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Li Y, Jin X, Yu C, Zuo M, Hong L, Wang M, Zhao C, Wu A, Wang J, Ju Z, Wang H. Phase separation of MRG15 delays cellular senescence. Commun Biol 2025; 8:688. [PMID: 40312521 PMCID: PMC12046007 DOI: 10.1038/s42003-025-08071-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2024] [Accepted: 04/10/2025] [Indexed: 05/03/2025] Open
Abstract
Phase separation, a biophysical process that segregates subcellular environments into condensates, has been recognized for its role in transcriptional regulation. However, the extent of its influence on cellular senescence processes remains to be fully elucidated. We established that MRG15 depletion leads to cellular senescence in human mesenchymal stem cells (hMSCs). MRG15 can form phase-separated liquid condensates via its intrinsically disordered region (IDR). IDR deletion and replacement assays revealed that MRG15 condensation is crucial to hMSC senescence. According to the epigenomic and transcriptomic analysis, MRG15 depletion impacts pathways integral to the cell cycle and the senescence process, as evidenced by the diminished binding and the modified expression of key genes, including p53, CDKN1A, LMNB1, CCNB1, NPM1, MYC, and HMGB2. Our findings establish a link between phase separation and senescence regulation and present a promising new therapeutic target for the alleviation of age-related diseases and the potential extension of lifespan.
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Affiliation(s)
- Yuwen Li
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
| | - Xinrong Jin
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China
| | - Chunyu Yu
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
| | - Min Zuo
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
| | - Liquan Hong
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
- Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou Institute of Cardiovascular Diseases, Hangzhou, China
| | - Mingwei Wang
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
- Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou Institute of Cardiovascular Diseases, Hangzhou, China
| | - Chenyan Zhao
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
| | - Aiwei Wu
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
| | - Jianjun Wang
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China
| | - Zhenyu Ju
- Key Laboratory of Regenerative Medicine of Ministry of Education, Institute of Aging and Regenerative Medicine, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong, China.
| | - Hu Wang
- Zhejiang Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences, The Third People's Hospital of Deqing, Department of Cardiology, Affiliated Hospital of Hangzhou Normal University, Hangzhou Normal University, Hangzhou, China.
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
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2
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McLaurin DM, Tucker SK, Siddique SJ, Challagundla L, Gibert Y, Hebert MD. A Novel Role for Coilin in Vertebrate Innate Immunity. FASEB J 2025; 39:e70580. [PMID: 40277349 PMCID: PMC12023821 DOI: 10.1096/fj.202403276r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2024] [Revised: 04/04/2025] [Accepted: 04/18/2025] [Indexed: 04/26/2025]
Abstract
Coilin is a protein localized in the nucleus, where it plays a role in the assembly of the Cajal Body and is involved in ribonucleoprotein biogenesis. Our recent research has uncovered new roles for coilin, including its involvement in producing microRNAs and in modifying other proteins through phosphorylation and SUMOylation. We also proposed that coilin could respond to stress signals. In plants, coilin has been shown to help regulate immune genes and activate defense mechanisms, especially in response to stress. In this study, we used two vertebrate models to study coilin function: a human primary foreskin fibroblast cell line deficient in coilin through RNA interference and a newly created zebrafish line with a mutation in the coilin gene generated by CRISPR-Cas9. Transcriptomic analysis in these two models of coilin deficiency revealed dysregulation of immunity-related genes in both species. To phenotypically validate the transcriptomic results, we challenged zebrafish coilin mutants with lipopolysaccharide (LPS), which triggers an innate immune response, and identified an attenuated response to LPS in vivo in the zebrafish coilin mutants. Our results support a vital novel function for coilin in vertebrates in regulating the expression of immunity-related genes. Moreover, these findings could lead to more research on how coilin regulates innate immunity in animals and humans.
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Affiliation(s)
- Douglas M. McLaurin
- Department of Cell and Molecular BiologyThe University of Mississippi Medical CenterJacksonMississippiUSA
| | - Sara K. Tucker
- Department of Cell and Molecular BiologyThe University of Mississippi Medical CenterJacksonMississippiUSA
| | - Shanzida J. Siddique
- Department of Cell and Molecular BiologyThe University of Mississippi Medical CenterJacksonMississippiUSA
| | - Lavanya Challagundla
- Department of Cell and Molecular BiologyThe University of Mississippi Medical CenterJacksonMississippiUSA
| | - Yann Gibert
- Department of Cell and Molecular BiologyThe University of Mississippi Medical CenterJacksonMississippiUSA
| | - Michael D. Hebert
- Department of Cell and Molecular BiologyThe University of Mississippi Medical CenterJacksonMississippiUSA
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3
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Fakim H, Vande Velde C. The implications of physiological biomolecular condensates in amyotrophic lateral sclerosis. Semin Cell Dev Biol 2024; 156:176-189. [PMID: 37268555 DOI: 10.1016/j.semcdb.2023.05.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/13/2023] [Accepted: 05/16/2023] [Indexed: 06/04/2023]
Abstract
In recent years, there has been an emphasis on the role of phase-separated biomolecular condensates, especially stress granules, in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). This is largely due to several ALS-associated mutations occurring in genes involved in stress granule assembly and observations that pathological inclusions detected in ALS patient neurons contain stress granule proteins, including the ALS-linked proteins TDP-43 and FUS. However, protein components of stress granules are also found in numerous other phase-separated biomolecular condensates under physiological conditions which are inadequately discussed in the context of ALS. In this review, we look beyond stress granules and describe the roles of TDP-43 and FUS in physiological condensates occurring in the nucleus and neurites, such as the nucleolus, Cajal bodies, paraspeckles and neuronal RNA transport granules. We also discuss the consequences of ALS-linked mutations in TDP-43 and FUS on their ability to phase separate into these stress-independent biomolecular condensates and perform their respective functions. Importantly, biomolecular condensates sequester multiple overlapping protein and RNA components, and their dysregulation could contribute to the observed pleiotropic effects of both sporadic and familial ALS on RNA metabolism.
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Affiliation(s)
- Hana Fakim
- Department of Neurosciences, Université de Montréal, and CHUM Research Center, Montréal, QC, Canada
| | - Christine Vande Velde
- Department of Neurosciences, Université de Montréal, and CHUM Research Center, Montréal, QC, Canada.
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McLaurin DM, Tucker SK, Hebert MD. Coilin mediates m6A RNA methylation through phosphorylation of METTL3. Biol Open 2023; 12:bio060116. [PMID: 38050869 PMCID: PMC10714142 DOI: 10.1242/bio.060116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 11/14/2023] [Indexed: 12/07/2023] Open
Abstract
MicroRNAs (miRNAs) are a class of noncoding RNAs that regulate gene expression. An important step in miRNA biogenesis occurs when primary miRNAs are bound and cleaved by the microprocessor to generate precursor miRNAs. Regulation at this step is essential and one such regulator includes m6A RNA methylation, an RNA modification found on primary miRNAs that is installed by METTL3 and bound by hnRNPA2B1. Our lab has recently discovered that the Cajal body marker protein coilin also participates in miRNA biogenesis and hypothesized that coilin may be influencing miRNA biogenesis through m6A RNA methylation. Here we report that coilin suppression reduces m6A on primary Let7a and miR-21. We also found that coilin suppression reduced the protein expression of hnRNPA2B1 and METTL3. We observed an interaction between coilin and ectopically expressed METTL3 and found that coilin suppression reduced the nucleoplasmic portion of METTL3 and blunted ectopic METTL3 phosphorylation. Finally, coilin suppression disrupted the greater METTL3 complex with cofactors METTL14 and WTAP. Collectively, our work has uncovered a role for coilin in mediating m6A RNA methylation and provides an avenue by which coilin participates in miRNA biogenesis.
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Affiliation(s)
- Douglas M. McLaurin
- Department of Cell and Molecular Biology, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
| | - Sara K. Tucker
- Department of Cell and Molecular Biology, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
| | - Michael D. Hebert
- Department of Cell and Molecular Biology, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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5
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Lettin L, Erbay B, Blair GE. Viruses and Cajal Bodies: A Critical Cellular Target in Virus Infection? Viruses 2023; 15:2311. [PMID: 38140552 PMCID: PMC10747631 DOI: 10.3390/v15122311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023] Open
Abstract
Nuclear bodies (NBs) are dynamic structures present in eukaryotic cell nuclei. They are not bounded by membranes and are often considered biomolecular condensates, defined structurally and functionally by the localisation of core components. Nuclear architecture can be reorganised during normal cellular processes such as the cell cycle as well as in response to cellular stress. Many plant and animal viruses target their proteins to NBs, in some cases triggering their structural disruption and redistribution. Although not all such interactions have been well characterised, subversion of NBs and their functions may form a key part of the life cycle of eukaryotic viruses that require the nucleus for their replication. This review will focus on Cajal bodies (CBs) and the viruses that target them. Since CBs are dynamic structures, other NBs (principally nucleoli and promyelocytic leukaemia, PML and bodies), whose components interact with CBs, will also be considered. As well as providing important insights into key virus-host cell interactions, studies on Cajal and associated NBs may identify novel cellular targets for development of antiviral compounds.
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Affiliation(s)
- Lucy Lettin
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK (B.E.)
| | - Bilgi Erbay
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK (B.E.)
- Moleküler Biyoloji ve Genetik Bölümü, Fen Fakültesi, Van Yuzuncu Yil University, Van 65140, Türkiye
| | - G. Eric Blair
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK (B.E.)
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Lazo PA, Morejón-García P. VRK1 variants at the cross road of Cajal body neuropathogenic mechanisms in distal neuropathies and motor neuron diseases. Neurobiol Dis 2023; 183:106172. [PMID: 37257665 DOI: 10.1016/j.nbd.2023.106172] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 05/09/2023] [Accepted: 05/24/2023] [Indexed: 06/02/2023] Open
Abstract
Distal hereditary neuropathies and neuro motor diseases are complex neurological phenotypes associated with pathogenic variants in a large number of genes, but in some the origin is unknown. Recently, rare pathogenic variants of the human VRK1 gene have been associated with these neurological phenotypes. All VRK1 pathogenic variants are recessive, and their clinical presentation occurs in either homozygous or compound heterozygous patients. The pathogenic VRK1 gene pathogenic variants are located in three clusters within the protein sequence. The main, and initial, shared clinical phenotype among VRK1 pathogenic variants is a distal progressive loss of motor and/or sensory function, which includes diseases such as spinal muscular atrophy, Charcot-Marie-Tooth, amyotrophic lateral sclerosis and hereditary spastic paraplegia. In most cases, symptoms start early in infancy, or in utero, and are slowly progressive. Additional neurological symptoms vary among non-related patients, probably because of their different VRK1 variants and their genetic background. The underlying common pathogenic mechanism, by its functional impairment, is a likely consequence of the roles that the VRK1 protein plays in the regulation on the stability and assembly of Cajal bodies, which affect RNA maturation and processing, neuronal migration of RNPs along axons, and DNA-damage responses. Alterations of these processes are associated with several neuro sensory or motor syndromes. The clinical heterogeneity of the neurological phenotypes associated with VRK1 is a likely consequence of the protein complexes in which VRK1 is integrated, which include several proteins known to be associated with Cajal bodies and DNA damage responses. Several hereditary distal neurological diseases are a consequence of pathogenic variants in genes that alter these cellular functions. We conclude that VRK1-related distal hereditary neuropathies and motor neuron diseases represent a novel subgroup of Cajal body related neurological syndromes.
