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Sanchez C, Ramirez A, Hodgson L. Unravelling molecular dynamics in living cells: Fluorescent protein biosensors for cell biology. J Microsc 2024. [PMID: 38357769 DOI: 10.1111/jmi.13270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 01/11/2024] [Accepted: 01/22/2024] [Indexed: 02/16/2024]
Abstract
Genetically encoded, fluorescent protein (FP)-based Förster resonance energy transfer (FRET) biosensors are microscopy imaging tools tailored for the precise monitoring and detection of molecular dynamics within subcellular microenvironments. They are characterised by their ability to provide an outstanding combination of spatial and temporal resolutions in live-cell microscopy. In this review, we begin by tracing back on the historical development of genetically encoded FP labelling for detection in live cells, which lead us to the development of early biosensors and finally to the engineering of single-chain FRET-based biosensors that have become the state-of-the-art today. Ultimately, this review delves into the fundamental principles of FRET and the design strategies underpinning FRET-based biosensors, discusses their diverse applications and addresses the distinct challenges associated with their implementation. We place particular emphasis on single-chain FRET biosensors for the Rho family of guanosine triphosphate hydrolases (GTPases), pointing to their historical role in driving our understanding of the molecular dynamics of this important class of signalling proteins and revealing the intricate relationships and regulatory mechanisms that comprise Rho GTPase biology in living cells.
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Affiliation(s)
- Colline Sanchez
- Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, New York, USA
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Andrea Ramirez
- Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, New York, USA
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Louis Hodgson
- Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, New York, USA
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, 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] [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] [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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Kukreja AA, Kavuri S, Joglekar AP. Microtubule Attachment and Centromeric Tension Shape the Protein Architecture of the Human Kinetochore. Curr Biol 2020; 30:4869-4881.e5. [PMID: 33035484 DOI: 10.1016/j.cub.2020.09.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/23/2020] [Accepted: 09/14/2020] [Indexed: 12/18/2022]
Abstract
The nanoscale protein architecture of the kinetochore plays an integral role in specifying the mechanisms underlying its functions in chromosome segregation. However, defining this architecture in human cells remains challenging because of the large size and compositional complexity of the kinetochore. Here, we use Förster resonance energy transfer to reveal the architecture of individual kinetochore-microtubule attachments in human cells. We find that the microtubule-binding domains of the Ndc80 complex cluster at the microtubule plus end. This clustering occurs only after microtubule attachment, and it increases proportionally with centromeric tension. Surprisingly, Ndc80 complex clustering is independent of the organization and number of its centromeric receptors. Moreover, this clustering is similar in yeast and human kinetochores despite significant differences in their centromeric organizations. These and other data suggest that the microtubule-binding interface of the human kinetochore behaves like a flexible "lawn" despite being nucleated by repeating biochemical subunits.
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Affiliation(s)
- Alexander A Kukreja
- Department of Biophysics, University of Michigan, 930 N. University Avenue, Ann Arbor, MI 48109, USA
| | - Sisira Kavuri
- Department of Cellular & Developmental Biology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA
| | - Ajit P Joglekar
- Department of Biophysics, University of Michigan, 930 N. University Avenue, Ann Arbor, MI 48109, USA; Department of Cellular & Developmental Biology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
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Roy B, Han SJ, Fontan AN, Joglekar AP. The copy-number and varied strengths of MELT motifs in Spc105 balance the strength and responsiveness of the spindle assembly checkpoint. eLife 2020; 9:55096. [PMID: 32479259 PMCID: PMC7292645 DOI: 10.7554/elife.55096] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Accepted: 05/29/2020] [Indexed: 12/15/2022] Open
Abstract
During mitosis, the Spindle Assembly Checkpoint (SAC) maintains genome stability while also ensuring timely anaphase onset. To maintain genome stability, the SAC must be strong to delay anaphase even if just one chromosome is unattached, but for timely anaphase onset, it must promptly respond to silencing mechanisms. How the SAC meets these potentially antagonistic requirements is unclear. Here we show that the balance between SAC strength and responsiveness is determined by the number of ‘MELT’ motifs in the kinetochore protein Spc105/KNL1 and their Bub3-Bub1 binding affinities. Many strong MELT motifs per Spc105/KNL1 minimize chromosome missegregation, but too many delay anaphase onset. We demonstrate this by constructing a Spc105 variant that trades SAC responsiveness for much more accurate chromosome segregation. We propose that the necessity of balancing SAC strength and responsiveness drives the dual evolutionary trend of the amplification of MELT motif number, but degeneration of their functionally optimal amino acid sequence.
