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Gutierrez PA, Baughman K, Sun Y, Tong L. A real-time fluorescence assay for CPSF73, the nuclease for pre-mRNA 3'-end processing. RNA 2021; 27:1148-1154. [PMID: 34230059 PMCID: PMC8457007 DOI: 10.1261/rna.078764.121] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [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: 03/25/2021] [Accepted: 06/17/2021] [Indexed: 05/09/2023]
Abstract
CPSF73 is the endonuclease that catalyzes the cleavage reaction for 3'-end processing of mRNA precursors (pre-mRNAs) in two distinct machineries, a canonical machinery for the majority of pre-mRNAs and a U7 snRNP (U7 machinery) for replication-dependent histone pre-mRNAs in animal cells. CPSF73 also possesses 5'-3' exonuclease activity in the U7 machinery, degrading the downstream cleavage product after the endonucleolytic cleavage. Recent studies show that CPSF73 is a potential target for developing anticancer, antimalarial, and antiprotozoal drugs, spurring interest in identifying new small-molecule inhibitors against this enzyme. CPSF73 nuclease activity has so far been demonstrated using a gel-based end-point assay, using radiolabeled or fluorescently labeled RNA substrates. By taking advantage of unique properties of the U7 machinery, we have developed a novel, real-time fluorescence assay for the nuclease activity of CPSF73. This assay is facile and high-throughput, and should also be helpful for the discovery of new CPSF73 inhibitors.
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Affiliation(s)
- Pedro A Gutierrez
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Kirk Baughman
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Yadong Sun
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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2
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Uggenti C, Lepelley A, Depp M, Badrock AP, Rodero MP, El-Daher MT, Rice GI, Dhir S, Wheeler AP, Dhir A, Albawardi W, Frémond ML, Seabra L, Doig J, Blair N, Martin-Niclos MJ, Della Mina E, Rubio-Roldán A, García-Pérez JL, Sproul D, Rehwinkel J, Hertzog J, Boland-Auge A, Olaso R, Deleuze JF, Baruteau J, Brochard K, Buckley J, Cavallera V, Cereda C, De Waele LMH, Dobbie A, Doummar D, Elmslie F, Koch-Hogrebe M, Kumar R, Lamb K, Livingston JH, Majumdar A, Lorenço CM, Orcesi S, Peudenier S, Rostasy K, Salmon CA, Scott C, Tonduti D, Touati G, Valente M, van der Linden H, Van Esch H, Vermelle M, Webb K, Jackson AP, Reijns MAM, Gilbert N, Crow YJ. cGAS-mediated induction of type I interferon due to inborn errors of histone pre-mRNA processing. Nat Genet 2020; 52:1364-1372. [PMID: 33230297 DOI: 10.1038/s41588-020-00737-3] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [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: 07/03/2020] [Accepted: 10/09/2020] [Indexed: 12/25/2022]
Abstract
Inappropriate stimulation or defective negative regulation of the type I interferon response can lead to autoinflammation. In genetically uncharacterized cases of the type I interferonopathy Aicardi-Goutières syndrome, we identified biallelic mutations in LSM11 and RNU7-1, which encode components of the replication-dependent histone pre-mRNA-processing complex. Mutations were associated with the misprocessing of canonical histone transcripts and a disturbance of linker histone stoichiometry. Additionally, we observed an altered distribution of nuclear cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) and enhanced interferon signaling mediated by the cGAS-stimulator of interferon genes (STING) pathway in patient-derived fibroblasts. Finally, we established that chromatin without linker histone stimulates cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) production in vitro more efficiently. We conclude that nuclear histones, as key constituents of chromatin, are essential in suppressing the immunogenicity of self-DNA.
