1
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Ducoli L, Zarnegar BJ, Porter DF, Meyers RM, Miao W, Riley NM, Srinivasan S, Jackrazi LV, Yang YY, Li Z, Wang Y, Bertozzi CR, Flynn RA, Khavari PA. irCLIP-RNP and Re-CLIP reveal patterns of dynamic protein assemblies on RNA. Nature 2025; 641:769-778. [PMID: 40140581 DOI: 10.1038/s41586-025-08787-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 02/13/2025] [Indexed: 03/28/2025]
Abstract
RNA-binding proteins (RBPs) control varied processes, including RNA splicing, stability, transport and translation1-3. Dysfunctional RNA-RBP interactions contribute to the pathogenesis of human disease1,4,5; however, characterizing the nature and dynamics of multiprotein assemblies on RNA has been challenging. Here, to address this, non-isotopic ligation-based ultraviolet-light-induced cross-linking and immunoprecipitation6 was combined with mass spectrometry (irCLIP-RNP) to identify RNA-dependent associated proteins (RDAPs) co-bound to RNA with any RBP of interest. irCLIP-RNP defined landscapes of multimeric protein assemblies on RNA, revealing patterns of RBP-RNA associations, including cell-type-selective combinatorial relationships between RDAPs and primary RBPs. irCLIP-RNP also defined dynamic RDAP remodelling in response to epidermal growth factor (EGF), revealing that EGF-induced recruitment of UPF1 adjacent to HNRNPC promotes splicing surveillance of cell proliferation mRNAs. To identify the RNAs simultaneously co-bound by multiple studied RBPs, a sequential immunoprecipitation irCLIP (Re-CLIP) method was also developed. Re-CLIP confirmed binding relationships observed in irCLIP-RNP and identified HNRNPC and UPF1 RBP co-binding on RND3 and DDX3X mRNAs. irCLIP-RNP and Re-CLIP provide a framework to identify and characterize dynamic RNA-protein assemblies in living cells.
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Affiliation(s)
- Luca Ducoli
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA
| | - Brian J Zarnegar
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA
| | - Douglas F Porter
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA
| | - Robin M Meyers
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA
| | - Weili Miao
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA
| | - Nicholas M Riley
- Department of Chemistry and Sarafan ChEM-H, Stanford University, Stanford, CA, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Suhas Srinivasan
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA
| | | | - Yen-Yu Yang
- Department of Chemistry, University of California, Riverside, CA, USA
| | - Zhouxian Li
- Department of Chemistry, University of California, Riverside, CA, USA
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, CA, USA
| | - Carolyn R Bertozzi
- Department of Chemistry and Sarafan ChEM-H, Stanford University, Stanford, CA, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Ryan A Flynn
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Paul A Khavari
- Program in Epithelial Biology, Stanford University, Stanford, CA, USA.
- Program in Cancer Biology, Stanford University, Stanford, CA, USA.
- Veterans Affairs, Palo Alto Healthcare System, Palo Alto, CA, USA.
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2
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Dreyfuss G. RNA-binding proteins in disease etiology: fragile X syndrome and spinal muscular atrophy. RNA (NEW YORK, N.Y.) 2025; 31:277-283. [PMID: 39694825 PMCID: PMC11874976 DOI: 10.1261/rna.080353.124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2024] [Accepted: 12/04/2024] [Indexed: 12/20/2024]
Abstract
All RNAs exist in complexes (RNPs) with RNA-binding proteins (RBPs). Studies in my lab since the 1980s have identified, sequenced and characterized the major pre-mRNA- and mRNA-RBPs (hnRNPs/mRNPs), revealing RNA-binding domains and common features of numerous RBPs and their central roles in posttranscriptional gene regulation. The first links between RBPs and RNPs to diseases emerged serendipitously for fragile X syndrome, as its gene (FMR1) encoded RBP (FMRP), and spinal muscular atrophy (SMA), caused by deficits in survival motor neurons (SMN). Discoveries of the SMN complex and its unanticipated function in RNP assembly, essential for spliceosomal snRNP biogenesis, advanced understanding of RNA biology and pathogenesis. I reflect on how these and other contributions (e.g., nucleocytoplasmic shuttling, telescripting) originated from curiosity-driven exploration and highly collaborative lab culture. The vast RNA and RBP assortments are beneficial, but increase complexity and chances of disorders, making the RNP sphere a rich source for future discoveries.
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Affiliation(s)
- Gideon Dreyfuss
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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3
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Ducoli L, Zarnegar BJ, Porter DF, Meyers RM, Miao W, Riley NM, Srinivasan S, Jackrazi LV, Yang YY, Li Z, Wang Y, Bertozzi CR, Flynn RA, Khavari PA. irCLIP-RNP and Re-CLIP reveal patterns of dynamic protein associations on RNA. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.27.615518. [PMID: 39386644 PMCID: PMC11463378 DOI: 10.1101/2024.09.27.615518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/12/2024]
Abstract
RNA binding proteins ( RBPs ) control varied processes, including RNA splicing, stability, transport, and translation 1-3 . Dysfunctional RNA-RBP interactions contribute to the pathogenesis of human disease 1,4,5 , however, characterizing the nature and dynamics of multiprotein assemblies on RNA has been challenging. To address this, non-isotopic ligation-based ultraviolet crosslinking immunoprecipitation 6 was combined with mass spectrometry ( irCLIP-RNP ) to identify RNA-dependent associated proteins ( RDAPs ) co-bound to RNA with any RBP of interest. irCLIP-RNP defined landscapes of multimeric protein assemblies on RNA, uncovering previously unknown patterns of RBP-RNA associations, including cell-type-selective combinatorial relationships between RDAPs and primary RBPs. irCLIP-RNP also defined dynamic RDAP remodeling in response to epidermal growth factor ( EGF ), uncovering EGF-induced recruitment of UPF1 adjacent to HNRNPC to effect splicing surveillance of cell proliferation mRNAs. To identify the RNAs simultaneously co-bound by multiple studied RBPs, a sequential immunoprecipitation irCLIP ( Re-CLIP ) method was also developed. Re-CLIP confirmed binding relationships seen in irCLIP-RNP and detected simultaneous HNRNPC and UPF1 co-binding on RND3 and DDX3X mRNAs. irCLIP-RNP and Re-CLIP provide a framework to identify and characterize dynamic RNA-protein assemblies in living cells.
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4
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Tilliole P, Fix S, Godin JD. hnRNPs: roles in neurodevelopment and implication for brain disorders. Front Mol Neurosci 2024; 17:1411639. [PMID: 39086926 PMCID: PMC11288931 DOI: 10.3389/fnmol.2024.1411639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 06/17/2024] [Indexed: 08/02/2024] Open
Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) constitute a family of multifunctional RNA-binding proteins able to process nuclear pre-mRNAs into mature mRNAs and regulate gene expression in multiple ways. They comprise at least 20 different members in mammals, named from A (HNRNP A1) to U (HNRNP U). Many of these proteins are components of the spliceosome complex and can modulate alternative splicing in a tissue-specific manner. Notably, while genes encoding hnRNPs exhibit ubiquitous expression, increasing evidence associate these proteins to various neurodevelopmental and neurodegenerative disorders, such as intellectual disability, epilepsy, microcephaly, amyotrophic lateral sclerosis, or dementias, highlighting their crucial role in the central nervous system. This review explores the evolution of the hnRNPs family, highlighting the emergence of numerous new members within this family, and sheds light on their implications for brain development.
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Affiliation(s)
- Pierre Tilliole
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, IGBMC, Illkirch, France
- Centre National de la Recherche Scientifique, CNRS, UMR7104, Illkirch, France
- Institut National de la Santé et de la Recherche Médicale, INSERM, U1258, Illkirch, France
- Université de Strasbourg, Strasbourg, France
| | - Simon Fix
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, IGBMC, Illkirch, France
- Centre National de la Recherche Scientifique, CNRS, UMR7104, Illkirch, France
- Institut National de la Santé et de la Recherche Médicale, INSERM, U1258, Illkirch, France
- Université de Strasbourg, Strasbourg, France
| | - Juliette D. Godin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, IGBMC, Illkirch, France
- Centre National de la Recherche Scientifique, CNRS, UMR7104, Illkirch, France
- Institut National de la Santé et de la Recherche Médicale, INSERM, U1258, Illkirch, France
- Université de Strasbourg, Strasbourg, France
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5
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Jia R, Che X, Jia J, Guo J. FOXM1a Isoform of Oncogene FOXM1 Is a Tumor Suppressor Suppressed by hnRNP C in Oral Squamous Cell Carcinoma. Biomolecules 2023; 13:1331. [PMID: 37759731 PMCID: PMC10526205 DOI: 10.3390/biom13091331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 08/24/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
FOXM1 is an oncogenic transcriptional factor and includes several isoforms generated by alternative splicing. Inclusion of alternative exon 9 produces FOXM1a, a transcriptionally inactive isoform. However, the role of FOXM1a in tumorigenesis remains unknown. In addition, the regulatory mechanisms of exon 9 splicing are also unclear. In the present study, we found that overexpression of FOXM1a significantly reduced cell proliferation and colony formation of oral squamous cell carcinoma (OSCC) cell proliferation in vitro. Importantly, OSCC cells with FOXM1a overexpression showed significantly slower tumor formation in nude mice. Moreover, we identified a U-rich exonic splicing suppressor (ESS) which is responsible for exon 9 skipping. Splicing factor heterogeneous nuclear ribonucleoprotein C (hnRNP C) can bind to the ESS and suppress exon 9 inclusion and FOXM1a expression. Silence of hnRNP C also significantly suppresses OSCC cell proliferation. HnRNP C is significantly co-expressed with FOXM1 in cancers. Our study uncovered a novel regulatory mechanism of oncogene FOXM1 expression in OSCC.
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Affiliation(s)
- Rong Jia
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan 430072, China; (R.J.); (X.C.)
| | - Xiaoxuan Che
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan 430072, China; (R.J.); (X.C.)
| | - Jun Jia
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan 430072, China; (R.J.); (X.C.)
- Department of Oral and Maxillofacial Surgery, School & Hospital of Stomatology, Wuhan University, Wuhan 430072, China
| | - Jihua Guo
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan 430072, China; (R.J.); (X.C.)
- Department of Endodontics, School & Hospital of Stomatology, Wuhan University, Wuhan 430072, China
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6
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Mann JT, Riley BA, Baker SF. All differential on the splicing front: Host alternative splicing alters the landscape of virus-host conflict. Semin Cell Dev Biol 2023; 146:40-56. [PMID: 36737258 DOI: 10.1016/j.semcdb.2023.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 01/24/2023] [Accepted: 01/25/2023] [Indexed: 02/05/2023]
Abstract
Alternative RNA splicing is a co-transcriptional process that richly increases proteome diversity, and is dynamically regulated based on cell species, lineage, and activation state. Virus infection in vertebrate hosts results in rapid host transcriptome-wide changes, and regulation of alternative splicing can direct a combinatorial effect on the host transcriptome. There has been a recent increase in genome-wide studies evaluating host alternative splicing during viral infection, which integrates well with prior knowledge on viral interactions with host splicing proteins. A critical challenge remains in linking how these individual events direct global changes, and whether alternative splicing is an overall favorable pathway for fending off or supporting viral infection. Here, we introduce the process of alternative splicing, discuss how to analyze splice regulation, and detail studies on genome-wide and splice factor changes during viral infection. We seek to highlight where the field can focus on moving forward, and how incorporation of a virus-host co-evolutionary perspective can benefit this burgeoning subject.
