1151
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Mangan H, Gailín MÓ, McStay B. Integrating the genomic architecture of human nucleolar organizer regions with the biophysical properties of nucleoli. FEBS J 2017; 284:3977-3985. [PMID: 28500793 DOI: 10.1111/febs.14108] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 04/21/2017] [Accepted: 05/10/2017] [Indexed: 11/30/2022]
Abstract
Nucleoli are the sites of ribosome biogenesis and the largest membraneless subnuclear structures. They are intimately linked with growth and proliferation control and function as sensors of cellular stress. Nucleoli form around arrays of ribosomal gene (rDNA) repeats also called nucleolar organizer regions (NORs). In humans, NORs are located on the short arms of all five human acrocentric chromosomes. Multiple NORs contribute to the formation of large heterochromatin-surrounded nucleoli observed in most human cells. Here we will review recent findings about their genomic architecture. The dynamic nature of nucleoli began to be appreciated with the advent of photodynamic experiments using fluorescent protein fusions. We review more recent data on nucleoli in Xenopus germinal vesicles (GVs) which has revealed a liquid droplet-like behavior that facilitates nucleolar fusion. Further analysis in both XenopusGVs and Drosophila embryos indicates that the internal organization of nucleoli is generated by a combination of liquid-liquid phase separation and active processes involving rDNA. We will attempt to integrate these recent findings with the genomic architecture of human NORs to advance our understanding of how nucleoli form and respond to stress in human cells.
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Affiliation(s)
- Hazel Mangan
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Michael Ó Gailín
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Brian McStay
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland
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1152
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Simon JR, Carroll NJ, Rubinstein M, Chilkoti A, López GP. Programming molecular self-assembly of intrinsically disordered proteins containing sequences of low complexity. Nat Chem 2017; 9:509-515. [PMID: 28537592 PMCID: PMC5597244 DOI: 10.1038/nchem.2715] [Citation(s) in RCA: 215] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 11/17/2016] [Indexed: 12/22/2022]
Abstract
Dynamic protein-rich intracellular structures that contain phase-separated intrinsically disordered proteins (IDPs) composed of sequences of low complexity (SLC) have been shown to serve a variety of important cellular functions, which include signalling, compartmentalization and stabilization. However, our understanding of these structures and our ability to synthesize models of them have been limited. We present design rules for IDPs possessing SLCs that phase separate into diverse assemblies within droplet microenvironments. Using theoretical analyses, we interpret the phase behaviour of archetypal IDP sequences and demonstrate the rational design of a vast library of multicomponent protein-rich structures that ranges from uniform nano-, meso- and microscale puncta (distinct protein droplets) to multilayered orthogonally phase-separated granular structures. The ability to predict and program IDP-rich assemblies in this fashion offers new insights into (1) genetic-to-molecular-to-macroscale relationships that encode hierarchical IDP assemblies, (2) design rules of such assemblies in cell biology and (3) molecular-level engineering of self-assembled recombinant IDP-rich materials.
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Affiliation(s)
- Joseph R. Simon
- NSF Research Triangle Materials Research Science and Engineering Center, Duke University, Durham, North Carolina 27708, USA
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
| | - Nick J. Carroll
- NSF Research Triangle Materials Research Science and Engineering Center, Duke University, Durham, North Carolina 27708, USA
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Michael Rubinstein
- NSF Research Triangle Materials Research Science and Engineering Center, Duke University, Durham, North Carolina 27708, USA
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Ashutosh Chilkoti
- NSF Research Triangle Materials Research Science and Engineering Center, Duke University, Durham, North Carolina 27708, USA
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
| | - Gabriel P. López
- NSF Research Triangle Materials Research Science and Engineering Center, Duke University, Durham, North Carolina 27708, USA
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131, USA
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
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1153
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Lin YH, Chan HS. Phase Separation and Single-Chain Compactness of Charged Disordered Proteins Are Strongly Correlated. Biophys J 2017; 112:2043-2046. [PMID: 28483149 DOI: 10.1016/j.bpj.2017.04.021] [Citation(s) in RCA: 158] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 04/17/2017] [Accepted: 04/18/2017] [Indexed: 01/10/2023] Open
Abstract
Liquid-liquid phase separation of intrinsically disordered proteins (IDPs) is a major undergirding factor in the regulated formation of membraneless organelles in the cell. The phase behavior of an IDP is sensitive to its amino acid sequence. Here we apply a recent random-phase-approximation polymer theory to investigate how the tendency for multiple chains of a protein to phase-separate, as characterized by the critical temperature T∗cr, is related to the protein's single-chain average radius of gyration 〈Rg〉. For a set of sequences containing different permutations of an equal number of positively and negatively charged residues, we found a striking correlation T∗cr ∼ 〈Rg〉-γ with γ as large as ∼6.0, indicating that electrostatic effects have similarly significant impact on promoting single-chain conformational compactness and phase separation. Moreover, T∗cr ∝ -SCD, where SCD is a recently proposed "sequence charge decoration" parameter determined solely by sequence information. Ramifications of our findings for deciphering the sequence dependence of IDP phase separation are discussed.
