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

---

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

A cytoplasmic, microsomal bound RNA-dependent RNA polymerase has been purified 2500-fold from rabbit reticulocyte lysates. The synthesis of RNA with the purified enzyme is absolutely dependent on the addition of an RNA template. The best template is hemoglobin messenger RNA, while bacteriophage RNA and poly(A,G) are less active, and DNA is completely inactive as a template. With poly(A,G) as a template, only UTP and CTP are incorporated into polynucleotide chains, indicating that the RNA polymerase is an RNA replicase and not a terminal transferase. With messenger RNA as a template, all four ribonucleoside triphosphates are required for maximal activity. The RNA-dependent RNA polymerase reaction is extremely sensitive to low concentrations of heme, rifamycin AF/013, and ribonuclease and resistant to actinomycin D and DNase. The discovery of RNA-directed RNA synthesis in reticulocytes offers an additional site for control of gene expression in mammalian cells and provides a possible mechanism for amplification of the expression of specific genes.
...
PMID:Reticulocyte RNA-dependent RNA polymerase. 451 33

Soluble enzyme fractions from uninfected Escherichia coli convert M13 and varphiX174 viral single strands to their double-stranded replicative forms. Rifampicin, an inhibitor of RNA polymerase, blocks conversion of M13 single strands to the replicative forms in vivo and in vitro. However, rifampicin does not block synthesis of the replicative forms of varphiX174 either in vivo or in soluble extracts. The replicative form of M13 synthesized in vitro consists of a full-length, linear, complementary strand annealed to a viral strand. The conversion of single strands of M13 to the replicative form proceeds in two separate stages. The first stage requires enzymes, ribonucleoside triphosphates, and single-stranded DNA; the reaction is inhibited by rifampicin. The macromolecular product separated at this stage supports DNA synthesis with deoxyribonucleoside triphosphates and a fresh addition of enzymes; ribonucleoside triphosphates are not required in this second stage nor does rifampicin inhibit the reaction. We presume that in the first stage there is synthesis of a short RNA chain, which then primes the synthesis of a replicative form by a DNA polymerase.
...
PMID:RNA synthesis initiates in vitro conversion of M13 DNA to its replicative form. 455 37

In a coupled system consisting of RNA polymerase and DNA polymerase I of Escherichia coli, the four deoxyribo- and the four ribonucleoside triphosphates, and DNA of bacteriophage f1 as template, DNA synthesis depends on the concomitant synthesis of RNA. Over a wide range of concentrations of the two polymerases, RNA synthesis was unaffected by the simultaneous synthesis of DNA, whereas the rate of DNA synthesis depended on the level of RNA synthesis. In the coupled reaction, RNA synthesis starts immediately at a high rate, which subsequently decreases, whereas DNA synthesis starts after a lag and its rate increases as the reaction proceeds. Upon addition of rifampicin, the rate of RNA synthesis falls abruptly, while that of DNA declines only gradually. The base composition of the DNA synthesized in the coupled reaction is complementary to that of f1 DNA template. It is suggested that the RNA synthesized by the RNA polymerase serves as a primer rather than as a template for the DNA polymerase.
...
PMID:Coupling of replication to transcription in vitro. 455

Conversion of single-stranded DNA of phage varphiX174 to the double-stranded replicative form in Escherichia coli uses enzymes essential for initiation and replication of the host chromosome. These enzymes can now be purified by the assay that this phage system provides. The varphiX174 conversion is distinct from that of M13. The reaction requires different host enzymes and is resistant to rifampicin and streptolydigin, inhibitors of RNA polymerase. However, RNA synthesis is essential for varphiX174 DNA synthesis: the reaction is inhibited by low concentrations of actinomycin D, all four ribonucleoside triphosphates are required, and an average of one phosphodiester bond links DNA to RNA in the isolated double-stranded circles. Thus, we presume that, as in the case of M13, synthesis of a short RNA chain primes the synthesis of a replicative form by DNA polymerase. Initiation of DNA synthesis by RNA priming is a mechanism of wide significance.
...
PMID:Initiation of DNA synthesis: synthesis of phiX174 replicative form requires RNA synthesis resistant to rifampicin. 456 Jun 96

varphiX174 and M13 (fd) single-stranded circular DNAs are converted to their replicative forms by extracts of E. coli pol A1 cells. We find that the varphiX174 DNA-dependent reaction requires Mg(++), ATP, and all four deoxynucleoside triphosphates, but not CTP, UTP, or GTP. This reaction also involves the products of the dnaC, dnaD, dnaE (DNA polymerase III), and dnaG genes, but not that of dnaF (ribonucleotide reductase). The in vitro conversion of fd single-stranded DNA to the replicative form requires all four ribonucleoside triphosphates, Mg(++), and all four deoxynucleoside triphosphates. The reaction involves the product of gene dnaE but not those of genes dnaC, dnaD, dnaF, or dnaG. The reaction with fd DNA is inhibited by rifampicin or antibody to RNA polymerase, while the reaction with varphiX174 DNA is not affected by either. With the varphiX174 DNA-dependent reaction, activities have been detected that specifically complement extracts of dnaA, dnaB, dnaC, dnaD, or dnaG mutants.
...
PMID:Conversion of phiX174 and fd single-stranded DNA to replicative forms in extracts of Escherichia coli. 456 9

