Motor-independent targeting of CLASPs to kinetochores by CENP-E promotes microtubule turnover and poleward flux.
Efficient chromosome segregation during mitosis relies on the coordinated activity of molecular motors with proteins that regulate kinetochore attachments to dynamic spindle microtubules [1]. CLASPs are conserved kinetochore- and microtubule-associated proteins encoded by two paralog genes, clasp1 and clasp2, and have been previously implicated in the regulation of kinetochore microtubule dynamics [2-4]. However, it remains unknown how CLASPs work in concert with other proteins to form a functional kinetochore microtubule interface. Here we have identified mitotic interactors of human CLASP1 via a proteomic approach. Among these, the microtubule plus-end-directed motor CENP-E [5] was found to form a complex with CLASP1 that colocalizes to multiple structures of the mitotic apparatus in human cells. We found that CENP-E recruits both CLASP1 and CLASP2 to kinetochores independently of its motor activity or the presence of microtubules. Depletion of CLASPs or CENP-E by RNA interference in human cells causes a significant and comparable reduction of kinetochore microtubule poleward flux and turnover rates and rescues spindle bipolarity in Kif2a-depleted cells. We conclude that CENP-E integrates two critical functions that are important for accurate chromosome movement and spindle architecture: one relying directly on its motor activity, and the other involving the targeting of key microtubule regulators to kinetochores.
Maffini
Stefano
S
Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
Maia
Ana R R
AR
Manning
Amity L
AL
Maliga
Zoltan
Z
Pereira
Ana L
AL
Junqueira
Magno
M
Shevchenko
Andrej
A
Hyman
Anthony
A
Yates
John R
JR
Galjart
Niels
N
Compton
Duane A
DA
Maiato
Helder
H
D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D013058:Mass Spectrometry; D008869:Microtubule-Associated Proteins / Q000378:metabolism* / Q000502:physiology; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology
C497850:CLASP1 protein, human; C497851:CLASP2 protein, human; D002868:Chromosomal Proteins, Non-Histone; D008869:Microtubule-Associated Proteins; C068688:centromere protein E