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Affiliation(s)
- Yi-Hsuan Lin
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Hue Sun Chan
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
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1154
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Banani SF, Lee HO, Hyman AA, Rosen MK. Biomolecular condensates: organizers of cellular biochemistry. Nat Rev Mol Cell Biol 2017; 18:285-298. [PMID: 28225081 PMCID: PMC7434221 DOI: 10.1038/nrm.2017.7] [Citation(s) in RCA: 3162] [Impact Index Per Article: 451.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biomolecular condensates are micron-scale compartments in eukaryotic cells that lack surrounding membranes but function to concentrate proteins and nucleic acids. These condensates are involved in diverse processes, including RNA metabolism, ribosome biogenesis, the DNA damage response and signal transduction. Recent studies have shown that liquid-liquid phase separation driven by multivalent macromolecular interactions is an important organizing principle for biomolecular condensates. With this physical framework, it is now possible to explain how the assembly, composition, physical properties and biochemical and cellular functions of these important structures are regulated.
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Affiliation(s)
- Salman F. Banani
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Hyun O. Lee
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Anthony A. Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Michael K. Rosen
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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1155
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Nucleolar reorganization in response to rDNA damage. Curr Opin Cell Biol 2017; 46:81-86. [PMID: 28431265 DOI: 10.1016/j.ceb.2017.03.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/06/2017] [Accepted: 03/07/2017] [Indexed: 11/24/2022]
Abstract
Nucleoli, sites of ribosome biogenesis, form around nucleolar organizer regions (NORs) comprising rDNA arrays, located on human acrocentric chromosome p-arms. NORs provide an opportunity to investigate the DNA double strand break (DSB) response at highly transcribed, repetitive, essential loci. Targeted introduction of DSBs into rDNA results in ATM-dependent inhibition of RNA-polymerase I transcription, coupled with movement of rDNA from the nucleolar interior to anchoring points at the periphery. Reorganization renders rDNA accessible to repair factors, normally excluded from nucleoli. Importantly, rDNA DSBs recruit the accurate homologous recombination (HR) repair machinery throughout the cell cycle, suggesting that HR can be templated in cis. We discuss recent findings regarding the biophysical properties of nucleoli and suggest a mechanism for stress-induced nucleolar reorganization.
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1156
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Rai U, Najm F, Tartakoff AM. Nucleolar asymmetry and the importance of septin integrity upon cell cycle arrest. PLoS One 2017; 12:e0174306. [PMID: 28339487 PMCID: PMC5365125 DOI: 10.1371/journal.pone.0174306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 03/07/2017] [Indexed: 12/31/2022] Open
Abstract
Cell cycle arrest can be imposed by inactivating the anaphase promoting complex (APC). In S. cerevisiae this arrest has been reported to stabilize a metaphase-like intermediate in which the nuclear envelope spans the bud neck, while chromatin repeatedly translocates between the mother and bud domains. The present investigation was undertaken to learn how other features of nuclear organization are affected upon depletion of the APC activator, Cdc20. We observe that the spindle pole bodies and the spindle repeatedly translocate across the narrow orifice at the level of the neck. Nevertheless, we find that the nucleolus (organized around rDNA repeats on the long right arm of chromosome XII) remains in the mother domain, marking the polarity of the nucleus. Accordingly, chromosome XII is polarized: TelXIIR remains in the mother domain and its centromere is predominantly located in the bud domain. In order to learn why the nucleolus remains in the mother domain, we studied the impact of inhibiting rRNA synthesis in arrested cells. We observed that this fragments the nucleolus and that these fragments entered the bud domain. Taken together with earlier observations, the restriction of the nucleolus to the mother domain therefore can be attributed to its massive structure. We also observed that inactivation of septins allowed arrested cells to complete the cell cycle, that the alternative APC activator, Cdh1, was required for completion of the cell cycle and that induction of Cdh1 itself caused arrested cells to progress to the end of the cell cycle.
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Affiliation(s)
- Urvashi Rai
- Cell Biology Program/Department of Molecular and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Fadi Najm
- Division of Medical Sciences, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Alan M. Tartakoff
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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1157
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Weber SC. Sequence-encoded material properties dictate the structure and function of nuclear bodies. Curr Opin Cell Biol 2017; 46:62-71. [PMID: 28343140 DOI: 10.1016/j.ceb.2017.03.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 02/13/2017] [Accepted: 03/07/2017] [Indexed: 12/21/2022]
Abstract
Concomitant with packaging the genome, the cell nucleus must also spatially organize the nucleoplasm. This complex mixture of proteins and nucleic acids partitions into a variety of phase-separated, membraneless organelles called nuclear bodies. Significant progress has been made in understanding the relationship between the material properties of nuclear bodies and their structural and functional consequences. Furthermore, the molecular basis of these condensed phases is beginning to emerge. Here, I review the latest work in this exciting field, highlighting recent advances and new challenges.
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Affiliation(s)
- Stephanie C Weber
- Department of Biology, McGill University, Montreal, QC H3A 1B1, Canada.
