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Identification of a soluble precursor complex essential for nuclear pore assembly in vitro
M C Dabauvalle1, K Loos, U Scheer
1Institute of Zoology I, University of Würzburg, Federal Republic of Germany.
Chromosoma
|December 1, 1990
Summary
Nuclear pore complex protein p68 is stored in Xenopus eggs as a macromolecular assembly. Depleting p68 prevents nuclear pore formation, highlighting its essential role in nuclear transport and assembly.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Biochemistry
Background:
- Nuclear pore complexes (NPCs) regulate transport between the nucleus and cytoplasm.
- p68 is a major wheat germ agglutinin (WGA)-binding glycoprotein in Xenopus oocyte NPCs, located in the pore channel.
- p68 participates in the transport of karyophilic proteins.
Purpose of the Study:
- To analyze the soluble form of nuclear pore complex protein p68 in Xenopus laevis eggs.
- To investigate the involvement of p68 in nuclear pore complex assembly.
Main Methods:
- Immunoadsorption using a monoclonal antibody against p68 (PI1) to deplete Xenopus egg extract.
- Depletion of WGA-binding proteins from the extract.
- Reconstitution of nuclei in vitro.
- Analysis of immunoprecipitate by SDS-polyacrylamide gel electrophoresis.
- Sucrose gradient centrifugation and gel filtration.
Main Results:
- Depletion of p68 or WGA-binding proteins prevented nuclear pore complex assembly and karyophilic protein import, despite intact nuclear envelope formation.
- Nuclear membrane formation and pore complex assembly are independent processes.
- p68, along with associated proteins, forms a stable macromolecular complex (Mr 254,000).
Conclusions:
- p68 is essential for nuclear pore complex assembly and function.
- p68 exists as a pre-assembled complex, explaining its punctate cytoplasmic localization in mitotic cells.