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Milano CR, Ur SN, Gu Y, Zhang J, Allison R, Brown G, Neale MJ, Tromer EC, Corbett KD, Hochwagen A. Chromatin binding by HORMAD proteins regulates meiotic recombination initiation. EMBO J 2024; 43:836-867. [PMID: 38332377 PMCID: PMC10907721 DOI: 10.1038/s44318-024-00034-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 01/08/2024] [Accepted: 01/11/2024] [Indexed: 02/10/2024] Open
Abstract
The meiotic chromosome axis coordinates chromosome organization and interhomolog recombination in meiotic prophase and is essential for fertility. In S. cerevisiae, the HORMAD protein Hop1 mediates the enrichment of axis proteins at nucleosome-rich islands through a central chromatin-binding region (CBR). Here, we use cryoelectron microscopy to show that the Hop1 CBR directly recognizes bent nucleosomal DNA through a composite interface in its PHD and winged helix-turn-helix domains. Targeted disruption of the Hop1 CBR-nucleosome interface causes a localized reduction of axis protein binding and meiotic DNA double-strand breaks (DSBs) in axis islands and leads to defects in chromosome synapsis. Synthetic effects with mutants of the Hop1 regulator Pch2 suggest that nucleosome binding delays a conformational switch in Hop1 from a DSB-promoting, Pch2-inaccessible state to a DSB-inactive, Pch2-accessible state to regulate the extent of meiotic DSB formation. Phylogenetic analyses of meiotic HORMADs reveal an ancient origin of the CBR, suggesting that the mechanisms we uncover are broadly conserved.
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Affiliation(s)
- Carolyn R Milano
- Department of Biology, New York University, New York, NY, 10003, USA
| | - Sarah N Ur
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, 92093, USA
- Vividion Therapeutics, San Diego, CA, 92121, USA
| | - Yajie Gu
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Jessie Zhang
- Department of Biology, New York University, New York, NY, 10003, USA
| | - Rachal Allison
- Genome Damage and Stability Centre, University of Sussex, Falmer, BN1 9RQ, UK
| | - George Brown
- Genome Damage and Stability Centre, University of Sussex, Falmer, BN1 9RQ, UK
| | - Matthew J Neale
- Genome Damage and Stability Centre, University of Sussex, Falmer, BN1 9RQ, UK
| | - Eelco C Tromer
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, 9747 AG, The Netherlands
| | - Kevin D Corbett
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
- Department of Molecular Biology, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Andreas Hochwagen
- Department of Biology, New York University, New York, NY, 10003, USA.
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Abstract
The process of eukaryotic ribosome assembly stretches across the nucleolus, the nucleoplasm and the cytoplasm, and therefore relies on efficient nucleocytoplasmic transport. In yeast, the import machinery delivers ~140,000 ribosomal proteins every minute to the nucleus for ribosome assembly. At the same time, the export machinery facilitates translocation of ~2000 pre-ribosomal particles every minute through ~200 nuclear pore complexes (NPC) into the cytoplasm. Eukaryotic ribosome assembly also requires >200 conserved assembly factors, which transiently associate with pre-ribosomal particles. Their site(s) of action on maturing pre-ribosomes are beginning to be elucidated. In this chapter, we outline protocols that enable rapid biochemical isolation of pre-ribosomal particles for single particle cryo-electron microscopy (cryo-EM) and in vitro reconstitution of nuclear transport processes. We discuss cell-biological and genetic approaches to investigate how the ribosome assembly and the nucleocytoplasmic transport machineries collaborate to produce functional ribosomes.
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Affiliation(s)
- Michaela Oborská-Oplová
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Ute Fischer
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | | | - Vikram Govind Panse
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
- Faculty of Science, University of Zurich, Zurich, Switzerland.
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Caloca B, Navarro A, Canales-Torres M, Le B, Rosas C, Sero Z, Bachant J. Comparison of Concanavalin A and Poly-L-lysine as Cell Adhesives for Routine Yeast Microscopy Applications. Yeast 2021; 39:312-322. [PMID: 34931343 DOI: 10.1002/yea.3686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 11/12/2021] [Accepted: 12/09/2021] [Indexed: 11/09/2022] Open
Abstract
A frequently encountered problem with imaging budding yeast specimens by light microscopy is that the cells do not adhere well to glass microscope slides. Frustratingly, cells that initially appear stationary in the visual field often become displaced and float away. The development of immunofluorescence microscopy methods for yeast led to the widespread use of poly-L-lysine as an adhesive for cell immobilization. More recently, the lectin-binding protein Concanavalin A has also been used as an adhesive that may be less familiar to yeast investigators. Here we directly compare the ability of poly-L-lysine and Concanavalin A to adhere yeast to glass microscope slides using several different assays. Using a simple coating procedure, we find that 1 mg/ml Concanavalin A proves superior to various concentrations of poly-L-lysine under all conditions tested, and that Concanavalin A can be used as an adhesive for live cell imaging without impairing yeast proliferation or cell division kinetics. Importantly, we also delineate forms of sample preparation that are or are not compatible with Concanavalin A. Overall, we hope our findings will bring Concanavalin A to the attention of a broad spectrum of the yeast community for their microscopy needs.
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Affiliation(s)
- Bryanna Caloca
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
| | - Alejandro Navarro
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
| | - Marcelino Canales-Torres
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
| | - Brittany Le
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
| | - Carol Rosas
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
| | - Zig Sero
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
| | - Jeff Bachant
- Department of Molecular Cell Systems Biology, University of California, Riverside, Riverside, CA
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Abstract
Biologists have long observed periodic-like oxygen consumption oscillations in yeast populations under certain conditions, and several unsatisfactory explanations for this phenomenon have been proposed. These ‘autonomous oscillations’ have often appeared with periods that are nearly integer divisors of the calculated doubling time of the culture. We hypothesize that these oscillations could be caused by a form of cell cycle synchronization that we call clustering. We develop some novel ordinary differential equation models of the cell cycle. For these models, and for random and stochastic perturbations, we give both rigorous proofs and simulations showing that both positive and negative growth rate feedback within the cell cycle are possible agents that can cause clustering of populations within the cell cycle. It occurs for a variety of models and for a broad selection of parameter values. These results suggest that the clustering phenomenon is robust and is likely to be observed in nature. Since there are necessarily an integer number of clusters, clustering would lead to periodic-like behaviour with periods that are nearly integer divisors of the period of the cell cycle. Related experiments have shown conclusively that cell cycle clustering occurs in some oscillating yeast cultures.
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Affiliation(s)
- Erik M. Boczko
- Department of Biomedical Informatics, Vanderbilt University
| | | | - Tomas Gedeon
- Department of Mathematics, Montana State University
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