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Affiliation(s)
- Babhrubahan Roy
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, United States
| | - Simon Jy Han
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, United States
| | - Adrienne Nicole Fontan
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, United States
| | - Ajit P Joglekar
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, United States
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Petazzi RA, Aji AK, Chiantia S. Fluorescence microscopy methods for the study of protein oligomerization. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 169:1-41. [DOI: 10.1016/bs.pmbts.2019.12.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Roy B, Verma V, Sim J, Fontan A, Joglekar AP. Delineating the contribution of Spc105-bound PP1 to spindle checkpoint silencing and kinetochore microtubule attachment regulation. J Cell Biol 2019; 218:3926-3942. [PMID: 31649151 PMCID: PMC6891095 DOI: 10.1083/jcb.201810172] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 06/19/2019] [Accepted: 09/18/2019] [Indexed: 02/01/2023] Open
Abstract
Roy et al. highlight a harmful cross-talk that can arise between spindle assembly checkpoint silencing and chromosome biorientation due to the involvement of protein phosphatase 1 in both the processes. Accurate chromosome segregation during cell division requires the spindle assembly checkpoint (SAC), which detects unattached kinetochores, and an error correction mechanism that destabilizes incorrect kinetochore–microtubule attachments. While the SAC and error correction are both regulated by protein phosphatase 1 (PP1), which silences the SAC and stabilizes kinetochore–microtubule attachments, how these distinct PP1 functions are coordinated remains unclear. Here, we investigate the contribution of PP1, docked on its conserved kinetochore receptor Spc105/Knl1, to SAC silencing and attachment regulation. We find that Spc105-bound PP1 is critical for SAC silencing but dispensable for error correction; in fact, reduced PP1 docking on Spc105 improved chromosome segregation and viability of mutant/stressed states. We additionally show that artificially recruiting PP1 to Spc105/Knl1 before, but not after, chromosome biorientation interfered with error correction. These observations lead us to propose that recruitment of PP1 to Spc105/Knl1 is carefully regulated to ensure that chromosome biorientation precedes SAC silencing, thereby ensuring accurate chromosome segregation.
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Affiliation(s)
- Babhrubahan Roy
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Vikash Verma
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Janice Sim
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Adrienne Fontan
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Ajit P Joglekar
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI .,Department of Biophysics, University of Michigan, Ann Arbor, MI
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8
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Skruzny M, Pohl E, Abella M. FRET Microscopy in Yeast. BIOSENSORS 2019; 9:E122. [PMID: 31614546 PMCID: PMC6956097 DOI: 10.3390/bios9040122] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 09/19/2019] [Accepted: 09/30/2019] [Indexed: 02/06/2023]
Abstract
Förster resonance energy transfer (FRET) microscopy is a powerful fluorescence microscopy method to study the nanoscale organization of multiprotein assemblies in vivo. Moreover, many biochemical and biophysical processes can be followed by employing sophisticated FRET biosensors directly in living cells. Here, we summarize existing FRET experiments and biosensors applied in yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, two important models of fundamental biomedical research and efficient platforms for analyses of bioactive molecules. We aim to provide a practical guide on suitable FRET techniques, fluorescent proteins, and experimental setups available for successful FRET experiments in yeasts.
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Affiliation(s)
- Michal Skruzny
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany.
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), 35043 Marburg, Germany.
