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 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.

Intranuclear Accumulation of Rna Resembling the Smaller Ribosomal Rna Component

1970 ◽  
Vol 6 (1) ◽  
pp. 53-72
Author(s):  
M. E. BRAMWELL
Keyword(s):  
Ribosomal Rna ◽  
Base Composition ◽  
Actinomycin D ◽  
Total Radioactivity ◽  
16S Ribosomal Rna ◽  
Low Concentrations ◽  
Rapid Accumulation ◽  
Nuclear Rna ◽  
Step Down ◽  
Nucleolar Rna

A study was made of the nuclear RNA in HeLa cells with particular reference to the rapidly labelled fractions. It was found that if cells were incubated at a high density, that is, under ‘step-down’ conditions, there was a rapid accumulation of RNA in the nucleus. The fraction of the nuclear RNA which includes rapidly labelled RNA and which binds tightly to columns of methylated albumin on kieselguhr increased in amount and reached levels which permitted enough of the material to be isolated for direct measurement of its base composition. This was found to be very similar to that of 16s ribosomal RNA. When cells growing logarithmically were treated with low concentrations of actinomycin D and then incubated in the presence of [3H]uridine it was found that an RNA fraction which bound tightly to methylated albumin on kieselguhr again accumulated in the nucleus. This fraction resembled that which accumulated under ‘step-down’ conditions. It contained over 85% of the total radioactivity in the nuclear RNA and again had a base composition very similar to 16s ribosomal RNA. Since nucleolar RNA synthesis was inhibited by the concentrations of actinomycin D used, it appeared that an RNA closely resembling 16s ribosomal RNA was synthesized outside the nucleolus. Sedimentation patterns on sucrose density gradients and thermal denaturation profiles lent support to the view that the RNA which binds tightly to columns of methylated albumin on kieselguhr probably represents ‘nascent’ 16s ribosomal RNA.

Studies on the Control of Ribosomal RNA Synthesis in HeLa Cells

1975 ◽  
Vol 57 (1) ◽  
pp. 79-83 ◽  
Author(s):  
C. James CHESTERTON ◽  
Barbara E. H. COUPAR ◽  
Peter H. W. BUTTER WORTH ◽  
Janice BUSS ◽  
Melvin H. GREEN
Keyword(s):  
Ribosomal Rna ◽  
Hela Cells ◽  
Rna Synthesis

scholarly journals A comparative study of the effect of aflatoxin B1 and actinomycin D on HeLa cells

1969 ◽  
Vol 114 (2) ◽  
pp. 289-298 ◽  
Author(s):  
E. H. Harley ◽  
K. R. Rees ◽  
A. Cohen
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Rna ◽  
Mechanism Of Action ◽  
Aflatoxin B1 ◽  
Hela Cells ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Inhibitory Effect ◽  
Cytotoxic Effects ◽  
Rna Precursor

1. The cytotoxic effects of aflatoxin B1 on HeLa cells were examined and effects of short exposures of the cells to the toxin were found to be reversible. 2. Aflatoxin B1 inhibited the synthesis of both ribosomal and heterodisperse RNA. It is proposed that the toxin's mechanism of action on ribosomal RNA synthesis is related to its inhibitory effect on the maturation of the 45s-ribosomal-RNA precursor. 3. Protein synthesis is inhibited to a greater extent by aflatoxin B1 than by actinomycin D. In contrast with actinomycin D, aflatoxin B1 was shown to disaggregate polyribosomes directly.

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 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.

Inhibition of Ribosomal RNA Synthesis in X-Irradiated HeLa Cells

1970 ◽  
Vol 44 (2) ◽  
pp. 456 ◽  
Author(s):  
R. Bases ◽  
F. Mendez ◽  
R. Nicolino
Keyword(s):  
Ribosomal Rna ◽  
Hela Cells ◽  
Rna Synthesis
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