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1158
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Computational and theoretical advances in studies of intrinsically disordered proteins. Curr Opin Struct Biol 2017; 42:147-154. [PMID: 28259050 DOI: 10.1016/j.sbi.2017.01.006] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 01/16/2017] [Accepted: 01/21/2017] [Indexed: 01/08/2023]
Abstract
Intrinsically disordered proteins (IDPs) are increasingly realized to play diverse biological roles, ranging from molecular signaling to the formation of membraneless organelles. Their high degree of disorder makes them more challenging to study using the techniques of conventional structural biology, because any observable will be averaged over a heterogeneous ensemble of structures. Molecular simulations and theory are therefore a natural complement to experiment for studying the structure, dynamics and function of IDPs. The diverse time and length scales relevant to the roles played by IDPs require flexibility in the techniques applied. Here, I summarize some of the developments in simulation and theory in recent years, which have been driven by the desire to better capture IDP properties at different time- and length-scales. I also provide an outlook for how methods can be improved in the future and emerging problems which may be addressed by theory and simulation.
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1159
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Jacobs WM, Frenkel D. Phase Transitions in Biological Systems with Many Components. Biophys J 2017; 112:683-691. [PMID: 28256228 PMCID: PMC5340130 DOI: 10.1016/j.bpj.2016.10.043] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 10/24/2016] [Accepted: 10/28/2016] [Indexed: 10/20/2022] Open
Abstract
Biological mixtures such as the cytosol may consist of thousands of distinct components. There is now a substantial body of evidence showing that, under physiological conditions, intracellular mixtures can phase separate into spatially distinct regions with differing compositions. In this article we present numerical evidence indicating that such spontaneous compartmentalization exploits general features of the phase diagram of a multicomponent biomolecular mixture. In particular, we show that demixed domains are likely to segregate when the variance in the intermolecular interaction strengths exceeds a well-defined threshold. Multiple distinct phases are likely to become stable under very similar conditions, which can then be tuned to achieve multiphase coexistence. As a result, only minor adjustments to the composition of the cytosol or the strengths of the intermolecular interactions are needed to regulate the formation of different domains with specific compositions, implying that phase separation is a robust mechanism for creating spatial organization. We further predict that this functionality is only weakly affected by increasing the number of components in the system. Our model therefore suggests that, for purely physico-chemical reasons, biological mixtures are naturally poised to undergo a small number of demixing phase transitions.
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Affiliation(s)
- William M Jacobs
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
| | - Daan Frenkel
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
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1160
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Mahynski NA, Blanco MA, Errington JR, Shen VK. Predicting low-temperature free energy landscapes with flat-histogram Monte Carlo methods. J Chem Phys 2017; 146:074101. [PMID: 28228029 DOI: 10.1063/1.4975331] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We present a method for predicting the free energy landscape of fluids at low temperatures from flat-histogram grand canonical Monte Carlo simulations performed at higher ones. We illustrate our approach for both pure and multicomponent systems using two different sampling methods as a demonstration. This allows us to predict the thermodynamic behavior of systems which undergo both first order and continuous phase transitions upon cooling using simulations performed only at higher temperatures. After surveying a variety of different systems, we identify a range of temperature differences over which the extrapolation of high temperature simulations tends to quantitatively predict the thermodynamic properties of fluids at lower ones. Beyond this range, extrapolation still provides a reasonably well-informed estimate of the free energy landscape; this prediction then requires less computational effort to refine with an additional simulation at the desired temperature than reconstruction of the surface without any initial estimate. In either case, this method significantly increases the computational efficiency of these flat-histogram methods when investigating thermodynamic properties of fluids over a wide range of temperatures. For example, we demonstrate how a binary fluid phase diagram may be quantitatively predicted for many temperatures using only information obtained from a single supercritical state.
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Affiliation(s)
- Nathan A Mahynski
- Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8320, USA
| | - Marco A Blanco
- Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8320, USA
| | - Jeffrey R Errington
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-4200, USA
| | - Vincent K Shen
- Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8320, USA
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1161
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Harmon TS, Holehouse AS, Pappu RV. To Mix, or To Demix, That Is the Question. Biophys J 2017; 112:565-567. [PMID: 28256216 DOI: 10.1016/j.bpj.2016.12.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 12/20/2016] [Accepted: 12/21/2016] [Indexed: 10/20/2022] Open
Affiliation(s)
- Tyler S Harmon
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Alex S Holehouse
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, Missouri.
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1162
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Garagounis C, Kostaki KI, Hawkins TJ, Cummins I, Fricker MD, Hussey PJ, Hetherington AM, Sweetlove LJ. Microcompartmentation of cytosolic aldolase by interaction with the actin cytoskeleton in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:885-898. [PMID: 28338736 DOI: 10.1093/jxb/erx015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Evidence is accumulating for molecular microcompartments formed when proteins interact in localized domains with the cytoskeleton, organelle surfaces, and intracellular membranes. To understand the potential functional significance of protein microcompartmentation in plants, we studied the interaction of the glycolytic enzyme fructose bisphosphate aldolase with actin in Arabidopsis thaliana. Homology modelling of a major cytosolic isozyme of aldolase, FBA8, suggested that the tetrameric holoenzyme has two actin binding sites and could therefore act as an actin-bundling protein, as was reported for animal aldolases. This was confirmed by in vitro measurements of an increase in viscosity of F-actin polymerized in the presence of recombinant FBA8. Simultaneously, interaction with F-actin caused non-competitive inhibition of aldolase activity. We did not detect co-localization of an FBA8-RFP fusion protein, expressed in an fba8-knockout background, with the actin cytoskeleton using confocal laser-scanning microscopy. However, we did find evidence for a low level of interaction using FRET-FLIM analysis of FBA8-RFP co-expressed with the actin-binding protein GFP-Lifeact. Furthermore, knockout of FBA8 caused minor alterations of guard cell actin cytoskeleton morphology and resulted in a reduced rate of stomatal closure in response to decreased humidity. We conclude that cytosolic aldolase can be microcompartmented in vivo by interaction with the actin cytoskeleton and may subtly modulate guard cell behaviour as a result.
