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At least 433 records · Page 24Linked to original sources
PubMed1969

Synthesis of replicative form deoxyribonucleic acid and messenger ribonucleic acid by gene IV mutants of bacteriophage S13.

Gene IV mutants of bacteriophage S13 are known to be blocked in infectious replicative form (RF) DNA synthesis, producing only a small fraction of the RF formed by wild-type phage. This investigation shows that gene IV mutants form only parental RF and are blocked in the synthesis of any progeny RF, either infectious or noninfectious. This was determined by density labeling of RF in cells treated with mitomycin C to suppress host deoxyribonucleic acid (DNA) synthesis. RF synthesis was also studied in untreated cells, using methylated albumin columns to separate RF from host DNA. In this case it was also found that synthesis of progeny RF by gene IV mutants is negligible. It has been found by DNA-ribonucleic acid (RNA) hybridization experiments that gene IV mutants form at least as much or more messenger RNA than wild-type phage. Therefore, parental RF alone can form messenger RNA in appreciable amounts.

Bacteriophages↗
PubMed1982

Regulation of tyrosine aminotransferase messenger ribonucleic acid in rat liver. effect of cycloheximide on messenger ribonucleic acid turnover.

Tyrosine aminotransferase messenger ribonucleic acid (mRNA) activity in rat liver was rapidly increased 3-6-fold following in vivo administration of hydrocortisone acetate, dibutyryladenosine cyclic 3',5'-phosphate, or the protein synthesis inhibitor cycloheximide. Treatment with the steroid hormone or cyclic nucleotide in combination with cycloheximide resulted in levels of tyrosine aminotransferase mRNA 10-20-fold greater than control values. These changes in mRNA activity were not accompanied by changes in albumin mRNA or total liver template activity. The rapid decline in tyrosine aminotransferase mRNA activity following cordycepin inhibition of de novo RNA synthesis was prevented by cycloheximide treatment. This protection was not observed when pactamycin was substituted for cycloheximide, demonstrating that the inhibition of protein synthesis per se was not responsible for the stabilization of tyrosine aminotransferase mRNA. Based upon the effects of cycloheximide and pactamycin on rat liver polysome structure, it is concluded that the cycloheximide-mediated increase in tyrosine aminotransferase mRNA activity is the result of stabilization of the mRNA molecule which renders the message less susceptible to inactivation and degradation in the cytoplasm. The action of cycloheximide is very specific for tyrosine aminotransferase, phosphoenolpyruvate carboxykinase, and probably several other mRNAs that code for minor liver proteins that turn over rapidly in response to hormonal or metabolic stimuli.

Animals↗
PubMed1973

Inhibitors of ribonucleic acid synthesis in Saccharomyces cerevisiae: decay rate of messenger ribonucleic acid.

Daunomycin and ethidium bromide, two deoxyribonucleic acid-intercalating drugs, inhibit ribonucleic acid (RNA) and protein synthesis in Saccharomyces cerevisiae. Both agents rapidly curtail uptake of radioactive adenine, whereas the kinetics of radioactive leucine uptake after drug addition are consistent with translation of a pool of exponentially decaying messenger RNA. Messenger RNA half-life determinations from these experiments gave identical results over a range of drug concentrations; this value is 21 +/- 4 min at 30 C. In a temperature-sensitive mutant in which RNA synthesis is curtailed at the nonpermissive temperature, a similar half-life for messenger RNA decay is found both in the absence and in the presence of either drug. This indicates that at the concentrations used in this study, neither daunomycin nor ethidium bromide has an appreciable direct effect on translation and do not increase the lability of messenger RNA.

Adenine↗
PubMed1972

Regulation of histidyl-transfer ribonucleic acid synthetase formation in a histidyl-transfer ribonucleic acid synthetase mutant of Salmonella typhimurium.

Control of formation of the histidyl-transfer ribonucleic acid (tRNA) synthetase with an increased K(m) for histidine was studied in a hisS mutant of Salmonella typhimurium. Histidine restriction of both the hisS and hisS(+) strains resulted in a derepression of synthesis of histidyl-tRNA synthetase. When grown in a concentration less than the K(m) (100 mug/ml) of l-histidine, the hisS mutant maintained a higher level of histidyl-tRNA synthetase than the hisS(+) strain. Addition of excess amounts of l-histidine to the growth medium of the hisS mutant culture grown with 100 mug of l-histidine per ml resulted in a repression of histidyl-tRNA synthetase formation to equal that of the hisS(+) strain grown in 100 mug of l-histidine per ml. These data confirm previous findings that histidine tRNA is involved in the repression of synthesis of histidyl-tRNA synthetase.

Amino Acyl-tRNA Synthetases↗
PubMed1981

[Protein quality of dietary yeast ribonucleic acid studied in growing rats. 2. Effect of ribonucleic acid on N balance and urinary N fractions].

In a balance trial with growing rats the influence of dietary ribonucleic acid (RNA) on N-metabolism was tested. Yeast-RNA was supplied at four levels ranging from 7.8% to 31.2% of diets nitrogen (1.64% in DM from casein + DL-methionine). The mean apparent digestibility of the RNA-N ingested was determined as 95%. Of the RNA-N consumed 16.6% were retained as measured by N-balance technique, whereas no retention of the RNA-N was observed by body-N analysis. This discrepancy in RNA-N retention was attributed to the relatively increased N-losses with higher N-intake when using the N-balance method. By regression analysis it was found that 80.2% of the RNA-N consumed were excreted via kidneys. Of the RNA-N intake 45.5% appeared in urea, 30.9% in allantion, only 1.1% and 0.3% in uric acid and creatinine respectively.

Allantoin↗
PubMed1969

Correlation between the rate of ribonucleic acid synthesis and the level of valyl transfer ribonucleic acid in mutants of Escherichia coli.

