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Ganser LR, Niaki AG, Yuan X, Huang E, Deng D, Djaja NA, Ge Y, Craig A, Langlois O, Myong S. The roles of FUS-RNA binding domain and low complexity domain in RNA-dependent phase separation. Structure 2024; 32:177-187.e5. [PMID: 38070499 PMCID: PMC10997494 DOI: 10.1016/j.str.2023.11.006] [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: 04/20/2023] [Revised: 10/24/2023] [Accepted: 11/14/2023] [Indexed: 02/04/2024]
Abstract
Fused in sarcoma (FUS) is an archetypal phase separating protein asymmetrically divided into a low complexity domain (LCD) and an RNA binding domain (RBD). Here, we explore how the two domains contribute to RNA-dependent phase separation, RNA recognition, and multivalent complex formation. We find that RBD drives RNA-dependent phase separation but forms large and irregularly shaped droplets that are rescued by LCD in trans. Electrophoretic mobility shift assay (EMSA) and single-molecule fluorescence assays reveal that, while both LCD and RBD bind RNA, RBD drives RNA engagement and multivalent complex formation. While RBD alone exhibits delayed RNA recognition and a less dynamic RNP complex compared to full-length FUS, LCD in trans rescues full-length FUS activity. Likewise, cell-based data show RBD forms nucleolar condensates while LCD in trans rescues the diffuse nucleoplasm localization of full-length FUS. Our results point to a regulatory role of LCD in tuning the RNP interaction and buffering phase separation.
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Affiliation(s)
- Laura R Ganser
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | | | - Xincheng Yuan
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA; Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Ethan Huang
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Dahlia Deng
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Nathalie A Djaja
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA; Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Yingda Ge
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Alanna Craig
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Olivia Langlois
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Sua Myong
- Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA; Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA.
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Djaja N, Myong S. Protocol for single-molecule pull-down of fluorescently tagged oligomers from cell lysates. STAR Protoc 2023; 4:102716. [PMID: 37967012 PMCID: PMC10684877 DOI: 10.1016/j.xpro.2023.102716] [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: 05/29/2023] [Revised: 08/29/2023] [Accepted: 10/27/2023] [Indexed: 11/17/2023] Open
Abstract
Mutations in intrinsically disordered proteins drive the irreversible formation of pathological aggregates, a hallmark of neurodegenerative diseases. Here, we present a protocol to pull down fluorescently tagged proteins to characterize their basal oligomeric states. We describe steps for transfection and cell lysis, single-molecule slide preparation and pull-down, and oligomer dissolution. This protocol enables visualization of protein oligomers with single-molecule resolution. In addition, differences in oligomerization may provide insight on condensation or aggregation propensity in differing mutated or cell stress conditions. For complete details on the use and execution of this protocol, please refer to Djaja et al.1.
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Affiliation(s)
- Nathalie Djaja
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
| | - Sua Myong
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218; Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218.
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Mekonnen G, Djaja N, Yuan X, Myong S. Advanced imaging techniques for studying protein phase separation in living cells and at single-molecule level. Curr Opin Chem Biol 2023; 76:102371. [PMID: 37523989 PMCID: PMC10528199 DOI: 10.1016/j.cbpa.2023.102371] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/04/2023] [Accepted: 06/24/2023] [Indexed: 08/02/2023]
Abstract
Protein-protein and protein-RNA interactions are essential for cell function and survival. These interactions facilitate the formation of ribonucleoprotein complexes and biomolecular condensates via phase separation. Such assembly is involved in transcription, splicing, translation and stress response. When dysregulated, proteins and RNA can undergo irreversible aggregation which can be cytotoxic and pathogenic. Despite technical advances in investigating biomolecular condensates, achieving the necessary spatiotemporal resolution to deduce the parameters that govern their assembly and behavior has been challenging. Many laboratories have applied advanced microscopy methods for imaging condensates. For example, single molecule imaging methods have enabled the detection of RNA-protein interaction, protein-protein interaction, protein conformational dynamics, and diffusional motion of molecules that report on the intrinsic molecular interactions underlying liquid-liquid phase separation. This review will outline advances in both microscopy and spectroscopy techniques which allow single molecule detection and imaging, and how these techniques can be used to probe unique aspects of biomolecular condensates.
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Affiliation(s)
- Gemechu Mekonnen
- Program in Cellular Molecular Developmental Biology and Biophysics, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Nathalie Djaja
- Program in Cellular Molecular Developmental Biology and Biophysics, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Xincheng Yuan
- Program in Cellular Molecular Developmental Biology and Biophysics, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Sua Myong
- Program in Cellular Molecular Developmental Biology and Biophysics, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA; Department of Biophysics, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA.
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