The conserved KMN network constitutes the core microtubule-binding site of the kinetochore.
The microtubule-binding interface of the kinetochore is of central importance in chromosome segregation. Although kinetochore components that stabilize, translocate on, and affect the polymerization state of microtubules have been identified, none have proven essential for kinetochore-microtubule interactions. Here, we examined the conserved KNL-1/Mis12 complex/Ndc80 complex (KMN) network, which is essential for kinetochore-microtubule interactions in vivo. We identified two distinct microtubule-binding activities within the KMN network: one associated with the Ndc80/Nuf2 subunits of the Ndc80 complex, and a second in KNL-1. Formation of the complete KMN network, which additionally requires the Mis12 complex and the Spc24/Spc25 subunits of the Ndc80 complex, synergistically enhances microtubule-binding activity. Phosphorylation by Aurora B, which corrects improper kinetochore-microtubule connections in vivo, reduces the affinity of the Ndc80 complex for microtubules in vitro. Based on these findings, we propose that the conserved KMN network constitutes the core microtubule-binding site of the kinetochore.
Cheeseman
Iain M
IM
Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine (UCSD), CMM-East, Room 3052, La Jolla, CA 92093, USA. icheeseman@ucsd.edu
Chappie
Joshua S
JS
Wilson-Kubalek
Elizabeth M
EM
Desai
Arshad
A
D000595:Amino Acid Sequence; D000818:Animals; D064107:Aurora Kinase B; D064127:Aurora Kinases; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D003598:Cytoskeletal Proteins; D004926:Escherichia coli; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000737:chemistry; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary
D029742:Caenorhabditis elegans Proteins; D003598:Cytoskeletal Proteins; C478660:KNL-1 protein, C elegans; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; C492665:NDC-80 protein, C elegans; C120529:NDC80 protein, human; D009687:Nuclear Proteins; C576921:AURKB protein, human; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases