scholarly journals Carcinogenesis and Cellular Injury. The effect of ethionine on ribonucleic acid synthesis in rat liver

1975 ◽  
Vol 150 (3) ◽  
pp. 335-344 ◽  
Author(s):  
P F Swann ◽  
A C Peacock ◽  
S Bunting
Keyword(s):  
Protein Synthesis ◽  
Rna Synthesis ◽  
Acid Synthesis ◽  
Female Rat ◽  
Concurrent Administration ◽  
Polyamine Synthesis ◽  
Rrna Maturation ◽  
Precursor Rna ◽  
Inhibitor Of Protein Synthesis ◽  
Ribosomal Precursor

1. By 1h after administration of ethionine to the female rat the appearance of newly synthesized 18SrRNA in the cytoplasm is completely inhibited. This is not caused by inhibition of RNA synthesis, for the synthesis of the large ribosomal precursor RNA (45S) and of tRNA continues. Cleavage of 45S RNA to 32S RNA also occurs, but there was no evidence for the accumulation of mature or immature rRNA in the nucleus. 2. The effect of ethionine on the maturation of rRNA was not mimicked by an inhibitor of protein synthesis (cycloheximide) or an inhibitor of polyamine synthesis [methylglyoxal bis(guanylhydrazone)]. 3. Unlike the ethionine-induced inhibition of protein synthesis, this effect was not prevented by concurrent administration of inosine. A similar effect could be induced in HeLa cells by incubation for 1h in a medium lacking methionine. The ATP concentration in these cells was normal. From these two observations it was concluded that the effect of etionine on rRNA maturation is not caused by an ethionine-induced lack of ATP. It is suggested that ethionine, by lowering the hepatic concentration of S-adenosylmethionine, prevents methylation of the ribosomal precursor. The methylation is essential for the correct maturation of the molecule; without methylation complete degradation occurs.

scholarly journals NUCLEAR ENVELOPE-ASSOCIATED RESUMPTION OF RNA SYNTHESIS IN LATE MITOSIS OF HELA CELLS

1973 ◽  
Vol 59 (1) ◽  
pp. 150-164 ◽  
Author(s):  
T. Simmons ◽  
P. Heywood ◽  
L. Hodge
Keyword(s):  
Protein Synthesis ◽  
Nuclear Envelope ◽  
Rna Synthesis ◽  
Electron Microscope Autoradiography ◽  
Molecular Synthesis ◽  
Hela S3 ◽  
Precursor Rna ◽  
Ribosomal Precursor ◽  
Hela S3 Cells ◽  
Silver Grains

The restitution of RNA synthesis in cultures progressing from metaphase into interphase (G1) has been investigated in synchronized HeLa S3 cells by using inhibitors of macro-molecular synthesis and the technique of electron microscope autoradiography. The rate of incorporation of radioactive uridine into RNA approached interphase levels in the absence of renewed protein synthesis. In contrast, maintenance of this rate in G1 was dependent upon renewed protein synthesis. Restoration of synthesis of heterogeneous nuclear RNA occurred under conditions that inhibited production of ribosomal precursor RNA. In autoradiographs of individual cells exposed to radioactive uridine, silver grains were first detected after nuclear envelope reformation at the periphery of the chromosome mass but before chromosomal decondensation. These data are consistent with the following interpretation. Multiple RNA polymerase activities persist through mitosis and are involved in the initiation of RNA synthesis in early telophase at sites on the nuclear envelope.

scholarly journals THE EFFECT OF PUROMYCIN ON INTRANUCLEAR STEPS IN RIBOSOME BIOSYNTHESIS

1968 ◽  
Vol 36 (1) ◽  
pp. 91-101 ◽  
Author(s):  
R. Soeiro ◽  
M. H. Vaughan ◽  
J. E. Darnell
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Rna ◽  
Cell Fractionation ◽  
Sequence Of Events ◽  
Inhibition Of Protein Synthesis ◽  
Precursor Rna ◽  
Initial Processing ◽  
Inhibitor Of Protein Synthesis ◽  
Ribosomal Precursor ◽  
Ribosome Biosynthesis

Inhibition of protein synthesis by puromycin (100 γ/ml) is known to inhibit the synthesis of ribosomes. However, ribosomal precursor RNA (45S) continues to be synthesized, methylated, and processed. Cell fractionation studies revealed that, although the initial processing (45S → 32S + 16S) occurs in the presence of puromycin, the 16S moiety is immediately degraded. No species of ribosomal RNA can be found to have emerged from the nucleolus. The RNA formed in the presence of puromycin is normal as judged by its ability to enter new ribosomal particles after puromycin is removed. This sequence of events is not a result of inhibition of protein synthesis, for cycloheximide, another inhibitor of protein synthesis, either alone or in combination with puromycin allows the completion of new ribosomes.

