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Lemke EA, Babu MM, Kriwacki RW, Mittag T, Pappu RV, Wright PE, Forman-Kay JD. Intrinsic disorder: A term to define the specific physicochemical characteristic of protein conformational heterogeneity. Mol Cell 2024; 84:1188-1190. [PMID: 38579677 DOI: 10.1016/j.molcel.2024.02.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 02/19/2024] [Accepted: 02/23/2024] [Indexed: 04/07/2024]
Abstract
In his commentary in this issue of Molecular Cell,1 Struhl reasons that the term "intrinsically disordered regions" represents a vague and confusing concept for protein function. However, the term "intrinsically disordered" highlights the important physicochemical characteristic of conformational heterogeneity. Thus, "intrinsically disordered" is the counterpart to the term "folded, " with neither term having specific functional implications.
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Affiliation(s)
- Edward A Lemke
- Biocenter, Johannes Gutenberg University, Hanns-Dieter-Hüsch Weg 17, 55128 Mainz, Germany; Institute for Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.
| | - M Madan Babu
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA; Center of Excellence for Data Driven Discovery, Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN, USA.
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO 63130, USA.
| | - Peter E Wright
- Department of Integrative Structural and Computational Biology and Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
| | - Julie D Forman-Kay
- Molecular Medicine Program, Hospital for Sick Children, Toronto ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto ON M5S 1A8, Canada.
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2
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Das T, Zaidi F, Farag M, Ruff KM, Messing J, Taylor JP, Pappu RV, Mittag T. Metastable condensates suppress conversion to amyloid fibrils. bioRxiv 2024:2024.02.28.582569. [PMID: 38464104 PMCID: PMC10925303 DOI: 10.1101/2024.02.28.582569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Stress granules form via co-condensation of RNA binding proteins with prion-like low complexity domains (PLCDs) and RNA molecules released by stress-induced polysomal runoff. Homotypic interactions among PLCDs can drive amyloid fibril formation and this is enhanced by ALS-associated mutations. We find that homotypic interactions that drive condensation versus fibril formation are separable for A1-LCD, the PLCD of hnRNPA1. These separable interactions lead to condensates that are metastable versus fibrils that are globally stable. Metastable condensates suppress fibril formation, and ALS-associated mutations enhance fibril formation by weakening condensate metastability. Mutations designed to enhance A1-LCD condensate metastability restore wild-type behaviors of stress granules in cells even when ALS-associated mutations are present. This suggests that fibril formation can be suppressed by enhancing condensate metastability through condensate-driving interactions.
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Affiliation(s)
- Tapojyoti Das
- Department of Structural Biology, St. Jude Children’s Research Hospital; Memphis, TN 38105, USA
| | - Fatima Zaidi
- Department of Structural Biology, St. Jude Children’s Research Hospital; Memphis, TN 38105, USA
| | - Mina Farag
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis; St. Louis, MO 63130, USA
| | - Kiersten M. Ruff
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis; St. Louis, MO 63130, USA
| | - James Messing
- Department of Cell and Molecular Biology, St. Jude Children’s Research Hospital; Memphis, TN 38105, USA
| | - J. Paul Taylor
- Department of Cell and Molecular Biology, St. Jude Children’s Research Hospital; Memphis, TN 38105, USA
| | - Rohit V. Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis; St. Louis, MO 63130, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research Hospital; Memphis, TN 38105, USA
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3
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Alshareedah I, Borcherds WM, Cohen SR, Singh A, Posey AE, Farag M, Bremer A, Strout GW, Tomares DT, Pappu RV, Mittag T, Banerjee PR. Sequence-specific interactions determine viscoelasticity and aging dynamics of protein condensates. bioRxiv 2023:2023.04.06.535902. [PMID: 37066350 PMCID: PMC10104120 DOI: 10.1101/2023.04.06.535902] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Biomolecular condensates are viscoelastic materials. Here, we report results from investigations into molecular-scale determinants of sequence-encoded and age-dependent viscoelasticity of condensates formed by prion-like low-complexity domains (PLCDs). The terminally viscous forms of PLCD condensates are Maxwell fluids. Measured viscoelastic moduli of these condensates are reproducible using a Rouse-Zimm model that accounts for the network-like organization engendered by reversible physical crosslinks among PLCDs in the dense phase. Measurements and computations show that the strengths of aromatic inter-sticker interactions determine the sequence-specific amplitudes of elastic and viscous moduli as well as the timescales over which elastic properties dominate. PLCD condensates also undergo physical aging on sequence-specific timescales. This is driven by mutations to spacer residues that weaken the metastability of terminally viscous phases. The aging of PLCD condensates is accompanied by disorder-to-order transitions, leading to the formation of non-fibrillar, beta-sheet-containing, semi-crystalline, terminally elastic, Kelvin-Voigt solids. Our results suggest that sequence grammars, which refer to the identities of stickers versus spacers in PLCDs, have evolved to afford control over the metastabilities of terminally viscous fluid phases of condensates. This selection can, in some cases, render barriers for conversion from metastable fluids to globally stable solids to be insurmountable on functionally relevant timescales.
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4
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Sabri N, Cuneo MJ, Marzahn MR, Lee J, Bouchard JJ, Güllülü Ö, Vaithiyalingam S, Borgia MB, Schmit J, Mittag T. Reduction of oligomer size modulates the competition between cluster formation and phase separation of the tumor suppressor SPOP. J Biol Chem 2023; 299:105427. [PMID: 37926283 PMCID: PMC10696467 DOI: 10.1016/j.jbc.2023.105427] [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: 05/09/2023] [Revised: 09/26/2023] [Accepted: 10/17/2023] [Indexed: 11/07/2023] Open
Abstract
Phase separation compartmentalizes many cellular pathways. Given that the same interactions that drive phase separation mediate the formation of soluble complexes below the saturation concentration, the contribution of condensates versus complexes to function is sometimes unclear. Here, we characterized several new cancer-associated mutations of the tumor suppressor speckle-type POZ protein (SPOP), a substrate recognition subunit of the Cullin3-RING ubiquitin ligase. This pointed to a strategy for generating separation-of-function mutations. SPOP self-associates into linear oligomers and interacts with multivalent substrates, and this mediates the formation of condensates. These condensates bear the hallmarks of enzymatic ubiquitination activity. We characterized the effect of mutations in the dimerization domains of SPOP on its linear oligomerization, binding to its substrate DAXX, and phase separation with DAXX. We showed that the mutations reduce SPOP oligomerization and shift the size distribution of SPOP oligomers to smaller sizes. The mutations therefore reduce the binding affinity to DAXX but unexpectedly enhance the poly-ubiquitination activity of SPOP toward DAXX. Enhanced activity may be explained by enhanced phase separation of DAXX with the SPOP mutants. Our results provide a comparative assessment of the functional role of complexes versus condensates and support a model in which phase separation is an important factor in SPOP function. Our findings also suggest that tuning of linear SPOP self-association could be used by the cell to modulate activity and provide insights into the mechanisms underlying hypermorphic SPOP mutations. The characteristics of cancer-associated SPOP mutations suggest a route for designing separation-of-function mutations in other phase-separating systems.
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Affiliation(s)
- Nafiseh Sabri
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Matthew J Cuneo
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Melissa R Marzahn
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jihun Lee
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jill J Bouchard
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ömer Güllülü
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Sivaraja Vaithiyalingam
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Madeleine B Borgia
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jeremy Schmit
- Department of Physics, Kansas State University, Manhattan, Kansas, USA
| | - Tanja Mittag
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA.
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5
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Pesce F, Bremer A, Tesei G, Hopkins JB, Grace CR, Mittag T, Lindorff-Larsen K. Design of intrinsically disordered protein variants with diverse structural properties. bioRxiv 2023:2023.10.22.563461. [PMID: 37961110 PMCID: PMC10634714 DOI: 10.1101/2023.10.22.563461] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Intrinsically disordered proteins (IDPs) perform a wide range of functions in biology, suggesting that the ability to design IDPs could help expand the repertoire of proteins with novel functions. Designing IDPs with specific structural or functional properties has, however, been difficult, in part because determining accurate conformational ensembles of IDPs generally requires a combination of computational modelling and experiments. Motivated by recent advancements in efficient physics-based models for simulations of IDPs, we have developed a general algorithm for designing IDPs with specific structural properties. We demonstrate the power of the algorithm by generating variants of naturally occurring IDPs with different levels of compaction and that vary more than 100 fold in their propensity to undergo phase separation, even while keeping a fixed amino acid composition. We experimentally tested designs of variants of the low-complexity domain of hnRNPA1 and find high accuracy in our computational predictions, both in terms of single-chain compaction and propensity to undergo phase separation. We analyze the sequence features that determine changes in compaction and propensity to phase separate and find an overall good agreement with previous findings for naturally occurring sequences. Our general, physics-based method enables the design of disordered sequences with specified conformational properties. Our algorithm thus expands the toolbox for protein design to include also the most flexible proteins and will enable the design of proteins whose functions exploit the many properties afforded by protein disorder.
