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)

Class III RNA polymerases purified from the murine plasmacytoma MOPC 315 and from Xenopus laevis ovaries were compared. The subunit structures of the chromatographically distinct murine enzymes IIIA and IIIB were indistinguishable and were remarkably similar to that of the amphibian enzyme III. The plasmacytoma class III RNA polymerases were also compared with purified plasmacytoma RNA polymerases I and II. Sedimentation studies indicated that RNA polymerase III si significantly larger than RNA polymerase II, which is slightly larger than RNA polymerase I. Structural analyses showed that the molecular weights of the large subunits present in the class III enzymes (138,000 and 155,000) differ from those of the class II enzymes (140,000 and either 170,000, 205,000, or 240,000) and from those of the class I enzymes (117,000 and 195,000). Some low-molecular-weight subunits are also unique to each enzyme class. These results clearly distinguish the class I, II, and III enzymes on a structural basis. In addition, polypeptides of molecular weight 29,000 and 19,000 were found in all enzyme classes, a polypeptide of molecular weight 52,000 was found only in class I and III enzymes, and a polypeptide of molecular weight 41,000 was found only in class II and III enzymes. These findings are discussed in terms of the function and regulation of the RNA polymerases.
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PMID:Distinct molecular structures of nuclear class I, II, and III DNA-dependent RNA polymerases. 105 9

Bacteriphage T7 RNAs have been fractionated on preparative polyacrylamide gels. The in vitro coding capacities of the RNAs have been determined by translation of the RNAs in a cell-free system and analysis of the polypeptide products on sodium dodecyl sulfate polyacrylamide slab gels. The T7 early RNAs are fractionated according to their molecular weight and without intermolecular aggregation. Fractionation of the late T7 RNAs gives rise to 10 major RNAs, ranging in size from 0.29 X 10(6) daltons to 2.05 X 10(6) daltons. Five of these RNAs are polycistronic and overlapping species are present for some T7 proteins. In particular, the gene 10 protein, the major capsid protein, is translated from at least three mRNAs. The smallest of these gene 10 mRNAs is monocistronic. A second gene 10 mRNA also codes for the gene 9 protein, and a third gene 10 mRNA codes for both gene 8 and gene 9 proteins. The T7 gene 3.5 protein, a T7 lytic enzyme, is also translated from several differently sized mRNAs. Comparison with published data on in vitro transcription by T7 RNA polymerase suggestes that transcription from multiple initiation sites and cleavage of larger precursors are both involved in generating the late T7 transcripts we observe. The overlapping mode of transcription could serve to amplify certain gene products.
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PMID:Detection of polycistronic and overlapping bacteriophage T7 late transcripts by in vitro translation. 106 Nov 35

Escherichia coli phage Qbeta RNA replicase, an RNA-dependent RNA polymerase (RNA-dependent RNA nucleotidyltransferase), is a tetramer composed of one phage-coded polypeptide and three host-supplied polypeptides which are known to function in the biosynthesis of proteins in the uninfected host. Two of these polypeptides, protein synthesis elongation factors EF-Tu and EF-Ts, can be covalently crosslinked with dimethyl suberimidate to form a complex which lacks the ability to catalyze the known host functions catalyzed by the individual elongation factors. Using a previously developed reconstitution system we have examined the effects of crosslinking the EF-Tu-Ts complex on reconstituted replicase activity. Renaturation is significantly more efficient when exogenously added native EF-Tu-Ts is crosslinked than when it is not. Crosslinked EF-Tu-Ts can be purified from a crude crosslinked postribosomal supernatant by its ability to replace EF-Tu and EF-Ts in the renaturation of denatured Qbeta replicase. A sample of Qbeta replicase with crosslinked EF-Tu-Ts replacing the individual elongation factors was prepared. Although it lacked EF-Tu and EF-Ts activities, it could initiate transcription of both poly(C) and Qbeta RNA normally and had approximately the same specific activity as control enzyme. Denatured Qbeta replicase formed with crosslinked EF-Tu-Ts was found to renature much more rapidly than untreated enzyme and, in contrast to normal replicase, its renaturation was not inhibited by GDP. The results demonstrate that EF-Tu and EF-Ts function as complex in Qbeta replicase and do not perform their known protein biosynthetic function in the RNA synthetic reaction.
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PMID:Reconstitution of Qbeta RNA replicase from a covalently bonded elongation factor Tu-Ts complex. 106 92

