title: Microtubule binding by KNL-1 contributes to spindle checkpoint silencing at the kinetochore.
abstract: Accurate chromosome segregation requires coordination between microtubule attachment and spindle checkpoint signaling at the kinetochore. The kinetochore-localized KMN (KNL-1/Mis12 complex/Ndc80 complex) network, which mediates microtubule attachment and scaffolds checkpoint signaling, harbors two distinct microtubule-binding activities: the load-bearing activity of the Ndc80 complex and a less well-understood activity in KNL-1. In this paper, we show that KNL-1 microtubule-binding and -bundling activity resides in its extreme N terminus. Selective perturbation of KNL-1 microtubule binding in Caenorhabditis elegans embryos revealed that this activity is dispensable for both load-bearing attachment formation and checkpoint activation but plays a role in checkpoint silencing at the kinetochore. Perturbation of both microtubule binding and protein phosphatase 1 docking at the KNL-1 N terminus additively affected checkpoint silencing, indicating that, despite their proximity in KNL-1, these two activities make independent contributions. We propose that microtubule binding by KNL-1 functions in checkpoint silencing by sensing microtubules attached to kinetochores and relaying their presence to eliminate generation of the checkpoint signal.
authors.affiliation: Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92037, USA.
authors.forename: Julien
authors.initials: J
authors.lastname: Espeut
authors.forename: Dhanya K
authors.initials: DK
authors.lastname: Cheerambathur
authors.forename: Lenno
authors.initials: L
authors.lastname: Krenning
authors.forename: Karen
authors.initials: K
authors.lastname: Oegema
authors.forename: Arshad
authors.initials: A
authors.lastname: Desai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D059447:Cell Cycle Checkpoints; D020090:Chromosome Segregation; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D018386:Kinetochores / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D008941:Spindle Apparatus / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; C478660:KNL-1 protein, C elegans; D008869:Microtubule-Associated Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins