1
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Khalil B, Linsenmeier M, Smith CL, Shorter J, Rossoll W. Nuclear-import receptors as gatekeepers of pathological phase transitions in ALS/FTD. Mol Neurodegener 2024; 19:8. [PMID: 38254150 PMCID: PMC10804745 DOI: 10.1186/s13024-023-00698-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 12/13/2023] [Indexed: 01/24/2024] Open
Abstract
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative disorders on a disease spectrum that are characterized by the cytoplasmic mislocalization and aberrant phase transitions of prion-like RNA-binding proteins (RBPs). The common accumulation of TAR DNA-binding protein-43 (TDP-43), fused in sarcoma (FUS), and other nuclear RBPs in detergent-insoluble aggregates in the cytoplasm of degenerating neurons in ALS/FTD is connected to nuclear pore dysfunction and other defects in the nucleocytoplasmic transport machinery. Recent advances suggest that beyond their canonical role in the nuclear import of protein cargoes, nuclear-import receptors (NIRs) can prevent and reverse aberrant phase transitions of TDP-43, FUS, and related prion-like RBPs and restore their nuclear localization and function. Here, we showcase the NIR family and how they recognize cargo, drive nuclear import, and chaperone prion-like RBPs linked to ALS/FTD. We also discuss the promise of enhancing NIR levels and developing potentiated NIR variants as therapeutic strategies for ALS/FTD and related neurodegenerative proteinopathies.
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Affiliation(s)
- Bilal Khalil
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, U.S.A
| | - Miriam Linsenmeier
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, U.S.A
| | - Courtney L Smith
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, U.S.A
- Mayo Clinic Graduate School of Biomedical Sciences, Neuroscience Track, Mayo Clinic, Jacksonville, FL, 32224, U.S.A
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, U.S.A..
| | - Wilfried Rossoll
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, U.S.A..
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2
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Siculella L, Giannotti L, Di Chiara Stanca B, Spedicato F, Calcagnile M, Quarta S, Massaro M, Damiano F. A comprehensive understanding of hnRNP A1 role in cancer: new perspectives on binding with noncoding RNA. Cancer Gene Ther 2023; 30:394-403. [PMID: 36460805 DOI: 10.1038/s41417-022-00571-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 11/23/2022] [Accepted: 11/23/2022] [Indexed: 12/03/2022]
Abstract
The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is the most abundant and ubiquitously expressed member of the heterogeneous nuclear ribonucleoproteins family (hnRNPs). hnRNP A1 is an RNA-binding protein associated with complexes active in diverse biological processes such as RNA splicing, transactivation of gene expression, and modulation of protein translation. It is overexpressed in several cancers, where it actively promotes the expression and translation of several key proteins and regulators associated with tumorigenesis and cancer progression. Interesting recent studies have focused on the RNA-binding property of hnRNP A1 and revealed previously under-explored functions of hnRNP A1 in the processing of miRNAs, and loading non-coding RNAs into exosomes. Here, we will report the recent advancements in our knowledge of the role of hnRNP A1 in the biological processes underlying cancer proliferation and growth, with a particular focus on metabolic reprogramming.
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Affiliation(s)
- Luisa Siculella
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Laura Giannotti
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Benedetta Di Chiara Stanca
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Francesco Spedicato
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Matteo Calcagnile
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Stefano Quarta
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Marika Massaro
- Institute of Clinical Physiology (IFC), National Research Council (CNR), Lecce, Italy
| | - Fabrizio Damiano
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy.
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3
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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: 16] [Impact Index Per Article: 5.3] [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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4
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Cascarina SM, Ross ED. Natural and pathogenic protein sequence variation affecting prion-like domains within and across human proteomes. BMC Genomics 2020; 21:23. [PMID: 31914925 PMCID: PMC6947906 DOI: 10.1186/s12864-019-6425-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 12/23/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Impaired proteostatic regulation of proteins with prion-like domains (PrLDs) is associated with a variety of human diseases including neurodegenerative disorders, myopathies, and certain forms of cancer. For many of these disorders, current models suggest a prion-like molecular mechanism of disease, whereby proteins aggregate and spread to neighboring cells in an infectious manner. The development of prion prediction algorithms has facilitated the large-scale identification of PrLDs among "reference" proteomes for various organisms. However, the degree to which intraspecies protein sequence diversity influences predicted prion propensity has not been systematically examined. RESULTS Here, we explore protein sequence variation introduced at genetic, post-transcriptional, and post-translational levels, and its influence on predicted aggregation propensity for human PrLDs. We find that sequence variation is relatively common among PrLDs and in some cases can result in relatively large differences in predicted prion propensity. Sequence variation introduced at the post-transcriptional level (via alternative splicing) also commonly affects predicted aggregation propensity, often by direct inclusion or exclusion of a PrLD. Finally, analysis of a database of sequence variants associated with human disease reveals a number of mutations within PrLDs that are predicted to increase prion propensity. CONCLUSIONS Our analyses expand the list of candidate human PrLDs, quantitatively estimate the effects of sequence variation on the aggregation propensity of PrLDs, and suggest the involvement of prion-like mechanisms in additional human diseases.
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Affiliation(s)
- Sean M Cascarina
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA
| | - Eric D Ross
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA.
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5
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Deshaies JE, Shkreta L, Moszczynski AJ, Sidibé H, Semmler S, Fouillen A, Bennett ER, Bekenstein U, Destroismaisons L, Toutant J, Delmotte Q, Volkening K, Stabile S, Aulas A, Khalfallah Y, Soreq H, Nanci A, Strong MJ, Chabot B, Vande Velde C. TDP-43 regulates the alternative splicing of hnRNP A1 to yield an aggregation-prone variant in amyotrophic lateral sclerosis. Brain 2019; 141:1320-1333. [PMID: 29562314 DOI: 10.1093/brain/awy062] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 01/17/2018] [Indexed: 12/14/2022] Open
Abstract
See Fratta and Isaacs (doi:10.1093/brain/awy091) for a scientific commentary on this article.The RNA binding proteins TDP-43 (encoded by TARDBP) and hnRNP A1 (HNRNPA1) are each mutated in certain amyotrophic lateral sclerosis cases and are often mislocalized in cytoplasmic aggregates within motor neurons of affected patients. Cytoplasmic inclusions of TDP-43, which are accompanied by a depletion of nuclear TDP-43, are observed in most amyotrophic lateral sclerosis cases and nearly half of frontotemporal dementia cases. Here, we report that TDP-43 binds HNRNPA1 pre-mRNA and modulates its splicing, and that depletion of nuclear TDP-43 results in increased inclusion of a cassette exon in the HNRNPA1 transcript, and consequently elevated protein levels of an isoform containing an elongated prion-like domain, referred to as hnRNP A1B. Combined in vivo and in vitro approaches demonstrated greater fibrillization propensity for hnRNP A1B, which drives protein aggregation and is toxic to cells. Moreover, amyotrophic lateral sclerosis patients with documented TDP-43 pathology showed neuronal hnRNP A1B cytoplasmic accumulation, indicating that TDP-43 mislocalization may contribute to neuronal vulnerability and loss via altered HNRNPA1 pre-mRNA splicing and function. Given that TDP-43 and hnRNP A1 each bind, and thus modulate, a third of the transcriptome, our data suggest a much broader disruption in RNA metabolism than previously considered.
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Affiliation(s)
- Jade-Emmanuelle Deshaies
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada.,CHUM Research Center, Montréal, QC, Canada
| | - Lulzim Shkreta
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Alexander J Moszczynski
- Molecular Medicine Research Group, Robarts Research Institute, London, ON, Canada.,Department of Clinical Neurological Sciences, Western University, London, ON, Canada
| | - Hadjara Sidibé
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada.,CHUM Research Center, Montréal, QC, Canada
| | - Sabrina Semmler
- CHUM Research Center, Montréal, QC, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada
| | - Aurélien Fouillen
- Department of Stomatology, Université de Montréal, Montréal, QC, Canada
| | - Estelle R Bennett
- The Alexander Silberman Institute of Life Sciences, The Edmond and Lily Safra Center of Brain Science, The Hebrew University of Jerusalem, Israel
| | - Uriya Bekenstein
- The Alexander Silberman Institute of Life Sciences, The Edmond and Lily Safra Center of Brain Science, The Hebrew University of Jerusalem, Israel.,Department of Biological Chemistry, The Hebrew University of Jerusalem, Israel
| | | | - Johanne Toutant
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, QC, Canada
| | | | - Kathryn Volkening
- Molecular Medicine Research Group, Robarts Research Institute, London, ON, Canada.,Department of Clinical Neurological Sciences, Western University, London, ON, Canada
| | - Stéphanie Stabile
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada.,CHUM Research Center, Montréal, QC, Canada
| | - Anaïs Aulas
- CHUM Research Center, Montréal, QC, Canada.,Department of Biochemistry, Université de Montréal, Montréal, QC, Canada
| | - Yousra Khalfallah
- CHUM Research Center, Montréal, QC, Canada.,Department of Biochemistry, Université de Montréal, Montréal, QC, Canada
| | - Hermona Soreq
- The Alexander Silberman Institute of Life Sciences, The Edmond and Lily Safra Center of Brain Science, The Hebrew University of Jerusalem, Israel.,Department of Biological Chemistry, The Hebrew University of Jerusalem, Israel
| | - Antonio Nanci
- Department of Stomatology, Université de Montréal, Montréal, QC, Canada
| | - Michael J Strong
- Molecular Medicine Research Group, Robarts Research Institute, London, ON, Canada.,Department of Clinical Neurological Sciences, Western University, London, ON, Canada
| | - Benoit Chabot
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Christine Vande Velde
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada.,CHUM Research Center, Montréal, QC, Canada.,Department of Biochemistry, Université de Montréal, Montréal, QC, Canada
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6
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Shishkin SS, Kovalev LI, Pashintseva NV, Kovaleva MA, Lisitskaya K. Heterogeneous Nuclear Ribonucleoproteins Involved in the Functioning of Telomeres in Malignant Cells. Int J Mol Sci 2019; 20:E745. [PMID: 30744200 PMCID: PMC6387250 DOI: 10.3390/ijms20030745] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 01/31/2019] [Accepted: 02/04/2019] [Indexed: 12/12/2022] Open
Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are structurally and functionally distinct proteins containing specific domains and motifs that enable the proteins to bind certain nucleotide sequences, particularly those found in human telomeres. In human malignant cells (HMCs), hnRNP-A1-the most studied hnRNP-is an abundant multifunctional protein that interacts with telomeric DNA and affects telomerase function. In addition, it is believed that other hnRNPs in HMCs may also be involved in the maintenance of telomere length. Accordingly, these proteins are considered possible participants in the processes associated with HMC immortalization. In our review, we discuss the results of studies on different hnRNPs that may be crucial to solving molecular oncological problems and relevant to further investigations of these proteins in HMCs.