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Affiliation(s)
- Francesco Pesce
- Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Giulio Tesei
- Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Jesse B. Hopkins
- BioCAT, Department of Physics, Illinois Institute of Technology, Chicago, IL, USA
| | - Christy R. Grace
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Kresten Lindorff-Larsen
- Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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6
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Chauhan G, Bremer A, Dar F, Mittag T, Pappu RV. Crowder titrations enable the quantification of driving forces for macromolecular phase separation. Biophys J 2023:S0006-3495(23)00582-9. [PMID: 37717144 DOI: 10.1016/j.bpj.2023.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/03/2023] [Accepted: 09/13/2023] [Indexed: 09/18/2023] Open
Abstract
Macromolecular solubility is an important contributor to the driving forces for phase separation. Formally, the driving forces in a binary mixture comprising a macromolecule dissolved in a solvent can be quantified in terms of the saturation concentration, which is the threshold macromolecular concentration above which the mixture separates into coexisting dense and dilute phases. In addition, the second virial coefficient, which measures the effective strength of solvent-mediated intermolecular interactions provides direct assessments of solvent quality. The sign and magnitude of second virial coefficients will be governed by a combination of solution conditions and the nature of the macromolecule of interest. Here, we show, using a combination of theory, simulation, and in vitro experiments, that titrations of crowders, providing they are true depletants, can be used to extract the intrinsic driving forces for macromolecular phase separation. This refers to saturation concentrations in the absence of crowders and the second virial coefficients that quantify the magnitude of the incompatibility between macromolecules and the solvent. Our results show how the depletion-mediated attractions afforded by crowders can be leveraged to obtain comparative assessments of macromolecule-specific, intrinsic driving forces for phase separation.
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Affiliation(s)
- Gaurav Chauhan
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Furqan Dar
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri.
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7
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Farag M, Borcherds WM, Bremer A, Mittag T, Pappu RV. Phase separation of protein mixtures is driven by the interplay of homotypic and heterotypic interactions. Nat Commun 2023; 14:5527. [PMID: 37684240 PMCID: PMC10491635 DOI: 10.1038/s41467-023-41274-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [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: 04/27/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023] Open
Abstract
Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via phase separation coupled to percolation. Intracellular condensates often encompass numerous distinct proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA-binding proteins, hnRNPA1 and FUS. Using simulations and experiments, we find that 1:1 mixtures of A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own due to complementary electrostatic interactions. Tie line analysis reveals that stoichiometric ratios of different components and their sequence-encoded interactions contribute jointly to the driving forces for condensate formation. Simulations also show that the spatial organization of PLCDs within condensates is governed by relative strengths of homotypic versus heterotypic interactions. We uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins.
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Affiliation(s)
- Mina Farag
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, 63130, USA.
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8
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Chauhan G, Bremer A, Dar F, Mittag T, Pappu RV. Crowder titrations enable the quantification of driving forces for macromolecular phase separation. bioRxiv 2023:2023.07.03.547544. [PMID: 37461587 PMCID: PMC10350001 DOI: 10.1101/2023.07.03.547544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Macromolecular solubility is an important contributor to the driving forces for phase separation. Formally, the driving forces in a binary mixture comprising a macromolecule dissolved in a solvent can be quantified in terms of the saturation concentration, which is the threshold macromolecular concentration above which the mixture separates into coexisting dense and dilute phases. Additionally, the second virial coefficient, which measures the effective strength of solvent-mediated intermolecular interactions provides direct assessments of solvent quality. The sign and magnitude of second virial coefficients will be governed by a combination of solution conditions and the nature of the macromolecule of interest. Here, we show, using a combination of theory, simulation, and in vitro experiments, that titrations of crowders, providing they are true depletants, can be used to extract the intrinsic driving forces for macromolecular phase separation. This refers to saturation concentrations in the absence of crowders and the second virial coefficients that quantify the magnitude of the incompatibility between macromolecules and the solvent. Our results show how the depletion-mediated attractions afforded by crowders can be leveraged to obtain comparative assessments of macromolecule-specific, intrinsic driving forces for phase separation. SIGNIFICANCE Phase separation has emerged as a process of significant relevance to sorting macromolecules into distinct compartments, thereby enabling spatial and temporal control over cellular matter. Considerable effort is being invested into uncovering the driving forces that enable the separation of macromolecular solutions into coexisting phases. At its heart, this process is governed by the balance of macromolecule-solvent, inter-macromolecule, and solvent-solvent interactions. We show that the driving forces for phase separation, including the coefficients that measure interaction strengths between macromolecules, can be extracted by titrating the concentrations of crowders that enable macromolecules to phase separate at lower concentrations. Our work paves the way to leverage specific categories of measurements for quantitative characterizations of driving forces for phase separation.
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Pappu R, Farag M, Borcherds W, Bremer A, Mittag T. Phase Separation in Mixtures of Prion-Like Low Complexity Domains is Driven by the Interplay of Homotypic and Heterotypic Interactions. Res Sq 2023:rs.3.rs-2870258. [PMID: 37205474 PMCID: PMC10187436 DOI: 10.21203/rs.3.rs-2870258/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via coupled associative and segregative phase transitions. We previously deciphered how evolutionarily conserved sequence features drive phase separation of PLCDs through homotypic interactions. However, condensates typically encompass a diverse mixture of proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA binding proteins namely, hnRNPA1 and FUS. We find that 1:1 mixtures of the A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own. The enhanced driving forces for phase separation of mixtures of A1-LCD and FUS-LCD arise partly from complementary electrostatic interactions between the two proteins. This complex coacervation-like mechanism adds to complementary interactions among aromatic residues. Further, tie line analysis shows that stoichiometric ratios of different components and their sequence-encoded interactions jointly contribute to the driving forces for condensate formation. These results highlight how expression levels might be tuned to regulate the driving forces for condensate formation in vivo . Simulations also show that the organization of PLCDs within condensates deviates from expectations based on random mixture models. Instead, spatial organization within condensates will reflect the relative strengths of homotypic versus heterotypic interactions. We also uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins. Overall, our findings emphasize the network-like organization of molecules within multicomponent condensates, and the distinctive, composition-specific conformational features of condensate interfaces.
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10
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Mayr C, Mittag T, Tang TYD, Wen W, Zhang H, Zhang H. Frontiers in biomolecular condensate research. Nat Cell Biol 2023; 25:512-514. [PMID: 36973422 DOI: 10.1038/s41556-023-01102-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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11
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Sabri N, Cuneo MJ, Marzahn MR, Lee J, Bouchard JJ, Vaithiyalingam S, Borgia MB, Schmit J, Mittag T. Reduction of oligomer size modulates the competition between cluster formation and phase separation of the tumor suppressor SPOP. bioRxiv 2023:2023.02.11.528154. [PMID: 36993550 PMCID: PMC10054981 DOI: 10.1101/2023.02.11.528154] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Phase separation is a ubiquitous process that compartmentalizes many cellular pathways. Given that the same interactions that drive phase separation mediate the formation of complexes below the saturation concentration, the contribution of condensates vs complexes to function is not always clear. Here, we characterized several new cancer-associated mutations of the tumor suppressor Speckle-type POZ protein (SPOP), a substrate recognition subunit of the Cullin3-RING ubiquitin ligase (CRL3), which pointed to a strategy for generating separation-of-function mutations. SPOP self-associates into linear oligomers and interacts with multivalent substrates, and this mediates the formation of condensates. These condensates bear the hallmarks of enzymatic ubiquitination activity. We characterized the effect of mutations in the dimerization domains of SPOP on its linear oligomerization, binding to the substrate DAXX, and phase separation with DAXX. We showed that the mutations reduce SPOP oligomerization and shift the size distribution of SPOP oligomers to smaller sizes. The mutations therefore reduce the binding affinity to DAXX, but enhance the poly-ubiquitination activity of SPOP towards DAXX. This unexpectedly enhanced activity may be explained by enhanced phase separation of DAXX with the SPOP mutants. Our results provide a comparative assessment of the functional role of clusters versus condensates and support a model in which phase separation is an important factor in SPOP function. Our findings also suggest that tuning of linear SPOP self-association could be used by the cell to modulate its activity, and provide insights into the mechanisms underlying hypermorphic SPOP mutations. The characteristics of these cancer-associated SPOP mutations suggest a route for designing separation-of-function mutations in other phase-separating systems.
