1
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Zhao Q, Pavanello L, Bartlam M, Winkler GS. Structure and function of molecular machines involved in deadenylation-dependent 5'-3' mRNA degradation. Front Genet 2023; 14:1233842. [PMID: 37876592 PMCID: PMC10590902 DOI: 10.3389/fgene.2023.1233842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 09/25/2023] [Indexed: 10/26/2023] Open
Abstract
In eukaryotic cells, the synthesis, processing, and degradation of mRNA are important processes required for the accurate execution of gene expression programmes. Fully processed cytoplasmic mRNA is characterised by the presence of a 5'cap structure and 3'poly(A) tail. These elements promote translation and prevent non-specific degradation. Degradation via the deadenylation-dependent 5'-3' degradation pathway can be induced by trans-acting factors binding the mRNA, such as RNA-binding proteins recognising sequence elements and the miRNA-induced repression complex. These factors recruit the core mRNA degradation machinery that carries out the following steps: i) shortening of the poly(A) tail by the Ccr4-Not and Pan2-Pan3 poly (A)-specific nucleases (deadenylases); ii) removal of the 5'cap structure by the Dcp1-Dcp2 decapping complex that is recruited by the Lsm1-7-Pat1 complex; and iii) degradation of the mRNA body by the 5'-3' exoribonuclease Xrn1. In this review, the biochemical function of the nucleases and accessory proteins involved in deadenylation-dependent mRNA degradation will be reviewed with a particular focus on structural aspects of the proteins and enzymes involved.
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Affiliation(s)
- Qi Zhao
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai International Advanced Research Institute (Shenzhen Futian), Nankai University, Tianjin, China
| | - Lorenzo Pavanello
- School of Pharmacy, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Mark Bartlam
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai International Advanced Research Institute (Shenzhen Futian), Nankai University, Tianjin, China
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2
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McCombe CL, Catanzariti AM, Greenwood JR, Desai AM, Outram MA, Yu DS, Ericsson DJ, Brenner SE, Dodds PN, Kobe B, Jones DA, Williams SJ. A rust-fungus Nudix hydrolase effector decaps mRNA in vitro and interferes with plant immune pathways. THE NEW PHYTOLOGIST 2023; 239:222-239. [PMID: 36631975 DOI: 10.1111/nph.18727] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 01/02/2023] [Indexed: 06/02/2023]
Abstract
To infect plants, pathogenic fungi secrete small proteins called effectors. Here, we describe the catalytic activity and potential virulence function of the Nudix hydrolase effector AvrM14 from the flax rust fungus (Melampsora lini). We completed extensive in vitro assays to characterise the enzymatic activity of the AvrM14 effector. Additionally, we used in planta transient expression of wild-type and catalytically dead AvrM14 versions followed by biochemical assays, phenotypic analysis and RNA sequencing to unravel how the catalytic activity of AvrM14 impacts plant immunity. AvrM14 is an extremely selective enzyme capable of removing the protective 5' cap from mRNA transcripts in vitro. Homodimerisation of AvrM14 promoted biologically relevant mRNA cap cleavage in vitro and this activity was conserved in related effectors from other Melampsora spp. In planta expression of wild-type AvrM14, but not the catalytically dead version, suppressed immune-related reactive oxygen species production, altered the abundance of some circadian-rhythm-associated mRNA transcripts and reduced the hypersensitive cell-death response triggered by the flax disease resistance protein M1. To date, the decapping of host mRNA as a virulence strategy has not been described beyond viruses. Our results indicate that some fungal pathogens produce Nudix hydrolase effectors with in vitro mRNA-decapping activity capable of interfering with plant immunity.
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Affiliation(s)
- Carl L McCombe
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Ann-Maree Catanzariti
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Julian R Greenwood
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Anna M Desai
- Plant and Microbial Biology Department, University of California, Berkeley, CA, 94720, USA
| | - Megan A Outram
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Daniel S Yu
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Daniel J Ericsson
- Australian Synchrotron, Macromolecular Crystallography, Clayton, Vic., 3168, Australia
| | - Steven E Brenner
- Plant and Microbial Biology Department, University of California, Berkeley, CA, 94720, USA
| | - Peter N Dodds
- Black Mountain Science and Innovation Park, CSIRO Agriculture and Food, Canberra, ACT, 2601, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Qld, 4072, Australia
| | - David A Jones
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Simon J Williams
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
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3
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Abstract
The 5'-terminal cap is a fundamental determinant of eukaryotic gene expression which facilitates cap-dependent translation and protects mRNAs from exonucleolytic degradation. Enzyme-directed hydrolysis of the cap (decapping) decisively affects mRNA expression and turnover, and is a heavily regulated event. Following the identification of the decapping holoenzyme (Dcp1/2) over two decades ago, numerous studies revealed the complexity of decapping regulation across species and cell types. A conserved set of Dcp1/2-associated proteins, implicated in decapping activation and molecular scaffolding, were identified through genetic and molecular interaction studies, and yet their exact mechanisms of action are only emerging. In this review, we discuss the prevailing models on the roles and assembly of decapping co-factors, with considerations of conservation across species and comparison across physiological contexts. We next discuss the functional convergences of decapping machineries with other RNA-protein complexes in cytoplasmic P bodies and compare current views on their impact on mRNA stability and translation. Lastly, we review the current models of decapping activation and highlight important gaps in our current understanding.
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Affiliation(s)
- Elva Vidya
- Goodman Cancer Institute, McGill University, Montréal, QC, Canada
- Department of Biochemistry, McGill University, Montréal, QC, Canada
| | - Thomas F. Duchaine
- Goodman Cancer Institute, McGill University, Montréal, QC, Canada
- Department of Biochemistry, McGill University, Montréal, QC, Canada
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4
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Peters JK, Tibble RW, Warminski M, Jemielity J, Gross JD. Structure of the poxvirus decapping enzyme D9 reveals its mechanism of cap recognition and catalysis. Structure 2022; 30:721-732.e4. [PMID: 35290794 PMCID: PMC9081138 DOI: 10.1016/j.str.2022.02.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 12/30/2021] [Accepted: 02/16/2022] [Indexed: 01/06/2023]
Abstract
Poxviruses encode decapping enzymes that remove the protective 5' cap from both host and viral mRNAs to commit transcripts for decay by the cellular exonuclease Xrn1. Decapping by these enzymes is critical for poxvirus pathogenicity by means of simultaneously suppressing host protein synthesis and limiting the accumulation of viral double-stranded RNA (dsRNA), a trigger for antiviral responses. Here we present a high-resolution structural view of the vaccinia virus decapping enzyme D9. This Nudix enzyme contains a domain organization different from other decapping enzymes in which a three-helix bundle is inserted into the catalytic Nudix domain. The 5' mRNA cap is positioned in a bipartite active site at the interface of the two domains. Specificity for the methylated guanosine cap is achieved by stacking between conserved aromatic residues in a manner similar to that observed in canonical cap-binding proteins VP39, eIF4E, and CBP20, and distinct from eukaryotic decapping enzyme Dcp2.