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Affiliation(s)
- Constantine Garagounis
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Kalliopi-Ioanna Kostaki
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Tim J Hawkins
- School of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Ian Cummins
- School of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Mark D Fricker
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Patrick J Hussey
- School of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Alistair M Hetherington
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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1163
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Reiter F, Wienerroither S, Stark A. Combinatorial function of transcription factors and cofactors. Curr Opin Genet Dev 2017; 43:73-81. [PMID: 28110180 DOI: 10.1016/j.gde.2016.12.007] [Citation(s) in RCA: 190] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 12/14/2016] [Accepted: 12/21/2016] [Indexed: 12/31/2022]
Abstract
Differential gene expression gives rise to the many cell types of complex organisms. Enhancers regulate transcription by binding transcription factors (TFs), which in turn recruit cofactors to activate RNA Polymerase II at core promoters. Transcriptional regulation is typically mediated by distinct combinations of TFs, enabling a relatively small number of TFs to generate a large diversity of cell types. However, how TFs achieve combinatorial enhancer control and how enhancers, enhancer-bound TFs, and the cofactors they recruit regulate RNA Polymerase II activity is not entirely clear. Here, we review how TF synergy is mediated at the level of DNA binding and after binding, the role of cofactors and the post-translational modifications they catalyze, and discuss different models of enhancer-core-promoter communication.
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Affiliation(s)
- Franziska Reiter
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Sebastian Wienerroither
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Alexander Stark
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria.
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1164
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Abstract
Phase separation of proteins is recognized as an important aspect of cellular organization and disease mechanisms. Shin et al. introduce a novel optogenetic tool, which enables different phase-space regimes inside living cells to be assessed and the transition paths between them to be studied with unprecedented spatiotemporal control.
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Affiliation(s)
- Giulia Paci
- Structural and Computational Biology Unit and Cell Biology and Biophysics Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Edward A Lemke
- Structural and Computational Biology Unit and Cell Biology and Biophysics Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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1165
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Picart C, Pontvianne F. Plant nucleolar DNA: Green light shed on the role of Nucleolin in genome organization. Nucleus 2017; 8:11-16. [PMID: 27644794 PMCID: PMC5287095 DOI: 10.1080/19491034.2016.1236167] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/02/2016] [Accepted: 09/08/2016] [Indexed: 10/21/2022] Open
Abstract
The nucleolus forms as a consequence of ribosome biogenesis, but it is also implicated in other cell functions. The identification of nucleolus-associated chromatin domains (NADs) in animal and plant cells revealed the presence of DNA sequences other than rRNA genes in and around the nucleolus. NADs display repressive chromatin signatures and harbour repetitive DNA, but also tRNA genes and RNA polymerase II-transcribed genes. Furthermore, the identification of NADs revealed a specific function of the nucleolus and the protein Nucleolin 1 (NUC1) in telomere biology. Here, we discuss the significance of these data with regard to nucleolar structure and to the role of the nucleolus and NUC1 in global genome organization and stability.
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Affiliation(s)
- Claire Picart
- CNRS, Laboratoire Génome et Développement des Plantes, UMR5096, F-66860, Perpignan, France
- Université de Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR5096, F-66860, Perpignan, France
| | - Frédéric Pontvianne
- CNRS, Laboratoire Génome et Développement des Plantes, UMR5096, F-66860, Perpignan, France
- Université de Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR5096, F-66860, Perpignan, France
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1166
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Rodriguez-Corona U, Pereira-Santana A, Sobol M, Rodriguez-Zapata LC, Hozak P, Castano E. Novel Ribonuclease Activity Differs between Fibrillarins from Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2017; 8:1878. [PMID: 29163603 PMCID: PMC5674935 DOI: 10.3389/fpls.2017.01878] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 10/16/2017] [Indexed: 05/09/2023]
Abstract
Fibrillarin is one of the most important nucleolar proteins that have been shown as essential for life. Fibrillarin localizes primarily at the periphery between fibrillar center and dense fibrillar component as well as in Cajal bodies. In most plants there are at least two different genes for fibrillarin. In Arabidopsis thaliana both genes show high level of expression in transcriptionally active cells. Here, we focus on two important differences between A. thaliana fibrillarins. First and most relevant is the enzymatic activity by AtFib2. The AtFib2 shows a novel ribonuclease activity that is not seen with AtFib1. Second is a difference in the ability to interact with phosphoinositides and phosphatidic acid between both proteins. We also show that the novel ribonuclease activity as well as the phospholipid binding region of fibrillarin is confine to the GAR domain. The ribonuclease activity of fibrillarin reveals in this study represents a new role for this protein in rRNA processing.
