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Choi HJ, Lee JY, Kim K. Glutathionylation on RNA-binding proteins: a regulator of liquid‒liquid phase separation in the pathogenesis of amyotrophic lateral sclerosis. Exp Mol Med 2023; 55:735-744. [PMID: 37009800 PMCID: PMC10167235 DOI: 10.1038/s12276-023-00978-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/09/2023] [Accepted: 01/11/2023] [Indexed: 04/04/2023] Open
Abstract
RNA-binding proteins (RBPs) containing low-sequence complexity domains mediate the formation of cellular condensates and membrane-less organelles with biological functions via liquid‒liquid phase separation (LLPS). However, the abnormal phase transition of these proteins induces the formation of insoluble aggregates. Aggregates are pathological hallmarks of neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS). The molecular mechanisms underlying aggregate formation by ALS-associated RPBs remain largely unknown. This review highlights emerging studies on various posttranslational modifications (PTMs) related to protein aggregation. We begin with the introduction of several ALS-associated RBPs that form aggregates induced by phase separation. In addition, we highlight our recent discovery of a new PTM involved in the phase transition during the pathogenesis of fused-in-sarcoma (FUS)-associated ALS. We suggest a molecular mechanism through which LLPS mediates glutathionylation in FUS-linked ALS. This review aims to provide a detailed overview of the key molecular mechanisms of LLPS-mediated aggregate formation by PTMs, which will help further the understanding of the pathogenesis and development of ALS therapeutics.
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Affiliation(s)
- Hyun-Jun Choi
- Soonchunhyang Institute of Medi-bio Science, Soonchunhyang University, Cheonan, 31151, Korea
- Department of Integrated Biomedical Sciences, Soonchunhyang University, Cheonan, 31151, Korea
| | - Ji Young Lee
- Department of Medical Biotechnology, Soonchunhyang University, Asan, 31538, Korea
- Department of Medical Science, Soonchunhyang University, Asan, 31538, Korea
| | - Kiyoung Kim
- Department of Medical Science, Soonchunhyang University, Asan, 31538, Korea.
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2
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Shi Y, Li Z, Wang B, Shi X, Ye H, Delafield DG, Lv L, Ye Z, Chen Z, Ma F, Li L. Enabling Global Analysis of Protein Citrullination via Biotin Thiol Tag-Assisted Mass Spectrometry. Anal Chem 2022; 94:17895-17903. [PMID: 36512406 DOI: 10.1021/acs.analchem.2c03844] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Citrullination is a key post-translational modification (PTM) that affects protein structures and functions. Although it has been linked to various biological processes and disease pathogenesis, the underlying mechanism remains poorly understood due to a lack of effective tools to enrich, detect, and localize this PTM. Herein, we report the design and development of a biotin thiol tag that enables derivatization, enrichment, and confident identification of citrullination via mass spectrometry. We perform global mapping of the citrullination proteome of mouse tissues. In total, we identify 691 citrullination sites from 432 proteins which represents the largest data set to date. We discover novel distribution and functions of this PTM. This study depicts a landscape of protein citrullination and lays the foundation for further deciphering their physiological and pathological roles.
