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


RESULTS
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
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.
Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom. bill.wickstead@path.ox.ac.uk
Bill
B
Wickstead
Jamie T
JT
Carrington
Eva
E
Gluenz
Keith
K
Gull
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D020090:Chromosome Segregation; D005407:Flagella / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D017404:In Situ Hybridization, Fluorescence; D016547:Kinesins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence / Q000379:methods; D008938:Mitosis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D008941:Spindle Apparatus / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*
D009687:Nuclear Proteins; D020033:Protein Isoforms; D015800:Protozoan Proteins; D049452:Green Fluorescent Proteins; D016547:Kinesins