1
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Polverino F, Mastrangelo A, Guarguaglini G. Contribution of AurkA/TPX2 Overexpression to Chromosomal Imbalances and Cancer. Cells 2024; 13:1397. [PMID: 39195284 DOI: 10.3390/cells13161397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2024] [Revised: 08/14/2024] [Accepted: 08/15/2024] [Indexed: 08/29/2024] Open
Abstract
The AurkA serine/threonine kinase is a key regulator of cell division controlling mitotic entry, centrosome maturation, and chromosome segregation. The microtubule-associated protein TPX2 controls spindle assembly and is the main AurkA regulator, contributing to AurkA activation, localisation, and stabilisation. Since their identification, AurkA and TPX2 have been described as being overexpressed in cancer, with a significant correlation with highly proliferative and aneuploid tumours. Despite the frequent occurrence of AurkA/TPX2 co-overexpression in cancer, the investigation of their involvement in tumorigenesis and cancer therapy resistance mostly arises from studies focusing only on one at the time. Here, we review the existing literature and discuss the mitotic phenotypes described under conditions of AurkA, TPX2, or AurkA/TPX2 overexpression, to build a picture that may help clarify their oncogenic potential through the induction of chromosome instability. We highlight the relevance of the AurkA/TPX2 complex as an oncogenic unit, based on which we discuss recent strategies under development that aim at disrupting the complex as a promising therapeutic perspective.
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Affiliation(s)
- Federica Polverino
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy
| | - Anna Mastrangelo
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy
| | - Giulia Guarguaglini
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy
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2
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Chang CC, Coyle SM. Regulatable assembly of synthetic microtubule architectures using engineered microtubule-associated protein-IDR condensates. J Biol Chem 2024; 300:107544. [PMID: 38992434 PMCID: PMC11342785 DOI: 10.1016/j.jbc.2024.107544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 06/25/2024] [Accepted: 06/28/2024] [Indexed: 07/13/2024] Open
Abstract
Microtubule filaments are assembled into higher-order structures using microtubule-associated proteins. However, synthetic MAPs that direct the formation of new structures are challenging to design, as nanoscale biochemical activities must be organized across micron length-scales. Here, we develop modular MAP-IDR condensates (synMAPs) that enable inducible assembly of higher-order microtubule structures for synthetic exploration in vitro and in mammalian cells. synMAPs harness a small microtubule-binding domain from oligodendrocytes (TPPP) whose activity we show can be rewired by interaction with unrelated condensate-forming IDR sequences. This combination is sufficient to allow synMAPs to self-organize multivalent structures that bind and bridge microtubules into higher-order architectures. By regulating the connection between the microtubule-binding domain and condensate-forming components of a synMAP, the formation of these structures can be triggered by small molecules or cell-signaling inputs. We systematically test a panel of synMAP circuit designs to define how the assembly of these synthetic microtubule structures can be controlled at the nanoscale (via microtubule-binding affinity) and microscale (via condensate formation). synMAPs thus provide a modular starting point for the design of higher-order microtubule systems and an experimental testbed for exploring condensate-directed mechanisms of higher-order microtubule assembly from the bottom-up.
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Affiliation(s)
- Chih-Chia Chang
- Biophysics Graduate Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Scott M Coyle
- Biophysics Graduate Program, University of Wisconsin-Madison, Madison, Wisconsin, USA; Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA.
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3
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Pena GE, Zhou X, Slevin L, Brownlee C, Heald R. Identification of a motif in TPX2 that regulates spindle architecture in Xenopus egg extracts. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.10.579770. [PMID: 38370704 PMCID: PMC10871311 DOI: 10.1101/2024.02.10.579770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
A bipolar spindle composed of microtubules and many associated proteins functions to segregate chromosomes during cell division in all eukaryotes, yet spindle size and architecture varies dramatically across different species and cell types. Targeting protein for Xklp2 (TPX2) is one candidate factor for modulating spindle microtubule organization through its roles in branching microtubule nucleation, activation of the mitotic kinase Aurora A, and association with the kinesin-5 (Eg5) motor. Here we identify a conserved nuclear localization sequence (NLS) motif, 123 KKLK 126 in X. laevis TPX2, which regulates astral microtubule formation and spindle pole morphology in Xenopus egg extracts. Addition of recombinant TPX2 with this sequence mutated to AALA dramatically increased spontaneous formation of microtubule asters and recruitment of phosphorylated Aurora A, pericentrin, and Eg5 to meiotic spindle poles. We propose that TPX2 is a linchpin spindle assembly factor whose regulation contributes to the recruitment and activation of multiple microtubule polymerizing and organizing proteins, generating distinct spindle architectures.
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4
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Romer B, Travis SM, Mahon BP, McManus CT, Jeffrey PD, Coudray N, Raghu R, Rale MJ, Zhong ED, Bhabha G, Petry S. Conformational states of the microtubule nucleator, the γ-tubulin ring complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.19.572162. [PMID: 38187763 PMCID: PMC10769196 DOI: 10.1101/2023.12.19.572162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Microtubules (MTs) perform essential functions in the cell, and it is critical that they are made at the correct cellular location and cell cycle stage. This nucleation process is catalyzed by the γ-tubulin ring complex (γ-TuRC), a cone-shaped protein complex composed of over 30 subunits. Despite recent insight into the structure of vertebrate γ-TuRC, which shows that its diameter is wider than that of a MT, and that it exhibits little of the symmetry expected for an ideal MT template, the question of how γ-TuRC achieves MT nucleation remains open. Here, we utilized single particle cryo-EM to identify two conformations of γ-TuRC. The helix composed of 14 γ-tubulins at the top of the γ-TuRC cone undergoes substantial deformation, which is predominantly driven by bending of the hinge between the GRIP1 and GRIP2 domains of the γ-tubulin complex proteins. However, surprisingly, this deformation does not remove the inherent asymmetry of γ-TuRC. To further investigate the role of γ-TuRC conformational change, we used cryo electron-tomography (cryo-ET) to obtain a 3D reconstruction of γ-TuRC bound to a nucleated MT, providing insight into the post-nucleation state. Rigid-body fitting of our cryo-EM structures into this reconstruction suggests that the MT lattice is nucleated by spokes 2 through 14 of the γ-tubulin helix, which entails spokes 13 and 14 becoming more structured than what is observed in apo γ-TuRC. Together, our results allow us to propose a model for conformational changes in γ-TuRC and how these may facilitate MT formation in a cell.
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Affiliation(s)
- Brianna Romer
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Sophie M. Travis
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Brian P. Mahon
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
- Present address: Molecular Structure and Design, Bristol Myers Squibb, Princeton, NJ, USA
| | - Collin T. McManus
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Philip D. Jeffrey
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Nicolas Coudray
- Department of Cell Biology, NYU School of Medicine, New York City, NY, USA
- Applied Bioinformatics Laboratories, NYU School of Medicine, New York, NY, USA
| | - Rishwanth Raghu
- Department of Computer Science, Princeton University, Princeton, NJ, USA
| | - Michael J. Rale
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
- Present address: Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Ellen D. Zhong
- Department of Computer Science, Princeton University, Princeton, NJ, USA
| | - Gira Bhabha
- Department of Cell Biology, NYU School of Medicine, New York City, NY, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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5
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Valdez V, Ma M, Gouveia B, Zhang R, Petry S. HURP facilitates spindle assembly by stabilizing microtubules and working synergistically with TPX2. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.18.571906. [PMID: 38187686 PMCID: PMC10769297 DOI: 10.1101/2023.12.18.571906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
In large vertebrate spindles, the majority of microtubules are formed via branching microtubule nucleation, whereby microtubules nucleate along the side of pre-existing microtubules. Hepatoma up-regulated protein (HURP) is a microtubule-associated protein that has been implicated in spindle assembly, but its mode of action is yet to be defined. In this study, we show that HURP is necessary for RanGTP-induced branching microtubule nucleation in Xenopus egg extract. Specifically, HURP stabilizes the microtubule lattice to promote microtubule formation from γ-TuRC. This function is shifted to promote branching microtubule nucleation in the presence of TPX2, another branching-promoting factor, as HURP's localization to microtubules is enhanced by TPX2 condensation. Lastly, we provide a structure of HURP on the microtubule lattice, revealing how HURP binding stabilizes the microtubule lattice. We propose a model in which HURP stabilizes microtubules during their formation, and TPX2 preferentially enriches HURP to microtubules to promote branching microtubule nucleation and thus spindle assembly.
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Affiliation(s)
- Venecia Valdez
- Princeton University, Department of Molecular Biology, Princeton, New Jersey, United States
| | - Meisheng Ma
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, School of Medicine (St. Louis, Missouri, United States)
- Present address: Department of Histology and Embryology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology (Wuhan, Hubei, China)
| | - Bernardo Gouveia
- Princeton University, Department of Chemical and Biological Engineering, Princeton, New Jersey, United States
| | - Rui Zhang
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, School of Medicine (St. Louis, Missouri, United States)
| | - Sabine Petry
- Princeton University, Department of Molecular Biology, Princeton, New Jersey, United States
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6
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Chang CC, Coyle SM. Regulatable assembly of synthetic microtubule architectures using engineered MAP-IDR condensates. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.14.532644. [PMID: 38105997 PMCID: PMC10723337 DOI: 10.1101/2023.03.14.532644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Microtubules filaments are assembled into higher-order structures and machines critical for cellular processes using microtubule-associated proteins (MAPs). However, the design of synthetic MAPs that direct the formation of new structures in cells is challenging, as nanoscale biochemical activities must be organized across micron length-scales. Here we develop synthetic MAP-IDR condensates (synMAPs) that provide tunable and regulatable assembly of higher-order microtubule structures in vitro and in mammalian cells. synMAPs harness a small microtubule-binding domain from oligodendrocytes (TPPP) whose activity can be synthetically rewired by interaction with condensate-forming IDR sequences. This combination allows synMAPs to self-organize multivalent structures that bind and bridge microtubules into synthetic architectures. Regulating the connection between the microtubule-binding and condensate-forming components allows synMAPs to act as nodes in more complex cytoskeletal circuits in which the formation and dynamics of the microtubule structure can be controlled by small molecules or cell-signaling inputs. By systematically testing a panel of synMAP circuit designs, we define a two-level control scheme for dynamic assembly of microtubule architectures at the nanoscale (via microtubule-binding) and microscale (via condensate formation). synMAPs provide a compact and rationally engineerable starting point for the design of more complex microtubule architectures and cellular machines.