The expression of bacteriophage T5-specific RNA and protein in infected cells is temporally separated into three classes: class I (preearly), class II (early), and class III (late). By immunoprecipitation techniques we have shown that T5 infection of cells leads to the synthesis of one class I polypeptide (11,000 daltons) and two class II polypeptides (90,000 and 15,000 daltons) capable of binding to the RNA polymerase of the host Escherichia coli cell. One of the class II polypeptides (90,000 daltons) is the product of gene C2, which is an essential gene product required for the initiation of class III RNA synthesis. The colicinogenic factor, ColIb, is a plasmid which prevents the normal synthesis of class II and the III bacteriophage T5-specific RNA in infected colicinogenic (ColIb+) cells. In T5-infected colicinogenic cells, only the T5 class I polypeptide is found associated with the RNA polymerase. Mutants of T5, designated T5h minus, are capable of growth on both noncolicinogenic and ColIb+ hosts. Extracts of T5h minus infected ColIb+ cells were shown to lack a small class I polypeptide (12,000 daltons) as compared to T5-infected cells. The h minus mutation, however, has no effect on the levels of the class I T5 polypeptide of similar molecular weight which is bound to the RNA polymerase. One effect of the h minus mutation is to enhance the quantities of the two class II polypeptides bound to the enzyme.
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PMID:The regulation of transcription in bacteriophage T5-infected Escherichia coli. 109 31

The inhibitory effect of the polypeptide antibiotics netropsin and distamycin A on DNA dependent nucleic acid synthesis has been shown to be related to the base composition of the template DNA. A number of natural DNA's of quite different dA-dT content as well as poly (dI-dC)-poly (dI-dC), poly (dA-dT)-poly (dA-dT), poly (dA) - poly (dT) and poly (dG) - poly (dC) has been studied as templates in DNA and in part in RNA polymerase reaction. The highest binding efficiency of netropsin existing for (dA-dT) - containing DNA polymers and the less pronounced interaction with the (dI-dC)-containing polymer shown by the melting and CD spectrral behaviour of the complexes are entirely reflected in the template inactivation. The same is evident for distamycin A. However, in contrast to netropsin the antibiotic distamycin A exhibits some binding tendency to poly (dG) - poly (dC). Binding effects of a netropsin derivative to DNA and (dA-dT) -containing polymers suggest the importance of hydrogen bonds of the peptide groups in the complex formation.
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PMID:(dA-dT) dependent inactivation of the DNA template properties by interaction with netropsin and distamycin A. 109 41

Yeast RNA polymerase A (RNA nucleotidyltransferase; nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) can be converted to a new form of enzyme, called RNA polymerase A*, which is lacking two polypeptide chains of 48,000 and 37,000 daltons. Apart from these two missing polypeptides the subunit structures of RNA polymerases A and A* are indistinguishable. RNA polymerase A* differs from the complete enzyme in its electrophoretic and chromatographic behavior, template requirements, and alpha-amanitin sensitivity. RNA polymerase A* transcribes the alternated copolymer d(A-T)n with the same efficiency as RNA polymerase A but its specific activity is greatly reduced with native calf thymus DNA as template. The transcription of a variety of synthetic templates is also altered by removal of the two polypeptide chains. RNA polymerase A* is inhibited by high concentrations of alpha-amanitin (500 mug/ml), whereas RNA polymerase A is comparatively less sensitive to the toxic peptide. The data are discussed in terms of possible roles of the two dissociable polypeptides.
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PMID:Dissociation of two polypeptide chains from yeast RNA polymerase A. 110 35

The nature of the inhibition by salt (KCl) of DNA-dependent RNA polymerase from T4 phage-infected Escherichia coli (T4 enzyme) was studied using holoenzyme preparations, core enzyme and sigma fractions obtained by phosphocellulose column chromatography, and sigma fractions further purified by gradient centrifugation in the presence and absence of 6 M urea. We showed with holoenzyme preparations that salt inhibits the formation of rifampicin-resistant preinitiation complexes. The inhibition was considerably reduced when a nonionic detergent (particularly of the Triton series) was included in the reaction mixtures. With T4 core enzyme and T4 sigma fractions together with the same fractions from uninfected cells (host enzyme fractions) and different DNA templates, we showed that the T4 sigma fraction plays a role in the salt-sensitive activity with T4 DNA. The salt sensitivity of the T4 sigma fraction was antagonized by Triton; it was not a function of sigma fractions isolated from phage cultures infected in the presence of chloramphenicol. As reported previously (Stevens, A. (1973), Biochem. Biophys. Res. Commun. 54, 488), the T4 sigma fraction inhibited the activity of host sigma when they were present together in reaction mixtures, particularly in the presence of salt. T4 sigma further purified by centrifugation in glycerol gradients had the same properties as the cruder fraction, and the T4-specific polypeptide of mol wt 10000 (Stevens, A. (1972), Proc. Natl. Acad. Sci. U.S.A. 69, 603) was found in the same fractions. If the glycerol gradients contained 6 M urea, the mol wt 10000 polypeptide was separated from the salt-stimulated sigma. Fractions containing the small polypeptide could be added back to produce the salt-inhibitory effects. The inhibitory activity of both the crude sigma fraction and the fractions containing the small polypeptide was inactivated at 65 degrees C. The results suggest that the mol wt 10000 protein is a salt-promoted inhibitor, but the small amounts of it which are present in purified fractions of the T4 enzyme have not yet allowed its isolation in large enough quantities to permit a detailed study of its properties.
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PMID:Characterization of an inhibitor causing potassium chloride sensitivity of an RNA polymerase from T4 phage-infected Escherichia coli. 110 66

