201
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Organization and regulation of gene transcription. Nature 2019; 573:45-54. [PMID: 31462772 DOI: 10.1038/s41586-019-1517-4] [Citation(s) in RCA: 355] [Impact Index Per Article: 71.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 07/30/2019] [Indexed: 12/18/2022]
Abstract
The regulated transcription of genes determines cell identity and function. Recent structural studies have elucidated mechanisms that govern the regulation of transcription by RNA polymerases during the initiation and elongation phases. Microscopy studies have revealed that transcription involves the condensation of factors in the cell nucleus. A model is emerging for the transcription of protein-coding genes in which distinct transient condensates form at gene promoters and in gene bodies to concentrate the factors required for transcription initiation and elongation, respectively. The transcribing enzyme RNA polymerase II may shuttle between these condensates in a phosphorylation-dependent manner. Molecular principles are being defined that rationalize transcriptional organization and regulation, and that will guide future investigations.
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202
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Kim TH, Tsang B, Vernon RM, Sonenberg N, Kay LE, Forman-Kay JD. Phospho-dependent phase separation of FMRP and CAPRIN1 recapitulates regulation of translation and deadenylation. Science 2019; 365:825-829. [DOI: 10.1126/science.aax4240] [Citation(s) in RCA: 152] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 07/29/2019] [Indexed: 12/16/2022]
Abstract
Membraneless organelles involved in RNA processing are biomolecular condensates assembled by phase separation. Despite the important role of intrinsically disordered protein regions (IDRs), the specific interactions underlying IDR phase separation and its functional consequences remain elusive. To address these questions, we used minimal condensates formed from the C-terminal disordered regions of two interacting translational regulators, FMRP and CAPRIN1. Nuclear magnetic resonance spectroscopy of FMRP-CAPRIN1 condensates revealed interactions involving arginine-rich and aromatic-rich regions. We found that different FMRP serine/threonine and CAPRIN1 tyrosine phosphorylation patterns control phase separation propensity with RNA, including subcompartmentalization, and tune deadenylation and translation rates in vitro. The resulting evidence for residue-specific interactions underlying co–phase separation, phosphorylation-modulated condensate architecture, and enzymatic activity within condensates has implications for how the integration of signaling pathways controls RNA processing and translation.
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203
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Onuchic PL, Milin AN, Alshareedah I, Deniz AA, Banerjee PR. Divalent cations can control a switch-like behavior in heterotypic and homotypic RNA coacervates. Sci Rep 2019; 9:12161. [PMID: 31434954 PMCID: PMC6704260 DOI: 10.1038/s41598-019-48457-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 08/06/2019] [Indexed: 01/30/2023] Open
Abstract
Liquid-liquid phase separation (LLPS) of RNA-protein complexes plays a major role in the cellular function of membraneless organelles (MLOs). MLOs are sensitive to changes in cellular conditions, such as fluctuations in cytoplasmic ion concentrations. To investigate the effect of these changes on MLOs, we studied the influence of divalent cations on the physical and chemical properties of RNA coacervates. Using a model system comprised of an arginine-rich peptide and RNA, we predicted and observed that variations in signaling cations exert interaction-dependent effects on RNA LLPS. Changing the ionic environment has opposing effects on the propensity for heterotypic peptide-RNA and homotypic RNA LLPS, which results in a switch between coacervate types. Furthermore, divalent ion variations continuously tune the microenvironments and fluid properties of heterotypic and homotypic droplets. Our results may provide a general mechanism for modulating the biochemical environment of RNA coacervates in a cellular context.
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Affiliation(s)
- Paulo L Onuchic
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, 92037, USA
| | - Anthony N Milin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, 92037, USA
| | - Ibraheem Alshareedah
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Ashok A Deniz
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, 92037, USA.
| | - Priya R Banerjee
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
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204
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Abstract
New findings suggest that transcription enhancers work by recruitment of a large dynamic network of coactivators and other factors responsible for gene activation. Formation of these condensates is driven by DNA-bound transcription factors, their intrinsically disordered activation domains, and dynamic low-specificity interactions within the complex.
