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Zhang M, Gu Z, Guo S, Sun Y, Ma S, Yang S, Guo J, Fang C, Shu L, Ge Y, Chen Z, Wang B. SRRM2 phase separation drives assembly of nuclear speckle subcompartments. Cell Rep 2024; 43:113827. [PMID: 38381607 DOI: 10.1016/j.celrep.2024.113827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 12/23/2023] [Accepted: 02/05/2024] [Indexed: 02/23/2024] Open
Abstract
Nuclear speckles (NSs) are nuclear biomolecular condensates that are postulated to form by macromolecular phase separation, although the detailed underlying forces driving NS formation remain elusive. SRRM2 and SON are 2 non-redundant scaffold proteins for NSs. How each individual protein governs assembly of the NS protein network and the functional relationship between SRRM2 and SON are largely unknown. Here, we uncover immiscible multiphases of SRRM2 and SON within NSs. SRRM2 and SON are functionally independent, specifically regulating alternative splicing of subsets of mRNA targets, respectively. We further show that SRRM2 forms multicomponent liquid phases in cells to drive NS subcompartmentalization, which is reliant on homotypic interaction and heterotypic non-selective protein-RNA complex coacervation-driven phase separation. SRRM2 serine/arginine-rich (RS) domains form higher-order oligomers and can be replaced by oligomerizable synthetic modules. The serine residues within the RS domains, however, play an irreplaceable role in fine-tuning the liquidity of NSs.
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Affiliation(s)
- Mengjun Zhang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Zhuang Gu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Shuanghui Guo
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Yingtian Sun
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Suibin Ma
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Shuo Yang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Jierui Guo
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Chenxi Fang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China
| | - Li Shu
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 203201, China
| | - Yifan Ge
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 203201, China
| | - Zhongwen Chen
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 203201, China
| | - Bo Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen 361102, China; Shenzhen Research Institute of Xiamen University, Shenzhen 518057, China.
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Sung HM, Schott J, Boss P, Lehmann JA, Hardt MR, Lindner D, Messens J, Bogeski I, Ohler U, Stoecklin G. Stress-induced nuclear speckle reorganization is linked to activation of immediate early gene splicing. J Cell Biol 2023; 222:e202111151. [PMID: 37956386 PMCID: PMC10641589 DOI: 10.1083/jcb.202111151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 07/13/2023] [Accepted: 09/29/2023] [Indexed: 11/15/2023] Open
Abstract
Current models posit that nuclear speckles (NSs) serve as reservoirs of splicing factors and facilitate posttranscriptional mRNA processing. Here, we discovered that ribotoxic stress induces a profound reorganization of NSs with enhanced recruitment of factors required for splice-site recognition, including the RNA-binding protein TIAR, U1 snRNP proteins and U2-associated factor 65, as well as serine 2 phosphorylated RNA polymerase II. NS reorganization relies on the stress-activated p38 mitogen-activated protein kinase (MAPK) pathway and coincides with splicing activation of both pre-existing and newly synthesized pre-mRNAs. In particular, ribotoxic stress causes targeted excision of retained introns from pre-mRNAs of immediate early genes (IEGs), whose transcription is induced during the stress response. Importantly, enhanced splicing of the IEGs ZFP36 and FOS is accompanied by relocalization of the corresponding nuclear mRNA foci to NSs. Our study reveals NSs as a dynamic compartment that is remodeled under stress conditions, whereby NSs appear to become sites of IEG transcription and efficient cotranscriptional splicing.
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Affiliation(s)
- Hsu-Min Sung
- Mannheim Institute for Innate Immunoscience (MI3) and Mannheim Cancer Center (MCC), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg, Germany
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
- Brussels Center for Redox Biology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
- Molecular Physiology, Institute of Cardiovascular Physiology, University Medical Center, Georg-August-University, Göttingen, Germany
| | - Johanna Schott
- Mannheim Institute for Innate Immunoscience (MI3) and Mannheim Cancer Center (MCC), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg, Germany
| | - Philipp Boss
- Berlin Institute for Medical Systems Biology, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
- Department of Biology, Humboldt University, Berlin, Germany
| | - Janina A. Lehmann
- Mannheim Institute for Innate Immunoscience (MI3) and Mannheim Cancer Center (MCC), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg, Germany
| | - Marius Roland Hardt
- Mannheim Institute for Innate Immunoscience (MI3) and Mannheim Cancer Center (MCC), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg, Germany
| | - Doris Lindner
- Mannheim Institute for Innate Immunoscience (MI3) and Mannheim Cancer Center (MCC), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg, Germany
| | - Joris Messens
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
- Brussels Center for Redox Biology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Ivan Bogeski
- Molecular Physiology, Institute of Cardiovascular Physiology, University Medical Center, Georg-August-University, Göttingen, Germany
| | - Uwe Ohler
- Berlin Institute for Medical Systems Biology, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
- Department of Biology, Humboldt University, Berlin, Germany
| | - Georg Stoecklin
- Mannheim Institute for Innate Immunoscience (MI3) and Mannheim Cancer Center (MCC), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg, Germany
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Podszywalow-Bartnicka P, Neugebauer KM. Splicing under stress: A matter of time and place. J Cell Biol 2023; 222:e202311014. [PMID: 37988026 PMCID: PMC10660129 DOI: 10.1083/jcb.202311014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023] Open
Abstract
Excision of introns during splicing regulates gene expression. In this issue, work by Sung et al. (https://doi.org/10.1083/jcb.202111151) demonstrates that the timing of intron removal in response to stress is coordinated in nuclear speckles, adding a component of spatial regulation to co-/post-transcriptional splicing.
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Affiliation(s)
| | - Karla M. Neugebauer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven CT, USA
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Enders L, Siklos M, Borggräfe J, Gaussmann S, Koren A, Malik M, Tomek T, Schuster M, Reiniš J, Hahn E, Rukavina A, Reicher A, Casteels T, Bock C, Winter GE, Hannich JT, Sattler M, Kubicek S. Pharmacological perturbation of the phase-separating protein SMNDC1. Nat Commun 2023; 14:4504. [PMID: 37587144 PMCID: PMC10432564 DOI: 10.1038/s41467-023-40124-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 07/13/2023] [Indexed: 08/18/2023] Open
Abstract
SMNDC1 is a Tudor domain protein that recognizes di-methylated arginines and controls gene expression as an essential splicing factor. Here, we study the specific contributions of the SMNDC1 Tudor domain to protein-protein interactions, subcellular localization, and molecular function. To perturb the protein function in cells, we develop small molecule inhibitors targeting the dimethylarginine binding pocket of the SMNDC1 Tudor domain. We find that SMNDC1 localizes to phase-separated membraneless organelles that partially overlap with nuclear speckles. This condensation behavior is driven by the unstructured C-terminal region of SMNDC1, depends on RNA interaction and can be recapitulated in vitro. Inhibitors of the protein's Tudor domain drastically alter protein-protein interactions and subcellular localization, causing splicing changes for SMNDC1-dependent genes. These compounds will enable further pharmacological studies on the role of SMNDC1 in the regulation of nuclear condensates, gene regulation and cell identity.
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Affiliation(s)
- Lennart Enders
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Marton Siklos
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Jan Borggräfe
- Helmholtz Munich, Molecular Targets and Therapeutics Center, Institute of Structural Biology, Neuherberg, 85764, München, Germany
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Bavarian NMR Center, Garching, 85748, München, Germany
| | - Stefan Gaussmann
- Helmholtz Munich, Molecular Targets and Therapeutics Center, Institute of Structural Biology, Neuherberg, 85764, München, Germany
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Bavarian NMR Center, Garching, 85748, München, Germany
| | - Anna Koren
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Monika Malik
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Tatjana Tomek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Michael Schuster
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Jiří Reiniš
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Elisa Hahn
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Andrea Rukavina
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Andreas Reicher
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Tamara Casteels
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
- Sloan Kettering Institute, 1275 York Avenue, New York, NY, 10065, USA
| | - Christoph Bock
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
- Medical University of Vienna, Institute of Artificial Intelligence, Center for Medical Data Science, Währinger Straße 25a, 1090, Vienna, Austria
| | - Georg E Winter
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - J Thomas Hannich
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - Michael Sattler
- Helmholtz Munich, Molecular Targets and Therapeutics Center, Institute of Structural Biology, Neuherberg, 85764, München, Germany
- Technical University of Munich, TUM School of Natural Sciences, Department of Bioscience, Bavarian NMR Center, Garching, 85748, München, Germany
| | - Stefan Kubicek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria.
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Peng KC, Siao W, Hsieh HL. FAR-RED INSENSITIVE 219 and phytochrome B corepress shade avoidance via modulating nuclear speckle formation. Plant Physiol 2023; 192:1449-1465. [PMID: 36869668 PMCID: PMC10231371 DOI: 10.1093/plphys/kiad103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/22/2022] [Accepted: 11/22/2022] [Indexed: 06/01/2023]
Abstract
Plants can sense the shade from neighboring plants by detecting a reduction of the red:far-red light (R:FR) ratio. Phytochrome B (phyB) is the primary photoreceptor that perceives shade light and regulates jasmonic acid (JA) signaling. However, the molecular mechanisms underlying phyB and JA signaling integration in shade responses remain largely unknown. Here, we show the interaction of phyB and FAR-RED INSENSITIVE 219 (FIN219)/JASMONATE RESISTANT1 (JAR1) in a functional demand manner in Arabidopsis (Arabidopsis thaliana) seedling development. Genetic evidence and interaction studies indicated that phyB and FIN219 synergistically and negatively regulate shade-induced hypocotyl elongation. Moreover, phyB interacted with various isoforms of FIN219 under high and low R:FR light. Methyl jasmonate (MeJA) treatment, FIN219 mutation, and PHYBOE digalactosyldiacylglycerol synthase1-1 (dgd1-1) plants, which show increased levels of JA, altered the patterns of phyB-associated nuclear speckles under the same conditions. Surprisingly, PHYBOE dgd1-1 showed a shorter hypocotyl phenotype than its parental mutants under shade conditions. Microarray assays using PHYBOE and PHYBOE fin219-2 indicated that PHYB overexpression substantially affects defense response-related genes under shade light and coregulates expression of auxin-responsive genes with FIN219. Thus, our findings reveal that phyB substantially crosstalks with JA signaling through FIN219 to modulate seedling development under shade light.
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Affiliation(s)
- Kai-Chun Peng
- Institute of Plant Biology, College of Life Science, National Taiwan University, Taipei 106, Taiwan
| | - Wei Siao
- Institute of Plant Biology, College of Life Science, National Taiwan University, Taipei 106, Taiwan
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium
- Center for Plant Systems Biology, VIB, 9052 Ghent, Belgium
| | - Hsu-Liang Hsieh
- Institute of Plant Biology, College of Life Science, National Taiwan University, Taipei 106, Taiwan
- Department of Life Science, College of Life Science, National Taiwan University, Taipei 106, Taiwan
- Master Program in Global Agriculture Technology and Genomic Science, National Taiwan University, Taipei 106, Taiwan
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Gao S, Esparza M, Dehghan I, Aksenova V, Zhang K, Batten K, Ferretti MB, Begg BE, Cagatay T, Shay JW, García-Sastre A, Goldsmith EJ, Chen ZJ, Dasso M, Lynch KW, Cobb MH, Fontoura BMA. Nuclear speckle integrity and function require TAO2 kinase. Proc Natl Acad Sci U S A 2022; 119:e2206046119. [PMID: 35704758 PMCID: PMC9231605 DOI: 10.1073/pnas.2206046119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/16/2022] [Indexed: 11/18/2022] Open
Abstract
Nuclear speckles are non-membrane-bound organelles known as storage sites for messenger RNA (mRNA) processing and splicing factors. More recently, nuclear speckles have also been implicated in splicing and export of a subset of mRNAs, including the influenza virus M mRNA that encodes proteins required for viral entry, trafficking, and budding. However, little is known about how nuclear speckles are assembled or regulated. Here, we uncovered a role for the cellular protein kinase TAO2 as a constituent of nuclear speckles and as a factor required for the integrity of these nuclear bodies and for their functions in pre-mRNA splicing and trafficking. We found that a nuclear pool of TAO2 is localized at nuclear speckles and interacts with nuclear speckle factors involved in RNA splicing and nuclear export, including SRSF1 and Aly/Ref. Depletion of TAO2 or inhibition of its kinase activity disrupts nuclear speckle structure, decreasing the levels of several proteins involved in nuclear speckle assembly and splicing, including SC35 and SON. Consequently, splicing and nuclear export of influenza virus M mRNA were severely compromised and caused a disruption in the virus life cycle. In fact, low levels of TAO2 led to a decrease in viral protein levels and inhibited viral replication. Additionally, depletion or inhibition of TAO2 resulted in abnormal expression of a subset of mRNAs with key roles in viral replication and immunity. Together, these findings uncovered a function of TAO2 in nuclear speckle formation and function and revealed host requirements and vulnerabilities for influenza infection.
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Affiliation(s)
- Shengyan Gao
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Matthew Esparza
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Ishmael Dehghan
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Vasilisa Aksenova
- Division of Molecular and Cellular Biology, National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892
| | - Ke Zhang
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Kimberly Batten
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Max B. Ferretti
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104
| | - Bridget E. Begg
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104
| | - Tolga Cagatay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Jerry W. Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029
- Division of Infectious Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029
- Department of Pathology, Molecular and Cell-Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Elizabeth J. Goldsmith
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Zhijian J. Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Mary Dasso
- Division of Molecular and Cellular Biology, National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892
| | - Kristen W. Lynch
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104
| | - Melanie H. Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Beatriz M. A. Fontoura
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
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Lee ES, Smith HW, Wolf EJ, Guvenek A, Wang YE, Emili A, Tian B, Palazzo AF. ZFC3H1 and U1-70K promote the nuclear retention of mRNAs with 5' splice site motifs within nuclear speckles. RNA 2022; 28:878-894. [PMID: 35351812 PMCID: PMC9074902 DOI: 10.1261/rna.079104.122] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 03/12/2022] [Indexed: 05/22/2023]
Abstract
Quality control of mRNA represents an important regulatory mechanism for gene expression in eukaryotes. One component of this quality control is the nuclear retention and decay of misprocessed RNAs. Previously, we demonstrated that mature mRNAs containing a 5' splice site (5'SS) motif, which is typically found in misprocessed RNAs such as intronic polyadenylated (IPA) transcripts, are nuclear retained and degraded. Using high-throughput sequencing of cellular fractions, we now demonstrate that IPA transcripts require the zinc finger protein ZFC3H1 for their nuclear retention and degradation. Using reporter mRNAs, we demonstrate that ZFC3H1 promotes the nuclear retention of mRNAs with intact 5'SS motifs by sequestering them into nuclear speckles. Furthermore, we find that U1-70K, a component of the spliceosomal U1 snRNP, is also required for the nuclear retention of these reporter mRNAs and likely functions in the same pathway as ZFC3H1. Finally, we show that the disassembly of nuclear speckles impairs the nuclear retention of reporter mRNAs with 5'SS motifs. Our results highlight a splicing independent role of U1 snRNP and indicate that it works in conjunction with ZFC3H1 in preventing the nuclear export of misprocessed mRNAs by sequestering them into nuclear speckles.
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Affiliation(s)
- Eliza S Lee
- Department of Biochemistry, University of Toronto, Ontario M5S 1A8, Canada
| | - Harrison W Smith
- Department of Biochemistry, University of Toronto, Ontario M5S 1A8, Canada
| | - Eric J Wolf
- Department of Molecular Genetics, University of Toronto, Ontario M5S 1A8, Canada
| | - Aysegul Guvenek
- Rutgers New Jersey Medical School, Newark, New Jersey 07103, USA
| | - Yifan E Wang
- Department of Biochemistry, University of Toronto, Ontario M5S 1A8, Canada
| | - Andrew Emili
- Department of Molecular Genetics, University of Toronto, Ontario M5S 1A8, Canada
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Bin Tian
- Rutgers New Jersey Medical School, Newark, New Jersey 07103, USA
- Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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