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Affiliation(s)
- Yatao Shi
- School of Pharmacy, University of Wisconsin─Madison, Madison, Wisconsin 53705, United States
| | - Zihui Li
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Bin Wang
- School of Pharmacy, University of Wisconsin─Madison, Madison, Wisconsin 53705, United States
| | - Xudong Shi
- Department of Surgery, School of Medicine and Public Health, University of Wisconsin─Madison, Madison, Wisconsin 53792, United States
| | - Hui Ye
- School of Pharmaceutical Sciences, China Pharmaceutical University, Nanjing, 210009, China
| | - Daniel G Delafield
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Langlang Lv
- School of Pharmaceutical Sciences, China Pharmaceutical University, Nanjing, 210009, China
| | - Zhengqing Ye
- Medicinal Chemistry Center, School of Pharmacy, University of Wisconsin─Madison, Madison, Wisconsin 53705, United States
| | - Zhengwei Chen
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Fengfei Ma
- School of Pharmacy, University of Wisconsin─Madison, Madison, Wisconsin 53705, United States
| | - Lingjun Li
- School of Pharmacy, University of Wisconsin─Madison, Madison, Wisconsin 53705, United States.,Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
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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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Cerasuolo A, Buonaguro L, Buonaguro FM, Tornesello ML. The Role of RNA Splicing Factors in Cancer: Regulation of Viral and Human Gene Expression in Human Papillomavirus-Related Cervical Cancer. Front Cell Dev Biol 2020; 8:474. [PMID: 32596243 PMCID: PMC7303290 DOI: 10.3389/fcell.2020.00474] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 05/20/2020] [Indexed: 12/12/2022] Open
Abstract
The spliceosomal complex components, together with the heterogeneous nuclear ribonucleoproteins (hnRNPs) and serine/arginine-rich (SR) proteins, regulate the process of constitutive and alternative splicing, the latter leading to the production of mRNA isoforms coding multiple proteins from a single pre-mRNA molecule. The expression of splicing factors is frequently deregulated in different cancer types causing the generation of oncogenic proteins involved in cancer hallmarks. Cervical cancer is caused by persistent infection with oncogenic human papillomaviruses (HPVs) and constitutive expression of viral oncogenes. The aberrant activity of hnRNPs and SR proteins in cervical neoplasia has been shown to trigger the production of oncoproteins through the processing of pre-mRNA transcripts either derived from human genes or HPV genomes. Indeed, hnRNP and SR splicing factors have been shown to regulate the production of viral oncoprotein isoforms necessary for the completion of viral life cycle and for cell transformation. Target-therapy strategies against hnRNPs and SR proteins, causing simultaneous reduction of oncogenic factors and inhibition of HPV replication, are under development. In this review, we describe the current knowledge of the functional link between RNA splicing factors and deregulated cellular as well as viral RNA maturation in cervical cancer and the opportunity of new therapeutic strategies.
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Affiliation(s)
| | | | | | - Maria Lina Tornesello
- Molecular Biology and Viral Oncology Unit, Istituto Nazionale Tumouri IRCCS–Fondazione G. Pascale, Naples, Italy
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5
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Lorton BM, Shechter D. Cellular consequences of arginine methylation. Cell Mol Life Sci 2019; 76:2933-2956. [PMID: 31101937 PMCID: PMC6642692 DOI: 10.1007/s00018-019-03140-2] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/22/2019] [Accepted: 05/10/2019] [Indexed: 02/07/2023]
Abstract
Arginine methylation is a ubiquitous post-translational modification. Three predominant types of arginine-guanidino methylation occur in Eukarya: mono (Rme1/MMA), symmetric (Rme2s/SDMA), and asymmetric (Rme2a/ADMA). Arginine methylation frequently occurs at sites of protein-protein and protein-nucleic acid interactions, providing specificity for binding partners and stabilization of important biological interactions in diverse cellular processes. Each methylarginine isoform-catalyzed by members of the protein arginine methyltransferase family, Type I (PRMT1-4,6,8) and Type II (PRMT5,9)-has unique downstream consequences. Methylarginines are found in ordered domains, domains of low complexity, and in intrinsically disordered regions of proteins-the latter two of which are intimately connected with biological liquid-liquid phase separation. This review highlights discoveries illuminating how arginine methylation affects genome integrity, gene transcription, mRNA splicing and mRNP biology, protein translation and stability, and phase separation. As more proteins and processes are found to be regulated by arginine methylation, its importance for understanding cellular physiology will continue to grow.
