The expanded Kinesin-13 repertoire of trypanosomes contains only one mitotic Kinesin indicating multiple extra-nuclear roles

PLoS One. 2010 Nov 23;5(11):e15020. doi: 10.1371/journal.pone.0015020.

Abstract

Background: Kinesin-13 proteins have a critical role in animal cell mitosis, during which they regulate spindle microtubule dynamics through their depolymerisation activity. Much of what is known about Kinesin-13 function emanates from a relatively small sub-family of proteins containing MCAK and Kif2A/B. However, recent work on kinesins from the much more widely distributed, ancestral Kinesin-13 family, which includes human Kif24, have identified a second function in flagellum length regulation that may exist either alongside or instead of the mitotic role.

Methodology/principal findings: The African trypanosome Trypanosoma brucei encodes 7 distinct Kinesin-13 proteins, allowing scope for extensive specialisation of roles. Here, we show that of all the trypanosomal Kinesin-13 proteins, only one is nuclear. This protein, TbKIN13-1, is present in the nucleoplasm throughout the cell cycle, but associates with the spindle during mitosis, which in trypanosomes is closed. TbKIN13-1 is necessary for the segregation of both large and mini-chromosomes in this organism and reduction in TbKIN13-1 levels mediated by RNA interference causes deflects in spindle disassembly with spindle-like structures persisting in non-mitotic cells. A second Kinesin-13 is localised to the flagellum tip, but the majority of the Kinesin-13 family members are in neither of these cellular locations.

Conclusions/significance: These data show that the expanded Kinesin-13 repertoire of trypanosomes is not associated with diversification of spindle-associated roles. TbKIN13-1 is required for correct spindle function, but the extra-nuclear localisation of the remaining paralogues suggests that the biological roles of the Kinesin-13 family is wider than previously thought.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Nucleus / metabolism*
  • Chromosome Segregation
  • Flagella / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Immunoblotting
  • In Situ Hybridization, Fluorescence
  • Kinesin / classification
  • Kinesin / genetics
  • Kinesin / metabolism*
  • Microscopy, Fluorescence / methods
  • Mitosis
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Phylogeny
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • RNA Interference
  • Spindle Apparatus / metabolism
  • Trypanosoma brucei brucei / genetics
  • Trypanosoma brucei brucei / metabolism*

Substances

  • Nuclear Proteins
  • Protein Isoforms
  • Protozoan Proteins
  • Green Fluorescent Proteins
  • Kinesin