Protein and Nucleic Acid Syntheses in Dark-dormant Common Purslane(Portulaca oleracea)Seed

Weed Science ◽  
1978 ◽  
Vol 26 (6) ◽  
pp. 669-672 ◽  
Author(s):  
Bonnie J. Reger ◽  
Ida E. Yates
Keyword(s):  
Protein Synthesis ◽  
Nucleic Acid ◽  
Rna Synthesis ◽  
Acid Synthesis ◽  
Portulaca Oleracea ◽  
Dark Incubation ◽  
Radicle Protrusion ◽  
Lag Period ◽  
Common Purslane ◽  
H Protein

Dark-incubated common purslane(Portulaca oleraceaL.) seed synthesize very little protein and essentially no nucleic acids. Dark-incubated seed incorporate only 14 × 10−3nmoles14C-leucine/mg protein/12-h dark. In contrast, seed exposed to 12-h light following 24-h dark incubation incorporate 365 × 10−3-nmoles14C-leucine/mg protein/12-h light. Once dormancy is broken by exposure of seed to light, initiation of radicle protrusion occurs at 12 h. Protein synthesis gradually increases with time in the light and precedes nucleic acid synthesis which is associated with radicle protrusion. During the 12-h lag period preceding radicle protrusion protein synthesis increases significantly by 3 to 9 h in light, RNA synthesis by 9 h in light, and DNA synthesis by 12 h in light. After 12 h in light,32P can be detected in all nucleic acid fractions, DNA and RNAs.

scholarly journals Mechanism of action of purpuromycin

1992 ◽  
Vol 284 (1) ◽  
pp. 47-52 ◽  
Author(s):  
P Landini ◽  
E Corti ◽  
B P Goldstein ◽  
M Denaro
Keyword(s):  
Protein Synthesis ◽  
Rna Synthesis ◽  
Intact Cell ◽  
Acid Synthesis ◽  
Free System ◽  
Dna And Rna ◽  
Dna And Rna Synthesis ◽  
Dependent Protein ◽  
Elongation Step

Purpuromycin, an antibiotic active against both fungi and bacteria, shows different modes of action against these two kinds of micro-organisms; in Candida albicans it inhibits RNA synthesis, whereas in Bacillus subtilis protein synthesis is primarily affected, with DNA and RNA synthesis blocked at higher concentrations of the drug. In bacterial cell-free protein-synthesis systems, purpuromycin did not inhibit synthesis from endogenous mRNA (elongation of peptides initiated within the intact cell) but inhibited MS2-phase RNA-dependent protein synthesis (which requires initiation) by 50% at 0.1 mg/l. Poly(U)-directed polyphenylalanine synthesis was 50% inhibited by 20 mg of purpuromycin/l when added to a complete system; however, when purpuromycin was preincubated with ribosomes dissociated into 30 S and 50 S subunits, the concentration for 50% inhibition fell to 0.1 mg/l. By contrast, in a C. albicans cell-free system poly(U)-directed polyphenylalanine synthesis was partially inhibited only at 200 mg/l. Purpuromycin also inhibited polynucleotide synthesis in vitro in reactions using Escherichia coli or wheat-germ RNA polymerases or E. coli DNA polymerase I. We suggest that in bacteria the primary target of purpuromycin is on ribosomes and that its action precedes the elongation step of protein synthesis. The effect on nucleic acid synthesis in both fungi and bacteria may be due to interaction of purpuromycin with DNA.

Introduction: virus–host interactions

1980 ◽  
Vol 210 (1180) ◽  
pp. 319-320
Keyword(s):  
Protein Synthesis ◽  
Messenger Rna ◽  
Rna Synthesis ◽  
Genetic Material ◽  
Acid Synthesis ◽  
Dna Viruses ◽  
Host Interactions ◽  
Polypeptide Sequence ◽  
Form Part ◽  
Reading Frames

