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)

Luzzati, Denise (Institut de Biologie Physico-Chimique, Paris, France). Effect of thymine starvation on messenger ribonucleic acid synthesis in Escherichia coli. J. Bacteriol. 92:1435-1446. 1966.-During the course of thymine starvation, the rate of synthesis of messenger ribonucleic acid (mRNA, the rapidly labeled fraction of the RNA which decays in the presence of dinitrophenol or which hybridizes with deoxyribonucleic acid) decreases exponentially, in parallel with the viability of the thymine-starved bacteria. The ability of cell-free extracts of starved bacteria to incorporate ribonucleoside triphosphates into RNA was determined; it was found to be inferior to that of extracts from control cells. The analysis of the properties of cell-free extracts of starved cells shows that their decreased RNA polymerase activity is the consequence of a modification of their deoxyribonucleic acid, the ability of which to serve as a template for RNA polymerase decreases during starvation.
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PMID:Effect of thymine starvation on messenger ribonucleic acid synthesis in Escherichia coli. 533 2

1. Isolated nuclei from starved rats showed a lowered incorporation of [(14)C]UMP into RNA. 2. The Mg(2+)-dependent incorporation was decreased by 30% after 1 day of starvation, but incorporation in the presence of Mn(2+) and ammonium sulphate decreased only after longer periods of starvation. 3. RNA synthesis by nuclei in the presence of excess of added RNA polymerase was unchanged after 1 day of starvation and was inhibited by 20% after 4 days. 4. The capacity of nuclei to bind actinomycin D was unchanged after 1 day and was decreased by 20% after 4 days of starvation.
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PMID:Decreased ribonucleic acid synthesis in isolated rat liver nuclei during starvation. 549 59

1. The Widnell & Tata (1966) assay method for Mg(2+)-activated DNA-dependent RNA polymerase was used for initial-velocity determinations of rat liver nuclear RNA polymerase. One unit (U) of RNA polymerase was defined as that amount of enzyme required for 1 mmol of [(3)H]GMP incorporation/min at 37 degrees C. 2. Colony fed rats were found to have a mean RNA polymerase activity of 65.9muU/mg of DNA and 18h-starved rats had a mean activity of 53.2muU/mg of DNA. Longer periods of starvation did not significantly decrease RNA polymerase activity further. 3. Rats that had been starved for 18h were used for all feeding experiments. Complete and tryptophan-deficient amino acid mixtures were given by stomach tube and the animals were killed 15-120min later. The response of RNA polymerase to the feeding with the complete amino acid mixture was rapid and almost linear over the first hour of feeding, resulting in a doubling of activity. The activity was still elevated above the starvation value at 120min after feeding. The tryptophan-deficient amino acid mixture produced a much less vigorous response about 45min after the feeding, and the activity had returned to the starvation value by 120min after the feeding. 4. The response of RNA polymerase to the feeding with the complete amino acid mixture was shown to occur within a period of less than 5min to about 10min after the feeding. 5. Pretreatment of the animals with puromycin or cycloheximide was found to abolish the 15min RNA polymerase response to the feeding with the complete amino acid mixture, but the activity of the controls was unaffected. 6. The characteristics of the RNA polymerase from 18h-starved animals and animals fed with the complete or incomplete amino acid mixtures for 1h were examined. The effects of Mg(2+) ions, pH, actinomycin D and nucleoside triphosphate omissions were determined. The [Mg(2+)]- and pH-activity profiles of the RNA polymerase from the animal fed with the complete mixture appeared to differ from those of the enzyme from the other groups, but this difference is probably not significant. 7. [5-(3)H]Orotic acid incorporation by rat liver nuclei in vivo was shown to be affected by the amino acid mixtures in a similar manner to the RNA polymerase. 8. The tryptophan concentrations of plasma and liver were determined up to 120 min after feeding with the amino acid mixtures. Feeding with the complete mixture produced a rapid increase in free tryptophan concentrations in both plasma and liver, but feeding with the incomplete mixture did not alter the plasma concentration. The liver tryptophan concentration increased at about 45min after feeding with the tryptophan-deficient diet. 9. There was a good correlation between the liver tryptophan concentration and RNA polymerase activity in all groups of animals. 10. It was concluded that the rat liver nucleus responded to an increase in amino acid supply by increased synthesis of RNA as a result of synthesis of RNA polymerase de novo. The correlation of tryptophan concentration and RNA polymerase activity appears to reflect the general amino acid concentration required to support hepatic protein synthesis and to produce new RNA polymerase. This new polymerase appears to differ from the basal RNA polymerase by its rapid synthesis and destruction, which may be a means of regulating RNA synthesis by the amino acid concentration in the liver.
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PMID:The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase. 549 25