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Affiliation(s)
- Pedro A Lazo
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Salamanca, Salamanca, Spain; Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, Salamanca, Spain.
| | - Patricia Morejón-García
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Salamanca, Salamanca, Spain; Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, Salamanca, Spain.
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7
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Turner BRH, Mellor C, McElroy C, Bowen N, Gu W, Knill C, Itasaki N. Non-ubiquitous expression of core spliceosomal protein SmB/B' in chick and mouse embryos. Dev Dyn 2023; 252:276-293. [PMID: 36058892 PMCID: PMC10087933 DOI: 10.1002/dvdy.537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/02/2022] [Accepted: 08/25/2022] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Although splicing is an integral part of the expression of many genes in our body, genetic syndromes with spliceosomal defects affect only specific tissues. To help understand the mechanism, we investigated the expression pattern of a core protein of the major spliceosome, SmB/B' (Small Nuclear Ribonucleoprotein Polypeptides B/B'), which is encoded by SNRPB. Loss-of-function mutations of SNRPB in humans cause cerebro-costo-mandibular syndrome (CCMS) characterized by rib gaps, micrognathia, cleft palate, and scoliosis. Our expression analysis focused on the affected structures as well as non-affected tissues, using chick and mouse embryos as model animals. RESULTS Embryos at young stages (gastrula) showed ubiquitous expression of SmB/B'. However, the level and pattern of expression became tissue-specific as differentiation proceeded. The regions relating to CCMS phenotypes such as cartilages of ribs and vertebrae and palatal mesenchyme express SmB/B' in the nucleus sporadically. However, cartilages that are not affected in CCMS also showed similar expressions. Another spliceosomal gene, SNRNP200, which mutations cause retinitis pigmentosa, was also prominently expressed in cartilages in addition to the retina. CONCLUSION The expression of SmB/B' is spatiotemporally regulated during embryogenesis despite the ubiquitous requirement of the spliceosome, however, the expression pattern is not strictly correlated with the phenotype presentation.
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Affiliation(s)
| | | | - Clara McElroy
- Faculty of Health Sciences, University of Bristol, Bristol, UK
| | - Natalie Bowen
- Faculty of Life Sciences, University of Bristol, Bristol, UK
| | - Wenjia Gu
- Faculty of Life Sciences, University of Bristol, Bristol, UK
| | - Chris Knill
- Faculty of Life Sciences, University of Bristol, Bristol, UK
| | - Nobue Itasaki
- Faculty of Health Sciences, University of Bristol, Bristol, UK
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8
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Gulyurtlu S, Magon MS, Guest P, Papavasiliou PP, Morrison KD, Prescott AR, Sleeman JE. Condensation properties of stress granules and processing bodies are compromised in Myotonic Dystrophy Type 1. Dis Model Mech 2022; 15:276177. [PMID: 35642886 PMCID: PMC9366894 DOI: 10.1242/dmm.049294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 05/23/2022] [Indexed: 11/26/2022] Open
Abstract
RNA regulation in mammalian cells requires complex physical compartmentalisation, using structures thought to be formed by liquid-liquid phase separation. Disruption of these structures is implicated in numerous degenerative diseases. Myotonic dystrophy type 1 (DM1) is a multi-systemic trinucleotide repeat disorder resulting from an expansion of nucleotides CTG (CTGexp) in the DNA encoding DM1 protein kinase (DMPK). The cellular hallmark of DM1 is the formation of nuclear foci that contain expanded DMPK RNA (CUGexp) (with thymine instead of uracil). We report here the deregulation of stress granules (SGs) and processing bodies (P-bodies), two cytoplasmic structures key for mRNA regulation, in cell culture models of DM1. Alterations to the rates of formation and dispersal of SGs suggest an altered ability of cells to respond to stress associated with DM1, while changes to the structure and dynamics of SGs and P-bodies suggest that a widespread alteration to the biophysical properties of cellular structures is a consequence of the presence of CUGexp RNA. Summary: Validation of an inducible model of myotonic dystrophy type 1 that shows altered cellular stress responses. These involve phase-separated cellular structures also implicated in other degenerative conditions.
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Affiliation(s)
- Selma Gulyurtlu
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
| | - Monika S Magon
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
| | - Patrick Guest
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
| | - Panagiotis P Papavasiliou
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
| | - Kim D Morrison
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
| | - Alan R Prescott
- School of Life Science, University of Dundee, Dundee, DD1 5EH, UK
| | - Judith E Sleeman
- Biomolecular Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
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9
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Gao Z, Zhang W, Chang R, Zhang S, Yang G, Zhao G. Liquid-Liquid Phase Separation: Unraveling the Enigma of Biomolecular Condensates in Microbial Cells. Front Microbiol 2021; 12:751880. [PMID: 34759902 PMCID: PMC8573418 DOI: 10.3389/fmicb.2021.751880] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 09/06/2021] [Indexed: 12/12/2022] Open
Abstract
Numerous examples of microbial phase-separated biomolecular condensates have now been identified following advances in fluorescence imaging and single molecule microscopy technologies. The structure, function, and potential applications of these microbial condensates are currently receiving a great deal of attention. By neatly compartmentalizing proteins and their interactors in membrane-less organizations while maintaining free communication between these macromolecules and the external environment, microbial cells are able to achieve enhanced metabolic efficiency. Typically, these condensates also possess the ability to rapidly adapt to internal and external changes. The biological functions of several phase-separated condensates in small bacterial cells show evolutionary convergence with the biological functions of their eukaryotic paralogs. Artificial microbial membrane-less organelles are being constructed with application prospects in biocatalysis, biosynthesis, and biomedicine. In this review, we provide an overview of currently known biomolecular condensates driven by liquid-liquid phase separation (LLPS) in microbial cells, and we elaborate on their biogenesis mechanisms and biological functions. Additionally, we highlight the major challenges and future research prospects in studying microbial LLPS.
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Affiliation(s)
| | | | | | | | - Guiwen Yang
- College of Life Science, Shandong Normal University, Jinan, China
| | - Guoyan Zhao
- College of Life Science, Shandong Normal University, Jinan, China
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Schilling M, Prusty AB, Boysen B, Oppermann FS, Riedel YL, Husedzinovic A, Rasouli H, König A, Ramanathan P, Reymann J, Erfle H, Daub H, Fischer U, Gruss OJ. TOR signaling regulates liquid phase separation of the SMN complex governing snRNP biogenesis. Cell Rep 2021; 35:109277. [PMID: 34161763 DOI: 10.1016/j.celrep.2021.109277] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 04/23/2021] [Accepted: 05/27/2021] [Indexed: 01/10/2023] Open
Abstract
The activity of the SMN complex in promoting the assembly of pre-mRNA processing UsnRNPs correlates with condensation of the complex in nuclear Cajal bodies. While mechanistic details of its activity have been elucidated, the molecular basis for condensation remains unclear. High SMN complex phosphorylation suggests extensive regulation. Here, we report on systematic siRNA-based screening for modulators of the capacity of SMN to condense in Cajal bodies and identify mTOR and ribosomal protein S6 kinase β-1 as key regulators. Proteomic analysis reveals TOR-dependent phosphorylations in SMN complex subunits. Using stably expressed or optogenetically controlled phospho mutants, we demonstrate that serine 49 and 63 phosphorylation of human SMN controls the capacity of the complex to condense in Cajal bodies via liquid-liquid phase separation. Our findings link SMN complex condensation and UsnRNP biogenesis to cellular energy levels and suggest modulation of TOR signaling as a rational concept for therapy of the SMN-linked neuromuscular disorder spinal muscular atrophy.
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Affiliation(s)
- Maximilian Schilling
- Institut für Genetik, Rheinische Friedrich-Wilhelms Universität Bonn, 53115 Bonn, Germany
| | - Archana B Prusty
- Theodor Boveri Institute, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Björn Boysen
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | | | - Yannick L Riedel
- Institut für Genetik, Rheinische Friedrich-Wilhelms Universität Bonn, 53115 Bonn, Germany
| | - Alma Husedzinovic
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Homa Rasouli
- Evotec SE, Am Klopferspitz 19a, 82152 Martinsried, Germany
| | - Angelika König
- Institut für Genetik, Rheinische Friedrich-Wilhelms Universität Bonn, 53115 Bonn, Germany
| | - Pradhipa Ramanathan
- Theodor Boveri Institute, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Jürgen Reymann
- Advanced Biological Screening Facility, BioQuant Centre, Universität Heidelberg, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Holger Erfle
- Advanced Biological Screening Facility, BioQuant Centre, Universität Heidelberg, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Henrik Daub
- Evotec SE, Am Klopferspitz 19a, 82152 Martinsried, Germany
| | - Utz Fischer
- Theodor Boveri Institute, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Oliver J Gruss
- Institut für Genetik, Rheinische Friedrich-Wilhelms Universität Bonn, 53115 Bonn, Germany; Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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11
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Imada T, Shimi T, Kaiho A, Saeki Y, Kimura H. RNA polymerase II condensate formation and association with Cajal and histone locus bodies in living human cells. Genes Cells 2021; 26:298-312. [PMID: 33608942 PMCID: PMC8252594 DOI: 10.1111/gtc.12840] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Revised: 02/14/2021] [Accepted: 02/15/2021] [Indexed: 12/24/2022]
Abstract
In eukaryotic nuclei, a number of phase‐separated nuclear bodies (NBs) are present. RNA polymerase II (Pol II) is the main player in transcription and forms large condensates in addition to localizing at numerous transcription foci. Cajal bodies (CBs) and histone locus bodies (HLBs) are NBs that are involved in transcriptional and post‐transcriptional regulation of small nuclear RNA and histone genes. By live‐cell imaging using human HCT116 cells, we here show that Pol II condensates (PCs) nucleated near CBs and HLBs, and the number of PCs increased during S phase concomitantly with the activation period of histone genes. Ternary PC–CB–HLB associates were formed via three pathways: nucleation of PCs and HLBs near CBs, interaction between preformed PC–HLBs with CBs and nucleation of PCs near preformed CB–HLBs. Coilin knockout increased the co‐localization rate between PCs and HLBs, whereas the number, nucleation timing and phosphorylation status of PCs remained unchanged. Depletion of PCs did not affect CBs and HLBs. Treatment with 1,6‐hexanediol revealed that PCs were more liquid‐like than CBs and HLBs. Thus, PCs are dynamic structures often nucleated following the activation of gene clusters associated with other NBs.