Viruses are among the most extreme parasites, being almost completely dependent upon their host for their growth and replication. Having no intermediary metabolism of their own they make use of the energy supply of the host, its production of nucleoside triphosphates for nucleic acid synthesis and amino acid for protein synthesis, and all of the machinery for protein synthesis. Within the infected cell the virus competes with the host for the supply of all these things and at the same time variants compete among themselves for survival and yield of progeny. It is the intensity of this competition that has produced the most subtle and intimate interactions between virus and host. The need to fit into a protective shell imposes tight limits on the size of the genome in most classes of virus. This means that additional functions can seldom be added simply by adding the necessary genetic information unless there is a compensating loss. But by making more efficient use of the genetic material, additional functions can be accommodated without altering the size of the genome significantly. This is seen to a remarkable degree in the small DNA viruses, where segments of the genome are translated in different reading frames to give different polypeptide sequences and where multiple alternative'splicing in messenger RNA synthesis allows the same polypeptide sequence to form part of two or even three proteins with different properties.

scholarly journals Ribonucleic acid labelling and nucleotide pools during compensatory renal hypertrophy

1974 ◽  
Vol 144 (3) ◽  
pp. 447-453 ◽  
Author(s):  
J M Hill ◽  
G Ab ◽  
R A Malt
Keyword(s):  
Rna Synthesis ◽  
Single Injection ◽  
Specific Radioactivity ◽  
Compensatory Hypertrophy ◽  
Rrna Synthesis ◽  
Renal Hypertrophy ◽  
Rna Content ◽  
Compensatory Renal Hypertrophy ◽  
Precursor Rna ◽  
Ribosomal Precursor

During the first 48h of compensatory renal hypertrophy induced by unilateral nephrectomy, RNA content per cell increased by 20–40%. During this period, rates of RNA synthesis derived from the rates of labelling of UTP and RNA after a single injection of [5-3H]uridine showed no change in the rate of RNA synthesis (3.1nmol of UTP incorporated into RNA/min per mg of RNA). ATP and ADP pools were not changed. The rate of RNA synthesis was considerably in excess of the increment of total RNA appearing in the kidneys. With [5-3H]uridine as label, only continuous infusion for 24h could produce an increase (60%) in the specific radioactivity of renal rRNA in mice with contralateral nephrectomies. With a single injection of [methyl-3H]methionine used to identify methyl groups inserted into newly synthesized rRNA, the specific radioactivity of this rRNA was unchanged 5h after contralateral nephrectomy, increased by 60% at 9–48h, and returned to normal values at 120h. Most RNA synthesized in both nephrectomized and sham-nephrectomized mice has a short half-life. Since total cellular RNA content increases in compensatory hypertrophy despite unchanged rates of rRNA synthesis, the accretion of RNA might involve conservation of ribosomal precursor RNA or a change in rate of degradation of mature rRNA.

scholarly journals Induction of human choriogonadotropin in HeLa-cell cultures by aliphatic monocarboxylates and inhibitors of deoxyribonucleic acid synthesis

1977 ◽  
Vol 166 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Nimai K. Ghosh ◽  
Adriana Rukenstein ◽  
Rody P. Cox
Keyword(s):  
Protein Synthesis ◽  
Hela Cell ◽  
Dna Synthesis ◽  
Hela Cells ◽  
Fold Increase ◽  
Short Chain Fatty Acids ◽  
Acid Synthesis ◽  
Hydroxyl Groups ◽  
Β Subunit ◽  
Inhibitor Of Protein Synthesis

The ectopic production of the glycopeptide hormone human placental choriogonadotropin by HeLa65 cells was measured by radioimmunoassay with antiserum against the β-subunit of choriogonadotropin and with the125I-labelled β-subunit as a tracer antigen. Choriogonadotropin synthesis was markedly (500-fold) stimulated by sodium butyrate. Kinetic studies and the use of an inhibitor of protein synthesis, cycloheximide, indicated that protein synthesis was required for this induction. Investigation of the efficiency of 22 aliphatic short-chain fatty acids and derivatives in causing increased choriogonadotropin synthesis by HeLa cells showed stringent structural requirements. Induction of choriogonadotropin synthesis in HeLa cells was not restricted to butyrate. Other aliphatic acids (propionate, isobutyrate, valerate and hexanoate) were also capable of inducing choriogonadotropin synthesis at 10–50% of the efficiency of butyrate. Hydroxy derivatives of monocarboxylate inducers, related mono- and di-carboxylic acids, alcohols, amines, ketones, esters and sulphoxide were ineffective in increasing choriogonadotropin production by HeLa cells. A saturated C4 straight-chain acid without substituent hydroxyl groups but with a methyl group at one end and a carboxyl moiety at the other appeared to be most efficient in activating choriogonadotropin production. A second clonal line of HeLa cells, HeLa71, showed a higher constitutive synthesis of choriogonadotropin than HeLa65 cells, which was also markedly increased by butyrate. Butyrate and other aliphatic monocarboxylate inducers of choriogonadotropin synthesis inhibited HeLa-cell growth and DNA synthesis. This inhibition of DNA replication may be related to the mechanism of choriogonadotropin synthesis, since two well-characterized anti-neoplastic inhibitors of DNA synthesis, hydroxyurea and 1-β-d-arabinofuranosylcytosine, also stimulated a 300-fold increase in choriogonadotropin synthesis in HeLa cells and were synergistic with butyrate in promoting choriogonadotropin synthesis. Thus activation in tumour cells of genes normally expressed by foetal tissue and the consequent ectopic synthesis of polypeptide hormones may require neither cell division nor DNA synthesis.

