scholarly journals Nucleolar 4s ribonucleic acid in dipteran salivary glands in the presence of inhibitor

1968 ◽  
Vol 109 (3) ◽  
pp. 375-387 ◽  
Author(s):  
J. L. Sirlin ◽  
U E Loening
Keyword(s):  
Salivary Glands ◽  
Ribosomal Rna ◽  
Ribonucleic Acid ◽  
Rna Synthesis ◽  
Transfer Rna ◽  
Chromosome 2 ◽  
Insect Larvae ◽  
Nuclear Rna

1. Salivary glands of insect larvae accumulate newly made transfer RNA in the nucleolus when maintained in the presence of nucleoside antagonists that inhibit RNA synthesis preferentially at the chromosome. 2. The nucleus contains precursor transfer RNA, which, on the basis of the general evidence, may originate in the chromosome and then be methylated in the nucleolus. 3. The maturation of precursor ribosomal RNA is blocked in the nucleolus during inhibition. 4. The transport of nuclear RNA to cytoplasm is also blocked. 5. It is suggested that, if the transfer RNA accumulated in the nucleolus does indeed originate in the chromosome, the accumulation may result from the blockage of an obligatory transient association of the RNA with the nucleolus.

scholarly journals RNA SYNTHESIS IN HELA CELLS

1970 ◽  
Vol 47 (3) ◽  
pp. 734-744 ◽  
Author(s):  
Thoru Pederson ◽  
Elliott Robbins
Keyword(s):  
Ribosomal Rna ◽  
Hela Cells ◽  
Rna Synthesis ◽  
Close Correlation ◽  
Selective Inhibition ◽  
Transfer Rna ◽  
Extracellular Medium ◽  
Hypertonic Medium ◽  
Nuclear Rna ◽  
Ribosomal Precursor

Interphase HeLa cells manifest a stepwise shutoff of RNA synthesis when the tonicity of the extracellular medium is gradually increased. Synthesis of heterogeneous nuclear RNA is most sensitive and is selectively inhibited at 1.5 times isotonicity (450 milliosmols/liter), while 45S ribosomal RNA synthesis is not affected significantly below 2.0 times isotonicity. Transfer RNA synthesis is least sensitive to increased osmolarity and is not completely inhibited until the electrolyte concentration of the medium is elevated to 2.8 times isotonicity. Although the transcription and methylation of 45S ribosomal precursor is unaffected at 1.5 times isotonicity, there is pronounced impairment of its processing into 32S and 18S RNA. Using a refined cell synchronization technique, we have been able to compare these effects of hypertonicity with the shutoff of RNA synthesis which occurs during the G2-prophase interval of the cell division cycle. In this case, as with random cells in hypertonic medium, a selective inhibition of heterogeneous nuclear RNA synthesis and slowed processing of 45S ribosomal RNA were found, whereas synthesis of 45S and transfer RNA continued unabated throughout G2-prophase. While it is known that RNA synthesis essentially ceases during metaphase, we have noted that transfer RNA synthesis continues in metaphase at 10–15% of the interphase rate, which is of particular interest in view of the relative resistance of this species to hypertonicity. The close correlation between the patterns of cessation of RNA synthesis at mitosis and during exposure to hypertonic medium supports our earlier contention that alteration of intracellular electrolyte levels provides a useful model for studying the mechanism of mitosis.

scholarly journals THE SELECTIVE INTERRUPTION OF NUCLEOLAR RNA SYNTHESIS IN HELA CELLS BY CORDYCEPIN

1969 ◽  
Vol 41 (2) ◽  
pp. 510-520 ◽  
Author(s):  
Moshe Siev ◽  
Robert Weinberg ◽  
Sheldon Penman
Keyword(s):  
Ribosomal Rna ◽  
Hela Cells ◽  
Rna Synthesis ◽  
Transfer Rna ◽  
Short Exposure ◽  
Low Concentrations ◽  
Dna And Protein Synthesis ◽  
Ribosomal Precursor ◽  
Precursor Molecules ◽  
Nucleolar Rna