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Affiliation(s)
- Benjamin M Lorton
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - David Shechter
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
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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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Rasputin a decade on and more promiscuous than ever? A review of G3BPs. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1866:360-370. [PMID: 30595162 PMCID: PMC7114234 DOI: 10.1016/j.bbamcr.2018.09.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 08/29/2018] [Accepted: 09/04/2018] [Indexed: 12/12/2022]
Abstract
Ras-GTPase-activating protein (SH3 domain)-binding proteins (G3BPs, also known as Rasputin) are a family of RNA binding proteins that regulate gene expression in response to environmental stresses by controlling mRNA stability and translation. G3BPs appear to facilitate this activity through their role in stress granules for which they are considered a core component, however, it should be noted that not all stress granules contain G3BPs and this appears to be contextual depending on the environmental stress and the cell type. Although the role of G3BPs in stress granules appears to be one of its major roles, data also strongly suggests that they interact with mRNAs outside of stress granules to regulate gene expression. G3BPs have been implicated in several diseases including cancer progression, invasion, and metastasis as well as virus survival. There is now a body of evidence that suggests targeting of G3BPs could be explored as a form of cancer therapeutic. This review discusses the important discoveries and advancements made in the field of G3BPs biology over the last two decades including their roles in RNA stability, translational control of cellular transcripts, stress granule formation, cancer progression and its interactions with viruses during infection. An emerging theme for G3BPs is their ability to regulate gene expression in response to environmental stimuli, disease progression and virus infection making it an intriguing target for disease therapies. Triage of many cellular mRNA occurs via stress granules in a G3BP-dependant manner. G3BPs control intra cellular responses to viral infection. Transcript stability, degradation and translation are controlled by G3BPs. G3BPs can control cancer progression.
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8
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Chong PA, Vernon RM, Forman-Kay JD. RGG/RG Motif Regions in RNA Binding and Phase Separation. J Mol Biol 2018; 430:4650-4665. [PMID: 29913160 DOI: 10.1016/j.jmb.2018.06.014] [Citation(s) in RCA: 230] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 06/02/2018] [Accepted: 06/06/2018] [Indexed: 12/29/2022]
Abstract
RGG/RG motifs are RNA binding segments found in many proteins that can partition into membraneless organelles. They occur in the context of low-complexity disordered regions and often in multiple copies. Although short RGG/RG-containing regions can sometimes form high-affinity interactions with RNA structures, multiple RGG/RG repeats are generally required for high-affinity binding, suggestive of the dynamic, multivalent interactions that are thought to underlie phase separation in formation of cellular membraneless organelles. Arginine can interact with nucleotide bases via hydrogen bonding and π-stacking; thus, nucleotide conformers that provide access to the bases provide enhanced opportunities for RGG interactions. Methylation of RGG/RG regions, which is accomplished by protein arginine methyltransferase enzymes, occurs to different degrees in different cell types and may regulate the behavior of proteins containing these regions.
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Affiliation(s)
- P Andrew Chong
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada
| | - Robert M Vernon
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada
| | - Julie D Forman-Kay
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada; Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
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9
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Ryan VH, Dignon GL, Zerze GH, Chabata CV, Silva R, Conicella AE, Amaya J, Burke KA, Mittal J, Fawzi NL. Mechanistic View of hnRNPA2 Low-Complexity Domain Structure, Interactions, and Phase Separation Altered by Mutation and Arginine Methylation. Mol Cell 2018; 69:465-479.e7. [PMID: 29358076 DOI: 10.1016/j.molcel.2017.12.022] [Citation(s) in RCA: 261] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 11/10/2017] [Accepted: 12/22/2017] [Indexed: 01/21/2023]
Abstract
hnRNPA2, a component of RNA-processing membraneless organelles, forms inclusions when mutated in a syndrome characterized by the degeneration of neurons (bearing features of amyotrophic lateral sclerosis [ALS] and frontotemporal dementia), muscle, and bone. Here we provide a unified structural view of hnRNPA2 self-assembly, aggregation, and interaction and the distinct effects of small chemical changes-disease mutations and arginine methylation-on these assemblies. The hnRNPA2 low-complexity (LC) domain is compact and intrinsically disordered as a monomer, retaining predominant disorder in a liquid-liquid phase-separated form. Disease mutations D290V and P298L induce aggregation by enhancing and extending, respectively, the aggregation-prone region. Co-aggregating in disease inclusions, hnRNPA2 LC directly interacts with and induces phase separation of TDP-43. Conversely, arginine methylation reduces hnRNPA2 phase separation, disrupting arginine-mediated contacts. These results highlight the mechanistic role of specific LC domain interactions and modifications conserved across many hnRNP family members but altered by aggregation-causing pathological mutations.
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Affiliation(s)
- Veronica H Ryan
- Neuroscience Graduate Program, Brown University, Providence, RI 02912, USA
| | - Gregory L Dignon
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Gül H Zerze
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Charlene V Chabata
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Rute Silva
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Alexander E Conicella
- Graduate Program in Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Joshua Amaya
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Kathleen A Burke
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Jeetain Mittal
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Nicolas L Fawzi
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA.