scholarly journals Induction of a rapidly responsive hepatic gene product by thyroid hormone requires ongoing protein synthesis.

1987 ◽  
Vol 7 (4) ◽  
pp. 1352-1357 ◽  
Author(s):  
D B Jacoby ◽  
J A Engle ◽  
H C Towle
Keyword(s):  
Protein Synthesis ◽  
Thyroid Hormone ◽  
Time Course ◽  
Primary Response ◽  
Receptor Interaction ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Spot 14 ◽  
Precursor Rna ◽  
Inhibitor Of Protein Synthesis

The regulation of a gene, designated spot 14, which is rapidly induced in rat liver in response to 3,5,3'-triiodo-L-thyronine (T3) was studied as a model for exploring the molecular basis of thyroid hormone action. The time course of induction of the nuclear precursor to spot 14 mRNA after intramuscular injection of T3 displayed a very short lag period of between 10 and 20 min. The rapidity of this effect suggests that the induction in gene expression occurs as a primary response to the hormone-receptor interaction. The protein synthesis inhibitor cycloheximide injected 15 min before T3 completely blocked the accumulation of nuclear precursor RNA 30 min after T3 treatment. Emetine, an inhibitor of protein synthesis which acts by a different mechanism than cycloheximide, also blocked the induction of the spot 14 nuclear precursor RNA. The increased rate of spot 14 gene transcription observed after T3 treatment, as measured by nuclear run-on assay, was similarly completely abolished in the presence of cycloheximide. In addition, ongoing protein synthesis was required for maintaining spot 14 nuclear precursor RNA at induced levels in animals previously treated with T3. On the other hand, cycloheximide had no effect on T3 uptake or binding to the nuclear receptor during the 45-min time frame studied. The paradox of the rapid kinetics of induction and the requirement of ongoing protein synthesis may be explained by a protein with an extremely short half-life which is necessary for T3 induction of the spot 14 gene.

Induction of a rapidly responsive hepatic gene product by thyroid hormone requires ongoing protein synthesis

1987 ◽  
Vol 7 (4) ◽  
pp. 1352-1357
Author(s):  
D B Jacoby ◽  
J A Engle ◽  
H C Towle
Keyword(s):  
Protein Synthesis ◽  
Thyroid Hormone ◽  
Time Course ◽  
Primary Response ◽  
Receptor Interaction ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Spot 14 ◽  
Precursor Rna ◽  
Inhibitor Of Protein Synthesis

The regulation of a gene, designated spot 14, which is rapidly induced in rat liver in response to 3,5,3'-triiodo-L-thyronine (T3) was studied as a model for exploring the molecular basis of thyroid hormone action. The time course of induction of the nuclear precursor to spot 14 mRNA after intramuscular injection of T3 displayed a very short lag period of between 10 and 20 min. The rapidity of this effect suggests that the induction in gene expression occurs as a primary response to the hormone-receptor interaction. The protein synthesis inhibitor cycloheximide injected 15 min before T3 completely blocked the accumulation of nuclear precursor RNA 30 min after T3 treatment. Emetine, an inhibitor of protein synthesis which acts by a different mechanism than cycloheximide, also blocked the induction of the spot 14 nuclear precursor RNA. The increased rate of spot 14 gene transcription observed after T3 treatment, as measured by nuclear run-on assay, was similarly completely abolished in the presence of cycloheximide. In addition, ongoing protein synthesis was required for maintaining spot 14 nuclear precursor RNA at induced levels in animals previously treated with T3. On the other hand, cycloheximide had no effect on T3 uptake or binding to the nuclear receptor during the 45-min time frame studied. The paradox of the rapid kinetics of induction and the requirement of ongoing protein synthesis may be explained by a protein with an extremely short half-life which is necessary for T3 induction of the spot 14 gene.

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