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Affiliation(s)
- Ulises Rodriguez-Corona
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de Yucatán, Mérida, Mexico
| | - Alejandro Pereira-Santana
- Biosystematics Group, Department of Plant Sciences, Wageningen University and Research, Wageningen, Netherlands
| | - Margarita Sobol
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic, Prague, Czechia
| | | | - Pavel Hozak
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Enrique Castano
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de Yucatán, Mérida, Mexico
- *Correspondence: Enrique Castano,
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1167
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Aumiller WM, Keating CD. Experimental models for dynamic compartmentalization of biomolecules in liquid organelles: Reversible formation and partitioning in aqueous biphasic systems. Adv Colloid Interface Sci 2017; 239:75-87. [PMID: 27401136 DOI: 10.1016/j.cis.2016.06.011] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/15/2016] [Accepted: 06/18/2016] [Indexed: 12/29/2022]
Abstract
Living cells contain numerous subcellular compartments, many of which lack membranous boundaries and are thought to occur due to liquid-liquid phase coexistence. This review will introduce these biological membraneless organelles and discuss simple experimental models based on liquid-liquid phase separation in polymer solutions. When more than one phase is present, solutes such as proteins or nucleic acids can be compartmentalized by partitioning into one of the phases. This could confer benefits to the cell such as enhanced reaction rates or sequestration of toxic molecules. Liquid-like compartments inside living cells are often dynamic, for example, appearing and disappearing in response to stimuli and/or at different points in the cell cycle. We will discuss mechanisms by which phase transitions can be induced in the laboratory and inside living cells, with special emphasis on regulating phase formation by phosphorylation state. This work is motivated by a desire to understand the physical and chemical mechanisms that underlie biological processes and to enable new nonbiological applications.
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1168
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Cohen-Fix O, Askjaer P. Cell Biology of the Caenorhabditis elegans Nucleus. Genetics 2017; 205:25-59. [PMID: 28049702 PMCID: PMC5216270 DOI: 10.1534/genetics.116.197160] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 11/09/2016] [Indexed: 12/25/2022] Open
Abstract
Studies on the Caenorhabditis elegans nucleus have provided fascinating insight to the organization and activities of eukaryotic cells. Being the organelle that holds the genetic blueprint of the cell, the nucleus is critical for basically every aspect of cell biology. The stereotypical development of C. elegans from a one cell-stage embryo to a fertile hermaphrodite with 959 somatic nuclei has allowed the identification of mutants with specific alterations in gene expression programs, nuclear morphology, or nuclear positioning. Moreover, the early C. elegans embryo is an excellent model to dissect the mitotic processes of nuclear disassembly and reformation with high spatiotemporal resolution. We review here several features of the C. elegans nucleus, including its composition, structure, and dynamics. We also discuss the spatial organization of chromatin and regulation of gene expression and how this depends on tight control of nucleocytoplasmic transport. Finally, the extensive connections of the nucleus with the cytoskeleton and their implications during development are described. Most processes of the C. elegans nucleus are evolutionarily conserved, highlighting the relevance of this powerful and versatile model organism to human biology.
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Affiliation(s)
- Orna Cohen-Fix
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Peter Askjaer
- Andalusian Center for Developmental Biology, Consejo Superior de Investigaciones Científicas/Junta de Andalucia/Universidad Pablo de Olavide, 41013 Seville, Spain
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1169
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Shin Y, Berry J, Pannucci N, Haataja MP, Toettcher JE, Brangwynne CP. Spatiotemporal Control of Intracellular Phase Transitions Using Light-Activated optoDroplets. Cell 2016; 168:159-171.e14. [PMID: 28041848 DOI: 10.1016/j.cell.2016.11.054] [Citation(s) in RCA: 569] [Impact Index Per Article: 71.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 09/20/2016] [Accepted: 11/28/2016] [Indexed: 11/28/2022]
Abstract
Phase transitions driven by intrinsically disordered protein regions (IDRs) have emerged as a ubiquitous mechanism for assembling liquid-like RNA/protein (RNP) bodies and other membrane-less organelles. However, a lack of tools to control intracellular phase transitions limits our ability to understand their role in cell physiology and disease. Here, we introduce an optogenetic platform that uses light to activate IDR-mediated phase transitions in living cells. We use this "optoDroplet" system to study condensed phases driven by the IDRs of various RNP body proteins, including FUS, DDX4, and HNRNPA1. Above a concentration threshold, these constructs undergo light-activated phase separation, forming spatiotemporally definable liquid optoDroplets. FUS optoDroplet assembly is fully reversible even after multiple activation cycles. However, cells driven deep within the phase boundary form solid-like gels that undergo aging into irreversible aggregates. This system can thus elucidate not only physiological phase transitions but also their link to pathological aggregates.
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Affiliation(s)
- Yongdae Shin
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Joel Berry
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Nicole Pannucci
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Mikko P Haataja
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Jared E Toettcher
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA.