The effects of dinucleoside monophosphates on the transcription of phage T4 DNA by E. coli RNA polymerase have been examined at various concentrations of the sigma subunit and extremely low concentration of ribonucleoside triphosphate. The following conclusions were reached: (i) Labeled specific dinucleoside monophosphates are incorporated as chain initiators. (ii) When the ratio of sigma factor to core enzyme is small, there is a general stimulation by most 5'-guanosyl dinucleoside monophosphates. (iii) When the ratio is increased or holoenzyme is present, ApU, CpA, UpA, and GpU are the most effective stimulators. (iv) At high concentrations of sigma factor, only certain adenosine-containing dinucleoside monophosphates (ApU, CpA, UpA, and ApA) stimulate the reaction. (v) Competition hybridization studies indicate that the RNAs stimulated by dinucleoside monophosphates (ApU, CpA, UpA, and GpU) are of the T4 "early" type. (vi) Studies involving both combinations of stimulatory dinucleoside monophosphates and competitive effects of these compounds on chain initiation by ATP and GTP suggest that the stimulatory dinucleoside monophosphates act as chain initiators and may recognize part of a continuous sequence in a promoter region. Studies based on the incorporation of (3)H-labeled stimulatory dinucleoside monophosphates support the above conclusions.
...
PMID:RNA initiation with dinucleoside monophosphates during transcription of bacteriophage T4 DNA with RNA polymerase of Escherichia coli. 456 32

Cytological preparations of Drosophila polytene chromosomes serve as templates for RNA synthesis carried out by exogenous RNA polymerase (Escherichia coli). Incorporation of labeled ribonucleoside triphosphates into RNA may be observed directly by autoradiography. Because of the effects of rifampicin, actinomycin D, ribonuclease, high salt, and the requirement for all four nucleoside triphosphates, we conclude that the labeling observed over chromosomes is due to DNA-dependent RNA polymerase activity. Using this method, one can observe RNA synthesis in vitro on specific chromosome regions due to the activity of exogenous RNA polymerase. We find that much of the RNA synthesis in this system occurs on DNA sequences which appear to be in a nondenatured state.
...
PMID:RNA synthesis by exogenous RNA polymerase on cytological preparations of chromosomes. 457 95

Purified vaccinia virions contain an enzyme that incorporates methyl groups from S-adenosylmethionine into viral RNA synthesized by the core-associated DNA-dependent RNA polymerase. This incorporation, by partially disrupted virions, was dependent on the presence of all four ribonucleoside triphosphates and Mg(++) and was inhibited by actinomycin D. At saturation, 2.3 methyl groups were incorporated per 1000 nucleotides. The methyl-labeled RNA product was sensitive to alkali and ribonucleases and hybridized to filters containing immobilized poly(U) or vaccinia DNA. The methyl groups were not located on the 3'-terminal polyadenylate sequence, nor were they randomly distributed along the RNA chain. The lability of a large portion of the methyl groups to perchloric acid digestion was consistent with an O-methyl linkage, and the chromatographic properties of the alkali-digested material suggested that either the 5'-terminus or up to three consecutive internal nucleotides were methylated. Methylation probably occurs at the macromolecular level, since added vaccinia RNA was a suitable substrate. The failure of heterologous rRNA and tRNA species as well as homopolyribonucleotides to act as substrate suggested that a specific sequence might be required.
...
PMID:Methylation of newly synthesized viral messenger RNA by an enzyme in vaccinia virus. 460 8

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.
...
PMID:Purification and properties of the ribonucleic acid-dependent ribonucleic acid polymerase from Halobacterium cutirubrum. 463 91

An enzymatic activity which synthesized oligo(A) in vitro was found in highly purified reovirus. The poly(A) polymerase activity was dependent on Mn(2+) and utilized only ATP, whereas the virion-associated RNA polymerase required all four ribonucleoside triphosphates and Mg(2+). Oligo(A) synthesis was demonstrated with complete virions and infectious subviral particles derived from virus by limited chymotrypsin digestion but not with cores, a product of extensive chymotrypsin digestion of virus. The enzymatic product and the oligo(A) from purified virions were isolated by binding to oligo(dT)-cellulose columns. Most of the in vitro product was similar in size and structure to the oligo(A) from purified virions by the criteria of gel electrophoresis, DEAE-cellulose chromatography, end-group analysis, and sensitivity to RNase. The evidence suggests that oligo(A) synthesis is mediated by the poly(A) polymerase during a late step in viral morphogenesis and may result from an alternative activity of the virion-associated transcriptase.
...
PMID:Poly(A) polymerase activity in reovirus. 483 12


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---