Abstract：

Mitotic chromosome segregation is orchestrated by the dynamic interaction of spindle microtubules with the kinetochore. During chromosome alignment, bi-oriented kinetochores move chromosomes by regulating the plus-end dynamics of the attached microtubules. Although previous studies show that mitotic kinesin CENP-E forms a link between attachment of spindle microtubule to the kinetochore and the mitotic checkpoint signaling cascade, the molecular mechanism underlying dynamic kinetochore-microtubule interactions in mammalian cells remains elusive. Here we identify a novel interaction between CENP-E and SKAP which functions synergistically in governing dynamic kinetochore-microtubule interactions. SKAP binds to the C-terminal tail of CENP-E in vitro and is essential for an accurate kinetochore-microtubule attachment in vivo. Immuno-electron microscopic analysis indicates that SKAP is a constituent of the kinetochore corona fibers of mammalian centromeres. Depletion of SKAP or CENP-E by RNA interference results in a dramatic reduction of inter-kinetochore tension, which causes chromosome mis-segregation with a prolonged delay in achieving metaphase alignment. Importantly, SKAP binds to microtubules in vitro, and this interaction is synergized by CENP-E. Based on these findings, we propose that SKAP cooperates with CENP-E to orchestrate dynamic kinetochore-microtubule interaction for faithful chromosome segregation.