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5
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Kago G, Parrish S. The Mimivirus L375 Nudix enzyme hydrolyzes the 5' mRNA cap. PLoS One 2021; 16:e0245820. [PMID: 34582446 PMCID: PMC8478210 DOI: 10.1371/journal.pone.0245820] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 09/10/2021] [Indexed: 11/19/2022] Open
Abstract
The giant Mimivirus is a member of the nucleocytoplasmic large DNA viruses (NCLDV), a group of diverse viruses that contain double-stranded DNA (dsDNA) genomes that replicate primarily in eukaryotic hosts. Two members of the NCLDV, Vaccinia Virus (VACV) and African Swine Fever Virus (ASFV), both synthesize Nudix enzymes that have been shown to decap mRNA, a process thought to accelerate viral and host mRNA turnover and promote the shutoff of host protein synthesis. Mimivirus encodes two Nudix enzymes in its genome, denoted as L375 and L534. Importantly, L375 exhibits sequence similarity to ASFV-DP and eukaryotic Dcp2, two Nudix enzymes shown to possess mRNA decapping activity. In this work, we demonstrate that recombinant Mimivirus L375 cleaves the 5' m7GpppN mRNA cap, releasing m7GDP as a product. L375 did not significantly cleave mRNAs containing an unmethylated 5'GpppN cap, indicating that this enzyme specifically hydrolyzes methylated-capped transcripts. A point mutation in the L375 Nudix motif completely eliminated cap hydrolysis, showing that decapping activity is dependent on this motif. Addition of uncapped RNA significantly reduced L375 decapping activity, suggesting that L375 may recognize its substrate through interaction with the RNA body.
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Affiliation(s)
- Grace Kago
- Department of Biology, McDaniel College, Westminster, Maryland, United States of America
| | - Susan Parrish
- Department of Biology, McDaniel College, Westminster, Maryland, United States of America
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6
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Luo Y, Schofield JA, Na Z, Hann T, Simon MD, Slavoff SA. Discovery of cellular substrates of human RNA-decapping enzyme DCP2 using a stapled bicyclic peptide inhibitor. Cell Chem Biol 2020; 28:463-474.e7. [PMID: 33357462 DOI: 10.1016/j.chembiol.2020.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 10/29/2020] [Accepted: 12/04/2020] [Indexed: 01/23/2023]
Abstract
DCP2 is an RNA-decapping enzyme that controls the stability of human RNAs that encode factors functioning in transcription and the immune response. While >1,800 human DCP2 substrates have been identified, compensatory expression changes secondary to genetic ablation of DCP2 have complicated a complete mapping of its regulome. Cell-permeable, selective chemical inhibitors of DCP2 could provide a powerful tool to study DCP2 specificity. Here, we report phage display selection of CP21, a bicyclic peptide ligand to DCP2. CP21 has high affinity and selectivity for DCP2 and inhibits DCP2 decapping activity toward selected RNA substrates in human cells. CP21 increases formation of P-bodies, liquid condensates enriched in intermediates of RNA decay, in a manner that resembles the deletion or mutation of DCP2. We used CP21 to identify 76 previously unreported DCP2 substrates. This work demonstrates that DCP2 inhibition can complement genetic approaches to study RNA decay.
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Affiliation(s)
- Yang Luo
- Department of Chemistry, Yale University, New Haven, CT 06520, USA; Chemical Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Jeremy A Schofield
- Chemical Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06529, USA
| | - Zhenkun Na
- Department of Chemistry, Yale University, New Haven, CT 06520, USA; Chemical Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Tanja Hann
- Yale Combined Program in the Biological and Biomedical Sciences, Yale University, New Haven, CT 06520, USA
| | - Matthew D Simon
- Chemical Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06529, USA
| | - Sarah A Slavoff
- Department of Chemistry, Yale University, New Haven, CT 06520, USA; Chemical Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06529, USA.
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7
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Pelletier J, Schmeing TM, Sonenberg N. The multifaceted eukaryotic cap structure. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 12:e1636. [PMID: 33300197 DOI: 10.1002/wrna.1636] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/16/2020] [Accepted: 11/03/2020] [Indexed: 12/13/2022]
Abstract
The 5' cap structure is added onto RNA polymerase II transcripts soon after initiation of transcription and modulates several post-transcriptional regulatory events involved in RNA maturation. It is also required for stimulating translation initiation of many cytoplasmic mRNAs and serves to protect mRNAs from degradation. These functional properties of the cap are mediated by several cap binding proteins (CBPs) involved in nuclear and cytoplasmic gene expression steps. The role that CBPs play in gene regulation, as well as the biophysical nature by which they recognize the cap, is quite intricate. Differences in mechanisms of capping as well as nuances in cap recognition speak to the potential of targeting these processes for drug development. In this review, we focus on recent findings concerning the cap epitranscriptome, our understanding of cap binding by different CBPs, and explore therapeutic targeting of CBP-cap interaction. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Processing > Capping and 5' End Modifications Translation > Translation Mechanisms.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Department of Oncology, McGill University, Montreal, Quebec, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montreal, Quebec, Canada
| | - T Martin Schmeing
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montreal, Quebec, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
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8
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Frindert J, Kahloon MA, Zhang Y, Ahmed YL, Sinning I, Jäschke A. YvcI from Bacillus subtilis has in vitro RNA pyrophosphohydrolase activity. J Biol Chem 2019; 294:19967-19977. [PMID: 31740579 DOI: 10.1074/jbc.ra119.011485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 11/15/2019] [Indexed: 12/23/2022] Open
Abstract
RNA degradation is one of several ways for organisms to regulate gene expression. In bacteria, the removal of two terminal phosphate moieties as orthophosphate (Bacillus subtilis) or pyrophosphate (Escherichia coli) triggers ribonucleolytic decay of primary transcripts by 5'-monophosphate-dependent ribonucleases. In the soil-dwelling firmicute species B. subtilis, the RNA pyrophosphohydrolase BsRppH, a member of the Nudix family, triggers RNA turnover by converting primary transcripts to 5'-monophospate RNA. In addition to BsRppH, a source of redundant activity in B. subtilis has been proposed. Here, using recombinant protein expression and in vitro enzyme assays, we provide evidence for several additional RNA pyrophosphohydrolases, among them MutT, NudF, YmaB, and YvcI in B. subtilis We found that in vitro, YvcI converts RNA 5'-di- and triphosphates into monophosphates in the presence of manganese at neutral to slightly acidic pH. It preferred G-initiating RNAs and required at least one unpaired nucleotide at the 5'-end of its substrates, with the 5'-terminal nucleotide determining whether primarily ortho- or pyrophosphate is released. Exchanges of catalytically important glutamate residues in the Nudix motif impaired or abolished the enzymatic activity of YvcI. In summary, the results of our extensive in vitro biochemical characterization raise the possibility that YvcI is an additional RNA pyrophosphohydrolase in B. subtilis.