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Affiliation(s)
- Joshua T Mann
- Infectious Disease Program, Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Brent A Riley
- Infectious Disease Program, Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Steven F Baker
- Infectious Disease Program, Lovelace Biomedical Research Institute, Albuquerque, NM, USA.
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7
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Dantsuji S, Ohno M, Taniguchi I. The hnRNP C tetramer binds to CBC on mRNA and impedes PHAX recruitment for the classification of RNA polymerase II transcripts. Nucleic Acids Res 2023; 51:1393-1408. [PMID: 36620872 PMCID: PMC9943658 DOI: 10.1093/nar/gkac1250] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Revised: 12/11/2022] [Accepted: 12/15/2022] [Indexed: 01/10/2023] Open
Abstract
In eukaryotic cells, various classes of RNAs are exported to the cytoplasm by class-specific factors. Accumulating evidence has shown that export factors affect the fate of RNA, demonstrating the importance of proper RNA classification upon export. We previously reported that RNA polymerase II transcripts were classified after synthesis depending on their length, and identified heterogeneous nuclear ribonucleoprotein (hnRNP) C as the key classification factor. HnRNP C inhibits the recruitment of PHAX, an adapter protein for spliceosomal U snRNA export, to long transcripts, navigating these RNAs to the mRNA export pathway. However, the mechanisms by which hnRNP C inhibits PHAX recruitment to mRNA remain unknown. We showed that the cap-binding complex, a bridging factor between m7G-capped RNA and PHAX, directly interacted with hnRNP C on mRNA. Additionally, we revealed that the tetramer-forming activity of hnRNP C and its strong RNA-binding activity were crucial for the inhibition of PHAX binding to longer RNAs. These results suggest that mRNA is wrapped around the hnRNP C tetramer without a gap from the cap, thereby impeding the recruitment of PHAX. The results obtained on the mode of length-specific RNA classification by the hnRNP C tetramer will provide mechanistic insights into hnRNP C-mediated RNA biogenesis.
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Affiliation(s)
- Sayaka Dantsuji
- Institute for Life and Medical Sciences, Kyoto University, Kyoto, Kyoto 606-8507, Japan
| | - Mutsuhito Ohno
- Institute for Life and Medical Sciences, Kyoto University, Kyoto, Kyoto 606-8507, Japan
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8
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Feng J, Zhou J, Lin Y, Huang W. hnRNP A1 in RNA metabolism regulation and as a potential therapeutic target. Front Pharmacol 2022; 13:986409. [PMID: 36339596 PMCID: PMC9634572 DOI: 10.3389/fphar.2022.986409] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 10/10/2022] [Indexed: 11/22/2022] Open
Abstract
Abnormal RNA metabolism, regulated by various RNA binding proteins, can have functional consequences for multiple diseases. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is an important RNA binding protein, that regulates various RNA metabolic processes, including transcription, alternative splicing of pre-mRNA, translation, miRNA processing and mRNA stability. As a potent splicing factor, hnRNP A1 can regulate multiple splicing events, including itself, collaborating with other cooperative or antagonistical splicing factors by binding to splicing sites and regulatory elements in exons or introns. hnRNP A1 can modulate gene transcription by directly interacting with promoters or indirectly impacting Pol II activities. Moreover, by interacting with the internal ribosome entry site (IRES) or 3'-UTR of mRNAs, hnRNP A1 can affect mRNA translation. hnRNP A1 can alter the stability of mRNAs by binding to specific locations of 3'-UTR, miRNAs biogenesis and Nonsense-mediated mRNA decay (NMD) pathway. In this review, we conclude the selective sites where hnRNP A1 binds to RNA and DNA, and the co-regulatory factors that interact with hnRNP A1. Given the dysregulation of hnRNP A1 in diverse diseases, especially in cancers and neurodegeneration diseases, targeting hnRNP A1 for therapeutic treatment is extremely promising. Therefore, this review also provides the small-molecule drugs, biomedicines and novel strategies targeting hnRNP A1 for therapeutic purposes.
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Affiliation(s)
- Jianguo Feng
- Guangdong Engineering Research Center for Translation of Medical 3D Printing Application, Guangdong Provincial Key Laboratory of Medical Biomechanics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
- Affiliated Xinhui Hospital, People’s Hospital of Xinhui District, Southern Medical University, Jiangmen, Guangdong Province, China
- Laboratory of Anesthesiology, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, China
| | - Jianlong Zhou
- Affiliated Xinhui Hospital, People’s Hospital of Xinhui District, Southern Medical University, Jiangmen, Guangdong Province, China
- Department of Oncology, Guangxi International Zhuang Medicine Hospital, Nanning, China
| | - Yunxiao Lin
- Affiliated Xinhui Hospital, People’s Hospital of Xinhui District, Southern Medical University, Jiangmen, Guangdong Province, China
| | - Wenhua Huang
- Guangdong Engineering Research Center for Translation of Medical 3D Printing Application, Guangdong Provincial Key Laboratory of Medical Biomechanics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
- Affiliated Xinhui Hospital, People’s Hospital of Xinhui District, Southern Medical University, Jiangmen, Guangdong Province, China
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9
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Domanski M, Dedic E, Pérez ME, Cléry A, Campagne S, Uldry AC, Braga S, Heller M, Rabl J, Afanasyev P, Boehringer D, Nováček J, Allain FT, Mühlemann O. 40S hnRNP particles are a novel class of nuclear biomolecular condensates. Nucleic Acids Res 2022; 50:6300-6312. [PMID: 35687109 PMCID: PMC9226511 DOI: 10.1093/nar/gkac457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/12/2022] [Accepted: 05/16/2022] [Indexed: 11/17/2022] Open
Abstract
Heterogenous nuclear ribonucleoproteins (hnRNPs) are abundant proteins implicated in various steps of RNA processing that assemble on nuclear RNA into larger complexes termed 40S hnRNP particles. Despite their initial discovery 55 years ago, our understanding of these intriguing macromolecular assemblies remains limited. Here, we report the biochemical purification of native 40S hnRNP particles and the determination of their complete protein composition by label-free quantitative mass spectrometry, identifying A-group and C-group hnRNPs as the major protein constituents. Isolated 40S hnRNP particles dissociate upon RNA digestion and can be reconstituted in vitro on defined RNAs in the presence of the individual protein components, demonstrating a scaffolding role for RNA in nucleating particle formation. Finally, we revealed their nanometer scale, condensate-like nature, promoted by intrinsically disordered regions of A-group hnRNPs. Collectively, we identify nuclear 40S hnRNP particles as novel dynamic biomolecular condensates.
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Affiliation(s)
- Michal Domanski
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Emil Dedic
- Institute of Biochemistry, Department of Biology, ETH Zürich, Hönggerbergring 64, 8093 Zürich, Switzerland
| | - Maria Escura Pérez
- Institute of Biochemistry, Department of Biology, ETH Zürich, Hönggerbergring 64, 8093 Zürich, Switzerland
| | - Antoine Cléry
- Institute of Biochemistry, Department of Biology, ETH Zürich, Hönggerbergring 64, 8093 Zürich, Switzerland
| | - Sébastien Campagne
- Institute of Biochemistry, Department of Biology, ETH Zürich, Hönggerbergring 64, 8093 Zürich, Switzerland
| | - Anne-Christine Uldry
- Proteomics & Mass Spectrometry Core Facility, Department for BioMedical Research (DBMR), University of Bern, Murtenstrasse 28, 3008 Bern, Switzerland
| | - Sophie Braga
- Proteomics & Mass Spectrometry Core Facility, Department for BioMedical Research (DBMR), University of Bern, Murtenstrasse 28, 3008 Bern, Switzerland
| | - Manfred Heller
- Proteomics & Mass Spectrometry Core Facility, Department for BioMedical Research (DBMR), University of Bern, Murtenstrasse 28, 3008 Bern, Switzerland
| | - Julius Rabl
- Cryo-EM Knowledge Hub, ScopeM, Otto Stern Weg 3, ETH Zürich, 8093 Zürich, Switzerland
| | - Pavel Afanasyev
- Cryo-EM Knowledge Hub, ScopeM, Otto Stern Weg 3, ETH Zürich, 8093 Zürich, Switzerland
| | - Daniel Boehringer
- Cryo-EM Knowledge Hub, ScopeM, Otto Stern Weg 3, ETH Zürich, 8093 Zürich, Switzerland
| | - Jiří Nováček
- Cryo-Electron Microscopy and Tomography Core Facility, Central European Institute of Technology, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic
| | - Frédéric T Allain
- Institute of Biochemistry, Department of Biology, ETH Zürich, Hönggerbergring 64, 8093 Zürich, Switzerland
| | - Oliver Mühlemann
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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10
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Mo L, Meng L, Huang Z, Yi L, Yang N, Li G. An analysis of the role of HnRNP C dysregulation in cancers. Biomark Res 2022; 10:19. [PMID: 35395937 PMCID: PMC8994388 DOI: 10.1186/s40364-022-00366-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 03/20/2022] [Indexed: 12/21/2022] Open
Abstract
Heterogeneous nuclear ribonucleoproteins C (HnRNP C) is part of the hnRNP family of RNA-binding proteins. The relationship between hnRNP C and cancers has been extensively studied, and dysregulation of hnRNP C has been found in many cancers. According to existing public data, hnRNP C could promote the maturation of new heterogeneous nuclear RNAs (hnRNA s, also referred to as pre-mRNAs) into mRNAs and could stabilize mRNAs, controlling their translation. This paper reviews the regulation and dysregulation of hnRNP C in cancers. It interacts with some cancer genes and other biological molecules, such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and double-stranded RNAs (dsRNAs). Even directly binds to them. The effects of hnRNP C on biological processes such as alternative cleavage and polyadenylation (APA) and N6-methyladenosine (m6A) modification differ among cancers. Its main function is regulating stability and level of translation of cancer genes, and the hnRNP C is regarded as a candidate biomarker and might be valuable for prognosis evaluation.
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Affiliation(s)
- Liyi Mo
- The Hengyang Key Laboratory of Cellular Stress Biology, Institute of Cytology and Genetics, Hengyang Medical School, University of South China, Hengyang, 421001, Hunan, China
| | - Lijuan Meng
- Department of Ultrasonography, Second Affiliated Hospital, University of South China, Hengyang, 421001, Hunan, China
| | - Zhicheng Huang
- The Hengyang Key Laboratory of Cellular Stress Biology, Institute of Cytology and Genetics, Hengyang Medical School, University of South China, Hengyang, 421001, Hunan, China
| | - Lan Yi
- The Hengyang Key Laboratory of Cellular Stress Biology, Institute of Cytology and Genetics, Hengyang Medical School, University of South China, Hengyang, 421001, Hunan, China
| | - Nanyang Yang
- The Hengyang Key Laboratory of Cellular Stress Biology, Institute of Cytology and Genetics, Hengyang Medical School, University of South China, Hengyang, 421001, Hunan, China.
| | - Guoqing Li
- The Hengyang Key Laboratory of Cellular Stress Biology, Institute of Cytology and Genetics, Hengyang Medical School, University of South China, Hengyang, 421001, Hunan, China.
