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Chen JS, Igarashi MG, Ren L, Hanna SM, Turner LA, McDonald NA, Beckley JR, Willet AH, Gould KL. The core spindle pole body scaffold Ppc89 links the pericentrin orthologue Pcp1 to the fission yeast spindle pole body via an evolutionarily conserved interface. Mol Biol Cell 2024; 35:ar112. [PMID: 38985524 PMCID: PMC11321043 DOI: 10.1091/mbc.e24-05-0220] [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: 05/28/2024] [Revised: 06/26/2024] [Accepted: 07/02/2024] [Indexed: 07/12/2024] Open
Abstract
Centrosomes and spindle pole bodies (SPBs) are important for mitotic spindle formation and serve as cellular signaling platforms. Although centrosomes and SPBs differ in morphology, many mechanistic insights into centrosome function have been gleaned from SPB studies. In the fission yeast Schizosaccharomyces pombe, the α-helical protein Ppc89, identified based on its interaction with the septation initiation network scaffold Sid4, comprises the SPB core. High-resolution imaging has suggested that SPB proteins assemble on the Ppc89 core during SPB duplication, but such interactions are undefined. Here, we define a connection between Ppc89 and the essential pericentrin Pcp1. Specifically, we found that a predicted third helix within Ppc89 binds the Pcp1 pericentrin-AKAP450 centrosomal targeting (PACT) domain complexed with calmodulin. Ppc89 helix 3 contains similarity to present in the N-terminus of Cep57 (PINC) motifs found in the centrosomal proteins fly SAS-6 and human Cep57 and also to the S. cerevisiae SPB protein Spc42. These motifs bind pericentrin-calmodulin complexes and AlphaFold2 models suggest a homologous complex assembles in all four organisms. Mutational analysis of the S. pombe complex supports the importance of Ppc89-Pcp1 binding interface in vivo. Our studies provide insight into the core architecture of the S. pombe SPB and suggest an evolutionarily conserved mechanism of scaffolding pericentrin-calmodulin complexes for mitotic spindle formation.
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Affiliation(s)
- Jun-Song Chen
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Maya G. Igarashi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Liping Ren
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Sarah M. Hanna
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Lesley A. Turner
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Nathan A. McDonald
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Janel R. Beckley
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Alaina H. Willet
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
| | - Kathleen L. Gould
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37240
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Wildner C, Mehta GD, Ball DA, Karpova TS, Koeppl H. Bayesian analysis dissects kinetic modulation during non-stationary gene expression. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.20.545522. [PMID: 37503023 PMCID: PMC10370195 DOI: 10.1101/2023.06.20.545522] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Labelling of nascent stem loops with fluorescent proteins has fostered the visualization of transcription in living cells. Quantitative analysis of recorded fluorescence traces can shed light on kinetic transcription parameters and regulatory mechanisms. However, existing methods typically focus on steady state dynamics. Here, we combine a stochastic process transcription model with a hierarchical Bayesian method to infer global as well locally shared parameters for groups of cells and recover unobserved quantities such as initiation times and polymerase loading of the gene. We apply our approach to the cyclic response of the yeast CUP1 locus to heavy metal stress. Within the previously described slow cycle of transcriptional activity on the scale of minutes, we discover fast time-modulated bursting on the scale of seconds. Model comparison suggests that slow oscillations of transcriptional output are regulated by the amplitude of the bursts. Several polymerases may initiate during a burst.
