Ran-GTP stabilises microtubule asters and inhibits nuclear assembly in Xenopus egg extracts

Chuanmao Zhang, Mike Hughes, Paul R. Clarke (Lead / Corresponding author)

Research output: Contribution to journalArticle

125 Citations (Scopus)

Abstract

Ran is an abundant GTPase of the Ras superfamily that is highly conserved in eukaryotes. In interphase cells, Ran is mainly nuclear and thought to be predominantly GTP-bound, but it is also present in the cytoplasm, probably GDP-bound. This asymmetric distribution plays an important role in directing nucleocytoplasmic transport. Ran has also been implicated in cell cycle control, including the transition from mitosis to interphase when the compartmentalisation of the nucleus is established. Here, we have examined the role of Ran in this transition using a cell-free system of Xenopus egg extracts supplemented with sperm heads that provides a model for microtubule aster formation and post-M phase nuclear assembly. Ran-GTP, added as wild-type protein, a mutant defective in GTPase activity (Q69L), or generated by addition of the specific nucleotide exchange factor RCC1, stabilises large microtubule asters nucleated at the sperm centrosome, prevents the redistribution of NuMA from the aster to the nucleus and blocks chromatin decondensation. In contrast, Ran GDP does not stabilise microtubules or inhibit nuclear assembly. RanT24N and RanBP1, which oppose the generation of Ran-GTP by RCC1, arrest nuclear growth after disappearance of the aster. Ran associates with microtubule asters in egg extracts and with mitotic spindles in somatic Xenopus cells, suggesting that it may affect microtubule stability directly. These results show that Ran has a novel function in the control of microtubule stability that is clearly distinct from nucleocytoplasmic transport. The Ran GDP/GTP switch may play a role in co-ordinating changes in the structure of microtubules and the assembly of the nucleus associated with the transition from mitosis to interphase.

Original languageEnglish
Pages (from-to)2453-2461
Number of pages9
JournalJournal of Cell Science
Volume112
Issue number14
Publication statusPublished - 15 Jul 1999

Fingerprint

Xenopus
Guanosine Triphosphate
Microtubules
Ovum
Interphase
Cell Nucleus Active Transport
Mitosis
Sperm Head
ras Proteins
Centrosome
Spindle Apparatus
Cell-Free System
GTP Phosphohydrolases
Mutant Proteins
Cell Cycle Checkpoints
Eukaryota
Cell Division
Chromatin
Spermatozoa
Cytoplasm

Keywords

  • Cell cycle control
  • Centrosome
  • Microtubule
  • NuMA
  • Ran

Cite this

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abstract = "Ran is an abundant GTPase of the Ras superfamily that is highly conserved in eukaryotes. In interphase cells, Ran is mainly nuclear and thought to be predominantly GTP-bound, but it is also present in the cytoplasm, probably GDP-bound. This asymmetric distribution plays an important role in directing nucleocytoplasmic transport. Ran has also been implicated in cell cycle control, including the transition from mitosis to interphase when the compartmentalisation of the nucleus is established. Here, we have examined the role of Ran in this transition using a cell-free system of Xenopus egg extracts supplemented with sperm heads that provides a model for microtubule aster formation and post-M phase nuclear assembly. Ran-GTP, added as wild-type protein, a mutant defective in GTPase activity (Q69L), or generated by addition of the specific nucleotide exchange factor RCC1, stabilises large microtubule asters nucleated at the sperm centrosome, prevents the redistribution of NuMA from the aster to the nucleus and blocks chromatin decondensation. In contrast, Ran GDP does not stabilise microtubules or inhibit nuclear assembly. RanT24N and RanBP1, which oppose the generation of Ran-GTP by RCC1, arrest nuclear growth after disappearance of the aster. Ran associates with microtubule asters in egg extracts and with mitotic spindles in somatic Xenopus cells, suggesting that it may affect microtubule stability directly. These results show that Ran has a novel function in the control of microtubule stability that is clearly distinct from nucleocytoplasmic transport. The Ran GDP/GTP switch may play a role in co-ordinating changes in the structure of microtubules and the assembly of the nucleus associated with the transition from mitosis to interphase.",
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Ran-GTP stabilises microtubule asters and inhibits nuclear assembly in Xenopus egg extracts. / Zhang, Chuanmao; Hughes, Mike; Clarke, Paul R. (Lead / Corresponding author).

In: Journal of Cell Science, Vol. 112, No. 14, 15.07.1999, p. 2453-2461.

Research output: Contribution to journalArticle

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AU - Clarke, Paul R.

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