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Affiliation(s)
- Sergey S Shishkin
- Laboratory of Biomedical Research, Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt, 33, bld. 2, 119071 Moscow, Russia.
| | - Leonid I Kovalev
- Laboratory of Biomedical Research, Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt, 33, bld. 2, 119071 Moscow, Russia.
| | - Natalya V Pashintseva
- Laboratory of Biomedical Research, Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt, 33, bld. 2, 119071 Moscow, Russia.
| | - Marina A Kovaleva
- Laboratory of Biomedical Research, Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt, 33, bld. 2, 119071 Moscow, Russia.
| | - Ksenia Lisitskaya
- Laboratory of Biomedical Research, Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt, 33, bld. 2, 119071 Moscow, Russia.
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7
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Naruse H, Ishiura H, Mitsui J, Date H, Takahashi Y, Matsukawa T, Tanaka M, Ishii A, Tamaoka A, Hokkoku K, Sonoo M, Segawa M, Ugawa Y, Doi K, Yoshimura J, Morishita S, Goto J, Tsuji S. Molecular epidemiological study of familial amyotrophic lateral sclerosis in Japanese population by whole-exome sequencing and identification of novel HNRNPA1 mutation. Neurobiol Aging 2017; 61:255.e9-255.e16. [PMID: 29033165 DOI: 10.1016/j.neurobiolaging.2017.08.030] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 08/27/2017] [Accepted: 08/30/2017] [Indexed: 12/13/2022]
Abstract
To elucidate the genetic epidemiology of familial amyotrophic lateral sclerosis (FALS) in the Japanese population, we conducted whole-exome sequencing analysis of 30 FALS families in whom causative mutations have not been identified in previous studies. Consequently, whole-exome sequencing analysis revealed novel mutations in HNRNPA1, TBK1, and VCP. Taken together with our previous results of mutational analyses by direct nucleotide sequencing analysis, a microarray-based resequencing method, or repeat-primed PCR analysis, causative mutations were identified in 41 of the 68 families (60.3%) with SOD1 being the most frequent cause of FALS (39.7%). Of the mutations identified in this study, a novel c.862/1018C>G (p.P288A/340A) mutation in HNRNPA1 located in the nuclear localization signal domain of hnRNPA1, enhances the recruitment of mutant hnRNPA1 into stress granules, indicating that an altered nuclear localization signal activity plays an essential role in amyotrophic lateral sclerosis pathogenesis.
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Affiliation(s)
- Hiroya Naruse
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hiroyuki Ishiura
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Jun Mitsui
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hidetoshi Date
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yuji Takahashi
- Department of Neurology, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Takashi Matsukawa
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Masaki Tanaka
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Akiko Ishii
- Department of Neurology, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
| | - Akira Tamaoka
- Department of Neurology, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
| | - Keiichi Hokkoku
- Department of Neurology, Teikyo University School of Medicine, Tokyo, Japan
| | - Masahiro Sonoo
- Department of Neurology, Teikyo University School of Medicine, Tokyo, Japan
| | - Mari Segawa
- Department of Neurology, School of Medicine, Fukushima Medical University, Fukushima, Japan
| | - Yoshikazu Ugawa
- Department of Neurology, School of Medicine, Fukushima Medical University, Fukushima, Japan
| | - Koichiro Doi
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Jun Yoshimura
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Shinichi Morishita
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Jun Goto
- Department of Neurology, International University of Health and Welfare Mita Hospital, Tokyo, Japan
| | - Shoji Tsuji
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
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8
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Roy R, Huang Y, Seckl MJ, Pardo OE. Emerging roles of hnRNPA1 in modulating malignant transformation. WILEY INTERDISCIPLINARY REVIEWS-RNA 2017; 8. [PMID: 28791797 DOI: 10.1002/wrna.1431] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/19/2017] [Accepted: 05/22/2017] [Indexed: 01/05/2023]
Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are RNA-binding proteins associated with complex and diverse biological processes such as processing of heterogeneous nuclear RNAs (hnRNAs) into mature mRNAs, RNA splicing, transactivation of gene expression, and modulation of protein translation. hnRNPA1 is the most abundant and ubiquitously expressed member of this protein family and has been shown to be involved in multiple molecular events driving malignant transformation. In addition to selective mRNA splicing events promoting expression of specific protein variants, hnRNPA1 regulates the gene expression and translation of several key players associated with tumorigenesis and cancer progression. Here, we will summarize our current knowledge of the involvement of hnRNPA1 in cancer, including its roles in regulating cell proliferation, invasiveness, metabolism, adaptation to stress and immortalization. WIREs RNA 2017, 8:e1431. doi: 10.1002/wrna.1431 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Rajat Roy
- Division of Cancer, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Yueyang Huang
- Division of Cancer, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Michael J Seckl
- Division of Cancer, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Olivier E Pardo
- Division of Cancer, Department of Surgery and Cancer, Imperial College London, London, UK
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9
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Yu C, Guo J, Liu Y, Jia J, Jia R, Fan M. Oral squamous cancer cell exploits hnRNP A1 to regulate cell cycle and proliferation. J Cell Physiol 2015; 230:2252-61. [PMID: 25752295 DOI: 10.1002/jcp.24956] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 02/05/2015] [Indexed: 01/08/2023]
Abstract
Oral squamous cell carcinoma (OSCC) is a common human malignant tumor with high mortality. So far, the molecular pathogenesis of OSCC remains largely unclear. Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 is an important multi-function splicing factor and closely related to tumorigenesis. hnRNP A1 is overexpressed in various tumors, and promotes aerobic glycolysis and elongation of telomere, but the function of hnRNP A1 in cell cycle and proliferation remains unclear. We found that hnRNP A1 was overexpressed in OSCC tissues, and was required for the growth of OSCC cells. Moreover, hnRNP A1 was highly expressed in the G2/M cell cycle phase. Knockdown of hnRNP A1 induced G2/M arrest. DNA microarray assay result showed that hnRNP A1 regulated the expression of a number of target genes associated with G2/M phase. Moreover, hnRNP A1 controlled the alternative splicing of CDK2 exon 5. These findings suggested that hnRNP A1 plays key roles in the regulation of cell cycle progression and pathogenesis of OSCC.