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Affiliation(s)
- Nafiseh Sabri
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
| | - Matthew J. Cuneo
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
| | - Melissa R. Marzahn
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
- Current address: Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL, USA
| | - Jihun Lee
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
- Current address: Celltrion, South Korea
| | - Jill J. Bouchard
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
- Current address: Dewpoint Therapeutics, Boston, MA 02210, USA
| | - Sivaraja Vaithiyalingam
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
| | - Madeleine B. Borgia
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
| | - Jeremy Schmit
- Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38103, USA
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12
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Farag M, Borcherds WM, Bremer A, Mittag T, Pappu RV. Phase Separation in Mixtures of Prion-Like Low Complexity Domains is Driven by the Interplay of Homotypic and Heterotypic Interactions. bioRxiv 2023:2023.03.15.532828. [PMID: 36993212 PMCID: PMC10055064 DOI: 10.1101/2023.03.15.532828] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via coupled associative and segregative phase transitions. We previously deciphered how evolutionarily conserved sequence features drive phase separation of PLCDs through homotypic interactions. However, condensates typically encompass a diverse mixture of proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA binding proteins namely, hnRNPA1 and FUS. We find that 1:1 mixtures of the A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own. The enhanced driving forces for phase separation of mixtures of A1-LCD and FUS-LCD arise partly from complementary electrostatic interactions between the two proteins. This complex coacervation-like mechanism adds to complementary interactions among aromatic residues. Further, tie line analysis shows that stoichiometric ratios of different components and their sequence-encoded interactions jointly contribute to the driving forces for condensate formation. These results highlight how expression levels might be tuned to regulate the driving forces for condensate formation in vivo . Simulations also show that the organization of PLCDs within condensates deviates from expectations based on random mixture models. Instead, spatial organization within condensates will reflect the relative strengths of homotypic versus heterotypic interactions. We also uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins. Overall, our findings emphasize the network-like organization of molecules within multicomponent condensates, and the distinctive, composition-specific conformational features of condensate interfaces. Significance Statement Biomolecular condensates are mixtures of different protein and nucleic acid molecules that organize biochemical reactions in cells. Much of what we know about how condensates form comes from studies of phase transitions of individual components of condensates. Here, we report results from studies of phase transitions of mixtures of archetypal protein domains that feature in distinct condensates. Our investigations, aided by a blend of computations and experiments, show that the phase transitions of mixtures are governed by a complex interplay of homotypic and heterotypic interactions. The results point to how expression levels of different protein components can be tuned in cells to modulate internal structures, compositions, and interfaces of condensates, thus affording distinct ways to control the functions of condensates.
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13
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Cuneo MJ, O'Flynn BG, Lo YH, Sabri N, Mittag T. Higher-order SPOP assembly reveals a basis for cancer mutant dysregulation. Mol Cell 2023; 83:731-745.e4. [PMID: 36693379 PMCID: PMC9992347 DOI: 10.1016/j.molcel.2022.12.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [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: 08/05/2022] [Revised: 11/19/2022] [Accepted: 12/30/2022] [Indexed: 01/24/2023]
Abstract
The speckle-type POZ protein (SPOP) functions in the Cullin3-RING ubiquitin ligase (CRL3) as a receptor for the recognition of substrates involved in cell growth, survival, and signaling. SPOP mutations have been attributed to the development of many types of cancers, including prostate and endometrial cancers. Prostate cancer mutations localize in the substrate-binding site of the substrate recognition (MATH) domain and reduce or prevent binding. However, most endometrial cancer mutations are dispersed in seemingly inconspicuous solvent-exposed regions of SPOP, offering no clear basis for their cancer-causing and peculiar gain-of-function properties. Herein, we present the first structure of SPOP in its oligomeric form, uncovering several new interfaces important for SPOP self-assembly and normal function. Given that many previously unaccounted-for cancer mutations are localized in these newly identified interfaces, we uncover molecular mechanisms underlying dysregulation of SPOP function, with effects ranging from gross structural changes to enhanced self-association, and heightened stability and activity.
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Affiliation(s)
- Matthew J Cuneo
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA
| | - Brian G O'Flynn
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA
| | - Yu-Hua Lo
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA
| | - Nafiseh Sabri
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA.
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14
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Thomasen FE, Cuneo MJ, Mittag T, Lindorff-Larsen K. Conformational and oligomeric states of SPOP from small-angle X-ray scattering and molecular dynamics simulations. eLife 2023; 12:e84147. [PMID: 36856266 PMCID: PMC9998093 DOI: 10.7554/elife.84147] [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: 10/12/2022] [Accepted: 02/20/2023] [Indexed: 03/02/2023] Open
Abstract
Speckle-type POZ protein (SPOP) is a substrate adaptor in the ubiquitin proteasome system, and plays important roles in cell-cycle control, development, and cancer pathogenesis. SPOP forms linear higher-order oligomers following an isodesmic self-association model. Oligomerization is essential for SPOP's multivalent interactions with substrates, which facilitate phase separation and localization to biomolecular condensates. Structural characterization of SPOP in its oligomeric state and in solution is, however, challenging due to the inherent conformational and compositional heterogeneity of the oligomeric species. Here, we develop an approach to simultaneously and self-consistently characterize the conformational ensemble and the distribution of oligomeric states of SPOP by combining small-angle X-ray scattering (SAXS) and molecular dynamics (MD) simulations. We build initial conformational ensembles of SPOP oligomers using coarse-grained molecular dynamics simulations, and use a Bayesian/maximum entropy approach to refine the ensembles, along with the distribution of oligomeric states, against a concentration series of SAXS experiments. Our results suggest that SPOP oligomers behave as rigid, helical structures in solution, and that a flexible linker region allows SPOP's substrate-binding domains to extend away from the core of the oligomers. Additionally, our results are in good agreement with previous characterization of the isodesmic self-association of SPOP. In the future, the approach presented here can be extended to other systems to simultaneously characterize structural heterogeneity and self-assembly.