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11
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Namane A, Saveanu C. Composition and Dynamics of Protein Complexes Measured by Quantitative Mass Spectrometry of Affinity-Purified Samples. Methods Mol Biol 2022; 2477:225-236. [PMID: 35524120 DOI: 10.1007/978-1-0716-2257-5_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Multiple protein complexes are fundamental parts of living systems. Identification of the components of these complexes and characterization of the molecular mechanisms that allow their formation, function, and regulation can be done by affinity purification of proteins and associated factors followed by mass spectrometry of peptides. Speed and specificity for the isolation of complexes from whole cell extracts improved over time, together with the reliable identification and quantification of proteins by mass spectrometry. Relative quantification of proteins in such samples can now be done to characterize even relatively nonabundant complexes. We describe here our experience with proteins fused with the Z domain, derived from staphylococcal protein A, and IgG affinity purification for the analysis of protein complexes involved in RNA metabolism in the budding yeast Saccharomyces cerevisiae. We illustrate the use of enrichment calculations for proteins in purified samples as a way to robust identification of protein partners. While the protocols presented here are specific for yeast, their principles can be applied to the study of protein complexes in any other organism.
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Affiliation(s)
- Abdelkader Namane
- Génétique des Interactions Macromoléculaires (UMR3525-CNRS), Institut Pasteur, Paris, France
| | - Cosmin Saveanu
- Génétique des Interactions Macromoléculaires (UMR3525-CNRS), Institut Pasteur, Paris, France.
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12
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Lisy S, Rothamel K, Ascano M. RNA Binding Proteins as Pioneer Determinants of Infection: Protective, Proviral, or Both? Viruses 2021; 13:2172. [PMID: 34834978 PMCID: PMC8625426 DOI: 10.3390/v13112172] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 10/22/2021] [Accepted: 10/23/2021] [Indexed: 12/18/2022] Open
Abstract
As the first intracellular host factors that directly interact with the genomes of RNA viruses, RNA binding proteins (RBPs) have a profound impact on the outcome of an infection. Recent discoveries brought about by new methodologies have led to an unprecedented ability to peer into the earliest events between viral RNA and the RBPs that act upon them. These discoveries have sparked a re-evaluation of current paradigms surrounding RBPs and post-transcriptional gene regulation. Here, we highlight questions that have bloomed from the implementation of these novel approaches. Canonical RBPs can impact the fates of both cellular and viral RNA during infection, sometimes in conflicting ways. Noncanonical RBPs, some of which were first characterized via interactions with viral RNA, may encompass physiological roles beyond viral pathogenesis. We discuss how these RBPs might discriminate between an RNA of either cellular or viral origin and thus exert either pro- or antiviral effects-which is a particular challenge as viruses contain mechanisms to mimic molecular features of cellular RNA.
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Affiliation(s)
- Samantha Lisy
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; (S.L.); (K.R.)
| | - Katherine Rothamel
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; (S.L.); (K.R.)
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92037, USA
| | - Manuel Ascano
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; (S.L.); (K.R.)
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13
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Birladeanu AM, Rogalska M, Potiri M, Papadaki V, Andreadou M, Kontoyiannis DL, Lewis JD, Erpapazoglou Z, Kafasla P. The scaffold protein IQGAP1 links heat-induced stress signals to alternative splicing regulation in gastric cancer cells. Oncogene 2021; 40:5518-5532. [PMID: 34294847 DOI: 10.1038/s41388-021-01963-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 07/06/2021] [Accepted: 07/13/2021] [Indexed: 02/07/2023]
Abstract
In response to oncogenic signals, Alternative Splicing (AS) regulators such as SR and hnRNP proteins show altered expression levels, subnuclear distribution and/or post-translational modification status, but the link between signals and these changes remains unknown. Here, we report that a cytosolic scaffold protein, IQGAP1, performs this task in response to heat-induced signals. We show that in gastric cancer cells, a nuclear pool of IQGAP1 acts as a tethering module for a group of spliceosome components, including hnRNPM, a splicing factor critical for the response of the spliceosome to heat-shock. IQGAP1 controls hnRNPM's sumoylation, subnuclear localisation and the relevant response of the AS machinery to heat-induced stress. Genome-wide analyses reveal that IQGAP1 and hnRNPM co-regulate the AS of a cell cycle-related RNA regulon in gastric cancer cells, thus favouring the accelerated proliferation phenotype of gastric cancer cells. Overall, we reveal a missing link between stress signals and AS regulation.
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Affiliation(s)
- Andrada-Maria Birladeanu
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece
| | - Malgorzata Rogalska
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, Barcelona, 08003, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, 08003, Spain
| | - Myrto Potiri
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece
| | - Vasiliki Papadaki
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece
| | - Margarita Andreadou
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece
| | - Dimitris L Kontoyiannis
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece
- Department of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Joe D Lewis
- European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Zoi Erpapazoglou
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece
| | - Panagiota Kafasla
- Institute for Fundamental Biomedical Research, B.S.R.C. "Alexander Fleming", 34 Fleming st. 16672 Vari, Athens, Greece.
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14
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Thibault PA, Ganesan A, Kalyaanamoorthy S, Clarke JPWE, Salapa HE, Levin MC. hnRNP A/B Proteins: An Encyclopedic Assessment of Their Roles in Homeostasis and Disease. BIOLOGY 2021; 10:biology10080712. [PMID: 34439945 PMCID: PMC8389229 DOI: 10.3390/biology10080712] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/16/2021] [Accepted: 07/21/2021] [Indexed: 12/13/2022]
Abstract
The hnRNP A/B family of proteins is canonically central to cellular RNA metabolism, but due to their highly conserved nature, the functional differences between hnRNP A1, A2/B1, A0, and A3 are often overlooked. In this review, we explore and identify the shared and disparate homeostatic and disease-related functions of the hnRNP A/B family proteins, highlighting areas where the proteins have not been clearly differentiated. Herein, we provide a comprehensive assembly of the literature on these proteins. We find that there are critical gaps in our grasp of A/B proteins' alternative splice isoforms, structures, regulation, and tissue and cell-type-specific functions, and propose that future mechanistic research integrating multiple A/B proteins will significantly improve our understanding of how this essential protein family contributes to cell homeostasis and disease.
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Affiliation(s)
- Patricia A. Thibault
- Office of the Saskatchewan Multiple Sclerosis Clinical Research Chair, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; (P.A.T.); (J.-P.W.E.C.); (H.E.S.)
- Department of Medicine, Neurology Division, University of Saskatchewan, Saskatoon, SK S7N 0X8, Canada
| | - Aravindhan Ganesan
- ArGan’s Lab, School of Pharmacy, Faculty of Science, University of Waterloo, Waterloo, ON N2L 3G1, Canada;
| | - Subha Kalyaanamoorthy
- Department of Chemistry, Faculty of Science, University of Waterloo, Waterloo, ON N2L 3G1, Canada;
| | - Joseph-Patrick W. E. Clarke
- Office of the Saskatchewan Multiple Sclerosis Clinical Research Chair, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; (P.A.T.); (J.-P.W.E.C.); (H.E.S.)
- Department of Health Sciences, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada
| | - Hannah E. Salapa
- Office of the Saskatchewan Multiple Sclerosis Clinical Research Chair, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; (P.A.T.); (J.-P.W.E.C.); (H.E.S.)
- Department of Medicine, Neurology Division, University of Saskatchewan, Saskatoon, SK S7N 0X8, Canada
| | - Michael C. Levin
- Office of the Saskatchewan Multiple Sclerosis Clinical Research Chair, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; (P.A.T.); (J.-P.W.E.C.); (H.E.S.)
- Department of Medicine, Neurology Division, University of Saskatchewan, Saskatoon, SK S7N 0X8, Canada
- Department of Health Sciences, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada
- Correspondence:
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15
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So BR, Di C, Cai Z, Venters CC, Guo J, Oh JM, Arai C, Dreyfuss G. A Complex of U1 snRNP with Cleavage and Polyadenylation Factors Controls Telescripting, Regulating mRNA Transcription in Human Cells. Mol Cell 2019; 76:590-599.e4. [PMID: 31522989 DOI: 10.1016/j.molcel.2019.08.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/25/2019] [Accepted: 08/02/2019] [Indexed: 11/27/2022]
Abstract
Full-length transcription in the majority of human genes depends on U1 snRNP (U1) to co-transcriptionally suppress transcription-terminating premature 3' end cleavage and polyadenylation (PCPA) from cryptic polyadenylation signals (PASs) in introns. However, the mechanism of this U1 activity, termed telescripting, is unknown. Here, we captured a complex, comprising U1 and CPA factors (U1-CPAFs), that binds intronic PASs and suppresses PCPA. U1-CPAFs are distinct from U1-spliceosomal complexes; they include CPA's three main subunits, CFIm, CPSF, and CstF; lack essential splicing factors; and associate with transcription elongation and mRNA export complexes. Telescripting requires U1:pre-mRNA base-pairing, which can be disrupted by U1 antisense oligonucleotide (U1 AMO), triggering PCPA. U1 AMO remodels U1-CPAFs, revealing changes, including recruitment of CPA-stimulating factors, that explain U1-CPAFs' switch from repressive to activated states. Our findings outline this U1 telescripting mechanism and demonstrate U1's unique role as central regulator of pre-mRNA processing and transcription.
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Affiliation(s)
- Byung Ran So
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Chao Di
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Zhiqiang Cai
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Christopher C Venters
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Jiannan Guo
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Jung-Min Oh
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Chie Arai
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
| | - Gideon Dreyfuss
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA.
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16
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A phylogenetically conserved hnRNP type A/B protein from squid brain. Neurosci Lett 2019; 696:219-224. [PMID: 30610890 DOI: 10.1016/j.neulet.2019.01.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 12/13/2018] [Accepted: 01/02/2019] [Indexed: 11/23/2022]
Abstract
Eukaryotic mRNA precursors are co-transcriptionally assembled into ribonucleoprotein complexes. Heterogeneous nuclear ribonucleoprotein (hnRNP) complexes are involved in mRNA translocation, stability, subcellular localization and regulation of mRNA translation. About 20 major classes of hnRNPs have been identified in mammals. In a previous work, we characterized a novel, strongly-basic, RNA-binding protein (p65) in presynaptic terminals of squid neurons presenting homology with human hnRNPA/B type proteins, likely involved in local mRNA processing. We have identified and sequenced two hnRNPA/B-like proteins associated with tissue purified squid p65: Protein 1 (36.3 kDa, IP 7.1) and Protein 2 (37.6 kDa, IP 8.9). In the present work we generated an in silico, tridimensional, structural model of squid hnRNPA/B-like Protein 2, which showed highly conserved secondary and tertiary structure of RNA recognition motifs with human hnRNPA1 protein, as well as illustrated the potential for squid Protein 2 stable homodimerization. This was supported by biophysical measurements of bacterially expressed, recombinant protein. In addition, we induced expression of squid hnRNPA/B-like Protein 2 in human neuroblastoma cells (SH-SY5Y) and observed an exclusively nuclear localization, which depended on an intact C-terminal amino acid sequence and which relocated to cytoplasm particles containing PABP when the cells were challenged with sorbitol, suggesting an involvement with stress granule function.