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Affiliation(s)
- Chih-Chia Chang
- Biophysics Graduate Program, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Scott M. Coyle
- Biophysics Graduate Program, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53705, USA
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7
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Ramšak M, Ramirez DA, Hough LE, Shirts MR, Vidmar S, Eleršič Filipič K, Anderluh G, Jerala R. Programmable de novo designed coiled coil-mediated phase separation in mammalian cells. Nat Commun 2023; 14:7973. [PMID: 38042897 PMCID: PMC10693550 DOI: 10.1038/s41467-023-43742-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 11/17/2023] [Indexed: 12/04/2023] Open
Abstract
Membraneless liquid compartments based on phase-separating biopolymers have been observed in diverse cell types and attributed to weak multivalent interactions predominantly based on intrinsically disordered domains. The design of liquid-liquid phase separated (LLPS) condensates based on de novo designed tunable modules that interact in a well-understood, controllable manner could improve our understanding of this phenomenon and enable the introduction of new features. Here we report the construction of CC-LLPS in mammalian cells, based on designed coiled-coil (CC) dimer-forming modules, where the stability of CC pairs, their number, linkers, and sequential arrangement govern the transition between diffuse, liquid and immobile condensates and are corroborated by coarse-grained molecular simulations. Through modular design, we achieve multiple coexisting condensates, chemical regulation of LLPS, condensate fusion, formation from either one or two polypeptide components or LLPS regulation by a third polypeptide chain. These findings provide further insights into the principles underlying LLPS formation and a design platform for controlling biological processes.
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Affiliation(s)
- Maruša Ramšak
- Department of Synthetic Biology and Immunology, National Institute of Chemistry, Ljubljana, Slovenia
- Interdisciplinary doctoral study of biomedicine, Medical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Dominique A Ramirez
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Loren E Hough
- Department of Physics and BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA
| | - Michael R Shirts
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO, USA
| | - Sara Vidmar
- Department of Synthetic Biology and Immunology, National Institute of Chemistry, Ljubljana, Slovenia
- Interdisciplinary doctoral study of biomedicine, Medical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Kristina Eleršič Filipič
- Department of Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Gregor Anderluh
- Department of Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Roman Jerala
- Department of Synthetic Biology and Immunology, National Institute of Chemistry, Ljubljana, Slovenia.
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8
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Yang S, Au FK, Li G, Lin J, Li XD, Qi RZ. Autoinhibitory mechanism controls binding of centrosomin motif 1 to γ-tubulin ring complex. J Cell Biol 2023; 222:e202007101. [PMID: 37213089 PMCID: PMC10202828 DOI: 10.1083/jcb.202007101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 01/03/2023] [Accepted: 03/24/2023] [Indexed: 05/23/2023] Open
Abstract
The γ-tubulin ring complex (γTuRC) is the principal nucleator of cellular microtubules, and the microtubule-nucleating activity of the complex is stimulated by binding to the γTuRC-mediated nucleation activator (γTuNA) motif. The γTuNA is part of the centrosomin motif 1 (CM1), which is widely found in γTuRC stimulators, including CDK5RAP2. Here, we show that a conserved segment within CM1 binds to the γTuNA and blocks its association with γTuRCs; therefore, we refer to this segment as the γTuNA inhibitor (γTuNA-In). Mutational disruption of the interaction between the γTuNA and the γTuNA-In results in a loss of autoinhibition, which consequently augments microtubule nucleation on centrosomes and the Golgi complex, the two major microtubule-organizing centers. This also causes centrosome repositioning, leads to defects in Golgi assembly and organization, and affects cell polarization. Remarkably, phosphorylation of the γTuNA-In, probably by Nek2, counteracts the autoinhibition by disrupting the γTuNA‒γTuNA-In interaction. Together, our data reveal an on-site mechanism for controlling γTuNA function.
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Affiliation(s)
- Shaozhong Yang
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Franco K.C. Au
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Gefei Li
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Jianwei Lin
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Xiang David Li
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Robert Z. Qi
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
- Bioscience and Biomedical Engineering Thrust, The Hong Kong University of Science and Technology (Guangzhou), Guangzhou, China
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9
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Guo C, Alfaro-Aco R, Zhang C, Russell RW, Petry S, Polenova T. Structural basis of protein condensation on microtubules underlying branching microtubule nucleation. Nat Commun 2023; 14:3682. [PMID: 37344496 PMCID: PMC10284871 DOI: 10.1038/s41467-023-39176-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 06/01/2023] [Indexed: 06/23/2023] Open
Abstract
Targeting protein for Xklp2 (TPX2) is a key factor that stimulates branching microtubule nucleation during cell division. Upon binding to microtubules (MTs), TPX2 forms condensates via liquid-liquid phase separation, which facilitates recruitment of microtubule nucleation factors and tubulin. We report the structure of the TPX2 C-terminal minimal active domain (TPX2α5-α7) on the microtubule lattice determined by magic-angle-spinning NMR. We demonstrate that TPX2α5-α7 forms a co-condensate with soluble tubulin on microtubules and binds to MTs between two adjacent protofilaments and at the intersection of four tubulin heterodimers. These interactions stabilize the microtubules and promote the recruitment of tubulin. Our results reveal that TPX2α5-α7 is disordered in solution and adopts a folded structure on MTs, indicating that TPX2α5-α7 undergoes structural changes from unfolded to folded states upon binding to microtubules. The aromatic residues form dense interactions in the core, which stabilize folding of TPX2α5-α7 on microtubules. This work informs on how the phase-separated TPX2α5-α7 behaves on microtubules and represents an atomic-level structural characterization of a protein that is involved in a condensate on cytoskeletal filaments.
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Affiliation(s)
- Changmiao Guo
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
| | - Raymundo Alfaro-Aco
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Chunting Zhang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
| | - Ryan W Russell
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08544, USA.
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA.
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10
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Kraus J, Travis SM, King MR, Petry S. Augmin is a Ran-regulated spindle assembly factor. J Biol Chem 2023; 299:104736. [PMID: 37086784 DOI: 10.1016/j.jbc.2023.104736] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 04/24/2023] Open
Abstract
Mitotic spindles are composed of microtubules (MTs) that must nucleate at the right place and time. Ran regulates this process by directly controlling the release of spindle assembly factors (SAFs) from nucleocytoplasmic shuttle proteins importin-αβ and subsequently forms a biochemical gradient of SAFs localized around chromosomes. The majority of spindle MTs are generated by branching MT nucleation, which has been shown to require an eight-subunit protein complex known as augmin. InXenopus laevis, Ran can control branching through a canonical SAF, TPX2, which is non-essential in Drosophila melanogaster embryos and HeLa cells. Thus, how Ran regulates branching MT nucleation when TPX2 is not required remains unknown. Here, we use in vitro pulldowns and TIRF microscopy to show that augmin is a Ran-regulated SAF. We demonstrate that augmin directly interacts with both importin-α and importin-β through two nuclear localization sequences on the Haus8 subunit, which overlap with the MT binding site. Moreover, we show Ran controls localization of augmin to MTs in both Xenopus egg extract and in vitro. Our results demonstrate that RanGTP directly regulates augmin, which establishes a new way by which Ran controls branching MT nucleation and spindle assembly both in the absence and presence of TPX2.
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Affiliation(s)
- Jodi Kraus
- Department of Molecular Biology; Princeton University; Princeton, NJ, 08544; USA
| | - Sophie M Travis
- Department of Molecular Biology; Princeton University; Princeton, NJ, 08544; USA
| | - Matthew R King
- Department of Molecular Biology; Princeton University; Princeton, NJ, 08544; USA
| | - Sabine Petry
- Department of Molecular Biology; Princeton University; Princeton, NJ, 08544; USA.
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11
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Biomolecular condensation involving the cytoskeleton. Brain Res Bull 2023; 194:105-117. [PMID: 36690162 DOI: 10.1016/j.brainresbull.2023.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 01/07/2023] [Accepted: 01/19/2023] [Indexed: 01/22/2023]
Abstract
Biomolecular condensation of proteins contributes to the organization of the cytoplasm and nucleoplasm. A number of condensation processes appear to be directly involved in regulating the structure, function and dynamics of the cytoskeleton. Liquid-liquid phase separation of cytoskeleton proteins, together with polymerization modulators, promotes cytoskeletal fiber nucleation and branching. Furthermore, the attachment of protein condensates to the cytoskeleton can contribute to cytoskeleton stability and organization, regulate transport, create patterns of functional reaction containers, and connect the cytoskeleton with membranes. Surface-bound condensates can exert and buffer mechanical forces that give stability and flexibility to the cytoskeleton, thus, may play a large role in cell biology. In this review, we introduce the concept and role of cellular biomolecular condensation, explain its special function on cytoskeletal fiber surfaces, and point out potential definition and experimental caveats. We review the current literature on protein condensation processes related to the actin, tubulin, and intermediate filament cytoskeleton, and discuss some of them in the context of neurobiology. In summary, we provide an overview about biomolecular condensation in relation to cytoskeleton structure and function, which offers a base for the exploration and interpretation of cytoskeletal condensates in neurobiology.