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Affiliation(s)
- F Emil Thomasen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of CopenhagenCopenhagenDenmark
| | - Matthew J Cuneo
- Department of Structural Biology, St. Jude Children’s Research HospitalMemphisUnited States
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research HospitalMemphisUnited States
| | - Kresten Lindorff-Larsen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of CopenhagenCopenhagenDenmark
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15
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Cohen SR, Alshareedah I, Borcherds WM, Farag M, Mittag T, Banerjee PR, Pappu RV. Modified Rouse-Zimm theory for computing sequence-specific viscoelastic properties of biomolecular condensates. Biophys J 2023; 122:206a. [PMID: 36783000 DOI: 10.1016/j.bpj.2022.11.1238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Samuel R Cohen
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, USA; Center of Regenerative Medicine, Washington University in St. Louis, St. Louis, MO, USA
| | | | - Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Mina Farag
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | | | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, USA; Center of Regenerative Medicine, Washington University in St. Louis, St. Louis, MO, USA
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16
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Farag M, Bremer A, Borcherds WM, Mittag T, Pappu RV. Complex coacervation contributes to the joint phase behaviors of mixtures of charge-deficient prion-like low-complexity domains. Biophys J 2023; 122:159a. [PMID: 36782740 DOI: 10.1016/j.bpj.2022.11.967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Mina Farag
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Rohit V Pappu
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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17
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Alshareedah I, Borcherds WM, Singh A, Cohen SR, Farag M, Pappu RV, Mittag T, Banerjee PR. Uncovering the distinct roles of enthalpy and entropy that give rise to viscoelasticity in biomolecular condensates. Biophys J 2023; 122:207a. [PMID: 36783005 DOI: 10.1016/j.bpj.2022.11.1244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
| | - Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Anurag Singh
- Department of Physics, University at Buffalo, Buffalo, NY, USA
| | - Samuel R Cohen
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Mina Farag
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
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18
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Zaidi FK, Das T, Mittag T. Understanding the mechanism of fibrillization of hnRNPA1 from phase-separated condensates. Biophys J 2023; 122:485a. [PMID: 36784499 DOI: 10.1016/j.bpj.2022.11.2593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Fatimah K Zaidi
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tapojyoti Das
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
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19
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Chauhan G, Bremer A, Dar F, Mittag T, Pappu RV. Effects of crowders on phase separation of associative macromolecules. Biophys J 2023; 122:205a-206a. [PMID: 36782993 DOI: 10.1016/j.bpj.2022.11.1237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Gaurav Chauhan
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Furqan Dar
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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20
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Borcherds WM, Alshareedah I, Singh A, Das T, Bremer A, Banerjee PR, Pappu RV, Mittag T. A stickers-and-spacers framework explains the viscoelastic and aging properties of biomolecular condensates. Biophys J 2023; 122:296a. [PMID: 36783473 DOI: 10.1016/j.bpj.2022.11.1674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | | | - Anurag Singh
- Department of Physics, University at Buffalo, Buffalo, NY, USA
| | - Tapojyoti Das
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Anne Bremer
- St. Jude Children's Research Hospital, Memphis, TN, USA
| | | | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
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21
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Farag M, Cohen SR, Borcherds WM, Bremer A, Mittag T, Pappu RV. Condensates formed by prion-like low-complexity domains have small-world network structures and interfaces defined by expanded conformations. Nat Commun 2022; 13:7722. [PMID: 36513655 PMCID: PMC9748015 DOI: 10.1038/s41467-022-35370-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022] Open
Abstract
Biomolecular condensates form via coupled associative and segregative phase transitions of multivalent associative macromolecules. Phase separation coupled to percolation is one example of such transitions. Here, we characterize molecular and mesoscale structural descriptions of condensates formed by intrinsically disordered prion-like low complexity domains (PLCDs). These systems conform to sticker-and-spacers architectures. Stickers are cohesive motifs that drive associative interactions through reversible crosslinking and spacers affect the cooperativity of crosslinking and overall macromolecular solubility. Our computations reproduce experimentally measured sequence-specific phase behaviors of PLCDs. Within simulated condensates, networks of reversible inter-sticker crosslinks organize PLCDs into small-world topologies. The overall dimensions of PLCDs vary with spatial location, being most expanded at and preferring to be oriented perpendicular to the interface. Our results demonstrate that even simple condensates with one type of macromolecule feature inhomogeneous spatial organizations of molecules and interfacial features that likely prime them for biochemical activity.
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Affiliation(s)
- Mina Farag
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, USA
| | - Samuel R Cohen
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, USA
| | - Wade M Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, Washington University in St. Louis, St. Louis, MO, USA.
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22
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Bremer A, Posey AE, Borgia MB, Borcherds WM, Farag M, Pappu RV, Mittag T. Quantifying Coexistence Concentrations in Multi-Component Phase-Separating Systems Using Analytical HPLC. Biomolecules 2022; 12:biom12101480. [PMID: 36291688 PMCID: PMC9599810 DOI: 10.3390/biom12101480] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 09/30/2022] [Accepted: 10/03/2022] [Indexed: 11/28/2022] Open
Abstract
Over the last decade, evidence has accumulated to suggest that numerous instances of cellular compartmentalization can be explained by the phenomenon of phase separation. This is a process by which a macromolecular solution separates spontaneously into dense and dilute coexisting phases. Semi-quantitative, in vitro approaches for measuring phase boundaries have proven very useful in determining some key features of biomolecular condensates, but these methods often lack the precision necessary for generating quantitative models. Therefore, there is a clear need for techniques that allow quantitation of coexisting dilute and dense phase concentrations of phase-separating biomolecules, especially in systems with more than one type of macromolecule. Here, we report the design and deployment of analytical High-Performance Liquid Chromatography (HPLC) for in vitro separation and quantification of distinct biomolecules that allows us to measure dilute and dense phase concentrations needed to reconstruct coexistence curves in multicomponent mixtures. This approach is label-free, detects lower amounts of material than is accessible with classic UV-spectrophotometers, is applicable to a broad range of macromolecules of interest, is a semi-high-throughput technique, and if needed, the macromolecules can be recovered for further use. The approach promises to provide quantitative insights into the balance of homotypic and heterotypic interactions in multicomponent phase-separating systems.
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Affiliation(s)
- Anne Bremer
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Ammon E. Posey
- Department of Biomedical Engineering, Center for Biomolecular Condensates (CBC), James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Madeleine B. Borgia
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Wade M. Borcherds
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Mina Farag
- Department of Biomedical Engineering, Center for Biomolecular Condensates (CBC), James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Rohit V. Pappu
- Department of Biomedical Engineering, Center for Biomolecular Condensates (CBC), James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
- Correspondence: (R.V.P.); (T.M.)
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
- Correspondence: (R.V.P.); (T.M.)
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23
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Tawaratsumida K, Redecke V, Wu R, Kuriakose J, Bouchard JJ, Mittag T, Lohman BK, Mishra A, High AA, Häcker H. A phospho-tyrosine-based signaling module using SPOP, CSK, and LYN controls TLR-induced IRF activity. Sci Adv 2022; 8:eabq0084. [PMID: 35857476 PMCID: PMC9269885 DOI: 10.1126/sciadv.abq0084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
Toll-like receptors (TLRs) recognize pathogen- and host-derived factors and control immune responses via the adaptor protein MyD88 and members of the interferon regulatory transcription factor (IRF) family. IRFs orchestrate key effector functions, including cytokine release, cell differentiation, and, under certain circumstances, inflammation pathology. Here, we show that IRF activity is generically controlled by the Src kinase family member LYN, which phosphorylates all TLR-induced IRFs at a conserved tyrosine residue, resulting in K48-linked polyubiquitination and proteasomal degradation of IRFs. We further show that LYN activity is controlled by the upstream kinase C-terminal Src kinase (CSK), whose activity, in turn, is controlled by the adaptor protein SPOP, which serves as molecular bridge to recruit CSK into the TLR signaling complex and to activate CSK catalytic activity. Consistently, deletion of SPOP or CSK results in increased LYN activity, LYN-directed IRF degradation, and inhibition of IRF transcriptional activity. Together, the data reveal a key regulatory mechanism for IRF family members controlling TLR biology.
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Affiliation(s)
- Kazuki Tawaratsumida
- Laboratory of Innate Immunity and Signal Transduction, Department of Pathology, Division of Microbiology and Immunology, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Vanessa Redecke
- Laboratory of Innate Immunity and Signal Transduction, Department of Pathology, Division of Microbiology and Immunology, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Ruiqiong Wu
- Department of Hematology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Jeeba Kuriakose
- Children’s GMP, LLC., St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Jill J. Bouchard
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Brian K. Lohman
- Bioinformatics Shared Resource, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Ashutosh Mishra
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Anthony A. High
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Hans Häcker
- Laboratory of Innate Immunity and Signal Transduction, Department of Pathology, Division of Microbiology and Immunology, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
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24
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Mittag T, Pappu RV. A conceptual framework for understanding phase separation and addressing open questions and challenges. Mol Cell 2022; 82:2201-2214. [DOI: 10.1016/j.molcel.2022.05.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 05/04/2022] [Accepted: 05/13/2022] [Indexed: 12/11/2022]
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25
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Mittag T, Bremer A, Farag M, Borcherds WM, Pappu RV. Phase behavior of intrinsically disordered prion‐like domains. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.0i193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Tanja Mittag
- Structural BiologySt. Jude Children's Research HospitalMemphisTN
| | - Anne Bremer
- Structural BiologySt. Jude Children's Research HospitalMemphisTN
| | - Mina Farag
- Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS)Washington University in St LouisSt. LouisMO
| | | | - Rohit V. Pappu
- Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS)Washington University in St LouisSt. LouisMO
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26
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Bremer A, Farag M, Borcherds WM, Peran I, Martin EW, Pappu RV, Mittag T. Deciphering how naturally occurring sequence features impact the phase behaviours of disordered prion-like domains. Nat Chem 2022; 14:196-207. [PMID: 34931046 PMCID: PMC8818026 DOI: 10.1038/s41557-021-00840-w] [Citation(s) in RCA: 143] [Impact Index Per Article: 71.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 10/19/2021] [Indexed: 12/20/2022]
Abstract
Prion-like low-complexity domains (PLCDs) have distinctive sequence grammars that determine their driving forces for phase separation. Here we uncover the physicochemical underpinnings of how evolutionarily conserved compositional biases influence the phase behaviour of PLCDs. We interpret our results in the context of the stickers-and-spacers model for the phase separation of associative polymers. We find that tyrosine is a stronger sticker than phenylalanine, whereas arginine is a context-dependent auxiliary sticker. In contrast, lysine weakens sticker-sticker interactions. Increasing the net charge per residue destabilizes phase separation while also weakening the strong coupling between single-chain contraction in dilute phases and multichain interactions that give rise to phase separation. Finally, glycine and serine residues act as non-equivalent spacers, and thus make the glycine versus serine contents an important determinant of the driving forces for phase separation. The totality of our results leads to a set of rules that enable comparative estimates of composition-specific driving forces for PLCD phase separation.
