A model for the proposed roles of different microtubule-based motor proteins in establishing spindle bipolarity

Claire E. Walczak, Isabelle Vernos, Timothy J. Mitchison, Eric Karsenti, Rebecca Heald

Research output: Contribution to journalArticle

303 Scopus citations

Abstract

Background: In eukaryotes, assembly of the mitotic spindle requires the interaction of chromosomes with microtubules. During this process, several motor proteins that move along microtubules promote formation of a bipolar microtubule array, but the precise mechanism is unclear. In order to examine the roles of different motor proteins in building a bipolar spindle, we have used a simplified system in which spindles assemble around beads coated with plasmid DNA and incubated in extracts from Xenopus eggs. Using this system, we can study spindle assembly in the absence of paired cues, such as centrosomes and kinetochores, whose microtubule-organizing properties might mask the action of motor proteins. Results: We blocked the function of individual motor proteins in the Xenopus extracts using specific antibodies. Inhibition of Xenopus kinesin-like protein 1 (Xklp1) led either to the dissociation of chromatin beads from microtubule arrays, or to collapsed microtubule bundles on beads. Inhibition of Eg5 resulted in monopolar microtubule arrays emanating from chromatin beads. Addition of antibodies against dynein inhibited the focusing of microtubule ends into spindle poles in a dose-dependent manner. Inhibition of Xenopus carboxyterminal kinesin 2 (XCTK2) affected both pole formation and spindle stability. Co-inhibition of XCTK2 and dynein dramatically increased the severity of spindle pole defects. Inhibition of Xklp2 caused only minor spindle pole defects. Conclusions: Multiple microtubule-based motor activities are required for the bipolar organization of microtubules around chromatin beads, and we propose a model for the roles of the individual motor proteins in this process.

Original languageEnglish (US)
Pages (from-to)903-913
Number of pages11
JournalCurrent Biology
Volume8
Issue number16
DOIs
StatePublished - Jul 30 1998
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Fingerprint Dive into the research topics of 'A model for the proposed roles of different microtubule-based motor proteins in establishing spindle bipolarity'. Together they form a unique fingerprint.

  • Cite this