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12
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Rale MJ, Romer B, Mahon BP, Travis SM, Petry S. The conserved centrosomin motif, γTuNA, forms a dimer that directly activates microtubule nucleation by the γ-tubulin ring complex (γTuRC). eLife 2022; 11:e80053. [PMID: 36515268 PMCID: PMC9859039 DOI: 10.7554/elife.80053] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 12/07/2022] [Indexed: 12/15/2022] Open
Abstract
To establish the microtubule cytoskeleton, the cell must tightly regulate when and where microtubules are nucleated. This regulation involves controlling the initial nucleation template, the γ-tubulin ring complex (γTuRC). Although γTuRC is present throughout the cytoplasm, its activity is restricted to specific sites including the centrosome and Golgi. The well-conserved γ-tubulin nucleation activator (γTuNA) domain has been reported to increase the number of microtubules (MTs) generated by γTuRCs. However, previously we and others observed that γTuNA had a minimal effect on the activity of antibody-purified Xenopus γTuRCs in vitro (Thawani et al., eLife, 2020; Liu et al., 2020). Here, we instead report, based on improved versions of γTuRC, γTuNA, and our TIRF assay, the first real-time observation that γTuNA directly increases γTuRC activity in vitro, which is thus a bona fide γTuRC activator. We further validate this effect in Xenopus egg extract. Via mutation analysis, we find that γTuNA is an obligate dimer. Moreover, efficient dimerization as well as γTuNA's L70, F75, and L77 residues are required for binding to and activation of γTuRC. Finally, we find that γTuNA's activating effect opposes inhibitory regulation by stathmin. In sum, our improved assays prove that direct γTuNA binding strongly activates γTuRCs, explaining previously observed effects of γTuNA expression in cells and illuminating how γTuRC-mediated microtubule nucleation is regulated.
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Affiliation(s)
- Michael J Rale
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Brianna Romer
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Brian P Mahon
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Sophie M Travis
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Sabine Petry
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
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13
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Effects of Ran-GTP/importin β inhibition on the meiotic division of porcine oocytes. Histochem Cell Biol 2022; 158:571-582. [PMID: 35930054 DOI: 10.1007/s00418-022-02134-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2022] [Indexed: 12/13/2022]
Abstract
The Ran-GTP/importin β pathway has been implicated in a diverse array of mitotic functions in somatic mitosis; however, the possible meiotic roles of Ran-GTP/importin β in mammalian oocyte meiosis are still not fully understood. In the present study, importazole (IPZ), a small molecule inhibitor of the interaction between Ran and importin β was used to explore the potential meiotic roles of Ran-GTP/importin β in porcine oocytes undergoing meiosis. After IPZ treatment, the extrusion rate of the first polar body (PB1) was significantly decreased, and a higher proportion of the oocytes were arrested at the germinal vesicle breakdown (GVBD) stage. Moreover, IPZ treatment led to severe defects in metaphase I (MI) spindle assembly and chromosome alignment during the germinal vesicle (GV)-to-MI stage, as well as failure of metaphase II (MII) spindle reassembly and homologous chromosome segregation during the MI-to-MII stage. Notably, IPZ treatment decreased TPX2 expression and abnormal subcellular localization. Furthermore, the expression levels of aurora kinase A (AURKA) and transforming acidic coiled-coil 3 (TACC3) were significantly reduced after IPZ treatment. Collectively, these data indicate that the interaction of Ran-GTP and importin β is essential for proper spindle assembly and successful chromosome segregation during two consecutive meiotic divisions in porcine oocytes, and regulation of this complex might be related to its effect on the TPX2 signaling cascades.
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14
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Gabel CA, Li Z, DeMarco AG, Zhang Z, Yang J, Hall MC, Barford D, Chang L. Molecular architecture of the augmin complex. Nat Commun 2022; 13:5449. [PMID: 36114186 PMCID: PMC9481612 DOI: 10.1038/s41467-022-33227-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 09/05/2022] [Indexed: 12/21/2022] Open
Abstract
Accurate segregation of chromosomes during mitosis depends on the correct assembly of the mitotic spindle, a bipolar structure composed mainly of microtubules. The augmin complex, or homologous to augmin subunits (HAUS) complex, is an eight-subunit protein complex required for building robust mitotic spindles in metazoa. Augmin increases microtubule density within the spindle by recruiting the γ-tubulin ring complex (γ-TuRC) to pre-existing microtubules and nucleating branching microtubules. Here, we elucidate the molecular architecture of augmin by single particle cryo-electron microscopy (cryo-EM), computational methods, and crosslinking mass spectrometry (CLMS). Augmin's highly flexible structure contains a V-shaped head and a filamentous tail, with the head existing in either extended or contracted conformational states. Our work highlights how cryo-EM, complemented by computational advances and CLMS, can elucidate the structure of a challenging protein complex and provides insights into the function of augmin in mediating microtubule branching nucleation.
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Affiliation(s)
- Clinton A Gabel
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
- Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA
| | - Zhuang Li
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
- Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA
| | - Andrew G DeMarco
- Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Ziguo Zhang
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Jing Yang
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Mark C Hall
- Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - David Barford
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Leifu Chang
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA.
- Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA.
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15
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Oh W, Wu TT, Jeong SY, You HJ, Lee JH. CtIP Regulates Mitotic Spindle Assembly by Modulating the TPX2-Aurora A Signaling Axis. Cells 2022; 11:cells11182814. [PMID: 36139389 PMCID: PMC9497199 DOI: 10.3390/cells11182814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 09/07/2022] [Accepted: 09/07/2022] [Indexed: 11/16/2022] Open
Abstract
CtBP-interacting protein (CtIP) plays a critical role in controlling the homologous recombination-mediated DNA double-stranded break (DSB) repair pathway through DNA end resection, and recent studies suggest that it also plays a role in mitosis. However, the mechanism by which CtIP contributes to mitosis regulation remains elusive. Here, we show that depletion of CtIP leads to a delay in anaphase progression resulting in misaligned chromosomes, an aberrant number of centrosomes, and defects in chromosome segregation. Additionally, we demonstrate that CtIP binds and colocalizes with Targeting protein for Xklp2 (TPX2) during mitosis to regulate the recruitment of TPX2 to the spindle poles. Furthermore, depletion of CtIP resulted in both a lower concentration of Aurora A, its downstream target, and very low microtubule intensity at the spindle poles, suggesting an important role for the CtIP-TPX2-Auroa A complex in microtubule dynamics at the centrosomal spindles. Our findings reveal a novel function of CtIP in regulating spindle dynamics through interactions with TPX2 and indicate that CtIP is involved in the proper execution of the mitotic program, where deregulation may lead to chromosomal instability.
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Affiliation(s)
- Wonkyung Oh
- Laboratory of Genomic Instability and Cancer Therapeutics, Cancer Mutation Research Center, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
| | - Ting Ting Wu
- Laboratory of Genomic Instability and Cancer Therapeutics, Cancer Mutation Research Center, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
| | - Seo-Yeon Jeong
- Laboratory of Genomic Instability and Cancer Therapeutics, Cancer Mutation Research Center, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
| | - Ho Jin You
- Laboratory of Genomic Instability and Cancer Therapeutics, Cancer Mutation Research Center, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
- Department of Pharmacology, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
| | - Jung-Hee Lee
- Laboratory of Genomic Instability and Cancer Therapeutics, Cancer Mutation Research Center, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
- Department of Cellular and Molecular Medicine, School of Medicine, Chosun University, 375 Seosuk-dong, Gwangju 61452, Korea
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16
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Wolff ID, Hollis JA, Wignall SM. Acentrosomal spindle assembly and maintenance in Caenorhabditis elegans oocytes requires a kinesin-12 nonmotor microtubule interaction domain. Mol Biol Cell 2022; 33:ar71. [PMID: 35594182 PMCID: PMC9635285 DOI: 10.1091/mbc.e22-05-0153] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
During the meiotic divisions in oocytes, microtubules are sorted and organized by motor proteins to generate a bipolar spindle in the absence of centrosomes. In most organisms, kinesin-5 family members crosslink and slide microtubules to generate outward force that promotes acentrosomal spindle bipolarity. However, the mechanistic basis for how other kinesin families act on acentrosomal spindles has not been explored. We investigated this question in Caenorhabditis elegans oocytes, where kinesin-5 is not required to generate outward force and the kinesin-12 family motor KLP-18 instead performs this function. Here we use a combination of in vitro biochemical assays and in vivo mutant analysis to provide insight into the mechanism by which KLP-18 promotes acentrosomal spindle assembly. We identify a microtubule binding site on the C-terminal stalk of KLP-18 and demonstrate that a direct interaction between the KLP-18 stalk and its adaptor protein MESP-1 activates nonmotor microtubule binding. We also provide evidence that this C-terminal domain is required for KLP-18 activity during spindle assembly and show that KLP-18 is continuously required to maintain spindle bipolarity. This study thus provides new insight into the construction and maintenance of the oocyte acentrosomal spindle as well as into kinesin-12 mechanism and regulation.
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Affiliation(s)
- Ian D Wolff
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
| | - Jeremy A Hollis
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
| | - Sarah M Wignall
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
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17
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Li C, Zhang X, Dong M, Han X. Progress on Crowding Effect in Cell-like Structures. MEMBRANES 2022; 12:593. [PMID: 35736300 PMCID: PMC9228500 DOI: 10.3390/membranes12060593] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 05/27/2022] [Accepted: 05/30/2022] [Indexed: 12/10/2022]
Abstract
Several biological macromolecules, such as proteins, nucleic acids, and polysaccharides, occupy about 30% of the space in cells, resulting in a crowded macromolecule environment. The crowding effect within cells exerts an impact on the functions of biological components, the assembly behavior of biomacromolecules, and the thermodynamics and kinetics of metabolic reactions. Cell-like structures provide confined and independent compartments for studying the working mechanisms of cells, which can be used to study the physiological functions arising from the crowding effect of macromolecules in cells. This article mainly summarizes the progress of research on the macromolecular crowding effects in cell-like structures. It includes the effects of this crowding on actin assembly behavior, tubulin aggregation behavior, and gene expression. The challenges and future trends in this field are presented at the end of the paper.
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Affiliation(s)
- Chao Li
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin 150001, China; (C.L.); (X.Z.)
| | - Xiangxiang Zhang
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin 150001, China; (C.L.); (X.Z.)
| | - Mingdong Dong
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Xiaojun Han
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin 150001, China; (C.L.); (X.Z.)
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18
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Abstract
In contrast to well-studied fungal and animal cells, plant cells assemble bipolar spindles that exhibit a great deal of plasticity in the absence of structurally defined microtubule-organizing centers like the centrosome. While plants employ some evolutionarily conserved proteins to regulate spindle morphogenesis and remodeling, many essential spindle assembly factors found in vertebrates are either missing or not required for producing the plant bipolar microtubule array. Plants also produce proteins distantly related to their fungal and animal counterparts to regulate critical events such as the spindle assembly checkpoint. Plant spindle assembly initiates with microtubule nucleation on the nuclear envelope followed by bipolarization into the prophase spindle. After nuclear envelope breakdown, kinetochore fibers are assembled and unified into the spindle apparatus with convergent poles. Of note, compared to fungal and animal systems, relatively little is known about how plant cells remodel the spindle microtubule array during anaphase. Uncovering mitotic functions of novel proteins for spindle assembly in plants will illuminate both common and divergent mechanisms employed by different eukaryotic organisms to segregate genetic materials.