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Affiliation(s)
- Cheng Yu
- Hubei-MOST KLOS & KLOBME, School & Hospital of Stomatology, Wuhan University, Wuhan, PR China
| | - Jihua Guo
- Hubei-MOST KLOS & KLOBME, School & Hospital of Stomatology, Wuhan University, Wuhan, PR China
| | - Yu Liu
- College of Life Sciences, Wuhan University, Wuhan, PR China
| | - Jun Jia
- Hubei-MOST KLOS & KLOBME, School & Hospital of Stomatology, Wuhan University, Wuhan, PR China
| | - Rong Jia
- Hubei-MOST KLOS & KLOBME, School & Hospital of Stomatology, Wuhan University, Wuhan, PR China
| | - Mingwen Fan
- Hubei-MOST KLOS & KLOBME, School & Hospital of Stomatology, Wuhan University, Wuhan, PR China
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10
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Shilo A, Ben Hur V, Denichenko P, Stein I, Pikarsky E, Rauch J, Kolch W, Zender L, Karni R. Splicing factor hnRNP A2 activates the Ras-MAPK-ERK pathway by controlling A-Raf splicing in hepatocellular carcinoma development. RNA (NEW YORK, N.Y.) 2014; 20:505-15. [PMID: 24572810 PMCID: PMC3964912 DOI: 10.1261/rna.042259.113] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 01/22/2014] [Indexed: 06/03/2023]
Abstract
In recent years, it has become clear that splicing factors play a direct role in cancer development. We showed previously that splicing factors SRSF1, SRSF6, and hnRNP A2/B1 are up-regulated in several cancers and can act as oncogenes when up-regulated. Here we examined the role of splicing factors hnRNP A1/A1b and hnRNP A2/B1 in hepatocellular carcinoma (HCC). We show that the splicing factors hnRNP A1 and hnRNP A2 are up-regulated in HCC tumors derived from inflammation-induced liver cancer mouse model. Overexpression of hnRNP A1 or hnRNP A2, but not the splicing isoform hnRNP B1, induced tumor formation of immortalized liver progenitor cells, while knockdown of these proteins inhibited anchorage-independent growth and tumor growth of human liver cancer cell lines. In addition, we found that cells overexpressing hnRNP A2 showed constitutive activation of the Ras-MAPK-ERK pathway. In contrast, knockdown of hnRNP A2 inhibited the Ras-MAPK-ERK pathway and prevented ERK1/2 activation by EGF. Moreover, we found that hnRNP A2 regulates the splicing of A-Raf, reducing the production of a short dominant-negative isoform of A-Raf and elevating the full-length A-Raf transcript. Taken together, our data suggest that hnRNP A2 up-regulation in HCC induces an alternative splicing switch that down-regulates a dominant-negative isoform of A-Raf, leading to activation of the Raf-MEK-ERK pathway and cellular transformation.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B/physiology
- Alternative Splicing
- Animals
- Carcinoma, Hepatocellular/etiology
- Carcinoma, Hepatocellular/metabolism
- Carcinoma, Hepatocellular/pathology
- Cell Transformation, Neoplastic/pathology
- Cells, Cultured
- Hepatocytes/metabolism
- Hepatocytes/pathology
- Heterogeneous Nuclear Ribonucleoprotein A1
- Heterogeneous-Nuclear Ribonucleoprotein Group A-B/antagonists & inhibitors
- Heterogeneous-Nuclear Ribonucleoprotein Group A-B/genetics
- Heterogeneous-Nuclear Ribonucleoprotein Group A-B/metabolism
- Humans
- Inflammation/complications
- Inflammation/genetics
- Inflammation/pathology
- Liver Neoplasms/etiology
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
- Mice
- Mice, Knockout
- Mice, Nude
- Mice, SCID
- Mitogen-Activated Protein Kinase 1/genetics
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3/genetics
- Mitogen-Activated Protein Kinase 3/metabolism
- Mitogen-Activated Protein Kinases/genetics
- Mitogen-Activated Protein Kinases/metabolism
- Proto-Oncogene Proteins A-raf/genetics
- RNA, Small Interfering/genetics
- Tumor Suppressor Protein p53/physiology
- Xenograft Model Antitumor Assays
- ras Proteins/genetics
- ras Proteins/metabolism
- ATP-Binding Cassette Sub-Family B Member 4
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Affiliation(s)
- Asaf Shilo
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada (IMRIC), Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Vered Ben Hur
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada (IMRIC), Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Polina Denichenko
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada (IMRIC), Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Ilan Stein
- Department of Immunology and Cancer Research, Institute for Medical Research Israel-Canada (IMRIC), Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
- Department of Pathology, Hebrew University-Hadassah Medical Center, Jerusalem 91120, Israel
| | - Eli Pikarsky
- Department of Immunology and Cancer Research, Institute for Medical Research Israel-Canada (IMRIC), Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
- Department of Pathology, Hebrew University-Hadassah Medical Center, Jerusalem 91120, Israel
| | - Jens Rauch
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland
| | - Walter Kolch
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland
| | - Lars Zender
- Division of Molecular Oncology of Solid Tumors, Department of Internal Medicine I, University Hospital Tuebingen, 72076 Tuebingen, Germany
| | - Rotem Karni
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada (IMRIC), Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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11
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Jean-Philippe J, Paz S, Lu ML, Caputi M. A truncated hnRNP A1 isoform, lacking the RGG-box RNA binding domain, can efficiently regulate HIV-1 splicing and replication. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:251-8. [PMID: 24530421 DOI: 10.1016/j.bbagrm.2014.02.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 01/31/2014] [Accepted: 02/05/2014] [Indexed: 10/25/2022]
Abstract
Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is one of the most abundant RNA binding proteins. hnRNP A1 is localized prevalently in the nucleus but it can relocate to the cytoplasm in response to specific stimuli shuttling between nuclear and cytoplasmic compartments. The cellular localization of this protein is regulated by a short C-terminus motif (M9) and other less defined sequences. The RNA binding specificity of this protein is dependent on multiple RNA binding domains (RBDs), which regulate its role in RNA processing and expression. hnRNP A1 plays multiple roles in gene expression by regulating the biogenesis and translation of messengers RNAs, the processing of miRNAs, affecting transcription and controlling telomere maintenance. The multiple functions of this protein correlate with diverse roles in genetic disease, cancer and the replication of viral pathogens. Utilizing a tagged hnRNP A1 deletion library we have shown that the three hnRNP A1 RBDs contribute to the prevalent nuclear distribution of the protein. Our data also indicate that a truncated form of the protein, lacking one of the RBDs, the RGG-box, can regulate splicing of a splicing reporter minigene and down-regulate replication of the HIV-1 virus with efficiency comparable to the wild-type protein. This functional hnRNP A1 deletion mutant is similar to a predicted hnRNP A1 isoform, which had not been previously experimentally characterized.
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Affiliation(s)
- Jacques Jean-Philippe
- Charles E. Schmidt College of Medicine, Florida Atlantic University, 777 Glades Rd, Boca Raton, FL 33431, USA
| | - Sean Paz
- Charles E. Schmidt College of Medicine, Florida Atlantic University, 777 Glades Rd, Boca Raton, FL 33431, USA
| | - Michael L Lu
- Charles E. Schmidt College of Medicine, Florida Atlantic University, 777 Glades Rd, Boca Raton, FL 33431, USA
| | - Massimo Caputi
- Charles E. Schmidt College of Medicine, Florida Atlantic University, 777 Glades Rd, Boca Raton, FL 33431, USA.
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12
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Han SP, Kassahn KS, Skarshewski A, Ragan MA, Rothnagel JA, Smith R. Functional implications of the emergence of alternative splicing in hnRNP A/B transcripts. RNA (NEW YORK, N.Y.) 2010; 16:1760-1768. [PMID: 20651029 PMCID: PMC2924535 DOI: 10.1261/rna.2142810] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 06/03/2010] [Indexed: 05/29/2023]
Abstract
The heterogeneous nuclear ribonucleoproteins (hnRNPs) A/B are a family of RNA-binding proteins that participate in various aspects of nucleic acid metabolism, including mRNA trafficking, telomere maintenance, and splicing. They are both regulators and targets of alternative splicing, and the patterns of alternative splicing of their transcripts have diverged between paralogs and between orthologs in different species. Surprisingly, the extent of this splicing variation and its implications for post-transcriptional regulation have remained largely unexplored. Here, we conducted a detailed analysis of hnRNP A/B sequences and expression patterns across six vertebrates. Alternative exons emerged via the introduction of new splice sites, changes in the strengths of existing splice sites, and the accumulation of auxiliary splicing regulatory motifs. Observed isoform expression patterns could be attributed to the frequency and strength of cis-elements. We found a trend toward increased splicing variation in mammals and identified novel alternatively spliced isoforms in human and chicken. Pulldown and translational assays demonstrated that the inclusion of alternative exons altered the affinity of hnRNP A/B proteins for their cognate nucleic acids and modified protein expression levels. As the hnRNPs A/B regulate several key steps in mRNA processing, the involvement of diverse hnRNP isoforms in multiple cellular contexts and species implies concomitant differences in the transcriptional output of these systems. We conclude that the emergence of alternative splicing in the hnRNPs A/B has contributed to the diversification of their roles in the regulation of alternative splicing and has thus added an unexpected layer of regulatory complexity to transcription in vertebrates.
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Affiliation(s)
- Siew Ping Han
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia
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13
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Tissue and developmental regulation of fragile X mental retardation 1 exon 12 and 15 isoforms. Neurobiol Dis 2009; 35:52-62. [PMID: 19362146 DOI: 10.1016/j.nbd.2009.03.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 03/24/2009] [Accepted: 03/29/2009] [Indexed: 11/22/2022] Open
Abstract
The pre-mRNA of the fragile X mental retardation 1 gene (FMR1) is subject to exon skipping and alternative splice site selection, which can generate up to 12 isoforms. The expression and function of these variants in vivo has not yet been fully explored. In the present study, we investigated the distribution of Fmr1 exon 12 and exon 15 isoforms. Exon 12 encodes an extension of KH(2) domain, one of the RNA binding domains in the FMR1 gene product (FMRP) and we show that exon 12 variant proteins differentially interact with kissing complex RNA. Alternative splicing at exon 15 produces FMRPs differing in RNA binding ability and each is distinguished by unique post-translational modifications. Using semiquantitative RT-PCR and Northern blotting, we found that particular Fmr1 exon 12 and exon 15 isoforms change during neuronal differentiation. Interestingly, Fmr1 exon 12 variants display tissue-specific and developmental differences, while exon 15-containing transcripts vary less. Altogether, the spatio-temporal plasticity of FMR1 mRNA is consistent with complex RNA processing that is mis-regulated in fragile X syndrome.
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14
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Siapka S, Patrinou-Georgoula M, Vlachoyiannopoulos PG, Guialis A. Multiple specificities of autoantibodies against hnRNP A/B proteins in systemic rheumatic diseases and hnRNP L as an associated novel autoantigen. Autoimmunity 2007; 40:223-33. [PMID: 17453722 DOI: 10.1080/08916930701352357] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Spliceosomal small nuclear ribonucleoproteins (U-snRNPs) are frequent and specific targets of autoantibodies in systemic rheumatic diseases. The abundant, functionally related heterogeneous nuclear ribonucleoprotein complexes (hnRNPs) have later defined as a new target of autoantibodies, of which their immunochemical/immunogenic and pathogenic properties are still under investigation. Among hnRNP proteins, those belonging to the A/B type are considered as the major autoantigens targeted by antibodies in sera of patients suffering with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). By performing an extensive screening using rat liver 40S hnRNP antigenic material, we document here the existence of multiple specificities of anti-hnRNP A/B autoantibodies in sera of Greek patients suffering with a spectrum of systemic rheumatic diseases. This included patients with SLE, Sjogren's syndrome (SS), Scleroderma (SSc) and a specific group of patients mostly with undifferentiated disease (UD patients). In total, four distinct types of anti-hnRNP A/B autoantibodies have been recognized. The first two referred to the known anti-hnRNPA2(RA33) and anti-hnRNP A1; the latter appearing very rarely. The third was of the new type selectively reacting with hnRNP B2 and an hnRNP A3 variant, while the fourth was a rare case of anti-hnRNP B2 alone. In addition, a novel specificity of autoantibodies against hnRNP L protein was identified in association with anti-hnRNP A/B antibodies. The co-existence within a serum of autoantibodies having variable specificity for hnRNP A/B and L autoantigens was shown. Specific immunochemical features of the identified autoantibodies are presented and a possible mechanism of autoepitope spreading within protein components of hnRNP complexes is discussed.