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Affiliation(s)
- Anne Bremer
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Mina Farag
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St Louis, St Louis, MO, USA
| | - Wade M Borcherds
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Ivan Peran
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Erik W Martin
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St Louis, St Louis, MO, USA.
| | - Tanja Mittag
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA.
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27
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Bremer A, Farag M, Borcherds WM, Peran I, Martin EW, Pappu RV, Mittag T. Deciphering how naturally occurring sequence features impact the phase behaviours of disordered prion-like domains. Nat Chem 2022; 14:196-207. [PMID: 34931046 DOI: 10.1101/2021.01.01.425046] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 10/19/2021] [Indexed: 05/25/2023]
Abstract
Prion-like low-complexity domains (PLCDs) have distinctive sequence grammars that determine their driving forces for phase separation. Here we uncover the physicochemical underpinnings of how evolutionarily conserved compositional biases influence the phase behaviour of PLCDs. We interpret our results in the context of the stickers-and-spacers model for the phase separation of associative polymers. We find that tyrosine is a stronger sticker than phenylalanine, whereas arginine is a context-dependent auxiliary sticker. In contrast, lysine weakens sticker-sticker interactions. Increasing the net charge per residue destabilizes phase separation while also weakening the strong coupling between single-chain contraction in dilute phases and multichain interactions that give rise to phase separation. Finally, glycine and serine residues act as non-equivalent spacers, and thus make the glycine versus serine contents an important determinant of the driving forces for phase separation. The totality of our results leads to a set of rules that enable comparative estimates of composition-specific driving forces for PLCD phase separation.
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Affiliation(s)
- Anne Bremer
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Mina Farag
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St Louis, St Louis, MO, USA
| | - Wade M Borcherds
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Ivan Peran
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Erik W Martin
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St Louis, St Louis, MO, USA.
| | - Tanja Mittag
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA.
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28
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Mittag T. Deciphering the link between evolutionarily conserved sequence features and the phase behavior of prion-like low-complexity domains. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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29
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Affiliation(s)
- Brian G O'Flynn
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
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30
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Martin EW, Harmon TS, Hopkins JB, Chakravarthy S, Incicco JJ, Schuck P, Soranno A, Mittag T. A multi-step nucleation process determines the kinetics of prion-like domain phase separation. Nat Commun 2021; 12:4513. [PMID: 34301955 PMCID: PMC8302766 DOI: 10.1038/s41467-021-24727-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 06/30/2021] [Indexed: 11/08/2022] Open
Abstract
Compartmentalization by liquid-liquid phase separation (LLPS) has emerged as a ubiquitous mechanism underlying the organization of biomolecules in space and time. Here, we combine rapid-mixing time-resolved small-angle X-ray scattering (SAXS) approaches to characterize the assembly kinetics of a prototypical prion-like domain with equilibrium techniques that characterize its phase boundaries and the size distribution of clusters prior to phase separation. We find two kinetic regimes on the micro- to millisecond timescale that are distinguished by the size distribution of clusters. At the nanoscale, small complexes are formed with low affinity. After initial unfavorable complex assembly, additional monomers are added with higher affinity. At the mesoscale, assembly resembles classical homogeneous nucleation. Careful multi-pronged characterization is required for the understanding of condensate assembly mechanisms and will promote understanding of how the kinetics of biological phase separation is encoded in biomolecules.
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Affiliation(s)
- Erik W Martin
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
| | - Tyler S Harmon
- The Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Jesse B Hopkins
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Srinivas Chakravarthy
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - J Jeremías Incicco
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, MO, USA
- Center for Science and Engineering of Living Cells (CSELS), Washington University in St. Louis, St. Louis, MO, USA
| | - Peter Schuck
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Andrea Soranno
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, MO, USA
- Center for Science and Engineering of Living Cells (CSELS), Washington University in St. Louis, St. Louis, MO, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
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31
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Abstract
A spectrum of cancers arises from chromosomal translocations that fuse receptor tyrosine kinase domains to oligomerization domains from unrelated proteins. Tulpule et al. (2021) demonstrate that fusion proteins with the ability to assemble higher-order cytoplasmic protein granules can activate RAS signaling in a lipid membrane-independent manner.
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Affiliation(s)
- Matthew J Cuneo
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
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32
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O'Flynn BG, Mittag T. The role of liquid-liquid phase separation in regulating enzyme activity. Curr Opin Cell Biol 2021; 69:70-79. [PMID: 33503539 PMCID: PMC8058252 DOI: 10.1016/j.ceb.2020.12.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [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: 10/21/2020] [Revised: 12/09/2020] [Accepted: 12/16/2020] [Indexed: 12/13/2022]
Abstract
Liquid-liquid phase separation (LLPS) is now recognized as a common mechanism underlying regulation of enzyme activity in cells. Insights from studies in cells are complemented by in vitro studies aimed at developing a better understanding of mechanisms underlying such control. These mechanisms are often based on the influence of LLPS on the physicochemical properties of the enzyme's environment. Biochemical mechanisms underlying such regulation include the potential for concentrating reactants together, tuning reaction rates, and controlling competing metabolic pathways. LLPS is thus a powerful tool with extensive utilities at the cell's disposal, e.g. for consolidating cell survival under stress or rerouting metabolic pathways in response to the energy state of the cell. Here, we examin the evidence for how LLPS affects enzyme catalysis and begin to understand emerging concepts and expand our understanding of enzyme catalysis in living cells.
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Affiliation(s)
- Brian G O'Flynn
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
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33
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Martin EW, Thomasen FE, Milkovic NM, Cuneo MJ, Grace C, Nourse A, Lindorff-Larsen K, Mittag T. Interplay of folded domains and the disordered low-complexity domain in mediating hnRNPA1 phase separation. Nucleic Acids Res 2021; 49:2931-2945. [PMID: 33577679 PMCID: PMC7969017 DOI: 10.1093/nar/gkab063] [Citation(s) in RCA: 63] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 12/29/2020] [Accepted: 01/29/2021] [Indexed: 01/24/2023] Open
Abstract
Liquid-liquid phase separation underlies the membrane-less compartmentalization of cells. Intrinsically disordered low-complexity domains (LCDs) often mediate phase separation, but how their phase behavior is modulated by folded domains is incompletely understood. Here, we interrogate the interplay between folded and disordered domains of the RNA-binding protein hnRNPA1. The LCD of hnRNPA1 is sufficient for mediating phase separation in vitro. However, we show that the folded RRM domains and a folded solubility-tag modify the phase behavior, even in the absence of RNA. Notably, the presence of the folded domains reverses the salt dependence of the driving force for phase separation relative to the LCD alone. Small-angle X-ray scattering experiments and coarse-grained MD simulations show that the LCD interacts transiently with the RRMs and/or the solubility-tag in a salt-sensitive manner, providing a mechanistic explanation for the observed salt-dependent phase separation. These data point to two effects from the folded domains: (i) electrostatically-mediated interactions that compact hnRNPA1 and contribute to phase separation and (ii) increased solubility at higher ionic strengths mediated by the folded domains. The interplay between disordered and folded domains can modify the dependence of phase behavior on solution conditions and can obscure signatures of physicochemical interactions underlying phase separation.