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Affiliation(s)
- Bo Liu
- Department of Plant Biology, University of California, Davis, California, USA; ,
| | - Yuh-Ru Julie Lee
- Department of Plant Biology, University of California, Davis, California, USA; ,
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19
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He Y, Peng L, Li J, Li Q, Chu Y, Lin Q, Rui R, Ju S. TPX2 deficiency leads to spindle abnormity and meiotic impairment in porcine oocytes. Theriogenology 2022; 187:164-172. [DOI: 10.1016/j.theriogenology.2022.04.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 04/28/2022] [Accepted: 04/30/2022] [Indexed: 10/18/2022]
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20
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A morphological study of adipose-derived stem cell sheets created with temperature-responsive culture dishes using scanning electron microscopy. Med Mol Morphol 2022; 55:187-198. [PMID: 35449367 DOI: 10.1007/s00795-022-00319-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 03/22/2022] [Indexed: 10/18/2022]
Abstract
Adipose-derived stem cell (ADSC) sheets have potential to be effective in various therapies. In this study, we first demonstrated that a cell sheet composed of human ADSCs could be created using a new temperature-responsive culture dish from the DIC Corporation. The dish can cause detachment of adherent cells due to temperature changes, but a few morphological analyses have evaluated the presence or absence of damage on the detached surface of cell sheet. To characterize our ADSC sheet, we tried to observe the surface of ADSC sheets with scanning electron microscope (SEM) using the ionic liquid, which enables the rapid preparation of samples. No damage was found on the surface of the ADSC sheets on the side that had been in contact with the surface of the culture dishes. In addition, when the transcriptomes of the harvested cell sheets were compared with those of monolayer cultures, no up-regulation of cell death related genes were detected. These results propose that the detachment from temperature-responsive culture dish causes no serious damage on the prepared ADSC sheet. It is also suggested that the SEM with ionic liquids is a useful and rapid method for the analysis of ADSC sheets for therapy.
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21
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Safari MS, King MR, Brangwynne CP, Petry S. Interaction of spindle assembly factor TPX2 with importins-α/β inhibits protein phase separation. J Biol Chem 2021; 297:100998. [PMID: 34302807 PMCID: PMC8390506 DOI: 10.1016/j.jbc.2021.100998] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 07/12/2021] [Accepted: 07/20/2021] [Indexed: 12/30/2022] Open
Abstract
The microtubule-based mitotic spindle is responsible for equally partitioning the genome during each cell division, and its assembly is executed via several microtubule nucleation pathways. Targeting Protein for XKlp2 (TPX2) stimulates the branching microtubule nucleation pathway, where new microtubules are nucleated from preexisting ones within mitotic or meiotic spindles. TPX2, like other spindle assembly factors, is sequestered by binding to nuclear importins-α/β until the onset of mitosis, yet the molecular nature of this regulation remains unclear. Here we demonstrate that TPX2 interacts with importins-α/β with nanomolar affinity in a 1:1:1 monodispersed trimer. We also identify a new nuclear localization sequence in TPX2 that contributes to its high-affinity interaction with importin-α. In addition, we establish that TPX2 interacts with importin-β via dispersed, weak interactions. We show that interactions of both importin-α and -β with TPX2 inhibit its ability to undergo phase separation, which was recently shown to enhance the kinetics of branching microtubule nucleation. In summary, our study informs how importins regulate TPX2 to facilitate spindle assembly, and provides novel insight into the functional regulation of protein phase separation.
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Affiliation(s)
- Mohammad S Safari
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Matthew R King
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, USA; Howard Hughes Medical Institute, Princeton University, Princeton, New Jersey, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA.
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22
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The Cytoskeleton and Its Roles in Self-Organization Phenomena: Insights from Xenopus Egg Extracts. Cells 2021; 10:cells10092197. [PMID: 34571847 PMCID: PMC8465277 DOI: 10.3390/cells10092197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/18/2021] [Accepted: 08/21/2021] [Indexed: 01/11/2023] Open
Abstract
Self-organization of and by the cytoskeleton is central to the biology of the cell. Since their introduction in the early 1980s, cytoplasmic extracts derived from the eggs of the African clawed-frog, Xenopus laevis, have flourished as a major experimental system to study the various facets of cytoskeleton-dependent self-organization. Over the years, the many investigations that have used these extracts uniquely benefited from their simplified cell cycle, large experimental volumes, biochemical tractability and cell-free nature. Here, we review the contributions of egg extracts to our understanding of the cytoplasmic aspects of self-organization by the microtubule and the actomyosin cytoskeletons as well as the importance of cytoskeletal filaments in organizing nuclear structure and function.
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23
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Novitasari D, Jenie RI, Kato JY, Meiyanto E. The integrative bioinformatic analysis deciphers the predicted molecular target gene and pathway from curcumin derivative CCA-1.1 against triple-negative breast cancer (TNBC). J Egypt Natl Canc Inst 2021; 33:19. [PMID: 34337682 DOI: 10.1186/s43046-021-00077-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 07/16/2021] [Indexed: 03/20/2023] Open
Abstract
BACKGROUND The poor outcomes from triple-negative breast cancer (TNBC) therapy are mainly because of TNBC cells' heterogeneity, and chemotherapy is the current approach in TNBC treatment. A previous study reported that CCA-1.1, the alcohol-derivative from monocarbonyl PGV-1, exhibits anticancer activities against several cancer cells, as well as in TNBC. This time, we utilized an integrative bioinformatics approach to identify potential biomarkers and molecular mechanisms of CCA-1.1 in inhibiting proliferation in TNBC cells. METHODS Genomics data expression were collected through UALCAN, derived initially from TCGA-BRCA data, and selected for TNBC-only cases. We predict CCA-1.1 potential targets using SMILES-based similarity functions across six public web tools (BindingDB, DINIES, Swiss Target Prediction, Polypharmacology browser/PPB, Similarity Ensemble Approach/SEA, and TargetNet). The overlapping genes between the CCA-1.1 target and TNBC (CPTGs) were selected and used in further assessment. Gene ontology (GO) enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) network analysis were generated in WebGestalt. The protein-protein interaction (PPI) network was established in STRING-DB, and then the hub-genes were defined through Cytoscape. The hub-gene's survival analysis was processed via CTGS web tools using TCGA database. RESULTS KEGG pathway analysis pointed to cell cycle process which enriched in CCA-1.1 potential targets. We also identified nine CPTGs that are responsible in mitosis, including AURKB, PLK1, CDK1, TPX2, AURKA, KIF11, CDC7, CHEK1, and CDC25B. CONCLUSION We suggested CCA-1.1 possibly regulated cell cycle process during mitosis, which led to cell death. These findings needed to be investigated through experimental studies to reinforce scientific data of CCA-1.1 therapy against TNBC.
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Affiliation(s)
- Dhania Novitasari
- Doctoral Student in the Faculty of Pharmacy, Universitas Gadjah Mada, Yogyakarta, 55281, Indonesia.,Cancer Chemoprevention Research Center, Faculty of Pharmacy, Universitas Gadjah Mada, Yogyakarta, 55281, Indonesia
| | - Riris Istighfari Jenie
- Cancer Chemoprevention Research Center, Faculty of Pharmacy, Universitas Gadjah Mada, Yogyakarta, 55281, Indonesia.,Macromolecular Engineering Laboratory, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Universitas Gadjah Mada, Sekip Utara, Yogyakarta, 55281, Indonesia
| | - Jun-Ya Kato
- Laboratory of Tumor Cell Biology, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan
| | - Edy Meiyanto
- Cancer Chemoprevention Research Center, Faculty of Pharmacy, Universitas Gadjah Mada, Yogyakarta, 55281, Indonesia. .,Macromolecular Engineering Laboratory, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Universitas Gadjah Mada, Sekip Utara, Yogyakarta, 55281, Indonesia.
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24
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Abstract
As one of four filament types, microtubules are a core component of the cytoskeleton and are essential for cell function. Yet how microtubules are nucleated from their building blocks, the αβ-tubulin heterodimer, has remained a fundamental open question since the discovery of tubulin 50 years ago. Recent structural studies have shed light on how γ-tubulin and the γ-tubulin complex proteins (GCPs) GCP2 to GCP6 form the γ-tubulin ring complex (γ-TuRC). In parallel, functional and single-molecule studies have informed on how the γ-TuRC nucleates microtubules in real time, how this process is regulated in the cell and how it compares to other modes of nucleation. Another recent surprise has been the identification of a second essential nucleation factor, which turns out to be the well-characterized microtubule polymerase XMAP215 (also known as CKAP5, a homolog of chTOG, Stu2 and Alp14). This discovery helps to explain why the observed nucleation activity of the γ-TuRC in vitro is relatively low. Taken together, research in recent years has afforded important insight into how microtubules are made in the cell and provides a basis for an exciting era in the cytoskeleton field.
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Affiliation(s)
- Akanksha Thawani
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, Berkeley, CA 94720, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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25
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Gai Y, Cook B, Setru S, Stone HA, Petry S. Confinement size determines the architecture of Ran-induced microtubule networks. SOFT MATTER 2021; 17:5921-5931. [PMID: 34041514 PMCID: PMC8958645 DOI: 10.1039/d1sm00045d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The organization of microtubules (MTs) is critical for cells during interphase and mitosis. During mitotic spindle assembly, MTs are made and organized around chromosomes in a process regulated by RanGTP. The role of RanGTP has been explored in Xenopus egg extracts, which are not limited by a cell membrane. Here, we investigated whether cell-sized confinements affect the assembly of RanGTP-induced MT networks in Xenopus egg extracts. We used microfluidics to encapsulate extracts within monodisperse extract-in-oil droplets. Importantly, we find that the architecture of Ran-induced MT networks depends on the droplet diameter and the Ran concentration, and differs from structures formed in bulk extracts. Our results highlight that both MT nucleation and physical confinement play critical roles in determining the spatial organization of the MT cytoskeleton.
