scholarly journals Direct association of messenger RNA labeled in the presence of fluoroorotate with membranes of the endoplasmic reticulum in rat liver.

1976 ◽  
Vol 70 (1) ◽  
pp. 47-58 ◽  
Author(s):  
J Cardelli ◽  
B Long ◽  
H C Pitot
Keyword(s):  
Endoplasmic Reticulum ◽  
Ribosomal Rna ◽  
Messenger Rna ◽  
Translational Regulation ◽  
Orotic Acid ◽  
Complete Removal ◽  
High Ionic Strength ◽  
Messenger Rnas ◽  
Direct Association ◽  
Pancreatic Rnase

Liver rough endoplasmic reticulum (RER) membranes were isolated from rats given [3H]orotic acid for 48 h (ribosomal RNA [rRNA] label) or for 3 h along with 5-fluoroorotate; this latter procedure permits the labeling of cytoplasmic messenger RNAs (mRNAs) in the absence of rRNA labeling. More than 50% of the labeled mRNA remained attached to membranes of the RER after complete removal of ribosomes with a buffer of high ionic strength in the presence of puromycin. Under similar conditions, membranes retained 40% of their polyadenylate as determined by a [3H]-polyuridylate hybridization assay. Treatment of mRNA-labeled endoplasmic reticulum membranes with pancreatic RNase indicates that the polyadenylate and possibly nonpolyadenylate-pyrimidine portions of the messenger are involved in the binding of mRNA to the membranes. The implication of these results in furthering our understanding of the mechanisms of the translational regulation of genetic expression is discussed.

scholarly journals Synthesis and turnover of mitochondrial ribonucleic acid in HeLa cells: the mature ribosomal and messenger ribonucleic acid species are metabolically unstable.

1981 ◽  
Vol 1 (6) ◽  
pp. 497-511 ◽  
Author(s):  
R Gelfand ◽  
G Attardi
Keyword(s):  
Ribosomal Rna ◽  
Hela Cells ◽  
Ribonucleic Acid ◽  
Half Life ◽  
Messenger Rna ◽  
Specific Activity ◽  
Mitochondrial Rna ◽  
Messenger Rnas ◽  
Precursor Pool ◽  
Messenger Ribonucleic Acid

The synthesis rates and half-lives of the individual mitochondrial ribosomal ribonucleic acid (RNA) and polyadenylic acid-containing RNA species in HeLa cells have been determined by analyzing their kinetics of labeling with [5-3H]-uridine and the changes in specific activity of the mitochondrial nucleotide precursor pools. In one experiment, a novel method for determining the nucleotide precursor pool specific activities, using nascent RNA chains, has been utilized. All mitochondrial RNA species analyzed were found to be metabolically unstable, with half-lives of 2.5 to 3.5 h for the two ribosomal RNA components and between 25 and 90 min for the various putative messenger RNAs. A cordycepin "chase" experiment yielded half-life values for the messenger RNA species which were, in general, larger by a factor of 1.5 to 2.5 than those estimated in the labeling kinetics experiments. On the basis of previous observations, a model is proposed whereby the rate of mitochondrial RNA decay is under feedback control by some mechanism linked to RNA synthesis or processing. A short half-life was determined for five large polyadenylated RNAs, which are probably precursors of mature species. A rate of synthesis of one to two molecules per minute per cell was estimated for the various H-strand-coded messenger RNA species, and a rate of synthesis 50 to 100 times higher was estimated for the ribosomal RNA species. These data indicate that the major portion of the H-strand in each mitochondrial deoxyribonucleic acid molecule is transcribed very infrequently, possibly as rarely as once or twice per cell generation. Furthermore, these results are consistent with a previously proposed model of H-strand transcription in the form of a single polycistronic molecule.

scholarly journals CAR-1 and Trailer hitch: driving mRNP granule function at the ER?

2006 ◽  
Vol 173 (2) ◽  
pp. 159-163 ◽  
Author(s):  
Carolyn J. Decker ◽  
Roy Parker
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Fate ◽  
Translational Control ◽  
Translational Regulation ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Spindle Pole ◽  
Axis Formation ◽  
Cell Fate Determination ◽  
Messenger Rnas