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Affiliation(s)
- Jens Frindert
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, D-69120 Heidelberg, Germany
| | - Masroor Ahmad Kahloon
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, D-69120 Heidelberg, Germany
| | - Yaqing Zhang
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, D-69120 Heidelberg, Germany
| | - Yasar Luqman Ahmed
- Heidelberg University Biochemistry Center, Heidelberg University, D-69120 Heidelberg, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center, Heidelberg University, D-69120 Heidelberg, Germany
| | - Andres Jäschke
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, D-69120 Heidelberg, Germany
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9
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Wurm JP, Sprangers R. Dcp2: an mRNA decapping enzyme that adopts many different shapes and forms. Curr Opin Struct Biol 2019; 59:115-123. [PMID: 31473440 PMCID: PMC6900585 DOI: 10.1016/j.sbi.2019.07.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 07/22/2019] [Accepted: 07/30/2019] [Indexed: 02/01/2023]
Abstract
Structure of the active state of the Dcp2 decapping enzyme. Insights into the structural states that are sampled in solution. Details regarding the intermolecular network that Dcp2 is embedded in.
Eukaryotic mRNAs contain a 5’ cap structure that protects the transcript against rapid exonucleolytic degradation. The regulation of cellular mRNA levels therefore depends on a precise control of the mRNA decapping pathways. The major mRNA decapping enzyme in eukaryotic cells is Dcp2. It is regulated by interactions with several activators, including Dcp1, Edc1, and Edc3, as well as by an autoinhibition mechanism. The structural and mechanistical characterization of Dcp2 complexes has long been impeded by the high flexibility and dynamic nature of the enzyme. Here we review recent insights into the catalytically active conformation of the mRNA decapping complex, the mode of action of decapping activators and the large interactions network that Dcp2 is embedded in.
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Affiliation(s)
- Jan Philip Wurm
- Department of Biophysics I, University of Regensburg, 93053, Regensburg, Germany.
| | - Remco Sprangers
- Department of Biophysics I, University of Regensburg, 93053, Regensburg, Germany.
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10
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Grudzien-Nogalska E, Wu Y, Jiao X, Cui H, Mateyak MK, Hart RP, Tong L, Kiledjian M. Structural and mechanistic basis of mammalian Nudt12 RNA deNADding. Nat Chem Biol 2019; 15:575-582. [PMID: 31101919 PMCID: PMC6527130 DOI: 10.1038/s41589-019-0293-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 03/18/2019] [Indexed: 11/21/2022]
Abstract
We recently demonstrated mammalian cells harbor NAD-capped mRNAs that are hydrolyzed by the DXO deNADding enzyme. Here we report the Nudix protein Nudt12 is a second mammalian deNADding enzyme structurally and mechanistically distinct from DXO and targeting different RNAs. Crystal structure of mouse Nudt12 in complex with the deNADding product AMP and three Mg2+ ions at 1.6 Å resolution provides exquisite insights into the molecular basis of the deNADding activity within the NAD pyrophosphate. Disruption of the Nudt12 gene stabilizes transfected NAD-capped RNA in cells and its endogenous NAD-capped mRNA targets are enriched in those encoding proteins involved in cellular energetics. Furthermore, exposure of cells to nutrient or environmental stress manifests changes in NAD-capped RNA levels that are selectively responsive to Nudt12 or DXO respectively, indicating an association of deNADding to cellular metabolism.
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Affiliation(s)
| | - Yixuan Wu
- Department Biological Sciences, Columbia University, New York, NY, USA
| | - Xinfu Jiao
- Department Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
| | - Huijuan Cui
- Department Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
| | - Maria K Mateyak
- Department Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
| | - Ronald P Hart
- Department Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
| | - Liang Tong
- Department Biological Sciences, Columbia University, New York, NY, USA.
| | - Megerditch Kiledjian
- Department Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA.
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11
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Charenton C, Graille M. mRNA decapping: finding the right structures. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2018.0164. [PMID: 30397101 DOI: 10.1098/rstb.2018.0164] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/24/2018] [Indexed: 12/14/2022] Open
Abstract
In eukaryotes, the elimination of the m7GpppN mRNA cap, a process known as decapping, is a critical, largely irreversible and highly regulated step of mRNA decay that withdraws the targeted mRNAs from the pool of translatable templates. The decapping reaction is catalysed by a multi-protein complex formed by the Dcp2 catalytic subunit and its Dcp1 cofactor, a holoenzyme that is poorly active on its own and needs several accessory proteins (Lsm1-7 complex, Pat1, Edc1-2, Edc3 and/or EDC4) to be fully efficient. Here, we discuss the several crystal structures of Dcp2 domains bound to various partners (proteins or small molecules) determined in the last couple of years that have considerably improved our current understanding of how Dcp2, assisted by its various activators, is recruited to its mRNA targets and adopts its active conformation upon substrate recognition. We also describe how, over the years, elegant integrative structural biology approaches combined to biochemistry and genetics led to the identification of the correct structure of the active Dcp1-Dcp2 holoenzyme among the many available conformations trapped by X-ray crystallography.This article is part of the theme issue '5' and 3' modifications controlling RNA degradation'.
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Affiliation(s)
- Clément Charenton
- Laboratoire de Biochimie, Ecole polytechnique, CNRS, Université Paris-Saclay, F-91128 Palaiseau cedex, France
| | - Marc Graille
- Laboratoire de Biochimie, Ecole polytechnique, CNRS, Université Paris-Saclay, F-91128 Palaiseau cedex, France
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12
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Grzela R, Nasilowska K, Lukaszewicz M, Tyras M, Stepinski J, Jankowska-Anyszka M, Bojarska E, Darzynkiewicz E. Hydrolytic activity of human Nudt16 enzyme on dinucleotide cap analogs and short capped oligonucleotides. RNA (NEW YORK, N.Y.) 2018; 24:633-642. [PMID: 29483298 PMCID: PMC5900562 DOI: 10.1261/rna.065698.118] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 02/20/2018] [Indexed: 05/30/2023]
Abstract
Human Nudt16 (hNudt16) is a member of the Nudix family of hydrolases, comprising enzymes catabolizing various substrates including canonical (d)NTPs, oxidized (d)NTPs, nonnucleoside polyphosphates, and capped mRNAs. Decapping activity of the Xenopus laevis (X29) Nudt16 homolog was observed in the nucleolus, with a high specificity toward U8 snoRNA. Subsequent studies have reported cytoplasmic localization of mammalian Nudt16 with cap hydrolysis activity initiating RNA turnover, similar to Dcp2. The present study focuses on hNudt16 and its hydrolytic activity toward dinucleotide cap analogs and short capped oligonucleotides. We performed a screening assay for potential dinucleotide and oligonucleotide substrates for hNudt16. Our data indicate that dinucleotide cap analogs and capped oligonucleotides containing guanine base in the first transcribed nucleotide are more susceptible to enzymatic digestion by hNudt16 than their counterparts containing adenine. Furthermore, unmethylated dinucleotides (GpppG and ApppG) and respective oligonucleotides (GpppG-16nt and GpppA-16nt) were hydrolyzed by hNudt16 with greater efficiency than were m7GpppG and m7GpppG-16nt. In conclusion, we found that hNudt16 hydrolysis of dinucleotide cap analogs and short capped oligonucleotides displayed a broader spectrum specificity than is currently known.