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Affiliation(s)
- Ya Gai
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Brian Cook
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
| | - Sagar Setru
- Lewis-Sigler Institute of Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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26
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Setru SU, Gouveia B, Alfaro-Aco R, Shaevitz JW, Stone HA, Petry S. A hydrodynamic instability drives protein droplet formation on microtubules to nucleate branches. NATURE PHYSICS 2021; 17:493-498. [PMID: 35211183 PMCID: PMC8865447 DOI: 10.1038/s41567-020-01141-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 11/24/2020] [Indexed: 05/23/2023]
Affiliation(s)
- Sagar U. Setru
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Bernardo Gouveia
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Raymundo Alfaro-Aco
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Joshua W. Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Howard A. Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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27
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Smertenko A, Clare SJ, Effertz K, Parish A, Ross A, Schmidt S. A guide to plant TPX2-like and WAVE-DAMPENED2-like proteins. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:1034-1045. [PMID: 33130902 PMCID: PMC8502432 DOI: 10.1093/jxb/eraa513] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 10/27/2020] [Indexed: 05/31/2023]
Abstract
TPX2 proteins were first identified in vertebrates as a key mitotic spindle assembly factor. Subsequent studies demonstrated that TPX2 is an intricate protein, with functionally and structurally distinct domains and motifs including Aurora kinase-binding, importin-binding, central microtubule-binding, and C-terminal TPX2 conserved domain, among others. The first plant TPX2-like protein, WAVE-DAMPENED2, was identified in Arabidopsis as a dominant mutation responsible for reducing the waviness of roots grown on slanted agar plates. Each plant genome encodes at least one 'canonical' protein with all TPX2 domains and a family of proteins (20 in Arabidopsis) that diversified to contain only some of the domains. Although all plant TPX2-family proteins to date bind microtubules, they function in distinct processes such as cell division, regulation of hypocotyl cell elongation by hormones and light signals, vascular development, or abiotic stress tolerance. Consequently, their expression patterns, regulation, and functions have diverged considerably. Here we summarize the current body of knowledge surrounding plant TPX2-family proteins.
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Affiliation(s)
- Andrei Smertenko
- Plant Molecular Sciences Graduate Program, Washington State University, Pullman, WA, USA
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
| | - Shaun J Clare
- Plant Molecular Sciences Graduate Program, Washington State University, Pullman, WA, USA
- Department of Crop and Soil Sciences, Washington State University, Pullman, WA, USA
| | - Karl Effertz
- Plant Molecular Sciences Graduate Program, Washington State University, Pullman, WA, USA
- Department of Crop and Soil Sciences, Washington State University, Pullman, WA, USA
| | - Alyssa Parish
- Plant Molecular Sciences Graduate Program, Washington State University, Pullman, WA, USA
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
| | - Austin Ross
- Plant Molecular Sciences Graduate Program, Washington State University, Pullman, WA, USA
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
| | - Sharol Schmidt
- Plant Molecular Sciences Graduate Program, Washington State University, Pullman, WA, USA
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
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28
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Gangadharan B, Rice LM. Nucleating a Microtubule: Put a γ-Tubulin Ring on It. Dev Cell 2020; 53:495-497. [PMID: 32516593 DOI: 10.1016/j.devcel.2020.05.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The γ-tubulin ring complex (γTuRC) is a microtubule nucleator that controls when and where new microtubules form. In this issue of Developmental Cell, Consolati et al. provide much-needed insight into the mechanism of γTuRC-mediated nucleation by determining the structure of human γTuRC and performing quantitative measurements of its activity.
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Affiliation(s)
- Binnu Gangadharan
- Department of Biophysics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Luke M Rice
- Department of Biophysics, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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29
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Wiegand T, Hyman AA. Drops and fibers - how biomolecular condensates and cytoskeletal filaments influence each other. Emerg Top Life Sci 2020; 4:247-261. [PMID: 33048111 PMCID: PMC7733666 DOI: 10.1042/etls20190174] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/16/2020] [Accepted: 09/17/2020] [Indexed: 12/13/2022]
Abstract
The cellular cytoskeleton self-organizes by specific monomer-monomer interactions resulting in the polymerization of filaments. While we have long thought about the role of polymerization in cytoskeleton formation, we have only begun to consider the role of condensation in cytoskeletal organization. In this review, we highlight how the interplay between polymerization and condensation leads to the formation of the cytoskeleton.
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Affiliation(s)
- Tina Wiegand
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
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30
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Polverino F, Naso FD, Asteriti IA, Palmerini V, Singh D, Valente D, Bird AW, Rosa A, Mapelli M, Guarguaglini G. The Aurora-A/TPX2 Axis Directs Spindle Orientation in Adherent Human Cells by Regulating NuMA and Microtubule Stability. Curr Biol 2020; 31:658-667.e5. [PMID: 33275894 DOI: 10.1016/j.cub.2020.10.096] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 09/16/2020] [Accepted: 10/30/2020] [Indexed: 12/17/2022]
Abstract
Mitotic spindle orientation is a crucial process that defines the axis of cell division, contributing to daughter cell positioning and fate, and hence to tissue morphogenesis and homeostasis.1,2 The trimeric NuMA/LGN/Gαi complex, the major determinant of spindle orientation, exerts pulling forces on the spindle poles by anchoring astral microtubules (MTs) and dynein motors to the cell cortex.3,4 Mitotic kinases contribute to correct spindle orientation by regulating nuclear mitotic apparatus protein (NuMA) localization,5-7 among which the Aurora-A centrosomal kinase regulates NuMA targeting to the cell cortex in metaphase.8,9 Aurora-A and its activator targeting protein for Xklp2 (TPX2) are frequently overexpressed in cancer,10-12 raising the question as to whether spindle orientation is among the processes downstream the Aurora-A/TPX2 signaling axis altered under pathological conditions. Here, we investigated the role of TPX2 in the Aurora-A- and NuMA-dependent spindle orientation. We show that, in cultured adherent human cells, the interaction with TPX2 is required for Aurora-A to exert this function. We also show that Aurora-A, TPX2, and NuMA are part of a complex at spindle MTs, where TPX2 acts as a platform for Aurora-A regulation of NuMA. Interestingly, excess TPX2 does not influence NuMA localization but induces a "super-alignment" of the spindle axis with respect to the substrate, although an excess of Aurora-A induces spindle misorientation. These opposite effects are both linked to altered MT stability. Overall, our results highlight the importance of TPX2 for spindle orientation and suggest that spindle orientation is differentially sensitive to unbalanced levels of Aurora-A, TPX2, or the Aurora-A/TPX2 complex.
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Affiliation(s)
- Federica Polverino
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Department of Biology and Biotechnology, Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; Department of Experimental Oncology, IEO European Institute of Oncology IRCCS, Via Adamello 16, 20141 Milan, Italy
| | - Francesco D Naso
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Department of Biology and Biotechnology, Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy
| | - Italia A Asteriti
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Department of Biology and Biotechnology, Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy
| | - Valentina Palmerini
- Department of Experimental Oncology, IEO European Institute of Oncology IRCCS, Via Adamello 16, 20141 Milan, Italy
| | - Divya Singh
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Davide Valente
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Department of Biology and Biotechnology, Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy
| | - Alexander W Bird
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Alessandro Rosa
- Center for Life Nano Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy; Department of Biology and Biotechnology "C. Darwin," Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Marina Mapelli
- Department of Experimental Oncology, IEO European Institute of Oncology IRCCS, Via Adamello 16, 20141 Milan, Italy.
| | - Giulia Guarguaglini
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Department of Biology and Biotechnology, Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy.
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31
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Liu P, Würtz M, Zupa E, Pfeffer S, Schiebel E. Microtubule nucleation: The waltz between γ-tubulin ring complex and associated proteins. Curr Opin Cell Biol 2020; 68:124-131. [PMID: 33190097 DOI: 10.1016/j.ceb.2020.10.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 09/22/2020] [Accepted: 10/08/2020] [Indexed: 12/31/2022]
Abstract
Microtubules are essential cytoskeletal elements assembled from αβ-tubulin dimers. In high eukaryotes, microtubule nucleation, the de novo assembly of a microtubule from its minus end, is initiated by the γ-tubulin ring complex (γ-TuRC). Despite many years of research, the structural and mechanistic principles of the microtubule nucleation machinery remained poorly understood. Only recently, cryoelectron microscopy studies uncovered the molecular organization and potential activation mechanisms of γ-TuRC. In vitro assays further deciphered the spatial and temporal cooperation between γ-TuRC and additional factors, for example, the augmin complex, the phase separation protein TPX2, and the microtubule polymerase XMAP215. These breakthroughs deepen our understanding of microtubule nucleation mechanisms and will link the assembly of individual microtubules to the organization of cellular microtubule networks.
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Affiliation(s)
- Peng Liu
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120, Heidelberg, Germany.
| | - Martin Würtz
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120, Heidelberg, Germany
| | - Erik Zupa
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120, Heidelberg, Germany
| | - Stefan Pfeffer
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120, Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120, Heidelberg, Germany
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32
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Levine TP. Structural bioinformatics predicts that the Retinitis Pigmentosa-28 protein of unknown function FAM161A is a homologue of the microtubule nucleation factor Tpx2. F1000Res 2020; 9:1052. [PMID: 33093951 PMCID: PMC7551519 DOI: 10.12688/f1000research.25870.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/13/2020] [Indexed: 11/20/2022] Open
Abstract
Background: FAM161A is a microtubule-associated protein conserved widely across eukaryotes, which is mutated in the inherited blinding disease Retinitis Pigmentosa-28. FAM161A is also a centrosomal protein, being a core component of a complex that forms an internal skeleton of centrioles. Despite these observations about the importance of FAM161A, current techniques used to examine its sequence reveal no homologies to other proteins. Methods: Sequence profiles derived from multiple sequence alignments of FAM161A homologues were constructed by PSI-BLAST and HHblits, and then used by the profile-profile search tool HHsearch, implemented online as HHpred, to identify homologues. These in turn were used to create profiles for reverse searches and pair-wise searches. Multiple sequence alignments were also used to identify amino acid usage in functional elements. Results: FAM161A has a single homologue: the targeting protein for
Xenopus kinesin-like protein-2 (Tpx2), which is a strong hit across more than 200 residues. Tpx2 is also a microtubule-associated protein, and it has been shown previously by a cryo-EM molecular structure to nucleate microtubules through two small elements: an extended loop and a short helix. The homology between FAM161A and Tpx2 includes these elements, as FAM161A has three copies of the loop, and one helix that has many, but not all, properties of the one in Tpx2. Conclusions: FAM161A and its homologues are predicted to be a previously unknown variant of Tpx2, and hence bind microtubules in the same way. This prediction allows precise, testable molecular models to be made of FAM161A-microtubule complexes.