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1170
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Tiwary AK, Cecilia D. Kinetics of the association of dengue virus capsid protein with the granular component of nucleolus. Virology 2016; 502:48-55. [PMID: 27992765 DOI: 10.1016/j.virol.2016.12.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 11/25/2016] [Accepted: 12/13/2016] [Indexed: 11/24/2022]
Abstract
Dengue virus (DENV) replicates in the cytoplasm but translocation of the capsid protein (C) to the nucleoli of infected cells has been shown to facilitate virus multiplication for DENV-2. This study demonstrates that the nucleolar localization of C occurs with all four serotypes of DENV. The interaction of C with the nucleolus was found to be dynamic with a mobile fraction of 66% by FRAP. That the C shuttled between the nucleus and cytoplasm was suggested by FLIP and translation inhibition experiments. Colocalization with B23 indicated that DENV C targeted the granular component (GC) of the nucleolus. Presence of DENV C in the nucleolus affected the recovery kinetics of B23 in infected and transfected cells. Sub-nucleolar localization of DENV C of all serotypes to the GC, its mobility in and out of the nucleolus and its affect on the dynamics of B23 is being shown for the first time.
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Affiliation(s)
- Ashish Kumar Tiwary
- Dengue Group, National Institute of Virology, 20-A Ambedkar Road, Pune 411001, Maharashtra, India
| | - D Cecilia
- Dengue Group, National Institute of Virology, 20-A Ambedkar Road, Pune 411001, Maharashtra, India.
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1171
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Lee KH, Zhang P, Kim HJ, Mitrea DM, Sarkar M, Freibaum BD, Cika J, Coughlin M, Messing J, Molliex A, Maxwell BA, Kim NC, Temirov J, Moore J, Kolaitis RM, Shaw TI, Bai B, Peng J, Kriwacki RW, Taylor JP. C9orf72 Dipeptide Repeats Impair the Assembly, Dynamics, and Function of Membrane-Less Organelles. Cell 2016; 167:774-788.e17. [PMID: 27768896 PMCID: PMC5079111 DOI: 10.1016/j.cell.2016.10.002] [Citation(s) in RCA: 496] [Impact Index Per Article: 62.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/03/2016] [Accepted: 09/30/2016] [Indexed: 12/13/2022]
Abstract
Expansion of a hexanucleotide repeat GGGGCC (G4C2) in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Transcripts carrying (G4C2) expansions undergo unconventional, non-ATG-dependent translation, generating toxic dipeptide repeat (DPR) proteins thought to contribute to disease. Here, we identify the interactome of all DPRs and find that arginine-containing DPRs, polyGly-Arg (GR) and polyPro-Arg (PR), interact with RNA-binding proteins and proteins with low complexity sequence domains (LCDs) that often mediate the assembly of membrane-less organelles. Indeed, most GR/PR interactors are components of membrane-less organelles such as nucleoli, the nuclear pore complex and stress granules. Genetic analysis in Drosophila demonstrated the functional relevance of these interactions to DPR toxicity. Furthermore, we show that GR and PR altered phase separation of LCD-containing proteins, insinuating into their liquid assemblies and changing their material properties, resulting in perturbed dynamics and/or functions of multiple membrane-less organelles.
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Affiliation(s)
- Kyung-Ha Lee
- 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
| | - Hong Joo Kim
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mohona Sarkar
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Brian D Freibaum
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jaclyn Cika
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Maura Coughlin
- 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
| | - Amandine Molliex
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Brian A Maxwell
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Nam Chul Kim
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jamshid Temirov
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jennifer Moore
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Regina-Maria Kolaitis
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Department of Cell and Molecular Biology, St Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Timothy I Shaw
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Bing Bai
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Junmin Peng
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; St. Jude Proteomics Facility, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, 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, Department of Cell and Molecular Biology, St Jude Children's Research Hospital, Memphis, TN 38105, USA.
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1172
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Levine ZA, Shea JE. Simulations of disordered proteins and systems with conformational heterogeneity. Curr Opin Struct Biol 2016; 43:95-103. [PMID: 27988422 DOI: 10.1016/j.sbi.2016.11.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/07/2016] [Indexed: 12/29/2022]
Abstract
Intrinsically disordered proteins (IDPs) and protein regions can facilitate a wide variety of complex physiological processes such as binding, signaling, and formation of membraneless organelles. They can however also play pathological roles by aggregating into cytotoxic oligomers and fibrils. Characterizing the structure and function of disordered proteins is an onerous task, primarily because these proteins adopt transient structures, which are difficult to capture in experiments. Simulations have emerged as a powerful tool for interpreting and augmenting experimental measurements of IDPs. In this review we focus on computer simulations of disordered protein structures, functions, assemblies, and emerging questions that, taken together, give an overview of the field as it exists today.
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Affiliation(s)
- Zachary A Levine
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106, USA; Department of Physics, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Joan-Emma Shea
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106, USA; Department of Physics, University of California Santa Barbara, Santa Barbara, CA 93106, USA.