The targeting of messenger RNAs (mRNAs) to specific subcellular sites for local translation plays an important role in diverse cellular and developmental processes in eukaryotes, including axis formation, cell fate determination, spindle pole regulation, cell motility, and neuronal synaptic plasticity. Recently, a new conserved class of Lsm proteins, the Scd6 family, has been implicated in controlling mRNA function. Depletion or mutation of members of the Scd6 family, Caenorhabditis elegans CAR-1 and Drosophila melanogaster trailer hitch, lead to a variety of developmental phenotypes, which in some cases can be linked to alterations in the endoplasmic reticulum (ER). Scd6/Lsm proteins are RNA binding proteins and are found in RNP complexes associated with translational control of mRNAs, and these complexes can colocalize with the ER. These findings raise the possibility that localization and translational regulation of mRNAs at the ER plays a role in controlling the organization of this organelle.

scholarly journals Synthesis and turnover of mitochondrial ribonucleic acid in HeLa cells: the mature ribosomal and messenger ribonucleic acid species are metabolically unstable

1981 ◽  
Vol 1 (6) ◽  
pp. 497-511
Author(s):  
R Gelfand ◽  
G Attardi
Keyword(s):  
Ribosomal Rna ◽  
Hela Cells ◽  
Ribonucleic Acid ◽  
Half Life ◽  
Messenger Rna ◽  
Specific Activity ◽  
Mitochondrial Rna ◽  
Messenger Rnas ◽  
Precursor Pool ◽  
Messenger Ribonucleic Acid

The synthesis rates and half-lives of the individual mitochondrial ribosomal ribonucleic acid (RNA) and polyadenylic acid-containing RNA species in HeLa cells have been determined by analyzing their kinetics of labeling with [5-3H]-uridine and the changes in specific activity of the mitochondrial nucleotide precursor pools. In one experiment, a novel method for determining the nucleotide precursor pool specific activities, using nascent RNA chains, has been utilized. All mitochondrial RNA species analyzed were found to be metabolically unstable, with half-lives of 2.5 to 3.5 h for the two ribosomal RNA components and between 25 and 90 min for the various putative messenger RNAs. A cordycepin "chase" experiment yielded half-life values for the messenger RNA species which were, in general, larger by a factor of 1.5 to 2.5 than those estimated in the labeling kinetics experiments. On the basis of previous observations, a model is proposed whereby the rate of mitochondrial RNA decay is under feedback control by some mechanism linked to RNA synthesis or processing. A short half-life was determined for five large polyadenylated RNAs, which are probably precursors of mature species. A rate of synthesis of one to two molecules per minute per cell was estimated for the various H-strand-coded messenger RNA species, and a rate of synthesis 50 to 100 times higher was estimated for the ribosomal RNA species. These data indicate that the major portion of the H-strand in each mitochondrial deoxyribonucleic acid molecule is transcribed very infrequently, possibly as rarely as once or twice per cell generation. Furthermore, these results are consistent with a previously proposed model of H-strand transcription in the form of a single polycistronic molecule.

DEGRADATION OF MESSENGER RNA IN MAMMALIAN CELLS

1972 ◽  
Vol 71 (2_Suppla) ◽  
pp. S369-S380 ◽  
Author(s):  
Francis T. Kenney ◽  
Kai-Lin Lee ◽  
Charles D. Stiles
Keyword(s):  
Messenger Rna ◽  
Mammalian Cells ◽  
Messenger Rnas ◽  
Tyrosine Transaminase

ABSTRACT Analyses of the response of hydrocortisone-induced tyrosine transaminase in cultured H-35 cells to inhibitors of translation (cycloheximide, puromycin) suggest: (1) that bound ribosomes stabilize messenger RNA in vivo; (2) that messenger is degraded at a rate determined by the rate of translation. Since specific messenger RNAs of mammalian cells are degraded at quite different rates, there may be extensive heterogeneity either in the rate at which ribosomes traverse different messengers or in the number of ribosomes which translate specific messenger RNAs.

scholarly journals STUDIES ON THE FUNCTION OF INTRACELLULAR RIBONUCLEASES

1966 ◽  
Vol 29 (3) ◽  
pp. 395-403 ◽  
Author(s):  
Takeshi Utsunomiya ◽  
Jay S. Roth
Keyword(s):  
Natural Products ◽  
Sodium Chloride ◽  
Rat Liver ◽  
Messenger Rna ◽  
Rnase Activity ◽  
Optimum Ph ◽  
Normal Rat ◽  
Pancreatic Rnase ◽  
The Stability ◽  
Normal Constituent

