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 inhibitor sensitivity and functional domains of recombinant encephalomyocarditis (EMC) virus RNA-dependent RNA polymerase (3Dpol) have been extensively analyzed. The inhibitor profiles of EMC virus 3Dpol and Escherichia coli DNA-dependent RNA polymerase are distinct, and experiments with substrate analogs indicate that EMC virus 3Dpol lacks reverse transcriptase activity. Twenty amino acid substitutions were engineered in EMC virus 3Dpol based on sequence alignments of viral RNA-dependent RNA polymerases that identified conserved amino acid residues within motifs. Ten out of 17 conservative substitutions within the four most conserved motifs reduced the RNA polymerase activity of the mutants to 0-6% of the activity of the wild-type enzyme, demonstrating the importance of these amino acids in the structure and/or function of EMC virus 3Dpol. Remarkably, 5 of the 10 mutations in EMC virus 3Dpol which had the most drastic effect on its RNA polymerase activity (D240E, S293T, N302Q, G332A, and D333E) were found to correspond to active site residues in E. coli DNA-dependent DNA polymerase I (Klenow). Our results reveal that a basic structural and functional framework is conserved in the most distantly related classes of nucleic acid polymerases and demonstrate the validity of modeling the active site of an RNA-dependent RNA polymerase on the known structure of a DNA polymerase.
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PMID:Point mutations which drastically affect the polymerization activity of encephalomyocarditis virus RNA-dependent RNA polymerase correspond to the active site of Escherichia coli DNA polymerase I. 131 53

Inhibitory effect of 3'-azide-3'deoxy-ribavirin-5'-triphosphate on activity of RNA-dependent RNA polymerase from influenza A virus as well as on DNA-dependent RNA polymerase II from mice liver nuclei was studied. The drug inhibited effectively RNA synthesis catalyzed by these enzymes, whereas its most selective inhibitory action was found in reaction with RNA polymerase from influenza A virus.
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PMID:[Inhibitory effect of 3'-azido-3'-azido-3'-deoxy- ribavirin-5'-triphosphate on RNA synthesis catalyzed by RNA polymerase from influenza A virus and by cellular DNA-dependent RNA polymerase II]. 247 5

Replication of the infectious RNA genome of poliovirus is accomplished in cells by the viral RNA polymerase through negative-strand RNA intermediates. Full-length negative-strand poliovirus RNA was synthesized in vitro by transcription of infectious poliovirus cDNA with bacteriophage SP6 DNA-dependent RNA polymerase. When provided with this negative-strand RNA as template, the poliovirus RNA-dependent RNA polymerase synthesized full-length positive-strand molecules. The positive-strand RNAs synthesized in vitro were infectious when transfected into HeLa cells. In contrast, positive-strand copies of poliovirus RNA synthesized in vitro by SP6 polymerase, using a poliovirus cDNA template, were not infectious. Production of infectious positive-strand RNA by the poliovirus polymerase was not observed when magnesium or negative-strand RNA template was omitted from the reaction mixture. Infectivity of the product RNA was not destroyed by DNase treatment. The specific infectivity in HeLa cells of in vitro-synthesized positive-strand RNA was 4 X 10(4) plaque-forming units/micrograms of RNA.
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PMID:In vitro synthesis of infectious poliovirus RNA. 300 3

Partially purified DNA-dependent RNA polymerase from infectious vaccinia virus particles exhibits the following two activities: 1) specific transcription of double-stranded DNA templates containing vaccinia early promoters and 2) nonspecific transcription of single-stranded DNA templates. After further purification of the RNA polymerase, specific transcriptase activity was selectively diminished suggesting the loss of a transcription factor. In agreement with the latter hypothesis, transcriptase activity could be reconstituted by mixing the purified RNA polymerase with certain column fractions. A quantitative complementation assay was developed and used to locate the transcription factor during successive column chromatography steps. The factor eluted as a single peak of activity from single strand DNA-cellulose and phosphocellulose columns. An observation that the transcription factor binds specifically to vaccinia early promoter sequences was exploited in the final affinity chromatography steps. The purified factor was separated from all previously identified vaccinia enzymes and contained two polypeptides of Mr 77,000 and 82,000. A DNA-dependent ATPase activity also copurified with the transcription factor. Although a single template was used for assays during isolation, the purified factor stimulated transcription of three other early genes by 20-30-fold suggesting that it has a general role in conferring promoter specificity for initiation of early transcription.
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PMID:Purification of a factor required for transcription of vaccinia virus early genes. 339 40

1. The RNA-dependent RNA polymerase from Halobacterium cutirubrum was purified to electrophoretic homogeneity. 2. It requires a single-stranded molecule of RNA or polyribonucleotide as template. 3. Nearest-neighbour analyses of the products formed on random poly(A,U) or alternating poly(A-U) templates and base analysis of the product of synthesis directed by wheat-germ RNA prove that the template is copied accurately. 4. The enzyme initiates new chains with purine ribonucleoside triphosphates. 5. Sucrose-density-gradient analysis of the product indicates that it has a size distribution similar to that of the template. 6. Preliminary amino acid analysis of the RNA-dependent polymerase shows that it contains much less serine than either of the subunits of H. cutirubrum DNA-dependent RNA polymerase. 7. The RNA-dependent enzyme is unable to substitute for either subunit of the DNA-dependent polymerase, and both the latter are devoid of RNA-dependent activity.
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PMID:Purification and properties of the ribonucleic acid-dependent ribonucleic acid polymerase from Halobacterium cutirubrum. 463 91

