combining several up-mutations within the critical region of the 7.5-kD promoter and by repeating the critical region sequence. Like the TATA box of eukaryotic RNA polymerase II promoters, the critical region specifies the site of transcriptional initiation.
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PMID:Structure of vaccinia virus early promoters. 251 86

Functional elements of vaccinia virus late promoters were characterized by mutagenesis. Synthetic oligonucleotides were inserted into a plasmid vector containing the lacZ gene of Escherichia coli flanked by sequences from the thymidine kinase (TK) gene of vaccinia virus. The lacZ gene, under control of the synthetic promoter, was introduced into the vaccinia virus genome at the TK locus by homologous recombination, and each of the 122 recombinants thus obtained was assayed for beta-galactosidase expression. The relative amounts and 5' ends of lacZ mRNAs specified by a subset of the recombinants were determined by primer extension. The analysis indicated that late promoters may be considered in terms of three regions; an upstream sequence of about 20 base-pairs, rich in T and A residues, separated by a spacer region of about six base-pairs from a highly conserved (-1)TAAAT(+4) element within which transcription initiates. All single nucleotide substitutions within the three A residues of the TAAAT, as well as the addition of a fourth A residue, caused drastic reductions in promoter strength. All substitutions of the T residues at -1 and +4 were also detrimental to promoter activity, to an extent that depended on the strength of the promoter as determined by the upstream sequence. mRNA synthesis appeared to initiate within the three A residues regardless of promoter strength. The 5'-poly(A) leader, which is a unique feature of poxvirus late mRNAs, was diminished in length when either of the T residues at -1 and +4 was mutated, was absent or limited to a few nucleotides when any of the three A residues was substituted, but was unaffected by changes outside the TAAAT sequence. The data are consistent with a model for the generation of the normal 5'-poly(A) leader by an RNA polymerase slippage mechanism requiring three consecutive A residues. Single nucleotide substitutions within the six base-pairs upstream and three base-pairs downstream from the TAAAT sequence had modest effects on promoter strength. The most and least favourable changes led to a fourfold increase and an eightfold decrease in activity, respectively. Sequences further upstream were essential for late promoter function; tracts of T or A residues enhanced expression up to 20-fold, the former conferring much greater activity. Highest expression was obtained with a tract of 18 or 20 T residues.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Structure of vaccinia virus late promoters. 251 87

Pro-opiomelanocortin (POMC) was expressed in CV-1 (green monkey kidney) cells using a vaccinia virus transient expression system [(1986) Proc. Natl. Acad. Sci. USA 83, 8122]. The system involved infection of cells with a recombinant vaccinia virus carrying the T7 RNA polymerase gene and transfection with a plasmid containing the mouse POMC sequence flanked by the T7 RNA polymerase promoter at its 5'-end and the T7 RNA polymerase terminator at its 3'-end. Assay of the medium from transfected cells showed that 1-2 micrograms of immunoreactive ACTH was produced/10(6) cells. Analysis of the same medium by SDS-PAGE/Western blots revealed a band of 30-36 kDa, which was immunostained with both ACTH and beta-endorphin antisera. Labeling the transfected cells with [3H]Arg, followed by immunoprecipitation and SDS-PAGE showed the synthesis of a major peak of POMC, 33 kDa. Purified [3H]POMC expressed by CV-1 cells was cleaved in vitro by bovine intermediate lobe secretory vesicle pro-opiomelanocortin-converting enzyme to ACTH intermediates (19-25 kDa), beta-lipotropin and beta-endorphin. Thus, this work has demonstrated a technique for expressing microgram quantities of prohormones in mammalian cells, suitable for use as substrates for prohormone-converting enzymes in vitro.
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PMID:Production of pro-opiomelanocortin (POMC) by a vaccinia virus transient expression system and in vitro processing of the expressed prohormone by POMC-converting enzyme. 254 89


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