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Spatial and temporal control of nuclear envelope assembly by Ran GTPase
Paul R Clarke1, Chuanmao Zhang
1Ninewells Hospital and Medical School, University of Dundee, Scotland.
Symposia of the Society for Experimental Biology
|November 30, 2004
Summary
The small GTPase Ran, concentrated on chromatin, drives nuclear envelope (NE) assembly by recruiting vesicles and promoting NPC formation. Its regulated localization controls NE formation timing during cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- Nuclear envelope (NE) assembly is crucial for cell division and function.
- The small GTPase Ran plays a key role in nuclear transport and cell cycle regulation.
- Understanding Ran's precise role in NE formation is essential for comprehending cell division.
Purpose of the Study:
- To propose a model for the role of Ran in nuclear envelope (NE) assembly using Xenopus egg extracts.
- To elucidate the mechanisms by which Ran-GTP recruits and fuses membrane vesicles to form the NE.
- To investigate how Ran facilitates nuclear pore complex (NPC) assembly during NE formation.
Main Methods:
- Studies using Xenopus egg extracts as a model system.
- Analysis of Ran localization on chromatin before and during NE assembly.
- Investigating the interaction of Ran-GTP with importin-beta and nucleoporins.
Main Results:
- Ran is concentrated on chromatin, recruiting RCC1 to generate local Ran-GTP.
- Ran-GTP recruits and fuses membrane vesicles to form the NE, potentially via importin-beta.
- Ran-GTP promotes NPC assembly by releasing nucleoporins from inhibitory complexes.
Conclusions:
- Ran localization to chromatin is a key regulator of NE assembly timing at the end of mitosis.
- Ran-GTP facilitates both membrane fusion for NE formation and NPC assembly.
- The dynamic localization of Ran and its regulators provides spatiotemporal control over NE assembly.