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Affiliation(s)
- Erik W Martin
- Department of Structural Biology, St. Jude Children's Research Hospital, TN 38105, USA
| | - F Emil Thomasen
- Structural Biology and NMR Laboratory, Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen N, 2200, Denmark
| | - Nicole M Milkovic
- Department of Structural Biology, St. Jude Children's Research Hospital, TN 38105, USA
| | - Matthew J Cuneo
- Department of Structural Biology, St. Jude Children's Research Hospital, TN 38105, USA
| | - Christy R Grace
- Department of Structural Biology, St. Jude Children's Research Hospital, TN 38105, USA
| | - Amanda Nourse
- Protein Technologies Center, Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Kresten Lindorff-Larsen
- Structural Biology and NMR Laboratory, Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen N, 2200, Denmark
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, TN 38105, USA
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34
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Farag M, Bremer A, Borcherds W, Mittag T, Pappu RV. How do Evolutionarily Encoded Compositional Biases Influence the Phase Behaviors of Intrinsically Disordered Low Complexity Domains of Proteins? Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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35
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Bremer A, Farag M, Borcherds WM, Pappu RV, Mittag T. Hidden Complexities in the Phase Behavior of Low-Complexity Disordered Proteins. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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36
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Martin EW, Harmon TS, Hopkins JB, Chakravarthy S, Incicco J, Schuck P, Soranno A, Mittag T. Kinetic and Equilibrium Measurement of Nucleation of Prion-Like Domain Phase Separation. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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37
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Gradinaru CC, Gomes GW, Mittag T, Head-Gordon TL, Forman-Kay JD. Integrating NMR, SAXS and Single-Molecule FRET Data to Infer Conformational Ensembles of the Yeast Sic1 Protein. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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38
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Borcherds WM, Bremer A, Farag M, Peran I, Martin EW, Pappu RV, Mittag T. Exploring the Effects of Increased Charge Content on the Phase Behavior of a Protein Low Complexity Domain. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.1962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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39
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Lazar T, Martínez-Pérez E, Quaglia F, Hatos A, Chemes L, Iserte JA, Méndez NA, Garrone NA, Saldaño T, Marchetti J, Rueda A, Bernadó P, Blackledge M, Cordeiro TN, Fagerberg E, Forman-Kay JD, Fornasari M, Gibson TJ, Gomes GNW, Gradinaru C, Head-Gordon T, Jensen MR, Lemke E, Longhi S, Marino-Buslje C, Minervini G, Mittag T, Monzon A, Pappu RV, Parisi G, Ricard-Blum S, Ruff KM, Salladini E, Skepö M, Svergun D, Vallet S, Varadi M, Tompa P, Tosatto SCE, Piovesan D. PED in 2021: a major update of the protein ensemble database for intrinsically disordered proteins. Nucleic Acids Res 2021; 49:D404-D411. [PMID: 33305318 PMCID: PMC7778965 DOI: 10.1093/nar/gkaa1021] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 10/13/2020] [Accepted: 12/08/2020] [Indexed: 12/21/2022] Open
Abstract
The Protein Ensemble Database (PED) (https://proteinensemble.org), which holds structural ensembles of intrinsically disordered proteins (IDPs), has been significantly updated and upgraded since its last release in 2016. The new version, PED 4.0, has been completely redesigned and reimplemented with cutting-edge technology and now holds about six times more data (162 versus 24 entries and 242 versus 60 structural ensembles) and a broader representation of state of the art ensemble generation methods than the previous version. The database has a completely renewed graphical interface with an interactive feature viewer for region-based annotations, and provides a series of descriptors of the qualitative and quantitative properties of the ensembles. High quality of the data is guaranteed by a new submission process, which combines both automatic and manual evaluation steps. A team of biocurators integrate structured metadata describing the ensemble generation methodology, experimental constraints and conditions. A new search engine allows the user to build advanced queries and search all entry fields including cross-references to IDP-related resources such as DisProt, MobiDB, BMRB and SASBDB. We expect that the renewed PED will be useful for researchers interested in the atomic-level understanding of IDP function, and promote the rational, structure-based design of IDP-targeting drugs.
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Affiliation(s)
- Tamas Lazar
- VIB-VUB Center for Structural Biology, Flanders Institute for Biotechnology, Brussels 1050, Belgium
- Structural Biology Brussels, Bioengineering Sciences Department, Vrije Universiteit Brussel, Brussels 1050, Belgium
| | - Elizabeth Martínez-Pérez
- Bioinformatics Unit, Fundación Instituto Leloir, Buenos Aires, C1405BWE, Argentina
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Federica Quaglia
- Dept. of Biomedical Sciences, University of Padua, Padova 35131, Italy
| | - András Hatos
- Dept. of Biomedical Sciences, University of Padua, Padova 35131, Italy
| | - Lucía B Chemes
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde’’, IIB-UNSAM, IIBIO-CONICET, Universidad Nacional de SanMartín, CP1650 San Martín, Buenos Aires, Argentina
| | - Javier A Iserte
- Bioinformatics Unit, Fundación Instituto Leloir, Buenos Aires, C1405BWE, Argentina
| | - Nicolás A Méndez
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde’’, IIB-UNSAM, IIBIO-CONICET, Universidad Nacional de SanMartín, CP1650 San Martín, Buenos Aires, Argentina
| | - Nicolás A Garrone
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde’’, IIB-UNSAM, IIBIO-CONICET, Universidad Nacional de SanMartín, CP1650 San Martín, Buenos Aires, Argentina
| | - Tadeo E Saldaño
- Laboratorio de Química y Biología Computacional, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal B1876BXD, Buenos Aires, Argentina
| | - Julia Marchetti
- Laboratorio de Química y Biología Computacional, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal B1876BXD, Buenos Aires, Argentina
| | - Ana Julia Velez Rueda
- Laboratorio de Química y Biología Computacional, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal B1876BXD, Buenos Aires, Argentina
| | - Pau Bernadó
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, University of Montpellier, Montpellier 34090, France
| | | | - Tiago N Cordeiro
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, University of Montpellier, Montpellier 34090, France
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras 2780-157, Portugal
| | - Eric Fagerberg
- Theoretical Chemistry, Lund University, Lund, POB 124, SE-221 00, Sweden
| | - Julie D Forman-Kay
- Molecular Medicine Program, Hospital for Sick Children, Toronto, M5G 1X8, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, M5S 1A8, Ontario, Canada
| | - Maria S Fornasari
- Laboratorio de Química y Biología Computacional, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal B1876BXD, Buenos Aires, Argentina
| | - Toby J Gibson
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Gregory-Neal W Gomes
- Department of Physics, University of Toronto, Toronto, M5S 1A7, Ontario, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, L5L 1C6, Ontario, Canada
| | - Claudiu C Gradinaru
- Department of Physics, University of Toronto, Toronto, M5S 1A7, Ontario, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, L5L 1C6, Ontario, Canada
| | - Teresa Head-Gordon
- Departments of Chemistry, Bioengineering, Chemical and Biomolecular Engineering University of California, Berkeley, CA 94720, USA
| | | | - Edward A Lemke
- Biocentre, Johannes Gutenberg-University Mainz, Mainz 55128, Germany
- Institute of Molecular Biology, Mainz 55128, Germany
| | - Sonia Longhi
- Aix-Marseille University, CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Marseille 13288, France
| | | | | | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | | | - Rohit V Pappu
- Department of Biomedical Engineering, Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, MO 63130, USA
| | - Gustavo Parisi
- Laboratorio de Química y Biología Computacional, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal B1876BXD, Buenos Aires, Argentina
| | - Sylvie Ricard-Blum
- Univ Lyon, University Claude Bernard Lyon 1, CNRS, INSA Lyon, CPE, Institute of Molecular and Supramolecular Chemistry and Biochemistry (ICBMS), UMR 5246, Villeurbanne, 69629 Lyon Cedex 07, France
| | - Kiersten M Ruff
- Department of Biomedical Engineering, Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, MO 63130, USA
| | - Edoardo Salladini
- Aix-Marseille University, CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Marseille 13288, France
| | - Marie Skepö
- Theoretical Chemistry, Lund University, Lund, POB 124, SE-221 00, Sweden
- LINXS - Lund Institute of Advanced Neutron and X-ray Science, Lund 223 70, Sweden
| | - Dmitri Svergun
- European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22607, Germany
| | - Sylvain D Vallet
- Univ Lyon, University Claude Bernard Lyon 1, CNRS, INSA Lyon, CPE, Institute of Molecular and Supramolecular Chemistry and Biochemistry (ICBMS), UMR 5246, Villeurbanne, 69629 Lyon Cedex 07, France
| | - Mihaly Varadi
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, CB10 1SD, UK
| | - Peter Tompa
- To whom correspondence should be addressed. Tel +32 473 785386;
| | - Silvio C E Tosatto
- Correspondence may also be addressed to Silvio C. E. Tosatto. Tel: +39 049 827 6269;
| | - Damiano Piovesan
- Dept. of Biomedical Sciences, University of Padua, Padova 35131, Italy
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40
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Yang P, Mathieu C, Kolaitis RM, Zhang P, Messing J, Yurtsever U, Yang Z, Wu J, Li Y, Pan Q, Yu J, Martin EW, Mittag T, Kim HJ, Taylor JP. G3BP1 Is a Tunable Switch that Triggers Phase Separation to Assemble Stress Granules. Cell 2020; 181:325-345.e28. [PMID: 32302571 DOI: 10.1016/j.cell.2020.03.046] [Citation(s) in RCA: 568] [Impact Index Per Article: 142.0] [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: 01/29/2019] [Revised: 10/23/2019] [Accepted: 03/20/2020] [Indexed: 12/18/2022]
Abstract
The mechanisms underlying ribonucleoprotein (RNP) granule assembly, including the basis for establishing and maintaining RNP granules with distinct composition, are unknown. One prominent type of RNP granule is the stress granule (SG), a dynamic and reversible cytoplasmic assembly formed in eukaryotic cells in response to stress. Here, we show that SGs assemble through liquid-liquid phase separation (LLPS) arising from interactions distributed unevenly across a core protein-RNA interaction network. The central node of this network is G3BP1, which functions as a molecular switch that triggers RNA-dependent LLPS in response to a rise in intracellular free RNA concentrations. Moreover, we show that interplay between three distinct intrinsically disordered regions (IDRs) in G3BP1 regulates its intrinsic propensity for LLPS, and this is fine-tuned by phosphorylation within the IDRs. Further regulation of SG assembly arises through positive or negative cooperativity by extrinsic G3BP1-binding factors that strengthen or weaken, respectively, the core SG network.
