The Ndc80/HEC1 complex is a contact point for kinetochore-microtubule attachment

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Kinetochores are multicomponent assemblies that connect chromosomal centromeres to mitotic-spindle microtubules. The Ndc80 complex is an essential core element of kinetochores, conserved from yeast to humans. It is a rod-like assembly of four proteins— Ndc80p (HEC1 in humans), Nuf2p, Spc24p and Spc25p. We describe here the crystal structure of the most conserved region of HEC1, which lies at one end of the rod and near the N terminus of the polypeptide chain. It folds into a calponin-homology domain, resembling the microtubule-binding domain of the plus-end-associated protein EB1. We show that an Ndc80p-Nuf2p heterodimer binds microtubules in vitro. The less conserved, N-terminal segment of Ndc80p contributes to the interaction and may be a crucial regulatory element. We propose that the Ndc80 complex forms a direct link between kinetochore core components and spindle microtubules.

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Figure 1: Structure of the HEC1 globular domain, compared with the EB1 microtubule-binding domain.
Figure 2: Surface properties of HEC1_CH.
Figure 3: Microtubule binding by 2NG and 2NGΔN.

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The authors thank J.J. Miranda for help with the microtubule cosedimentation assay, D. Panne for assistance with X-ray data collection and E. Salmon, J. Deluca, N. Larsen, P.R. Ohi and V. Draviam for critique of the manuscript. We acknowledge the Advanced Light Source at Lawrence Berkeley National Laboratory. J.A.-B. is a recipient of the American Cancer Society postdoctoral fellowship. S.C.H. is an investigator of the Howard Hughes Medical Institute.

Author information

R.R.W. contributed to the design and execution of the structure determination of HEC1_CH, the microtubule cosedimentation experiments and manuscript preparation. J.A.-B. and R.R.W. contributed the negative-stain electron microscopy. S.C.H. guided the project and helped prepare the manuscript.

Correspondence to Stephen C Harrison.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Fig. 1

Comparison of relative microtubule-binding affinity of Ndc80 and EB1. (PDF 68 kb)

Supplementary Fig. 2

Ndc80p N-terminal segment alone does not bind to microtubules. (PDF 11 kb)

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