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Affiliation(s)
- Takashi Imada
- School of Life Science and TechnologyTokyo Institute of TechnologyYokohamaJapan
| | - Takeshi Shimi
- World Research Hub InitiativeInstitute of Innovative ResearchTokyo Institute of TechnologyYokohamaJapan
- Cell Biology CenterInstitute of Innovative ResearchTokyo Institute of TechnologyYokohamaJapan
| | - Ai Kaiho
- Protein Metabolism ProjectTokyo Metropolitan Institute of Medical ScienceTokyoJapan
- Institute for Advanced Life SciencesHoshi UniversityTokyoJapan
| | - Yasushi Saeki
- Protein Metabolism ProjectTokyo Metropolitan Institute of Medical ScienceTokyoJapan
| | - Hiroshi Kimura
- School of Life Science and TechnologyTokyo Institute of TechnologyYokohamaJapan
- World Research Hub InitiativeInstitute of Innovative ResearchTokyo Institute of TechnologyYokohamaJapan
- Cell Biology CenterInstitute of Innovative ResearchTokyo Institute of TechnologyYokohamaJapan
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12
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Campillo-Marcos I, García-González R, Navarro-Carrasco E, Lazo PA. The human VRK1 chromatin kinase in cancer biology. Cancer Lett 2021; 503:117-128. [PMID: 33516791 DOI: 10.1016/j.canlet.2020.12.032] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/30/2020] [Accepted: 12/21/2020] [Indexed: 01/08/2023]
Abstract
VRK1 is a nuclear Ser-Thr chromatin kinase that does not mutate in cancer, and is overexpressed in many types of tumors and associated with a poor prognosis. Chromatin VRK1 phosphorylates several transcription factors, including p53, histones and proteins implicated in DNA damage response pathways. In the context of cell proliferation, VRK1 regulates entry in cell cycle, chromatin condensation in G2/M, Golgi fragmentation, Cajal body dynamics and nuclear envelope assembly in mitosis. This kinase also controls the initial chromatin relaxation associated with histone acetylation, and the non-homologous-end joining (NHEJ) DNA repair pathway, which involves sequential steps such as γH2AX, NBS1 and 53BP1 foci formation, all phosphorylated by VRK1, in response to ionizing radiation or chemotherapy. In addition, VRK1 can be an alternative target for therapies based on synthetic lethality strategies. Therefore, VRK1 roles on proliferation have a pro-tumorigenic effect. Functions regulating chromatin stability and DNA damage responses have a protective anti-tumor role in normal cells, but in tumor cells can also facilitate resistance to genotoxic treatments.
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Affiliation(s)
- Ignacio Campillo-Marcos
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular Del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad de Salamanca, 37007 Salamanca, Spain; Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, 37007 Salamanca, Spain.
| | - Raúl García-González
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular Del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad de Salamanca, 37007 Salamanca, Spain; Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, 37007 Salamanca, Spain.
| | - Elena Navarro-Carrasco
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular Del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad de Salamanca, 37007 Salamanca, Spain; Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, 37007 Salamanca, Spain.
| | - Pedro A Lazo
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular Del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad de Salamanca, 37007 Salamanca, Spain.
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13
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Vladimirova O, De Leo A, Deng Z, Wiedmer A, Hayden J, Lieberman PM. Phase separation and DAXX redistribution contribute to LANA nuclear body and KSHV genome dynamics during latency and reactivation. PLoS Pathog 2021; 17:e1009231. [PMID: 33471863 PMCID: PMC7943007 DOI: 10.1371/journal.ppat.1009231] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 03/09/2021] [Accepted: 12/08/2020] [Indexed: 12/14/2022] Open
Abstract
Liquid-liquid phase separation (LLPS) can drive formation of diverse and essential macromolecular structures, including those specified by viruses. Kaposi’s Sarcoma-Associated Herpesvirus (KSHV) genomes associate with the viral encoded Latency-Associated Nuclear Antigen (LANA) to form stable nuclear bodies (NBs) during latent infection. Here, we show that LANA-NB formation and KSHV genome conformation involves LLPS. Using LLPS disrupting solvents, we show that LANA-NBs are partially disrupted, while DAXX and PML foci are highly resistant. LLPS disruption altered the LANA-dependent KSHV chromosome conformation but did not stimulate lytic reactivation. We found that LANA-NBs undergo major morphological transformation during KSHV lytic reactivation to form LANA-associated replication compartments encompassing KSHV DNA. DAXX colocalizes with the LANA-NBs during latency but is evicted from the LANA-associated lytic replication compartments. These findings indicate the LANA-NBs are dynamic super-molecular nuclear structures that partly depend on LLPS and undergo morphological transitions corresponding to the different modes of viral replication. During latent infection, gamma-herpesvirus genomes are maintained as extrachromosomal circular DNA, referred to as episomes, by dedicated viral-encoded episome maintenance proteins. KSHV-encoded LANA maintains viral episomes through binding as an oligomeric protein to repetitive DNA elements in the viral terminal repeats (TRs). Viral episomes can be visualized as LANA-associated nuclear bodies (LANA-NBs). Here, we show that LANA-NBs utilize mechanisms of self-assembly through liquid-liquid phase separation (LLPS) to build dynamic structures that change during cell cycle and viral life cycle. We find that DAXX is a component of the latent phase LANA-NBs, but is evicted during the transition to lytic replication where LANA remains associated with KSHV DNA to form a ring-like replication compartment.
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Affiliation(s)
| | - Alessandra De Leo
- Department of Immunology, H. Lee Moffit Cancer and Research Center, Tampa Florida, United States of America
| | - Zhong Deng
- The Wistar Institute, Philadelphia, United States of America
| | - Andreas Wiedmer
- The Wistar Institute, Philadelphia, United States of America
| | - James Hayden
- The Wistar Institute, Philadelphia, United States of America
| | - Paul M. Lieberman
- The Wistar Institute, Philadelphia, United States of America
- * E-mail:
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14
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Corbet GA, Parker R. RNP Granule Formation: Lessons from P-Bodies and Stress Granules. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2020; 84:203-215. [PMID: 32482896 DOI: 10.1101/sqb.2019.84.040329] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
It is now clear that cells form a wide collection of large RNA-protein assemblies, referred to as RNP granules. RNP granules exist in bacterial cells and can be found in both the cytosol and nucleus of eukaryotic cells. Recent approaches have begun to define the RNA and protein composition of a number of RNP granules. Herein, we review the composition and assembly of RNP granules, as well as how RNPs are targeted to RNP granules using stress granules and P-bodies as model systems. Taken together, these reveal that RNP granules form through the summative effects of a combination of protein-protein, protein-RNA, and RNA-RNA interactions. Similarly, the partitioning of individual RNPs into stress granules is determined by the combinatorial effects of multiple elements. Thus, RNP granules are assemblies generally dominated by combinatorial effects, thereby providing rich opportunities for biological regulation.
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Affiliation(s)
- Giulia Ada Corbet
- Department of Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - Roy Parker
- Department of Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
- Howard Hughes Medical Institute, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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15
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The Nuclear Arsenal of Cilia. Dev Cell 2019; 49:161-170. [DOI: 10.1016/j.devcel.2019.03.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 12/07/2018] [Accepted: 03/08/2019] [Indexed: 12/31/2022]
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16
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Sawyer IA, Sturgill D, Dundr M. Membraneless nuclear organelles and the search for phases within phases. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 10:e1514. [DOI: 10.1002/wrna.1514] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/20/2018] [Accepted: 09/27/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Iain A. Sawyer
- Department of Cell Biology and Anatomy, Chicago Medical School Rosalind Franklin University of Medicine and Science North Chicago Illinois
- Laboratory of Receptor Biology and Gene Expression National Cancer Institute, National Institutes of Health Bethesda Maryland
| | - David Sturgill
- Laboratory of Receptor Biology and Gene Expression National Cancer Institute, National Institutes of Health Bethesda Maryland
| | - Miroslav Dundr
- Department of Cell Biology and Anatomy, Chicago Medical School Rosalind Franklin University of Medicine and Science North Chicago Illinois
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17
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Thompson LW, Morrison KD, Shirran SL, Groen EJN, Gillingwater TH, Botting CH, Sleeman JE. Neurochondrin interacts with the SMN protein suggesting a novel mechanism for spinal muscular atrophy pathology. J Cell Sci 2018; 131:jcs.211482. [PMID: 29507115 PMCID: PMC5963842 DOI: 10.1242/jcs.211482] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 02/16/2018] [Indexed: 12/15/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an inherited neurodegenerative condition caused by a reduction in the amount of functional survival motor neuron (SMN) protein. SMN has been implicated in transport of mRNA in neural cells for local translation. We previously identified microtubule-dependent mobile vesicles rich in SMN and SNRPB, a member of the Sm family of small nuclear ribonucleoprotein (snRNP)-associated proteins, in neural cells. By comparing the interactomes of SNRPB and SNRPN, a neural-specific Sm protein, we now show that the essential neural protein neurochondrin (NCDN) interacts with Sm proteins and SMN in the context of mobile vesicles in neurites. NCDN has roles in protein localisation in neural cells and in maintenance of cell polarity. NCDN is required for the correct localisation of SMN, suggesting they may both be required for formation and transport of trafficking vesicles. NCDN may have potential as a therapeutic target for SMA together with, or in place of the targeting of SMN expression. This article has an associated First Person interview with the first author of the paper. Highlighted Article: The essential neural protein neurochondrin interacts with the spinal muscular atrophy (SMA) protein SMN in cell lines and in mice. This might be relevant to the molecular pathology of SMA.