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Affiliation(s)
- Timothy P Levine
- UCL Institute of Ophthalmology, University College London, London, EC1V 9EL, UK
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33
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A Pushing Mechanism for Microtubule Aster Positioning in a Large Cell Type. Cell Rep 2020; 33:108213. [DOI: 10.1016/j.celrep.2020.108213] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 01/12/2020] [Accepted: 09/10/2020] [Indexed: 12/15/2022] Open
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Smertenko T, Turner G, Fahy D, Brew-Appiah RAT, Alfaro-Aco R, de Almeida Engler J, Sanguinet KA, Smertenko A. Brachypodium distachyon MAP20 functions in metaxylem pit development and contributes to drought recovery. THE NEW PHYTOLOGIST 2020; 227:1681-1695. [PMID: 31863702 DOI: 10.1111/nph.16383] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 12/07/2019] [Indexed: 06/10/2023]
Abstract
Pits are regions in the cell walls of plant tracheary elements that lack secondary walls. Each pit consists of a space within the secondary wall called a pit chamber, and a modified primary wall called the pit membrane. The pit membrane facilitates transport of solutions between vessel cells and restricts embolisms during drought. Here we analyzed the role of an angiosperm-specific TPX2-like microtubule protein MAP20 in pit formation using Brachypodium distachyon as a model system. Live cell imaging was used to analyze the interaction of MAP20 with microtubules and the impact of MAP20 on microtubule dynamics. MAP20-specific antibody was used to study expression and localization of MAP20 in different cell types during vascular bundle development. We used an artificial microRNAs (amiRNA) knockdown approach to determine the function of MAP20. MAP20 is expressed during the late stages of vascular bundle development and localizes around forming pits and under secondary cell wall thickenings in metaxylem cells. MAP20 suppresses microtubule depolymerization; however, unlike the animal TPX2 counterpart, MAP20 does not cooperate with the γ-tubulin ring complex in microtubule nucleation. Knockdown of MAP20 causes bigger pits, thinner pit membranes, perturbed vasculature development, lower reproductive potential and higher drought susceptibility. We conclude that MAP20 may contribute to drought adaptation by modulating pit size and pit membrane thickness in metaxylem.
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Affiliation(s)
- Tetyana Smertenko
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Glenn Turner
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Deirdre Fahy
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Rhoda A T Brew-Appiah
- Department of Crop and Soil Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Raymundo Alfaro-Aco
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ, 08544, USA
| | - Janice de Almeida Engler
- Institut Sophia Agrobiotech, Institut National de la Recherche Agronomique, Université Côte d'Azur, Centre National de la Recherche Scientifique, 06903, Sophia-Antipolis, France
| | - Karen A Sanguinet
- Department of Crop and Soil Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Andrei Smertenko
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
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35
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Guilloux G, Gibeaux R. Mechanisms of spindle assembly and size control. Biol Cell 2020; 112:369-382. [PMID: 32762076 DOI: 10.1111/boc.202000065] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/03/2020] [Accepted: 08/03/2020] [Indexed: 01/09/2023]
Abstract
The spindle is crucial for cell division by allowing the faithful segregation of replicated chromosomes to daughter cells. Proper segregation is ensured only if microtubules (MTs) and hundreds of other associated factors interact to assemble this complex structure with the appropriate architecture and size. In this review, we describe the latest view of spindle organisation as well as the molecular gradients and mechanisms underlying MT nucleation and spindle assembly. We then discuss the overlapping physical and molecular constraints that dictate spindle morphology, concluding with a focus on spindle size regulation.
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Affiliation(s)
- Gabriel Guilloux
- Univ Rennes, CNRS, IGDR [(Institute of Genetics and Development of Rennes)] - UMR 6290, F-35000 Rennes, France
| | - Romain Gibeaux
- Univ Rennes, CNRS, IGDR [(Institute of Genetics and Development of Rennes)] - UMR 6290, F-35000 Rennes, France
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36
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Thawani A, Rale MJ, Coudray N, Bhabha G, Stone HA, Shaevitz JW, Petry S. The transition state and regulation of γ-TuRC-mediated microtubule nucleation revealed by single molecule microscopy. eLife 2020; 9:e54253. [PMID: 32538784 PMCID: PMC7338055 DOI: 10.7554/elife.54253] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 06/15/2020] [Indexed: 12/31/2022] Open
Abstract
Determining how microtubules (MTs) are nucleated is essential for understanding how the cytoskeleton assembles. While the MT nucleator, γ-tubulin ring complex (γ-TuRC) has been identified, precisely how γ-TuRC nucleates a MT remains poorly understood. Here, we developed a single molecule assay to directly visualize nucleation of a MT from purified Xenopus laevis γ-TuRC. We reveal a high γ-/αβ-tubulin affinity, which facilitates assembly of a MT from γ-TuRC. Whereas spontaneous nucleation requires assembly of 8 αβ-tubulins, nucleation from γ-TuRC occurs efficiently with a cooperativity of 4 αβ-tubulin dimers. This is distinct from pre-assembled MT seeds, where a single dimer is sufficient to initiate growth. A computational model predicts our kinetic measurements and reveals the rate-limiting transition where laterally associated αβ-tubulins drive γ-TuRC into a closed conformation. NME7, TPX2, and the putative activation domain of CDK5RAP2 h γ-TuRC-mediated nucleation, while XMAP215 drastically increases the nucleation efficiency by strengthening the longitudinal γ-/αβ-tubulin interaction.
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Affiliation(s)
- Akanksha Thawani
- Department of Chemical and Biological Engineering, Princeton UniversityPrincetonUnited States
| | - Michael J Rale
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
| | - Nicolas Coudray
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Gira Bhabha
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton UniversityPrincetonUnited States
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative GenomicsPrincetonUnited States
- Department of Physics, Princeton UniversityPrincetonUnited States
| | - Sabine Petry
- Department of Molecular Biology, Princeton UniversityPrincetonUnited States
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37
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Consolati T, Locke J, Roostalu J, Chen ZA, Gannon J, Asthana J, Lim WM, Martino F, Cvetkovic MA, Rappsilber J, Costa A, Surrey T. Microtubule Nucleation Properties of Single Human γTuRCs Explained by Their Cryo-EM Structure. Dev Cell 2020; 53:603-617.e8. [PMID: 32433913 PMCID: PMC7280788 DOI: 10.1016/j.devcel.2020.04.019] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 03/21/2020] [Accepted: 04/27/2020] [Indexed: 12/13/2022]
Abstract
The γ-tubulin ring complex (γTuRC) is the major microtubule nucleator in cells. The mechanism of its regulation is not understood. We purified human γTuRC and measured its nucleation properties in a total internal reflection fluorescence (TIRF) microscopy-based real-time nucleation assay. We find that γTuRC stably caps the minus ends of microtubules that it nucleates stochastically. Nucleation is inefficient compared with microtubule elongation. The 4 Å resolution cryoelectron microscopy (cryo-EM) structure of γTuRC, combined with crosslinking mass spectrometry analysis, reveals an asymmetric conformation with only part of the complex in a "closed" conformation matching the microtubule geometry. Actin in the core of the complex, and MZT2 at the outer perimeter of the closed part of γTuRC appear to stabilize the closed conformation. The opposite side of γTuRC is in an "open," nucleation-incompetent conformation, leading to a structural asymmetry explaining the low nucleation efficiency of purified human γTuRC. Our data suggest possible regulatory mechanisms for microtubule nucleation by γTuRC closure.
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Affiliation(s)
- Tanja Consolati
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Dr Aiguader 88, 08003 Barcelona, Spain
| | - Julia Locke
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | | | - Zhuo Angel Chen
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany; Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| | - Julian Gannon
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Jayant Asthana
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Dr Aiguader 88, 08003 Barcelona, Spain
| | - Wei Ming Lim
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Dr Aiguader 88, 08003 Barcelona, Spain
| | | | | | - Juri Rappsilber
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany; Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| | - Alessandro Costa
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
| | - Thomas Surrey
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Dr Aiguader 88, 08003 Barcelona, Spain; ICREA, Passeig de Lluis Companys 23, 08010 Barcelona, Spain.
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38
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Sosunov A, Wu X, McGovern R, Mikell C, McKhann GM, Goldman JE. Abnormal mitosis in reactive astrocytes. Acta Neuropathol Commun 2020; 8:47. [PMID: 32293551 PMCID: PMC7158149 DOI: 10.1186/s40478-020-00919-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/17/2020] [Indexed: 12/21/2022] Open
Abstract
Although abnormal mitosis with disarranged metaphase chromosomes or many micronuclei in astrocytes (named "Alzheimer I type astrocytes" and later "Creutzfeldt-Peters cells") have been known for nearly 100 years, the origin and mechanisms of this pathology remain elusive. In experimental brain insults in rats, we show that abnormal mitoses that are not followed by cytokinesis are typical for reactive astrocytes. The pathology originates due to the inability of the cells to form normal mitotic spindles with subsequent metaphase chromosome congression, which, in turn may be due to shape constraints aggravated by cellular enlargement and to the accumulation of large amounts of cytosolic proteins. Many astrocytes escape from arrested mitosis by producing micronuclei. These polyploid astrocytes can survive for long periods of time and enter into new cell cycles.
