title: PP2A-B56 opposes Mps1 phosphorylation of Knl1 and thereby promotes spindle assembly checkpoint silencing.
abstract: The spindle assembly checkpoint (SAC) monitors correct attachment of chromosomes to microtubules, an important safeguard mechanism ensuring faithful chromosome segregation in eukaryotic cells. How the SAC signal is turned off once all the chromosomes have successfully attached to the spindle remains an unresolved question. Mps1 phosphorylation of Knl1 results in recruitment of the SAC proteins Bub1, Bub3, and BubR1 to the kinetochore and production of the wait-anaphase signal. SAC silencing is therefore expected to involve a phosphatase opposing Mps1. Here we demonstrate in vivo and in vitro that BubR1-associated PP2A-B56 is a key phosphatase for the removal of the Mps1-mediated Knl1 phosphorylations necessary for Bub1/BubR1 recruitment in mammalian cells. SAC silencing is thus promoted by a negative feedback loop involving the Mps1-dependent recruitment of a phosphatase opposing Mps1. Our findings extend the previously reported role for BubR1-associated PP2A-B56 in opposing Aurora B and suggest that BubR1-bound PP2A-B56 integrates kinetochore surveillance and silencing of the SAC.
authors.affiliation: Sir William Dunn School of Pathology and Department of Biochemistry, University of Oxford, Oxford OX1 3RE, England, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Espert
authors.affiliation: Sir William Dunn School of Pathology and Department of Biochemistry, University of Oxford, Oxford OX1 3RE, England, UK.
authors.forename: Pelin
authors.initials: P
authors.lastname: Uluocak
authors.affiliation: Sir William Dunn School of Pathology and Department of Biochemistry, University of Oxford, Oxford OX1 3RE, England, UK.
authors.forename: Ricardo Nunes
authors.initials: RN
authors.lastname: Bastos
authors.affiliation: Sir William Dunn School of Pathology and Department of Biochemistry, University of Oxford, Oxford OX1 3RE, England, UK.
authors.forename: Davinderpreet
authors.initials: D
authors.lastname: Mangat
authors.affiliation: Sir William Dunn School of Pathology and Department of Biochemistry, University of Oxford, Oxford OX1 3RE, England, UK.
authors.forename: Philipp
authors.initials: P
authors.lastname: Graab
authors.affiliation: Sir William Dunn School of Pathology and Department of Biochemistry, University of Oxford, Oxford OX1 3RE, England, UK ulrike.gruneberg@path.ox.ac.uk.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gruneberg
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000201:enzymology; D059566:M Phase Cell Cycle Checkpoints; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C472643:Knl1 protein, human; D008869:Microtubule-Associated Proteins; D011505:Protein-Tyrosine Kinases; C584277:BUB1 protein, human; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human; D054648:Protein Phosphatase 2