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Affiliation(s)
- Luke W Thompson
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Kim D Morrison
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Sally L Shirran
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Ewout J N Groen
- Edinburgh Medical School, Biomedical Sciences and Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School, Biomedical Sciences and Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK
| | - Catherine H Botting
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Judith E Sleeman
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
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18
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Lafarga V, Tapia O, Sharma S, Bengoechea R, Stoecklin G, Lafarga M, Berciano MT. CBP-mediated SMN acetylation modulates Cajal body biogenesis and the cytoplasmic targeting of SMN. Cell Mol Life Sci 2018; 75:527-546. [PMID: 28879433 PMCID: PMC11105684 DOI: 10.1007/s00018-017-2638-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 08/09/2017] [Accepted: 08/29/2017] [Indexed: 01/12/2023]
Abstract
The survival of motor neuron (SMN) protein plays an essential role in the biogenesis of spliceosomal snRNPs and the molecular assembly of Cajal bodies (CBs). Deletion of or mutations in the SMN1 gene cause spinal muscular atrophy (SMA) with degeneration and loss of motor neurons. Reduced SMN levels in SMA lead to deficient snRNP biogenesis with consequent splicing pathology. Here, we demonstrate that SMN is a novel and specific target of the acetyltransferase CBP (CREB-binding protein). Furthermore, we identify lysine (K) 119 as the main acetylation site in SMN. Importantly, SMN acetylation enhances its cytoplasmic localization, causes depletion of CBs, and reduces the accumulation of snRNPs in nuclear speckles. In contrast, the acetylation-deficient SMNK119R mutant promotes formation of CBs and a novel category of promyelocytic leukemia (PML) bodies enriched in this protein. Acetylation increases the half-life of SMN protein, reduces its cytoplasmic diffusion rate and modifies its interactome. Hence, SMN acetylation leads to its dysfunction, which explains the ineffectiveness of HDAC (histone deacetylases) inhibitors in SMA therapy despite their potential to increase SMN levels.
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Affiliation(s)
- Vanesa Lafarga
- Laboratory of Genomic Instability, "Centro Nacional de Investigaciones Oncológicas" (CNIO), 28024, Madrid, Spain
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120, Heidelberg, Germany
| | - Olga Tapia
- Department of Anatomy and Cell Biology, "Centro de Investigación en Red de Enfermedades Neurodegenerativas" (CIBERNED), University of Cantabria-IDIVAL, 39011, Santander, Spain
| | - Sahil Sharma
- Department of Biochemistry, Center for Biomedicine and Medical Technology Mannheim (CBTM), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), 68167, Mannheim, Germany
- German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, 68167, Mannheim, Germany
| | - Rocio Bengoechea
- Department of Neurology, The Hope Center for Neurological Diseases, School of Medicine of Washington University, St. Louis, 63110, USA
| | - Georg Stoecklin
- Department of Biochemistry, Center for Biomedicine and Medical Technology Mannheim (CBTM), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), 68167, Mannheim, Germany
- German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, 68167, Mannheim, Germany
| | - Miguel Lafarga
- Department of Anatomy and Cell Biology, "Centro de Investigación en Red de Enfermedades Neurodegenerativas" (CIBERNED), University of Cantabria-IDIVAL, 39011, Santander, Spain
| | - Maria T Berciano
- Department of Anatomy and Cell Biology, "Centro de Investigación en Red de Enfermedades Neurodegenerativas" (CIBERNED), University of Cantabria-IDIVAL, 39011, Santander, Spain.
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19
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Raimer AC, Gray KM, Matera AG. SMN - A chaperone for nuclear RNP social occasions? RNA Biol 2017; 14:701-711. [PMID: 27648855 PMCID: PMC5519234 DOI: 10.1080/15476286.2016.1236168] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/01/2016] [Accepted: 09/09/2016] [Indexed: 12/24/2022] Open
Abstract
Survival Motor Neuron (SMN) protein localizes to both the nucleus and the cytoplasm. Cytoplasmic SMN is diffusely localized in large oligomeric complexes with core member proteins, called Gemins. Biochemical and cell biological studies have demonstrated that the SMN complex is required for the cytoplasmic assembly and nuclear transport of Sm-class ribonucleoproteins (RNPs). Nuclear SMN accumulates with spliceosomal small nuclear (sn)RNPs in Cajal bodies, sub-domains involved in multiple facets of snRNP maturation. Thus, the SMN complex forms stable associations with both nuclear and cytoplasmic snRNPs, and plays a critical role in their biogenesis. In this review, we focus on potential functions of the nuclear SMN complex, with particular emphasis on its role within the Cajal body.
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Affiliation(s)
- Amanda C. Raimer
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Kelsey M. Gray
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - A. Gregory Matera
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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20
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Sawyer IA, Hager GL, Dundr M. Specific genomic cues regulate Cajal body assembly. RNA Biol 2017; 14:791-803. [PMID: 27715441 PMCID: PMC5519236 DOI: 10.1080/15476286.2016.1243648] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/06/2016] [Accepted: 09/27/2016] [Indexed: 02/07/2023] Open
Abstract
The assembly of specialized sub-nuclear microenvironments known as nuclear bodies (NBs) is important for promoting efficient nuclear function. In particular, the Cajal body (CB), a prominent NB that facilitates spliceosomal snRNP biogenesis, assembles in response to genomic cues. Here, we detail the factors that regulate CB assembly and structural maintenance. These include the importance of transcription at nucleating gene loci, the grouping of these genes on human chromosomes 1, 6 and 17, as well as cell cycle and biochemical regulation of CB protein function. We also speculate on the correlation between CB formation and RNA splicing levels in neurons and cancer. The timing and location of these specific molecular events is critical to CB assembly and its contribution to genome function. However, further work is required to explore the emerging biophysical characteristics of CB assembly and the impact upon subsequent genome reorganization.
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Affiliation(s)
- Iain A. Sawyer
- Department of Cell Biology, Rosalind Franklin University of Medicine & Science, Chicago Medical School, North Chicago, IL, USA
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Gordon L. Hager
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Miroslav Dundr
- Department of Cell Biology, Rosalind Franklin University of Medicine & Science, Chicago Medical School, North Chicago, IL, USA
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21
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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: 60] [Impact Index Per Article: 6.7] [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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22
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Ono M, Yamada K, Bensaddek D, Afzal V, Biddlestone J, Ortmann B, Mudie S, Boivin V, Scott MS, Rocha S, Lamond AI. Enhanced snoMEN Vectors Facilitate Establishment of GFP-HIF-1α Protein Replacement Human Cell Lines. PLoS One 2016; 11:e0154759. [PMID: 27128805 PMCID: PMC4851398 DOI: 10.1371/journal.pone.0154759] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 04/19/2016] [Indexed: 11/18/2022] Open
Abstract
The snoMEN (snoRNA Modulator of gene ExpressioN) vector technology was developed from a human box C/D snoRNA, HBII-180C, which contains an internal sequence that can be manipulated to make it complementary to RNA targets, allowing knock-down of targeted genes. Here we have screened additional human nucleolar snoRNAs and assessed their application for gene specific knock-downs to improve the efficiency of snoMEN vectors. We identify and characterise a new snoMEN vector, termed 47snoMEN, that is derived from box C/D snoRNA U47, demonstrating its use for knock-down of both endogenous cellular proteins and G/YFP-fusion proteins. Using multiplex 47snoMEM vectors that co-express multiple 47snoMEN in a single transcript, each of which can target different sites in the same mRNA, we document >3-fold increase in knock-down efficiency when compared with the original HBII-180C based snoMEN. The multiplex 47snoMEM vector allowed the construction of human protein replacement cell lines with improved efficiency, including the establishment of novel GFP–HIF-1α replacement cells. Quantitative mass spectrometry analysis confirmed the enhanced efficiency and specificity of protein replacement using the 47snoMEN-PR vectors. The 47snoMEN vectors expand the potential applications for snoMEN technology in gene expression studies, target validation and gene therapy.
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Affiliation(s)
- Motoharu Ono
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Kayo Yamada
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Dalila Bensaddek
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Vackar Afzal
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - John Biddlestone
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Brian Ortmann
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Sharon Mudie
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Vincent Boivin
- Department of Biochemistry and RNA Group, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Canada
| | - Michelle S. Scott
- Department of Biochemistry and RNA Group, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Canada
| | - Sonia Rocha
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Angus I. Lamond
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
- * E-mail:
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23
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Mitrea DM, Kriwacki RW. Phase separation in biology; functional organization of a higher order. Cell Commun Signal 2016; 14:1. [PMID: 26727894 PMCID: PMC4700675 DOI: 10.1186/s12964-015-0125-7] [Citation(s) in RCA: 500] [Impact Index Per Article: 55.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 12/29/2015] [Indexed: 12/18/2022] Open
Abstract
Inside eukaryotic cells, macromolecules are partitioned into membrane-bounded compartments and, within these, some are further organized into non-membrane-bounded structures termed membrane-less organelles. The latter structures are comprised of heterogeneous mixtures of proteins and nucleic acids and assemble through a phase separation phenomenon similar to polymer condensation. Membrane-less organelles are dynamic structures maintained through multivalent interactions that mediate diverse biological processes, many involved in RNA metabolism. They rapidly exchange components with the cellular milieu and their properties are readily altered in response to environmental cues, often implicating membrane-less organelles in responses to stress signaling. In this review, we discuss: (1) the functional roles of membrane-less organelles, (2) unifying structural and mechanistic principles that underlie their assembly and disassembly, and (3) established and emerging methods used in structural investigations of membrane-less organelles.
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Affiliation(s)
- Diana M Mitrea
- Department of Structural Biology, 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, 38163, USA.
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24
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Hyjek M, Wojciechowska N, Rudzka M, Kołowerzo-Lubnau A, Smoliński DJ. Spatial regulation of cytoplasmic snRNP assembly at the cellular level. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:7019-30. [PMID: 26320237 PMCID: PMC4765780 DOI: 10.1093/jxb/erv399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Small nuclear ribonucleoproteins (snRNPs) play a crucial role in pre-mRNA splicing in all eukaryotic cells. In contrast to the relatively broad knowledge on snRNP assembly within the nucleus, the spatial organization of the cytoplasmic stages of their maturation remains poorly understood. Nevertheless, sparse research indicates that, similar to the nuclear steps, the crucial processes of cytoplasmic snRNP assembly may also be strictly spatially regulated. In European larch microsporocytes, it was determined that the cytoplasmic assembly of snRNPs within a cell might occur in two distinct spatial manners, which depend on the rate of de novo snRNP formation in relation to the steady state of these particles within the nucleus. During periods of moderate expression of splicing elements, the cytoplasmic assembly of snRNPs occurred diffusely throughout the cytoplasm. Increased expression of both Sm proteins and U snRNA triggered the accumulation of these particles within distinct, non-membranous RNP-rich granules, which are referred to as snRNP-rich cytoplasmic bodies.