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10
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Gao G, Dhar S, Bedford MT. PRMT5 regulates IRES-dependent translation via methylation of hnRNP A1. Nucleic Acids Res 2017; 45:4359-4369. [PMID: 28115626 PMCID: PMC5416833 DOI: 10.1093/nar/gkw1367] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/20/2016] [Accepted: 12/29/2016] [Indexed: 01/19/2023] Open
Abstract
The type II arginine methyltransferase PRMT5 is responsible for the symmetric dimethylation of histone to generate the H3R8me2s and H4R3me2s marks, which correlate with the repression of transcription. However, the protein level of a number of genes (MEP50, CCND1, MYC, HIF1a, MTIF and CDKN1B) are reported to be downregulated by the loss of PRMT5, while their mRNA levels remain unchanged, which is counterintuitive for PRMT5's proposed role as a transcription repressor. We noticed that the majority of the genes regulated by PRMT5, at the posttranscriptional level, express mRNA containing an internal ribosome entry site (IRES). Using an IRES-dependent reporter system, we established that PRMT5 facilitates the translation of a subset of IRES-containing genes. The heterogeneous nuclear ribonucleoprotein, hnRNP A1, is an IRES transacting factor (ITAF) that regulates the IRES-dependent translation of Cyclin D1 and c-Myc. We showed that hnRNP A1 is methylated by PRMT5 on two residues, R218 and R225, and that this methylation facilitates the interaction of hnRNP A1 with IRES RNA to promote IRES-dependent translation. This study defines a new role for PRMT5 regulation of cellular protein levels, which goes beyond the known functions of PRMT5 as a transcription and splicing regulator.
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Affiliation(s)
- Guozhen Gao
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Surbhi Dhar
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Mark T Bedford
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
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11
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Wall ML, Lewis SM. Methylarginines within the RGG-Motif Region of hnRNP A1 Affect Its IRES Trans-Acting Factor Activity and Are Required for hnRNP A1 Stress Granule Localization and Formation. J Mol Biol 2016; 429:295-307. [PMID: 27979648 DOI: 10.1016/j.jmb.2016.12.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 11/22/2016] [Accepted: 12/08/2016] [Indexed: 12/30/2022]
Abstract
Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is a stress granule-associated RNA-binding protein that plays a role in apoptosis and cellular stress recovery. HnRNP A1 is a major non-histone target of protein arginine methyltransferase 1, which asymmetrically dimethylates hnRNP A1 at several key arginine residues within its arginine-glycine-glycine (RGG)-motif region. Although arginine methylation is known to regulate general RNA binding of hnRNP A1 in vitro, the functional role of arginine methylation in hnRNP A1 cytoplasmic activity is unknown. To test the impact of key methylarginine residues on hnRNP A1 cytoplasmic activity and stress granule association, cytoplasmically restricted Flag-tagged mutants of hnRNP A1 were generated in which key methylarginine residues within the RGG-motif region were changed to either lysine or alanine. Lysine substitution, which mimics unmethylated arginine, resulted in a 40% increase in internal ribosome entry site trans-acting factor (ITAF) activity and the protein readily associates with stress granules. Alanine substitution resulted in a loss of ITAF activity and reduced mRNA binding. The alanine mutant also displays reduced stress granule association and suppresses stress granule formation. Our data suggest that arginine residues within the RGG-motif region are critical for hnRNP A1 cytoplasmic activities and that endogenous asymmetric dimethylation of the RGG-motif region suppresses hnRNP A1 ITAF activity in cells. Our findings indicate that methylarginine residues within the RGG-motif region of hnRNP A1 are important for its cytoplasmic activities and that hypomethylation and/or mutation of the RGG-motif region may contribute to the role of hnRNP A1 in diseases such as cancer.
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Affiliation(s)
- Michael L Wall
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada
| | - Stephen M Lewis
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada; Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Biology, University of New Brunswick, Saint John, New Brunswick, Canada; Department of Chemistry & Biochemistry, Université de Moncton, Moncton, New Brunswick, Canada.
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