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Affiliation(s)
- Sorana Siapka
- RNA Processing Programme, Institute of Biological Research and Biotechnology, The National Hellenic Research Foundation, Vassileos Constantinou Avenue, Athens 116 35, Greece
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15
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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: 273] [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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16
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Harris D, Zhang Z, Chaubey B, Pandey VN. Identification of cellular factors associated with the 3'-nontranslated region of the hepatitis C virus genome. Mol Cell Proteomics 2006; 5:1006-18. [PMID: 16500930 DOI: 10.1074/mcp.m500429-mcp200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Chronic infection by hepatitis C virus (HCV) is the leading cause of severe hepatitis that often develops into liver cirrhosis and hepatocellular carcinoma. The molecular mechanisms underlying HCV replication and pathogenesis are poorly understood. Similarly, the role(s) of host factors in the replication of HCV remains largely undefined. Based on our knowledge of other RNA viruses, it is likely that a number of cellular factors may be involved in facilitating HCV replication. It has been demonstrated that elements within the 3'-nontranslated region (3'-NTR) of the (+) strand HCV genome are essential for initiation of (-) strand synthesis. The RNA signals within the highly conserved 3'-NTR may be the site for recruiting cellular factors that mediate virus replication/pathogenesis. However, the identities of putative cellular factors interacting with these RNA signals remain unknown. In this report, we demonstrate that an RNA affinity capture system developed in our laboratory used in conjunction with LC/MS/MS allowed us to positively identify more than 70 cellular proteins that interact with the 3'-NTR (+) of HCV. Binding of these cellular proteins was not competed out by a 10-fold excess of nonspecific competitor RNA. With few exceptions, all of the identified cellular proteins are RNA-binding proteins whose reported cellular functions provide unique insights into host cell-virus interactions and possible mechanisms influencing HCV replication and HCV-associated pathogenesis. Small interfering RNA-mediated silencing of selected 3'-NTR-binding proteins in an HCV replicon cell line reduced replicon RNA to undetectable levels, suggesting important roles for these cellular factors in HCV replication.
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Affiliation(s)
- Dylan Harris
- Department of Biochemistry and Molecular Biology and Centre for the Study of Emerging and Re-emerging Pathogens, University of Medicine and Dentistry of New Jersey--New Jersey Medical School, Newark, New Jersey 07103, USA
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17
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Abstract
Alternative pre-mRNA splicing is a central mode of genetic regulation in higher eukaryotes. Variability in splicing patterns is a major source of protein diversity from the genome. In this review, I describe what is currently known of the molecular mechanisms that control changes in splice site choice. I start with the best-characterized systems from the Drosophila sex determination pathway, and then describe the regulators of other systems about whose mechanisms there is some data. How these regulators are combined into complex systems of tissue-specific splicing is discussed. In conclusion, very recent studies are presented that point to new directions for understanding alternative splicing and its mechanisms.
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Affiliation(s)
- Douglas L Black
- Department of Microbiology, Immunology, and Molecular Genetics, Howard Hughes Medical Institute, University of California-Los Angeles, Los Angeles, California 90095-1662, USA.
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18
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Shi ST, Yu GY, Lai MMC. Multiple type A/B heterogeneous nuclear ribonucleoproteins (hnRNPs) can replace hnRNP A1 in mouse hepatitis virus RNA synthesis. J Virol 2003; 77:10584-93. [PMID: 12970443 PMCID: PMC228381 DOI: 10.1128/jvi.77.19.10584-10593.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 has previously been shown to bind mouse hepatitis virus (MHV) RNA at the 3' end of both plus and minus strands and modulate MHV RNA synthesis. However, a mouse erythroleukemia cell line, CB3, does not express hnRNP A1 but still supports MHV replication, suggesting that alternative proteins can replace hnRNP A1 in cellular functions and viral infection. In this study, we set out to identify these proteins. UV cross-linking experiments revealed that several CB3 cellular proteins similar in size to hnRNP A1 interacted with the MHV RNA. These proteins were purified by RNA affinity column with biotinylated negative-strand MHV leader RNA and identified by mass spectrometry to be hnRNP A2/B1, hnRNP A/B, and hnRNP A3, all of which belong to the type A/B hnRNPs. All of these proteins contain amino acid sequences with strong similarity to the RNA-binding domains of hnRNP A1. Some of these hnRNPs have previously been shown to replace hnRNP A1 in regulating RNA splicing. These proteins displayed MHV RNA-binding affinity and specificity similar to those of hnRNP A1. hnRNP A2/B1, which is predominantly localized to the nucleus and shuttles between the nucleus and the cytoplasm, was shown to relocalize to the cytoplasm in MHV-infected CB3 cells. Furthermore, overexpression of hnRNP A/B in cells enhanced MHV RNA synthesis. Our findings demonstrate that the functions of hnRNP A1 in MHV RNA synthesis can be replaced by other closely related hnRNPs, further supporting the roles of cellular proteins in MHV RNA synthesis.
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Affiliation(s)
- Stephanie T Shi
- Department of Molecular Microbiology and Immunology and Howard Hughes Medical Institute, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA
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19
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Bronstein NB, Kishore R, Ismail Z, Zhang Q, Taylor T, Newman SA. cDNA cloning and spatiotemporal expression during avian embryogenesis of hnRNP A1, a regulatory factor in alternative splicing. Gene Expr Patterns 2003; 3:285-95. [PMID: 12799073 DOI: 10.1016/s1567-133x(03)00048-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Alternative splicing and selective transport of RNA transcripts from cell nuclei are important regulatory mechanisms of gene expression during embryonic development. Here we report the molecular characterization and developmental expression in several tissue and organ systems of chicken hnRNP A1, a nucleo-cytoplasmic 'shuttle' protein which in mammalian systems has been shown to function in the regulation of RNA alternative splicing by antagonizing constitutive splicing factors such as SF2/ASF. We show that hnRNP A1 is represented in the chicken by a single gene which is widely expressed at early embryonic stages, with particularly high levels of expression in the brain, skin, developing gut, and other ectodermal and endodermal derivatives. At later stages, expression of its mRNA and protein product become progressively confined to specific organ primordia and cell types, where both transient and persistent expression patterns are observed. HnRNP A1 protein is expressed at sites of active neurogenesis in the developing central and peripheral nervous systems, regions of known extensive alternative splicing.
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Affiliation(s)
- Natalie B Bronstein
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA
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20
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Chabot B, LeBel C, Hutchison S, Nasim FH, Simard MJ. Heterogeneous nuclear ribonucleoprotein particle A/B proteins and the control of alternative splicing of the mammalian heterogeneous nuclear ribonucleoprotein particle A1 pre-mRNA. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2003; 31:59-88. [PMID: 12494763 DOI: 10.1007/978-3-662-09728-1_3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Affiliation(s)
- B Chabot
- Département de Microbiologie et d'Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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21
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Rooke N, Markovtsov V, Cagavi E, Black DL. Roles for SR proteins and hnRNP A1 in the regulation of c-src exon N1. Mol Cell Biol 2003; 23:1874-84. [PMID: 12612063 PMCID: PMC149473 DOI: 10.1128/mcb.23.6.1874-1884.2003] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2002] [Revised: 09/25/2002] [Accepted: 12/16/2002] [Indexed: 12/27/2022] Open
Abstract
The splicing of the c-src exon N1 is controlled by an intricate combination of positive and negative RNA elements. Most previous work on these sequences focused on intronic elements found upstream and downstream of exon N1. However, it was demonstrated that the 5' half of the N1 exon itself acts as a splicing enhancer in vivo. Here we examine the function of this regulatory element in vitro. We show that a mutation in this sequence decreases splicing of the N1 exon in vitro. Proteins binding to this element were identified as hnRNP A1, hnRNP H, hnRNP F, and SF2/ASF by site-specific cross-linking and immunoprecipitation. The binding of these proteins to the RNA was eliminated by a mutation in the exonic element. The activities of hnRNP A1 and SF2/ASF on N1 splicing were examined by adding purified protein to in vitro splicing reactions. SF2/ASF and another SR protein, SC35, are both able to stimulate splicing of c-src pre-mRNA. However, splicing activation by SF2/ASF is dependent on the N1 exon enhancer element whereas activation by SC35 is not. In contrast to SF2/ASF and in agreement with other systems, hnRNP A1 repressed c-src splicing in vitro. The negative activity of hnRNP A1 on splicing was compared with that of PTB, a protein previously demonstrated to repress splicing in this system. Both proteins repress exon N1 splicing, and both counteract the enhancing activity of the SR proteins. Removal of the PTB binding sites upstream of N1 prevents PTB-mediated repression but does not affect A1-mediated repression. Thus, hnRNP A1 and PTB use different mechanisms to repress c-src splicing. Our results link the activity of these well-known exonic splicing regulators, SF2/ASF and hnRNP A1, to the splicing of an exon primarily controlled by intronic factors.
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Affiliation(s)
- Nanette Rooke
- Department of Microbiology, Immunology and Molecular Genetics, University of California-Los Angeles, 1602 Molecular Sciences Building, 405 Hilgard Avenue, Los Angeles, CA 90095, USA
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22
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Ma ASW, Moran-Jones K, Shan J, Munro TP, Snee MJ, Hoek KS, Smith R. Heterogeneous nuclear ribonucleoprotein A3, a novel RNA trafficking response element-binding protein. J Biol Chem 2002; 277:18010-20. [PMID: 11886857 DOI: 10.1074/jbc.m200050200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cis-acting response element, A2RE, which is sufficient for cytoplasmic mRNA trafficking in oligodendrocytes, binds a small group of rat brain proteins. Predominant among these is heterogeneous nuclear ribonucleoprotein (hnRNP) A2, a trans-acting factor for cytoplasmic trafficking of RNAs bearing A2RE-like sequences. We have now identified the other A2RE-binding proteins as hnRNP A1/A1(B), hnRNP B1, and four isoforms of hnRNP A3. The rat and human hnRNP A3 cDNAs have been sequenced, revealing the existence of alternatively spliced mRNAs. In Western blotting, 38-, 39-, 41-, and 41.5-kDa components were all recognized by antibodies against a peptide in the glycine-rich region of hnRNP A3, but only the 41- and 41.5-kDa bands bound antibodies to a 15-residue N-terminal peptide encoded by an alternatively spliced part of exon 1. The identities of these four proteins were verified by Edman sequencing and mass spectral analysis of tryptic fragments generated from electrophoretically separated bands. Sequence-specific binding of bacterially expressed hnRNP A3 to A2RE has been demonstrated by biosensor and UV cross-linking electrophoretic mobility shift assays. Mutational analysis and confocal microscopy data support the hypothesis that the hnRNP A3 isoforms have a role in cytoplasmic trafficking of RNA.
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Affiliation(s)
- Alice S W Ma
- Department of Biochemistry and Molecular Biology, The University of Queensland, Brisbane, Queensland 4072, Australia
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23
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Hay DC, Kemp GD, Dargemont C, Hay RT. Interaction between hnRNPA1 and IkappaBalpha is required for maximal activation of NF-kappaB-dependent transcription. Mol Cell Biol 2001; 21:3482-90. [PMID: 11313474 PMCID: PMC100270 DOI: 10.1128/mcb.21.10.3482-3490.2001] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcriptional activation of NF-kappaB is mediated by signal-induced phosphorylation and degradation of its inhibitor, IkappaBalpha. NF-kappaB activation induces a rapid resynthesis of IkappaBalpha which is responsible for postinduction repression of transcription. Following resynthesis, IkappaBalpha translocates to the nucleus, removes template bound NF-kappaB, and exports NF-kappaB to the cytoplasm in a transcriptionally inactive form. Here we demonstrate that IkappaBalpha interacts directly with another nucleocytoplasmic shuttling protein, hnRNPA1, both in vivo and in vitro. This interaction requires one of the N-terminal RNA binding domains of hnRNPA1 and the C-terminal region of IkappaBalpha. Cells lacking hnRNPA1 are defective in NF-kappaB-dependent transcriptional activation, but the defect in these cells is complemented by ectopic expression of hnRNPA1. hnRNPA1 expression in these cells increased the amount of IkappaBalpha degradation, compared to that of the control cells, in response to activation by Epstein-Barr virus latent membrane protein 1. Thus in addition to regulating mRNA processing and transport, hnRNPA1 also contributes to the control of NF-kappaB-dependent transcription.
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Affiliation(s)
- D C Hay
- Institute of Biomolecular Sciences, School of Biology, University of St. Andrews, The North Haugh, St. Andrews, KY16 9ST, Scotland
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24
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Matsui M, Horiguchi H, Kamma H, Fujiwara M, Ohtsubo R, Ogata T. Testis- and developmental stage-specific expression of hnRNP A2/B1 splicing isoforms, B0a/b. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1493:33-40. [PMID: 10978504 DOI: 10.1016/s0167-4781(00)00154-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) A2 and B1 are abundant nuclear proteins that bind to nascent RNAs synthesized by RNA polymerase II. Previously we had found that the splicing isoforms hnRNP B0a/b, from which the ninth exon of the A2/B1 gene is excluded, are abundantly expressed in testis. We postulated that B0a/b are testis-specific isoforms, and investigated the expression of A2/B1 and B0a/b in rat tissues and in postnatal development of rat testes using RNase protection assay, immunoblotting, and immunohistochemistry. We found that hnRNP B0a/b mRNAs are expressed in several tissues but that the testis alone expresses B0a/b proteins. A sequential study using neonatal rat testes demonstrated that B0a/b mRNAs are produced after 17 days of age, but not translated until 4 weeks of age when round spermatids appear in addition to spermatogonia and spermatocytes. Immunohistochemically, hnRNP A2/B1 isoforms are expressed during spermatogenesis from spermatogonia through round spermatids, whereas the expression of A1 is restricted to spermatogonia. This expression pattern in the rat testis is maintained from birth through adulthood. These results suggest that the expression of the hnRNP A2/B1 gene is partly regulated by a testis-specific post-transcriptional mechanism, and that the products of the A2/B1 gene, especially hnRNP B0a/b, are involved in spermatogenesis.
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Affiliation(s)
- M Matsui
- Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, Ibraki 300-0394, Japan
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25
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Honoré B. The hnRNP 2H9 gene, which is involved in the splicing reaction, is a multiply spliced gene. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1492:108-19. [PMID: 10858537 DOI: 10.1016/s0167-4781(00)00092-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The hnRNP 2H9 gene products are involved in the splicing process and participate in early heat shock-induced splicing arrest. By combining low/high stringency hybridisation, database search, Northern and Western blotting it is shown that the gene is alternatively spliced into at least six transcripts: hnRNPs 2H9, 2H9A, 2H9B, 2H9C, 2H9D and 2H9E predicting proteins containing 346, 331, 297, 215, 145 and 139 amino acids, respectively. The hnRNP 2H9A cDNA sequence was used to obtain a genomic BAC clone and the structure of the hnRNP 2H9 gene was revealed by sequencing two subclones together spanning about 6.7 kb. The six transcripts are processed from at least 10, 10, 8, 7, 5 and 4 exons, respectively, with all intron/exon junctions obeying the 'GT-AG' rule. The hnRNP 2H9 and 2H9A proteins contain two RNA recognition motifs of the quasi-RRM type found in the two C-terminal qRRMs of the hnRNPs H, H' and F proteins. The hnRNP 2H9B protein has a partially deleted N-terminal qRRM, which is completely deleted in hnRNP 2H9C. hnRNPs 2H9D and 2H9E contain only one slightly modified C-terminal qRRM. Furthermore, the six proteins vary in their auxiliary domains outside the qRRMs. Western blotting indicates that the alternatively spliced transcripts give rise to different sets and levels of proteins expressed among various human cells and tissues. Due to their great structural variations the different proteins may thus possess different functions in the splicing reaction.
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Affiliation(s)
- B Honoré
- Department of Medical Biochemistry, University of Aarhus, Ole Worms Allé, Bldg. 170, DK-8000 Aarhus C, Denmark.
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26
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Kim JH, Hahm B, Kim YK, Choi M, Jang SK. Protein-protein interaction among hnRNPs shuttling between nucleus and cytoplasm. J Mol Biol 2000; 298:395-405. [PMID: 10772858 DOI: 10.1006/jmbi.2000.3687] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are involved in several RNA-related biological processes such as transcription, pre-mRNA processing, mature mRNA transport to the cytoplasm, and translation. About 20 major hnRNPs from A1 to U are known. Among them, hnRNP A, D, E, I, and K are known to shuttle between the nucleus and the cytoplasm. hnRNP E2 has been seen to stabilize alpha-globin mRNA and to enhance polioviral mRNA translation. hnRNP K modulates transcription and translation of some mRNAs. hnRNP I and its homologue hnRNP L have been suggested to enhance translation of some IRES-dependent mRNAs. In order to better understand the molecular mechanisms of the biological functions of hnRNPs, we investigated protein-protein interactions of six hnRNPs (hnRNP A1, C1, E2, I, K, and L) using the yeast two-hybrid system and in vitro co-precipitation assays. All of the hnRNPs tested exerted homomeric interactions, and hnRNP E2, I, K, and L interacted with each other. In the case of hnRNP E2 and hnRNP K, the N-terminal half of the proteins containing two KH (K homologous) domains were required for protein-protein interaction, and the second quarter of hnRNP I and hnRNP L containing RRM2 (RNA recognition motif 2) was essential for protein-protein interaction. hnRNP A1 and C1 did not form complexes with other hnRNPs in our assay systems. This suggests that the hnRNPs could fall into two groups: one group, including hnRNP A1 and C1, involved in hnRNP core complex formation and another group, including hnRNP E2, I, K, and L, involved in a variety of RNA-related biological processes. Different combinations of the proteins of the second group may facilitate different biological processes in conjunction with other factors.
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Affiliation(s)
- J H Kim
- Department of Life Science, Pohang University of Science and Technology, Hyoja-Dong San31, Pohang, Kyungbuk, 790-784, Korea
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27
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Plomaritoglou A, Choli-Papadopoulou T, Guialis A. Molecular characterization of a murine, major A/B type hnRNP protein: mBx. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1490:54-62. [PMID: 10786617 DOI: 10.1016/s0167-4781(99)00054-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously identified a discrete hnRNP polypeptide of the A/B type, named mBx, as an abundant protein species in murine cells. The molecular characterization of this protein is now accomplished. From all evidence provided, mBx polypeptide represents a new gene product, distinct from the known members of the A/B family A1 and A2/B1. It is, instead, mostly related to a still hypothetical human protein of A/B type, as well as to the Xenopus hnRNPA3 protein species.
