title: Kinesin-12 differentially affects spindle assembly depending on its microtubule substrate.
abstract: BACKGROUND
  During mitosis, the microtubule (MT) cytoskeleton rearranges into a bipolar spindle that drives chromosome segregation. Two kinesin subtypes, kinesin-5 and kinesin-12, help build this bipolar array by separating the spindle poles. However, unlike kinesin-5, the kinesin-12 mechanism is not well understood.
  
  
  RESULTS
  At physiologically normal protein levels, we demonstrate that the human kinesin-12 Kif15 acts predominantly on kinetochore fibers to regulate their lengths. This activity limits the extent to which spindle poles separate, leading to transient spindle length instabilities when the motor is absent. Using a novel cell line wherein Kif15 usurps kinesin-5 function, we further show that Kif15 can assume a commanding role in spindle pole separation as a consequence of its mislocalization to nonkinetochore MTs. This Kif15-dependent mechanism is inefficient, however, as spindles assemble through a perilous monopolar intermediate.
  
  
  CONCLUSIONS
  By examining Kif15 activity in two cellular contexts, we found that Kif15 bound to kinetochore fibers antagonizes centrosome separation while Kif15 bound to nonkinetochore MTs mediates centrosome separation. Our work demonstrates that Kif15 acts on parallel MT arrays and clarifies its role under both normal and pathological conditions.
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
authors.forename: Emma G
authors.initials: EG
authors.lastname: Sturgill
authors.forename: Ryoma
authors.initials: R
authors.lastname: Ohi
mesh_terms: D002453:Cell Cycle; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D016547:Kinesins / Q000235:genetics* / Q000378:metabolism; D018386:Kinetochores / Q000378:metabolism* / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008938:Mitosis; D008941:Spindle Apparatus / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: C470243:KIF11 protein, human; C486567:KIF15 protein, human; D016547:Kinesins