Suppressor Analysis Uncovers That MAPs and Microtubule Dynamics Balance with the Cut7/Kinesin-5 Motor for Mitotic Spindle Assembly in Schizosaccharomyces pombe

G3 (Bethesda). 2019 Jan 9;9(1):269-280. doi: 10.1534/g3.118.200896.


The Kinesin-5 motor Cut7 in Schizosaccharomyces pombe plays essential roles in spindle pole separation, leading to the assembly of bipolar spindle. In many organisms, simultaneous inactivation of Kinesin-14s neutralizes Kinesin-5 deficiency. To uncover the molecular network that counteracts Kinesin-5, we have conducted a genetic screening for suppressors that rescue the cut7-22 temperature sensitive mutation, and identified 10 loci. Next generation sequencing analysis reveals that causative mutations are mapped in genes encoding α-, β-tubulins and the microtubule plus-end tracking protein Mal3/EB1, in addition to the components of the Pkl1/Kinesin-14 complex. Moreover, the deletion of various genes required for microtubule nucleation/polymerization also suppresses the cut7 mutant. Intriguingly, Klp2/Kinesin-14 levels on the spindles are significantly increased in cut7 mutants, whereas these increases are negated by suppressors, which may explain the suppression by these mutations/deletions. Consistent with this notion, mild overproduction of Klp2 in these double mutant cells confers temperature sensitivity. Surprisingly, treatment with a microtubule-destabilizing drug not only suppresses cut7 temperature sensitivity but also rescues the lethality resulting from the deletion of cut7, though a single klp2 deletion per se cannot compensate for the loss of Cut7. We propose that microtubule assembly and/or dynamics antagonize Cut7 functions, and that the orchestration between these two factors is crucial for bipolar spindle assembly.

Keywords: fission yeast; kinesin; microtubule dynamics; mitotic spindle; suppressor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosome Segregation / genetics
  • Kinesins / genetics*
  • M Phase Cell Cycle Checkpoints / genetics
  • Microtubule-Associated Proteins / genetics*
  • Microtubules / genetics
  • Mitosis / genetics
  • Mutation
  • Schizosaccharomyces / genetics*
  • Schizosaccharomyces / growth & development
  • Schizosaccharomyces pombe Proteins / genetics*
  • Spindle Apparatus / genetics*
  • Tubulin / genetics


  • Cut7 protein, S pombe
  • Klp2 protein, S pombe
  • Mal3 protein, S pombe
  • Microtubule-Associated Proteins
  • PKL1 protein, S pombe
  • Schizosaccharomyces pombe Proteins
  • Tubulin
  • Kinesins

Associated data

  • figshare/10.25387/g3.7351985