A non-motor microtubule binding site is essential for the high processivity and mitotic function of kinesin-8 Kif18A

PLoS One. 2011;6(11):e27471. doi: 10.1371/journal.pone.0027471. Epub 2011 Nov 10.

Abstract

Background: Members of the kinesin-8 subfamily are plus end-directed molecular motors that accumulate at the plus-ends of kinetochore-microtubules (kt-MTs) where they regulate MT dynamics. Loss of vertebrate kinesin-8 function induces hyperstable MTs and elongated mitotic spindles accompanied by severe chromosome congression defects. It has been reported that the motility of human kinesin-8, Kif18A, is required for its accumulation at the plus tips of kt-MTs.

Methodology/findings: Here, we investigate how Kif18A localizes to the plus-ends of kt-MTs. We find that Kif18A lacking its C-terminus does not accumulate on the tips of kt-MTs and fails to fulfill its mitotic function. In vitro studies reveal that Kif18A possesses a non-motor MT binding site located within its C-proximal 121 residues. Using single molecule measurements we find that Kif18A is a highly processive motor and, furthermore, that the C-terminal tail is essential for the high processivity of Kif18A.

Conclusion/significance: These results show that Kif18A like its yeast orthologue is a highly processive motor. The ability of Kif18A to walk on MTs for a long distance without dissociating depends on a non-motor MT binding site located at the C-terminus of Kif18A. This C-proximal tail of Kif18A is essential for its plus-end accumulation and mitotic function. These findings advance our understanding of how Kif18A accumulates at the tips of kt-MTs to fulfill its function in mitosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Movement
  • Chromosome Positioning
  • HeLa Cells
  • Humans
  • Immunization
  • Immunoblotting
  • Kinesin / antagonists & inhibitors
  • Kinesin / genetics
  • Kinesin / metabolism*
  • Kinetochores / metabolism*
  • Male
  • Microtubules / metabolism*
  • Mitosis / physiology*
  • Protein Binding
  • RNA, Small Interfering / genetics
  • Rabbits
  • Testis / metabolism

Substances

  • RNA, Small Interfering
  • KIF18A protein, human
  • Kinesin