The ? 20 S cylinder particles of Xenopus laevis: Experimental findings and open questions

Kleinschmidt, Jürgen A.; Buhl, W J

doi:10.1007/bf00356913

Cited by 3 publications

(1 citation statement)

References 5 publications

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“…The debate (90--92) centers on whether all of the different "ring body" preparations are in fact the same, and whether they indeed contain stoichiometric, or even significant, amounts of RNAs. Careful analysis of the particles from Xenopus oocytes failed to reveal evidence for a specific RNA component (90), however, these particles, defined by their ringlike morphology, size, and a characteristic set of proteins, are apparently ubiquitous from plants to man and it may be that the particles show either species or cell-type differences in composition. Their "legitimacy" as RNPs notwithstanding, there is now the interesting possibility that at least some of these ring bodies are, or at least copurify with, large multifunctional proteases (93,94) and as such may be important elements in protein turnover.…”

Section: Cytoplasmic Eventsmentioning

confidence: 99%

Ribonucleoprotein particles in cellular processes.

Dreyfuss

Philipson

Mattaj

1988

The Journal of Cell Biology

121

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THE general way of thinking about the pathway of expression of genetic information in eukaryotes, from DNA to protein via RNA, instills a protein-centric point of view, as if the protein is the real goal and the RNA is just the intermediate. In fact, most of the RNA in the cell is not mRNA but rather part of modular structures, RNA-protein machines, that are termed ribonucleoprotein (RNP) particles or ribonucleoprorein complexes. The ribosome is one well-known example of such a complex. What is new and surprising is the discovery of the tremendous variety, complexity, and versatility of RNP particles which is reflected by the wide range of cellular processes in which they are involved.RNPs are involved in each step along the pathway of gene expression in eukaryotes, mRNAs are formed from precursor transcripts (hnRNAs or pre-mRNAs) by splicing of introns, and transported to the cytoplasm where each needs to accumulate to the precise level that will produce the correct amount of the particular protein. What has emerged over the past few years is that key components involved in processing pre-mRNA are complexes of unique small RNAs (snRNAs) with specific proteins, small nuclear ribonucleoprotein particles (snRNPs). The nuclear precursor transcripts themselves are in fact also RNPs, being complexed with specific proteins, the hnRNP proteins, as are cytoplasmic mRNAs which are associated with the mRNP proteins. Parts of the protein synthetic machinery, particularly ribosomes, are also complexes of proteins with RNA. The continual and dynamic association of messenger RNAs and their precursor hnRNA molecules with specific sets of proteins in the cell underscores the importance of understanding the molecular nature of these hnRNP and mRNP complexes.Recent work from numerous laboratories has led to the discovery of many additional RNP particles that are involved in an unexpected variety of cellular processes including protein targeting, priming of mitochondrial DNA synthesis, and transcription termination (see Table I). Here we review some of the most recent findings on the structure, composition, and function of RNP particles in the eukaryotic cell. Ribosomes, mRNPs, and viral RNPs are not discussed here. Also, since several reviews (1-6) have been published over the last two years that discuss pre-mRNA processing, we confine the discussion to only the most recent data in this rapidly advancing field.

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Section: Cytoplasmic Eventsmentioning

confidence: 99%

Ribonucleoprotein particles in cellular processes.

Dreyfuss

Philipson

Mattaj

1988

The Journal of Cell Biology

121

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The protein of M_r 21 000 constituting the prosome‐like particle of duck erythroblasts is homologous to apoferritin

Coux

Camoin

Nothwang

et al. 1992

European Journal of Biochemistry

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In duck erythroblasts, two major populations of untranslated messenger (m) RNP can be separated by sucrose gradient centrifugation in low ionic strength. One of these contains globin mRNA associated to protein factors, among them the prosomes. The other, sedimenting in the 35S zone, contains non‐globin mRNA. From this ‘35S’ mRNP, a new RNP particle called the prosome‐like particle was isolated and characterized [Akhayat, O., Infante, A. A., Infante, D., Martins de Sa, C., Grossi de Sa, M.‐F. & Scherrer, K. (1987) Eur. J. Biochem. 170, 23–33]. The PLP is a multimer of a protein of Mr 21000, and contains small RNA species. The particle is tightly associated with repressed mRNA and inhibits in vitro protein synthesis. We show here that the protein of Mr 21000, constituting the prosome‐like particle, is apoferritin. Different approaches confirm the RNP character of this particle and provide evidence that some of its RNA species are tRNA. The hypothesis is discussed as to whether (apo–)ferritin might serve other functions in addition to iron storage.

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Cytolocation of prosome antigens on intermediate filament subnetworks of cytokeratin, vimentin and desmin type

Olink-Coux

Arcangeletti

Pinardi

et al. 1994

Journal of Cell Science

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Analysis by double-label indirect immunofluorescence of PtK1 and HeLa cells had previously demonstrated that prosome* antigens form networks that superimpose on those of the intermediate filaments of the cytokeratin type. We show here that in PtK1 cells various prosomal antigens also reside to a variable extent on intermediate filaments subnetworks of the vimentin type. In proliferating human fibroblasts the prosome and vimentin networks were found to coincide, while in proliferating myoblasts of the C2.7 mouse myogenic cell line the prosomal antigens seem to superimpose on the intermediate filaments of the desmin type. Thus, the prosomes, which are RNP particles of variable composition and subcomplexes of untranslated mRNP, and carry a multicatalytic proteinase activity, seem to co-localize with the specific kind of cytoplasmic intermediate filament in relation to the cell type. These results, which generalize the previous data, are discussed in view of possible role(s) for prosomes in mRNA metabolism and/or intermediate filaments remodelling.

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The ? 20 S cylinder particles of Xenopus laevis: Experimental findings and open questions

Cited by 3 publications

References 5 publications

Ribonucleoprotein particles in cellular processes.

Ribonucleoprotein particles in cellular processes.

The protein of M_r 21 000 constituting the prosome‐like particle of duck erythroblasts is homologous to apoferritin

Cytolocation of prosome antigens on intermediate filament subnetworks of cytokeratin, vimentin and desmin type

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The ? 20 S cylinder particles of Xenopus laevis: Experimental findings and open questions

Cited by 3 publications

References 5 publications

Ribonucleoprotein particles in cellular processes.

Ribonucleoprotein particles in cellular processes.

The protein of Mr 21 000 constituting the prosome‐like particle of duck erythroblasts is homologous to apoferritin

Cytolocation of prosome antigens on intermediate filament subnetworks of cytokeratin, vimentin and desmin type

Contact Info

Product

Resources

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The protein of M_r 21 000 constituting the prosome‐like particle of duck erythroblasts is homologous to apoferritin