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Affiliation(s)
- Steven Hahn
- Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
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205
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Lång A, Lång E, Bøe SO. PML Bodies in Mitosis. Cells 2019; 8:cells8080893. [PMID: 31416160 PMCID: PMC6721746 DOI: 10.3390/cells8080893] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 08/08/2019] [Accepted: 08/10/2019] [Indexed: 12/14/2022] Open
Abstract
Promyelocytic leukemia (PML) bodies are dynamic intracellular structures that recruit and release a variety of different proteins in response to stress, virus infection, DNA damage and cell cycle progression. While PML bodies primarily are regarded as nuclear compartments, they are forced to travel to the cytoplasm each time a cell divides, due to breakdown of the nuclear membrane at entry into mitosis and subsequent nuclear exclusion of nuclear material at exit from mitosis. Here we review the biochemical and biophysical transitions that occur in PML bodies during mitosis and discuss this in light of post-mitotic nuclear import, cell fate decision and acute promyelocytic leukemia therapy.
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Affiliation(s)
- Anna Lång
- Oslo University Hospital, Department of Molecular Microbiology, Forskningsveien 1, 0373 Oslo, Norway
| | - Emma Lång
- Oslo University Hospital, Department of Molecular Microbiology, Forskningsveien 1, 0373 Oslo, Norway
| | - Stig Ove Bøe
- Oslo University Hospital, Department of Molecular Microbiology, Forskningsveien 1, 0373 Oslo, Norway.
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206
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Formicola N, Vijayakumar J, Besse F. Neuronal ribonucleoprotein granules: Dynamic sensors of localized signals. Traffic 2019; 20:639-649. [PMID: 31206920 DOI: 10.1111/tra.12672] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 06/03/2019] [Accepted: 06/11/2019] [Indexed: 12/14/2022]
Abstract
Membrane-less organelles, because of their capacity to dynamically, selectively and reversibly concentrate molecules, are very well adapted for local information processing and rapid response to environmental fluctuations. These features are particularly important in the context of neuronal cells, where synapse-specific activation, or localized extracellular cues, induce signaling events restricted to specialized axonal or dendritic subcompartments. Neuronal ribonucleoprotein (RNP) particles, or granules, are nonmembrane bound macromolecular condensates that concentrate specific sets of mRNAs and regulatory proteins, promoting their long-distance transport to axons or dendrites. Neuronal RNP granules also have a dual function in regulating the translation of associated mRNAs: while preventing mRNA translation at rest, they fuel local protein synthesis upon activation. As revealed by recent work, rapid and reversible switches between these two functional modes are triggered by modifications of the networks of interactions underlying RNP granule assembly. Such flexible properties also come with a cost, as neuronal RNP granules are prone to transition into pathological aggregates in response to mutations, aging, or cellular stresses, further emphasizing the need to better understand the mechanistic principles governing their dynamic assembly and regulation in living systems.
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207
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208
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Ditlev JA, Vega AR, Köster DV, Su X, Tani T, Lakoduk AM, Vale RD, Mayor S, Jaqaman K, Rosen MK. A composition-dependent molecular clutch between T cell signaling condensates and actin. eLife 2019; 8:e42695. [PMID: 31268421 PMCID: PMC6624021 DOI: 10.7554/elife.42695] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 06/14/2019] [Indexed: 01/04/2023] Open
Abstract
During T cell activation, biomolecular condensates form at the immunological synapse (IS) through multivalency-driven phase separation of LAT, Grb2, Sos1, SLP-76, Nck, and WASP. These condensates move radially at the IS, traversing successive radially-oriented and concentric actin networks. To understand this movement, we biochemically reconstituted LAT condensates with actomyosin filaments. We found that basic regions of Nck and N-WASP/WASP promote association and co-movement of LAT condensates with actin, indicating conversion of weak individual affinities to high collective affinity upon phase separation. Condensates lacking these components were propelled differently, without strong actin adhesion. In cells, LAT condensates lost Nck as radial actin transitioned to the concentric network, and engineered condensates constitutively binding actin moved aberrantly. Our data show that Nck and WASP form a clutch between LAT condensates and actin in vitro and suggest that compositional changes may enable condensate movement by distinct actin networks in different regions of the IS.
