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Chen C, Piano V, Alex A, Han SJY, Huis In 't Veld PJ, Roy B, Fergle D, Musacchio A, Joglekar AP. The structural flexibility of MAD1 facilitates the assembly of the Mitotic Checkpoint Complex. Nat Commun 2023; 14:1529. [PMID: 36934097 PMCID: PMC10024682 DOI: 10.1038/s41467-023-37235-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 03/08/2023] [Indexed: 03/20/2023] Open
Abstract
The spindle assembly checkpoint (SAC) safeguards the genome during cell division by generating an effector molecule known as the Mitotic Checkpoint Complex (MCC). The MCC comprises two subcomplexes: BUBR1:BUB3 and CDC20:MAD2, and the formation of CDC20:MAD2 is the rate-limiting step during MCC assembly. Recent studies show that the rate of CDC20:MAD2 formation is significantly accelerated by the cooperative binding of CDC20 to the SAC proteins MAD1 and BUB1. However, the molecular basis for this acceleration is not fully understood. Here, we demonstrate that the structural flexibility of MAD1 at a conserved hinge near the C-terminus is essential for catalytic MCC assembly. This MAD1 hinge enables the MAD1:MAD2 complex to assume a folded conformation in vivo. Importantly, truncating the hinge reduces the rate of MCC assembly in vitro and SAC signaling in vivo. Conversely, mutations that preserve hinge flexibility retain SAC signaling, indicating that the structural flexibility of the hinge, rather than a specific amino acid sequence, is important for SAC signaling. We summarize these observations as the 'knitting model' that explains how the folded conformation of MAD1:MAD2 promotes CDC20:MAD2 assembly.
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Affiliation(s)
- Chu Chen
- Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Molecular Genetics of Ageing, Max Planck Institute for Biology of Ageing, Cologne, 50931, Germany
| | - Valentina Piano
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
- Institute of Human Genetics, University Hospital Cologne, Cologne, 50931, Germany
| | - Amal Alex
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
| | - Simon J Y Han
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Pim J Huis In 't Veld
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
| | - Babhrubahan Roy
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Daniel Fergle
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Andrea Musacchio
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
- Centre for Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, Essen, 45141, Germany
| | - Ajit P Joglekar
- Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA.
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
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Roy B, Sim J, Han SJY, Joglekar AP. Kre28-Spc105 interaction is essential for Spc105 loading at the kinetochore. Open Biol 2022; 12:210274. [PMID: 35042402 PMCID: PMC8767186 DOI: 10.1098/rsob.210274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Kinetochore (KTs) are macromolecular protein assemblies that attach sister chromatids to spindle microtubules (MTs) and mediate accurate chromosome segregation during mitosis. The outer KT consists of the KMN network, a protein super-complex comprising Knl1 (yeast Spc105), Mis12 (yeast Mtw1), and Ndc80 (yeast Ndc80), which harbours sites for MT binding. Within the KMN network, Spc105 acts as an interaction hub of components involved in spindle assembly checkpoint (SAC) signalling. It is known that Spc105 forms a complex with KT component Kre28. However, where Kre28 physically localizes in the budding yeast KT is not clear. The exact function of Kre28 at the KT is also unknown. Here, we investigate how Spc105 and Kre28 interact and how they are organized within bioriented yeast KTs using genetics and cell biological experiments. Our microscopy data show that Spc105 and Kre28 localize at the KT with a 1 : 1 stoichiometry. We also show that the Kre28-Spc105 interaction is important for Spc105 protein turn-over and essential for their mutual recruitment at the KTs. We created several truncation mutants of kre28 that affect Spc105 loading at the KTs. When over-expressed, these mutants sustain the cell viability, but SAC signalling and KT biorientation are impaired. Therefore, we conclude that Kre28 contributes to chromosome biorientation and high-fidelity segregation at least indirectly by regulating Spc105 localization at the KTs.
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Affiliation(s)
- Babhrubahan Roy
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Janice Sim
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Simon J Y Han
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Ajit P Joglekar
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
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Roy B, Han SJY, Fontan AN, Jema S, Joglekar AP. Aurora B phosphorylates Bub1 to promote spindle assembly checkpoint signaling. Curr Biol 2022; 32:237-247.e6. [PMID: 34861183 PMCID: PMC8752509 DOI: 10.1016/j.cub.2021.10.049] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 08/24/2021] [Accepted: 10/22/2021] [Indexed: 01/12/2023]
Abstract
Accurate chromosome segregation during cell division requires amphitelic chromosome attachment to the spindle apparatus. It is ensured by the combined activity of the spindle assembly checkpoint (SAC),1 a signaling mechanism that delays anaphase onset in response to unattached chromosomes, and an error correction mechanism that eliminates syntelic attachments.2 The SAC becomes active when Mps1 kinase sequentially phosphorylates the kinetochore protein Spc105/KNL1 and the signaling proteins that Spc105/KNL1 recruits to facilitate the production of the mitotic checkpoint complex (MCC).3-8 The error correction mechanism is regulated by the Aurora B kinase, but Aurora B also promotes SAC signaling via indirect mechanisms.9-12 Here we present evidence that Aurora B kinase activity directly promotes MCC production by working downstream of Mps1 in budding yeast and human cells. Using the ectopic SAC activation (eSAC) system, we find that the conditional dimerization of Aurora B in budding yeast and an Aurora B recruitment domain in HeLa cells with either Bub1 or Mad1, but not the phosphodomain of Spc105/KNL1, leads to ectopic MCC production and mitotic arrest.13-16 Importantly, Bub1 must recruit both Mad1 and Cdc20 for this ectopic signaling activity. These and other data show that Aurora B cooperates with Bub1 to promote MCC production, but only after Mps1 licenses Bub1 recruitment to the kinetochore. This direct involvement of Aurora B in SAC signaling may maintain SAC signaling even after Mps1 activity in the kinetochore is lowered.
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Affiliation(s)
- Babhrubahan Roy
- Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl., Ann Arbor, MI-48109, USA
| | - Simon J. Y. Han
- Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl., Ann Arbor, MI-48109, USA,present address: Medical Scientist Training Program, University of Cincinnati College of Medicine, 3230 Eden Ave, Cincinnati, OH 45267, USA
| | - Adrienne N. Fontan
- Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl., Ann Arbor, MI-48109, USA,present address: Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, 455 Main St, Cambridge, MA 02142
| | - Soubhagyalaxmi Jema
- Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl., Ann Arbor, MI-48109, USA
| | - Ajit P. Joglekar
- Cell & Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl., Ann Arbor, MI-48109, USA,corresponding author, lead contact: , Twitter handle: @AjitJoglekar1
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