The human kinesin Kif18A is a motile microtubule depolymerase essential for chromosome congression.
BACKGROUND
The accurate alignment of chromosomes at the spindle equator is fundamental for the equal distribution of the genome in mitosis and thus for the genetic integrity of eukaryotes. Although it is well established that chromosome movements are coupled to microtubule dynamics, the underlying mechanism is not well understood.


RESULTS
By combining RNAi-depletion experiments with in vitro biochemical assays, we demonstrate that the human kinesin Kif18A is a motile microtubule depolymerase essential for chromosome congression in mammalian tissue culture cells. We show that in vitro Kif18A is a slow plus-end-directed kinesin that possesses microtubule depolymerizing activity. Notably, Kif18A like its yeast ortholog Kip3p depolymerizes longer microtubules more quickly than shorter ones. In vivo, Kif18A accumulates in mitosis where it localizes close to the plus ends of kinetochore microtubules. The depletion of Kif18A induces aberrantly long mitotic spindles and loss of tension across sister kinetochores, resulting in the activation of the Mad2-dependent spindle-assembly checkpoint. Live-cell microscopy studies revealed that in Kif18A-depleted cells, chromosomes move at reduced speed and completely fail to align at the spindle equator.


CONCLUSIONS
These studies identify Kif18A as a dual-functional kinesin and a key component of chromosome congression in mammalian cells.
Mayr
Monika I
MI
Chemical Genetics, Independent Research Group, Department of Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Hümmer
Stefan
S
Bormann
Jenny
J
Grüner
Tamara
T
Adio
Sarah
S
Woehlke
Guenther
G
Mayer
Thomas U
TU
D002135:Calcium-Binding Proteins / Q000502:physiology; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000502:physiology; D002877:Chromosomes, Human / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016547:Kinesins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D018386:Kinetochores / Q000378:metabolism; D064246:Mad2 Proteins; D008870:Microtubules / Q000378:metabolism*; D034622:RNA Interference; D012097:Repressor Proteins / Q000502:physiology
D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D012097:Repressor Proteins; C502735:KIF18A protein, human; D016547:Kinesins