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Affiliation(s)
- Renata Grzela
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Karolina Nasilowska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-097 Warsaw, Poland
| | - Maciej Lukaszewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-097 Warsaw, Poland
| | - Michal Tyras
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Janusz Stepinski
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | | | - Elzbieta Bojarska
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Edward Darzynkiewicz
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-097 Warsaw, Poland
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13
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Scheller U, Pfisterer K, Uebe S, Ekici AB, Reis A, Jamra R, Ferrazzi F. Integrative bioinformatics analysis characterizing the role of EDC3 in mRNA decay and its association to intellectual disability. BMC Med Genomics 2018; 11:41. [PMID: 29685133 PMCID: PMC5914069 DOI: 10.1186/s12920-018-0358-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 04/04/2018] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Decapping of mRNA is an important step in the regulation of mRNA turnover and therefore of gene expression, which is a key process controlling development and homeostasis of all organisms. It has been shown that EDC3 plays a role in mRNA decapping, however its function is not well understood. Previously, we have associated a homozygous variant in EDC3 with autosomal recessive intellectual disability. Here, we investigate the functional role of EDC3. METHODS We performed transcriptome analyses in patients' samples. In addition, we established an EDC3 loss-of-function model using siRNA-based knockdown in the human neuroblastoma cell line SKNBE and carried out RNA sequencing. Integrative bioinformatics analyses were performed to identify EDC3-dependent candidate genes and/or pathways. RESULTS Our analyses revealed that 235 genes were differentially expressed in patients versus controls. In addition, AU-rich element (ARE)-containing mRNAs, whose degradation in humans has been suggested to involve EDC3, had higher fold changes than non-ARE-containing genes. The analysis of RNA sequencing data from the EDC3 in vitro loss-of-function model confirmed the higher fold changes of ARE-containing mRNAs compared to non-ARE-containing mRNAs and further showed an upregulation of long non-coding and coding RNAs. In total, 764 genes were differentially expressed. Integrative bioinformatics analyses of these genes identified dysregulated candidate pathways, including pathways related to synapses/coated vesicles and DNA replication/cell cycle. CONCLUSION Our data support the involvement of EDC3 in mRNA decay, including ARE-containing mRNAs, and suggest that EDC3 might be preferentially involved in the degradation of long coding and non-coding RNAs. Furthermore, our results associate ECD3 loss-of-function with synapses-related pathways. Collectively, our data provide novel information that might help elucidate the molecular mechanisms underlying the association of intellectual disability with the dysregulation of mRNA degradation.
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Affiliation(s)
- Ute Scheller
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
| | - Kathrin Pfisterer
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
| | - Steffen Uebe
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
| | - Arif B. Ekici
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
| | - André Reis
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
| | - Rami Jamra
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
- Institute of Human Genetics, University of Leipzig, Philipp-Rosenthal-Straße 55, 04103 Leipzig, Germany
| | - Fulvia Ferrazzi
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany
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14
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Mugridge JS, Tibble RW, Ziemniak M, Jemielity J, Gross JD. Structure of the activated Edc1-Dcp1-Dcp2-Edc3 mRNA decapping complex with substrate analog poised for catalysis. Nat Commun 2018; 9:1152. [PMID: 29559651 PMCID: PMC5861098 DOI: 10.1038/s41467-018-03536-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 02/22/2018] [Indexed: 11/17/2022] Open
Abstract
The conserved decapping enzyme Dcp2 recognizes and removes the 5′ eukaryotic cap from mRNA transcripts in a critical step of many cellular RNA decay pathways. Dcp2 is a dynamic enzyme that functions in concert with the essential activator Dcp1 and a diverse set of coactivators to selectively and efficiently decap target mRNAs in the cell. Here we present a 2.84 Å crystal structure of K. lactis Dcp1–Dcp2 in complex with coactivators Edc1 and Edc3, and with substrate analog bound to the Dcp2 active site. Our structure shows how Dcp2 recognizes cap substrate in the catalytically active conformation of the enzyme, and how coactivator Edc1 forms a three-way interface that bridges the domains of Dcp2 to consolidate the active conformation. Kinetic data reveal Dcp2 has selectivity for the first transcribed nucleotide during the catalytic step. The heterotetrameric Edc1–Dcp1–Dcp2–Edc3 structure shows how coactivators Edc1 and Edc3 can act simultaneously to activate decapping catalysis. The decapping enzyme Dcp2 removes the 5′ eukaryotic cap from mRNA transcripts and acts in concert with its essential activator Dcp1 and various coactivators. Here the authors present the structure of the fully-activated mRNA decapping complex, which reveals how Dcp2 recognizes the cap substrate and coactivators Edc1 and Edc3 activate catalysis.
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Affiliation(s)
- Jeffrey S Mugridge
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, 94158, USA
| | - Ryan W Tibble
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, 94158, USA.,Program in Chemistry and Chemical Biology, University of California, San Francisco, San Francisco, CA, 94158, USA
| | - Marcin Ziemniak
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089, Warsaw, Poland.,Centre of New Technologies, University of Warsaw, 02-097, Warsaw, Poland.,Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, 02-089, Warsaw, Poland
| | - Jacek Jemielity
- Centre of New Technologies, University of Warsaw, 02-097, Warsaw, Poland
| | - John D Gross
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, 94158, USA. .,Program in Chemistry and Chemical Biology, University of California, San Francisco, San Francisco, CA, 94158, USA.