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Affiliation(s)
- A Plomaritoglou
- Laboratory of Molecular Biology, Institute of Biological Research and Biotechnology, The National Hellenic Research Foundation, Athens, Greece
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28
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Weighardt F, Cobianchi F, Cartegni L, Chiodi I, Villa A, Riva S, Biamonti G. A novel hnRNP protein (HAP/SAF-B) enters a subset of hnRNP complexes and relocates in nuclear granules in response to heat shock. J Cell Sci 1999; 112 ( Pt 10):1465-76. [PMID: 10212141 DOI: 10.1242/jcs.112.10.1465] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A two-hybrid screening in yeast for proteins interacting with the human hnRNP A1, yielded a nuclear protein of 917 amino acids that we termed hnRNP A1 associated protein (HAP). HAP contains an RNA binding domain (RBD) flanked by a negatively charged domain and by an S/K-R/E-rich region. In in vitro pull-down assays, HAP interacts with hnRNP A1, through its S/K-R/E-rich region, and with several other hnRNPs. HAP was found to be identical to the previously described Scaffold Attachment Factor B (SAF-B) and to HET, a transcriptional regulator of the Heat Shock Protein 27 gene. We show that HAP is a bona fide hnRNP protein, since anti-HAP antibodies immunoprecipitate from HeLa cell nucleoplasm the complete set of hnRNP proteins. Unlike most hnRNP proteins, the subnuclear distribution of HAP is profoundly modified in heat-shocked HeLa cells. Heat-shock treatment at 42 degrees C causes a transcription-dependent recruitment of HAP to a few large nuclear granules that exactly coincide with sites of accumulation of Heat Shock Factor 1 (HSF1). The recruitment of HAP to the granules is temporally delayed with respect to HSF1 and persists for a longer time during recovery at 37 degrees C. The hnRNP complexes immunoprecipitated from nucleoplasm of heat-shocked cells with anti-HAP antibodies have an altered protein composition with respect to canonical complexes. Altogether our results suggest an involvement of HAP in the cellular response to heat shock, possibly at the RNA metabolism level.
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Affiliation(s)
- F Weighardt
- Istituto di Genetica Biochimica ed Evoluzionistica, CNR Via Abbiategrasso 207, Italy
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29
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Kamma H, Horiguchi H, Wan L, Matsui M, Fujiwara M, Fujimoto M, Yazawa T, Dreyfuss G. Molecular characterization of the hnRNP A2/B1 proteins: tissue-specific expression and novel isoforms. Exp Cell Res 1999; 246:399-411. [PMID: 9925756 DOI: 10.1006/excr.1998.4323] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
hnRNP A2/B1 proteins are among the most abundant pre-mRNA-binding proteins of vertebrates and structurally similar to hnRNP A1. We have produced two specific monoclonal antibodies against A2 and B1 and studied their molecular characteristics and in vivo expression in rat tissues. Immunoprecipitation demonstrated that the hnRNP A2/B1 complexes contain many snRNP (small nuclear ribonucleoprotein) proteins, consistent with their role in pre-mRNA splicing. RNA polymerase II inhibition causes nucleocytoplasmic shuttling of A2 and B1. In most tissues, they are localized in the nucleus; however, in the squamous epithelium of the skin and esophagus A2 is also distributed in the cytoplasm. The relative amounts of A2 and B1 are not constant among different tissues. In the adrenal, only A2 is extremely abundant in the medulla but not in the cortex. In the testis the expression of A2 and B1 are observed through spermatogenesis, and different from A1 which is stringently repressed in spermatocytes. We also found and cloned a novel testis-specific isoform of A2/B1, namely hnRNP B0. The difference of expression of A2, B1, and A1 provides new information on their in vivo roles. The diversity of A/B group hnRNP proteins may have important effects on the posttranscriptional regulation of cell-specific gene expression.
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Affiliation(s)
- H Kamma
- Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, 305-8575, Japan.
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30
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Zu K, Sikes ML, Beyer AL. Separable roles in vivo for the two RNA binding domains of Drosophila A1-hnRNP homolog. RNA (NEW YORK, N.Y.) 1998; 4:1585-1598. [PMID: 9848655 PMCID: PMC1369727 DOI: 10.1017/s135583829898102x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We analyzed the roles of the three domains of a Drosophila hnRNP A1 homolog by expression of wild-type and mutant versions of HRB87F/hrp36 in Drosophila melanogaster. HRB87F/hrp36 is one of two Drosophila proteins that is most similar to mammalian A1 hnRNP, and like A1, consists of two copies of the RNA-binding domain (RBD) motif followed by a glycine-rich domain (GRD). The role of the domains in nuclear localization and RNA binding to polytene chromosomal sites was determined. RBD-1 and the GRD were largely responsible for both the cellular location of the protein and for the typical chromosomal distribution pattern of the protein at sites of PolII transcription. RBD-1 also provided a role in the exon-skipping activity of the protein that was not provided by RBD-2. On the other hand, RBD-2 and the GRD were responsible for the very limited chromosomal distribution pattern seen upon heat shock, when HRB87F/hrp36 is sequestered at heat-shock puff 93D, which encodes a long nucleus-restricted RNA. Thus, these studies indicate that the two RBDs function independently of each other but in concert with the GRD. In addition, the self-association property of the GRD was strikingly evident in these overexpressed proteins.
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Affiliation(s)
- K Zu
- Department of Microbiology, University of Virginia, Charlottesville 22908, USA
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31
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Hanamura A, Cáceres JF, Mayeda A, Franza BR, Krainer AR. Regulated tissue-specific expression of antagonistic pre-mRNA splicing factors. RNA (NEW YORK, N.Y.) 1998; 4:430-444. [PMID: 9630249 PMCID: PMC1369629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The SR proteins are essential metazoan pre-mRNA splicing factors that can also influence the selection of alternative 5' splice sites in a concentration-dependent manner. Their activity in alternative splicing in vitro is antagonized by members of the hnRNP A/B family of proteins. The opposite effects of members of these two families of antagonistic splicing factors in vitro and upon overexpression in vivo suggest that changes in their relative levels may be a natural mechanism for the regulation of alternative splicing in vivo. One prediction of this model is that the ratios of these antagonists should vary in different cell types and in other situations in which cellular or viral transcripts are differentially spliced. We raised monoclonal antibodies specific for SF2/ASF and used them to measure the abundance of SF2/ASF protein and its isoforms, its phosphorylation state in vivo and during splicing in vitro, and its association with the spliceosome. SF2/ASF exists predominantly or exclusively in a highly phosphorylated state in vivo in all cell types examined, and unphosphorylated protein was not detectable. Unphosphorylated recombinant SF2/ASF becomes rapidly phosphorylated under splicing conditions in HeLa cell extracts and associates stably with one or more exons of beta-globin pre-mRNA. This interaction appears to persist through the splicing reaction and SF2/ASF remains bound to spliced mRNA. We compared the distribution of SF2/ASF to that of its antagonist, hnRNP A1, in different rat tissues and in immortal and transformed cell lines. We found that the protein levels of these antagonistic splicing factors vary naturally over a very wide range, supporting the notion that changes in the ratio of these proteins can affect alternative splicing of a variety of pre-mRNAs in vivo.
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Affiliation(s)
- A Hanamura
- Cold Spring Harbor Laboratory, New York 11724-2208, USA
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32
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Li HP, Zhang X, Duncan R, Comai L, Lai MM. Heterogeneous nuclear ribonucleoprotein A1 binds to the transcription-regulatory region of mouse hepatitis virus RNA. Proc Natl Acad Sci U S A 1997; 94:9544-9. [PMID: 9275159 PMCID: PMC23214 DOI: 10.1073/pnas.94.18.9544] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A cellular protein, previously described as p35/38, binds to the complementary (-)-strand of the leader RNA and intergenic (IG) sequence of mouse hepatitis virus (MHV) RNA. The extent of the binding of this protein to IG sites correlates with the efficiency of the subgenomic mRNA transcription from that IG site, suggesting that it is a requisite transcription factor. We have purified this protein and determined by partial peptide sequencing that it is heterogeneous nuclear ribonucleoprotein (hnRNP) A1, an abundant, primarily nuclear protein. hnRNP A1 shuttles between the nucleus and cytoplasm and plays a role in the regulation of alternative RNA splicing. The MHV(-)-strand leader and IG sequences conform to the consensus binding motifs of hnRNP A1. Recombinant hnRNP A1 bound to these two RNA regions in vitro in a sequence-specific manner. During MHV infection, hnRNP A1 relocalizes from the nucleus to the cytoplasm, where viral replication occurs. These data suggest that hnRNP A1 is a cellular factor that regulates the RNA-dependent RNA transcription of the virus.
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Affiliation(s)
- H P Li
- Department of Molecular Microbiology and Immunology, University of Southern California Schools of Medicine, Los Angeles, CA 90033, USA
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33
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Wang J, Dong Z, Bell LR. Sex-lethal interactions with protein and RNA. Roles of glycine-rich and RNA binding domains. J Biol Chem 1997; 272:22227-35. [PMID: 9268369 DOI: 10.1074/jbc.272.35.22227] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Sex-lethal (Sxl) is an RNA-binding protein, containing two conserved RNA binding domains (RBDs) and a glycine-rich region, which functions as a regulator of alternative splicing in Drosophila sex determination. Previous work demonstrated that Sxl monomers interact cooperatively upon binding to target RNAs and that the cooperativity depends on the glycine-rich N terminus. Here we use band shift experiments to show that RNA binding patterns are altered when Sxl is combined with other proteins having similar glycine-rich domains, including mammalian heterogeneous nuclear (hn) RNP L and Drosophila Hrb87F (an hnRNP A/B homolog). Direct involvement of the Sxl glycine-rich region in protein interactions was verified by Far-Western analysis. Two interaction domains, the Sxl N terminus and the Sxl first RNA binding domain, were suggested by the yeast two-hybrid assay. In a systematic examination of the RNA binding properties of Sxl domains, it was found that the Sxl termini as well as the RBDs influence RNA binding specificity. Finally, selection of the Sxl optimal binding site (SELEX) confirms the importance of U-runs in the Sxl binding site and suggests a second type of non-U-run target that may be associated with RNA secondary structure.