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Affiliation(s)
- Peiguo Yang
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Cécile Mathieu
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Regina-Maria Kolaitis
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Peipei Zhang
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - James Messing
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Ugur Yurtsever
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Graduate School of Structure and Dynamics of Living Systems, Université Paris-Saclay, Gif-sur-Yvette, 91190, France
| | - Zemin Yang
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jinjun Wu
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Yuxin Li
- Center for Proteomics and Metabolomics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Qingfei Pan
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jiyang Yu
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Erik W Martin
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Hong Joo Kim
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - J Paul Taylor
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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41
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Abstract
Liquid-liquid phase separation plays important roles in the compartmentalization of cells. Developing an understanding of how phase separation is encoded in biomacromolecules requires quantitative mapping of their phase behavior. Given that such experiments require large quantities of the biomolecule of interest, these efforts have been lagging behind the recent breadth of biological insights. Herein, we present a microfluidic phase chip that enables the measurement of saturation concentrations over at least three orders of magnitude for a broad spectrum of biomolecules and solution conditions. The phase chip consists of five units, each made of twenty individual sample chambers to allow the measurement of five sample conditions simultaneously. The analytes are slowly concentrated via evaporation of water, which is replaced by oil, until the sample undergoes phase separation into a dilute and dense phase. We show that the phase chip lowers the required sample quantity by 98% while offering six-fold better statistics in comparison to standard manual experiments that involve centrifugal separation of dilute and dense phases. We further show that the saturation concentrations measured in chips are in agreement with previously reported data for a variety of biomolecules. Concomitantly, time-dependent changes of the dense phase morphology and potential off-pathway processes, including aggregation, can be monitored microscopically. In summary, the phase chip is suited to exploring sequence-to-binodal relationships by enabling the determination of a large number of saturation concentrations at low protein cost.
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Affiliation(s)
- Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital Memphis, TN, USA.
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital Memphis, TN, USA.
| | - Michael Heymann
- Institute for Biomaterials and Biomolecular Systems, University Stuttgart, Germany.
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42
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Borcherds W, Bremer A, Borgia MB, Mittag T. How do intrinsically disordered protein regions encode a driving force for liquid-liquid phase separation? Curr Opin Struct Biol 2020; 67:41-50. [PMID: 33069007 DOI: 10.1016/j.sbi.2020.09.004] [Citation(s) in RCA: 118] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/02/2020] [Accepted: 09/07/2020] [Indexed: 12/24/2022]
Abstract
Liquid-liquid phase separation is the mechanism underlying the formation of biomolecular condensates. Disordered protein regions often drive phase separation, but the molecular interactions mediating this phenomenon are not well understood, sometimes leading to the conflation that all disordered protein regions drive phase separation. Given the critical role of phase separation in many cellular processes, and that dysfunction of phase separation can lead to debilitating diseases, it is important that we understand the interactions and sequence properties underlying phase behavior. A conceptual framework that divides IDRs into interacting and solvating regions has proven particularly useful, and analytical instantiations and coarse-grained models can test our understanding of the driving forces against experimental phase behavior. Validated simulation paradigms enable the exploration of sequence space to help our understanding of how disordered protein regions can encode phase behavior, which IDRs may mediate phase separation in cells, and which IDRs are highly soluble.
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Affiliation(s)
- Wade Borcherds
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Madeleine B Borgia
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
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43
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Gomes GNW, Krzeminski M, Namini A, Martin EW, Mittag T, Head-Gordon T, Forman-Kay JD, Gradinaru CC. Conformational Ensembles of an Intrinsically Disordered Protein Consistent with NMR, SAXS, and Single-Molecule FRET. J Am Chem Soc 2020; 142:15697-15710. [PMID: 32840111 PMCID: PMC9987321 DOI: 10.1021/jacs.0c02088] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Intrinsically disordered proteins (IDPs) have fluctuating heterogeneous conformations, which makes their structural characterization challenging. Although challenging, characterization of the conformational ensembles of IDPs is of great interest, since their conformational ensembles are the link between their sequences and functions. An accurate description of IDP conformational ensembles depends crucially on the amount and quality of the experimental data, how it is integrated, and if it supports a consistent structural picture. We used integrative modeling and validation to apply conformational restraints and assess agreement with the most common structural techniques for IDPs: Nuclear Magnetic Resonance (NMR) spectroscopy, Small-angle X-ray Scattering (SAXS), and single-molecule Förster Resonance Energy Transfer (smFRET). Agreement with such a diverse set of experimental data suggests that details of the generated ensembles can now be examined with a high degree of confidence. Using the disordered N-terminal region of the Sic1 protein as a test case, we examined relationships between average global polymeric descriptions and higher-moments of their distributions. To resolve apparent discrepancies between smFRET and SAXS inferences, we integrated SAXS data with NMR data and reserved the smFRET data for independent validation. Consistency with smFRET, which was not guaranteed a priori, indicates that, globally, the perturbative effects of NMR or smFRET labels on the Sic1 ensemble are minimal. Analysis of the ensembles revealed distinguishing features of Sic1, such as overall compactness and large end-to-end distance fluctuations, which are consistent with biophysical models of Sic1's ultrasensitive binding to its partner Cdc4. Our results underscore the importance of integrative modeling and validation in generating and drawing conclusions from IDP conformational ensembles.
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Affiliation(s)
- Gregory-Neal W Gomes
- Department of Physics, University of Toronto, Toronto, Ontario M5G 1X8, Canada.,Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Mickaël Krzeminski
- Molecular Medicine Program, Hospital for Sick Children, Toronto, Ontario M5S 1A8, Canada.,Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1X8, Canada
| | - Ashley Namini
- Department of Physics, University of Toronto, Toronto, Ontario M5G 1X8, Canada.,Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Erik W Martin
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, United States
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, United States
| | - Teresa Head-Gordon
- Departments of Chemistry, Bioengineering, Chemical and Biomolecular Engineering University of California, Berkeley, California 94720, United States
| | - Julie D Forman-Kay
- Molecular Medicine Program, Hospital for Sick Children, Toronto, Ontario M5S 1A8, Canada.,Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1X8, Canada
| | - Claudiu C Gradinaru
- Department of Physics, University of Toronto, Toronto, Ontario M5G 1X8, Canada.,Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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44
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Martin EW, Hopkins JB, Mittag T. Small-angle X-ray scattering experiments of monodisperse intrinsically disordered protein samples close to the solubility limit. Methods Enzymol 2020; 646:185-222. [PMID: 33453925 PMCID: PMC8370720 DOI: 10.1016/bs.mie.2020.07.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [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] [Indexed: 01/05/2023]
Abstract
The condensation of biomolecules into biomolecular condensates via liquid-liquid phase separation (LLPS) is a ubiquitous mechanism that drives cellular organization. To enable these functions, biomolecules have evolved to drive LLPS and facilitate partitioning into biomolecular condensates. Determining the molecular features of proteins that encode LLPS will provide critical insights into a plethora of biological processes. Problematically, probing biomolecular dense phases directly is often technologically difficult or impossible. By capitalizing on the symmetry between the conformational behavior of biomolecules in dilute solution and dense phases, it is possible to infer details critical to phase separation by precise measurements of the dilute phase thus circumventing complicated characterization of dense phases. The symmetry between dilute and dense phases is found in the size and shape of the conformational ensemble of a biomolecule-parameters that small-angle X-ray scattering (SAXS) is ideally suited to probe. Recent technological advances have made it possible to accurately characterize samples of intrinsically disordered protein regions at low enough concentration to avoid interference from intermolecular attraction, oligomerization or aggregation, all of which were previously roadblocks to characterizing self-assembling proteins. Herein, we describe the pitfalls inherent to measuring such samples, the experimental details required for circumventing these issues and analysis methods that place the results of SAXS measurements into the theoretical framework of LLPS.