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17
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Ramanathan M, Porter DF, Khavari PA. Methods to study RNA-protein interactions. Nat Methods 2019; 16:225-234. [PMID: 30804549 PMCID: PMC6692137 DOI: 10.1038/s41592-019-0330-1] [Citation(s) in RCA: 235] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 01/28/2019] [Indexed: 12/26/2022]
Abstract
Noncoding RNA sequences, including long noncoding RNAs, small nucleolar RNAs, and untranslated mRNA regions, accomplish many of their diverse functions through direct interactions with RNA-binding proteins (RBPs). Recent efforts have identified hundreds of new RBPs that lack known RNA-binding domains, thus underscoring the complexity and diversity of RNA-protein complexes. Recent progress has expanded the number of methods for studying RNA-protein interactions in two general categories: approaches that characterize proteins bound to an RNA of interest (RNA-centric), and those that examine RNAs bound to a protein of interest (protein-centric). Each method has unique strengths and limitations, which makes it important to select optimal approaches for the biological question being addressed. Here we review methods for the study of RNA-protein interactions, with a focus on their suitability for specific applications.
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Affiliation(s)
- Muthukumar Ramanathan
- Program in Epithelial Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Douglas F Porter
- Program in Epithelial Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Paul A Khavari
- Program in Epithelial Biology, Stanford University School of Medicine, Stanford, CA, USA.
- Veterans Affairs Palo Alto Healthcare System, Palo Alto, CA, USA.
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18
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Scherrer K. Primary transcripts: From the discovery of RNA processing to current concepts of gene expression - Review. Exp Cell Res 2018; 373:1-33. [PMID: 30266658 DOI: 10.1016/j.yexcr.2018.09.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 09/12/2018] [Accepted: 09/17/2018] [Indexed: 12/15/2022]
Abstract
The main purpose of this review is to recall for investigators - and in particular students -, some of the early data and concepts in molecular genetics and biology that are rarely cited in the current literature and are thus invariably overlooked. There is a growing tendency among editors and reviewers to consider that only data produced in the last 10-20 years or so are pertinent. However this is not the case. In exact science, sound data and lucid interpretation never become obsolete, and even if forgotten, will resurface sooner or later. In the field of gene expression, covered in the present review, recent post-genomic data have indeed confirmed many of the earlier results and concepts developed in the mid-seventies, well before the start of the recombinant DNA revolution. Human brains and even the most powerful computers, have difficulty in handling and making sense of the overwhelming flow of data generated by recent high-throughput technologies. This was easier when low throughput, more integrative methods based on biochemistry and microscopy dominated biological research. Nowadays, the need for organising concepts is ever more important, otherwise the mass of available data can generate only "building ruins" - the bricks without an architect. Concepts such as pervasive transcription of genomes, large genomic domains, full domain transcripts (FDTs) up to 100 kb long, the prevalence of post-transcriptional events in regulating eukaryotic gene expression, and the 3D-genome architecture, were all developed and discussed before 1990, and are only now coming back into vogue. Thus, to review the impact of earlier concepts on later developments in the field, I will confront former and current data and ideas, including a discussion of old and new methods. Whenever useful, I shall first briefly report post-genomic developments before addressing former results and interpretations. Equally important, some of the terms often used sloppily in scientific discussions will be clearly defined. As a basis for the ensuing discussion, some of the issues and facts related to eukaryotic gene expression will first be introduced. In chapter 2 the evolution in perception of biology over the last 60 years and the impact of the recombinant DNA revolution will be considered. Then, in chapter 3 data and theory concerning the genome, gene expression and genetics will be reviewed. The experimental and theoretical definition of the gene will be discussed before considering the 3 different types of genetic information - the "Triad" - and the importance of post-transcriptional regulation of gene expression in the light of the recent finding that 90% of genomic DNA seems to be transcribed. Some previous attempts to provide a conceptual framework for these observations will be recalled, in particular the "Cascade Regulation Hypothesis" (CRH) developed in 1967-85, and the "Gene and Genon" concept proposed in 2007. A knowledge of the size of primary transcripts is of prime importance, both for experimental and theoretical reasons, since these molecules represent the primary units of the "RNA genome" on which most of the post-transcriptional regulation of gene expression occurs. In chapter 4, I will first discuss some current post-genomic topics before summarising the discovery of the high Mr-RNA transcripts, and the investigation of their processing spanning the last 50 years. Since even today, a consensus concerning the real form of primary transcripts in eukaryotic cells has not yet been reached, I will refer to the viral and specialized cellular models which helped early on to understand the mechanisms of RNA processing and differential splicing which operate in cells and tissues. As a well-studied example of expression and regulation of a specific cellular gene in relation to differentiation and pathology, I will discuss the early and recent work on expression of the globin genes in nucleated avian erythroblasts. An important concept is that the primary transcript not only embodies protein-coding information and regulation of its expression, but also the 3D-structure of the genomic DNA from which it was derived. The wealth of recent post-genomic data published in this field emphasises the importance of a fundamental principle of genome organisation and expression that has been overlooked for years even though it was already discussed in the 1970-80ties. These issues are addressed in chapter 5 which focuses on the involvement of the nuclear matrix and nuclear architecture in DNA and RNA biology. This section will make reference to the Unified Matrix Hypothesis (UMH), which was the first molecular model of the 3D organisation of DNA and RNA. The chapter on the "RNA-genome and peripheral memories" discusses experimental data on the ribonucleoprotein complexes containing pre-mRNA (pre-mRNPs) and mRNA (mRNPs) which are organised in nuclear and cytoplasmic spaces respectively. Finally, "Outlook " will enumerate currently unresolved questions in the field, and will propose some ideas that may encourage further investigation, and comprehension of available experimental data still in need of interpretation. In chapter 8, some propositions and paradigms basic to the authors own analysis are discussed. "In conclusion" the raison d'être of this review is recalled and positioned within the overall framework of scientific endeavour.
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Affiliation(s)
- Klaus Scherrer
- Institute Jacques Monod, CNRS, University Paris Diderot, Paris, France.
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19
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Volanakis A, Kamieniarz-Gdula K, Schlackow M, Proudfoot NJ. WNK1 kinase and the termination factor PCF11 connect nuclear mRNA export with transcription. Genes Dev 2017; 31:2175-2185. [PMID: 29196535 PMCID: PMC5749165 DOI: 10.1101/gad.303677.117] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 11/06/2017] [Indexed: 12/16/2022]
Abstract
In this study, Volankis et al. present evidence for a new connection between gene transcription and mRNA export. They show that the kinase WNK1 phosphorylates termination factor PCF11 on its RNA polymerase II CTD-interacting domain (CID) and suggest that WNK1 and the associated phosphorylation of the PCF11 CID act to promote transcript release from chromatin-associated Pol II, which facilitates mRNA export to the cytoplasm. Nuclear gene transcription is coordinated with transcript release from the chromatin template and messenger RNA (mRNA) export to the cytoplasm. Here we describe the role of nuclear-localized kinase WNK1 (with no lysine [K] 1) in the mammalian mRNA export pathway even though it was previously established as a critical regulator of ion homeostasis in the cytoplasm. Our data reveal that WNK1 phosphorylates the termination factor PCF11 on its RNA polymerase II (Pol II) C-terminal domain (CTD)-interacting domain (CID). Furthermore, phosphorylation of the PCF11 CID weakens its interaction with Pol II. We predict that WNK1 and the associated phosphorylation of the PCF11 CID act to promote transcript release from chromatin-associated Pol II. This in turn facilitates mRNA export to the cytoplasm.
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Affiliation(s)
- Adam Volanakis
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Kinga Kamieniarz-Gdula
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Margarita Schlackow
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Nick J Proudfoot
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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20
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SPSB1-mediated HnRNP A1 ubiquitylation regulates alternative splicing and cell migration in EGF signaling. Cell Res 2017; 27:540-558. [PMID: 28084329 DOI: 10.1038/cr.2017.7] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 12/06/2016] [Accepted: 12/09/2016] [Indexed: 12/31/2022] Open
Abstract
Extracellular signals have been shown to impact on alternative pre-mRNA splicing; however, the molecular mechanisms and biological significance of signal-induced splicing regulation remain largely unknown. Here, we report that epidermal growth factor (EGF) induces splicing changes through ubiquitylation of a well-known splicing regulator, hnRNP A1. EGF signaling upregulates an E3 ubiquitin (Ub) ligase adaptor, SPRY domain-containing SOCS box protein 1 (SPSB1), which recruits Elongin B/C-Cullin complexes to conjugate lysine 29-linked polyUb chains onto hnRNP A1. Importantly, SPSB1 and ubiquitylation of hnRNP A1 have a critical role in EGF-driven cell migration. Mechanistically, EGF-induced ubiquitylation of hnRNP A1 together with the activation of SR protein kinases (SRPKs) results in the upregulation of a Rac1 splicing isoform, Rac1b, to promote cell motility. These findings unravel a novel crosstalk between protein ubiquitylation and alternative splicing in EGF/EGF receptor signaling, and identify a new EGF/SPSB1/hnRNP A1/Rac1 axis in modulating cell migration, which may have important implications for cancer treatment.
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21
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Gruber AJ, Schmidt R, Gruber AR, Martin G, Ghosh S, Belmadani M, Keller W, Zavolan M. A comprehensive analysis of 3' end sequencing data sets reveals novel polyadenylation signals and the repressive role of heterogeneous ribonucleoprotein C on cleavage and polyadenylation. Genome Res 2016; 26:1145-59. [PMID: 27382025 PMCID: PMC4971764 DOI: 10.1101/gr.202432.115] [Citation(s) in RCA: 157] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 05/31/2016] [Indexed: 12/22/2022]
Abstract
Alternative polyadenylation (APA) is a general mechanism of transcript diversification in mammals, which has been recently linked to proliferative states and cancer. Different 3′ untranslated region (3′ UTR) isoforms interact with different RNA-binding proteins (RBPs), which modify the stability, translation, and subcellular localization of the corresponding transcripts. Although the heterogeneity of pre-mRNA 3′ end processing has been established with high-throughput approaches, the mechanisms that underlie systematic changes in 3′ UTR lengths remain to be characterized. Through a uniform analysis of a large number of 3′ end sequencing data sets, we have uncovered 18 signals, six of which are novel, whose positioning with respect to pre-mRNA cleavage sites indicates a role in pre-mRNA 3′ end processing in both mouse and human. With 3′ end sequencing we have demonstrated that the heterogeneous ribonucleoprotein C (HNRNPC), which binds the poly(U) motif whose frequency also peaks in the vicinity of polyadenylation (poly(A)) sites, has a genome-wide effect on poly(A) site usage. HNRNPC-regulated 3′ UTRs are enriched in ELAV-like RBP 1 (ELAVL1) binding sites and include those of the CD47 gene, which participate in the recently discovered mechanism of 3′ UTR–dependent protein localization (UDPL). Our study thus establishes an up-to-date, high-confidence catalog of 3′ end processing sites and poly(A) signals, and it uncovers an important role of HNRNPC in regulating 3′ end processing. It further suggests that U-rich elements mediate interactions with multiple RBPs that regulate different stages in a transcript's life cycle.