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Affiliation(s)
- Malwina Hyjek
- Department of Cell Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, Toruń, 87-100, Poland Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń Poland
| | - Natalia Wojciechowska
- Department of Cell Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, Toruń, 87-100, Poland Department of General Botany, Institute of Experimental Biology, Faculty of Biology, A. Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Magda Rudzka
- Department of Cell Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, Toruń, 87-100, Poland Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń Poland
| | - Agnieszka Kołowerzo-Lubnau
- Department of Cell Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, Toruń, 87-100, Poland Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń Poland
| | - Dariusz Jan Smoliński
- Department of Cell Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, Toruń, 87-100, Poland Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń Poland
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25
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Förthmann B, Grothe C, Claus P. A nuclear odyssey: fibroblast growth factor-2 (FGF-2) as a regulator of nuclear homeostasis in the nervous system. Cell Mol Life Sci 2015; 72:1651-62. [PMID: 25552245 PMCID: PMC11113852 DOI: 10.1007/s00018-014-1818-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/10/2014] [Accepted: 12/19/2014] [Indexed: 01/07/2023]
Abstract
Nuclear localization of classical growth factors is a well-known phenomenon but still remains a molecular and cellular conundrum. Fibroblast growth factor-2 (FGF-2) is an excellent example of a protein which functions as an extracellular molecule involved in canonical receptor tyrosine kinase signaling as well as displaying intracellular functions. Paracrine and nuclear functions are two important sides of the same protein. FGF-2 is expressed in isoforms with different molecular weights from one mRNA species. In rodents, all of these isoforms become imported to the nucleus. In this review, we discuss structural and functional aspects of FGF-2 isoforms in the nervous system. The nuclear odyssey of FGF-2 is reflected by nuclear dynamics, localization to nuclear bodies such as nucleoli, binding to chromatin and engagement in various protein interactions. Recently discovered molecular partnerships of the isoforms shed light on their nuclear functions, thereby greatly extending our knowledge of the multifaceted functions of FGF-2.
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Affiliation(s)
- Benjamin Förthmann
- Department of Neuroanatomy, Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | - Claudia Grothe
- Department of Neuroanatomy, Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| | - Peter Claus
- Department of Neuroanatomy, Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
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Muro E, Gébrane-Younès J, Jobart-Malfait A, Louvet E, Roussel P, Hernandez-Verdun D. The traffic of proteins between nucleolar organizer regions and prenucleolar bodies governs the assembly of the nucleolus at exit of mitosis. Nucleus 2014. [DOI: 10.4161/nucl.11334] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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27
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Nuclear bodies: new insights into assembly/dynamics and disease relevance. Curr Opin Cell Biol 2014; 28:76-83. [DOI: 10.1016/j.ceb.2014.03.004] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 03/10/2014] [Accepted: 03/12/2014] [Indexed: 01/15/2023]
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Transcriptionally correlated subcellular dynamics of MBNL1 during lens development and their implication for the molecular pathology of myotonic dystrophy type 1. Biochem J 2014; 458:267-80. [PMID: 24354850 DOI: 10.1042/bj20130870] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
DM1 (myotonic dystrophy type 1) is caused by elongation of a CTG repeat in the DMPK (dystrophia myotonica-protein kinase) gene. mRNA transcripts containing these CUGexp (CUG expansion) repeats form accumulations, or foci, in the nucleus of the cell. The pathogenesis of DM1 is proposed to result from inappropriate patterns of alternative splicing caused by sequestration of the developmentally regulated alternative splicing factor MBNL1 (muscleblind-like 1) by these foci. Since eye lens cataract is a common feature of DM1 we have examined the distribution and dynamics of MBNL1 in lens epithelial cell lines derived from patients with DM1. The results of the present study demonstrate that only a small proportion of nuclear MBNL1 accumulates in CUGexp pre-mRNA foci. MBNL1 is, however, highly mobile and changes localization in response to altered transcription and splicing activity. Moreover, immunolocalization studies in lens sections suggest that a change in MBNL1 distribution is important during lens growth and differentiation. Although these data suggest that the loss of MBNL1 function due to accumulation in foci is an unlikely explanation for DM1 symptoms in the lens, they do demonstrate a strong relationship between the subcellular MBNL1 localization and pathways of cellular differentiation, providing an insight into the sensitivity of the lens to changes in MBNL1 distribution.
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Li Y, Fong KW, Tang M, Han X, Gong Z, Ma W, Hebert M, Songyang Z, Chen J. Fam118B, a newly identified component of Cajal bodies, is required for Cajal body formation, snRNP biogenesis and cell viability. J Cell Sci 2014; 127:2029-39. [PMID: 24569877 DOI: 10.1242/jcs.143453] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cajal bodies are specialized and dynamic compartments in the nucleus that are involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs). Because of the dynamic and varied roles of Cajal bodies, it is of great interest to identify the components of Cajal bodies to better understand their functions. We performed a genome-wide screen to identify proteins that colocalize with coilin, the marker protein of Cajal bodies. In this study, we identified and characterized Fam118B as a newly discovered component of Cajal bodies. Fam118B is widely expressed in a variety of cell lines derived from various origins. Overexpression of Fam118B changes the canonical morphology of Cajal bodies, whereas depletion of Fam118B disrupts the localization of components of Cajal bodies, including coilin, the survival of motor neuron protein (SMN) and the Sm protein D1 (SmD1, also known as SNRPD1). Moreover, depletion of Fam118B reduces splicing capacity and inhibits cell proliferation. In addition, Fam118B associates with coilin and SMN proteins. Fam118B depletion reduces symmetric dimethylarginine modification of SmD1, which in turn diminishes the binding of SMN to this Sm protein. Taken together, these data indicate that Fam118B, by regulating SmD1 symmetric dimethylarginine modification, plays an important role in Cajal body formation, snRNP biogenesis and cell viability.
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Affiliation(s)
- Yujing Li
- State Key Laboratory for Biocontrol and Key Laboratory of Gene Engineering of Ministry of Education, Sun Yat-Sen University-Baylor College of Medicine Joint Research Center on Biomedical Sciences, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
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Tapia O, Lafarga V, Bengoechea R, Palanca A, Lafarga M, Berciano MT. The SMN Tudor SIM-like domain is key to SmD1 and coilin interactions and to Cajal body biogenesis. J Cell Sci 2014; 127:939-46. [PMID: 24413165 DOI: 10.1242/jcs.138537] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cajal bodies (CBs) are nuclear organelles involved in the maturation of spliceosomal small nuclear ribonucleoproteins (snRNPs). They concentrate coilin, snRNPs and the survival motor neuron protein (SMN). Dysfunction of CB assembly occurs in spinal muscular atrophy (SMA). Here, we demonstrate that SMN is a SUMO1 target that has a small ubiquitin-related modifier (SUMO)-interacting motif (SIM)-like motif in the Tudor domain. The expression of SIM-like mutant constructs abolishes the interaction of SMN with the spliceosomal SmD1 (also known as SNRPD1), severely decreases SMN-coilin interaction and prevents CB assembly. Accordingly, the SMN SIM-like-mediated interactions are important for CB biogenesis and their dysfunction can be involved in SMA pathophysiology.
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Affiliation(s)
- Olga Tapia
- Department of Anatomy and Cell Biology, University of Cantabria-IFIMAV, Santander E-39008, Spain
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31
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Grob A, McStay B. Construction of synthetic nucleoli and what it tells us about propagation of sub-nuclear domains through cell division. Cell Cycle 2014; 13:2501-8. [PMID: 25486191 PMCID: PMC4614152 DOI: 10.4161/15384101.2014.949124] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 07/16/2014] [Accepted: 07/16/2014] [Indexed: 11/19/2022] Open
Abstract
The cell nucleus is functionally compartmentalized into numerous membraneless and dynamic, yet defined, bodies. The cell cycle inheritance of these nuclear bodies (NBs) is poorly understood at the molecular level. In higher eukaryotes, their propagation is challenged by cell division through an "open" mitosis, where the nuclear envelope disassembles along with most NBs. A deeper understanding of the mechanisms involved can be achieved using the engineering principles of synthetic biology to construct artificial NBs. Successful biogenesis of such synthetic NBs demonstrates knowledge of the basic mechanisms involved. Application of this approach to the nucleolus, a paradigm of nuclear organization, has highlighted a key role for mitotic bookmarking in the cell cycle propagation of NBs.
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Key Words
- 1°, primary
- 2°, secondary
- CBs, Cajal bodies
- CDK, cyclin-dependent kinase
- DFC, dense fibrillar component
- DJ, distal junction
- FCs, fibrillar centers
- GC, granular component
- HLBs, histone locus bodies
- HMG, high mobility group
- IGS, intergenic spacers
- NBs, nuclear bodies
- NORs, nucleolar organizer regions
- Nucleolar Organizer Region (NOR)
- PJ, proximal junction
- PML, promyelocytic leukemia
- PNBs, pre-nucleolar bodies
- TFs, transcription factors
- UBF
- UBF, Upstream binding factor
- XEn, Xenopus enhancer
- cell cycle
- mitotic bookmarking
- neo-NOR
- neonucleoli
- nuclear bodies
- nucleolus
- pol, RNA polymerase
- pre-rRNA, precursor rRNA
- pseudo-NOR
- rDNA, ribosomal genes
- rRNA, ribosomal RNA; RNP, ribonucleoprotein
- synthetic biology
- t-UTPs, transcription U 3 proteins
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Affiliation(s)
- Alice Grob
- Center for Chromosome Biology; School of Natural Sciences; National University of Ireland; Galway, Ireland
| | - Brian McStay
- Center for Chromosome Biology; School of Natural Sciences; National University of Ireland; Galway, Ireland
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Alawi F, Lin P. Dyskerin localizes to the mitotic apparatus and is required for orderly mitosis in human cells. PLoS One 2013; 8:e80805. [PMID: 24303026 PMCID: PMC3841160 DOI: 10.1371/journal.pone.0080805] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 10/15/2013] [Indexed: 11/18/2022] Open
Abstract
Dyskerin is a highly conserved, nucleolar RNA-binding protein with established roles in small nuclear ribonucleoprotein biogenesis, telomerase and telomere maintenance and precursor rRNA processing. Telomerase is functional during S phase and the bulk of rRNA maturation occurs during G1 and S phases; both processes are inactivated during mitosis. Yet, we show that during the course of cell cycle progression, human dyskerin expression peaks during G2/M in parallel with the upregulation of pro-mitotic factors. Dyskerin redistributed from the nucleolus in interphase cells to the perichromosomal region during prometaphase, metaphase and anaphase. With continued anaphase progression, dyskerin also localized to the cytoplasm within the mid-pole region. Loss of dyskerin function via siRNA-mediated depletion promoted G2/M accumulation and this was accompanied by an increased mitotic index and activation of the spindle assembly checkpoint. Live cell imaging further revealed an array of mitotic defects including delayed prometaphase progression, a significantly increased incidence of multi-polar spindles, and anaphase bridges culminating in micronucleus formation. Together, these findings suggest that dyskerin is a highly dynamic protein throughout the cell cycle and increases the repertoire of fundamental cellular processes that are disrupted by absence of its normal function.