Cordycepin is an analogue of adenosine lacking the 3'-OH. When incorporated into a growing RNA molecule, cordycepin prevents further elongation, thus producing a prematurely terminated RNA molecule. When HeLa cells are exposed to low concentrations of cordycepin, DNA and protein synthesis are unaffected during short exposure periods. The synthesis of completed ribosomal and ribosomal-precursor (45S) RNA is significantly depressed. Partially completed 45S ribosomal precursor molecules accumulate in the nucleolus. 18S ribosomal RNA can be cleaved from these incomplete precursors, while 32S ribosomal precursor cannot be produced from partially snythesized 45S molecules. The synthesis of transfer RNA is also reduced in the presence of cordycepin. The synthesis of the nuclear heterogeneous RNA species is unaffected by the drug while the cytoplasmic heterogeneous RNA is slightly reduced.

scholarly journals The control of ribonucleic acid synthesis in bacteria. Steady-state content of messenger ribonucleic acid in Escherichia coli M.R.E. 600

1970 ◽  
Vol 120 (2) ◽  
pp. 279-288 ◽  
Author(s):  
W. J. H. Gray ◽  
J. E. M. Midgley
Keyword(s):  
Escherichia Coli ◽  
Ribosomal Rna ◽  
Ribonucleic Acid ◽  
Messenger Rna ◽  
Acid Synthesis ◽  
Growth Conditions ◽  
Transfer Rna ◽  
Average Lifetime ◽  
Messenger Ribonucleic Acid ◽  
Wide Range

1. The technique of DNA–RNA hybridization was used to follow changes in the amount and average lifetime of unstable messenger RNA in Escherichia coli M.R.E. 600 over a wide range of different growth conditions. The method of analysis was based on the kinetics of incorporation of exogenous labelled nucleic acid bases into the RNA of steadily growing cultures, as described by Bolton & McCarthy (1962). 2. The ratio of the average lifetime of messenger RNA to the mean generation time of E. coli cultures was constant over the temperature range 25–45°C in a given medium, but the constant varied with the nature of the growth medium. For cultures growing in sodium lactate–salts or glucose–salts media the ratio was 0.046±0.005 and in enriched broth it was 0.087±0.009. Measurements of the amounts of transfer RNA, ribosomal RNA and messenger RNA were also made. The results confirmed earlier reports that the ratio of the amount of messenger RNA to the amount of ribosomes in the cells is virtually constant. On the other hand, the ratio of the amount of transfer RNA to the amount of ribosomal RNA decreased with increasing growth rate at a given temperature. 3. In cultures at temperatures higher than necessary for optimum rates of growth the average lifetime of messenger RNA lengthened in harmony with the increased time required for cell division. It seems that suboptimum growth rates at higher temperatures cannot be explained simply as a combination of increased rates of synthesis and breakdown of messenger RNA with a grossly decreased efficiency of translation. The absolute rate of messenger RNA synthesis was lowered, and its amount in the cells was typical of all other cultures grown at lower temperatures in the same medium. 4. The rate of entry of exogenous labelled uracil into unstable messenger RNA and stable ribosomal RNA was constant in all media at all temperatures in the approximate ratio 1:2. In media supporting a lower rate of growth, e.g. lactate–salts or glucose–salts media, the messenger RNA fraction constituted 2.2±0.3% of the total cellular RNA. In enriched broth 3.6±0.3% of the total RNA was messenger.

Synthese von Ribonucleinsäuren in Ganzkeimen und im isolierten Ektoderm von Triturus alpestris

1965 ◽  
Vol 20 (10) ◽  
pp. 997-1004 ◽  
Author(s):  
H. Tiedemann ◽  
J. Born ◽  
U. Kocher-Becker
Keyword(s):  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Specific Activity ◽  
Transfer Rna ◽  
Sedimentation Pattern ◽  
Triturus Alpestris ◽  
Different Ages