| | - Emma Pohl
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), 35043 Marburg, Germany
| | - Marc Abella
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), 35043 Marburg, Germany
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Guo W, Kumar S, Görlitz F, Garcia E, Alexandrov Y, Munro I, Kelly DJ, Warren S, Thorpe P, Dunsby C, French P. Automated Fluorescence Lifetime Imaging High-Content Analysis of Förster Resonance Energy Transfer between Endogenously Labeled Kinetochore Proteins in Live Budding Yeast Cells. SLAS Technol 2019; 24:308-320. [PMID: 30629461 PMCID: PMC6537140 DOI: 10.1177/2472630318819240] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 11/16/2018] [Accepted: 11/23/2018] [Indexed: 11/23/2022]
Abstract
We describe an open-source automated multiwell plate fluorescence lifetime imaging (FLIM) methodology to read out Förster resonance energy transfer (FRET) between fluorescent proteins (FPs) labeling endogenous kinetochore proteins (KPs) in live budding yeast cells. The low copy number of many KPs and their small spatial extent present significant challenges for the quantification of donor fluorescence lifetime in the presence of significant cellular autofluorescence and photobleaching. Automated FLIM data acquisition was controlled by µManager and incorporated wide-field time-gated imaging with optical sectioning to reduce background fluorescence. For data analysis, we used custom MATLAB-based software tools to perform kinetochore foci segmentation and local cellular background subtraction and fitted the fluorescence lifetime data using the open-source FLIMfit software. We validated the methodology using endogenous KPs labeled with mTurquoise2 FP and/or yellow FP and measured the donor fluorescence lifetimes for foci comprising 32 kinetochores with KP copy numbers as low as ~2 per kinetochore under an average labeling efficiency of 50%. We observed changes of median donor lifetime ≥250 ps for KPs known to form dimers. Thus, this FLIM high-content analysis platform enables the screening of relatively low-copy-number endogenous protein-protein interactions at spatially confined macromolecular complexes.
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Affiliation(s)
- Wenjun Guo
- Photonics Group, Department of Physics,
Imperial College London, London, UK
- Francis Crick Institute, London,
UK
| | - Sunil Kumar
- Photonics Group, Department of Physics,
Imperial College London, London, UK
- Francis Crick Institute, London,
UK
| | - Frederik Görlitz
- Photonics Group, Department of Physics,
Imperial College London, London, UK
| | - Edwin Garcia
- Photonics Group, Department of Physics,
Imperial College London, London, UK
| | - Yuriy Alexandrov
- Photonics Group, Department of Physics,
Imperial College London, London, UK
- Francis Crick Institute, London,
UK
| | - Ian Munro
- Photonics Group, Department of Physics,
Imperial College London, London, UK
| | - Douglas J. Kelly
- Photonics Group, Department of Physics,
Imperial College London, London, UK
- RIKEN Center for Biodynamic Systems
Research, Kobe, Japan
| | - Sean Warren
- Garvan Institute of Medical Research,
University of New South Wales, Sydney, New South Wales, Australia
| | - Peter Thorpe
- Francis Crick Institute, London,
UK
- Queen Mary University of London, London,
UK
| | - Christopher Dunsby
- Photonics Group, Department of Physics,
Imperial College London, London, UK
- Francis Crick Institute, London,
UK
- Centre for Pathology, Imperial College
London, London, UK
| | - Paul French
- Photonics Group, Department of Physics,
Imperial College London, London, UK
- Francis Crick Institute, London,
UK
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Aravamudhan P, Chen R, Roy B, Sim J, Joglekar AP. Dual mechanisms regulate the recruitment of spindle assembly checkpoint proteins to the budding yeast kinetochore. Mol Biol Cell 2016; 27:3405-3417. [PMID: 27170178 PMCID: PMC5221577 DOI: 10.1091/mbc.e16-01-0007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 05/03/2016] [Indexed: 01/10/2023] Open
Abstract
Quantitative knowledge of the recruitment of spindle assembly checkpoint (SAC) proteins by the kinetochore is essential to understanding the mechanisms that regulate protein recruitment and hence the strength of the SAC. Here this recruitment is quantified, and novel mechanisms are identified that strongly modulate SAC protein recruitment by the kinetochore. Recruitment of spindle assembly checkpoint (SAC) proteins by an unattached kinetochore leads to SAC activation. This recruitment is licensed by the Mps1 kinase, which phosphorylates the kinetochore protein Spc105 at one or more of its six MELT repeats. Spc105 then recruits the Bub3-Bub1 and Mad1-Mad2 complexes, which produce the inhibitory signal that arrests cell division. The strength of this signal depends, in part, on the number of Bub3-Bub1 and Mad1-Mad2 molecules that Spc105 recruits. Therefore regulation of this recruitment will influence SAC signaling. To understand this regulation, we established the physiological binding curves that describe the binding of Bub3-Bub1 and Mad1-Mad2 to the budding yeast kinetochore. We find that the binding of both follows the mass action law. Mps1 likely phosphorylates all six MELT repeats of Spc105. However, two mechanisms prevent Spc105 from recruiting six Bub3-Bub1 molecules: low Bub1 abundance and hindrance in the binding of more than one Bub3-Bub1 molecule to the same Spc105. Surprisingly, the kinetochore recruits two Mad1-Mad2 heterotetramers for every Bub3-Bub1 molecule. Finally, at least three MELT repeats per Spc105 are needed for accurate chromosome segregation. These data reveal that kinetochore-intrinsic and -extrinsic mechanisms influence the physiological operation of SAC signaling, potentially to maximize chromosome segregation accuracy.