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Affiliation(s)
- Jonathon A Ditlev
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of BiophysicsHoward Hughes Medical Institute, University of Texas Southwestern Medical CenterDallasUnited States
| | - Anthony R Vega
- Department of BiophysicsUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Darius Vasco Köster
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- National Centre for Biological Sciences, Tata Institute for Fundamental ResearchBangaloreIndia
| | - Xiaolei Su
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of Cellular and Molecular PharmacologyHoward Hughes Medical Institute, University of California, San FranciscoSan FranciscoUnited States
| | - Tomomi Tani
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological LaboratoryWoods HoleUnited States
| | - Ashley M Lakoduk
- Department of Cell BiologyUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Ronald D Vale
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of Cellular and Molecular PharmacologyHoward Hughes Medical Institute, University of California, San FranciscoSan FranciscoUnited States
| | - Satyajit Mayor
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- National Centre for Biological Sciences, Tata Institute for Fundamental ResearchBangaloreIndia
| | - Khuloud Jaqaman
- Department of BiophysicsUniversity of Texas Southwestern Medical CenterDallasUnited States
- Lyda Hill Department of BioinformaticsUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Michael K Rosen
- Howard Hughes Medical Institute, Summer Institute, Marine Biological LaboratoryWoods HoleUnited States
- Department of BiophysicsHoward Hughes Medical Institute, University of Texas Southwestern Medical CenterDallasUnited States
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209
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ALS and FTD: Where RNA metabolism meets protein quality control. Semin Cell Dev Biol 2019; 99:183-192. [PMID: 31254610 DOI: 10.1016/j.semcdb.2019.06.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 06/14/2019] [Accepted: 06/14/2019] [Indexed: 12/12/2022]
Abstract
Recent genetic and biochemical evidence has improved our understanding of the pathomechanisms that lead to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two devastating neurodegenerative diseases with overlapping symptoms and causes. Impaired RNA metabolism, enhanced aggregation of protein-RNA complexes, aberrant formation of ribonucleoprotein (RNP) granules and dysfunctional protein clearance via autophagy are emerging as crucial events in ALS/FTD pathogenesis. Importantly, these processes interact at the molecular level, converging on a common pathogenic cascade. In this review, we summarize key principles underlying ALS and FTD, and we discuss how mutations in genes involved in RNA metabolism, protein quality control and protein degradation meet mechanistically to impair the functionality and dynamics of RNP granules, and how this leads to cellular toxicity and death. Finally, we describe recent advances in understanding signaling pathways that become dysfunctional in ALS/FTD, partly due to altered RNP granule dynamics, but also with stress granule-independent mechanisms and, thus could be promising targets for future therapeutic intervention.
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210
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Vindry C, Weil D, Standart N. Pat1 RNA-binding proteins: Multitasking shuttling proteins. WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 10:e1557. [PMID: 31231973 DOI: 10.1002/wrna.1557] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 05/02/2019] [Accepted: 05/07/2019] [Indexed: 12/11/2022]
Abstract
Post-transcriptional regulation of gene expression is largely achieved at the level of splicing in the nucleus, and translation and mRNA decay in the cytosol. While the regulation may be global, through the direct inhibition of central factors, such as the spliceosome, translation initiation factors and mRNA decay enzymes, in many instances transcripts bearing specific sequences or particular features are regulated by RNA-binding factors which mobilize or impede recruitment of these machineries. This review focuses on the Pat1 family of RNA-binding proteins, conserved from yeast to man, that enhance the removal of the 5' cap by the decapping enzyme Dcp1/2, leading to mRNA decay and also have roles in translational repression. Like Dcp1/2, other decapping coactivators, including DDX6 and Edc3, and translational repressor proteins, Pat1 proteins are enriched in cytoplasmic P-bodies, which have a principal role in mRNA storage. They also concentrate in nuclear Cajal-bodies and splicing speckles and in man, impact splice site choice in some pre-mRNAs. Pivotal to these functions is the association of Pat1 proteins with distinct heptameric Lsm complexes: the cytosolic Pat1/Lsm1-7 complex mediates mRNA decay and the nuclear Pat1/Lsm2-8 complex alternative splicing. This dual role of human Pat1b illustrates the power of paralogous complexes to impact distinct processes in separate compartments. The review highlights our recent findings that Pat1b mediates the decay of AU-rich mRNAs, which are particularly enriched in P-bodies, unlike the decapping activator DDX6, which acts on GC-rich mRNAs, that tend to be excluded from P-bodies, and discuss the implications for mRNA decay pathways. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNRNA Processing > Splicing Regulation/Alternative Splicing Translation > Translation Regulation.
