title: Accurate phosphoregulation of kinetochore-microtubule affinity requires unconstrained molecular interactions.
abstract: Accurate chromosome segregation relies on dynamic interactions between microtubules (MTs) and the NDC80 complex, a major kinetochore MT-binding component. Phosphorylation at multiple residues of its Hec1 subunit may tune kinetochore-MT binding affinity for diverse mitotic functions, but molecular details of such phosphoregulation remain elusive. Using quantitative analyses of mitotic progression in mammalian cells, we show that Hec1 phosphorylation provides graded control of kinetochore-MT affinity. In contrast, modeling the kinetochore interface with repetitive MT binding sites predicts a switchlike response. To reconcile these findings, we hypothesize that interactions between NDC80 complexes and MTs are not constrained, i.e., the NDC80 complexes can alternate their binding between adjacent kinetochore MTs. Experiments using cells with phosphomimetic Hec1 mutants corroborate predictions of such a model but not of the repetitive sites model. We propose that accurate regulation of kinetochore-MT affinity is driven by incremental phosphorylation of an NDC80 molecular "lawn," in which the NDC80-MT bonds reorganize dynamically in response to the number and stability of MT attachments.
authors: Physiology Department, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
authors: Anatoly V
authors: AV
authors: Zaytsev
authors: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523.
authors: Lynsie J R
authors: LJ
authors: Sundin
authors: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523.
authors: Keith F
authors: KF
authors: DeLuca
authors: Physiology Department, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 jdeluca@colostate.edu gekate@mail.med.upenn.edu.
authors: Ekaterina L
authors: EL
authors: Grishchuk
authors: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523 jdeluca@colostate.edu gekate@mail.med.upenn.edu.
authors: Jennifer G
authors: JG
authors: DeLuca
mesh_terms: D000818:Animals; D001665:Binding Sites; D020090:Chromosome Segregation; D002877:Chromosomes, Human / Q000378:metabolism; D003598:Cytoskeletal Proteins; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008677:Metaphase; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008958:Models, Molecular; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D048328:Potoroidae; D011485:Protein Binding; D011499:Protein Processing, Post-Translational
chemical_list: D003598:Cytoskeletal Proteins; D008869:Microtubule-Associated Proteins; C120529:NDC80 protein, human; D009687:Nuclear Proteins