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Affiliation(s)
- Alexander Sosunov
- Department of Neurosurgery, Columbia University, 630 W. 168th St, P&S 15-405, New York, NY 10032 USA
| | - Xiaoping Wu
- Department of Neurosurgery, Columbia University, 630 W. 168th St, P&S 15-405, New York, NY 10032 USA
| | - Robert McGovern
- Department of Neurosurgery, University of Minnesota, Minneapolis, MN 55455 USA
| | - Charles Mikell
- Department of Neurosurgery, Stony Brook University School of Medicine, Stony Brook, NY USA
| | - Guy M. McKhann
- Department of Neurosurgery, Columbia University, 630 W. 168th St, P&S 15-405, New York, NY 10032 USA
| | - James E. Goldman
- Pathology & Cell Biology, Columbia University, New York, NY 10032 USA
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39
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Meaders JL, Burgess DR. Microtubule-Based Mechanisms of Pronuclear Positioning. Cells 2020; 9:E505. [PMID: 32102180 PMCID: PMC7072840 DOI: 10.3390/cells9020505] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 02/18/2020] [Accepted: 02/19/2020] [Indexed: 12/22/2022] Open
Abstract
The zygote is defined as a diploid cell resulting from the fusion of two haploid gametes. Union of haploid male and female pronuclei in many animals occurs through rearrangements of the microtubule cytoskeleton into a radial array of microtubules known as the sperm aster. The sperm aster nucleates from paternally-derived centrioles attached to the male pronucleus after fertilization. Nematode, echinoderm, and amphibian eggs have proven as invaluable models to investigate the biophysical principles for how the sperm aster unites male and female pronuclei with precise spatial and temporal regulation. In this review, we compare these model organisms, discussing the dynamics of sperm aster formation and the different force generating mechanism for sperm aster and pronuclear migration. Finally, we provide new mechanistic insights for how sperm aster growth may influence sperm aster positioning.
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Affiliation(s)
| | - David R Burgess
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
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40
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Naso FD, Sterbini V, Crecca E, Asteriti IA, Russo AD, Giubettini M, Cundari E, Lindon C, Rosa A, Guarguaglini G. Excess TPX2 Interferes with Microtubule Disassembly and Nuclei Reformation at Mitotic Exit. Cells 2020; 9:E374. [PMID: 32041138 PMCID: PMC7072206 DOI: 10.3390/cells9020374] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/24/2020] [Accepted: 01/29/2020] [Indexed: 12/15/2022] Open
Abstract
The microtubule-associated protein TPX2 is a key mitotic regulator that contributes through distinct pathways to spindle assembly. A well-characterised function of TPX2 is the activation, stabilisation and spindle localisation of the Aurora-A kinase. High levels of TPX2 are reported in tumours and the effects of its overexpression have been investigated in cancer cell lines, while little is known in non-transformed cells. Here we studied TPX2 overexpression in hTERT RPE-1 cells, using either the full length TPX2 or a truncated form unable to bind Aurora-A, to identify effects that are dependent-or independent-on its interaction with the kinase. We observe significant defects in mitotic spindle assembly and progression through mitosis that are more severe when overexpressed TPX2 is able to interact with Aurora-A. Furthermore, we describe a peculiar, and Aurora-A-interaction-independent, phenotype in telophase cells, with aberrantly stable microtubules interfering with nuclear reconstitution and the assembly of a continuous lamin B1 network, resulting in daughter cells displaying doughnut-shaped nuclei. Our results using non-transformed cells thus reveal a previously uncharacterised consequence of abnormally high TPX2 levels on the correct microtubule cytoskeleton remodelling and G1 nuclei reformation, at the mitosis-to-interphase transition.
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Affiliation(s)
- Francesco D. Naso
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
| | - Valentina Sterbini
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
| | - Elena Crecca
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
| | - Italia A. Asteriti
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
| | - Alessandra D. Russo
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
| | - Maria Giubettini
- CrestOptics S.p.A., Via di Torre Rossa 66, 00165 Rome, Italy;
- Center for Life Nano Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy;
| | - Enrico Cundari
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
| | - Catherine Lindon
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK;
| | - Alessandro Rosa
- Center for Life Nano Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy;
- Department of Biology and Biotechnology “C. Darwin”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Giulia Guarguaglini
- Institute of Molecular Biology and Pathology, National Research Council of Italy, c/o Sapienza University of Rome, Via degli Apuli 4, 00185 Rome, Italy; (F.D.N.); (V.S.); (E.C.); (I.A.A.); (A.D.R.); (E.C.)
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41
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Alfaro-Aco R, Thawani A, Petry S. Biochemical reconstitution of branching microtubule nucleation. eLife 2020; 9:e49797. [PMID: 31933480 PMCID: PMC6959992 DOI: 10.7554/elife.49797] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Accepted: 12/12/2019] [Indexed: 12/31/2022] Open
Abstract
Microtubules are nucleated from specific locations at precise times in the cell cycle. However, the factors that constitute these microtubule nucleation pathways and their mode of action still need to be identified. Using purified Xenopus laevis proteins we biochemically reconstitute branching microtubule nucleation, which is critical for chromosome segregation. We found that besides the microtubule nucleator gamma-tubulin ring complex (γ-TuRC), the branching effectors augmin and TPX2 are required to efficiently nucleate microtubules from pre-existing microtubules. TPX2 has the unexpected capacity to directly recruit γ-TuRC as well as augmin, which in turn targets more γ-TuRC along the microtubule lattice. TPX2 and augmin enable γ-TuRC-dependent microtubule nucleation at preferred branching angles of less than 90 degrees from regularly-spaced patches along microtubules. This work provides a blueprint for other microtubule nucleation pathways and helps explain how microtubules are generated in the spindle.
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Affiliation(s)
| | - Akanksha Thawani
- Department of Chemical and Biological EngineeringPrinceton UniversityPrincetonUnited States
| | - Sabine Petry
- Department of Molecular BiologyPrinceton UniversityPrincetonUnited States
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King MR, Petry S. Phase separation of TPX2 enhances and spatially coordinates microtubule nucleation. Nat Commun 2020; 11:270. [PMID: 31937751 PMCID: PMC6959270 DOI: 10.1038/s41467-019-14087-0] [Citation(s) in RCA: 121] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 12/10/2019] [Indexed: 12/14/2022] Open
Abstract
Phase separation of substrates and effectors is proposed to enhance biological reaction rates and efficiency. Targeting protein for Xklp2 (TPX2) is an effector of branching microtubule nucleation in spindles and functions with the substrate tubulin by an unknown mechanism. Here we show that TPX2 phase separates into a co-condensate with tubulin, which mediates microtubule nucleation in vitro and in isolated cytosol. TPX2-tubulin co-condensation preferentially occurs on pre-existing microtubules, the site of branching microtubule nucleation, at the endogenous and physiologically relevant concentration of TPX2. Truncation and chimera versions of TPX2 suggest that TPX2-tubulin co-condensation enhances the efficiency of TPX2-mediated branching microtubule nucleation. Finally, the known inhibitor of TPX2, the importin-α/β heterodimer, regulates TPX2 condensation in vitro and, consequently, branching microtubule nucleation activity in isolated cytosol. Our study demonstrates how regulated phase separation can simultaneously enhance reaction efficiency and spatially coordinate microtubule nucleation, which may facilitate rapid and accurate spindle formation.
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Affiliation(s)
- Matthew R King
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, 08544, USA
- Department of Biomedical Engineering, Washington University, Brauer Hall, One Brookings Drive, Saint Louis, Missouri, 63130, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, 08544, USA.
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43
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Alfaro-Aco R, Thawani A, Petry S. Biochemical reconstitution of branching microtubule nucleation. eLife 2020. [PMID: 31933480 DOI: 10.1101/700047v1.full] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023] Open
Abstract
Microtubules are nucleated from specific locations at precise times in the cell cycle. However, the factors that constitute these microtubule nucleation pathways and their mode of action still need to be identified. Using purified Xenopus laevis proteins we biochemically reconstitute branching microtubule nucleation, which is critical for chromosome segregation. We found that besides the microtubule nucleator gamma-tubulin ring complex (γ-TuRC), the branching effectors augmin and TPX2 are required to efficiently nucleate microtubules from pre-existing microtubules. TPX2 has the unexpected capacity to directly recruit γ-TuRC as well as augmin, which in turn targets more γ-TuRC along the microtubule lattice. TPX2 and augmin enable γ-TuRC-dependent microtubule nucleation at preferred branching angles of less than 90 degrees from regularly-spaced patches along microtubules. This work provides a blueprint for other microtubule nucleation pathways and helps explain how microtubules are generated in the spindle.
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Affiliation(s)
- Raymundo Alfaro-Aco
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Akanksha Thawani
- Department of Chemical and Biological Engineering, Princeton University, Princeton, United States
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, United States
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44
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Vargas-Hurtado D, Brault JB, Piolot T, Leconte L, Da Silva N, Pennetier C, Baffet A, Marthiens V, Basto R. Differences in Mitotic Spindle Architecture in Mammalian Neural Stem Cells Influence Mitotic Accuracy during Brain Development. Curr Biol 2019; 29:2993-3005.e9. [DOI: 10.1016/j.cub.2019.07.061] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 05/31/2019] [Accepted: 07/19/2019] [Indexed: 12/16/2022]
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45
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Verma V, Maresca TJ. Direct observation of branching MT nucleation in living animal cells. J Cell Biol 2019; 218:2829-2840. [PMID: 31340987 PMCID: PMC6719462 DOI: 10.1083/jcb.201904114] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 06/07/2019] [Accepted: 07/01/2019] [Indexed: 02/07/2023] Open
Abstract
Branching microtubule nucleation by its molecular mediators has never been directly observed in animal cells. By imaging augmin, γ-TuRC, and microtubules with high spatiotemporal resolution, Verma and Maresca quantitatively define the sequential steps of augmin-mediated branching microtubule nucleation in dividing Drosophila cells. Centrosome-mediated microtubule (MT) nucleation has been well characterized; however, numerous noncentrosomal MT nucleation mechanisms exist. The branching MT nucleation pathway envisages that the γ-tubulin ring complex (γ-TuRC) is recruited to MTs by the augmin complex to initiate nucleation of new MTs. While the pathway is well conserved at a molecular and functional level, branching MT nucleation by core constituents has never been directly observed in animal cells. Here, multicolor TIRF microscopy was applied to visualize and quantitatively define the entire process of branching MT nucleation in dividing Drosophila cells during anaphase. The steps of a stereotypical branching nucleation event entailed augmin binding to a mother MT and recruitment of γ-TuRC after 15 s, followed by nucleation 16 s later of a daughter MT at a 36° branch angle. Daughters typically remained attached throughout their ∼40-s lifetime unless the mother depolymerized past the branch point. Assembly of branched MT arrays, which did not require Drosophila TPX2, enhanced localized RhoA activation during cytokinesis.