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Affiliation(s)
- Caroline Vindry
- Centre International de Recherche en Infectiologie, CIRI, Lyon, France
| | - Dominique Weil
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire de Biologie du Développement, Paris, France
| | - Nancy Standart
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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211
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Min J, Wright WE, Shay JW. Clustered telomeres in phase-separated nuclear condensates engage mitotic DNA synthesis through BLM and RAD52. Genes Dev 2019; 33:814-827. [PMID: 31171703 PMCID: PMC6601508 DOI: 10.1101/gad.324905.119] [Citation(s) in RCA: 119] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/24/2019] [Indexed: 11/25/2022]
Abstract
Alternative lengthening of telomeres (ALT) is a telomerase-independent telomere maintenance mechanism that occurs in a subset of cancers. One of the hallmarks of ALT cancer is the excessively clustered telomeres in promyelocytic leukemia (PML) bodies, represented as large bright telomere foci. Here, we present a model system that generates telomere clustering in nuclear polySUMO (small ubiquitin-like modification)/polySIM (SUMO-interacting motif) condensates, analogous to PML bodies, and thus artificially engineered ALT-associated PML body (APB)-like condensates in vivo. We observed that the ALT-like phenotypes (i.e., a small fraction of heterogeneous telomere lengths and formation of C circles) are rapidly induced by introducing the APB-like condensates together with BLM through its helicase domain, accompanied by ssDNA generation and RPA accumulation at telomeres. Moreover, these events lead to mitotic DNA synthesis (MiDAS) at telomeres mediated by RAD52 through its highly conserved N-terminal domain. We propose that the clustering of large amounts of telomeres in human cancers promotes ALT that is mediated by MiDAS, analogous to Saccharomyces cerevisiae type II ALT survivors.
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Affiliation(s)
- Jaewon Min
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas, 75390, USA
| | - Woodring E Wright
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas, 75390, USA
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas, 75390, USA
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212
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Dignon G, Zheng W, Kim YC, Mittal J. Temperature-Controlled Liquid-Liquid Phase Separation of Disordered Proteins. ACS CENTRAL SCIENCE 2019; 5:821-830. [PMID: 31139718 PMCID: PMC6535772 DOI: 10.1021/acscentsci.9b00102] [Citation(s) in RCA: 160] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Indexed: 05/18/2023]
Abstract
The liquid-liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs) is a commonly observed phenomenon within the cell, and such condensates are also highly attractive for applications in biomaterials and drug delivery. A better understanding of the sequence-dependent thermoresponsive behavior is of immense interest as it will aid in the design of protein sequences with desirable properties and in the understanding of cellular response to heat stress. In this work, we use a transferable coarse-grained model to directly probe the sequence-dependent thermoresponsive phase behavior of IDPs. To achieve this goal, we develop a unique knowledge-based amino acid potential that accounts for the temperature-dependent effects on solvent-mediated interactions for different types of amino acids. Remarkably, we are able to distinguish between more than 35 IDPs with upper or lower critical solution temperatures at experimental conditions, thus providing direct evidence that incorporating the temperature-dependent solvent-mediated interactions to IDP assemblies can capture the difference in the shape of the resulting phase diagrams. Given the success of the model in predicting experimental behavior, we use it as a high-throughput screening framework to scan through millions of disordered sequences to characterize the composition dependence of protein phase separation.
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Affiliation(s)
- Gregory
L. Dignon
- Department
of Chemical and Biomolecular Engineering, Lehigh University, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Wenwei Zheng
- College
of Integrative Sciences and Arts, Arizona
State University, Mesa, Arizona 85212, United
States
| | - Young C. Kim
- Center
for Materials Physics and Technology, Naval
Research Laboratory, Washington, D.C. 20375, United States
| | - Jeetain Mittal
- Department
of Chemical and Biomolecular Engineering, Lehigh University, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
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213
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Raff JW. Phase Separation and the Centrosome: A Fait Accompli? Trends Cell Biol 2019; 29:612-622. [PMID: 31076235 DOI: 10.1016/j.tcb.2019.04.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/08/2019] [Accepted: 04/08/2019] [Indexed: 12/28/2022]
Abstract
There is currently intense interest in the idea that many membraneless organelles might assemble through phase separation of their constituent molecules into biomolecular 'condensates' that have liquid-like properties. This idea is intuitively appealing, especially for complex organelles such as centrosomes, where a liquid-like structure would allow the many constituent molecules to diffuse and interact with one another efficiently. I discuss here recent studies that either support the concept of a liquid-like centrosome or suggest that centrosomes are assembled upon a more solid, stable scaffold. I suggest that it may be difficult to distinguish between these possibilities. I argue that the concept of biomolecular condensates is an important advance in cell biology, with potentially wide-ranging implications, but it seems premature to conclude that centrosomes, and perhaps other membraneless organelles, are necessarily best described as liquid-like phase-separated condensates.