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Affiliation(s)
- Pavithra Aravamudhan
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Renjie Chen
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Babhrubahan Roy
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Janice Sim
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Ajit P Joglekar
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
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Aravamudhan P, Goldfarb AA, Joglekar AP. The kinetochore encodes a mechanical switch to disrupt spindle assembly checkpoint signalling. Nat Cell Biol 2015; 17:868-79. [PMID: 26053220 PMCID: PMC4630029 DOI: 10.1038/ncb3179] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 04/23/2015] [Indexed: 12/14/2022]
Abstract
The spindle assembly checkpoint (SAC) is a unique signalling mechanism that responds to the state of attachment of the kinetochore to spindle microtubules. SAC signalling is activated by unattached kinetochores, and it is silenced after these kinetochores form end-on microtubule attachments. Although the biochemical cascade of SAC signalling is well understood, how kinetochore-microtubule attachment disrupts it remained unknown. Here we show that, in budding yeast, end-on microtubule attachment to the kinetochore physically separates the Mps1 kinase, which probably binds to the calponin homology domain of Ndc80, from the kinetochore substrate of Mps1, Spc105 (KNL1 orthologue). This attachment-mediated separation disrupts the phosphorylation of Spc105, and enables SAC silencing. Additionally, the Dam1 complex may act as a barrier that shields Spc105 from Mps1. Together these data suggest that the protein architecture of the kinetochore encodes a mechanical switch. End-on microtubule attachment to the kinetochore turns this switch off to silence the SAC.
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Affiliation(s)
| | - Alan A. Goldfarb
- Cell and developmental biology, University of Michigan, 109 Zina Pitcher Place, 3067 BSRB, Ann Arbor, MI-48109, USA
| | - Ajit P. Joglekar
- Biophysics, University of Michigan, Ann Arbor, MI-48109, USA
- Cell and developmental biology, University of Michigan, 109 Zina Pitcher Place, 3067 BSRB, Ann Arbor, MI-48109, USA
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Aravamudhan P, Felzer-Kim I, Gurunathan K, Joglekar AP. Assembling the protein architecture of the budding yeast kinetochore-microtubule attachment using FRET. Curr Biol 2014; 24:1437-46. [PMID: 24930965 PMCID: PMC4320969 DOI: 10.1016/j.cub.2014.05.014] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 04/20/2014] [Accepted: 05/06/2014] [Indexed: 11/20/2022]
Abstract
BACKGROUND The kinetochore is a multiprotein machine that couples chromosome movement to microtubule (MT) polymerization and depolymerization. It uses numerous copies of at least three MT-binding proteins to generate bidirectional movement. The nanoscale organization of these proteins within the kinetochore plays an important role in shaping the mechanisms that drive persistent, bidirectional movement of the kinetochore. RESULTS We used fluorescence resonance energy transfer (FRET) between genetically encoded fluorescent proteins fused to kinetochore subunits to reconstruct the nanoscale organization of the budding yeast kinetochore. We performed >60 FRET and high-resolution colocalization measurements involving the essential MT-binding kinetochore components: Ndc80, Dam1, Spc105, and Stu2. These measurements reveal that neighboring Ndc80 complexes within the kinetochore are narrowly distributed along the length of the MT. Dam1 complex molecules are concentrated near the MT-binding domains of Ndc80. Stu2 localizes in high abundance within a narrowly defined territory within the kinetochore centered ∼20 nm on the centromeric side of the Dam1 complex. CONCLUSIONS Our data show that the MT attachment site of the budding yeast kinetochore is well organized. Ndc80, Dam1, and Stu2 are all narrowly distributed about their average positions along the kinetochore-MT axis. The relative organization of these components, their narrow distributions, and their known MT-binding properties together elucidate how their combined actions generate persistent, bidirectional kinetochore movement coupled to MT polymerization and depolymerization.
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Affiliation(s)
- Pavithra Aravamudhan
- Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109-1055, USA
| | - Isabella Felzer-Kim
- Cell and Developmental Biology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA
| | - Kaushik Gurunathan
- Sastra University, Tirumalaisamudram, Thanjavur, Tamil Nadu 613402, India
| | - Ajit P Joglekar
- Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109-1055, USA; Cell and Developmental Biology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
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