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Visualizing nuclear export of different classes of RNA by electron microscopy
N Panté1, A Jarmolowski, E Izaurralde
1M.E. Müller Institute for Microscopy, Biozentrum, University of Basel,Switzerland. pante@ubaclu.unibas.ch
RNA (New York, N.Y.)
|May 1, 1997
Summary
Nuclear export of RNA via nuclear pore complexes (NPCs) was studied using gold-labeled RNAs in Xenopus oocytes. Exported RNAs followed specific kinetics, but U6 snRNA remained nuclear, suggesting distinct export pathways.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Nuclear export of RNA is crucial for gene expression.
- Nuclear pore complexes (NPCs) regulate transport between the nucleus and cytoplasm.
- Understanding RNA export mechanisms is vital for cellular function.
Purpose of the Study:
- To investigate the mechanism of RNA export through NPCs.
- To determine the role of NPCs in the transport of different RNA types.
- To identify potential docking sites for RNA export at NPCs.
Main Methods:
- Gold-labeling of various RNA types (mRNA, tRNA, U snRNAs).
- Microinjection into Xenopus oocyte nuclei.
- Observation of RNA export using electron microscopy (EM).
- Manipulation of conditions to study NPC docking and RNA export inhibition.
Main Results:
- Gold-tagged mRNA, tRNA, and U1 snRNA were efficiently exported, mimicking unlabeled RNA kinetics.
- U6 snRNA conjugates and naked U6 snRNA remained in the nucleus, indicating differential export.
- RNA-gold particles localized within the NPC central axis, nuclear basket, or channel periphery during export.
- Inhibition of export led to nucleoplasmic accumulation, not NPC docking, suggesting nucleoplasmic mobilization.
Conclusions:
- RNA export involves specific pathways, with U6 snRNA exhibiting unique nuclear retention.
- NPCs facilitate RNA export through defined channels, but initial docking sites remain elusive.
- Mobilization of RNA from the nucleoplasm to the NPC is a critical step in the export process.