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15
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Quintas A, Pérez-Núñez D, Sánchez EG, Nogal ML, Hentze MW, Castelló A, Revilla Y. Characterization of the African Swine Fever Virus Decapping Enzyme during Infection. J Virol 2017; 91:e00990-17. [PMID: 29021398 PMCID: PMC5709586 DOI: 10.1128/jvi.00990-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/03/2017] [Indexed: 01/13/2023] Open
Abstract
African swine fever virus (ASFV) infection is characterized by a progressive decrease in cellular protein synthesis with a concomitant increase in viral protein synthesis, though the mechanism by which the virus achieves this is still unknown. Decrease of cellular mRNA is observed during ASFV infection, suggesting that inhibition of cellular proteins is due to an active mRNA degradation process. ASFV carries a gene (Ba71V D250R/Malawi g5R) that encodes a decapping protein (ASFV-DP) that has a Nudix hydrolase motif and decapping activity in vitro Here, we show that ASFV-DP was expressed from early times and accumulated throughout the infection with a subcellular localization typical of the endoplasmic reticulum, colocalizing with the cap structure and interacting with the ribosomal protein L23a. ASFV-DP was capable of interaction with poly(A) RNA in cultured cells, primarily mediated by the N-terminal region of the protein. ASFV-DP also interacted with viral and cellular RNAs in the context of infection, and its overexpression in infected cells resulted in decreased levels of both types of transcripts. This study points to ASFV-DP as a viral decapping enzyme involved in both the degradation of cellular mRNA and the regulation of viral transcripts.IMPORTANCE Virulent ASFV strains cause a highly infectious and lethal disease in domestic pigs for which there is no vaccine. Since 2007, an outbreak in the Caucasus region has spread to Russia, jeopardizing the European pig population and making it essential to deepen knowledge about the virus. Here, we demonstrate that ASFV-DP is a novel RNA-binding protein implicated in the regulation of mRNA metabolism during infection, making it a good target for vaccine development.
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Affiliation(s)
- Ana Quintas
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Universidad Autónoma de Madrid, Madrid, Spain
| | - Daniel Pérez-Núñez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Universidad Autónoma de Madrid, Madrid, Spain
| | - Elena G Sánchez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Universidad Autónoma de Madrid, Madrid, Spain
| | - Maria L Nogal
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Universidad Autónoma de Madrid, Madrid, Spain
| | | | - Alfredo Castelló
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Yolanda Revilla
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Universidad Autónoma de Madrid, Madrid, Spain
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16
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Domashevskiy AV, Rodriguez DJ, Gunawardana D, Goss DJ. Preparation of Functional, Fluorescently Labeled mRNA Capped with Anthraniloyl-m(7)GpppG. Methods Mol Biol 2017; 1428:61-75. [PMID: 27236792 DOI: 10.1007/978-1-4939-3625-0_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Fluorescent mRNA molecules offer a wide range of applications for studying capping/decapping reactions, translation, and other biophysical studies. Furthermore, fluorescent tags prove invaluable for tracking RNA molecules in cells. Here, we describe an efficient synthesis of a fluorescent cap analog, anthranioyl-GTP, its purification, and in vitro cap labeling of transcribed mRNA catalyzed by the recombinant vaccinia capping enzyme to produce anthranioyl-m(7)GpppG-capped RNA.
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Affiliation(s)
- Artem V Domashevskiy
- Department of Sciences, John Jay College of Criminal Justice, City University of New York, New York, NY, USA.
| | - David J Rodriguez
- Department of Sciences, John Jay College of Criminal Justice, City University of New York, New York, NY, USA
| | - Dilantha Gunawardana
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia.,Department of Botany, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Dixie J Goss
- Department of Chemistry, Hunter College, City University of New York, New York, NY, USA
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17
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Affiliation(s)
- Jeff Coller
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, Ohio USA
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18
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Valkov E, Jonas S, Weichenrieder O. Mille viae in eukaryotic mRNA decapping. Curr Opin Struct Biol 2017; 47:40-51. [PMID: 28591671 DOI: 10.1016/j.sbi.2017.05.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 05/22/2017] [Indexed: 12/20/2022]
Abstract
Cellular mRNA levels are regulated via rates of transcription and decay. Since the removal of the mRNA 5'-cap by the decapping enzyme DCP2 is generally an irreversible step towards decay, it requires regulation. Control of DCP2 activity is likely effected by two interdependent means: by conformational control of the DCP2-DCP1 complex, and by assembly control of the decapping network, an array of mutually interacting effector proteins. Here, we compare three recent and conformationally distinct crystal structures of the DCP2-DCP1 decapping complex in the presence of substrate analogs and decapping enhancers and we discuss alternative substrate recognition modes for the catalytic domain of DCP2. Together with structure-based insight into decapping network assembly, we propose that DCP2-mediated decapping follows more than one path.
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Affiliation(s)
- Eugene Valkov
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Stefanie Jonas
- Institute of Biochemistry, ETH Zürich, Otto-Stern Weg 3, 8093 Zürich, Switzerland.
| | - Oliver Weichenrieder
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
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19
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Changes in conformational equilibria regulate the activity of the Dcp2 decapping enzyme. Proc Natl Acad Sci U S A 2017; 114:6034-6039. [PMID: 28533364 DOI: 10.1073/pnas.1704496114] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Crystal structures of enzymes are indispensable to understanding their mechanisms on a molecular level. It, however, remains challenging to determine which structures are adopted in solution, especially for dynamic complexes. Here, we study the bilobed decapping enzyme Dcp2 that removes the 5' cap structure from eukaryotic mRNA and thereby efficiently terminates gene expression. The numerous Dcp2 structures can be grouped into six states where the domain orientation between the catalytic and regulatory domains significantly differs. Despite this wealth of structural information it is not possible to correlate these states with the catalytic cycle or the activity of the enzyme. Using methyl transverse relaxation-optimized NMR spectroscopy, we demonstrate that only three of the six domain orientations are present in solution, where Dcp2 adopts an open, a closed, or a catalytically active state. We show how mRNA substrate and the activator proteins Dcp1 and Edc1 influence the dynamic equilibria between these states and how this modulates catalytic activity. Importantly, the active state of the complex is only stably formed in the presence of both activators and the mRNA substrate or the m7GDP decapping product, which we rationalize based on a crystal structure of the Dcp1:Dcp2:Edc1:m7GDP complex. Interestingly, we find that the activating mechanisms in Dcp2 also result in a shift of the substrate specificity from bacterial to eukaryotic mRNA.
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20
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Li J, Wang W, He Y, Li Y, Yan EZ, Zhang K, Irvine DJ, Hammond PT. Structurally Programmed Assembly of Translation Initiation Nanoplex for Superior mRNA Delivery. ACS NANO 2017; 11:2531-2544. [PMID: 28157292 PMCID: PMC5629916 DOI: 10.1021/acsnano.6b08447] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Messenger RNA (mRNA) represents a promising class of nucleic-acid-based therapeutics. While numerous nanocarriers have been developed for mRNA delivery, the inherent labile nature of mRNA results in a very low transfection efficiency and poor expression of desired protein. Here we preassemble the mRNA translation initiation structure through an inherent molecular recognition between 7-methylguanosine (m7G)-capped mRNA and eukaryotic initiation factor 4E (eIF4E) protein to form ribonucleoproteins (RNPs), thereby mimicking the first step of protein synthesis inside cells. Subsequent electrostatic stabilization of RNPs with structurally tunable cationic carriers leads to nanosized complexes (nanoplexes), which elicit high levels of mRNA transfection in different cell types by enhancing intracellular mRNA stability and protein synthesis. By investigating a family of synthetic polypeptides bearing different side group arrangements of cationic charge, we find that the molecular structure modulates the nanoscale distance between the mRNA strand and the eIF4E protein inside the nanoplex, which directly impacts the enhancement of mRNA transfection. To demonstrate the biomedical potential of this approach, we use this approach to introduce mRNA/eIF4E nanoplexes to murine dendritic cells, resulting in increased activation of cytotoxic CD8 T cells ex vivo. More importantly, eIF4E enhances gene expression in lungs following a systemic delivery of luciferase mRNA/eIF4E in mice. Collectively, this bioinspired molecular assembly method could lead to a new paradigm of gene delivery.
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Affiliation(s)
- Jiahe Li
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Wade Wang
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Yanpu He
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Yingzhong Li
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Emily Z. Yan
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Ketian Zhang
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Darrell J. Irvine
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Paula T. Hammond
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
- Correspondence: David H. Koch Professor in Engineering, Bayer Chair Professor of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States.
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21
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Warminski M, Sikorski PJ, Kowalska J, Jemielity J. Applications of Phosphate Modification and Labeling to Study (m)RNA Caps. Top Curr Chem (Cham) 2017; 375:16. [PMID: 28116583 PMCID: PMC5396385 DOI: 10.1007/s41061-017-0106-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 01/10/2017] [Indexed: 02/07/2023]
Abstract
The cap is a natural modification present at the 5' ends of eukaryotic messenger RNA (mRNA), which because of its unique structural features, mediates essential biological functions during the process of gene expression. The core structural feature of the mRNA cap is an N7-methylguanosine moiety linked by a 5'-5' triphosphate chain to the first transcribed nucleotide. Interestingly, other RNA 5' end modifications structurally and functionally resembling the m7G cap have been discovered in different RNA types and in different organisms. All these structures contain the 'inverted' 5'-5' oligophosphate bridge, which is necessary for interaction with specific proteins and also serves as a cleavage site for phosphohydrolases regulating RNA turnover. Therefore, cap analogs containing oligophosphate chain modifications or carrying spectroscopic labels attached to phosphate moieties serve as attractive molecular tools for studies on RNA metabolism and modification of natural RNA properties. Here, we review chemical, enzymatic, and chemoenzymatic approaches that enable preparation of modified cap structures and RNAs carrying such structures, with emphasis on phosphate-modified mRNA cap analogs and their potential applications.
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Affiliation(s)
- Marcin Warminski
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089, Warsaw, Poland
| | - Pawel J Sikorski
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Joanna Kowalska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089, Warsaw, Poland.
| | - Jacek Jemielity
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland.
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22
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Structural basis of mRNA-cap recognition by Dcp1-Dcp2. Nat Struct Mol Biol 2016; 23:987-994. [PMID: 27694842 PMCID: PMC5113729 DOI: 10.1038/nsmb.3301] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/01/2016] [Indexed: 11/21/2022]
Abstract
Removal of the 5′ cap on mRNA by the decapping enzyme Dcp2 is a critical step in 5′-to-3′ mRNA decay. Understanding the structural basis of Dcp2 activity has been a significant challenge because Dcp2 is dynamic, with weak affinity for cap substrate. Here we present a 2.6-Å-resolution crystal structure of a heterotrimer of fission yeast Dcp2, its essential activator Dcp1, and the human NMD cofactor PNRC2, in complex with a tight-binding cap analog. Cap binding is accompanied by a conformational change of Dcp2 to form a composite nucleotide binding site using conserved residues on the catalytic and regulatory domains. Kinetic analysis of PNRC2 reveals a conserved short linear motif enhances both substrate affinity and the catalytic step of decapping. These findings explain why Dcp2 requires a conformational change for efficient catalysis and reveals that coactivators can promote RNA binding and the catalytic step of decapping, possibly through different conformational states.
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23
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Structure of the active form of Dcp1-Dcp2 decapping enzyme bound to m 7GDP and its Edc3 activator. Nat Struct Mol Biol 2016; 23:982-986. [PMID: 27694841 DOI: 10.1038/nsmb.3300] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 09/01/2016] [Indexed: 01/19/2023]
Abstract
Elimination of the 5' cap of eukaryotic mRNAs, known as decapping, is considered to be a crucial, irreversible and highly regulated step required for the rapid degradation of mRNA by Xrn1, the major cytoplasmic 5'-3' exonuclease. Decapping is accomplished by the recruitment of a protein complex formed by the Dcp2 catalytic subunit and its Dcp1 cofactor. However, this complex has a low intrinsic enzymatic activity and requires several accessory proteins such as the Lsm1-7 complex, Pat1, Edc1-Edc2 and/or Edc3 to be fully active. Here we present the crystal structure of the active form of the yeast Kluyveromyces lactis Dcp1-Dcp2 enzyme bound to its product (m7GDP) and its potent activator Edc3. This structure of the Dcp1-Dcp2 complex bound to a cap analog further explains previously published data on substrate binding and provides hints as to the mechanism of Edc3-mediated Dcp2 activation.
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24
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Grudzien-Nogalska E, Kiledjian M. New insights into decapping enzymes and selective mRNA decay. WILEY INTERDISCIPLINARY REVIEWS-RNA 2016; 8. [PMID: 27425147 DOI: 10.1002/wrna.1379] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 06/23/2016] [Accepted: 06/27/2016] [Indexed: 01/04/2023]
Abstract
Removal of the 5' end cap is a critical determinant controlling mRNA stability and efficient gene expression. Removal of the cap is exquisitely controlled by multiple direct and indirect regulators that influence association with the cap and the catalytic step. A subset of these factors directly stimulate activity of the decapping enzyme, while others influence remodeling of factors bound to mRNA and indirectly stimulate decapping. Furthermore, the components of the general decapping machinery can also be recruited by mRNA-specific regulatory proteins to activate decapping. The Nudix hydrolase, Dcp2, identified as a first decapping enzyme, cleaves capped mRNA and initiates 5'-3' degradation. Extensive studies on Dcp2 led to broad understanding of its activity and the regulation of transcript specific decapping and decay. Interestingly, seven additional Nudix proteins possess intrinsic decapping activity in vitro and at least two, Nudt16 and Nudt3, are decapping enzymes that regulate mRNA stability in cells. Furthermore, a new class of decapping proteins within the DXO family preferentially function on incompletely capped mRNAs. Importantly, it is now evident that each of the characterized decapping enzymes predominantly modulates only a subset of mRNAs, suggesting the existence of multiple decapping enzymes functioning in distinct cellular pathways. WIREs RNA 2017, 8:e1379. doi: 10.1002/wrna.1379 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Ewa Grudzien-Nogalska
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
| | - Megerditch Kiledjian
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA
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25
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Rhoads RE. Synthetic mRNA: Production, Introduction into Cells, and Physiological Consequences. Methods Mol Biol 2016; 1428:3-27. [PMID: 27236789 DOI: 10.1007/978-1-4939-3625-0_1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recent advances have made it possible to synthesize mRNA in vitro that is relatively stable when introduced into mammalian cells, has a diminished ability to activate the innate immune response against exogenous (virus-like) RNA, and can be efficiently translated into protein. Synthetic methods have also been developed to produce mRNA with unique investigational properties such as photo-cross-linking, fluorescence emission, and attachment of ligands through click chemistry. Synthetic mRNA has been proven effective in numerous applications beneficial for human health such as immunizing patients against cancer and infections diseases, alleviating diseases by restoring deficient proteins, converting somatic cells to pluripotent stem cells to use in regenerative medicine therapies, and engineering the genome by making specific alterations in DNA. This introductory chapter provides background information relevant to the following 20 chapters of this volume that present protocols for these applications of synthetic mRNA.
