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Minus-end-directed Kinesin-14 motors align antiparallel microtubules to control metaphase spindle length

Austin J Hepperla1, Patrick T Willey1, Courtney E Coombes1

  • 1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA.

Developmental Cell
|October 15, 2014
PubMed

Insights

Budding yeast kinesin-14 motors (Kar3-Cik1) align spindle microtubules, enabling kinesin-5 motors to properly control mitotic spindle length and bipolarity during cell division.

Area of Science:

  • Cell Biology
  • Molecular Motors
  • Cytoskeleton Dynamics

Background:

  • The mitotic spindle, a microtubule structure, is essential for accurate chromosome segregation during cell division.
  • Metaphase mitotic spindle length control is crucial and traditionally attributed to a balance between opposing motor forces.
  • A paradox exists where inhibiting kinesin-14 motors, which pull poles together, often results in shorter spindles.

Purpose of the Study:

  • To elucidate the mechanistic explanation for the paradox of shorter metaphase mitotic spindles when kinesin-14 motors are inactive.
  • To investigate the role of the budding yeast kinesin-14 motor Kar3-Cik1 in spindle assembly and length regulation.

Main Methods:

  • Computational modeling
  • In vitro reconstitution assays
  • Live-cell fluorescence microscopy
  • Electron microscopy

Main Results:

  • The kinesin-14 motor complex Kar3-Cik1 efficiently aligns spindle microtubules along the spindle axis.
  • This alignment facilitates the action of kinesin-5 motors, which generate outward microtubule sliding forces.
  • Proper functioning of Kar3-Cik1 is thus critical for achieving correct spindle bipolarity and length.

Conclusions:

  • The kinesin-14 motor Kar3-Cik1 plays a key role in organizing spindle microtubules, resolving the paradox of spindle length control.
  • Efficient spindle microtubule alignment by kinesin-14 is a prerequisite for effective function of kinesin-5 motors in establishing spindle bipolarity.

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