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Affiliation(s)
- Andreas J Gruber
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Ralf Schmidt
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Andreas R Gruber
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Georges Martin
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Souvik Ghosh
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Manuel Belmadani
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Walter Keller
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Mihaela Zavolan
- Computational and Systems Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
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22
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Cieniková Z, Jayne S, Damberger FF, Allain FHT, Maris C. Evidence for cooperative tandem binding of hnRNP C RRMs in mRNA processing. RNA (NEW YORK, N.Y.) 2015; 21:1931-42. [PMID: 26370582 PMCID: PMC4604433 DOI: 10.1261/rna.052373.115] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/21/2015] [Indexed: 05/20/2023]
Abstract
The human hnRNP C is a ubiquitous cellular protein involved in mRNA maturation. Recently, we have shown that this protein specifically recognizes uridine (U) pentamers through its single RNA recognition motif (RRM). However, a large fraction of natural RNA targets of hnRNP C consists of much longer contiguous uridine stretches. To understand how these extended sites are recognized, we studied the binding of the RRM to U-tracts of 8-11 bases. In vivo investigation of internal translation activation of unr (upstream of N-ras) mRNA indicates that the conservation of the entire hnRNP C binding site, UC(U)8, is required for hnRNP C-dependent IRES activation. The assays further suggest a synergistic interplay between hnRNP C monomers, dependent on the protein's ability to oligomerize. In vitro spectroscopic and thermodynamic analyses show that isolated RRMs bind to (U)11 oligomers as dimers. Structural modeling of a ternary double-RRM/RNA complex indicates additionally that two RRM copies can be accommodated on the canonical sequence UC(U)8. The proposed tandem RRM binding is in very good agreement with the transcriptome-wide recognition of extended U-tracts by full-length hnRNP C, which displays a cross-linking pattern consistent with a positively cooperative RRM dimer binding model.
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Affiliation(s)
- Zuzana Cieniková
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
| | - Sandrine Jayne
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
| | - Fred Franz Damberger
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
| | - Frédéric Hai-Trieu Allain
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
| | - Christophe Maris
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
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23
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Cieniková Z, Damberger FF, Hall J, Allain FHT, Maris C. Structural and mechanistic insights into poly(uridine) tract recognition by the hnRNP C RNA recognition motif. J Am Chem Soc 2014; 136:14536-44. [PMID: 25216038 DOI: 10.1021/ja507690d] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
HnRNP C is a ubiquitous RNA regulatory factor and the principal constituent of the nuclear hnRNP core particle. The protein contains one amino-terminal RNA recognition motif (RRM) known to bind uridine (U)-rich sequences. This work provides a molecular and mechanistic understanding of this interaction. We solved the solution structures of the RRM in complex with poly(U) oligomers of five and seven nucleotides. The five binding pockets of RRM recognize uridines with an unusual 5'-to-3' gradient of base selectivity. The target recognition is therefore strongly sensitive to base clustering, explaining the preference for contiguous uridine tracts. Using a novel approach integrating the structurally derived recognition consensus of the RRM with a thermodynamic description of its multi-register binding, we modeled the saturation of cellular uridine tracts by this protein. The binding pattern is remarkably consistent with the experimentally observed transcriptome-wide cross-link distribution of the full-length hnRNP C on short uridine tracts. This result re-establishes the RRM as the primary RNA-binding domain of the hnRNP C tetramer and provides a proof of concept for interpreting high-throughput interaction data using structural approaches.
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Affiliation(s)
- Zuzana Cieniková
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich , 8093 Zürich, Switzerland
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The RNA-binding protein repertoire of embryonic stem cells. Nat Struct Mol Biol 2013; 20:1122-30. [PMID: 23912277 DOI: 10.1038/nsmb.2638] [Citation(s) in RCA: 385] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 06/19/2013] [Indexed: 12/20/2022]
Abstract
RNA-binding proteins (RBPs) have essential roles in RNA-mediated gene regulation, and yet annotation of RBPs is limited mainly to those with known RNA-binding domains. To systematically identify the RBPs of embryonic stem cells (ESCs), we here employ interactome capture, which combines UV cross-linking of RBP to RNA in living cells, oligo(dT) capture and MS. From mouse ESCs (mESCs), we have defined 555 proteins constituting the mESC mRNA interactome, including 283 proteins not previously annotated as RBPs. Of these, 68 new RBP candidates are highly expressed in ESCs compared to differentiated cells, implicating a role in stem-cell physiology. Two well-known E3 ubiquitin ligases, Trim25 (also called Efp) and Trim71 (also called Lin41), are validated as RBPs, revealing a potential link between RNA biology and protein-modification pathways. Our study confirms and expands the atlas of RBPs, providing a useful resource for the study of the RNA-RBP network in stem cells.
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Westmark CJ, Malter JS. The regulation of AβPP expression by RNA-binding proteins. Ageing Res Rev 2012; 11:450-9. [PMID: 22504584 DOI: 10.1016/j.arr.2012.03.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 03/13/2012] [Accepted: 03/28/2012] [Indexed: 12/29/2022]
Abstract
Amyloid β-protein precursor (AβPP) is cleaved by β- and γ-secretases to liberate amyloid beta (Aβ), the predominant protein found in the senile plaques associated with Alzheimer's disease (AD) and Down syndrome (Masters et al., 1985). Intense investigation by the scientific community has centered on understanding the molecular pathways that underlie the production and accumulation of Aβ Therapeutics that reduce the levels of this tenacious, plaque-promoting peptide may reduce the ongoing neural dysfunction and neuronal degeneration that occurs so profoundly in AD. AβPP and Aβ production are highly complex and involve still to be elucidated combinations of transcriptional, post-transcriptional, translational and post-translational events that mediate the production, processing and clearance of these proteins. Research in our laboratory for the past two decades has focused on the role of RNA binding proteins (RBPs) in mediating the post-transcriptional as well as translational regulation of APP messenger RNA (mRNA). This review article summarizes our findings, as well as those from other laboratories, describing the identification of regulatory RBPs, where and under what conditions they interact with APP mRNA and how those interactions control AβPP and Aβ synthesis.
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Affiliation(s)
- Cara J Westmark
- University of Wisconsin, Waisman Center for Developmental Disabilities, 1500 Highland Avenue, Madison, WI 53705, USA.
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The mRNA-bound proteome and its global occupancy profile on protein-coding transcripts. Mol Cell 2012; 46:674-90. [PMID: 22681889 DOI: 10.1016/j.molcel.2012.05.021] [Citation(s) in RCA: 934] [Impact Index Per Article: 71.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 05/14/2012] [Accepted: 05/17/2012] [Indexed: 01/17/2023]
Abstract
Protein-RNA interactions are fundamental to core biological processes, such as mRNA splicing, localization, degradation, and translation. We developed a photoreactive nucleotide-enhanced UV crosslinking and oligo(dT) purification approach to identify the mRNA-bound proteome using quantitative proteomics and to display the protein occupancy on mRNA transcripts by next-generation sequencing. Application to a human embryonic kidney cell line identified close to 800 proteins. To our knowledge, nearly one-third were not previously annotated as RNA binding, and about 15% were not predictable by computational methods to interact with RNA. Protein occupancy profiling provides a transcriptome-wide catalog of potential cis-regulatory regions on mammalian mRNAs and showed that large stretches in 3' UTRs can be contacted by the mRNA-bound proteome, with numerous putative binding sites in regions harboring disease-associated nucleotide polymorphisms. Our observations indicate the presence of a large number of mRNA binders with diverse molecular functions participating in combinatorial posttranscriptional gene-expression networks.
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Padmanabhan K, Robles MS, Westerling T, Weitz CJ. Feedback regulation of transcriptional termination by the mammalian circadian clock PERIOD complex. Science 2012; 337:599-602. [PMID: 22767893 DOI: 10.1126/science.1221592] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Eukaryotic circadian clocks are built on transcriptional feedback loops. In mammals, the PERIOD (PER) and CRYPTOCHROME (CRY) proteins accumulate, form a large nuclear complex (PER complex), and repress their own transcription. We found that mouse PER complexes included RNA helicases DDX5 and DHX9, active RNA polymerase II large subunit, Per and Cry pre-mRNAs, and SETX, a helicase that promotes transcriptional termination. During circadian negative feedback, RNA polymerase II accumulated near termination sites on Per and Cry genes but not on control genes. Recruitment of PER complexes to the elongating polymerase at Per and Cry termination sites inhibited SETX action, impeding RNA polymerase II release and thereby repressing transcriptional reinitiation. Circadian clock negative feedback thus includes direct control of transcriptional termination.
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Affiliation(s)
- Kiran Padmanabhan
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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A fraction of the transcription factor TAF15 participates in interactions with a subset of the spliceosomal U1 snRNP complex. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1812-24. [PMID: 22019700 DOI: 10.1016/j.bbapap.2011.09.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 09/23/2011] [Accepted: 09/26/2011] [Indexed: 10/16/2022]
Abstract
RNA/ssDNA-binding proteins comprise an emerging class of multifunctional proteins with an anticipated role in coupling transcription with RNA processing. We focused here on the highly related transcription factors of the TET sub-class: TLS/FUS, EWS and in particular the least studied member TAF15. An extensive array of immunoprecipitation studies on differentially extracted HeLa nuclei revealed the specific association of TAF15 with the spliceosomal U1 snRNP complex, as deduced by the co-precipitating U1 snRNA, U1-70K and Sm proteins. Additionally, application of anti-U1 RNP autoantibodies identified TAF15 in the immunoprecipitates. Minor fractions of nuclear TAF15 and U1 snRNP were involved in this association. Pull-down assays using recombinant TAF15 and U1 snRNP-specific proteins (U1-70K, U1A and U1C) provided in vitro evidence for a direct protein-protein interaction between TAF15 and U1C, which required the N-terminal domain of TAF15. The ability of TAF15 to directly contact RNA, most likely RNA pol II transcripts, was supported by in vivo UV cross-linking studies in the presence of α-amanitin. By all findings, the existence of a functionally discrete subset of U1 snRNP in association with TAF15 was suggested and provided further support for the involvement of U1 snRNP components in early steps of coordinated gene expression.