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Affiliation(s)
- Robert E Rhoads
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA, 71130-3932, USA.
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26
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Siwaszek A, Ukleja M, Dziembowski A. Proteins involved in the degradation of cytoplasmic mRNA in the major eukaryotic model systems. RNA Biol 2015; 11:1122-36. [PMID: 25483043 DOI: 10.4161/rna.34406] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The process of mRNA decay and surveillance is considered to be one of the main posttranscriptional gene expression regulation platforms in eukaryotes. The degradation of stable, protein-coding transcripts is normally initiated by removal of the poly(A) tail followed by 5'-cap hydrolysis and degradation of the remaining mRNA body by Xrn1. Alternatively, the exosome complex degrades mRNA in the 3'>5'direction. The newly discovered uridinylation-dependent pathway, which is present in many different organisms, also seems to play a role in bulk mRNA degradation. Simultaneously, to avoid the synthesis of incorrect proteins, special cellular machinery is responsible for the removal of faulty transcripts via nonsense-mediated, no-go, non-stop or non-functional 18S rRNA decay. This review is focused on the major eukaryotic cytoplasmic mRNA degradation pathways showing many similarities and pointing out main differences between the main model-species: yeast, Drosophila, plants and mammals.
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Affiliation(s)
- Aleksandra Siwaszek
- a Institute of Biochemistry and Biophysics ; Polish Academy of Sciences ; Warsaw , Poland
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27
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Zytek M, Kowalska J, Lukaszewicz M, Wojtczak BA, Zuberek J, Ferenc-Mrozek A, Darzynkiewicz E, Niedzwiecka A, Jemielity J. Towards novel efficient and stable nuclear import signals: synthesis and properties of trimethylguanosine cap analogs modified within the 5',5'-triphosphate bridge. Org Biomol Chem 2015; 12:9184-99. [PMID: 25296894 DOI: 10.1039/c4ob01579g] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A trimethylguanosine (TMG) cap is present at the 5' end of several small nuclear and nucleolar RNAs. Recently, it has been reported that the TMG cap is a potential nuclear import signal for nucleus-targeting therapeutic nucleic acids and proteins. The import is mediated by recognition of the TMG cap by the snRNA transporting protein, snurportin1. This work describes the synthesis and properties of a series of dinucleotide TMG cap (m3(2,2,7)GpppG) analogs modified in the 5',5'-triphosphate bridge as tools to study TMG cap-dependent biological processes. The bridge was altered at different positions by introducing either bridging (imidodiphosphate, O to NH and methylenebisphosphonate, O to CH2) or non-bridging (phosphorothioate, O to S and boranophosphate, O to BH3) modifications, or by elongation to tetraphosphate. The stability of novel analogs in blood serum was studied to reveal that the α,β-bridging O to NH substitution (m3(2,2,7)GppNHpG) confers the highest resistance. Short RNAs capped with analogs containing α,β-bridging (m3(2,2,7)GppNHpG) or β-non-bridging (m3(2,2,7)GppSpG D2) modifications were resistant to decapping pyrophosphatase, hNudt16. Preliminary studies on binding by human snurportin1 revealed that both O to NH and O to S substitutions support this binding. Due to favorable properties in all three assays, m3(2,2,7)GppNHpG was selected as a promising candidate for further studies on the efficiency of the TMG cap as a nuclear import signal.
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Affiliation(s)
- Malgorzata Zytek
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland.
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28
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Gunawardana D, Domashevskiy AV, Gayler KR, Goss DJ. Efficient preparation and properties of mRNAs containing a fluorescent cap analog: Anthraniloyl-m(7)GpppG. ACTA ACUST UNITED AC 2015; 3:e988538. [PMID: 26779415 DOI: 10.4161/21690731.2014.988538] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/30/2014] [Accepted: 11/12/2014] [Indexed: 11/19/2022]
Abstract
A method has been developed for synthesising fluorescently labeled capped mRNA. The method incorporates a single fluorescent molecule as part of the 5'-mRNA or oligonucleotide cap site. The fluorescent molecule, Ant-m(7)GTP is specifically incorporated into the cap site to yield Ant-m(7)GpppG-capped mRNA or oligonucleotide. Efficient capping was observed with 60-100% of the RNA transcripts capped with the fluorescent molecule. The Ant-m(7)G derivative, which has been previously shown to interact with the eukaryotic cap binding protein eIF4E, is shown in this paper to be a substrate for the Vaccinia capping enzyme and the DCP2 decapping enzyme from Arabidopsis. Further, the Ant-m(7)GTP-capped RNA is readily translated. This Ant-m(7)GTP-capped RNA provides an important tool for monitoring capping reactions, translation, and biophysical studies.
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Affiliation(s)
- Dilantha Gunawardana
- Department of Biochemistry and Molecular Biology; Bio21 Molecular Science and Biotechnology Institute; University of Melbourne, Parkville; Victoria, Australia; Present address: Department of Botany; University of Sri Jayewardenepura; Soratha Mawatha, Nugegoda, Sri Lanka
| | - Artem V Domashevskiy
- Department of Sciences; John Jay College of Criminal Justice; City University of New York ; New York, NY USA
| | - Ken R Gayler
- Department of Biochemistry and Molecular Biology; Bio21 Molecular Science and Biotechnology Institute; University of Melbourne, Parkville ; Victoria, Australia
| | - Dixie J Goss
- Department of Chemistry and Graduate Center; Hunter College; City University of New York ; New York, NY USA
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Suh SS, Hwang J, Park M, Park SY, Ryu TK, Lee S, Lee TK. Hypoxia-modulated gene expression profiling in sea urchin (Strongylocentrotus nudus) immune cells. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2014; 109:63-69. [PMID: 25164204 DOI: 10.1016/j.ecoenv.2014.08.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 08/07/2014] [Accepted: 08/11/2014] [Indexed: 06/03/2023]
Abstract
Hypoxia is an issue that affects ocean coastal waters worldwide. It has severe consequences for marine organisms, including death and rapid adaptive changes in metabolic organization. Although some aquatic animals are routinely exposed and resistant to severe environmental hypoxia, others such as sea urchins (Strongylocentrotus nudus) have a limited capacity to withstand this stress. In this study, hypoxia induced a significant increase in the number of red spherule cells among coelomocytes, which function as immune cells. This suggests that sea urchin immune cells could be used as a biological indicator of hypoxic stress. In the current study, we used cDNA microarrays to investigate the differential expression patterns of hypoxia-regulated genes to better understand the molecular mechanisms underlying the response of immune cells to hypoxia. Surprisingly, the predominant major effect of hypoxia was the widespread suppression of gene expression. In particular, the expression of RNA helicase and GATA-4/5/6 was decreased significantly in response to hypoxia, even in field conditions, suggesting that they could be utilized as sensitive bioindicators of hypoxic stress in the sea urchin.