To determine the stringent response, a repression of gene activity during amino acid starvation assumed to be mediated by the effector necleotide guanosine tetraphosphate (ppGpp), of metabolically regulated constitutive genes, we measured the transcription of ribosomal protein genes, the constitutive lac operon, and stable RNA genes in a variety of growth media and after amino acid starvation in a relA+/relA pair of Escherichia coli B/r strains. For rRNA and tRNA (stable RNA) it has previously been shown that the distinction between stringent control and growth rate control is unfounded, as the function describing the stable RNA gene activities at different concentrations of guanosine tetraphosphate is independent of growth conditions (exponential growth or amino acid starvation) and of the relA allele present. Here, the results indicated that the stringent responses of ribosomal protein genes and lac differ from their metabolic control during exponential growth in different media. This can be explained by polarity and RNA polymerase sink effects during amino acid starvation which are irrelevant for stable RNA genes but which are superimposed on mRNA gene activities.
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PMID:Transcription of ribosomal component genes and lac in a relA+/relA pair of Escherichia coli strains. 609 Mar 95

The uptake of nucleosides and the synthesis of RNA in Tetrahymena thermophila were examined following amino acid starvation. Omission of leucine, phenylalanine, or arginine from the medium resulted in a rapid decrease in the incorporation of [3H]uridine into the acid-soluble pool and acid-insoluble material (RNA). Amino acid starvation inhibited the uptake of all ribo- and deoxyribonucleosides tested but did not affect the uptake of amino acids or glucose. In addition, under the conditions used, the omission of an amino acid did not result in a large decrease in amino acid incorporation into total protein. Treatment of cells with cycloheximide or emetine gave results similar to the effects of amino acid starvation, but in these experiments the inhibition of protein synthesis was essentially complete. Nucleotide pool sizes were also measured following amino acid starvation. ATP and UTP levels were essentially unchanged, but the dTTP pool size was decreased by 40%. The decrease in RNA synthesis in vivo in the absence of an essential amino acid was reflected in the endogenous RNA synthetic activity of isolated nuclei. However, when solubilized RNA polymerase activity was measured with calf thymus DNA as template, no significant difference was observed between control and amino acid-starved cells.
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PMID:The effect of amino acid starvation on nucleoside uptake and RNA synthesis in Tetrahymena. 615 97

Parameters relating to RNA synthesis were measured after a temperature shift from 30 to 42 degrees C, in a relA+ and relA- isogenic pair of Escherichia coli strains containing a temperature-sensitive valyl tRNA synthetase. The following results were obtained: (i) the rRNA chain growth rate increased 2-fold in both strains; (ii) newly synthesized rRNA became unstable in both strains; (iii) the stable RNA gene activity (rRNA and tRNA, measured as stable RNA synthesis rate relative to the total instantaneous rate of RNA synthesis) decreased 1.7-fold in the relA+ strain and increased 1.9-fold in the relA mutant; and (iv) the RNA polymerase activity (measured by the percentage of total RNA polymerase enzyme active in transcription an any instant) decreased from 20 to 3.6% in the relA+ strain and remained unchanged (or increased at most to 22%) in the relA mutant. It is suggested that both rRNA gene activity and the RNA polymerase activity depend on the intracellular concentration of guanosine tetraphosphate, whereas the altered chain elongation rate and stability of rRNA are temperature or amino acid starvation effects, respectively, without involvement of relA function.
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PMID:relA-dependent RNA polymerase activity in Escherichia coli. 617 1

