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Schwenzer H, Jühling F, Chu A, Pallett LJ, Baumert TF, Maini M, Fassati A. Oxidative Stress Triggers Selective tRNA Retrograde Transport in Human Cells during the Integrated Stress Response. Cell Rep 2020; 26:3416-3428.e5. [PMID: 30893612 PMCID: PMC6426654 DOI: 10.1016/j.celrep.2019.02.077] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 02/04/2019] [Accepted: 02/20/2019] [Indexed: 01/05/2023] Open
Abstract
In eukaryotes, tRNAs are transcribed in the nucleus and exported to the cytosol, where they deliver amino acids to ribosomes for protein translation. This nuclear-cytoplasmic movement was believed to be unidirectional. However, active shuttling of tRNAs, named tRNA retrograde transport, between the cytosol and nucleus has been discovered. This pathway is conserved in eukaryotes, suggesting a fundamental function; however, little is known about its role in human cells. Here we report that, in human cells, oxidative stress triggers tRNA retrograde transport, which is rapid, reversible, and selective for certain tRNA species, mostly with shorter 3′ ends. Retrograde transport of tRNASeC, which promotes translation of selenoproteins required to maintain homeostatic redox levels in cells, is highly efficient. tRNA retrograde transport is regulated by the integrated stress response pathway via the PERK-REDD1-mTOR axis. Thus, we propose that tRNA retrograde transport is part of the cellular response to oxidative stress. Oxidative stress triggers nuclear import of cytoplasmic tRNAs Import is selective for certain tRNAs Import requires activation of the unfolded protein response and inhibition of mTOR via REDD1 tRNA nuclear import is a component of the integrated stress response
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Affiliation(s)
- Hagen Schwenzer
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Frank Jühling
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 2 Université de Strasbourg, 67000 Strasbourg, France
| | - Alexander Chu
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Laura J Pallett
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Thomas F Baumert
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 2 Université de Strasbourg, 67000 Strasbourg, France; Nouvel Hôpital Civil, Institut Hospitalo-Universitaire, 67000 Strasbourg, France
| | - Mala Maini
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Ariberto Fassati
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK.
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Deryusheva S, Gall JG. scaRNAs and snoRNAs: Are they limited to specific classes of substrate RNAs? RNA (NEW YORK, N.Y.) 2019; 25:17-22. [PMID: 30301832 PMCID: PMC6298559 DOI: 10.1261/rna.068593.118] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 10/07/2018] [Indexed: 05/28/2023]
Abstract
Posttranscriptional modifications of rRNA occur in the nucleolus where rRNA modification guide RNAs, or snoRNAs, concentrate. On the other hand, scaRNAs, the modification guide RNAs for spliceosomal snRNAs, concentrate in the Cajal body (CB). It is generally assumed, therefore, that snRNAs must accumulate in CBs to be modified by scaRNAs. Here we demonstrate that the evidence for the latter postulate is not consistent. In the nucleus, scaRNA localization is not limited to CBs. Furthermore, canonical scaRNAs can modify rRNAs. We suggest that the conventional view that scaRNAs function only in the CB needs revision.
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MESH Headings
- Animals
- Base Sequence
- Coiled Bodies/metabolism
- HeLa Cells
- Humans
- Nucleic Acid Conformation
- RNA Processing, Post-Transcriptional
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Small Nuclear/chemistry
- RNA, Small Nuclear/genetics
- RNA, Small Nuclear/metabolism
- RNA, Small Nucleolar/chemistry
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/metabolism
- Spliceosomes/genetics
- Spliceosomes/metabolism
- Xenopus/genetics
- Xenopus/metabolism
- RNA, Guide, CRISPR-Cas Systems
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Affiliation(s)
- Svetlana Deryusheva
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Joseph G Gall
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
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Heyn P, Salmonowicz H, Rodenfels J, Neugebauer KM. Activation of transcription enforces the formation of distinct nuclear bodies in zebrafish embryos. RNA Biol 2016; 14:752-760. [PMID: 27858508 DOI: 10.1080/15476286.2016.1255397] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Nuclear bodies are cellular compartments that lack lipid bilayers and harbor specific RNAs and proteins. Recent proposals that nuclear bodies form through liquid-liquid phase separation leave the question of how different nuclear bodies maintain their distinct identities unanswered. Here we investigate Cajal bodies (CBs), histone locus bodies (HLBs) and nucleoli - involved in assembly of the splicing machinery, histone mRNA 3' end processing, and rRNA processing, respectively - in the embryos of the zebrafish, Danio rerio. We take advantage of the transcriptional silence of the 1-cell embryo and follow nuclear body appearance as zygotic transcription becomes activated. CBs are present from fertilization onwards, while HLB and nucleolar components formed foci several hours later when histone genes and rDNA became active. HLB formation was blocked by transcription inhibition, suggesting nascent histone transcripts recruit HLB components like U7 snRNP. Surprisingly, we found that U7 base-pairing with nascent histone transcripts was not required for localization to HLBs. Rather, the type of Sm ring assembled on U7 determined its targeting to HLBs or CBs; the spliceosomal Sm ring targeted snRNAs to CBs while the specialized U7 Sm-ring localized to HLBs, demonstrating the contribution of protein constituents to the distinction among nuclear bodies. Thus, nucleolar, HLB, and CB components can mix in early embryogenesis when transcription is naturally or artificially silenced. These data support a model in which transcription of specific gene loci nucleates nuclear body components with high specificity and fidelity to perform distinct regulatory functions.
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Affiliation(s)
- Patricia Heyn
- a Max Planck Institute of Molecular Cell Biology and Genetics , Dresden , Germany
| | - Hanna Salmonowicz
- a Max Planck Institute of Molecular Cell Biology and Genetics , Dresden , Germany
| | - Jonathan Rodenfels
- b Department of Molecular Biophysics & Biochemistry , Yale University , New Haven , CT , USA
| | - Karla M Neugebauer
- b Department of Molecular Biophysics & Biochemistry , Yale University , New Haven , CT , USA
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Abstract
Spliceosomal snRNPs are complex particles that proceed through a fascinating maturation pathway. Several steps of this pathway are closely linked to nuclear non-membrane structures called Cajal bodies. In this review, I summarize the last 20 y of research in this field. I primarily focus on snRNP biogenesis, specifically on the steps that involve Cajal bodies. I also evaluate the contribution of the Cajal body in snRNP quality control and discuss the role of snRNPs in Cajal body formation.
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Affiliation(s)
- David Staněk
- a Institute of Molecular Genetics, Czech Academy of Sciences , Prague , Czech Republic
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Kim R, Paschedag J, Novikova N, Bellini M. The recruitment of the U5 snRNP to nascent transcripts requires internal loop 1 of U5 snRNA. Chromosome Res 2012. [PMID: 23180092 DOI: 10.1007/s10577-012-9326-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In this study, we take advantage of the high spatial resolution offered by the nucleus and lampbrush chromosomes of the amphibian oocyte to investigate the mechanisms that regulate the intranuclear trafficking of the U5 snRNP and its recruitment to nascent transcripts. We monitor the fate of newly assembled fluorescent U5 snRNP in Xenopus oocytes depleted of U4 and/or U6 snRNAs and demonstrate that the U4/U6.U5 tri-snRNP is not required for the association of U5 snRNP with Cajal bodies, splicing speckles, and nascent transcripts. In addition, using a mutational analysis, we show that a non-functional U5 snRNP can associate with nascent transcripts, and we further characterize internal loop structure 1 of U5 snRNA as a critical element for licensing U5 snRNP to target both nascent transcripts and splicing speckles. Collectively, our data support the model where the recruitment of snRNPs onto pre-mRNAs is independent of spliceosome assembly and suggest that U5 snRNP may promote the association of the U4/U6.U5 tri-snRNP with nascent transcripts.
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Affiliation(s)
- Rebecca Kim
- Department of Cell and Developmental Biology, University of Illinois at Champaign-Urbana, 601 S Goodwin Avenue, Room B107 CLSL, Urbana, IL 61801, USA
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Strzelecka M, Oates AC, Neugebauer KM. Dynamic control of Cajal body number during zebrafish embryogenesis. Nucleus 2012; 1:96-108. [PMID: 21327108 DOI: 10.4161/nucl.1.1.10680] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 11/17/2009] [Accepted: 11/18/2009] [Indexed: 02/06/2023] Open
Abstract
The Cajal body (CB) is an evolutionarily conserved nuclear subcompartment, enriched in components of the RNA processing machinery. The composition and dynamics of CBs in cells of living organisms is not well understood. Here we establish the zebrafish embryo as a model system to investigate the properties of CBs during rapid growth and cell division, taking advantage of the ease of live-cell imaging. We show that zebrafish embryo CBs contain coilin and multiple components of the pre-mRNA splicing machinery. Histone mRNA 3' end processing factors, present in CBs in some systems, were instead concentrated in a distinct nuclear body. CBs were present in embryos before and after activation of zygotic gene expression, indicating a maternal contribution of CB components. During the first 24 hours of development, embryonic cells displayed up to 30 CBs per nucleus; these dispersed prior to mitosis and reassembled within minutes upon daughter cell nucleus formation. Following zygotic genome activation, snRNP biogenesis was required for CB assembly and maintenance, suggesting a self-assembly process that determines CB numbers in embryos. Differentiation into muscle, neurons and epidermis was associated with the achievement of a steady state number of 2 CBs per nucleus. We propose that CB number is regulated during development to respond to the demands of gene expression in a rapidly growing embryo.
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Sasaki-Haraguchi N, Shimada MK, Taniguchi I, Ohno M, Mayeda A. Mechanistic insights into human pre-mRNA splicing of human ultra-short introns: potential unusual mechanism identifies G-rich introns. Biochem Biophys Res Commun 2012; 423:289-94. [PMID: 22640740 DOI: 10.1016/j.bbrc.2012.05.112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/18/2012] [Indexed: 10/28/2022]
Abstract
It is unknown how very short introns (<65 nt; termed 'ultra-short' introns) could be spliced in a massive spliceosome (>2.7 MDa) without steric hindrance. By screening an annotated human transcriptome database (H-InvDB), we identified three model ultra-short introns: the 56-nt intron in the HNRNPH1 (hnRNP H1) gene, the 49-nt intron in the NDOR1 (NADPH dependent diflavin oxidoreductase 1) gene, and the 43-nt intron in the ESRP2 (epithelial splicing regulatory protein 2) gene. We verified that these endogenous ultra-short introns are spliced, and also recapitulated this in cultured cells transfected with the corresponding mini-genes. The splicing of these ultra-short introns was repressed by a splicing inhibitor, spliceostatin A, suggesting that SF3b (a U2 snRNP component) is involved in their splicing processes. The 56-nt intron containing a pyrimidine-rich tract was spliced out in a lariat form, and this splicing was inhibited by the disruption of U1, U2, or U4 snRNA. In contrast, the 49- and 43-nt introns were purine-rich overall without any pyrimidine-rich tract, and these lariat RNAs were not detectable. Remarkably, shared G-rich intronic sequences in the 49- and 43-nt introns were required for their splicing, suggesting that these ultra-short introns may recruit a novel auxiliary splicing mechanism linked to G-rich intronic splicing enhancers.
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Affiliation(s)
- Noriko Sasaki-Haraguchi
- Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan
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Patel SB, Novikova N, Bellini M. Splicing-independent recruitment of spliceosomal small nuclear RNPs to nascent RNA polymerase II transcripts. ACTA ACUST UNITED AC 2007; 178:937-49. [PMID: 17846169 PMCID: PMC2064619 DOI: 10.1083/jcb.200706134] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In amphibian oocytes, most lateral loops of the lampbrush chromosomes correspond to active transcriptional sites for RNA polymerase II. We show that newly assembled small nuclear ribonucleoprotein (RNP [snRNP]) particles, which are formed upon cytoplasmic injection of fluorescently labeled spliceosomal small nuclear RNAs (snRNAs), target the nascent transcripts of the chromosomal loops. With this new targeting assay, we demonstrate that nonfunctional forms of U1 and U2 snRNAs still associate with the active transcriptional units. In particular, we find that their association with nascent RNP fibrils is independent of their base pairing with pre–messenger RNAs. Additionally, stem loop I of the U1 snRNA is identified as a discrete domain that is both necessary and sufficient for association with nascent transcripts. Finally, in oocytes deficient in splicing, the recruitment of U1, U4, and U5 snRNPs to transcriptional units is not affected. Collectively, these data indicate that the recruitment of snRNPs to nascent transcripts and the assembly of the spliceosome are uncoupled events.
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MESH Headings
- Animals
- Female
- Nucleic Acid Conformation
- RNA Polymerase II/genetics
- RNA Polymerase II/metabolism
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA Splicing
- RNA, Small Nuclear/genetics
- RNA, Small Nuclear/metabolism
- Ribonucleoprotein, U1 Small Nuclear/genetics
- Ribonucleoprotein, U1 Small Nuclear/metabolism
- Ribonucleoprotein, U2 Small Nuclear/genetics
- Ribonucleoprotein, U2 Small Nuclear/metabolism
- Ribonucleoprotein, U4-U6 Small Nuclear/genetics
- Ribonucleoprotein, U4-U6 Small Nuclear/metabolism
- Ribonucleoprotein, U5 Small Nuclear/genetics
- Ribonucleoprotein, U5 Small Nuclear/metabolism
- Ribonucleoprotein, U7 Small Nuclear/genetics
- Ribonucleoprotein, U7 Small Nuclear/metabolism
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
- Spliceosomes/genetics
- Spliceosomes/physiology
- Xenopus
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Affiliation(s)
- Snehal Bhikhu Patel
- Department of Biochemistry, College of Medicine, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Damianov A, Kann M, Lane WS, Bindereif A. Human RBM28 protein is a specific nucleolar component of the spliceosomal snRNPs. Biol Chem 2006; 387:1455-60. [PMID: 17081119 DOI: 10.1515/bc.2006.182] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The biogenesis of spliceosomal small nuclear RNAs (snRNAs) involves organized translocations between the cytoplasm and certain nuclear domains, such as Cajal bodies and nucleoli. Here we identify human RBM28 protein as a novel snRNP component, based on affinity selection of U6 small nuclear ribonucleoprotein (snRNP). As shown by immunofluorescence, RBM28 is a nucleolar protein. Anti-RBM28 immunoprecipitation from HeLa cell lysates revealed that this protein specifically associates with U1, U2, U4, U5, and U6 snRNAs. Our data provide the first evidence that RBM28 is a common nucleolar component of the spliceosomal ribonucleoprotein complexes, possibly coordinating their transition through the nucleolus.
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Affiliation(s)
- Andrey Damianov
- Institut für Biochemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany
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10
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Klingauf M, Stanĕk D, Neugebauer KM. Enhancement of U4/U6 small nuclear ribonucleoprotein particle association in Cajal bodies predicted by mathematical modeling. Mol Biol Cell 2006; 17:4972-81. [PMID: 16987958 PMCID: PMC1679666 DOI: 10.1091/mbc.e06-06-0513] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Spliceosomal small nuclear ribonucleoprotein particles (snRNPs) undergo specific assembly steps in Cajal bodies (CBs), nonmembrane-bound compartments within cell nuclei. An example is the U4/U6 di-snRNP, assembled from U4 and U6 monomers. These snRNPs can also assemble in the nucleoplasm when cells lack CBs. Here, we address the hypothesis that snRNP concentration in CBs facilitates assembly, by comparing the predicted rates of U4 and U6 snRNP association in nuclei with and without CBs. This was accomplished by a random walk-and-capture simulation applied to a three-dimensional model of the HeLa cell nucleus, derived from measurements of living cells. Results of the simulations indicated that snRNP capture is optimal when nuclei contain three to four CBs. Interestingly, this is the observed number of CBs in most cells. Microinjection experiments showed that U4 snRNA targeting to CBs was U6 snRNP independent and that snRNA concentration in CBs is approximately 20-fold higher than in nucleoplasm. Finally, combination of the simulation with calculated association rates predicted that the presence of CBs enhances U4 and U6 snRNP association by up to 11-fold, largely owing to this concentration difference. This provides a chemical foundation for the proposal that these and other cellular compartments promote molecular interactions, by increasing the local concentration of individual components.
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Affiliation(s)
- Mirko Klingauf
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - David Stanĕk
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Karla M. Neugebauer
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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Stanĕk D, Neugebauer KM. Detection of snRNP assembly intermediates in Cajal bodies by fluorescence resonance energy transfer. ACTA ACUST UNITED AC 2004; 166:1015-25. [PMID: 15452143 PMCID: PMC2172029 DOI: 10.1083/jcb.200405160] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Spliceosomal small nuclear ribonucleoprotein particles (snRNPs) are required for pre-mRNA splicing throughout the nucleoplasm, yet snRNPs also concentrate in Cajal bodies (CBs). To address a proposed role of CBs in snRNP assembly, we have used fluorescence resonance energy transfer (FRET) microscopy to investigate the subnuclear distribution of specific snRNP intermediates. Two distinct complexes containing the protein SART3 (p110), required for U4/U6 snRNP assembly, were localized: SART3•U6 snRNP and SART3•U4/U6 snRNP. These complexes segregated to different nuclear compartments, with SART3•U6 snRNPs exclusively in the nucleoplasm and SART3•U4/U6 snRNPs preferentially in CBs. Mutant cells lacking the CB-specific protein coilin and consequently lacking CBs exhibited increased nucleoplasmic levels of SART3•U4/U6 snRNP complexes. Reconstitution of CBs in these cells by expression of exogenous coilin restored accumulation of SART3•U4/U6 snRNP in CBs. Thus, while some U4/U6 snRNP assembly can occur in the nucleoplasm, these data provide evidence that SART3•U6 snRNPs form in the nucleoplasm and translocate to CBs where U4/U6 snRNP assembly occurs.
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Affiliation(s)
- David Stanĕk
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
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