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Busch A, Hertel KJ. Evolution of SR protein and hnRNP splicing regulatory factors. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 3:1-12. [PMID: 21898828 DOI: 10.1002/wrna.100] [Citation(s) in RCA: 285] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The splicing of pre-mRNAs is an essential step of gene expression in eukaryotes. Introns are removed from split genes through the activities of the spliceosome, a large ribonuclear machine that is conserved throughout the eukaryotic lineage. While unicellular eukaryotes are characterized by less complex splicing, pre-mRNA splicing of multicellular organisms is often associated with extensive alternative splicing that significantly enriches their proteome. The alternative selection of splice sites and exons permits multicellular organisms to modulate gene expression patterns in a cell type-specific fashion, thus contributing to their functional diversification. Alternative splicing is a regulated process that is mainly influenced by the activities of splicing regulators, such as SR proteins or hnRNPs. These modular factors have evolved from a common ancestor through gene duplication events to a diverse group of splicing regulators that mediate exon recognition through their sequence-specific binding to pre-mRNAs. Given the strong correlations between intron expansion, the complexity of pre-mRNA splicing, and the emergence of splicing regulators, it is argued that the increased presence of SR and hnRNP proteins promoted the evolution of alternative splicing through relaxation of the sequence requirements of splice junctions.
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Affiliation(s)
- Anke Busch
- Department of Microbiology and Molecular Genetics, University of California, Irvine, Irvine, CA 92697-4025, USA
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Expression and mutation analysis of heterogeneous nuclear ribonucleoprotein G in human oral cancer. Oral Oncol 2011; 47:1011-6. [PMID: 21840245 DOI: 10.1016/j.oraloncology.2011.07.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 06/27/2011] [Accepted: 07/05/2011] [Indexed: 11/24/2022]
Abstract
We previously reported that wild type (wt) hnRNP G exhibited tumor suppressive activity in human oral squamous cell carcinoma (HOSCC) cell lines lacking hnRNP G. Wt hnRNP G markedly inhibited the proliferation capacity, anchorage independency and in vivo tumorigenicity of HOSCC cells and notably enhanced the DNA repair capabilities of these cells. In the present study, we studied the genetic and expression states of hnRNP G in normal, premalignant and malignant human oral tissues to further understand the relationship between the hnRNP G alterations and the development of human oral cancer. To correlate the cancer development and the level of hnRNP G expression, we performed an immunohistochemistry staining of hnRNP G in normal, premalignant and malignant human oral tissues. Moreover, we examined the entire coding regions of hnRNP G from selected samples to understand the cause of the alterations of the gene expression. The expression of hnRNP G was notably decreased or completely abolished in 80% of premalignant-dysplastic and malignant oral epithelial tissues, whereas 100% of normal and 90% of hyperplastic non-dysplastic epithelium showed high level of hnRNP G in the nucleus of the basal cell layers. Approximately 80% of HOSCC lacking the expression of hnRNP G showed genetic alteration in hnRNP G, i.e., point mutation and exonic deletion. This study suggest that genetic alterations and aberrant expression of hnRNP G occurring during oral carcinogenesis might be useful markers for the early detection of human oral cancer.
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Zheng R, Shen Z, Tripathi V, Xuan Z, Freier SM, Bennett CF, Prasanth SG, Prasanth KV. Polypurine-repeat-containing RNAs: a novel class of long non-coding RNA in mammalian cells. J Cell Sci 2010; 123:3734-44. [PMID: 20940252 DOI: 10.1242/jcs.070466] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In higher eukaryotic cells, long non-protein-coding RNAs (lncRNAs) have been implicated in a wide array of cellular functions. Cell- or tissue-specific expression of lncRNA genes encoded in the mammalian genome is thought to contribute to the complex gene networks needed to regulate cellular function. Here, we have identified a novel species of polypurine triplet repeat-rich lncRNAs, designated as GAA repeat-containing RNAs (GRC-RNAs), that localize to numerous punctate foci in the mammalian interphase nuclei. GRC-RNAs consist of a heterogeneous population of RNAs, ranging in size from ~1.5 kb to ~4 kb and localize to subnuclear domains, several of which associate with GAA.TTC-repeat-containing genomic regions. GRC-RNAs are components of the nuclear matrix and interact with various nuclear matrix-associated proteins. In mitotic cells, GRC-RNAs form distinct cytoplasmic foci and, in telophase and G1 cells, localize to the midbody, a structure involved in accurate cell division. Differentiation of tissue culture cells leads to a decrease in the number of GRC-RNA nuclear foci, albeit with an increase in size as compared with proliferating cells. Conversely, the number of GRC-RNA foci increases during cellular transformation. We propose that nuclear GRC-RNAs represent a novel family of mammalian lncRNAs that might play crucial roles in the cell nucleus.
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Affiliation(s)
- Ruiping Zheng
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA
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Nishimura AL, Zupunski V, Troakes C, Kathe C, Fratta P, Howell M, Gallo JM, Hortobágyi T, Shaw CE, Rogelj B. Nuclear import impairment causes cytoplasmic trans-activation response DNA-binding protein accumulation and is associated with frontotemporal lobar degeneration. Brain 2010; 133:1763-71. [PMID: 20472655 DOI: 10.1093/brain/awq111] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Trans-activation response DNA-binding protein (TDP-43) accumulation is the major component of ubiquitinated protein inclusions found in patients with amyotrophic lateral sclerosis, and frontotemporal lobar degeneration with TDP-43 positive ubiquitinated inclusions, recently relabelled the 'TDP-43 proteinopathies'. TDP-43 is predominantly located in the nucleus, however, in disease it mislocalizes to the cytoplasm where it aggregates to form hallmark pathological inclusions. The identification of TDP-43 mutations in familial and sporadic amyotrophic lateral sclerosis cases confirms its pathogenic role; but it is wild-type TDP-43 that is deposited in the vast majority of TDP-43 proteinopathies, implicating other unknown factors for its mislocalization and aggregation. One such mechanism may be defective nuclear import of TDP-43 protein, as a disruption of its nuclear localization signal leads to mislocalization and aggregation of TDP-43 in the cytoplasm. In order to explore the factors that regulate the nuclear import of TDP-43, we used a small interfering RNA library to silence 82 proteins involved in nuclear transport and found that knockdowns of karyopherin-beta1 and cellular apoptosis susceptibility protein resulted in marked cytoplasmic accumulation of TDP-43. In glutathione S-transferase pull-down assays, TDP-43 bound to karyopherin-alphas, thereby confirming the classical nuclear import pathway for the import of TDP-43. Analysis of the expression of chosen nuclear import factors in post-mortem brain samples from patients with TDP-43 positive frontotemporal lobar degeneration, and spinal cord samples from patients with amyotrophic lateral sclerosis, revealed a considerable reduction in expression of cellular apoptosis susceptibility protein in frontotemporal lobar degeneration. We propose that cellular apoptosis susceptibility protein associated defective nuclear transport may play a mechanistic role in the pathogenesis of the TDP-43 positive frontotemporal lobar degeneration.
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Affiliation(s)
- Agnes L Nishimura
- Medical Research Council (MRC) Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, London, SE5 8AF, UK
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Yong J, Kasim M, Bachorik JL, Wan L, Dreyfuss G. Gemin5 delivers snRNA precursors to the SMN complex for snRNP biogenesis. Mol Cell 2010; 38:551-62. [PMID: 20513430 PMCID: PMC2901871 DOI: 10.1016/j.molcel.2010.03.014] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 02/16/2010] [Accepted: 03/26/2010] [Indexed: 12/26/2022]
Abstract
The SMN complex assembles Sm cores on snRNAs, a key step in the biogenesis of snRNPs, the spliceosome's major components. Here, using SMN complex inhibitors identified by high-throughput screening and a ribo-proteomic strategy on formaldehyde crosslinked RNPs, we dissected this pathway in cells. We show that protein synthesis inhibition impairs the SMN complex, revealing discrete SMN and Gemin subunits and accumulating an snRNA precursor (pre-snRNA)-Gemin5 intermediate. By high-throughput sequencing of this transient intermediate's RNAs, we discovered the previously undetectable precursors of all the snRNAs and identified their Gemin5-binding sites. We demonstrate that pre-snRNA 3' sequences function to enhance snRNP biogenesis. The SMN complex is also inhibited by oxidation, and we show that it stalls an inventory-complete SMN complex containing pre-snRNAs. We propose a stepwise pathway of SMN complex formation and snRNP biogenesis, highlighting Gemin5's function in delivering pre-snRNAs as substrates for Sm core assembly and processing.
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Affiliation(s)
| | | | - Jennifer L. Bachorik
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148
| | - Lili Wan
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148
| | - Gideon Dreyfuss
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148
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Koryllou A, Patrinou-Georgoula M, Troungos C, Pletsa V. Cell death induced by N-methyl-N-nitrosourea, a model S(N)1 methylating agent, in two lung cancer cell lines of human origin. Apoptosis 2009; 14:1121-33. [PMID: 19634013 DOI: 10.1007/s10495-009-0379-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
New therapeutic approaches are needed for lung cancer, the leading cause of cancer death. Methylating agents constitute a widely used class of anticancer drugs, the effect of which on human non small cell lung cancer (NSCLC) has not been adequately studied. N-methyl-N-nitrosourea (MNU), a model S(N)1 methylating agent, induced cell death through a distinct mechanism in two human NSCLC cell lines studied, A549(p53(wt)) and H157(p53(null)). In A549(p53(wt)), MNU induced G2/M arrest, accompanied by cdc25A degradation, hnRNP B1 induction, hnRNP C1/C2 downregulation. Non-apoptotic cell death was confirmed by the lack of increase in the sub-G1 DNA content, Poly (ADP-ribose) polymerase cleavage and caspase-3, -7 activation. In H157(p53(null)), MNU induced apoptotic cell death, confirmed by cytofluorometry of DNA content and immunodetection of apoptotic markers, accompanied by overexpression of hnRNP B1 and C1/C2. Thus, the mechanism of the cell death induced by S(N)1 methylating agents is cell type-dependent and must be assessed prior treatment.
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Affiliation(s)
- Angeliki Koryllou
- Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, Athens, Greece
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Ma KW, Au SWN, Waye MMY. Over-expression of SUMO-1 induces the up-regulation of heterogeneous nuclear ribonucleoprotein A2/B1 isoform B1 (hnRNP A2/B1 isoform B1) and uracil DNA glycosylase (UDG) in hepG2 cells. Cell Biochem Funct 2009; 27:228-37. [PMID: 19384898 DOI: 10.1002/cbf.1562] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Sumoylation is one of the post-translational modifications that governs many cellular activities, including subcellular localization targeting, protein-protein interaction, and transcriptional activity regulation. SUMO E3 ligases are responsible for substrate specificity determination in which PIAS is the largest E3 family that consists of five members in human; they are PIAS1, PIAS3, PIASx alpha, PIASx beta, and PIASy. Several studies showed that all these PIAS genes are highly expressed in testis but only a few reports have discussed their expression pattern in other tissues. Though liver is a multifunctional organ and one would expect to find regulation of cellular functions by sumoylation, the identified sumoylation substrates are scarce and few of them correlate with liver cancer. In this report, we have found that PIASx alpha, PIASx beta, and PIASy are highly expressed in liver as well as testis by tissue distribution studies. We thus aimed to identify any SUMO-1 related proteins in liver cancer cells by two-dimensional gel electrophoresis and mass spectrometry. Two up-regulated proteins, heterogeneous nuclear ribonucleoprotein A2/B1 isoform B1 (hnRNP A2/B1 isoform B1) and uracil DNA glycosylase (UDG), have been identified in the EGFP-SUMO-1 over-expressing HepG2 cells. The up-regulation is suggested to be mediated via changes at the translational level or protection from degradation by western blotting and RT-PCR.
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Affiliation(s)
- Kit Wan Ma
- The Croucher Laboratory for Human Genomics, MMW Bldg., the Chinese University of Hong Kong, Shatin, NT, Hong Kong, SAR, China
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36
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Comparative qualitative and quantitative analysis of scleroderma (systemic sclerosis) serologic immunoassays. J Autoimmun 2008; 31:166-74. [DOI: 10.1016/j.jaut.2008.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 06/30/2008] [Accepted: 07/01/2008] [Indexed: 11/23/2022]
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37
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Han S, Choi M. Human ribosomal protein L18a interacts with hnRNP E1. Anim Cells Syst (Seoul) 2008. [DOI: 10.1080/19768354.2008.9647167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Heterogeneous nuclear ribonucleoprotein D/AUF1 interacts with heterogeneous nuclear ribonucleoprotein L. J Biosci 2007; 32:1263-72. [DOI: 10.1007/s12038-007-0135-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Gama-Carvalho M, Barbosa-Morais NL, Brodsky AS, Silver PA, Carmo-Fonseca M. Genome-wide identification of functionally distinct subsets of cellular mRNAs associated with two nucleocytoplasmic-shuttling mammalian splicing factors. Genome Biol 2007; 7:R113. [PMID: 17137510 PMCID: PMC1794580 DOI: 10.1186/gb-2006-7-11-r113] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 10/18/2006] [Accepted: 11/30/2006] [Indexed: 11/19/2022] Open
Abstract
A genome wide identification of mRNAs that were associated with the splicing factor subunit U2AF65 suggests that U2AF65 associates with specific subsets of spliced mRNAs and may be involved in novel cellular functions in addition to splicing. Background Pre-mRNA splicing is an essential step in gene expression that occurs co-transcriptionally in the cell nucleus, involving a large number of RNA binding protein splicing factors, in addition to core spliceosome components. Several of these proteins are required for the recognition of intronic sequence elements, transiently associating with the primary transcript during splicing. Some protein splicing factors, such as the U2 small nuclear RNP auxiliary factor (U2AF), are known to be exported to the cytoplasm, despite being implicated solely in nuclear functions. This observation raises the question of whether U2AF associates with mature mRNA-ribonucleoprotein particles in transit to the cytoplasm, participating in additional cellular functions. Results Here we report the identification of RNAs immunoprecipitated by a monoclonal antibody specific for the U2AF 65 kDa subunit (U2AF65) and demonstrate its association with spliced mRNAs. For comparison, we analyzed mRNAs associated with the polypyrimidine tract binding protein (PTB), a splicing factor that also binds to intronic pyrimidine-rich sequences but additionally participates in mRNA localization, stability, and translation. Our results show that 10% of cellular mRNAs expressed in HeLa cells associate differentially with U2AF65 and PTB. Among U2AF65-associated mRNAs there is a predominance of transcription factors and cell cycle regulators, whereas PTB-associated transcripts are enriched in mRNA species that encode proteins implicated in intracellular transport, vesicle trafficking, and apoptosis. Conclusion Our results show that U2AF65 associates with specific subsets of spliced mRNAs, strongly suggesting that it is involved in novel cellular functions in addition to splicing.
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Affiliation(s)
- Margarida Gama-Carvalho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
| | - Nuno L Barbosa-Morais
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
- Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Hills Road, Cambridge CB2 0XZ, UK
| | - Alexander S Brodsky
- Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Alpert 536, Boston, MA 02115, USA
- Department of Molecular Biology, Cell Biology and Biochemistry and Center for Genomics & Proteomics, Brown University, 69 Brown Street, Providence, Rhode Island 02912, USA
| | - Pamela A Silver
- Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Alpert 536, Boston, MA 02115, USA
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
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Martinez-Contreras R, Cloutier P, Shkreta L, Fisette JF, Revil T, Chabot B. hnRNP proteins and splicing control. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 623:123-47. [PMID: 18380344 DOI: 10.1007/978-0-387-77374-2_8] [Citation(s) in RCA: 289] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Proteins of the heterogeneous nuclear ribonucleoparticles (hnRNP) family form a structurally diverse group of RNA binding proteins implicated in various functions in metazoans. Here we discuss recent advances supporting a role for these proteins in precursor-messenger RNA (pre-mRNA) splicing. Heterogeneous nuclear RNP proteins can repress splicing by directly antagonizing the recognition of splice sites, or can interfere with the binding of proteins bound to enhancers. Recently, hnRNP proteins have been shown to hinder communication between factors bound to different splice sites. Conversely, several reports have described a positive role for some hnRNP proteins in pre-mRNA splicing. Moreover, cooperative interactions between bound hnRNP proteins may encourage splicing between specific pairs of splice sites while simultaneously hampering other combinations. Thus, hnRNP proteins utilize a variety of strategies to control splice site selection in a manner that is important for both alternative and constitutive pre-mRNA splicing.
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Matunis MJ. Isolation and fractionation of rat liver nuclear envelopes and nuclear pore complexes. Methods 2006; 39:277-83. [PMID: 16870471 DOI: 10.1016/j.ymeth.2006.06.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Accepted: 06/13/2006] [Indexed: 01/08/2023] Open
Abstract
The nuclear envelope is a double lipid bilayer that physically separates the functions of the nucleus and the cytoplasm of eukaryotic cells. Regulated transport of molecules between the nucleus and the cytoplasm is essential for normal cell metabolism and is mediated by large protein complexes, termed nuclear pore complexes (NPCs), which span the inner and outer membranes of the nuclear envelope. Significant progress has been made in the past 10 years in identifying the protein composition of NPCs and the basic molecular mechanisms by which these complexes facilitate the selective exchange of molecules between the nucleus and the cytoplasm. However, many fundamentally important questions about the functions of NPCs, the specific functions of individual NPC-associated proteins, and the assembly and disassembly of NPCs, remain unanswered. This review describes approaches for isolating and characterizing nuclear envelopes and NPC-associated proteins from mammalian cells. It is anticipated that these procedures can be used as a starting point for further molecular and biochemical analysis of the mammalian nuclear envelope, NPCs, and NPC-associated proteins.
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Affiliation(s)
- Michael J Matunis
- Johns Hopkins University, Bloomberg School of Public Health, Department of Biochemistry and Molecular Biology, Baltimore MD 21205, USA.
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Carpenter B, McKay M, Dundas SR, Lawrie LC, Telfer C, Murray GI. Heterogeneous nuclear ribonucleoprotein K is over expressed, aberrantly localised and is associated with poor prognosis in colorectal cancer. Br J Cancer 2006; 95:921-7. [PMID: 16953238 PMCID: PMC2360539 DOI: 10.1038/sj.bjc.6603349] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Heterogeneous ribonucleoprotein K (hnRNP K) is a member of the hnRNP family which has several different cellular roles including transcription, mRNA shuttling, RNA editing and translation. Several reports implicate hnRNP K having a role in tumorigenesis, for instance hnRNP K increases transcription of the oncogene c-myc and hnRNP K expression is regulated by the p53/MDM 2 pathway. In this study comparing normal colon to colorectal cancer by proteomics, hnRNP K was identified as being overexpressed in this type of cancer. Immunohistochemistry with a monoclonal antibody to hnRNP K (which we developed) on colorectal cancer tissue microarray, confirmed that hnRNP K was overexpressed in colorectal cancer (P<0.001) and also showed that hnRNP K had an aberrant subcellular localisation in cancer cells. In normal colon hnRNP K was exclusively nuclear whereas in colorectal cancer the protein localised both in the cytoplasm and the nucleus. There were significant increases in both nuclear (P=0.007) and cytoplasmic (P=0.001) expression of hnRNP K in Dukes C tumours compared with early stage tumours. In Dukes C patient's good survival was associated with increased hnRNP K nuclear expression (P=0.0093). To elaborate on the recent observation that hnRNP K is regulated by p53, the expression profiles of these two proteins were also analysed. There was no correlation between hnRNP K and p53 expression, however, patients who presented tumours that were positive for hnRNP K and p53 had a poorer survival outcome (P=0.045).
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Affiliation(s)
- B Carpenter
- Department of Pathology, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
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Carpenter B, MacKay C, Alnabulsi A, MacKay M, Telfer C, Melvin WT, Murray GI. The roles of heterogeneous nuclear ribonucleoproteins in tumour development and progression. Biochim Biophys Acta Rev Cancer 2005; 1765:85-100. [PMID: 16378690 DOI: 10.1016/j.bbcan.2005.10.002] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Revised: 10/18/2005] [Accepted: 10/19/2005] [Indexed: 10/25/2022]
Abstract
The heterogeneous nuclear ribonucleoproteins (hnRNP) are a family of proteins which share common structural domains, and extensive research has shown that they have central roles in DNA repair, telomere biogenesis, cell signaling and in regulating gene expression at both transcriptional and translational levels. Through these key cellular functions, individual hnRNPs have a variety of potential roles in tumour development and progression including the inhibition of apoptosis, angiogenesis and cell invasion. The aims of this review are to provide an overview of the multi functional roles of the hnRNPs, and how such roles implicate this family as regulators of tumour development. The different stages of tumour development that are potentially regulated by the hnRNPs along with their aberrant expression profiles in tumour tissues will also be discussed.
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Affiliation(s)
- Brian Carpenter
- Department of Pathology, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
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Vassileva MT, Matunis MJ. SUMO modification of heterogeneous nuclear ribonucleoproteins. Mol Cell Biol 2004; 24:3623-32. [PMID: 15082759 PMCID: PMC387737 DOI: 10.1128/mcb.24.9.3623-3632.2004] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2003] [Revised: 09/30/2003] [Accepted: 02/05/2004] [Indexed: 11/20/2022] Open
Abstract
Small ubiquitin-related modifiers (SUMOs) are proteins that are posttranslationally conjugated to other cellular proteins, particularly those that localize and function in the nucleus. Enzymes regulating SUMO modification localize in part to nuclear pore complexes (NPCs), indicating that modification of some proteins may occur as they are translocated between the nucleus and the cytoplasm. Substrates that are regulated by SUMO modification at NPCs, however, have not been previously identified. Among the most abundant cargos transported through NPCs are the heterogeneous nuclear ribonucleoproteins (hnRNPs). HnRNPs are involved in various aspects of mRNA biogenesis, including regulation of pre-mRNA splicing and nuclear export. Here, we demonstrate that two subsets of hnRNPs, the hnRNP C and M proteins, are substrates for SUMO modification. We demonstrate that the hnRNP C proteins are modified by SUMO at a single lysine residue, K237, and that SUMO modification at this site decreases their binding to nucleic acids. We also show that Nup358, a SUMO E3 ligase associated with the cytoplasmic fibrils of NPCs, enhances the SUMO modification of the hnRNP C and M proteins. Based on our findings, we propose that SUMO modification of the hnRNP C and M proteins may occur at NPCs and facilitate the nucleocytoplasmic transport of mRNAs.
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Affiliation(s)
- Maria T Vassileva
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA
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Chan CC, Dostie J, Diem MD, Feng W, Mann M, Rappsilber J, Dreyfuss G. eIF4A3 is a novel component of the exon junction complex. RNA (NEW YORK, N.Y.) 2004; 10:200-9. [PMID: 14730019 PMCID: PMC1370532 DOI: 10.1261/rna.5230104] [Citation(s) in RCA: 211] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Accepted: 11/19/2003] [Indexed: 05/19/2023]
Abstract
The exon junction complex (EJC) is a protein complex that assembles near exon-exon junctions of mRNAs as a result of splicing. EJC proteins play important roles in postsplicing events including mRNA export, cytoplasmic localization, and nonsense-mediated decay. Recent evidence suggests that mRNA translation is also influenced by the splicing history of the transcript. Here we identify eIF4A3, a DEAD-box RNA helicase and a member of the eIF4A family of translation initiation factors, as a novel component of the EJC. We show that eIF4A3 associates preferentially with nuclear complexes containing the EJC proteins magoh and Y14. Furthermore, eIF4A3, but not the highly related eIF4A1 or eIF4A2, preferentially associates with spliced mRNA. In vitro splicing and mapping experiments demonstrate that eIF4A3 binds mRNAs at the position of the EJC. Using monoclonal antibodies, we show that eIF4A3 is found in the nucleus whereas eIF4A1 and eIF4A2 are found in the cytoplasm. Thus, eIF4A3 likely provides a splicing-dependent influence on the translation of mRNAs.
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Affiliation(s)
- Chia C Chan
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, USA
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Chkheidze AN, Liebhaber SA. A novel set of nuclear localization signals determine distributions of the alphaCP RNA-binding proteins. Mol Cell Biol 2003; 23:8405-15. [PMID: 14612387 PMCID: PMC262676 DOI: 10.1128/mcb.23.23.8405-8415.2003] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2003] [Revised: 07/22/2003] [Accepted: 08/29/2003] [Indexed: 11/20/2022] Open
Abstract
AlphaCPs comprise a subfamily of KH-domain-containing RNA-binding proteins with specificity for C-rich pyrimidine tracts. These proteins play pivotal roles in a broad spectrum of posttranscriptional events. The five major alphaCP isoforms are encoded by four dispersed loci. Each isoform contains three repeats of the RNA-binding KH domain (KH1, KH2, and KH3) but lacks other identifiable motifs. To explore the complexity of their respective functions, we examined the subcellular localization of each alphaCP isoform. Immunofluorescence studies revealed three distinct distributions: alphaCP1 and alphaCP2 are predominantly nuclear with specific enrichment of alphaCP1 in nuclear speckles, alphaCP3 and alphaCP4 are restricted to the cytoplasm, and alphaCP2-KL, an alphaCP2 splice variant, is present at significant levels in both the nucleus and the cytoplasm. We mapped nuclear localization signals (NLSs) for alphaCP isoforms. alphaCP2 contains two functionally independent NLS. Both NLSs appear to be novel and were mapped to a 9-amino-acid segment between KH2 and KH3 (NLS I) and to a 12-amino-acid segment within KH3 (NLS II). NLS I is conserved in alphaCP1, whereas NLS II is inactivated by two amino acid substitutions. Neither NLS is present in alphaCP3 or alphaCP4. Consistent with mapping studies, deletion of NLS I from alphaCP1 blocks its nuclear accumulation, whereas NLS I and NLS II must both be inactivated to block nuclear accumulation of alphaCP2. These data demonstrate an unexpected complexity in the compartmentalization of alphaCP isoforms and identify two novel NLS that play roles in their respective distributions. This complexity of alphaCP distribution is likely to contribute to the diverse functions mediated by this group of abundant RNA-binding proteins.
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Affiliation(s)
- Alexander N Chkheidze
- Departments of Genetics and Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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Pawlak MR, Banik-Maiti S, Pietenpol JA, Ruley HE. Protein arginine methyltransferase I: substrate specificity and role in hnRNP assembly. J Cell Biochem 2003; 87:394-407. [PMID: 12397599 DOI: 10.1002/jcb.10307] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Prmt1, the major protein arginine methyltransferase in mammalian cells, has been implicated in signal transduction, transcriptional control, and protein trafficking. In the present study, mouse embryonic stem cells homozygous for an essentially null mutation in the Prmt1 gene were used to examine Prmt1 activity and substrate specificity, which by several criteria appeared to be highly specific. First, other methyltransferases did not substitute for the loss of Prmt1 activity. Second, almost all proteins modified by recombinant Prmt1 in vitro were authentic substrates, i.e., proteins rendered hypomethylated by Prmt1 gene disruption. Finally, Prmt1 did not modify the substrates of other methyltransferases from cells treated with methyltransferase inhibitors. Recombinant proteins corresponding to two splice-variants, Prmt1(353) and Prmt1(371), methylated different, proteins in vitro, providing the first evidence for functional differences between the two isoforms. However, the differences in substrate specificity were lost by the addition of an N-terminal His(6) tag. Loss of Prmt1 activity (and hypomethylation of hnRNPs) has no obvious effect on the formation or composition of hnRNP complexes. Finally, methylation of the most abundant Prmt1 substrates appeared to be extensive and constitutive throughout the cell cycle, suggesting the modification does not modulate protein function under normal growth conditions.
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Affiliation(s)
- Maciej R Pawlak
- Department of Microbiology and Immunology, Room AA5206 MCN, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2363, USA
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Abstract
BACKGROUND Y14 is an RNA binding protein which is part of a multiprotein complex, the exon-exon junction complex (EJC), that assembles on the exon-exon junctions of mRNAs produced by splicing. The position-specific binding of Y14 persists on mRNAs after their export to the cytoplasm. Thus, Y14, together with its interacting proteins, has the capacity to communicate to the cytoplasm the processing history of the mRNA, including the position of the removed introns, information that is likely to be important for defining premature termination codons. How Y14 and other components of the EJC are removed from mRNAs into the cytoplasm has not been determined. RESULTS We show that Y14 but not another EJC component, Aly/REF, is present in polysome profile fractions containing one ribosome per mRNA. Using reporter constructs in an in vitro splicing/translation-coupled system, we show that Y14 remains associated with untranslated mRNAs but is removed from translationally active mRNAs. Importantly, mRNAs whose translation in vivo is prevented by the presence of strong secondary 5' UTR structure retain Y14 in the cytoplasm. CONCLUSIONS These findings indicate that Y14 remains associated with mRNAs in the cytoplasm until they are translated, and translation is required to remove Y14 from mRNAs. Thus, the process of translation removes the splicing-dependent EJC protein imprints, which most likely function in the surveillance of mRNAs to define premature termination codons and possibly also in modulating the translation activity of cytoplasmic mRNAs.
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Affiliation(s)
- Josée Dostie
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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Mili S, Shu HJ, Zhao Y, Piñol-Roma S. Distinct RNP complexes of shuttling hnRNP proteins with pre-mRNA and mRNA: candidate intermediates in formation and export of mRNA. Mol Cell Biol 2001; 21:7307-19. [PMID: 11585913 PMCID: PMC99905 DOI: 10.1128/mcb.21.21.7307-7319.2001] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2001] [Accepted: 07/30/2001] [Indexed: 11/20/2022] Open
Abstract
Nascent pre-mRNAs associate with hnRNP proteins in hnRNP complexes, the natural substrates for mRNA processing. Several lines of evidence indicate that hnRNP complexes undergo substantial remodeling during mRNA formation and export. Here we report the isolation of three distinct types of pre-mRNP and mRNP complexes from HeLa cells associated with hnRNP A1, a shuttling hnRNP protein. Based on their RNA and protein compositions, these complexes are likely to represent distinct stages in the nucleocytoplasmic shuttling pathway of hnRNP A1 with its bound RNAs. In the cytoplasm, A1 is associated with its nuclear import receptor (transportin), the cytoplasmic poly(A)-binding protein, and mRNA. In the nucleus, A1 is found in two distinct types of complexes that are differently associated with nuclear structures. One class contains pre-mRNA and mRNA and is identical to previously described hnRNP complexes. The other class behaves as freely diffusible nuclear mRNPs (nmRNPs) at late nuclear stages of maturation and possibly associated with nuclear mRNA export. These nmRNPs differ from hnRNPs in that while they contain shuttling hnRNP proteins, the mRNA export factor REF, and mRNA, they do not contain nonshuttling hnRNP proteins or pre-mRNA. Importantly, nmRNPs also contain proteins not found in hnRNP complexes. These include the alternatively spliced isoforms D01 and D02 of the hnRNP D proteins, the E0 isoform of the hnRNP E proteins, and LRP130, a previously reported protein with unknown function that appears to have a novel type of RNA-binding domain. The characteristics of these complexes indicate that they result from RNP remodeling associated with mRNA maturation and delineate specific changes in RNP protein composition during formation and transport of mRNA in vivo.
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Affiliation(s)
- S Mili
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029-6574, USA
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Mourelatos Z, Abel L, Yong J, Kataoka N, Dreyfuss G. SMN interacts with a novel family of hnRNP and spliceosomal proteins. EMBO J 2001; 20:5443-52. [PMID: 11574476 PMCID: PMC125643 DOI: 10.1093/emboj/20.19.5443] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a common neurodegenerative disease caused by deletion or loss-of-function mutations of the survival of motor neurons (SMN) protein. SMN is in a complex with several proteins, including Gemin2, Gemin3 and Gemin4, and it plays important roles in small nuclear ribonucleoprotein (snRNP) biogenesis and in pre-mRNA splicing. Here, we characterize three new hnRNP proteins, collectively referred to as hnRNP Qs, which are derived from alternative splicing of a single gene. The hnRNP Q proteins interact with SMN, and the most common SMN mutant found in SMA patients is defective in its interactions with them. We further demonstrate that hnRNP Qs are required for efficient pre-mRNA splicing in vitro. The hnRNP Q proteins may provide a molecular link between the SMN complex and splicing.
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Affiliation(s)
- Zissimos Mourelatos
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, and Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA Corresponding author e-mail:
| | - Linda Abel
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, and Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA Corresponding author e-mail:
| | - Jeongsik Yong
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, and Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA Corresponding author e-mail:
| | - Naoyuki Kataoka
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, and Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA Corresponding author e-mail:
| | - Gideon Dreyfuss
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, and Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA Corresponding author e-mail:
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