Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bacteriophage T7-coded inhibitor of Escherichia coli RNA polymerase, termed I protein, was purified from an inactive E. coli RNA polymerase-I protein complex isolated from phage T7-infected cells. A molecular weight of about 7,000 to 9,000 was assigned to the purified I protein by acrylamide-sodium dodecyl sulfate gel electrophoresis, Sephadex G-50 gel filtration, and glycerol gradient centrifugation analysis. I protein inhibits initiation of RNA synthesis by directly binding to the RNA polymerase holoenzyme and prevents the binding of the enzyme to the promoter sites on the template T7 DNA. However, once a highly stable transcriptional preinitiation complex between RNA polymerase holoenzyme and T7 DNA is formed at the promoter site on T7 DNA in the absence of nucleoside triphosphates, I protein does not inhibit the initiation of RNA synthesis by this preformed complex upon addition of nucleoside triphosphates. RNA synthesis by the core RNA polymerase and the binding of core RNA polymerase with template DNA are not inhibited by I protein, although a partial association between the core enzyme and I protein can be observed. I protein does not bind to sigma factor or T7 DNA. Therefore, binding of I protein with the RNA polymerase, which results in the inhibition of initiation of RNA synthesis, requires the presence of sigma factor in the RNA polymerase holoenzyme form.
J Virol 1977 Dec
PMID:I protein: bacteriophage T7-coded inhibitor of Escherichia coli RNA polymerase. 33 33

The genome of virulent coliphage T5 contains about 30 sites which form stable complexes with E. coli RNA polymerase. Some of these sites bind RNA polymerase with high rates, others form extremely stable complexes as compared with promotors of other E. coli systems. The transcriptional activity of these promotors in vivo and in vitro reflects the rate of complex formation with RNA polymerase rather than the stability of the enzyme/promotor complex. The fastest, i.e. the most active promotors are found in the "early" region of gene expression followed by promotors of the "preearly" class. The few binding sites for the E. coli holoenzyme within the "late" region react more slowly with the enzyme.
Mol Gen Genet 1977 Dec 09
PMID:Interaction of E. coli RNA polymerase with promotors of coliphage T5: the rates of complex formation and decay and their correlation with in vitro and in vivo transcriptional activity. 34 Sep 27

The expression of the genes specifying the beta and beta' subunits of RNA polymerase (nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6) was examined in an Escherichia coli strain bearing a temperature-sensitive mutation in the beta' subunit gene. A shift to 42 degrees results in a restriction of RNA chain initiation and a cessation of RNA synthesis. A shift to 39 degrees results in only partial restriction, allowing RNA and protein synthesis to continue. The partial restriction produces a 5- to 6-fold increase in the relative transcription rate of the beta and beta' genes and a concomitant increase in the relative synthesis rate of the beta and beta' proteins. The transcription rate of ribosomal protein genes was also increased somewhat. These results indicate that the genes specifying the beta and beta' subunits of RNA polymerase are regulated at the level of transcription and that this regulation is related to the transcription of ribosomal protein genes. Furthermore, the results indicate that this regulation of the beta and beta' RNA polymerase subunit genes is somehow triggered by a reduction in the ability of RNA polymerase to initiate transcription on the bacterial chromosome.
Proc Natl Acad Sci U S A 1977 Dec
PMID:Regulation of synthesis and activity of a mutant RNA polymerase in Escherichia coli. 34 Nov 56

A new assay yielding mechanistic information on the initiation reaction of Escherichia coli RNA polymerase has been developed. It was found to be useful in characterizing the promoters of bacteriophage DNA templates. The binding of the first two triphosphates in an RNA sequence was determined to be equilibrium ordered with ATP binding first followed by UTP on the lambda promoters PL. and PR. The products resulting from phosphodiester bond formation, pppApU and PPi, dissociated rapidly in the absence of the other triphosphates required for RNA synthesis. The resulting steady state conversion of ATP and UTP into pppApU was the basis for the new assay. The rate-limiting step in the initiation reaction was not precisely determined, but it was argued not to be entirely the release of product. The Zn2+ chelator, 1,10-phenanthroline, was partially characterized and found to be an uncompetitive inhibitor of ATP in the reaction (Ki = 100 micrometer). The unique advantage of this steady state assay is that several steps in the RNA initiation process are amplified kinetically and thus can be examined separately with techniques applicable to any other two-substrate, two-product enzyme reaction.
J Biol Chem 1978 Dec 25
PMID:A steady state assay for the RNA polymerase initiation reaction. 36 12

