title: Basis of catalytic assembly of the mitotic checkpoint complex.
abstract: In mitosis, for each daughter cell to inherit an accurate copy of the genome from the mother cell, sister chromatids in the mother cell must attach to microtubules emanating from opposite poles of the mitotic spindle, a process known as bi-orientation. A surveillance mechanism, termed the spindle assembly checkpoint (SAC), monitors the microtubule attachment process and can temporarily halt the separation of sister chromatids and the completion of mitosis until bi-orientation is complete. SAC failure results in abnormal chromosome numbers, termed aneuploidy, in the daughter cells, a hallmark of many tumours. The HORMA-domain-containing protein mitotic arrest deficient 2 (MAD2) is a subunit of the SAC effector mitotic checkpoint complex (MCC). Structural conversion from the open to the closed conformation of MAD2 is required for MAD2 to be incorporated into the MCC. In vitro, MAD2 conversion and MCC assembly take several hours, but in cells the SAC response is established in a few minutes. Here, to address this discrepancy, we reconstituted a near-complete SAC signalling system with purified components and monitored assembly of the MCC in real time. A marked acceleration in MAD2 conversion and MCC assembly was observed when monopolar spindle 1 (MPS1) kinase phosphorylated the MAD1-MAD2 complex, triggering it to act as the template for MAD2 conversion and therefore contributing to the establishment of a physical platform for MCC assembly. Thus, catalytic activation of the SAC depends on regulated protein-protein interactions that accelerate the spontaneous but rate-limiting conversion of MAD2 required for MCC assembly.
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Alex C
authors.initials: AC
authors.lastname: Faesen
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Thanasoula
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Stefano
authors.initials: S
authors.lastname: Maffini
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Breit
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Müller
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Suzan
authors.initials: S
authors.lastname: van Gerwen
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Bange
authors.affiliation: Department of Mechanistic Cell Biology, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.|Centre for Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, Universitätsstraße, 45141 Essen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Musacchio
mesh_terms: D055162:Biocatalysis; D018797:Cell Cycle Proteins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D018386:Kinetochores / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints / Q000502:physiology*; D064246:Mad2 Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D055550:Protein Stability; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D013997:Time Factors
chemical_list: D018797:Cell Cycle Proteins; C501384:MAD1L1 protein, human; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human