The Ndc80 internal loop is required for recruitment of the Ska complex to establish end-on microtubule attachment to kinetochores.

• DOI: 10.1242/jcs.104208
• Publication Date: 2012-03-28T01:33:28Z
• Authors: Gang Zhang; Christian D. Kels...; Xiao-Wen Hu; Mathilde J Kaas H...; Martin R. Singleton; Jesper V. Olsen; Jakob Nilsson
• Keywords: 0301 basic medicine; Molecular Sequence Data; Fluorescent Antibody Technique; Nuclear Proteins; Microtubules; Mass Spectrometry; Cytoskeletal Proteins; Protein Transport; 03 medical and health sciences; Sequence Analysis, Protein; Chromosome Segregation; Multiprotein Complexes; Protein Interaction Mapping; Chromosomes, Human; Humans; RNA Interference; Amino Acid Sequence; Cloning, Molecular; Kinetochores; Metaphase; Protein Binding

The Ndc80 complex establishes end-on attachment of kinetochores to microtubules essential for chromosome segregation. The Ndc80 subunit is characterized by an N-terminal region, that binds directly to microtubules, and a long coiled-coil region that interacts with Nuf2. A loop region in Ndc80 that generates a kink in the structure disrupts the long coiled-coil region but the exact function of this loop is not clear. Here we show that this loop region is essential for end-on attachment of kinetochores to microtubules in human cells. Cells expressing loop mutants of Ndc80 are unable to align the chromosomes and stable kinetochore fibers are absent. Through quantitative mass spectrometry and immunofluorescence we find that the binding of the Ska complex depends on the loop region explaining why end-on attachment is defective. This underscores the importance of the Ndc80 loop region in coordinating chromosome segregation through the recruitment of specific proteins to the kinetochore.