The RNase activity and properties of ribosome and polysome preparations from normal rat liver and some hepatomas have been examined. Polysome and ribosome preparations from the Novikoff, McCoy MDAB, and Dunning hepatomas had considerably higher specific RNase activity than corresponding preparations from normal rat liver, Novikoff ascites, or Morris 5123 hepatomas. The optimum pH of the RNase was approximately 8.5 for all samples tested, and the samples showed no evidence of latent RNase activity when treated with 3 M sodium chloride, EDTA, urea, or p-chloromercuribenzenesulfonic acid. The RNase activity appeared to be associated principally with breakdown products and/or subunits smaller than 80S. In the presence of Mg++ ions, subunits could reaggregate to form monomer ribosomes indistinguishable from the natural products, but some of the reassociated ribosomes could contain RNase activity which had been bound to the smaller particles. Similar results were obtained with spermine. In the hepatomas, evidence was obtained for the preexistence of considerable amounts of the smaller, RNase-containing subunits in the cell. When a small amount of crystalline bovine pancreatic RNase was added to partly dissociated ribosomes, the RNase was found only in association with the smaller subunits, and little or no enzyme was taken up by ribosomes or polysomes. The results have led to the conclusion that RNase is not a normal constituent of the ribosome or polysome, but that RNase may become associated with these particulates if dissociation and reassociation take place. Some implications of these findings for the stability of messenger RNA and for the mechanism of its breakdown are discussed.

An Electron-Microscope Study of the in vitro Transformation of Human Leucocytes

1967 ◽  
Vol 2 (3) ◽  
pp. 359-370
Author(s):  
J. A. CHAPMAN ◽  
M. W. ELVES ◽  
J. GOUGH
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Messenger Rna ◽  
Human Peripheral Blood ◽  
Limited Extent ◽  
Single Particles ◽  
Blast Cells ◽  
Protein Secreting

Electron-microscope studies of cultured small lymphocytes from human peripheral blood transforming into larger blastoid cells in the presence of phytohaemagglutinin (PHA) show that the transformed cell possesses the preliminary stages of development of a protein-synthesizing system. The transformed blastoid cell has abundant ribosomes, although, in contrast with in vivo protein-secreting cells, many of these occur as single particles with only a small proportion Linked in polysomal clusters. Endoplasmic reticulum membranes occur to a very limited extent and with a marked paucity of attached ribosomal particles; the few attached particles are usually located in groups. Some endoplasmic reticulum membranes revealed degenerative changes in otherwise normal cells. A moderately well-developed Golgi apparatus was a characteristic feature of the cells. Apart from the relatively low proportion of polysomes, in vitro PHA-transformed blastoid cells are identical in fine structure to in vivo blast cells (otherwise known as immunoblasts, haemocytoblasts, etc.) occurring in the immune response. It is suggested that messenger-RNA production in PHA-stimulated transformed cells may be reduced and that this could explain the limited number of polysomes and the restricted development of the endoplasmic reticulum.

scholarly journals Transient Cerebral Ischemia Activates Processing of xbp1 Messenger RNA Indicative of Endoplasmic Reticulum Stress

2003 ◽  
Vol 23 (4) ◽  
pp. 449-461 ◽  
Author(s):  
Wulf Paschen ◽  
Christoph Aufenberg ◽  
Svenja Hotop ◽  
Thorsten Mengesdorf
Keyword(s):  
Endoplasmic Reticulum ◽  
Cerebral Ischemia ◽  
Er Stress ◽  
Messenger Rna ◽  
Stress Proteins ◽  
Focal Cerebral Ischemia ◽  
Signal Transduction Pathway ◽  
Transient Cerebral Ischemia ◽  
Mrna Levels ◽  
Xbp1 Mrna

Cells respond to conditions associated with endoplasmic reticulum (ER) dysfunction with activation of the unfolded protein response, characterized by a shutdown of translation and induction of the expression of genes coding for ER stress proteins. The genetic response is based on IRE1-induced processing of xbp1 messenger RNA (mRNA), resulting in synthesis of new XBP1proc protein that functions as a potent transcription factor for ER stress genes. xbp1 processing in models of transient global and focal cerebral ischemia was studied. A marked increase in processed xbp1 mRNA levels during reperfusion was observed, most pronounced (about 35-fold) after 1-h occlusion of the right middle cerebral artery. The rise in processed xbp1 mRNA was not paralleled by a similar increase in XBP1proc protein levels because transient ischemia induces severe suppression of translation. As a result, mRNA levels of genes coding for ER stress proteins were only slightly increased, whereas mRNA levels of heat-shock protein 70 rose about 550-fold. Under conditions associated with ER dysfunction, cells require activation of the entire ER stress-induced signal transduction pathway, to cope with this severe form of stress. After transient cerebral ischemia, however, the block of translation may prevent synthesis of new XBP1proc protein and thus hinder recovery from ischemia-induced ER dysfunction.

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