Benzimidazoles are weak mutagens acting through base substitutions; they are incorporated into nucleic acids. Experiments with deoxyribohomopolymers as templates demonstrated that benzimidazole nucleoside triphosphate is polymerized by RNA polymerase only in the presence of poly dC, i.e., instead of guanine. In plasmolyzed Escherichia coli cells, benzimidazole ribonucleoside diphosphate is polymerized by polynucleotide phosphorylase and can, after blocking of the normal mRNA synthesis with actinomycin D, be used as a messenger for polypeptide formation. The addition of radioactive amino acids to this system showed that benzimidazole is not read preferentially as guanine, as would have been expected from the RNA polymerase results. Instead, the reading was position dependent and brnzimidazole is recognized (1) in the first codon position as adenine, (2) in the second as purine, and (3) in the third possibly only as base. Benzimidazole mutagenicity is thus explained as a G in equilibrium A transition.
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PMID:The molecular mechanism of benzimidazole mutagenicity: in vitro studies on transcription and translation. 110 1

Infection of Pseudomonas putida by the bacteriophage gh-L-induced the synthesis of a novel DNA-dependent RNA polymerase. This gh-L-induced RNA polymerase was purified to near homogeneity. It was shown to be distinct from the host RNA polymerase (alpha-2 beta beta sigma) physically and in respect to many of its catalytic properties. The gh-L-induced RNA polymerase was composed of a single polypeptide of approximately 98,000 molecular weight. The divalent metal ion requirement for in vitro RNA synthesis by the gh-L-polymerase could be satisified with Mg-2+, but not with Mn-2+. Rna synthesis by the gh-L polymerase was highly resistant to inhibition by rifampicin and streptolydigin but could be inhibited by relatively low concentrations of KCl or the rifamycin derivative AF/013. The structural analog of ATP, 3'-deoxyadenosine 5'-triphosphate, inhibited both the gh-L-induced and the host RNA polymerases by competing for a single binding site with ATP. The phage polymerase was extremely sensitive to this inhibitor, exhibiting an apparent K-i value (2 times 10-8 M) approximately 100 times lower than that for the host RNA polymerase. The gh-L polymerase had a highly specific template requirement for DNA from the homologous gh-L phage. It would not efficiently utilize denatured DNA templates and had only low levels of activity with pyrimidine-containing polydeoxyribonucleotide homopolymers.
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PMID:Purification and characterization of bacteriophage gh-I-induced deoxyribonucleic acid-dependent ribonucleic acid polymerase from Pseudomonas putida. 111 26

A special class of non-histone protein ("tight protein") is identified in purified HeLa cell chromatin on the basis of its failure to dissociate from the DNA at very high ionic strength (2.5 M NaCl-5.0 M urea), where over 92% of the total chromatin protein is released. The tight proteins are insoluble in 0.4 N H2SO4 and lack histones as determined by polyacrylamide gel electrophoresis. They have molecular weights between 14,000 and 85,000 with over 70% of the polypeptide chains between 14,000 and 30,000 mol wt. This is the same size range as the non-histone proteins which others have found to display species-specific DNA binding in vitro. There is approximately one molecule of tight protein per 275 DNA base pairs. The tight proteins are characterized by much higher rates of labeling with amino acids than the histones and non-histone chromatin proteins that are dissociated from the DNA by high ionic strength, but they have the lowest phosphorylation levels. Chromatin fractionation experiments were performed to investigate the distribution of tight proteins between template-active and template-inactive regions. Under specific conditions, spleen DNase (DNase II) selectively shears those portions of HeLa cell chromatin that contain nascent RNA transcripts. This nascent RNA-enriched chromatin fraction also contains a high level of the proteins known to be complexed with heterogeneous nuclear RNA in ribonucleoprotein particles and contains over 70% of the RNA polymerase activity of total chromatin. When this method was employed to investigate the distribution of tight proteins, they were found to be almost entirely confined to the template-inactive fraction. Although these experiments do not elucidate the precise function of these proteins, they identify, for the first time, a particular subclass of non-histone chromosomal protein which is distributed asymmetrically between transcriptionally active and inactive chromatin regions.
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PMID:A special class of non-histone protein tightly complexed with template-inactive DNA in chromatin. 114 2


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