1. Conditions have been established for the estimation of molecular weights of proteins by analytical gel filtration and sucrose-density-gradient centrifugation in 2.5m-potassium chloride-1m-sodium chloride; Halobacterium cutirubrum polynucleotide phosphorylase, DNA-dependent RNA polymerase and RNA-dependent RNA polymerase have been studied by these methods. 2. The RNA-dependent polymerase has also been studied by density-gradient centrifugation in the absence of salt. 3. All three proteins are of unusually low molecular weight compared with similar enzymes from non-halophilic bacteria.
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PMID:Nucleic acid enzymology of extremely halophilic bacteria. Gel-filtration and density-gradient-centrifugation studies of the molecular weights of Halobacterium cutirubrum polynucleotide phosphorylase and deoxyribonucleic acid- and ribonucleic acid-dependent ribonucleic acid polymerases. 511 75

The multiplication of murine coronavirus strains A59 or JHM in Sac(-) cells was unaffected by the presence of alpha-amanitin at concentrations which inhibited the host cell DNA-dependent RNA polymerase activity. In cells infected with the A59 virus strain, actinomycin D-resistant RNA synthesis could readily be detected by pulse-labelling with [3H]uridine; this virus-specific RNA synthesis was not induced in the presence of the protein synthesis inhibitor anisomycin. A new RNA-dependent RNA polymerase activity was detected in the large particle fraction of A59 virus-infected cells. Optimal conditions for enzyme activity in vitro were established. Maximum activity occurred 5 h after infection, coincident with the peak of virus-specific RNA synthesis detected by pulse-labelling in vivo.
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PMID:RNA-dependent RNA polymerase activity in murine coronavirus-infected cells. 629 95

Two catalytic functions were required, minimally, for the appearance of DNA in evolution: a ribonucleotide reductase (RNR) and a reverse transcriptase (RT). If one accepts the explanatory strength of the RNA world model, it is clear that DNA molecules arose in the RNA world at some stage during the early evolution of cells. I suggest that competition for limited and valuable resources such as nucleotides, amino acids, and sugars made an early appearance among RNA cells, RNA viruses, viroids, and RNA plasmids. Structural and functional similarities between the different types of polymerases favor the simple hypothesis that the first RTs were RNA polymerase mutants that preferentially joined together preexisting deoxyribonucleotide triphosphates (dNTPs) using RNA templates. What was the role of dNTPs inside cells before DNA was synthesized and tested by natural selection? The oxygen atom that is removed by the reductase is of crucial importance to many ribozyme functions, since the 2'-OH is a strong nucleophile that forms transitional states during catalysis. Consequently, a RNR may have been used by cellular parasites to inhibit ribozyme action. Thus, DNA may have been, initially, an inert by-product of retrotranscription in lineages that acquired RTs and could synthesize DNA molecules using cellular RNA templates to detoxify the intracellular environment. DNA was useless as template until a transcriptase (DNA-dependent RNA polymerase) evolved that could copy (-)DNA to reconstitute the (+)RNA genome, indeed a successful way of confronting ribonuclease threats in the RNA world.
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PMID:Inhibition of ribozymes by deoxyribonucleotides and the origin of DNA. 969 60

Repetitive elements flanked by exons 2 and 3 of the human transaldolase gene, thus termed transaldolase-associated repetitive elements, TARE, were identified in human DNA. Nonpolyadenylated TARE transcripts were detected by Northern blot analysis and cloned by reverse transcriptase-mediated polymerase chain reaction from human T lymphocytes. A dominant 1085-nucleotide long transcript, TARE-6, contained two adjacent Alu elements, a right monomer and a complete dimer, oriented opposite to the direction of transcription of the transaldolase gene. Reverse transcriptase-polymerase chain reaction and in vitro transcription analyses showed that transcription of TARE-6 proceeded in the orientation of the RNA pol III promoter of the Alu dimer and opposite to the orientation of the TAL-H gene. TAREs lacking RNA polymerase III promoter showed no transcriptional activity. In vitro transcription of TARE-6 was resistant to 1 microg/ml alpha-amanitin but sensitive to 100 microg/ml alpha-amanitin and tagetitoxin, suggesting involvement of RNA polymerase III. TAREs in both the transaldolase and HSAG-1 genomic loci were surrounded by TA target site duplications. Homologies between transaldolase and HSAG-1 break off internally at splice donor and acceptor sites. The results suggest RNA polymerase III-mediated transcription of TARE may be a source of repetitive elements, contributing to distinct genes and thus shaping the human genome.
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PMID:Human transaldolase-associated repetitive elements are transcribed by RNA polymerase III. 1070 96

The influenza A virus, a severe pandemic pathogen, has a segmented RNA genome consisting of eight single-stranded RNA molecules. The 5' and 3' ends of each RNA segment recognized by the influenza A virus RNA-dependent RNA polymerase direct both transcription and replication of the virus's RNA genome. Promoter binding by the viral RNA polymerase and formation of an active open complex are prerequisites for viral replication and proliferation. Here we describe the solution structure of this promoter as solved by multidimensional, heteronuclear magnetic resonance spectroscopy. Our studies show that the viral promoter has a significant dynamic nature and reveal an unusual displacement of an adenosine that forms a novel (A-A) x U motif and a C-A mismatch stacked in a helix. The characterized structural features of the promoter imply that the specificity of polymerase binding results from an internal RNA loop. In addition, an unexpected bending (46 +/- 10 degrees ) near the initiation site suggests the existence of a promoter recognition mechanism similar to that of DNA-dependent RNA polymerase and a possible regulatory function for the terminal structure during open complex formation.
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PMID:Structural features of an influenza virus promoter and their implications for viral RNA synthesis. 1155 8


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