1. ¹Laboratory of Cell Dynamics, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China E-mail: yaoxb@ustc.edu.cn
2. ²Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
3. ³Electron Microscopy Facility, Morhouse School of Medicine, Atlanta, GA 30310, USA

Correspondence: Xue Biao YAO, PhD, Laboratory of Cell Dynamics, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China Tel: (551) 360-7141, Fax: (551) 360-7141, E-mail: yaoxb@ustc.edu.cn

^*These two authors contributed equally to this work

Received 1 July 2003; Revised 11 August 2003; Accepted 13 September 2003.

Abstract

Entry into mitosis is driven by signaling cascades of mitotic kinases. Our recent studies show that TTK, a kinetochore-associated protein kinase, interacts with CENP-E, a mitotic kinesin located to corona fiber of kinetochore. Using immunoelectron microscopy, here we show that TTK is present at the nuclear pore adjacent complex of interphase HeLa cells. Upon nuclear envelope fragmentation, TTK targets to the outermost region of the developing kinetochores of monoorient chromosome as well as to spindle poles. After stable attachment, throughout chromosome congression, TTK is a constituent of the corona fibers, extending up to 90 nm away from the kinetochore outer plate. Upon metaphase alignment, TTK departs from the kinetochore and migrates toward the centrosomes. Taken together, this evidence strongly supports a model in which TTK functions in spindle checkpoint signaling cascades at both kinetochore and centrosome.