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Affiliation(s)
- J Wang
- Molecular Biology Program, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-1340, USA
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34
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Liang P, Amons R, Clegg JS, MacRae TH. Molecular characterization of a small heat shock/alpha-crystallin protein in encysted Artemia embryos. J Biol Chem 1997; 272:19051-8. [PMID: 9228089 DOI: 10.1074/jbc.272.30.19051] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Molecular chaperones protect cells during stress by limiting the denaturation/aggregation of proteins and facilitating their renaturation. In this context, brine shrimp embryos can endure a wide variety of stressful conditions, including temperature extremes, prolonged anoxia, and desiccation, thus encountering shortages of both energy (ATP) and water. How the embryos survive these stresses is the subject of continuing study, a situation true for other organisms facing similar physiological challenges. To approach this question we cloned and sequenced a cDNA for p26, a molecular chaperone specific to oviparous Artemia embryos. p26 is the first representative of the small heat shock/alpha-crystallin family from crustaceans to be sequenced, and it possesses the conserved alpha-crystallin domain characteristic of these proteins. The secondary structure of this domain was predicted to consist predominantly of beta-pleated sheet, and it appeared to lack regions of alpha-helix. Unique properties of the nonconserved amino terminus, which showed weak similarity to nucleolins and fibrillarins, are enrichments in both glycine and arginine. The carboxyl-terminal tail is the longest yet reported for a small heat shock/alpha-crystallin protein, and it is hydrophilic, a common attribute of this region. Site-specific differences between amino acids from p26 and other small heat shock/alpha-crystallin proteins bring into question the functions proposed for some of these residues. Probing of Southern blots disclosed a multi-gene family for p26, whereas two size classes of p26 mRNA at 0.7 and 1.9 kilobase pairs were seen on Northern blots, the larger probably representing nonprocessed transcripts. Examination of immunofluorescently stained samples with the confocal microscope revealed that a limited portion of intracellular p26 is found in the nuclei of encysted embryos and that it resides within discrete compartments of this organelle. The results in this paper demonstrate clearly that p26 is a novel member of the small heat shock/alpha-crystallin family of proteins. These data, in concert with its restriction to embryos undergoing oviparous development, suggest that p26 functions as a molecular chaperone during exposure to stress, perhaps able to limit protein degradation and thus ensure a ready supply of functional proteins when growth is reinitiated.
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Affiliation(s)
- P Liang
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada
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35
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Weighardt F, Biamonti G, Riva S. The roles of heterogeneous nuclear ribonucleoproteins (hnRNP) in RNA metabolism. Bioessays 1996; 18:747-56. [PMID: 8831291 DOI: 10.1002/bies.950180910] [Citation(s) in RCA: 163] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In eukaryotic cells, messenger RNAs are formed by extensive post-transcriptional processing of primary transcripts, assembled with a large number of proteins and processing factors in ribonucleoprotein complexes. The protein moiety of these complexes mainly constitutes a class of about 20 major polypeptides called heterogeneous nuclear ribonucleoproteins or hnRNPs. The function and the mechanism of action of hnRNPs is still not fully understood, but the identification of RNA binding domains and RNA binding specificities, and the development of new functional assays, has stimulated interest in them. In contrast to previous models that hypothesised a mere structural (histone-like) function, a more diversified and dynamic role for these proteins is now emerging. In fact, they can be viewed as a subset of the trans-acting pre-mRNA maturation factors. They might actively participate in post-transcriptional events such as regulated splicing and mRNA export. Moreover, recent data suggest an involvement of some of these proteins in molecular diseases. Here we present an overview of the most relevant properties of hnRNPs and discuss some emerging ideas on their roles.
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Affiliation(s)
- F Weighardt
- Istituto di Genetica Biochimica ed Evoluzionistica del CNR, Pavia, Italy.
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36
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Steiner G, Skriner K, Hassfeld W, Smolen JS. Clinical and immunological aspects of autoantibodies to RA33/hnRNP-A/B proteins--a link between RA, SLE and MCTD. Mol Biol Rep 1996; 23:167-71. [PMID: 9112225 DOI: 10.1007/bf00351165] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Heterogeneous nuclear ribonucleoprotein (hnRNP) complexes are major constituents of the spliceosome. They are composed of approximately 30 different proteins which can bind to nascent pre-mRNA. Among these, the hnRNP-A/B proteins form a subgroup of highly related proteins consisting of two adjacent RNA binding domains (RBD) within the N-terminal parts, whereas the C-terminal halves contain almost 50% glycine residues. These proteins, in particular A2/RA33, are targeted by autoantibodies from patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and mixed connective tissue disease (MCTD). In SLE anti-hnRNP antibodies frequently occur together with antibodies to U1 small nuclear RNP (U1-snRNP) and Sm, other proteins of the spliceosome. Preliminary epitope mapping studies have revealed major antibody binding sites in the RNA binding regions for all three diseases. Nevertheless, there is some indication of disease specific epitope recognition. Studies in animal models have demonstrated anti-RA33/hnRNP-A/B antibodies in lupus-prone mouse strains. Thus, autoantibodies to the spliceosomal hnRNP-A/B proteins are a common feature of RA, SLE, and MCTD. However, these diseases differ in their reactivities to other spliceosomal proteins, especially anti-U1 snRNP and Sm. Therefore, anti-RA33/hnRNP-A/B autoantibodies are not only valuable diagnostic markers but may also allow additional insights into the pathogenesis of rheumatic autoimmune diseases.
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Affiliation(s)
- G Steiner
- Ludwig Boltzmann-Institute for Rheumatology and Balneology, University of Vienna, Austria
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37
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Michael WM, Choi M, Dreyfuss G. A nuclear export signal in hnRNP A1: a signal-mediated, temperature-dependent nuclear protein export pathway. Cell 1995; 83:415-22. [PMID: 8521471 DOI: 10.1016/0092-8674(95)90119-1] [Citation(s) in RCA: 420] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Pre-mRNAs are associated with hnRNPs, and these proteins play important roles in the biogenesis of mRNAs. The hnRNP A1 is one of the most abundant hnRNPs, and although localized primarily in the nucleoplasm, shuttles continuously between the nucleus and the cytoplasm. A 38 amino acid domain within A1, termed M9, which bears no resemblance to classical nuclear localization signal (NLS) sequences, localizes A1 to the nucleus. Here we show that M9 is also a nuclear export signal; placing M9 on a protein that is otherwise restricted to the nucleus, the nucleoplasmin core domain (NPc), efficiently exports it to the cytoplasm in a temperature-dependent manner. In contrast, classical NLSs cannot promote the export of NPc. These findings demonstrate that there is a signal-dependent, temperature-sensitive nuclear export pathway and strengthen the suggestion that A1 and other shuttling hnRNPs function as carriers for RNA during export to the cytoplasm.
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Affiliation(s)
- W M Michael
- Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6148, USA
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38
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Kajita Y, Nakayama J, Aizawa M, Ishikawa F. The UUAG-specific RNA binding protein, heterogeneous nuclear ribonucleoprotein D0. Common modular structure and binding properties of the 2xRBD-Gly family. J Biol Chem 1995; 270:22167-75. [PMID: 7673195 DOI: 10.1074/jbc.270.38.22167] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Human cDNA clones encoding the UUAG-binding heterogeneous nuclear ribonucleoprotein (hnRNP) D0 protein have been isolated and expressed. The protein has two RNA-binding domains (RBDs) in the middle part of the protein and an RGG box, a region rich in glycine and arginine residues, in the C-terminal part ("2xRBD-Gly" structure). The hnRNP A1, A2/B1, and D0 proteins, all possess common features of the 2xRBD-Gly structure and binding specificity toward RNA. Together, they form a subfamily of RBD class RNA binding proteins (the 2xRBD-Gly family). One of the structural characteristics shared by these proteins is the presence of several isoforms presumably resulting from alternative splicing. Filter binding assays, using the recombinant hnRNP D0 proteins that have one of the two RBDs, indicated that one RBD specifically binds to the UUAG sequence. However, two isoforms with or without a 19-amino acid insertion at the N-terminal RBD showed different preference toward mutant RNA substrates. The 19-amino acid insertion is located in the N-terminal end of the first RBD. This result establishes the participation of the N terminus of RBD in determining the sequence specificity of binding. A similar insertion was also reported with the hnRNP A2/B1 proteins. Thus, it might be possible that this type of insertion with the 2xRBD-Gly type RNA binding proteins plays a role in "fine tuning" the specificity of RNA binding. RBD is supposed to bind with RNA in general and sequence-specific manners. These two discernible binding modes are proposed to be performed by different regions of the RBD. A structural model of these two binding sites is presented.
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Affiliation(s)
- Y Kajita
- Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan
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39
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Siebel CW, Admon A, Rio DC. Soma-specific expression and cloning of PSI, a negative regulator of P element pre-mRNA splicing. Genes Dev 1995; 9:269-83. [PMID: 7867926 DOI: 10.1101/gad.9.3.269] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
PSI is an RNA-binding protein involved in repressing splicing of the P element third intron in Drosophila somatic cell extracts. PSI produced in bacteria restores splicing inhibition to an extract relieved of inhibitory activity, indicating that PSI plays a direct role in somatic inhibition. Sequence analysis of cDNAs encoding PSI reveals three KH RNA-binding domains, a conserved motif also found in the yeast splicing regulator MER1. Notably, PSI is expressed highly in somatic embryonic nuclei but is undetectable in germ-line cells. In contrast, hrp48, another protein implicated in somatic inhibition, is found in the nucleus and cytoplasm of both tissues. The splicing inhibitory properties and soma-specific expression of PSI may be sufficient to explain the germ-line-specific transposition of P elements.