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1173
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Kennedy MB, Mastro TL. Liquid Phase Transition in the Postsynaptic Density? Trends Biochem Sci 2016; 42:2-4. [PMID: 27955862 DOI: 10.1016/j.tibs.2016.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 11/22/2016] [Indexed: 02/04/2023]
Affiliation(s)
- Mary B Kennedy
- Division of Biology and Biological Engineering, Mail Code 216-76, California Institute of Technology (Caltech), Pasadena, CA 91125, USA.
| | - Tara L Mastro
- Division of Biology and Biological Engineering, Mail Code 216-76, California Institute of Technology (Caltech), Pasadena, CA 91125, USA
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1174
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Taylor N, Elbaum-Garfinkle S, Vaidya N, Zhang H, Stone HA, Brangwynne CP. Biophysical characterization of organelle-based RNA/protein liquid phases using microfluidics. SOFT MATTER 2016; 12:9142-9150. [PMID: 27791212 PMCID: PMC6724727 DOI: 10.1039/c6sm01087c] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Living cells contain numerous membrane-less RNA/protein (RNP) bodies that assemble by intracellular liquid-liquid phase separation. The properties of these condensed phase droplets are increasingly recognized as important in their physiological function within living cells, and also through the link to protein aggregation pathologies. However, techniques such as droplet coalescence analysis or standard microrheology do not always enable robust property measurements of model RNA/protein droplets in vitro. Here, we introduce a microfluidic platform that drives protein droplets into a single large phase, which facilitates viscosity measurements using passive microrheology and/or active two-phase flow analysis. We use this technique to study various phase separating proteins from structures including P granules, nucleoli, and Whi3 droplets. In each case, droplets exhibit simple liquid behavior, with shear rate-independent viscosities, over observed timescales. Interestingly, we find that a reported order of magnitude difference between the timescale of Whi3 and LAF-1 droplet coalescence is driven by large differences in surface tension rather than viscosity, with implications for droplet assembly and function. The ability to simultaneously perform active and passive microrheological measurements enables studying the impact of ATP-dependent biological activity on RNP droplets, which is a key area for future research.
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Affiliation(s)
- Nicole Taylor
- Department of Chemical and Biological Engineering, Princeton University, USA.
| | | | - Nilesh Vaidya
- Department of Chemical and Biological Engineering, Princeton University, USA.
| | - Huaiying Zhang
- Department of Chemical and Biological Engineering, Princeton University, USA.
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, USA
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1175
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Blocher WC, Perry SL. Complex coacervate-based materials for biomedicine. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2016; 9. [DOI: 10.1002/wnan.1442] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/10/2016] [Accepted: 10/02/2016] [Indexed: 02/06/2023]
Affiliation(s)
- Whitney C. Blocher
- Department of Chemical Engineering; University of Massachusetts Amherst; Amherst MA USA
| | - Sarah L. Perry
- Department of Chemical Engineering; University of Massachusetts Amherst; Amherst MA USA
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1176
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Long non-coding RNAs: spatial amplifiers that control nuclear structure and gene expression. Nat Rev Mol Cell Biol 2016; 17:756-770. [DOI: 10.1038/nrm.2016.126] [Citation(s) in RCA: 420] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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1177
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Abstract
A recent study visualizes nascent RNAs in live Drosophila embryos to establish a connection between enhancer strength and the frequency of transcriptional bursts. Interestingly, one enhancer can simultaneously activate two core promoters, challenging models of enhancer-core-promoter communication via direct protein-protein contacts.
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Affiliation(s)
- Felix Muerdter
- Research Institute of Molecular Pathology, Vienna Biocenter, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Alexander Stark
- Research Institute of Molecular Pathology, Vienna Biocenter, Dr. Bohr-Gasse 7, 1030 Vienna, Austria.
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1178
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Trinkle-Mulcahy L, Sleeman JE. The Cajal body and the nucleolus: "In a relationship" or "It's complicated"? RNA Biol 2016; 14:739-751. [PMID: 27661468 DOI: 10.1080/15476286.2016.1236169] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
From their initial identification as 'nucleolar accessory bodies' more than a century ago, the relationship between Cajal bodies and nucleoli has been a subject of interest and controversy. In this review, we seek to place recent developments in the understanding of the physical and functional relationships between the 2 structures in the context of historical observations. Biophysical models of nuclear body formation, the molecular nature of CB/nucleolus interactions and the increasing list of joint roles for CBs and nucleoli, predominantly in assembling ribonucleoprotein (RNP) complexes, are discussed.
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Affiliation(s)
- Laura Trinkle-Mulcahy
- a Department of Cellular and Molecular Medicine , Ottawa Institute of Systems Biology, University of Ottawa , Ottawa , ON , Canada
| | - Judith E Sleeman
- b BSRC Complex, School of Biology, University of St Andrews , UK
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1179
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Wheeler JR, Matheny T, Jain S, Abrisch R, Parker R. Distinct stages in stress granule assembly and disassembly. eLife 2016; 5:e18413. [PMID: 27602576 DOI: 10.7554/elife.18413.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/15/2016] [Indexed: 05/23/2023] Open
Abstract
Stress granules are non-membrane bound RNA-protein (RNP) assemblies that form when translation initiation is limited and contain a biphasic structure with stable core structures surrounded by a less concentrated shell. The order of assembly and disassembly of these two structures remains unknown. Time course analysis of granule assembly suggests that core formation is an early event in granule assembly. Stress granule disassembly is also a stepwise process with shell dissipation followed by core clearance. Perturbations that alter liquid-liquid phase separations (LLPS) driven by intrinsically disordered protein regions (IDR) of RNA binding proteins in vitro have the opposite effect on stress granule assembly in vivo. Taken together, these observations argue that stress granules assemble through a multistep process initiated by stable assembly of untranslated mRNPs into core structures, which could provide sufficient high local concentrations to allow for a localized LLPS driven by IDRs on RNA binding proteins.
