title: A molecular basis for the differential roles of Bub1 and BubR1 in the spindle assembly checkpoint.
abstract: The spindle assembly checkpoint (SAC) monitors and promotes kinetochore-microtubule attachment during mitosis. Bub1 and BubR1, SAC components, originated from duplication of an ancestor gene. Subsequent sub-functionalization established subordination: Bub1, recruited first to kinetochores, promotes successive BubR1 recruitment. Because both Bub1 and BubR1 hetero-dimerize with Bub3, a targeting adaptor for phosphorylated kinetochores, the molecular basis for such sub-functionalization is unclear. We demonstrate that Bub1, but not BubR1, enhances binding of Bub3 to phosphorylated kinetochores. Grafting a short motif of Bub1 onto BubR1 promotes Bub1-independent kinetochore recruitment of BubR1. This gain-of-function BubR1 mutant cannot sustain a functional checkpoint. We demonstrate that kinetochore localization of BubR1 relies on direct hetero-dimerization with Bub1 at a pseudo-symmetric interface. This pseudo-symmetric interaction underpins a template-copy relationship crucial for kinetochore-microtubule attachment and SAC signaling. Our results illustrate how gene duplication and sub-functionalization shape the workings of an essential molecular network.
authors.affiliation: Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Overlack
authors.affiliation: Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Ivana
authors.initials: I
authors.lastname: Primorac
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht, Netherlands.
authors.forename: Mathijs
authors.initials: M
authors.lastname: Vleugel
authors.affiliation: Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Veronica
authors.initials: V
authors.lastname: Krenn
authors.affiliation: Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Stefano
authors.initials: S
authors.lastname: Maffini
authors.affiliation: Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Hoffmann
authors.affiliation: Department of Molecular Cancer Research, University Medical Center Utrecht, Utrecht, Netherlands.
authors.forename: Geert J P L
authors.initials: GJ
authors.lastname: Kops
authors.affiliation: Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Musacchio
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D050505:Mutant Proteins; D011505:Protein-Tyrosine Kinases; C584277:BUB1 protein, human; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human
keywords: biochemistry; cell biology; cell cycle; cell division; centromere; human; kinetochore; spindle assembly checkpoint