The mechanism of rifampicin inhibition of Escherichia coli RNA polymerase was studied with a newly developed steady state assay for RNA chain initiation and by analysis of the products formed with several 5'-terminal nucleotides. The major effect of rifampicin was found to be a total block of the translocation step that would ordinarily follow formation of the first phosphodiester bond. These effects were incorporated into a steric model for rifampicin inhibition. Additional minor effects of the enzyme bound inhibitor were to increase slightly the lifetime of RNA polymerase on the lambdaPR' promoter and to increase by two the apparent Michaelis constants of the initiating triphosphates. The products formed by RNA polymerase in the presence of rifampicin belong nearly exclusively to the class pppPupN. No evidence for the accumulation of such molecules was obtained in vivo.
J Biol Chem 1978 Dec 25
PMID:On the mechanism of rifampicin inhibition of RNA synthesis. 36 13

Purified core histones (H2A, H2B, H3, and H4) and bacteriophage T7 DNA have been reconstituted to form a nucleoprotein complex, and the properties of this complex as a template for transcription by Escherichia coli RNA polymerase have been studied. At low ionic strength, RNA chain elongation rates are slow, and the chains produced even after long incubation are short. At higher salt concentrations, chain-elongation rates approach those on naked DNA. Since the salt concentrations used are not in themselves sufficient to dissociate the histones from the DNA, some mechanism must exist that permits passage of the polymerase through histone-covered regions.
Biochemistry 1978 Dec 26
PMID:Transcription of histone-covered T7 DNA by Escherichia coli RNA polymerase. 36 33

We have isolated two regulatory mutants altered in the leader region of the Escherichia coli tryptophan (trp) operon. In one mutant, trpL29, the AUG translation start codon for the trip leader peptide is replaced by AUA. The other mutant, trpL75, has a G leads to A change at residue 75, immediately after the UGA translation stop codon for the trp leader peptide. In vivo, trpL29 and trpL75 increase the efficiency of transcription termination at the trp attenuator 3- to 5-fold. trpL29 and trpL75 also fail to respond fully to tryptophan starvation and other conditions that normally relieve transcription termination at the trp attenuator. The trpL29 mutation, which presumably reduces synthesis of the trp leader peptide, is cis dominant. The effect of starvation for a number of the amino acids in the trp leader peptide was determined. Only starvation for tryptophan and arginine, amino acids that occur at residues 10, 11, and 12 of the 14-residue trp leader peptide, elicits relief of transcription termination. Our findings suggest that translation of trp leader RNA is involved in regulation of transcription termination at the attenuator. A model is discussed in which the location of the ribosome synthesizing the leader peptide is communicated to the RNA polymerase transcribing the leader region.
Proc Natl Acad Sci U S A 1978 Dec
PMID:Translational control of transcription termination at the attenuator of the Escherichia coli tryptophan operon. 36 6

A gene affecting the sigma subunit of DNA-dependent RNA polymerase is tightly linked to dnaG at 66 min on the Escherichia coli chromosome. In order to create an easily selectable marker in this region, we inserted transposon-10, which carries a gene determining resistance to tetracycline (tet) near 66 min, and the order tolC-dnaG-sigma-tet was determined. We used frequency of contransduction with tet as a criterion to screen a collection of spontaneous temperature-sensitive Escherichia coli mutants that might affect the sigma subunit. One such mutant was found to map at the sigma locus. The sigma subunit isolated from this mutant is unstable at 46 degrees C in vitro and has an altered electrophoretic mobility. The temperature sensitivity of RNA synthesis in this mutant indicates that most transcription in E. coli is sigma dependent.
Proc Natl Acad Sci U S A 1978 Dec
PMID:Temperature-sensitive Escherichia coli mutant producing a temperature-sensitive sigma subunit of DNA-dependent RNA polymerase. 36 14

Rat liver chromatin was fractionated into DNA, histones and non-histone chromosomal proteins and each component was modified with N-methyl-l-N'-nitro-N-nitrosoguanidine of N-ethyl-N'-nitrosoguanidine. The radioactivity of 14C-labeled alkyl or guanidino moieties of both compounds bound significantly to both histones and non-histone chromosomal proteins and the binding of N-methyl-N'-nitro-N-nitrosoguanidine was higher than N-ethyl-N'-nitro-N-nitrosoguanidine. However the binding of both compounds to DNA was very low and its significance was hard to evaluate. All of the three components, one of which was modified, were reconstituted into chromatin, then, [3H]UMP incorporation into acid insoluble material using Escherichia coli RNA polymerase (EC 2.7.7.6) was measured. Only with the reconstituted chromatin containing histones modified either by N-methyl-N'-nitro-N-nitrosoguanidine or N-ethyl-N'-nitro-N-nitrosoguanidine, the template activity increased drastically; i.e., about 10 or 5 times higher than that with the unmodified reconstituted chromatin, respectively. However, any remarkable alteration in the electrophoretic pattern of protein fraction of the reconstituted chromatin could not be found. The results obtained in this study are discussed in the context that the modified histones could give rise to change in the mutual interaction of chromosomal components during the reconstitution of chromatin accompanied with the increase of chromatine template activity.
Biochim Biophys Acta 1978 Dec 21
PMID:Modification of rat liver chromatin by N-methyl-N'-nitro-N-nitrosoguanidine or N-ethyl-N'-nitro-N-nitrosoguanidine and template activity for RNA synthesis by Escherichia coli RNA polymerase after reconstitution. 36 40

Problems involved in using the Hg-nucleotide technique for in vitro chromatin transcription are 2-fold. First, Escherichia coli RNA polymerase can utilize endogenous RNA as template and synthesize complementary sequences which remain base-paired to the template, thereby allowing it to bind to the SH-Sepharose column and copurify with the newly synthesized Hg-RNA. Second, non-mercurated endogenous RNA can bind to the SH-Sepharose through aggregation with Hg-RNA and thus be retained in the final RNA preparation. These two problems associated with the Hg-nucleotide technique can be minimized by modifying the conditions for RNA synthesis and SH-Sepharose chromatography. Using the modified procedure the Hg-nucleotide and SH-Sepharose technique can remove more than 90% of endogenous RNA contaminants. In order to directly demonstrate that the mRNAov sequences detected in vitro result from de novo transcription of oviduct chromatin, experiments were carried out which show that the hybridizable RNA sequences contain the Hg element and that the synthesis of these RNA sequences is sensitive to low concentrations of actinomycin D. These combined results strongly suggest that the majority of mRNAov sequences detected by hybridization to cDNAov is indeed due to DNA-dependent RNA synthesis by E. coli RNA polymerase and not due to an artifact of endogenous RNA contamination. This observation was further supported by data obtained using a filter hybridization method which measures directly the mRNAov sequences present in [3H]RNA synthesized from chromatin. The 3H-labeled ovalbumin messenger RNA was assayed by hybridization to cloned pOV230 DNA containing the ovalbumin structural gene sequence. With this modified Hg-nucleotide-SH-Sepharose technique and filter hybridization technique, we have restudied the in vitro transcription of the ovalbumin gene from chromatins isolated at different stages of hormone-induced oviduct development. The results are in agreement with our previous findings which suggest that the primary regulation of ovalbumin synthesis by steroid hormones occurs at the transcriptional level.
Biochim Biophys Acta 1978 Dec 21
PMID:Effect of estrogen on gene expression in the chick oviduct. In vitro transcription of the ovalbumin gene. 36 41


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