Under conditions of severe nitrogen starvation, brought about by nutritional shift-down, Bacillus brevis ATCC 8185 was unable to sporulate unless supplemented with the peptide antibiotic tyrocidine. The induction of sporulation was highly specific for tyrocidine and required only very low concentrations of the peptide (5 microM). Tyrocidine-induced sporulation was accompanied by the typical sporulation-specific events (e.g. extracellular protease production and dipicolinate synthesis) as well as the formation of linear gramicidin. The addition of tyrocidine produced acute inhibition of RNA synthesis that was followed by a limited activation of transcription near the time of onset of linear gramicidin synthesis, when the first sporulation-specific changes were observed. These results provide direct evidence for a role of tyrocidine in sporulation of B. brevis and suggest that the action of the peptide antibiotic may involve the control of transcription. Such a notion is supported by earlier studies on the effects of tyrocidine and linear gramicidin on purified RNA polymerase.
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PMID:Induction of sporulation in Bacillus brevis. 1. Biochemical events and modulation of RNA synthesis during induction by tyrocidine. 618 37

We have examined the transcription of two plasmid-encoded, stable RNAs; a shortened 16S ribosomal RNA and the spacer transfer RNA2Glu from the Escherichia coli rrnB operon. Plasmid deletions were constructed in vitro, in order to examine the DNA regions required for stringent control of rRNA expression in vivo during amino acid starvation. We find that rRNA synthesized from plasmids does exhibit a relA-dependent, stringent response. The DNA sequences required for this regulation do not extend beyond 20 bases downstream of the P1 transcription initiation site. Deletion of P2, the second of the two tandem rRNA promoters, does not weaken the stringent control of transcripts from P1. These results demonstrate that pause sites for RNA polymerase identified in vitro do not play a significant role in the stringent control of rRNA synthesis in vivo and imply that stringent regulation takes place at the level of initiation, rather than elongation, of transcription. Surprisingly, we find that the presence of extra intact rrnB operons (carried by a multicopy plasmid) reduces the magnitude of the stringent response.
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PMID:Regions of DNA involved in the stringent control of plasmid-encoded rRNA in vivo. 618 38

Unusual guanosine nucleotides synthesised during amino acid or energy source starvation are thought to be the effectors of the stringent response. In vitro experiments suggest that the magic spot compounds alter transcription specificity of RNA polymerase by binding to the enzyme. However, there is no good in vivo evidence for such an interaction. We define sites on the beta-subunit of RNA polymerase which, when altered, yield E.coli mutants apparently insensitive to the presence of ppGpp.
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PMID:Relaxed mutants of Escherichia coli RNA polymerase. 635 28

During the cellular differentiation induced by starvation of Acanthamoeba castellanii, the expression of a number of genes is regulated. Evidence is reviewed that at least one of these, the precursor ribosomal RNA transcription unit, is regulated at the level of transcription. The structure of the rRNA transcription unit and of the RNA polymerases responsible for transcription in Acanthamoeba are reviewed. Utilizing an in vitro transcription system constructed from these components, preliminary evidence has been obtained that pre-rRNA gene expression is regulated by a modification of RNA polymerase I that affects the enzyme's ability to participate efficiently in the initiation of transcription. These results are reviewed in relation to other known mechanisms of transcriptional regulation in eukaryotes.
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PMID:Regulation of ribosomal RNA transcription during differentiation of Acanthamoeba castellanii: a review. 635 52


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