The correlation between the synthesis of different RNA-fractions and embryonic differentiation was compared by studying the RNA-synthesis in whole Triturus embryos of different ages and isolated ectoderm not induced to develop into special tissues.In the isolated ectoderm, having the same age as neurulae, transfer-RNA as well as ribosomal-RNA is synthesized. The transfer-RNA has about the same specific activity and the ribosomal-RNA a somewhat lower specific activity compared to neurulae. Pulse-labelled RNA with a heterogeneous sedimentation pattern is likewise synthesized in whole embryos and in isolated ectoderm. — The results are in accord with the hypothesis that embryonic differentiation is directed by informational-RNA, which is only a very small part of the whole RNA.

scholarly journals Changes in the ribonucleic acid metabolism of aging mouse tissues with particular reference to the prostate gland

1968 ◽  
Vol 110 (1) ◽  
pp. 79-86 ◽  
Author(s):  
W. I. P. Mainwaring
Keyword(s):  
Ribosomal Rna ◽  
Ribonucleic Acid ◽  
Messenger Rna ◽  
Rna Synthesis ◽  
Acid Metabolism ◽  
Prostate Gland ◽  
Mouse Tissues ◽  
Aging Mouse ◽  
Tissue Homogenates ◽  
Increased Susceptibility

1. The synthesis of RNA in purified nuclei of tissues from aged mice is substantially diminished. 2. As judged by the recovery of RNA in 105000g supernatants of tissue homogenates, the synthesis of ribosomal RNA may be particularly affected. 3. The decrease in RNA synthesis may be due to changes in the composition of the nuclear-associated protein with age, which result in changes in the priming ability of tissue chromatin. 4. Aging is accompanied by marked changes in the sedimentation profiles of ribonucleoprotein particles. These can be attributed to an age-associated depletion in messenger RNA or to an increased susceptibility to enzymic disaggregation.

scholarly journals The hybridization capacity of ribonucleic acid produced during hormone action

1968 ◽  
Vol 109 (2) ◽  
pp. 253-258 ◽  
Author(s):  
G. R. Wyatt ◽  
J. R. Tata
Keyword(s):  
Growth Hormone ◽  
Rat Liver ◽  
Ribosomal Rna ◽  
Ribonucleic Acid ◽  
Hormone Action ◽  
Rna Molecules ◽  
Nuclear Rna ◽  
Ribosomal Precursor ◽  
Preferential Synthesis

1. Measurements of hybridization with homologous DNA were used to assess the nature of the RNA synthesized during hormone action in several systems. 2. When increasing amounts of pulse-labelled rat liver nuclear RNA were annealed with constant amounts of DNA, saturation was not achieved even with RNA/DNA ratios of up to 180:1, which is taken to indicate great diversity in the species of labelled RNA molecules. In the converse experiment, when the DNA/RNA ratio was varied up to 20:1, a plateau of hybridization was observed, and the non-hybridizing RNA is believed to represent chiefly ribosomal and ribosomal precursor species. 3. In the livers of hypophysectomized and thyroidectomized rats treated with growth hormone and tri-iodothyronine, and in whole Xenopus larvae during induced metamorphosis, the synthesis of non-hybridizing RNA was consistently stimulated more than that of hybridizing RNA. This is interpreted as reflecting preferential synthesis of ribosomal RNA in response to these hormones.

THE NUCLEAR RNA-SYNTHESIS IN THE ANTERIOR PITUITARY OF RATS

1965 ◽  
Vol 49 (3_Suppl) ◽  
pp. S160 ◽  
Author(s):  
E. Stöcker ◽  
G. Dhom
Keyword(s):  
Anterior Pituitary ◽  
Rna Synthesis ◽  
Nuclear Rna Synthesis ◽  
Nuclear Rna

scholarly journals Accelerated rates of ribosomal RNA synthesis during growth of contracting heart cells in culture

1989 ◽  
Vol 264 (30) ◽  
pp. 18220-18227
Author(s):  
P J McDermott ◽  
L I Rothblum ◽  
S D Smith ◽  
H E Morgan
Keyword(s):  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Heart Cells ◽  
Cells In Culture ◽  
Contracting Heart
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