By use of a mutant of Escherichia coli with a partially thermolabile transfer ribonucleic acid (tRNA) synthase, it was possible to regulate the rate of RNA synthesis over a 10-fold range. The addition of chloramphenicol to cultures kept at the nonpermissive temperature stimulated RNA synthesis. The longer the culture was kept at the nonpermissive temperature prior to addition of chloramphenicol, the lower was the resulting rate of RNA synthesis. The decrease in the rate of incorporation of labeled uracil into RNA was correlated with the decrease in the level of valyl tRNA. Additional experiments provided evidence which may be interpreted as indicating that valyl tRNA does not, by itself, react with the RNA-forming system.

Carbon Isotopes↗
PubMed1965

Nucleotide composition of nucleic acids of fungi. I. Ribonucleic acids.

Storck, Roger (The University of Texas, Austin). Nucleotide composition of nucleic acids from fungi. I. Ribonucleic acids. J. Bacteriol. 90:1260-1264. 1965.-The nucleotide composition of the ribonucleic acids (RNA) present in extracts of 26 species of fungi was determined. The results were analyzed, together with those in the literature. It was found that the content in moles per cent of guanine plus cytosine (GC content) varied from 44.1 to 60.5 in a distribution composed of 8 species of zygomycetes, 10 of ascomycetes, 11 of deuteromycetes, and 8 of basidiomycetes. The GC-content range and average were, respectively, 44.1 to 49.3 and 46.4 for the zygomycetes, 47.4 to 54.4 and 50.2 for the ascomycetes, 48.2 to 54.5 and 51.6 for the deuteromycetes, and 50.4 to 60.5 and 52.4 for the basidiomycetes. The GC content averaged 45.6 and ranged from 44.1 to 46.3 for four Mucor species. In addition, GC contents significantly lower than 50 were also encountered in some species of Hemiascomycetidae, suggesting that AT type RNA is not uncommon in fungi. It was proposed that the base composition of fungal RNA might have a taxonomic and phylogenetic significance.

Chemical Phenomena↗
PubMed1970

Regulation of ribonucleic acid synthesis in Escherichia coli during diauxie lag: accumulation of heterogeneous ribonucleic acid.

The synthesis of ribonucleic acid (RNA) and of protein in Escherichia coli during glucose-lactose diauxie lag have been examined. The rate of RNA synthesis is about 7%, of the corresponding rate during exponential growth and the rate of protein synthesis 10 to 15%. Inhibition of RNA synthesis occurs to the same extent in both rel and rel(+) strains. The RNA which accumulates during 20 min in diauxie lag is composed of about 50% ribosomal and transfer RNA species and about 50% of a fraction which resembles messenger RNA (mRNA) in its heterogeneous sedimentation properties. Decay of the heterogeneous fraction occurs in the presence of glucose and actinomycin D with a half-life of 3 min, the same as that of pulse-labeled mRNA; however, during the diauxie lag, the half-life of this RNA is about 25 min. Accumulation of the heterogeneous RNA is further increased when protein synthesis is blocked by chloramphenicol. The data suggest that the disproportionate accumulation of mRNA during diauxie lag and energy source shift-down may be attributed at least in part to increased stability of mRNA, but do not rule out a preferential synthesis of mRNA.

Bacterial Proteins↗
PubMed1972

Role of histidine transfer ribonucleic acid in regulation of synthesis of histidyl-transfer ribonucleic acid synthetase of Salmonella typhimurium.

The role of histidine transfer ribonucleic acid (tRNA) in repression of synthesis of histidyl-tRNA synthetase was examined in two strains of Salmonella typhimurium, one of which was a histidine tRNA (hisR) mutant possessing 52% of the wild-type (hisR(+)) histidine tRNA and a derepressed level of the histidine biosynthetic enzymes during histidine-unrestricted growth. Histidine-restricted growth caused a derepression of the rate of formation of histidyl-tRNA synthetase in both strains. In the case of the wild-type strain, addition of histidine to the derepressed culture caused a repression of synthesis of histidyl-tRNA synthetase for at least one generation of growth. In contrast, when histidine was restored to the derepressed hisR mutant culture, synthesis of histidyl-tRNA synthetase was continued at the initial derepressed rate. These results suggest that histidine must be attached to histidine tRNA for repression of synthesis of histidyl-tRNA synthetase.

Aerobiosis↗
PubMed1970

Effect of the "ribonucleic acid control" locus in Escherichia coli on T4 bacteriophage-specific ribonucleic acid synthesis.

Amino acid control of ribonucleic acid (RNA) synthesis in bacteria is known to be governed genetically by the rel locus. We investigated whether the rel gene of the host would also exert its effect on the regulation of phage-specific RNA synthesis in T4 phage-infected Escherichia coli cells. Since T-even phage infection completely shuts off host macromolecular synthesis, phage RNA synthesis could be followed specifically by the cumulative incorporation of radioactivity from labeled precursors into RNA of infected cells. Labeled uracil was shown to accumulate in phage-specific RNA for 30 to 35 min after infection, a phenomenon which probably reflects an expansion of the labile phage-RNA pool. Amino acid starvation was effected by the use of auxotrophic bacterial strains or thienylalanine. The latter substance is an amino acid analogue which induces a chemical auxotrophy by inhibiting the biosynthesis of phenylalanine, tyrosine, and tryptophan. Phage RNA synthesis was strictly dependent on the presence of amino acids, whereas phage deoxyribonucleic acid synthesis was not. By the use of several pairs of bacterial strains which were isogenic except for the rel gene, it was demonstrated that amino acid dependence was related to the allelic state of this gene. If the rel gene was mutated, amino acid starvation did not restrict phage RNA synthesis.

Amino Acids↗