The Sphere Organelle Contains Small Nuclear Ribonucleoproteins

We show by immunofluorescence microscopy of amphibian oocyte nuclei that small nuclear ribonucleoproteins (snRNPs) occur in lampbrush chromosome loops, in a few dozen extrachromosomal organelles previously described as ``spheres,'' and in thousands of smaller granules. Spheres are variable...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1989-09, Vol.86 (17), p.6635-6639
Main Authors: Gall, Joseph G., Callan, Harold G.
Format: Article
Language:English
Subjects:
Acheta domesticus
Animals
Biological and medical sciences
Cell nucleolus
Cell structures and functions
Chromatin
Chromosomes
Chromosomes - ultrastructure
Fluorescence
Fluorescent Antibody Technique
Fundamental and applied biological sciences. Psychology
Genetic loci
Image contrast
Microscopy, Phase-Contrast
Miscellaneous
Molecular and cellular biology
Notophthalmus viridescens
Oocytes
Organelles
Organelles - ultrastructure
Orthoptera
Ribonucleoproteins - analysis
Ribonucleoproteins, Small Nuclear
Small nuclear ribonucleoproteins
Small nuclear RNA
Species Specificity
Spiders
Xenopus laevis
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Summary:We show by immunofluorescence microscopy of amphibian oocyte nuclei that small nuclear ribonucleoproteins (snRNPs) occur in lampbrush chromosome loops, in a few dozen extrachromosomal organelles previously described as ``spheres,'' and in thousands of smaller granules. Spheres are variable in size (up to ≈ 20 μ m in diameter in the newt Notophthalmus and ≈ 10 μ m in the frog Xenopus) and are easily distinguishable from nucleoli by morphology and composition. Spheres occur both free in the nucleoplasm and attached to specific chromosome loci, the sphere organizers. Oocyte nuclei of a cricket and a spider contain essentially similar organelles, suggesting that spheres may be common throughout the animal kingdom. We suggest that spheres play a role in the assembly of snRNP complexes for the nucleus comparable to the way that nucleoli assemble ribosomal RNP complexes for the cytoplasm.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.86.17.6635