Architecture of the Human Ndc80-Hec1 Complex, a Critical Constituent of the Outer Kinetochore*
Journal - Journal of Biological Chemistry
The Ndc80 complex is a constituent of the outer plate of thekinetochore and plays a critical role in establishing the stablekinetochore-microtubule interactions required for chromosomesegregation in mitosis. The Ndc80 complex is evolutionarilyconserved and contains the four subunits Spc24, Spc25, Nuf2,and Ndc80 (whose human homologue is called Hec1). All four subunitsare predicted to contain globular domains and extensive coiledcoil regions. To gain an insight into the organization of thehuman Ndc80 complex, we reconstituted it using recombinant methods.The hydrodynamic properties of the recombinant Ndc80 complexare identical to those of the endogenous HeLa cell complex andare consistent with a 1:1:1:1 stoichiometry of the four subunitsand a very elongated shape. Two tight Hec1-Nuf2 and Spc24-Spc25subcomplexes, each stabilized by a parallel heterodimeric coiledcoil, maintain this organization. These subcomplexes tetramerizevia an interaction of the C- and N-terminal portions of theHec1-Nuf2 and Spc24-Spc25 coiled coils, respectively. The recombinantcomplex displays normal kinetochore localization upon injectionin HeLa cells and is therefore a faithful copy of the endogenousNdc80 complex.* This work was supported by grants from the Italian Associationfor Cancer Research (AIRC), the Italian Ministry of Health,and the Human Frontier Science Program. The costs of publicationof this article were defrayed in part by the payment of pagecharges. This article must therefore be hereby marked "advertisement"in accordance with 18 U.S.C. Section 1734 solely to indicatethis fact.