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Affiliation(s)
- Jordan W Raff
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
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214
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Guzikowski AR, Chen YS, Zid BM. Stress-induced mRNP granules: Form and function of processing bodies and stress granules. WILEY INTERDISCIPLINARY REVIEWS. RNA 2019; 10:e1524. [PMID: 30793528 PMCID: PMC6500494 DOI: 10.1002/wrna.1524] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 12/18/2018] [Accepted: 12/28/2018] [Indexed: 12/12/2022]
Abstract
In response to stress, cells must quickly reprogram gene expression to adapt and survive. This is achieved in part by altering levels of mRNAs and their translation into proteins. Recently, the formation of two stress-induced messenger ribonucleoprotein (mRNP) assemblies named stress granules and processing bodies has been postulated to directly impact gene expression during stress. These assemblies sequester and concentrate specific proteins and RNAs away from the larger cytoplasm during stress, thereby providing a layer of posttranscriptional gene regulation with the potential to directly impact mRNA levels, protein translation, and cell survival. The function of these granules has generally been ascribed either by the protein components concentrated into them or, more broadly, by global changes that occur during stress. Recent proteome- and transcriptome-wide studies have provided a more complete view of stress-induced mRNP granule composition in varied cell types and stress conditions. However, direct measurements of the phenotypic and functional consequences of stress granule and processing body formation are lacking. This leaves our understanding of their roles during stress incomplete. Continued study into the function of these granules will be an important part in elucidating how cells respond to and survive stressful environmental changes. This article is categorized under: Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Export and Localization > RNA Localization.
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Affiliation(s)
- Anna R. Guzikowski
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States of America
| | - Yang S. Chen
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States of America
| | - Brian M. Zid
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, United States of America
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215
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Ralston SH, Taylor JP. Rare Inherited forms of Paget's Disease and Related Syndromes. Calcif Tissue Int 2019; 104:501-516. [PMID: 30756140 PMCID: PMC6779132 DOI: 10.1007/s00223-019-00520-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 12/21/2018] [Indexed: 12/14/2022]
Abstract
Several rare inherited disorders have been described that show phenotypic overlap with Paget's disease of bone (PDB) and in which PDB is a component of a multisystem disorder affecting muscle and the central nervous system. These conditions are the subject of this review article. Insertion mutations within exon 1 of the TNFRSF11A gene, encoding the receptor activator of nuclear factor kappa B (RANK), cause severe PDB-like disorders including familial expansile osteolysis, early-onset familial PDB and expansile skeletal hyperphosphatasia. The mutations interfere with normal processing of RANK and cause osteoclast activation through activation of nuclear factor kappa B (NFκB) independent of RANK ligand stimulation. Recessive, loss-of-function mutations in the TNFRSF11B gene, which encodes osteoprotegerin, cause juvenile PDB and here the bone disease is due to unopposed activation of RANK by RANKL. Multisystem proteinopathy is a disorder characterised by myopathy and neurodegeneration in which PDB is often an integral component. It may be caused by mutations in several genes including VCP, HNRNPA1, HNRNPA2B1, SQSTM1, MATR3, and TIA1, some of which are involved in classical PDB. The mechanisms of osteoclast activation in these conditions are less clear but may involve NFκB activation through sequestration of IκB. The evidence base for management of these disorders is somewhat limited due to the fact they are extremely rare. Bisphosphonates have been successfully used to gain control of elevated bone remodelling but as yet, no effective treatment exists for the treatment of the muscle and neurological manifestations of MSP syndromes.