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Affiliation(s)
- Faizan Alawi
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
| | - Ping Lin
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
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Förthmann B, Brinkmann H, Ratzka A, Stachowiak MK, Grothe C, Claus P. Immobile survival of motoneuron (SMN) protein stored in Cajal bodies can be mobilized by protein interactions. Cell Mol Life Sci 2013; 70:2555-68. [PMID: 23334184 PMCID: PMC11113639 DOI: 10.1007/s00018-012-1242-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 11/29/2012] [Accepted: 12/10/2012] [Indexed: 12/25/2022]
Abstract
Reduced levels of survival of motoneuron (SMN) protein lead to spinal muscular atrophy, but it is still unknown how SMN protects motoneurons in the spinal cord against degeneration. In the nucleus, SMN is associated with two types of nuclear bodies denoted as gems and Cajal bodies (CBs). The 23 kDa isoform of fibroblast growth factor-2 (FGF-2(23)) is a nuclear protein that binds to SMN and destabilizes the SMN-Gemin2 complex. In the present study, we show that FGF-2(23) depletes SMN from CBs without affecting their general structure. FRAP analysis of SMN-EGFP in CBs demonstrated that the majority of SMN in CBs remained mobile and allowed quantification of fast, slow and immobile nuclear SMN populations. The potential for SMN release was confirmed by in vivo photoconversion of SMN-Dendra2, indicating that CBs concentrate immobile SMN that could have a specialized function in CBs. FGF-2(23) accelerated SMN release from CBs, accompanied by a conversion of immobile SMN into a mobile population. Furthermore, FGF-2(23) caused snRNP accumulation in CBs. We propose a model in which Cajal bodies store immobile SMN that can be mobilized by its nuclear interaction partner FGF-2(23), leading to U4 snRNP accumulation in CBs, indicating a role for immobile SMN in tri-snRNP assembly.
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Affiliation(s)
- Benjamin Förthmann
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| | - Hella Brinkmann
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | - Andreas Ratzka
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | - Michal K. Stachowiak
- Department of Pathology and Anatomical Sciences, State University of New York, Buffalo, NY 14214 USA
| | - Claudia Grothe
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
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34
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Pontes O, Vitins A, Ream TS, Hong E, Pikaard CS, Costa-Nunes P. Intersection of small RNA pathways in Arabidopsis thaliana sub-nuclear domains. PLoS One 2013; 8:e65652. [PMID: 23776518 PMCID: PMC3680462 DOI: 10.1371/journal.pone.0065652] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 04/25/2013] [Indexed: 12/22/2022] Open
Abstract
In Arabidopsis thaliana, functionally diverse small RNA (smRNA) pathways bring about decreased RNA accumulation of target genes via several different mechanisms. Cytological experiments have suggested that the processing of microRNAs (miRNAs) and heterochromatic small interfering RNAs (hc-siRNAs) occurs within a specific nuclear domain that can present Cajal Body (CB) characteristics. It is unclear whether single or multiple smRNA-related domains are found within the same CB and how specialization of the smRNA pathways is determined within this specific sub-compartment. To ascertain whether nuclear smRNA centers are spatially related, we localized key proteins required for siRNA or miRNA biogenesis by immunofluorescence analysis. The intranuclear distribution of the proteins revealed that hc-siRNA, miRNA and trans-acting siRNA (ta-siRNA) pathway proteins accumulate and colocalize within a sub-nuclear structure in the nucleolar periphery. Furthermore, colocalization of miRNA- and siRNA-pathway members with CB markers, and reduced wild-type localization patterns in CB mutants indicates that proper nuclear localization of these proteins requires CB integrity. We hypothesize that these nuclear domains could be important for RNA silencing and may partially explain the functional redundancies and interactions among components of the same protein family. The CB may be the place in the nucleus where Dicer-generated smRNA precursors are processed and assigned to a specific pathway, and where storage, recycling or assembly of RNA interference components takes place.
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Affiliation(s)
- Olga Pontes
- Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America.
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35
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Ono M, Yamada K, Endo A, Avolio F, Lamond AI. Analysis of human protein replacement stable cell lines established using snoMEN-PR vector. PLoS One 2013; 8:e62305. [PMID: 23638031 PMCID: PMC3636044 DOI: 10.1371/journal.pone.0062305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 03/19/2013] [Indexed: 11/20/2022] Open
Abstract
The study of the function of many human proteins is often hampered by technical limitations, such as cytotoxicity and phenotypes that result from overexpression of the protein of interest together with the endogenous version. Here we present the snoMEN (snoRNA Modulator of gene ExpressioN) vector technology for generating stable cell lines where expression of the endogenous protein can be reduced and replaced by an exogenous protein, such as a fluorescent protein (FP)-tagged version. SnoMEN are snoRNAs engineered to contain complementary sequences that can promote knock-down of targeted RNAs. We have established and characterised two such partial protein replacement human cell lines (snoMEN-PR). Quantitative mass spectrometry was used to analyse the specificity of knock-down and replacement at the protein level and also showed an increased pull-down efficiency of protein complexes containing exogenous, tagged proteins in the protein replacement cell lines, as compared with conventional co-expression strategies. The snoMEN approach facilitates the study of mammalian proteins, particularly those that have so far been difficult to investigate by exogenous expression and has wide applications in basic and applied gene-expression research.
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Affiliation(s)
- Motoharu Ono
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Kayo Yamada
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Akinori Endo
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Fabio Avolio
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Angus I. Lamond
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, United Kingdom
- * E-mail:
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36
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Prescott AR, Bales A, James J, Trinkle-Mulcahy L, Sleeman JE. Time-resolved quantitative proteomics implicates the core snRNP protein, SmB, together with the Survival of Motor Neuron protein, in neural trafficking. J Cell Sci 2013; 127:812-27. [DOI: 10.1242/jcs.137703] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The biogenesis of splicing snRNPs (small nuclear ribonucleoproteins) is a complex process, beginning and ending in the nucleus of the cell but including key stages that take place in the cytoplasm. In particular, the SMN (Survival Motor Neurons) protein complex is required for addition of the core Sm proteins to the snRNP. Insufficiency of SMN results in the inherited neurodegenerative condition, Spinal Muscular Atrophy (SMA). Details of the physical organization of the cytoplasmic stages of snRNP biogenesis are unknown. We have used time-resolved quantitative proteomics to identify proteins that associate preferentially with either newly assembled or mature splicing snRNPs. These data have allowed us to identify highly mobile SmB protein trafficking vesicles in neural cells. These vesicles are dependent on the cellular levels of SMN and SmB for their morphology and mobility. We propose that these represent a family of related vesicles, some of which play a role in snRNP biogenesis and some of which may play more diverse roles in cellular RNA metabolism.
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Luo L, Ando S, Sasabe M, Machida C, Kurihara D, Higashiyama T, Machida Y. Arabidopsis ASYMMETRIC LEAVES2 protein required for leaf morphogenesis consistently forms speckles during mitosis of tobacco BY-2 cells via signals in its specific sequence. JOURNAL OF PLANT RESEARCH 2012; 125:661-8. [PMID: 22351044 PMCID: PMC3428529 DOI: 10.1007/s10265-012-0479-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2011] [Accepted: 01/23/2012] [Indexed: 05/05/2023]
Abstract
Leaf primordia with high division and developmental competencies are generated around the periphery of stem cells at the shoot apex. Arabidopsis ASYMMETRIC-LEAVES2 (AS2) protein plays a key role in the regulation of many genes responsible for flat symmetric leaf formation. The AS2 gene, expressed in leaf primordia, encodes a plant-specific nuclear protein containing an AS2/LOB domain with cysteine repeats (C-motif). AS2 proteins are present in speckles in and around the nucleoli, and in the nucleoplasm of some leaf epidermal cells. We used the tobacco cultured cell line BY-2 expressing the AS2-fused yellow fluorescent protein to examine subnuclear localization of AS2 in dividing cells. AS2 mainly localized to speckles (designated AS2 bodies) in cells undergoing mitosis and distributed in a pairwise manner during the separation of sets of daughter chromosomes. Few interphase cells contained AS2 bodies. Deletion analyses showed that a short stretch of the AS2 amino-terminal sequence and the C-motif play negative and positive roles, respectively, in localizing AS2 to the bodies. These results suggest that AS2 bodies function to properly distribute AS2 to daughter cells during cell division in leaf primordia; and this process is controlled at least partially by signals encoded by the AS2 sequence itself.
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Affiliation(s)
- Lilan Luo
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
| | - Sayuri Ando
- Graduate school of Bioscience and Biotechnology, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501 Japan
| | - Michiko Sasabe
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
| | - Chiyoko Machida
- Graduate school of Bioscience and Biotechnology, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501 Japan
| | - Daisuke Kurihara
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
- JST ERATO Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
| | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
- JST ERATO Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
| | - Yasunori Machida
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
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Tsao W, Jeong YH, Lin S, Ling J, Price DL, Chiang PM, Wong PC. Rodent models of TDP-43: recent advances. Brain Res 2012; 1462:26-39. [PMID: 22608070 DOI: 10.1016/j.brainres.2012.04.031] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/04/2012] [Accepted: 04/17/2012] [Indexed: 12/11/2022]
Abstract
Recently, missense mutations in the gene TARDBP encoding TDP-43 have been linked to familial ALS. The discovery of genes encoding these RNA binding proteins, such as TDP-43 and FUS/TLS, raised the notion that altered RNA metabolism is a major factor underlying the pathogenesis of ALS. To begin to unravel how mutations in TDP-43 cause dysfunction and death of motor neurons, investigators have employed both gain- and loss-of-function studies in rodent model systems. Here, we will summarize major findings from the initial sets of TDP-43 transgenic and knockout rodent models, identify their limitations, and point to future directions toward clarification of disease mechanism(s) and testing of therapeutic strategies that ultimately may lead to novel therapy for this devastating disease. This article is part of a Special Issue entitled RNA-Binding Proteins.
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Affiliation(s)
- William Tsao
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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39
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Daguenet E, Baguet A, Degot S, Schmidt U, Alpy F, Wendling C, Spiegelhalter C, Kessler P, Rio MC, Le Hir H, Bertrand E, Tomasetto C. Perispeckles are major assembly sites for the exon junction core complex. Mol Biol Cell 2012; 23:1765-82. [PMID: 22419818 PMCID: PMC3338441 DOI: 10.1091/mbc.e12-01-0040] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The exon junction complex (EJC) allows the spliceosome to communicate with other cellular machinery. This study shows that assembled EJC cores are enriched in nuclear regions around speckles, called perispeckles. Speckles and perispeckles may represent specialized nuclear regions for messenger ribonucleoprotein maturation. The exon junction complex (EJC) is loaded onto mRNAs as a consequence of splicing and regulates multiple posttranscriptional events. MLN51, Magoh, Y14, and eIF4A3 form a highly stable EJC core, but where this tetrameric complex is assembled in the cell remains unclear. Here we show that EJC factors are enriched in domains that we term perispeckles and are visible as doughnuts around nuclear speckles. Fluorescence resonance energy transfer analyses and EJC assembly mutants show that perispeckles do not store free subunits, but instead are enriched for assembled cores. At the ultrastructural level, perispeckles are distinct from interchromatin granule clusters that may function as storage sites for splicing factors and intermingle with perichromatin fibrils, where nascent RNAs and active RNA Pol II are present. These results support a model in which perispeckles are major assembly sites for the tetrameric EJC core. This subnuclear territory thus represents an intermediate region important for mRNA maturation, between transcription sites and splicing factor reservoirs and assembly sites.
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Affiliation(s)
- Elisabeth Daguenet
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Unité Mixte de Recherche 7104, Centre National de la Recherche Scientifique/U964 Institut National de Santé et de Recherche Médicale/Université de Strasbourg, 67404 Illkirch, France
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40
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Clelland AK, Bales ABE, Sleeman JE. Changes in intranuclear mobility of mature snRNPs provide a mechanism for splicing defects in spinal muscular atrophy. J Cell Sci 2012; 125:2626-37. [PMID: 22393244 PMCID: PMC3403233 DOI: 10.1242/jcs.096867] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
It is becoming increasingly clear that defects in RNA metabolism can lead to disease. Spinal muscular atrophy (SMA), a leading genetic cause of infant mortality, results from insufficient amounts of survival motor neuron (SMN) protein. SMN is required for the biogenesis of small nuclear ribonucleoproteins (snRNPs): essential components of the spliceosome. Splicing abnormalities have been detected in models of SMA but it is unclear how lowered SMN affects the fidelity of pre-mRNA splicing. We have examined the dynamics of mature snRNPs in cells depleted of SMN and demonstrated that SMN depletion increases the mobility of mature snRNPs within the nucleus. To dissect the molecular mechanism by which SMN deficiency affects intranuclear snRNP mobility, we employed a panel of inhibitors of different stages of pre-mRNA processing. This in vivo modelling demonstrates that snRNP mobility is altered directly as a result of impaired snRNP maturation. Current models of nuclear dynamics predict that subnuclear structures, including the spliceosome, form by self-organization mediated by stochastic interactions between their molecular components. Thus, alteration of the intranuclear mobility of snRNPs provides a molecular mechanism for splicing defects in SMA.
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Takata H, Nishijima H, Maeshima K, Shibahara KI. The integrator complex is required for integrity of Cajal bodies. J Cell Sci 2012; 125:166-75. [PMID: 22250197 DOI: 10.1242/jcs.090837] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nucleus in eukaryotic cells is a highly organized and dynamic structure containing numerous subnuclear bodies. The morphological appearance of nuclear bodies seems to be a reflection of ongoing functions, such as DNA replication, transcription, repair, RNA processing and RNA transport. The integrator complex mediates processing of small nuclear RNA (snRNA), so it might play a role in nuclear body formation. Here, we show that the integrator complex is essential for integrity of the Cajal body. Depletion of INTS4, an integrator complex subunit, abrogated 3'-end processing of snRNA. A defect in this activity caused a significant accumulation of the Cajal body marker protein coilin in nucleoli. Some fractions of coilin still formed nucleoplasmic foci; however, they were free of other Cajal body components, such as survival of motor neuron protein (SMN), Sm proteins and snRNAs. SMN and Sm proteins formed striking cytoplasmic granules. These findings demonstrate that the integrator complex is essential for snRNA maturation and Cajal body homeostasis.
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Affiliation(s)
- Hideaki Takata
- Department of Integrated Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan.
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42
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Zou T, Yang X, Pan D, Huang J, Sahin M, Zhou J. SMN deficiency reduces cellular ability to form stress granules, sensitizing cells to stress. Cell Mol Neurobiol 2011; 31:541-50. [PMID: 21234798 PMCID: PMC11498399 DOI: 10.1007/s10571-011-9647-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 01/04/2011] [Indexed: 10/18/2022]
Abstract
Spinal Muscular Atrophy (SMA) is a neurodegenerative disease that is caused by deletion of the SMN (Survival of Motor Neuron) gene. The SMN protein is essential for cell survival and co-localized with TIA-1/R and G3BP, two characteristic markers of stress granules (SGs). To further study the SMN function in stress granules and in response to stress, we generated stable cell lines with SMN knockdown. Our data indicate that suppression of SMN drastically reduces cellular ability to form stress granules in response to stress treatment. In addition, we show that SMN deficiency sensitizes cells to sodium arsenite and H(2)O(2), two well-known stress inducers, leading to cell death at a much lower concentration of inducers in SMN knockdown cells than in control cells. Interestingly, the cell death is correlated with formation of stress granules, suggesting that involvement of SMN in formation of stress granules may play an important role in cell survival. Furthermore, rescue of SGs formation by overexpression of G3BP can reverse the defective formation of stress granules and results in partial abrogation of cell death against SMN deficiency. We deduce that modulation of stress response may be useful for potential SMN treatment.
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Affiliation(s)
- Tie Zou
- Department of Medicine, Program in Neuroscience, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605 USA
| | - Xianming Yang
- Jiangsu Key Laboratory of Neuroregeneration, Nantong University, 19th Qixiu Road, Nantong, JiangSu 226007 People’s Republic of China
| | - Danmin Pan
- Jiangsu Key Laboratory of Neuroregeneration, Nantong University, 19th Qixiu Road, Nantong, JiangSu 226007 People’s Republic of China
| | - Jia Huang
- Department of Neurology, Children’s Hospital, Boston, MA 02115 USA
| | - Mustafa Sahin
- Department of Neurology, Children’s Hospital, Boston, MA 02115 USA
| | - Jianhua Zhou
- Jiangsu Key Laboratory of Neuroregeneration, Nantong University, 19th Qixiu Road, Nantong, JiangSu 226007 People’s Republic of China
- Department of Medicine, Program in Neuroscience, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605 USA
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43
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Rajendra T, Praveen K, Matera AG. Genetic analysis of nuclear bodies: from nondeterministic chaos to deterministic order. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2011; 75:365-74. [PMID: 21467138 PMCID: PMC4062921 DOI: 10.1101/sqb.2010.75.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The eukaryotic nucleus is a congested place, and macromolecular crowding is thought to have an important role in increasing the relative concentrations of nuclear proteins, thereby accelerating the rates of biochemical reactions. Crowding is also thought to provide the environment needed for formation of nuclear bodies/subcompartments, such as the Cajal body (CB) and the histone locus body (HLB), via self-organization. In this chapter, we contrast the theories of stochastic self-organization and hierarchical self-organization in their application to nuclear body assembly, using CBs and HLBs as paradigms. Genetic ablation studies in Drosophila on components of CBs and HLBs have revealed an order to the assembly of these structures that is suggestive of a hierarchical model of self-organization. These studies also show that functions attributed to the nuclear bodies are largely unaffected in their absence, reinforcing an emerging theme in the field that the purpose of these subdomains may be to enhance the efficiency and specificity of reactions.
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Affiliation(s)
- T.K. Rajendra
- Departments of Biology and Genetics, Program in Molecular Biology & Biotechnology, Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, NC 27599
| | - Kavita Praveen
- Departments of Biology and Genetics, Program in Molecular Biology & Biotechnology, Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, NC 27599
| | - A. Gregory Matera
- Departments of Biology and Genetics, Program in Molecular Biology & Biotechnology, Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, NC 27599
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Morse R, Todd AG, Shaw DJ, McConville AL, Robinson IM, Young PJ. Mutations in the survival motor neuron (SMN) protein alter the dynamic nature of nuclear bodies. Neuromolecular Med 2011; 13:77-87. [PMID: 21082361 DOI: 10.1007/s12017-010-8139-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 10/26/2010] [Indexed: 12/01/2022]
Abstract
The childhood disorder spinal muscular atrophy (SMA) is caused by reduced expression of the survival motor neuron (SMN) protein. SMN is a multifunctional protein that has been implicated in the production, processing and transport of RNA and ribonucleoproteins (RNPs). Within the nucleus, SMN is predominantly targeted to Cajal bodies (CB), which are involved in the maturation and processing of several subclasses of RNPs. Here, we show that the SMN exon 2b-encoded domain (SMN2b) is independently sufficient to mediate CB targeting, but that the resulting bodies are less dynamic than those containing full-length SMN protein. We also show that while two SMN proteins harbouring SMA-causing point mutations (A2G and S262I) are efficiently targeted to CBs, they also display reduced nuclear movement.
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Affiliation(s)
- Robert Morse
- Clinical Neurobiology, Institute of Biomedical and Clinical Sciences, Peninsula Medical School, University of Exeter, Heavitree Rd, Exeter, EX1 2LU, UK
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45
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Novotný I, Blažíková M, Staneˇk D, Herman P, Malinsky J. In vivo kinetics of U4/U6·U5 tri-snRNP formation in Cajal bodies. Mol Biol Cell 2011; 22:513-23. [PMID: 21177826 PMCID: PMC3038649 DOI: 10.1091/mbc.e10-07-0560] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 12/08/2010] [Accepted: 12/15/2010] [Indexed: 01/09/2023] Open
Abstract
The U4/U6·U5 tri-small nuclear ribonucleoprotein particle (tri-snRNP) is an essential pre-mRNA splicing factor, which is assembled in a stepwise manner before each round of splicing. It was previously shown that the tri-snRNP is formed in Cajal bodies (CBs), but little is known about the dynamics of this process. Here we created a mathematical model of tri-snRNP assembly in CBs and used it to fit kinetics of individual snRNPs monitored by fluorescence recovery after photobleaching. A global fitting of all kinetic data determined key reaction constants of tri-snRNP assembly. Our model predicts that the rates of di-snRNP and tri-snRNP assemblies are similar and that ∼230 tri-snRNPs are assembled in one CB per minute. Our analysis further indicates that tri-snRNP assembly is approximately 10-fold faster in CBs than in the surrounding nucleoplasm, which is fully consistent with the importance of CBs for snRNP formation in rapidly developing biological systems. Finally, the model predicted binding between SART3 and a CB component. We tested this prediction by Förster resonance energy transfer and revealed an interaction between SART3 and coilin in CBs.
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MESH Headings
- Antigens, Neoplasm/genetics
- Antigens, Neoplasm/metabolism
- Cell Line, Tumor
- Cell Nucleus/genetics
- Cell Nucleus/metabolism
- Coiled Bodies/genetics
- Coiled Bodies/metabolism
- HeLa Cells
- Humans
- Kinetics
- Models, Molecular
- Nuclear Proteins/metabolism
- Protein Binding/genetics
- RNA Helicases/genetics
- RNA Helicases/metabolism
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA Splicing/genetics
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Ribonucleoprotein, U4-U6 Small Nuclear/genetics
- Ribonucleoprotein, U4-U6 Small Nuclear/metabolism
- Ribonucleoprotein, U5 Small Nuclear/genetics
- Ribonucleoprotein, U5 Small Nuclear/metabolism
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
- Spliceosomes/genetics
- Spliceosomes/metabolism
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Affiliation(s)
- Ivan Novotný
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Michaela Blažíková
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
- Faculty of Mathematics and Physics, Charles University, 121 16 Prague 2, Czech Republic
| | - David Staneˇk
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Petr Herman
- Faculty of Mathematics and Physics, Charles University, 121 16 Prague 2, Czech Republic
| | - Jan Malinsky
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
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Altered distributions of Gemini of coiled bodies and mitochondria in motor neurons of TDP-43 transgenic mice. Proc Natl Acad Sci U S A 2010; 107:16325-30. [PMID: 20736350 DOI: 10.1073/pnas.1003459107] [Citation(s) in RCA: 260] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
TAR DNA-binding protein-43 (TDP-43), a DNA/RNA-binding protein involved in RNA transcription and splicing, has been associated with the pathophysiology of neurodegenerative diseases, including ALS. However, the function of TDP-43 in motor neurons remains undefined. Here we use both gain- and loss-of-function approaches to determine roles of TDP-43 in motor neurons. Mice expressing human TDP-43 in neurons exhibited growth retardation and premature death that are characterized by abnormal intranuclear inclusions composed of TDP-43 and fused in sarcoma/translocated in liposarcoma (FUS/TLS), and massive accumulation of mitochondria in TDP-43-negative cytoplasmic inclusions in motor neurons, lack of mitochondria in motor axon terminals, and immature neuromuscular junctions. Whereas an elevated level of TDP-43 disrupts the normal nuclear distribution of survival motor neuron (SMN)-associated Gemini of coiled bodies (GEMs) in motor neurons, its absence prevents the formation of GEMs in the nuclei of these cells. Moreover, transcriptome-wide deep sequencing analysis revealed that a decrease in abundance of neurofilament transcripts contributed to the reduction of caliber of motor axons in TDP-43 mice. In concert, our findings indicate that TDP-43 participates in pathways critical for motor neuron physiology, including those that regulate the normal distributions of SMN-associated GEMs in the nucleus and mitochondria in the cytoplasm.
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47
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Abstract
The Cajal body (CB) is a nuclear organelle present in all eukaryotes that have been carefully studied. It is identified by the signature protein coilin and by CB-specific RNAs (scaRNAs). CBs contain high concentrations of splicing small nuclear ribonucleoproteins (snRNPs) and other RNA processing factors, suggesting that they are sites for assembly and/or posttranscriptional modification of the splicing machinery of the nucleus. The histone locus body (HLB) contains factors required for processing histone pre-mRNAs. As its name implies, the HLB is associated with the genes that code for histones, suggesting that it may function to concentrate processing factors at their site of action. CBs and HLBs are present throughout the interphase of the cell cycle, but disappear during mitosis. The biogenesis of CBs shows the features of a self-organizing structure.
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Affiliation(s)
- Zehra Nizami
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
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48
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Muro E, Gébrane-Younès J, Jobart-Malfait A, Louvet E, Roussel P, Hernandez-Verdun D. The traffic of proteins between nucleolar organizer regions and prenucleolar bodies governs the assembly of the nucleolus at exit of mitosis. Nucleus 2010; 1:202-11. [PMID: 21326952 PMCID: PMC3030696 DOI: 10.4161/nucl.1.2.11334] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 01/26/2010] [Accepted: 01/28/2010] [Indexed: 11/19/2022] Open
Abstract
The building of nuclear bodies after mitosis is a coordinated event crucial for nuclear organization and function. The nucleolus is assembled during early G(1) phase. Here, two periods (early G1a and early G1b) have been defined. During these periods, the nucleolar compartments (DFC, GC) corresponding to different steps of ribosome biogenesis are progressively assembled. In telophase, rDNA transcription is first activated and PNBs (reservoirs of nucleolar processing proteins) are formed. The traffic of the processing proteins between incipient nucleoli and PNBs was analyzed using photoactivation. We demonstrate that the DFC protein fibrillarin passes from one incipient nucleolus to other nucleoli but not to PNBs, and that the GC proteins, B23/NPM and Nop52, shuttle between PNBs and incipient nucleoli. This difference in traffic suggests a way of regulating assembly first of DFC and then of GC. The time of residency of GC proteins is high in incipient nucleoli compared to interphase nuclei, it decreases in LMB-treated early G1a cells impairing the assembly of GC. Because the assembly of the nucleolus and that of the Cajal body at the exit from mitosis are both sensitive to CRM1 activity, we discuss the fact that assembly of GC and/or its interaction with DFC in early G1a depends on shuttling between PNBs and NORs in a manner dependent on Cajal body assembly.
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Affiliation(s)
- Eleonora Muro
- Nuclei and Cell Cycle; Institut Jacques Monod-UMR 7592 CNRS; Université Paris Diderot; Paris, France
| | - Jeannine Gébrane-Younès
- Nuclei and Cell Cycle; Institut Jacques Monod-UMR 7592 CNRS; Université Paris Diderot; Paris, France
| | - Aude Jobart-Malfait
- Imagery Platform; Institut Jacques Monod-UMR 7592 CNRS; Université Paris Diderot; Paris, France
| | - Emilie Louvet
- Nuclei and Cell Cycle; Institut Jacques Monod-UMR 7592 CNRS; Université Paris Diderot; Paris, France
| | - Pascal Roussel
- Nuclei and Cell Cycle; Institut Jacques Monod-UMR 7592 CNRS; Université Paris Diderot; Paris, France
| | - Danièle Hernandez-Verdun
- Nuclei and Cell Cycle; Institut Jacques Monod-UMR 7592 CNRS; Université Paris Diderot; Paris, France
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49
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Goodier JL, Mandal PK, Zhang L, Kazazian HH. Discrete subcellular partitioning of human retrotransposon RNAs despite a common mechanism of genome insertion. Hum Mol Genet 2010; 19:1712-25. [PMID: 20147320 DOI: 10.1093/hmg/ddq048] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Despite the immense significance retrotransposons have had for genome evolution much about their biology is unknown, including the processes of forming their ribonucleoprotein (RNP) particles and transporting them about the cell. Suppression of retrotransposon expression, together with the presence of retrotransposon sequence within numerous mRNAs, makes tracking endogenous L1 RNP particles in cells problematic. We overcame these difficulties by assaying in living and fixed cells tagged-RNPs generated from constructs expressing retrotransposition-competent L1s. In this way, we demonstrate for the first time the subcellular colocalization of L1 RNA and proteins ORF1p and ORF2p, and show their targeting together to cytoplasmic foci. Foci are often associated with markers of cytoplasmic stress granules. Furthermore, mutation analyses reveal that ORF1p can direct L1 RNP distribution within the cell. We also assayed RNA localization of the non-autonomous retrotransposons Alu and SVA. Despite a requirement for the L1 integration machinery, each manifests unique features of subcellular RNA distribution. In nuclei Alu RNA forms small round foci partially associated with marker proteins for coiled bodies, suborganelles involved in the processing of non-coding RNAs. SVA RNA patterning is distinctive, being cytoplasmic but without prominent foci and concentrated in large nuclear aggregates that often ring nucleoli. Such variability predicts significant differences in the life cycles of these elements.
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Affiliation(s)
- John L Goodier
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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50
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James NJ, Howell GJ, Walker JH, Blair GE. The role of Cajal bodies in the expression of late phase adenovirus proteins. Virology 2010; 399:299-311. [PMID: 20137801 DOI: 10.1016/j.virol.2010.01.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 11/10/2009] [Accepted: 01/07/2010] [Indexed: 11/17/2022]
Abstract
Cajal bodies (CBs) are subnuclear structures involved in RNA metabolism. Here we show that, following infection of HeLa cells by adenovirus type 5 (Ad5), CBs fragment and form ordered structures, which we have termed "rosettes". Formation of CB rosettes was prevented by inhibition of viral DNA synthesis and preceded expression of the L4-33K protein. CB rosettes localised to the periphery of E2A-72K-containing replication centers and to the edges of ASF/SF2 and hnRNP A1 ring structures that demarcate sites of viral transcription and splicing. At later times of infection, CB rosettes were undetectable. Furthermore, knock-down of p80-coilin (the major structural protein of CBs) by RNA interference reduced the yield of infectious Ad5 and expression of the late proteins IIIa (from L1), hexon (from L3) and fiber (from L5), whereas the E2A-72K protein was unaffected. We conclude that CBs have an important role in the expression of adenovirus major late gene products.
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Affiliation(s)
- Nicola J James
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, Room 8.52d, Mount Preston Street, University of Leeds, Leeds LS2 9JT, UK
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