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Affiliation(s)
- Christian Wildner
- Centre for Synthetic Biology, Technische Universität Darmstadt, Darmstadt, 64283, Germany
| | - Gunjan D. Mehta
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana-502285, India
| | - David A. Ball
- National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Tatiana S. Karpova
- National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Heinz Koeppl
- Centre for Synthetic Biology, Technische Universität Darmstadt, Darmstadt, 64283, Germany
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3
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Gräf R, Grafe M, Meyer I, Mitic K, Pitzen V. The Dictyostelium Centrosome. Cells 2021; 10:cells10102657. [PMID: 34685637 PMCID: PMC8534566 DOI: 10.3390/cells10102657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 10/01/2021] [Accepted: 10/02/2021] [Indexed: 12/13/2022] Open
Abstract
The centrosome of Dictyostelium amoebae contains no centrioles and consists of a cylindrical layered core structure surrounded by a corona harboring microtubule-nucleating γ-tubulin complexes. It is the major centrosomal model beyond animals and yeasts. Proteomics, protein interaction studies by BioID and superresolution microscopy methods led to considerable progress in our understanding of the composition, structure and function of this centrosome type. We discuss all currently known components of the Dictyostelium centrosome in comparison to other centrosomes of animals and yeasts.
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Brilot AF, Lyon AS, Zelter A, Viswanath S, Maxwell A, MacCoss MJ, Muller EG, Sali A, Davis TN, Agard DA. CM1-driven assembly and activation of yeast γ-tubulin small complex underlies microtubule nucleation. eLife 2021; 10:e65168. [PMID: 33949948 PMCID: PMC8099430 DOI: 10.7554/elife.65168] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/12/2021] [Indexed: 01/08/2023] Open
Abstract
Microtubule (MT) nucleation is regulated by the γ-tubulin ring complex (γTuRC), conserved from yeast to humans. In Saccharomyces cerevisiae, γTuRC is composed of seven identical γ-tubulin small complex (γTuSC) sub-assemblies, which associate helically to template MT growth. γTuRC assembly provides a key point of regulation for the MT cytoskeleton. Here, we combine crosslinking mass spectrometry, X-ray crystallography, and cryo-EM structures of both monomeric and dimeric γTuSCs, and open and closed helical γTuRC assemblies in complex with Spc110p to elucidate the mechanisms of γTuRC assembly. γTuRC assembly is substantially aided by the evolutionarily conserved CM1 motif in Spc110p spanning a pair of adjacent γTuSCs. By providing the highest resolution and most complete views of any γTuSC assembly, our structures allow phosphorylation sites to be mapped, surprisingly suggesting that they are mostly inhibitory. A comparison of our structures with the CM1 binding site in the human γTuRC structure at the interface between GCP2 and GCP6 allows for the interpretation of significant structural changes arising from CM1 helix binding to metazoan γTuRC.
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Affiliation(s)
- Axel F Brilot
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Andrew S Lyon
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Alex Zelter
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Shruthi Viswanath
- Department of Bioengineering and Therapeutic Sciences, University of California at San FranciscoSan FranciscoUnited States
| | - Alison Maxwell
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Michael J MacCoss
- Department of Genome Sciences, University of WashingtonSeattleUnited States
| | - Eric G Muller
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California at San FranciscoSan FranciscoUnited States
| | - Trisha N Davis
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - David A Agard
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
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Brizendine RK, Anuganti M, Cremo CR. Evidence for S2 flexibility by direct visualization of quantum dot-labeled myosin heads and rods within smooth muscle myosin filaments moving on actin in vitro. J Gen Physiol 2021; 153:211680. [PMID: 33439241 PMCID: PMC7809879 DOI: 10.1085/jgp.202012751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/18/2020] [Accepted: 12/10/2020] [Indexed: 12/21/2022] Open
Abstract
Myosins in muscle assemble into filaments by interactions between the C-terminal light meromyosin (LMM) subdomains of the coiled-coil rod domain. The two head domains are connected to LMM by the subfragment-2 (S2) subdomain of the rod. Our mixed kinetic model predicts that the flexibility and length of S2 that can be pulled away from the filament affects the maximum distance working heads can move a filament unimpeded by actin-attached heads. It also suggests that it should be possible to observe a head remain stationary relative to the filament backbone while bound to actin (dwell), followed immediately by a measurable jump upon detachment to regain the backbone trajectory. We tested these predictions by observing filaments moving along actin at varying ATP using TIRF microscopy. We simultaneously tracked two different color quantum dots (QDs), one attached to a regulatory light chain on the lever arm and the other attached to an LMM in the filament backbone. We identified events (dwells followed by jumps) by comparing the trajectories of the QDs. The average dwell times were consistent with known kinetics of the actomyosin system, and the distribution of the waiting time between observed events was consistent with a Poisson process and the expected ATPase rate. Geometric constraints suggest a maximum of ∼26 nm of S2 can be unzipped from the filament, presumably involving disruption in the coiled-coil S2, a result consistent with observations by others of S2 protruding from the filament in muscle. We propose that sufficient force is available from the working heads in the filament to overcome the stiffness imposed by filament-S2 interactions.