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Affiliation(s)
- C W Siebel
- Department of Molecular and Cell Biology, University of California at Berkeley 94720
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40
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Kozu T, Henrich B, Schäfer KP. Structure and expression of the gene (HNRPA2B1) encoding the human hnRNP protein A2/B1. Genomics 1995; 25:365-71. [PMID: 7789969 DOI: 10.1016/0888-7543(95)80035-k] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Heterogeneous nuclear ribonucleoprotein (hnRNP) A2 is a major nuclear protein and one of the major components of the hnRNP core complex in mammalian cells. We first determined the complete sequence of the human gene for hnRNP protein A2 (HNRPA2B1). The human HNRPA2B1 gene exists in a single copy over 9 kb in length. The gene was split into 12 exons, including a 36-nucleotide mini-exon, which was specific to the hnRNP protein B1, providing genetic evidence that the B1 mRNA was generated from the primary HNRPA2B1 transcript by alternative splicing. The 5' region of HNRPA2B1 was GC-rich and contained several DNA motifs for the binding of several transcription factors, which included 2 CCAAT boxes and no TATA sequences. The 5' ends of the mRNA were mapped to multiple positions. These structural features are characteristic of promoter regions of housekeeping genes. Northern blot and RT-PCR analyses of the HNRPA2B1 transcripts revealed levels of B1 mRNA from 2 to 5% of total A2/B1 transcripts and showed that both A2 and B1 mRNAs were transcribed in all human cell lines and mouse tissues studied. The structural and evolutionary characteristics of the A2 and A1 proteins as they relate to each other are discussed.
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Affiliation(s)
- T Kozu
- Department of Immunology and Virology, Saitama Cancer Center Research Institute, Japan
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41
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Pype S, Slegers H, Moens L, Merlevede W, Goris J. Tyrosine phosphorylation of a M(r) 38,000 A/B-type hnRNP protein selectively modulates its RNA binding. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)31716-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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42
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Wang J, Bell LR. The Sex-lethal amino terminus mediates cooperative interactions in RNA binding and is essential for splicing regulation. Genes Dev 1994; 8:2072-85. [PMID: 7958879 DOI: 10.1101/gad.8.17.2072] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Sex-lethal (Sxl) acts as a binary switch that regulates Drosophila sexual differentiation and dosage compensation and also maintains a stable female state through autoregulation. As part of a cascade of genes that are regulated by sex-specific splicing, Sxl controls the sex-specific splicing of transformer (tra) RNA and also its own RNA. Sxl contains two RNP-CS (RNA-binding) domains and is known to bind tra pre-mRNA near the alternative 3' splice site, thus blocking use of that site to give the female-specific splicing pattern. Here, we test how Sxl protein interacts with Sxl RNA during autoregulation. We show that Sxl not only binds Sxl pre-mRNA near the alternative 3' splice site but also at distant, multiple sites surrounding the Sxl alternative exon. Moreover, Sxl binds cooperatively at these multiple sites. The Sxl amino terminus is essential for the cooperative interaction and is also required for regulatory activity in vivo. It appears that this region of Sxl protein, which resembles regions in some other RNA-binding proteins, is a domain that mediates protein-protein interactions during RNA binding and plays an important role in splicing regulation.
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Affiliation(s)
- J Wang
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-1340
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Cobianchi F, Biamonti G, Maconi M, Riva S. Human hnRNP protein A1: a model polypeptide for a structural and genetic investigation of a broad family of RNA binding proteins. Genetica 1994; 94:101-14. [PMID: 7896132 DOI: 10.1007/bf01443425] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The hnRNP fiber is the substrate on which pre-mRNA processing occurs. The protein moiety of the fiber (hnRNP proteins) constitutes a broad family of RNA binding proteins that revealed, upon molecular analysis, a number of interesting features. Heterogeneous nuclear ribonucleoprotein A1 is a major component of the human hnRNP complex. In recent years this protein has attracted great attention because of several emerging evidences of its direct involvement in pre-mRNA processing and it has become one of the best characterized RNA binding proteins. Detailed knowledge of the structure of protein A1 has laid the basis for the understanding of its function, and for this reason A1 can be considered as a model polypeptide for the investigation of a large number of RNA binding proteins. In this work we report recent findings regarding the binding properties of protein A1 as well as new data on the gene structure of A1 and of its closely related hnRNP protein A2. Our results show that a single A1 molecule contains the determinants for simultaneous binding of two single-stranded nucleic acid molecules and we demonstrate that the glycine-rich domain of A1, isolated from the rest of the molecule, is capable of sustaining protein-protein interactions. These features probably account for the reannealing activity of the protein and for its capacity to modulate the binding of snRNPs to intron sequences in vitro. Comparison of A1 and A2 gene sequences revealed a remarkable conservation of the overall structural organization, suggesting important functions for the different structural elements.
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Affiliation(s)
- F Cobianchi
- Istituto di Genetica Biochimica ed Evoluzionistica, CNR, Pavia, Italy
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44
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Abstract
Eukaryotic RNA binding proteins (RBP) are key players in RNA processing and in post-transcriptional regulation of gene expression. By interacting with RNA and other factors and by modulating the RNA structure, they promote the assembly of a great variety of specific ribonucleoprotein complexes. Many RBPs are composed of highly structured and conserved RNA binding domains (RBD) linked to unstructured and divergent auxiliary domains; such modular structure can account for a multiplicity of interactions. In this context, the auxiliary domains emerge as essential partners of the RBDs in both RNA binding and functional specialisation. Moreover, the determinants of biologically important functions, such as strand annealing, protein-protein interactions, nuclear localization and activity in in vitro splicing, seem to reside in the auxiliary domains. The structural and functional properties of these domains suggest their possible derivation from ancestral non-specific RNA binding polypeptides.
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Affiliation(s)
- G Biamonti
- Istituto di Genetica Biochimica ed Evoluzionistica del CNR, Pavia, Italy
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45
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Enhanced stability of interleukin-2 mRNA in MLA 144 cells. Possible role of cytoplasmic AU-rich sequence-binding proteins. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37697-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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46
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Hamilton B, Nagy E, Malter J, Arrick B, Rigby W. Association of heterogeneous nuclear ribonucleoprotein A1 and C proteins with reiterated AUUUA sequences. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)52955-0] [Citation(s) in RCA: 142] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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47
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An G, Wu R. cDNA cloning of a hnRNP A1 isoform and its regulation by retinol in monkey tracheobronchial epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1172:292-300. [PMID: 8448206 DOI: 10.1016/0167-4781(93)90216-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
An isoform of the hnRNP A1 was cloned from a cDNA library of monkey tracheobronchial epithelial (TBE) cells by differential hybridization. The cDNA clone MT77 has an insert of 1756 base pairs and the DNA sequence shares high homology to both human A1 alpha-type and beta-type isoforms with the exception of several differences in the coding and noncoding regions. Like the other two isoforms, MT77 has two polyadenylation sites. A probe prepared from the MT77 clone hybridizes to two message bands at 1.4 and 1.8 kb. Both messages were found in a polysomal preparation, suggesting that both messages are used in A1 protein synthesis. The expression of the A1 gene in monkey TBE cells is stimulated by vitamin A (retinol). The results of nuclear run-on transcriptional assays suggest that this stimulation occurs at the transcriptional level. Furthermore, this effect is not prevented, but superinduced, by cycloheximide. These results suggest that vitamin A may be directly involved in regulating A1 transcription through a mechanism similar to the interactions between the retinoic acid responsive elements and the nuclear receptors of retinoic acid.
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Affiliation(s)
- G An
- California Primate Research Center, University of California-Davis 95616
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48
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Abstract
When messenger RNA precursors (pre-mRNAs) containing alternative 5' splice sites are spliced in vitro, the relative concentrations of the heterogeneous ribonucleoprotein (hnRNP) A1 and the essential splicing factor SF2 precisely determine which 5' splice site is selected. In general, an excess of hnRNP A1 favors distal 5' splice sites, whereas an excess of SF2 results in utilization of proximal 5' splice sites. The regulation of these antagonistic activities may play an important role in the tissue-specific and developmental control of gene expression by alternative splicing.
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Affiliation(s)
- A Mayeda
- Cold Spring Harbor Laboratory, New York, New York 11724-2208
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49
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Steinert PM, Mack JW, Korge BP, Gan SQ, Haynes SR, Steven AC. Glycine loops in proteins: their occurrence in certain intermediate filament chains, loricrins and single-stranded RNA binding proteins. Int J Biol Macromol 1991; 13:130-9. [PMID: 1716976 DOI: 10.1016/0141-8130(91)90037-u] [Citation(s) in RCA: 161] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Quasi-repetitive, glycine-rich peptide sequences are widespread in at least three distinct families of proteins: the keratins and other intermediate filament proteins, including nuclear lamins; loricrins, which are major envelope components of terminally differentiated epithelial cells; and single-stranded RNA binding proteins. We propose that such sequences comprise a new structural motif termed the 'glycine loop'. The defining characteristics of glycine loop sequences are: (1) they have the form x(y)n, where x is usually an aromatic or occasionally a long-chain aliphatic residue; y is usually glycine but may include polar residues such as serine, asparagine, arginine, cysteine, and rarely other residues; and the value of n is highly variable, ranging from 1 to 35 in examples identified to date. (2) Glycine-loop-containing domains are thought to form when at least two and to date, as many as 18, such quasi-repeats are configured in tandem, so that the entire domain in a protein may be 50-150 residues long. (3) The average value of n, the pattern of residues found in the x position and the non-glycine substitutions in the y position appear to be characteristic of a given glycine loop containing domain, whereas the actual number of repeats is less constrained. (4) Glycine loop sequences display a high degree of evolutionary sequence variability and even allelic variations among different individuals of the same vertebrate species. (5) Glycine loop sequences are expected to be highly flexible, but possess little other regular secondary structure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P M Steinert
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal Diseases, National Institutes of Health, Bethesda, MD 20892
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