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Affiliation(s)
- Stuart H Ralston
- Centre for Genomic and Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK.
| | - J Paul Taylor
- Howard Hughes Medical Institute and Department of Cell and Molecular Biology, St Jude's Children's Research Hospital, Memphis, TN, USA
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216
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Nakashima KK, Vibhute MA, Spruijt E. Biomolecular Chemistry in Liquid Phase Separated Compartments. Front Mol Biosci 2019; 6:21. [PMID: 31001538 PMCID: PMC6456709 DOI: 10.3389/fmolb.2019.00021] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 03/11/2019] [Indexed: 12/11/2022] Open
Abstract
Biochemical processes inside the cell take place in a complex environment that is highly crowded, heterogeneous, and replete with interfaces. The recently recognized importance of biomolecular condensates in cellular organization has added new elements of complexity to our understanding of chemistry in the cell. Many of these condensates are formed by liquid-liquid phase separation (LLPS) and behave like liquid droplets. Such droplet organelles can be reproduced and studied in vitro by using coacervates and have some remarkable features, including regulated assembly, differential partitioning of macromolecules, permeability to small molecules, and a uniquely crowded environment. Here, we review the main principles of biochemical organization in model membraneless compartments. We focus on some promising in vitro coacervate model systems that aptly mimic part of the compartmentalized cellular environment. We address the physicochemical characteristics of these liquid phase separated compartments, and their impact on biomolecular chemistry and assembly. These model systems enable a systematic investigation of the role of spatiotemporal organization of biomolecules in controlling biochemical processes in the cell, and they provide crucial insights for the development of functional artificial organelles and cells.
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Affiliation(s)
| | | | - Evan Spruijt
- Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
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217
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Shastrula PK, Sierra I, Deng Z, Keeney F, Hayden JE, Lieberman PM, Janicki SM. PML is recruited to heterochromatin during S phase and represses DAXX-mediated histone H3.3 chromatin assembly. J Cell Sci 2019; 132:jcs.220970. [PMID: 30796101 DOI: 10.1242/jcs.220970] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 02/09/2019] [Indexed: 12/18/2022] Open
Abstract
The incorporation of the histone H3 variant, H3.3, into chromatin by the H3.3-specific chaperone DAXX and the ATP-dependent chromatin remodeling factor ATRX is a critical mechanism for silencing repetitive DNA. DAXX and ATRX are also components of promyelocytic nuclear bodies (PML-NBs), which have been identified as sites of H3.3 chromatin assembly. Here, we use a transgene array that can be visualized in single living cells to investigate the mechanisms that recruit PML-NB proteins (i.e. PML, DAXX, ATRX, and SUMO-1, SUMO-2 and SUMO-3) to heterochromatin and their functions in H3.3 chromatin assembly. We show that DAXX and PML are recruited to the array through distinct SUMOylation-dependent mechanisms. Additionally, PML is recruited during S phase and its depletion increases H3.3 deposition. Since this effect is abrogated when PML and DAXX are co-depleted, it is likely that PML represses DAXX-mediated H3.3 chromatin assembly. Taken together, these results suggest that, at heterochromatin, PML-NBs coordinate H3.3 chromatin assembly with DNA replication, which has important implications for understanding how transcriptional silencing is established and maintained.
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Affiliation(s)
- Prashanth Krishna Shastrula
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.,University of the Sciences in Philadelphia, Department of Biological Sciences, 600 South 43rd Street, Philadelphia, PA 19104, USA
| | - Isabel Sierra
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Zhong Deng
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Frederick Keeney
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - James E Hayden
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Paul M Lieberman
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Susan M Janicki
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
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218
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Abstract
The discovery of a biomolecular condensate involved in DNA replication has wide-ranging implications.
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Affiliation(s)
- Nina Y Yao
- Laboratory of DNA ReplicationThe Rockefeller UniversityNew YorkUnited States
| | - Michael E O'Donnell
- The Howard Hughes Medical Institute and the Laboratory of DNA ReplicationThe Rockefeller UniversityNew YorkUnited States
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219
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Affiliation(s)
- Julie D Forman-Kay
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - 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 38163, USA.
| | - Geraldine Seydoux
- Department of Molecular Biology and Genetics, HHMI, School of Medicine, Johns Hopkins University, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
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