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Affiliation(s)
- Joshua R Wheeler
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Tyler Matheny
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Saumya Jain
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Robert Abrisch
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Roy Parker
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
- Howard Hughes Medical Institute, University of Colorado, Boulder, United States
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1180
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Wheeler JR, Matheny T, Jain S, Abrisch R, Parker R. Distinct stages in stress granule assembly and disassembly. eLife 2016; 5. [PMID: 27602576 PMCID: PMC5014549 DOI: 10.7554/elife.18413] [Citation(s) in RCA: 495] [Impact Index Per Article: 61.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/15/2016] [Indexed: 12/31/2022] Open
Abstract
Stress granules are non-membrane bound RNA-protein (RNP) assemblies that form when translation initiation is limited and contain a biphasic structure with stable core structures surrounded by a less concentrated shell. The order of assembly and disassembly of these two structures remains unknown. Time course analysis of granule assembly suggests that core formation is an early event in granule assembly. Stress granule disassembly is also a stepwise process with shell dissipation followed by core clearance. Perturbations that alter liquid-liquid phase separations (LLPS) driven by intrinsically disordered protein regions (IDR) of RNA binding proteins in vitro have the opposite effect on stress granule assembly in vivo. Taken together, these observations argue that stress granules assemble through a multistep process initiated by stable assembly of untranslated mRNPs into core structures, which could provide sufficient high local concentrations to allow for a localized LLPS driven by IDRs on RNA binding proteins. DOI:http://dx.doi.org/10.7554/eLife.18413.001
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Affiliation(s)
- Joshua R Wheeler
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Tyler Matheny
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Saumya Jain
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Robert Abrisch
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Roy Parker
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, United States.,Howard Hughes Medical Institute, University of Colorado, Boulder, United States
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1181
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In Vivo Formation of Vacuolated Multi-phase Compartments Lacking Membranes. Cell Rep 2016; 16:1228-1236. [PMID: 27452472 DOI: 10.1016/j.celrep.2016.06.088] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 06/02/2016] [Accepted: 06/24/2016] [Indexed: 12/12/2022] Open
Abstract
Eukaryotic cells contain membrane-less organelles, including nucleoli and stress granules, that behave like liquid droplets. Such endogenous condensates often have internal substructure, but how this is established in the absence of membrane encapsulation remains unclear. We find that the N- and C-terminal domains of TDP43, a heterogeneous nuclear ribonucleoprotein implicated in neurodegenerative diseases, are capable of driving the formation of sub-structured liquid droplets in vivo. These droplets contain dynamic internal "bubbles" of nucleoplasm, reminiscent of membrane-based multi-vesicular endosomes. A conserved sequence embedded within the intrinsically disordered region (IDR) of TDP43 promotes the formation of these multi-phase assemblies. Disease-causing point mutations in the IDR can change the propensity to form bubbles, protein dynamics within the phase, or phase-environment exchange rates. Our results show that a single IDR-containing protein can nucleate the assembly of compartmentalized liquid droplets approximating the morphological complexity of membrane-bound organelles.
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1182
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Banani SF, Rice AM, Peeples WB, Lin Y, Jain S, Parker R, Rosen MK. Compositional Control of Phase-Separated Cellular Bodies. Cell 2016; 166:651-663. [PMID: 27374333 DOI: 10.1016/j.cell.2016.06.010] [Citation(s) in RCA: 771] [Impact Index Per Article: 96.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 03/13/2016] [Accepted: 06/01/2016] [Indexed: 12/12/2022]
Abstract
Cellular bodies such as P bodies and PML nuclear bodies (PML NBs) appear to be phase-separated liquids organized by multivalent interactions among proteins and RNA molecules. Although many components of various cellular bodies are known, general principles that define body composition are lacking. We modeled cellular bodies using several engineered multivalent proteins and RNA. In vitro and in cells, these scaffold molecules form phase-separated liquids that concentrate low valency client proteins. Clients partition differently depending on the ratio of scaffolds, with a sharp switch across the phase diagram diagonal. Composition can switch rapidly through changes in scaffold concentration or valency. Natural PML NBs and P bodies show analogous partitioning behavior, suggesting how their compositions could be controlled by levels of PML SUMOylation or cellular mRNA concentration, respectively. The data suggest a conceptual framework for considering the composition and control thereof of cellular bodies assembled through heterotypic multivalent interactions.
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Affiliation(s)
- Salman F Banani
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Allyson M Rice
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - William B Peeples
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yuan Lin
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Saumya Jain
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80309, USA
| | - Roy Parker
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80309, USA
| | - Michael K Rosen
- Department of Biophysics and Howard Hughes Medical Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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1183
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1184
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Bergeron-Sandoval LP, Safaee N, Michnick S. Mechanisms and Consequences of Macromolecular Phase Separation. Cell 2016; 165:1067-1079. [DOI: 10.1016/j.cell.2016.05.026] [Citation(s) in RCA: 186] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 03/23/2016] [Accepted: 04/26/2016] [Indexed: 12/29/2022]
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