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Affiliation(s)
- Richard K Brizendine
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
| | - Murali Anuganti
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
| | - Christine R Cremo
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
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Rüthnick D, Vitale J, Neuner A, Schiebel E. The N-terminus of Sfi1 and yeast centrin Cdc31 provide the assembly site for a new spindle pole body. J Cell Biol 2021; 220:211743. [PMID: 33523111 PMCID: PMC7852455 DOI: 10.1083/jcb.202004196] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 11/20/2020] [Accepted: 12/18/2020] [Indexed: 12/31/2022] Open
Abstract
The spindle pole body (SPB) provides microtubule-organizing functions in yeast and duplicates exactly once per cell cycle. The first step in SPB duplication is the half-bridge to bridge conversion via the antiparallel dimerization of the centrin (Cdc31)-binding protein Sfi1 in anaphase. The bridge, which is anchored to the old SPB on the proximal end, exposes free Sfi1 N-termini (N-Sfi1) at its distal end. These free N-Sfi1 promote in G1 the assembly of the daughter SPB (dSPB) in a yet unclear manner. This study shows that N-Sfi1 including the first three Cdc31 binding sites interacts with the SPB components Spc29 and Spc42, triggering the assembly of the dSPB. Cdc31 binding to N-Sfi1 promotes Spc29 recruitment and is essential for satellite formation. Furthermore, phosphorylation of N-Sfi1 has an inhibitory effect and delays dSPB biogenesis until G1. Taking these data together, we provide an understanding of the initial steps in SPB assembly and describe a new function of Cdc31 in the recruitment of dSPB components.
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Affiliation(s)
- Diana Rüthnick
- Center for Molecular Biology, University of Heidelberg, German Cancer Research Center-Center for Molecular Biology Alliance, Heidelberg, Germany
| | - Jlenia Vitale
- Center for Molecular Biology, University of Heidelberg, German Cancer Research Center-Center for Molecular Biology Alliance, Heidelberg, Germany
| | - Annett Neuner
- Center for Molecular Biology, University of Heidelberg, German Cancer Research Center-Center for Molecular Biology Alliance, Heidelberg, Germany
| | - Elmar Schiebel
- Center for Molecular Biology, University of Heidelberg, German Cancer Research Center-Center for Molecular Biology Alliance, Heidelberg, Germany
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Jaspersen SL. Anatomy of the fungal microtubule organizing center, the spindle pole body. Curr Opin Struct Biol 2020; 66:22-31. [PMID: 33113389 DOI: 10.1016/j.sbi.2020.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/14/2020] [Accepted: 09/19/2020] [Indexed: 12/21/2022]
Abstract
The fungal kingdom is large and diverse, representing extremes of ecology, life cycles and morphology. At a cellular level, the diversity among fungi is particularly apparent at the spindle pole body (SPB). This nuclear envelope embedded structure, which is essential for microtubule nucleation, shows dramatically different morphologies between different fungi. However, despite phenotypic diversity, many SPB components are conserved, suggesting commonalities in structure, function and duplication. Here, I review the organization of the most well-studied SPBs and describe how advances in genomics, genetics and cell biology have accelerated knowledge of SPB architecture in other fungi, providing insights into microtubule nucleation and other processes conserved across eukaryotes.
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Affiliation(s)
- Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO 64110, United States; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, United States.
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