title: A sequential multi-target Mps1 phosphorylation cascade promotes spindle checkpoint signaling.
abstract: The master spindle checkpoint kinase Mps1 senses kinetochore-microtubule attachment and promotes checkpoint signaling to ensure accurate chromosome segregation. The kinetochore scaffold Knl1, when phosphorylated by Mps1, recruits checkpoint complexes Bub1-Bub3 and BubR1-Bub3 to unattached kinetochores. Active checkpoint signaling ultimately enhances the assembly of the mitotic checkpoint complex (MCC) consisting of BubR1-Bub3, Mad2, and Cdc20, which inhibits the anaphase-promoting complex or cyclosome bound to Cdc20 (APC/CCdc20) to delay anaphase onset. Using in vitro reconstitution, we show that Mps1 promotes APC/C inhibition by MCC components through phosphorylating Bub1 and Mad1. Phosphorylated Bub1 binds to Mad1-Mad2. Phosphorylated Mad1 directly interacts with Cdc20. Mutations of Mps1 phosphorylation sites in Bub1 or Mad1 abrogate the spindle checkpoint in human cells. Therefore, Mps1 promotes checkpoint activation through sequentially phosphorylating Knl1, Bub1, and Mad1. This sequential multi-target phosphorylation cascade makes the checkpoint highly responsive to Mps1 and to kinetochore-microtubule attachment.
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
authors.forename: Zhejian
authors.initials: Z
authors.lastname: Ji
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
authors.forename: Haishan
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
authors.forename: Luying
authors.initials: L
authors.lastname: Jia
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
authors.forename: Hongtao
authors.identifier: 0000-0002-8861-049X
authors.initials: H
authors.lastname: Yu
mesh_terms: D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D018797:Cell Cycle Proteins; C472643:Knl1 protein, human; C501384:MAD1L1 protein, human; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D011505:Protein-Tyrosine Kinases; C584277:BUB1 protein, human; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human
keywords: E. coli; biochemistry; cell biology; human; kinetochore; protein kinase; spindle checkpoint; xenopus