Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
The importin alpha-regulated microtubule-associated protein TPX2 is known to be critical for meiotic and mitotic spindle formation in vertebrates, but its detailed mechanism of action and regulation is not understood. Here, the site of interaction on TPX2 for importin alpha is mapped. A TPX2 mutant that cannot bind importin alpha is constitutively active in the induction of microtubule-containing aster-like structures in Xenopus egg extract, demonstrating that no other importin alpha or RanGTPase target is required to mediate microtubule assembly in this system. Further, recombinant TPX2 is shown to induce the formation and bundling of microtubules in dilute solutions of pure tubulin. In this purified system, importin alpha prevents TPX2-induced microtubule formation, but not TPX2-tubulin interaction or microtubule bundling. This demonstrates that TPX2 has more than one mode of interaction with tubulin and that only one of these types of interaction is abolished by importin alpha. The data suggest that the critical early function in spindle formation regulated by importin alpha is TPX2-mediated microtubule nucleation.
Askjaer,
Ran GTPase cycle and importins alpha and beta are essential for spindle formation and nuclear envelope assembly in living Caenorhabditis elegans embryos.
2002, Pubmed
Askjaer,
Ran GTPase cycle and importins alpha and beta are essential for spindle formation and nuclear envelope assembly in living Caenorhabditis elegans embryos.
2002,
Pubmed Bamba,
The GTPase Ran regulates chromosome positioning and nuclear envelope assembly in vivo.
2002,
Pubmed
,
Xenbase Bischoff,
RanGAP1 induces GTPase activity of nuclear Ras-related Ran.
1994,
Pubmed Carazo-Salas,
Ran-GTP coordinates regulation of microtubule nucleation and dynamics during mitotic-spindle assembly.
2001,
Pubmed
,
Xenbase Carazo-Salas,
Generation of GTP-bound Ran by RCC1 is required for chromatin-induced mitotic spindle formation.
1999,
Pubmed
,
Xenbase Cassimeris,
Regulation of microtubule-associated proteins.
2001,
Pubmed Clarke,
Ran GTPase: a master regulator of nuclear structure and function during the eukaryotic cell division cycle?
2001,
Pubmed Compton,
Spindle assembly in animal cells.
2000,
Pubmed Dasso,
The Ran GTPase: theme and variations.
2002,
Pubmed Giet,
The non-catalytic domain of the Xenopus laevis auroraA kinase localises the protein to the centrosome.
2001,
Pubmed
,
Xenbase Görlich,
Isolation of a protein that is essential for the first step of nuclear protein import.
1994,
Pubmed
,
Xenbase Gruss,
Ran induces spindle assembly by reversing the inhibitory effect of importin alpha on TPX2 activity.
2001,
Pubmed
,
Xenbase Gruss,
Chromosome-induced microtubule assembly mediated by TPX2 is required for spindle formation in HeLa cells.
2002,
Pubmed
,
Xenbase Heidebrecht,
p100: a novel proliferation-associated nuclear protein specifically restricted to cell cycle phases S, G2, and M.
1997,
Pubmed Hetzer,
The Ran GTPase as a marker of chromosome position in spindle formation and nuclear envelope assembly.
2002,
Pubmed Hyman,
Preparation of modified tubulins.
1991,
Pubmed Kalab,
The ran GTPase regulates mitotic spindle assembly.
1999,
Pubmed
,
Xenbase Karsenti,
The mitotic spindle: a self-made machine.
2001,
Pubmed
,
Xenbase Laemmli,
Cleavage of structural proteins during the assembly of the head of bacteriophage T4.
1970,
Pubmed Mitchison,
Microtubule assembly nucleated by isolated centrosomes.
,
Pubmed Moritz,
Gamma-tubulin complexes and microtubule nucleation.
2001,
Pubmed Nachury,
Importin beta is a mitotic target of the small GTPase Ran in spindle assembly.
2001,
Pubmed
,
Xenbase Nakai,
PSORT: a program for detecting sorting signals in proteins and predicting their subcellular localization.
1999,
Pubmed Ohba,
Self-organization of microtubule asters induced in Xenopus egg extracts by GTP-bound Ran.
1999,
Pubmed
,
Xenbase Popov,
XMAP215 is required for the microtubule-nucleating activity of centrosomes.
2002,
Pubmed
,
Xenbase Sawin,
Mitotic spindle assembly by two different pathways in vitro.
1991,
Pubmed
,
Xenbase Schiebel,
gamma-tubulin complexes: binding to the centrosome, regulation and microtubule nucleation.
2000,
Pubmed Tournebize,
Control of microtubule dynamics by the antagonistic activities of XMAP215 and XKCM1 in Xenopus egg extracts.
2000,
Pubmed
,
Xenbase Vasquez,
Phosphorylation by CDK1 regulates XMAP215 function in vitro.
1999,
Pubmed
,
Xenbase Weis,
Characterization of the nuclear protein import mechanism using Ran mutants with altered nucleotide binding specificities.
1996,
Pubmed Wiese,
Role of importin-beta in coupling Ran to downstream targets in microtubule assembly.
2001,
Pubmed
,
Xenbase Wilde,
Stimulation of microtubule aster formation and spindle assembly by the small GTPase Ran.
1999,
Pubmed
,
Xenbase Wilde,
Ran stimulates spindle assembly by altering microtubule dynamics and the balance of motor activities.
2001,
Pubmed
,
Xenbase Wittmann,
Localization of the kinesin-like protein Xklp2 to spindle poles requires a leucine zipper, a microtubule-associated protein, and dynein.
1998,
Pubmed
,
Xenbase Wittmann,
TPX2, A novel xenopus MAP involved in spindle pole organization.
2000,
Pubmed
,
Xenbase Wittmann,
The spindle: a dynamic assembly of microtubules and motors.
2001,
Pubmed Zhang,
Ran-GTP stabilises microtubule asters and inhibits nuclear assembly in Xenopus egg extracts.
1999,
Pubmed
,
Xenbase