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Affiliation(s)
- Carolina Uggenti
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Alice Lepelley
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France
| | - Marine Depp
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Andrew P Badrock
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Mathieu P Rodero
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France
| | - Marie-Thérèse El-Daher
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Gillian I Rice
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Somdutta Dhir
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Ann P Wheeler
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Ashish Dhir
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Waad Albawardi
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Marie-Louise Frémond
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France
| | - Luis Seabra
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France
| | - Jennifer Doig
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Natalie Blair
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Maria José Martin-Niclos
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France
| | - Erika Della Mina
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France
| | - Alejandro Rubio-Roldán
- Centre for Genomics and Oncological Research (GENyO), Pfizer-University of Granada-Andalusian Regional Government, Parque Tecnico de la Ciencia de Salud, Granada, Spain
| | - Jose L García-Pérez
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
- Centre for Genomics and Oncological Research (GENyO), Pfizer-University of Granada-Andalusian Regional Government, Parque Tecnico de la Ciencia de Salud, Granada, Spain
| | - Duncan Sproul
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
- Cancer Research UK Edinburgh Centre, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Jan Rehwinkel
- Medical Research Council Human Immunology Unit, Medical Research Council Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Jonny Hertzog
- Medical Research Council Human Immunology Unit, Medical Research Council Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Anne Boland-Auge
- Université Paris-Saclay, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Centre National de Recherche en Génomique Humaine, Évry, France
| | - Robert Olaso
- Université Paris-Saclay, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Centre National de Recherche en Génomique Humaine, Évry, France
| | - Jean-François Deleuze
- Université Paris-Saclay, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Centre National de Recherche en Génomique Humaine, Évry, France
| | - Julien Baruteau
- University College London Great Ormond Street Institute of Child Health, London, UK
| | - Karine Brochard
- Service de Médecine Interne Néphrologie Pédiatrique, Hôpital des Enfants, Toulouse, France
| | - Jonathan Buckley
- Department of Paediatric Nephrology, University of Cape Town, Red Cross War Memorial Children's Hospital, Cape Town, South Africa
| | - Vanessa Cavallera
- Child Neurology and Psychiatry Unit, Istituto di Ricovero e Cura a Carattere Scientifico, Mondino Foundation, Pavia, Italy
| | - Cristina Cereda
- Genomic and Post-Genomic Center, Istituto di Ricovero e Cura a Carattere Scientifico, Mondino Foundation, Pavia, Italy
| | | | - Angus Dobbie
- Yorkshire Clinical Genetics Service, Chapel Allerton Hospital, Leeds, UK
| | - Diane Doummar
- Sorbonne Université, Assistance Publique-Hôpitaux de Paris, Département de Neuropédiatrie, Centre de Référence de Neurogénétique et Mouvements Anormaux de l'Enfant, Hôpital Armand Trousseau, Paris, France
| | - Frances Elmslie
- South West Thames Regional Genetics Service, St George's, University of London, London, UK
| | - Margarete Koch-Hogrebe
- Department of Paediatric Neurology, Children's Hospital Datteln, Witten/Herdecke University, Datteln, Germany
| | - Ram Kumar
- Department of Paediatric Neurology, Alder Hey Children's National Health Service Foundation Trust, Liverpool, UK
| | - Kate Lamb
- Department of Paediatrics, Gloucestershire Royal Hospital, Gloucester, UK
| | - John H Livingston
- Department of Paediatric Neurology, Leeds Teaching Hospitals National Health Service Trust, Leeds, UK
| | - Anirban Majumdar
- Department of Paediatric Neurology, Bristol Children's Hospital, Bristol, UK
| | - Charles Marques Lorenço
- Faculdade de Medicina - Centro Universitário Estácio de Ribeirão Preto, Ribeirão Preto, Brazil
| | - Simona Orcesi
- Child Neurology and Psychiatry Unit, Istituto di Ricovero e Cura a Carattere Scientifico, Mondino Foundation, Pavia, Italy
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy
| | - Sylviane Peudenier
- Centre de Référence des Déficiences Intellectuelles de Causes Rares et Polyhandicap, Centre Hospitalier Régional Universitaire de Brest, Brest, France
| | - Kevin Rostasy
- Department of Paediatric Neurology, Children's Hospital Datteln, Witten/Herdecke University, Datteln, Germany
| | - Caroline A Salmon
- Department of Paediatrics, Royal Surrey County Hospital, Guildford, UK
| | - Christiaan Scott
- University of Cape Town, Red Cross War Memorial Children's Hospital, Cape Town, South Africa
| | - Davide Tonduti
- Center for diagnosis and treatment of Leukodystrophies, Pediatric Neurology Unit, V. Buzzi Children's Hospital, Milano, Italy
| | - Guy Touati
- Reference Center for Inborn Errors of Metabolism-Department of Pediatrics, Hôpital des Enfants-Centre Hospitalier Universitaire de Toulouse, Toulouse, France
| | - Marialuisa Valente
- Genomic and Post-Genomic Center, Istituto di Ricovero e Cura a Carattere Scientifico, Mondino Foundation, Pavia, Italy
| | - Hélio van der Linden
- Department of Paediatric Neurology, Neurological Institute of Goiânia, Goiânia, Brazil
| | - Hilde Van Esch
- Center for Human Genetics, University Hospitals Leuven, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Marie Vermelle
- Department of Paediatrics, Centre Hospitalier de Dunkerque, Dunkerque, France
| | - Kate Webb
- University of Cape Town, Red Cross War Memorial Children's Hospital, Cape Town, South Africa
| | - Andrew P Jackson
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Martin A M Reijns
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Nick Gilbert
- Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Yanick J Crow
- Centre for Genomic and Experimental Medicine, Medical Research Council Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK.
- University of Paris, Imagine Institute, Laboratory of Neurogenetics and Neuroinflammation, Paris, France.
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3
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Yang XC, Sun Y, Aik WS, Marzluff WF, Tong L, Dominski Z. Studies with recombinant U7 snRNP demonstrate that CPSF73 is both an endonuclease and a 5'-3' exonuclease. RNA 2020; 26:1345-1359. [PMID: 32554553 PMCID: PMC7491329 DOI: 10.1261/rna.076273.120] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [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: 05/05/2020] [Accepted: 05/26/2020] [Indexed: 05/24/2023]
Abstract
Metazoan replication-dependent histone pre-mRNAs are cleaved at the 3' end by U7 snRNP, an RNA-guided endonuclease that contains U7 snRNA, seven proteins of the Sm ring, FLASH, and four polyadenylation factors: symplekin, CPSF73, CPSF100, and CstF64. A fully recombinant U7 snRNP was recently reconstituted from all 13 components for functional and structural studies and shown to accurately cleave histone pre-mRNAs. Here, we analyzed the activity of recombinant U7 snRNP in more detail. We demonstrate that in addition to cleaving histone pre-mRNAs endonucleolytically, reconstituted U7 snRNP acts as a 5'-3' exonuclease that degrades the downstream product generated from histone pre-mRNAs as a result of the endonucleolytic cleavage. Surprisingly, recombinant U7 snRNP also acts as an endonuclease on single-stranded DNA substrates. All these activities depend on the ability of U7 snRNA to base-pair with the substrate and on the presence of the amino-terminal domain (NTD) of symplekin in either cis or trans, and are abolished by mutations within the catalytic center of CPSF73, or by binding of the NTD to the SSU72 phosphatase of RNA polymerase II. Altogether, our results demonstrate that recombinant U7 snRNP functionally mimics its endogenous counterpart and provide evidence that CPSF73 is both an endonuclease and a 5'-3' exonuclease, consistent with the activity of other members of the β-CASP family. Our results also raise the intriguing possibility that CPSF73 may be involved in some aspects of DNA metabolism in vivo.
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Affiliation(s)
- Xiao-Cui Yang
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Yadong Sun
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Wei Shen Aik
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Zbigniew Dominski
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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4
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Fan J, Wang K, Du X, Wang J, Chen S, Wang Y, Shi M, Zhang L, Wu X, Zheng D, Wang C, Wang L, Tian B, Li G, Zhou Y, Cheng H. ALYREF links 3'-end processing to nuclear export of non-polyadenylated mRNAs. EMBO J 2019; 38:e99910. [PMID: 30858280 PMCID: PMC6484419 DOI: 10.15252/embj.201899910] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [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: 06/05/2018] [Revised: 01/19/2019] [Accepted: 02/14/2019] [Indexed: 11/09/2022] Open
Abstract
The RNA-binding protein ALYREF plays key roles in nuclear export and also 3'-end processing of polyadenylated mRNAs, but whether such regulation also extends to non-polyadenylated RNAs is unknown. Replication-dependent (RD)-histone mRNAs are not polyadenylated, but instead end in a stem-loop (SL) structure. Here, we demonstrate that ALYREF prevalently binds a region next to the SL on RD-histone mRNAs. SL-binding protein (SLBP) directly interacts with ALYREF and promotes its recruitment. ALYREF promotes histone pre-mRNA 3'-end processing by facilitating U7-snRNP recruitment through physical interaction with the U7-snRNP-specific component Lsm11. Furthermore, ALYREF, together with other components of the TREX complex, enhances histone mRNA export. Moreover, we show that 3'-end processing promotes ALYREF recruitment and histone mRNA export. Together, our results point to an important role of ALYREF in coordinating 3'-end processing and nuclear export of non-polyadenylated mRNAs.
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Affiliation(s)
- Jing Fan
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Ke Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Xian Du
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Jianshu Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Suli Chen
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Yimin Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Min Shi
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Li Zhang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Xudong Wu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Dinghai Zheng
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Changshou Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Lantian Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
| | - Bin Tian
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Yu Zhou
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Hong Cheng
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences University of Chinese Academy of Sciences, Shanghai, China
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5
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Sabath I, Skrajna A, Yang XC, Dadlez M, Marzluff WF, Dominski Z. 3'-End processing of histone pre-mRNAs in Drosophila: U7 snRNP is associated with FLASH and polyadenylation factors. RNA 2013; 19:1726-44. [PMID: 24145821 PMCID: PMC3884669 DOI: 10.1261/rna.040360.113] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [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] [Indexed: 05/06/2023]
Abstract
3'-End cleavage of animal replication-dependent histone pre-mRNAs is controlled by the U7 snRNP. Lsm11, the largest component of the U7-specific Sm ring, interacts with FLASH, and in mammalian nuclear extracts these two proteins form a platform that recruits the CPSF73 endonuclease and other polyadenylation factors to the U7 snRNP. FLASH is limiting, and the majority of the U7 snRNP in mammalian extracts exists as a core particle consisting of the U7 snRNA and the Sm ring. Here, we purified the U7 snRNP from Drosophila nuclear extracts and characterized its composition by mass spectrometry. In contrast to the mammalian U7 snRNP, a significant fraction of the Drosophila U7 snRNP contains endogenous FLASH and at least six subunits of the polyadenylation machinery: symplekin, CPSF73, CPSF100, CPSF160, WDR33, and CstF64. The same composite U7 snRNP is recruited to histone pre-mRNA for 3'-end processing. We identified a motif in Drosophila FLASH that is essential for the recruitment of the polyadenylation complex to the U7 snRNP and analyzed the role of other factors, including SLBP and Ars2, in 3'-end processing of Drosophila histone pre-mRNAs. SLBP that binds the upstream stem-loop structure likely recruits a yet-unidentified essential component(s) to the processing machinery. In contrast, Ars2, a protein previously shown to interact with FLASH in mammalian cells, is dispensable for processing in Drosophila. Our studies also demonstrate that Drosophila symplekin and three factors involved in cleavage and polyadenylation-CPSF, CstF, and CF Im-are present in Drosophila nuclear extracts in a stable supercomplex.
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Affiliation(s)
- Ivan Sabath
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Aleksandra Skrajna
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 00-901 Warsaw, Poland
| | - Xiao-cui Yang
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Michał Dadlez
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 00-901 Warsaw, Poland
- Institute of Genetics and Biotechnology, Warsaw University, 02-106 Warsaw, Poland
| | - William F. Marzluff
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Zbigniew Dominski
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Corresponding authorE-mail
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6
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Burch BD, Godfrey AC, Gasdaska PY, Salzler HR, Duronio RJ, Marzluff WF, Dominski Z. Interaction between FLASH and Lsm11 is essential for histone pre-mRNA processing in vivo in Drosophila. RNA 2011; 17:1132-47. [PMID: 21525146 PMCID: PMC3096045 DOI: 10.1261/rna.2566811] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [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] [Indexed: 05/06/2023]
Abstract
Metazoan replication-dependent histone mRNAs are the only nonpolyadenylated cellular mRNAs. Formation of the histone mRNA 3' end requires the U7 snRNP, which contains Lsm10 and Lsm11, and FLASH, a processing factor that binds Lsm11. Here, we identify sequences in Drosophila FLASH (dFLASH) that bind Drosophila Lsm11 (dLsm11), allow localization of dFLASH to the nucleus and histone locus body (HLB), and participate in histone pre-mRNA processing in vivo. Amino acids 105-154 of dFLASH bind to amino acids 1-78 of dLsm11. A two-amino acid mutation of dLsm11 that prevents dFLASH binding but does not affect localization of U7 snRNP to the HLB cannot rescue the lethality or histone pre-mRNA processing defects resulting from an Lsm11 null mutation. The last 45 amino acids of FLASH are required for efficient localization to the HLB in Drosophila cultured cells. Removing the first 64 amino acids of FLASH has no effect on processing in vivo. Removal of 13 additional amino acids of dFLASH results in a dominant negative protein that binds Lsm11 but inhibits processing of histone pre-mRNA in vivo. Inhibition requires the Lsm11 binding site, suggesting that the mutant dFLASH protein sequesters the U7 snRNP in an inactive complex and that residues between 64 and 77 of dFLASH interact with a factor required for processing. Together, these studies demonstrate that direct interaction between dFLASH and dLsm11 is essential for histone pre-mRNA processing in vivo and for proper development and viability in flies.
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MESH Headings
- Animals
- Binding Sites
- Carrier Proteins/chemistry
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cells, Cultured
- Drosophila/genetics
- Drosophila/metabolism
- Drosophila Proteins/chemistry
- Drosophila Proteins/genetics
- Drosophila Proteins/metabolism
- Histones/genetics
- Histones/metabolism
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional
- RNA, Heterogeneous Nuclear/genetics
- RNA, Heterogeneous Nuclear/metabolism
- RNA, Messenger/metabolism
- Ribonucleoprotein, U7 Small Nuclear/genetics
- Ribonucleoprotein, U7 Small Nuclear/metabolism
- Ribonucleoproteins, Small Nuclear/chemistry
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
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Affiliation(s)
- Brandon D Burch
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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7
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Godfrey AC, White AE, Tatomer DC, Marzluff WF, Duronio RJ. The Drosophila U7 snRNP proteins Lsm10 and Lsm11 are required for histone pre-mRNA processing and play an essential role in development. RNA 2009; 15:1661-72. [PMID: 19620235 PMCID: PMC2743060 DOI: 10.1261/rna.1518009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [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: 12/16/2008] [Accepted: 05/21/2009] [Indexed: 05/23/2023]
Abstract
Metazoan replication-dependent histone mRNAs are not polyadenylated, and instead terminate in a conserved stem-loop structure generated by an endonucleolytic cleavage of the pre-mRNA involving U7 snRNP. U7 snRNP contains two like-Sm proteins, Lsm10 and Lsm11, which replace SmD1 and SmD2 in the canonical heptameric Sm protein ring that binds spliceosomal snRNAs. Here we show that mutations in either the Drosophila Lsm10 or the Lsm11 gene disrupt normal histone pre-mRNA processing, resulting in production of poly(A)+ histone mRNA as a result of transcriptional read-through to cryptic polyadenylation sites present downstream from each histone gene. This molecular phenotype is indistinguishable from that which we previously described for mutations in U7 snRNA. Lsm10 protein fails to accumulate in Lsm11 mutants, suggesting that a pool of Lsm10-Lsm11 dimers provides precursors for U7 snRNP assembly. Unexpectedly, U7 snRNA was detected in Lsm11 and Lsm1 mutants and could be precipitated with anti-trimethylguanosine antibodies, suggesting that it assembles into a snRNP particle in the absence of Lsm10 and Lsm11. However, this U7 snRNA could not be detected at the histone locus body, suggesting that Lsm10 and Lsm11 are necessary for U7 snRNP localization. In contrast to U7 snRNA null mutants, which are viable, Lsm10 and Lsm11 mutants do not survive to adulthood. Because we cannot detect differences in the histone mRNA phenotype between Lsm10 or Lsm11 and U7 mutants, we propose that the different terminal developmental phenotypes result from the participation of Lsm10 and Lsm11 in an essential function that is distinct from histone pre-mRNA processing and that is independent of U7 snRNA.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Drosophila/genetics
- Drosophila/growth & development
- Drosophila/metabolism
- Drosophila Proteins/genetics
- Drosophila Proteins/physiology
- Female
- Fertility/genetics
- Genes, Developmental/physiology
- Genes, Lethal/genetics
- Histones/genetics
- Histones/metabolism
- Male
- Mutation/physiology
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional/genetics
- RNA Processing, Post-Transcriptional/physiology
- RNA, Messenger/metabolism
- Ribonucleoprotein, U7 Small Nuclear/genetics
- Ribonucleoprotein, U7 Small Nuclear/physiology
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/physiology
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Affiliation(s)
- Ashley C Godfrey
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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8
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Abstract
The replication-dependent histone mRNAs in metazoa are not polyadenylated, in contrast to the bulk of mRNA. Instead, they contain an RNA stem-loop (SL) structure close to the 3' end of the mature RNA, and this 3' end is generated by cleavage using a machinery involving the U7 snRNP and protein factors such as the stem-loop binding protein (SLBP). This machinery of 3' end processing is related to that of polyadenylation as protein components are shared between the systems. It is commonly believed that histone 3' end processing is restricted to metazoa and green algae. In contrast, polyadenylation is ubiquitous in Eukarya. However, using computational approaches, we have now identified components of histone 3' end processing in a number of protozoa. Thus, the histone mRNA stem-loop structure as well as the SLBP protein are present in many different protozoa, including Dictyostelium, alveolates, Trypanosoma, and Trichomonas. These results show that the histone 3' end processing machinery is more ancient than previously anticipated and can be traced to the root of the eukaryotic phylogenetic tree. We also identified histone mRNAs from both metazoa and protozoa that are polyadenylated but also contain the signals characteristic of histone 3' end processing. These results provide further evidence that some histone genes are regulated at the level of 3' end processing to produce either polyadenylated RNAs or RNAs with the 3' end characteristic of replication-dependent histone mRNAs.
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Affiliation(s)
- Marcela Dávila López
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy at Göteborg University, SE-405 30 Göteborg, Sweden
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9
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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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10
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Stepanova IS, Bogolyubov DS, Skovorodkin IN, Parfenov VN. Cajal bodies and interchromatin granule clusters in cricket oocytes: Composition, dynamics and interactions. Cell Biol Int 2007; 31:203-14. [PMID: 17123844 DOI: 10.1016/j.cellbi.2006.04.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 03/06/2006] [Accepted: 04/20/2006] [Indexed: 10/24/2022]
Abstract
The organization and molecular composition of complicated Cajal bodies (CBs) and interchromatin granule clusters (IGCs) in oocytes of the house cricket, Acheta domesticus, were studied using immunofluorescent/confocal and Immunogold labeling/electron microscopy. In A. domesticus oocytes, the CB consists of the fibrillar matrix and a central cavity containing a predominantly granular body with insertions of tightly packed fibrillar material. The latter structure was identified as an "internal" IGC, since it is enriched with the SC35 protein, a marker for IGCs. The IGCs located outside the CB were also identified. Microinjections of the fluorescein-tagged U7 snRNA into the ooplasm showed the targeting of the U7 to the matrix of the CB. Some other essential CB components (coilin, snRNPs, fibrillarin) were found to be colocalized in the matrix of the CB. Neither confocal nor Immunogold microscopy revealed significant amounts of RNA polymerase II (pol II) in the CB of A. domesticus oocytes. The splicing factor SC35 was detected in the matrix of the CB. In oocytes treated with DRB, the amount of IGCs in the nucleoplasm increased significantly, granular and fibrillar components of IGCs were segregated, and the fibrillar areas accumulated pol II. Additionally, IG-like granules were shown to display on the surface of the CB probably due to a shifting from the internal IGC. We believe that in A. domesticus oocytes, CBs are involved in nuclear distribution of splicing factors, but their role in pol II transport is less significant. We also suggest that the formation of complicated CBs is a result of interconnection between two different nuclear domains, CBs and IGCs.
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Affiliation(s)
- Irina S Stepanova
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia
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11
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Wagner EJ, Ospina JK, Hu Y, Dundr M, Matera AG, Marzluff WF. Conserved zinc fingers mediate multiple functions of ZFP100, a U7snRNP associated protein. RNA 2006; 12:1206-18. [PMID: 16714279 PMCID: PMC1484431 DOI: 10.1261/rna.2606] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [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] [Indexed: 05/09/2023]
Abstract
Formation of the 3' end of replication-dependent histone mRNAs is most robust during S phase and is mediated by both the stem-loop binding protein (SLBP) and the U7 snRNP. We previously identified a 100-kDa zinc finger protein (ZFP100) as a component of U7 snRNP that interacts with the SLBP/pre-mRNA complex. Here, we show that myc- or GFP-tagged ZFP100 overexpressed after transfection is concentrated in Cajal bodies (CBs), and unlike components of the spliceosomal snRNPs, photobleaching experiments demonstrate that ZFP100 is stably associated with CBs. Of the 18 zinc fingers contained within ZFP100, the region encompassing fingers 2-6 is sufficient to maintain CB localization. Zn fingers 5-10 are required for maximal binding of ZFP100 to a 20-amino-acid region of Lsm11, a U7 snRNP core protein. Expression of ZFP100 stimulates histone mRNA processing in vivo, assayed by activation of a reporter gene that encodes a GFP mRNA ending in a histone 3' end. Importantly, the domain that is required for CB localization and Lsm11 binding is also sufficient to stimulate histone pre-mRNA processing in vivo. Comparisons with other mammalian ZFP100 orthologs show that the central Zn fingers sufficient for in vivo activity are most highly conserved, whereas the number and sequence of the Zn fingers in the N- and C-terminal domains vary.
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Affiliation(s)
- Eric J Wagner
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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12
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Abstract
Cajal bodies (CBs) are nuclear organelles that are usually identified by the marker protein p80-coilin. Because no orthologue of coilin is known in Drosophila melanogaster, we identified D. melanogaster CBs using probes for other components that are relatively diagnostic for CBs in vertebrate cells. U85 small CB–specific RNA, U2 small nuclear RNA, the survival of motor neurons protein, and fibrillarin occur together in a nuclear body that is closely associated with the nucleolus. Based on its similarity to CBs in other organisms, we refer to this structure as the D. melanogaster CB. Surprisingly, the D. melanogaster U7 small nuclear RNP resides in a separate nuclear body, which we call the histone locus body (HLB). The HLB is invariably colocalized with the histone gene locus. Thus, canonical CB components are distributed into at least two nuclear bodies in D. melanogaster. The identification of these nuclear bodies now permits a broad range of questions to be asked about CB structure and function in a genetically tractable organism.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Cell Nucleus/genetics
- Cell Nucleus/metabolism
- Cell Nucleus/ultrastructure
- Coiled Bodies/genetics
- Coiled Bodies/metabolism
- Coiled Bodies/ultrastructure
- Drosophila melanogaster/cytology
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Embryo, Nonmammalian/cytology
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/metabolism
- Evolution, Molecular
- Gene Expression Regulation, Developmental/physiology
- Histones/genetics
- Histones/metabolism
- Histones/ultrastructure
- Larva/cytology
- Larva/growth & development
- Larva/metabolism
- Multigene Family/physiology
- Protein Biosynthesis/physiology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Ribonucleoprotein, U7 Small Nuclear/genetics
- Ribonucleoprotein, U7 Small Nuclear/metabolism
- Ribonucleoprotein, U7 Small Nuclear/ultrastructure
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
- Species Specificity
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Affiliation(s)
- Ji-Long Liu
- Department of Embryology, Carnegie Institution of Washington, Baltimore, MD 21218, USA
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13
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Kolev NG, Steitz JA. In vivo assembly of functional U7 snRNP requires RNA backbone flexibility within the Sm-binding site. Nat Struct Mol Biol 2006; 13:347-53. [PMID: 16547514 DOI: 10.1038/nsmb1075] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [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: 07/06/2005] [Accepted: 02/17/2006] [Indexed: 11/08/2022]
Abstract
Most histone precursor mRNAs (pre-mRNAs) in metazoans are matured by 3'-end cleavage directed by the U7 small nuclear ribonucleoprotein (snRNP). RNA functional groups necessary for in vivo assembly and activity of the U7 snRNP were examined by nucleotide-analog interference mapping and mutagenesis using a chimeric mouse histone H4 pre-mRNA-U7 snRNA construct that is cleaved in cis in Xenopus laevis oocytes. Assembly of the unique U7 Sm protein core is rate limiting for processing in vivo and requires four conserved nucleotides within the U7 Sm-binding site, as well as the correct positioning and size of the U7 terminal stem-loop structure. To our surprise, pseudouridine substitution revealed a requirement for backbone flexibility at a particular position within the U7 Sm site, providing in vivo biochemical evidence that an unusual C2'-endo sugar conformation is necessary for assembly of the Sm ring.
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Affiliation(s)
- Nikolay G Kolev
- Howard Hughes Medical Institute, Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06536, USA
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14
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Dominski Z, Yang XC, Marzluff WF. The polyadenylation factor CPSF-73 is involved in histone-pre-mRNA processing. Cell 2005; 123:37-48. [PMID: 16213211 DOI: 10.1016/j.cell.2005.08.002] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [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: 05/06/2005] [Revised: 07/08/2005] [Accepted: 08/03/2005] [Indexed: 11/21/2022]
Abstract
During 3' end processing, histone pre-mRNAs are cleaved 5 nucleotides after a conserved stem loop by an endonuclease dependent on the U7 small nuclear ribonucleoprotein (snRNP). The upstream cleavage product corresponds to the mature histone mRNA, while the downstream product is degraded by a 5'-3' exonuclease, also dependent on the U7 snRNP. To identify the two nuclease activities, we carried out UV-crosslinking studies using both the complete RNA substrate and the downstream cleavage product, each containing a single radioactive phosphate and a phosphorothioate modification at the cleavage site. We detected a protein migrating at 85 kDa that crosslinked to each substrate in a U7-dependent manner. Immunoprecipitation experiments identified this protein as CPSF-73, a known component of the cleavage/polyadenylation machinery. These studies suggest that CPSF-73 is both the endonuclease and 5'-3' exonuclease in histone-pre-mRNA processing and reveal an evolutionary link between 3' end formation of histone mRNAs and polyadenylated mRNAs.
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Affiliation(s)
- Zbigniew Dominski
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
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15
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Abstract
Metazoan replication-dependent histone mRNAs are the only eukaryotic mRNAs that lack polyA tails. The genes for the five histone proteins have remained physically linked during evolution. Expression of histone mRNAs and histone proteins requires a unique set of factors, and may be coordinated by association of the histone genes with Cajal bodies. Recently several novel factors, including components of the U7 snRNP, as well as proteins involved in regulation of histone gene expression, have been described.
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Affiliation(s)
- William F Marzluff
- Program in Molecular Biology and Biotechnology, Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, North Carolina 27599, USA.
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16
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Azzouz TN, Schumperli D. Evolutionary conservation of the U7 small nuclear ribonucleoprotein in Drosophila melanogaster. RNA 2003; 9:1532-41. [PMID: 14624008 PMCID: PMC1370506 DOI: 10.1261/rna.5143303] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Accepted: 09/04/2003] [Indexed: 05/21/2023]
Abstract
The U7 snRNP involved in histone RNA 3' end processing is related to but biochemically distinct from spliceosomal snRNPs. In vertebrates, the Sm core structure assembling around the noncanonical Sm-binding sequence of U7 snRNA contains only five of the seven standard Sm proteins. The missing Sm D1 and D2 subunits are replaced by U7-specific Sm-like proteins Lsm10 and Lsm11, at least the latter of which is important for histone RNA processing. So far, it was unknown if this special U7 snRNP composition is conserved in invertebrates. Here we describe several putative invertebrate Lsm10 and Lsm11 orthologs that display low but clear sequence similarity to their vertebrate counterparts. Immunoprecipitation studies in Drosophila S2 cells indicate that the Drosophila Lsm10 and Lsm11 orthologs (dLsm10 and dLsm11) associate with each other and with Sm B, but not with Sm D1 and D2. Moreover, dLsm11 associates with the recently characterized Drosophila U7 snRNA and, indirectly, with histone H3 pre-mRNA. Furthermore, dLsm10 and dLsm11 can assemble into U7 snRNPs in mammalian cells. These experiments demonstrate a strong evolutionary conservation of the unique U7 snRNP composition, despite a high degree of primary sequence divergence of its constituents. Therefore, Drosophila appears to be a suitable system for further genetic studies of the cell biology of U7 snRNPs.
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Affiliation(s)
- Teldja N Azzouz
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
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17
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Abstract
In animals, replication-dependent histone genes are expressed in dividing somatic cells during S phase to maintain chromatin condensation. Histone mRNA 3'-end formation is an essential regulatory step producing an mRNA with a hairpin structure at the 3'-end. This requires the interaction of the U7 small nuclear ribonucleoprotein particle (snRNP) with a purine-rich spacer element and of the hairpin-binding protein with the hairpin element, respectively, in the 3'-untranslated region of histone RNA. Here, we demonstrate that bona fide histone RNA 3' processing takes place in Xenopus egg extracts in a reaction dependent on the addition of synthetic U7 RNA that is assembled into a ribonucleoprotein particle by protein components available in the extract. In addition to reconstituted U7 snRNP, Xenopus hairpin-binding protein SLBP1 is necessary for efficient processing. Histone RNA 3' processing is not affected by addition of non-destructible cyclin B, which drives the egg extract into M phase, but SLBP1 is phosphorylated in this extract. SPH-1, the Xenopus homologue of human p80-coilin found in coiled bodies, is associated with U7 snRNPs. However, this does not depend on the U7 RNA being able to process histone RNA and also occurs with U1 snRNPs; therefore, association of SPH1 cannot be considered as a hallmark of a functional U7 snRNP.
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Affiliation(s)
- B Müller
- Abteilung Entwicklungsbiologie, Zoologisches Institut, Universität Bern, Baltzerstrasse 4, CH 3012 Bern, Switzerland.
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