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Affiliation(s)
- Erik W Martin
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - Jesse B Hopkins
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, United States
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, United States.
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Zeng X, Holehouse AS, Chilkoti A, Mittag T, Pappu RV. Connecting Coil-to-Globule Transitions to Full Phase Diagrams for Intrinsically Disordered Proteins. Biophys J 2020; 119:402-418. [PMID: 32619404 PMCID: PMC7376131 DOI: 10.1016/j.bpj.2020.06.014] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 06/09/2020] [Accepted: 06/11/2020] [Indexed: 01/09/2023] Open
Abstract
Phase separation is thought to underlie spatial and temporal organization that is required for controlling biochemical reactions in cells. Multivalence of interaction motifs, also known as stickers, is a defining feature of proteins that drive phase separation. Intrinsically disordered proteins with stickers uniformly distributed along the linear sequence can serve as scaffold molecules that drive phase separation. The sequence-intrinsic contributions of disordered proteins to phase separation can be discerned by computing or measuring sequence-specific phase diagrams. These help to delineate the combinations of protein concentration and a suitable control parameter, such as temperature, that support phase separation. Here, we present an approach that combines detailed simulations with a numerical adaptation of an analytical Gaussian cluster theory to enable the calculation of sequence-specific phase diagrams. Our approach leverages the known equivalence between the driving forces for single-chain collapse in dilute solutions and the driving forces for phase separation in concentrated solutions. We demonstrate the application of the theory-aided computations through calculation of phase diagrams for a set of archetypal intrinsically disordered low-complexity domains. We also leverage theories to compute sequence-specific percolation lines and thereby provide a thermodynamic framework for hardening transitions that have been observed for many biomolecular condensates.
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Affiliation(s)
- Xiangze Zeng
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri; Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, Missouri
| | - Alex S Holehouse
- Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, Missouri; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri; Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, Missouri.
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Martin EW, Holehouse AS, Peran I, Farag M, Incicco JJ, Bremer A, Grace CR, Soranno A, Pappu RV, Mittag T. Valence and patterning of aromatic residues determine the phase behavior of prion-like domains. Science 2020; 367:694-699. [PMID: 32029630 PMCID: PMC7297187 DOI: 10.1126/science.aaw8653] [Citation(s) in RCA: 498] [Impact Index Per Article: 124.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 08/30/2019] [Accepted: 01/06/2020] [Indexed: 12/12/2022]
Abstract
Prion-like domains (PLDs) can drive liquid-liquid phase separation (LLPS) in cells. Using an integrative biophysical approach that includes nuclear magnetic resonance spectroscopy, small-angle x-ray scattering, and multiscale simulations, we have uncovered sequence features that determine the overall phase behavior of PLDs. We show that the numbers (valence) of aromatic residues in PLDs determine the extent of temperature-dependent compaction of individual molecules in dilute solutions. The valence of aromatic residues also determines full binodals that quantify concentrations of PLDs within coexisting dilute and dense phases as a function of temperature. We also show that uniform patterning of aromatic residues is a sequence feature that promotes LLPS while inhibiting aggregation. Our findings lead to the development of a numerical stickers-and-spacers model that enables predictions of full binodals of PLDs from their sequences.
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Affiliation(s)
- Erik W Martin
- Department of Structural Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Alex S Holehouse
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Ivan Peran
- Department of Structural Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Mina Farag
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - J Jeremias Incicco
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Anne Bremer
- Department of Structural Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Christy R Grace
- Department of Structural Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Andrea Soranno
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
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Usher GA, Rohac R, Sabri N, Mittag T, Boal AK, Showalter SA. Insights into SPOP-Substrate Behavior through Studies of Pdx1-SPOP Interactions. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Gomes GW, Krzeminski M, Martin EW, Mittag T, Forman-Kay JD, Gradinaru CC. Structure and Function Implications of Conformational Ensembles Consistent with NMR, SAXS, and smFRET Data. The Disordered Protein SIC1 Before and After Multisite Phosphorylation. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Abstract
Biomolecular condensates are emerging as an important organizational principle within living cells. These condensed states are formed by phase separation, yet little is known about how material properties are encoded within the constituent molecules and how the specificity for being in different phases is established. Here we use analytic theory to explain the phase behavior of the cancer-related protein SPOP and its substrate DAXX. Binary mixtures of these molecules have a phase diagram that contains dilute liquid, dense liquid, and gel states. We show that these discrete phases appear due to a competition between SPOP-DAXX and DAXX-DAXX interactions. The stronger SPOP-DAXX interactions dominate at sub-stoichiometric DAXX concentrations leading to the formation of cross-linked gels. The theory shows that the driving force for gel formation is not the binding energy, but rather the entropy of distributing DAXX molecules on the binding sites. At high DAXX concentrations the SPOP-DAXX interactions saturate, which leads to the dissolution of the gel and the appearance of a liquid phase driven by weaker DAXX-DAXX interactions. This competition between interactions allows multiple dense phases to form in a narrow region of parameter space. We propose that the molecular architecture of phase-separating proteins governs the internal structure of dense phases, their material properties and their functions. Analytical theory can reveal these properties on the long length and time scales relevant to biomolecular condensates.
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Affiliation(s)
- Jeremy D Schmit
- Department of Physics , Kansas State University , Manhattan , Kansas 66506 , United States
| | - Jill J Bouchard
- Department of Structural Biology , St. Jude Children's Research Hospital , Memphis , Tennessee 38105 , United States
| | - Erik W Martin
- Department of Structural Biology , St. Jude Children's Research Hospital , Memphis , Tennessee 38105 , United States
| | - Tanja Mittag
- Department of Structural Biology , St. Jude Children's Research Hospital , Memphis , Tennessee 38105 , United States
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Abstract
Liquid-liquid phase separation (LLPS) underlies the formation of biomolecular condensates, i.e., membrane-less compartments in cells that carry out functions related to RNA metabolism, stress adaptation, transport, or signaling. Examples of such biomolecular condensates are the nucleolus, nuclear speckles, promyelocytic leukemia protein (PML) bodies and paraspeckles in the nucleus, and stress granules and P bodies in the cytoplasm. Other structures in cells that are not typically viewed as bona fide compartments also seem to be formed via LLPS as recently elucidated, including heterochromatin, super-enhancers, and membrane receptor clusters. Key protein and/or RNA components of these biomolecular condensates form a scaffold via LLPS. Other constituents incorporate into this scaffold as clients. To understand the sequence features and interactions that mediate biomolecular condensate formation in cells, it is useful to quantify phase separation of pure components in vitro. Microscopy and turbidity measurements can be used to determine the concentration of a protein above which it phase separates, the so-called saturation concentration. Here, we describe experiments for the determination of full coexistence lines of phase-separating proteins by centrifugation. Coexistence lines are reconstructed from coexisting light and dense phase concentrations of the protein, and we present them as so-called phase diagrams. Phase diagrams allow the quantitative comparison of phase separation for proteins and their mutants under different conditions. They are thus important for our nuanced understanding of the driving forces underlying liquid-liquid phase separation in vitro. Such results have direct applicability for understanding phase separation-driven compartmentalization of cells.
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Affiliation(s)
- Nicole M Milkovic
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
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