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Affiliation(s)
- Vikash Verma
- Biology Department, University of Massachusetts, Amherst, MA
| | - Thomas J Maresca
- Biology Department, University of Massachusetts, Amherst, MA .,Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, MA
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46
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Boruc J, Deng X, Mylle E, Besbrugge N, Van Durme M, Demidov D, Tomaštíková ED, Tan TRC, Vandorpe M, Eeckhout D, Beeckman T, Nowack MK, De Jaeger G, Lin H, Liu B, Van Damme D. TPX2-LIKE PROTEIN3 Is the Primary Activator of α-Aurora Kinases and Is Essential for Embryogenesis. PLANT PHYSIOLOGY 2019; 180:1389-1405. [PMID: 31097675 PMCID: PMC6752915 DOI: 10.1104/pp.18.01515] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 04/29/2019] [Indexed: 05/08/2023]
Abstract
Aurora kinases are key regulators of mitosis. Multicellular eukaryotes generally possess two functionally diverged types of Aurora kinases. In plants, including Arabidopsis (Arabidopsis thaliana), these are termed α- and β-Auroras. As the functional specification of Aurora kinases is determined by their specific interaction partners, we initiated interactomics analyses using both Arabidopsis α-Aurora kinases (AUR1 and AUR2). Proteomics results revealed that TPX2-LIKE PROTEINS2 and 3 (TPXL2/3) prominently associated with α-Auroras, as did the conserved TPX2 to a lower degree. Like TPX2, TPXL2 and TPXL3 strongly activated the AUR1 kinase but exhibited cell-cycle-dependent localization differences on microtubule arrays. The separate functions of TPX2 and TPXL2/3 were also suggested by their different influences on AUR1 localization upon ectopic expressions. Furthermore, genetic analyses showed that TPXL3, but not TPX2 and TPXL2, acts nonredundantly to enable proper embryo development. In contrast to vertebrates, plants have an expanded TPX2 family and these family members have both redundant and unique functions. Moreover, as neither TPXL2 nor TPXL3 contains the C-terminal Kinesin-5 binding domain present in the canonical TPX2, the targeting and activity of this kinesin must be organized differently in plants.
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Affiliation(s)
- Joanna Boruc
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Xingguang Deng
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, China
| | - Evelien Mylle
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Nienke Besbrugge
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Matthias Van Durme
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Dmitri Demidov
- Leibniz Institute of Plant Genetics and Crop Plant Research, 06466 Stadt Seeland, Germany
| | - Eva Dvořák Tomaštíková
- The Czech Academy of Sciences, Institute of Experimental Botany, Centre of the Region Hana for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic
| | - Tong-Reen Connie Tan
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
| | - Michaël Vandorpe
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Dominique Eeckhout
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Tom Beeckman
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Moritz K. Nowack
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Geert De Jaeger
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
| | - Honghui Lin
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, China
| | - Bo Liu
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
| | - Daniël Van Damme
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- VIB-UGent Center for Plant Systems Biology, 9052 Ghent, Belgium
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Schmidt S, Smertenko A. Identification and characterization of the land-plant-specific microtubule nucleation factor MACET4. J Cell Sci 2019; 132:jcs232819. [PMID: 31076517 DOI: 10.1242/jcs.232819] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 05/01/2019] [Indexed: 12/23/2022] Open
Abstract
Here, we show that the embryophyte (land-plant)-specific protein MACERATOR4 (MACET4) binds microtubules in vitro and in vivo, promotes microtubule polymerization at sub-critical tubulin concentrations, decreases the lag phase in microtubule bulk polymerization assays, and colocalizes with microtubule nucleation sites. Furthermore, we find that MACET4 forms oligomers that induce aster formation in vitro in a manner that is similar to aster formation mediated by centrosomes and TPX2. MACET4 is expressed during cell division and accumulates at the microtubule nucleation regions of the plant-specific cytokinetic microtubule array, the phragmoplast. We found that MACET4 localizes to the preprophase band and the cortical division zone, but not the spindle. MACET4 appears as cytoplasmic foci in vivo and forms octamers in vitro Transient expression in tobacco leaf pavement cells results in labeling of shrinking plus- and minus-ends. MACET4 facilitates microtubule depolymerization by increasing the frequency of catastrophes in vivo and by suppressing rescues in vitro Microtubules formed in the presence of MACET4 in vitro are shorter, most likely due to the depletion of the free tubulin pool. Accordingly, MACET4 knockdown results in longer phragmoplasts. We conclude that the direct activity of MACET4 is in promoting microtubule nucleation.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Sharol Schmidt
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Andrei Smertenko
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
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48
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Thawani A, Stone HA, Shaevitz JW, Petry S. Spatiotemporal organization of branched microtubule networks. eLife 2019; 8:43890. [PMID: 31066674 PMCID: PMC6519983 DOI: 10.7554/elife.43890] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 05/07/2019] [Indexed: 11/13/2022] Open
Abstract
To understand how chromosomes are segregated, it is necessary to explain the precise spatiotemporal organization of microtubules (MTs) in the mitotic spindle. We use Xenopus egg extracts to study the nucleation and dynamics of MTs in branched networks, a process that is critical for spindle assembly. Surprisingly, new branched MTs preferentially originate near the minus-ends of pre-existing MTs. A sequential reaction model, consisting of deposition of nucleation sites on an existing MT, followed by rate-limiting nucleation of branches, reproduces the measured spatial profile of nucleation, the distribution of MT plus-ends and tubulin intensity. By regulating the availability of the branching effectors TPX2, augmin and γ-TuRC, combined with single-molecule observations, we show that first TPX2 is deposited on pre-existing MTs, followed by binding of augmin/γ-TuRC to result in the nucleation of branched MTs. In sum, regulating the localization and kinetics of nucleation effectors governs the architecture of branched MT networks.
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Affiliation(s)
- Akanksha Thawani
- Department of Chemical and Biological Engineering, Princeton University, Princeton, United States
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, United States
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, United States.,Department of Physics, Princeton University, Princeton, United States
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, United States
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49
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Ding L, Zhang S, Chen S, Zheng L, Xiao L. Effect and mechanism of lentivirus-mediated silencing of TPX2 gene on proliferation and apoptosis of human hepatoma cells. J Cell Biochem 2019; 120:8352-8358. [PMID: 30548299 DOI: 10.1002/jcb.28119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 10/31/2018] [Indexed: 01/24/2023]
Abstract
This study aimed to investigate the role and mechanism of action of targeting protein for Xklp2 (TPX2) in liver cancer, we compared TPX messenger RNA (mRNA) expression in liver cancer tissue samples and adjacent normal liver tissue samples as well as in human liver cancer cell lines and nonmalignant cell line by quantitative reverse transcription polymerase chain reaction (qRT-PCR). TPX2 gene was silenced in HepG2 cells by transfection with the lentiviral vector expressing TPX2-targeting short hairpin RNA (shRNA), and the knockdown efficiency was evaluated by RT-qPCR. Cell proliferation, apoptosis as well as protein level of c-Myc, cyclin D1, caspase-3, phosphorylated glycogen synthase kinase-3β (p-GSK-3β), and β-catenin in HepG2 cells were evaluated before and after the TPX2 knockdown. Wnt/β-catenin signaling pathway was inhibited by treatment with 20 μM of XAV-939 or activated by treatment with 20 mM of LiCl. We found that TPX2 mRNA level was significantly increased in liver cancer tissue samples and cell lines comparing to noncancerous counterparts (P < 0.05). TPX2 knockdown significantly reduces TPX2 expression (P < 0.01), cell proliferation (P < 0.05), protein level of c-Myc and cyclin D1 (P < 0.01), activation of Wnt/β-catenin signaling in HepG2 cells (P < 0.01) while increasing cell apoptosis (P < 0.01). Treatment with XAV-939 significantly reduced HepG2 cell proliferation (P < 0.05) while increasing cell apoptosis (P < 0.01). Treatment with LiCl significantly attenuated the antiproliferative and apoptosis-promoting effect of TPX2 knockdown on HepG2 cells (P < 0.05). Lentivirus-mediated silencing of TPX2 gene could inhibit proliferation and induce apoptosis in hepatoma cells by inhibiting Wnt signaling pathway and regulating cyclin and apoptosis-related proteins.
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Affiliation(s)
- Lei Ding
- Department of Infectious Diseases, Jinan Central Hospital Affiliated to Shandong University, Jinan, China
| | - Shuhong Zhang
- Department of Infectious Diseases, Jinan Central Hospital Affiliated to Shandong University, Jinan, China
| | - Shijun Chen
- Department of infectious diseases, Jinan Infectious Diseases Hospital Affiliated to Shandong University, Jinan, China
| | - Lixue Zheng
- Department of Infectious Diseases, Jinan Central Hospital Affiliated to Shandong University, Jinan, China
| | - Lianxiang Xiao
- Department of MRI Diagnosis, Shandong Medical Imaging Research Institute, Shandong University, Jinan, China
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50
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Abstract
Microtubules are major constituents of the cytoskeleton in all eukaryotic cells. They are essential for chromosome segregation during cell division, for directional intracellular transport and for building specialized cellular structures such as cilia or flagella. Their assembly has to be controlled spatially and temporally. For this, the cell uses multiprotein complexes containing γ-tubulin. γ-Tubulin has been found in two different types of complexes, γ-tubulin small complexes and γ-tubulin ring complexes. Binding to adaptors and activator proteins transforms these complexes into structural templates that drive the nucleation of new microtubules in a highly controlled manner. This review discusses recent advances on the mechanisms of assembly, recruitment and activation of γ-tubulin complexes at microtubule-organizing centres.
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Affiliation(s)
- Dorian Farache
- Centre de Biologie Intégrative, Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France
| | - Laurent Emorine
- Centre de Biologie Intégrative, Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France
| | - Laurence Haren
- Centre de Biologie Intégrative, Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France
| | - Andreas Merdes
- Centre de Biologie Intégrative, Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France
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