Motor-independent targeting of CLASPs to kinetochores by CENP-E promotes microtubule turnover and poleward flux

Curr Biol. 2009 Sep 29;19(18):1566-72. doi: 10.1016/j.cub.2009.07.059. Epub 2009 Sep 3.

Abstract

Efficient chromosome segregation during mitosis relies on the coordinated activity of molecular motors with proteins that regulate kinetochore attachments to dynamic spindle microtubules [1]. CLASPs are conserved kinetochore- and microtubule-associated proteins encoded by two paralog genes, clasp1 and clasp2, and have been previously implicated in the regulation of kinetochore microtubule dynamics [2-4]. However, it remains unknown how CLASPs work in concert with other proteins to form a functional kinetochore microtubule interface. Here we have identified mitotic interactors of human CLASP1 via a proteomic approach. Among these, the microtubule plus-end-directed motor CENP-E [5] was found to form a complex with CLASP1 that colocalizes to multiple structures of the mitotic apparatus in human cells. We found that CENP-E recruits both CLASP1 and CLASP2 to kinetochores independently of its motor activity or the presence of microtubules. Depletion of CLASPs or CENP-E by RNA interference in human cells causes a significant and comparable reduction of kinetochore microtubule poleward flux and turnover rates and rescues spindle bipolarity in Kif2a-depleted cells. We conclude that CENP-E integrates two critical functions that are important for accurate chromosome movement and spindle architecture: one relying directly on its motor activity, and the other involving the targeting of key microtubule regulators to kinetochores.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosomal Proteins, Non-Histone / metabolism
  • Chromosomal Proteins, Non-Histone / physiology*
  • HeLa Cells
  • Humans
  • Kinetochores / metabolism*
  • Mass Spectrometry
  • Microtubule-Associated Proteins / metabolism*
  • Microtubule-Associated Proteins / physiology
  • Microtubules / metabolism*
  • Mitosis / physiology

Substances

  • CLASP1 protein, human
  • CLASP2 protein, human
  • Chromosomal Proteins, Non-Histone
  • Microtubule-Associated Proteins
  • centromere protein E