On the fine structure of polyribosomes

Brökelmann, Jost

doi:10.1007/bf00219854

Cited by 2 publications

(2 citation statements)

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“…Previous studies have established that polysomes are associated with cytoskeletal elements in eukaryotic cells [Wolosewick and Porter, 1976;Brokelmann, 1977;van Venrooij et al, 1981;Moon et al, 1983;Ramaekers et al, 1983;Howe and Hershey, 19841, but the functional significance of this association is not understood [Nielsen et al, 19831. It is possible the cytoskeleton is required for protein synthesis or that it merely serves as a structural framework for to centrifugation.…”

Section: Discussionmentioning

confidence: 99%

“…It has been proposed that the cytoskeleton is also involved in protein synthesis [Nielsen et al, 19831. This proposal is based on ultrastructural observations of polysomes associated with cytoskeletal filaments [Wolosewick and Porter, 1976;Brokelmann, 1977;Ramaekers et al, 19831, the resistance of polysomes and mRNA to extraction with non-ionic detergents [Brokelmann 1977;van Venrooij et al, 1981;Jeffery, 1982;Moon et d, 1983;Jeffery, 1984, 19851, and the effects of cytochalasin on 0 1987 Alan R. Liss, Inc.…”

Section: Introductionmentioning

confidence: 97%

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Translational control and the cytoskeleton in Physarum polycephalum

Brodeur

Jeffery

1987

Cell Motil. Cytoskeleton

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Translationally active plasmodia of the syncytial slime mold Physarum polycephalum develop into translationally dormant sclerotia during starvation. Although functional mRNA and ribosomes exist in sclerotia, protein synthesis is suppressed at the level of initiation. To test the possibility that alterations in the cytoskeleton may limit protein synthesis, we have examined the distribution of polysomes and actin mRNA in the cytoskeletal (CSK) and soluble (SOL) fractions of Triton X-100-extracted plasmodia and sclerotia. Most of the polysomes and actin mRNA were located in the CSK of plasmodia, while most of the ribosomes and actin mRNA were located in the SOL of sclerotia. The results suggest that ribosomes and mRNA shift from the CSK to the SOL as protein synthesis is suppressed during starvation. Plasmodia and sclerotia can be induced to accumulate excess polysomes by treatment with low levels of the elongation inhibitor cycloheximide. Treatment of plasmodia with cycloheximide caused excess polysomes to accumulate in the SOL, suggesting that the CSK contains a limited capacity for binding translational components and that the association of polysomes with the cytoskeleton is not required for protein synthesis. Treatment of sclerotia with cycloheximide, however, caused polysomes and actin mRNA to accumulate in the CSK, suggesting that the sclerotial cytoskeleton, although depleted in ribosomes and mRNA, is capable of binding translational components. It is concluded that alterations in the sclerotial cytoskeleton are not involved in translational control.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Translational control and the cytoskeleton in Physarum polycephalum

Brodeur

Jeffery

1987

Cell Motil. Cytoskeleton

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Ultrastructural immunocytochemistry of nascent albumin topology: Proposed cytosolic folding and membrane transit of the protein

LeBouton

Masse

1981

Anat. Rec.

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The relationship of nascent albumin and hepatocyte organelles was studied with the immunoperoxidase reaction in rats given various drugs to alter cellular albumin content. colchicine was used to increase intracellular albumin. Cycloheximide inhibited synthesis but allowed nascent albumin to remain with its ribosome of origin. Puromycin also inhibited synthesis but released albumin from its ribosome. There was no difference in the appearance of attached ribosomes in hepatocytes from saline-injected rats and those given colchicine or cycloheximide. In these cases, membranes of the endoplasmic reticulum were consistently decorated with ribosomes positive for the presence of albumin antigenicity on their cytosolic surface. The cisternal and cytosolic compartments were negative. The situation after puromycin was different. Here the membranes appeared to be denuded of ribosomes and reaction product, indicative of albumin, was present only on the lumenal surface. To determine whether puromycin had caused the release of ribosomes, sections from puromycin-treated cells were stained nonspecifically with uranyl acetate. This showed that the normal amount of ribosomes was still bound but that they could not be seen when a probe specific only for albumin was used. It appears that nascent albumin can associate with its ribosome within the cytosol. Also, apparently after albumin passes through the membrane of the rough endoplasmic reticulum, it remains attached to its lumenal surface. A model incorporating cytosolic folding of albumin followed by its entropic membrane transit is presented.

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On the fine structure of polyribosomes

Cited by 2 publications

References 50 publications

Translational control and the cytoskeleton in Physarum polycephalum

Translational control and the cytoskeleton in Physarum polycephalum

Ultrastructural immunocytochemistry of nascent albumin topology: Proposed cytosolic folding and membrane transit of the protein

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