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Affiliation(s)
- Sung-Suk Suh
- South Sea Environment Research Department, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea
| | - Jinik Hwang
- South Sea Environment Research Department, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea
| | - Mirye Park
- South Sea Environment Research Department, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea
| | - So Yun Park
- South Sea Environment Research Department, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea
| | - Tae Kwon Ryu
- Accident Prevention and Assessment Division, Yuseong-gu, Daejeon, 305-343, Republic of Korea
| | - Sukchan Lee
- Department of Genetic Engineering, SungKyunKwan University, Suwon 440-746, Republic of Korea
| | - Taek-Kyun Lee
- South Sea Environment Research Department, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea.
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Aglietti RA, Floor SN, McClendon CL, Jacobson MP, Gross JD. Active site conformational dynamics are coupled to catalysis in the mRNA decapping enzyme Dcp2. Structure 2013; 21:1571-80. [PMID: 23911090 DOI: 10.1016/j.str.2013.06.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 06/22/2013] [Accepted: 06/25/2013] [Indexed: 11/16/2022]
Abstract
Removal of the 5' cap structure by Dcp2 is a major step in several 5'-3' mRNA decay pathways. The activity of Dcp2 is enhanced by Dcp1 and bound coactivators, yet the details of how these interactions are linked to chemistry are poorly understood. Here, we report three crystal structures of the catalytic Nudix hydrolase domain of Dcp2 that demonstrate binding of a catalytically essential metal ion, and enzyme kinetics are used to identify several key active site residues involved in acid/base chemistry of decapping. Using nuclear magnetic resonance and molecular dynamics, we find that a conserved metal binding loop on the catalytic domain undergoes conformational changes during the catalytic cycle. These findings describe key events during the chemical step of decapping, suggest local active site conformational changes are important for activity, and provide a framework to explain stimulation of catalysis by the regulatory domain of Dcp2 and associated coactivators.
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Affiliation(s)
- Robin A Aglietti
- Program in Chemistry and Chemical Biology, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
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31
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Song MG, Bail S, Kiledjian M. Multiple Nudix family proteins possess mRNA decapping activity. RNA (NEW YORK, N.Y.) 2013; 19:390-9. [PMID: 23353937 PMCID: PMC3677249 DOI: 10.1261/rna.037309.112] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 12/20/2012] [Indexed: 05/23/2023]
Abstract
RNA decapping is an important contributor to gene expression and is a critical determinant of mRNA decay. The recent demonstration that mammalian cells harbor at least two distinct decapping enzymes that preferentially modulate a subset of mRNAs raises the intriguing possibility of whether additional decapping enzymes exist. Because both known decapping proteins, Dcp2 and Nudt16, are members of the Nudix hydrolase family, we set out to determine whether other members of this family of proteins also contain intrinsic RNA decapping activity. Here we demonstrate that six additional mouse Nudix proteins--Nudt2, Nudt3, Nudt12, Nudt15, Nudt17, and Nudt19--have varying degrees of decapping activity in vitro on both monomethylated and unmethylated capped RNAs. The decapping products from Nudt17 and Nudt19 were analogous to Dcp2 and predominantly generated m⁷GDP, while cleavage by Nudt2, Nudt3, Nudt12, and Nudt15 was more pleiotropic and generated both m⁷GMP and m⁷GDP. Interestingly, all six Nudix proteins as well as both Dcp2 and Nudt16 could hydrolyze the cap of an unmethylated capped RNA, indicating that decapping enzymes may be less constrained for the presence of the methyl moiety. Investigation of Saccharomyces cerevisiae Nudix proteins revealed that the yeast homolog of Nudt3, Ddp1p, also possesses decapping activity in vitro. Moreover, the bacterial Nudix pyrophosphohydrolase RppH displayed RNA decapping activity and released m⁷GDP product comparable to Dcp2, indicating that decapping is an evolutionarily conserved activity that preceded mammalian cap formation. These findings demonstrate that multiple Nudix family hydrolases may function in mRNA decapping and mRNA stability.
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Affiliation(s)
| | | | - Megerditch Kiledjian
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854-8082, USA
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32
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McLennan AG. Substrate ambiguity among the nudix hydrolases: biologically significant, evolutionary remnant, or both? Cell Mol Life Sci 2013; 70:373-85. [PMID: 23184251 PMCID: PMC11113851 DOI: 10.1007/s00018-012-1210-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/01/2012] [Accepted: 11/05/2012] [Indexed: 12/20/2022]
Abstract
Many members of the nudix hydrolase family exhibit considerable substrate multispecificity and ambiguity, which raises significant issues when assessing their functions in vivo and gives rise to errors in database annotation. Several display low antimutator activity when expressed in bacterial tester strains as well as some degree of activity in vitro towards mutagenic, oxidized nucleotides such as 8-oxo-dGTP. However, many of these show greater activity towards other nucleotides such as ADP-ribose or diadenosine tetraphosphate (Ap(4)A). The antimutator activities have tended to gain prominence in the literature, whereas they may in fact represent the residual activity of an ancestral antimutator enzyme that has become secondary to the more recently evolved major activity after gene duplication. Whether any meaningful antimutagenic function has also been retained in vivo requires very careful assessment. Then again, other examples of substrate ambiguity may indicate as yet unexplored regulatory systems. For example, bacterial Ap(4)A hydrolases also efficiently remove pyrophosphate from the 5' termini of mRNAs, suggesting a potential role for Ap(4)A in the control of bacterial mRNA turnover, while the ability of some eukaryotic mRNA decapping enzymes to degrade IDP and dIDP or diphosphoinositol polyphosphates (DIPs) may also be indicative of new regulatory networks in RNA metabolism. DIP phosphohydrolases also degrade diadenosine polyphosphates and inorganic polyphosphates, suggesting further avenues for investigation. This article uses these and other examples to highlight the need for a greater awareness of the possible significance of substrate ambiguity among the nudix hydrolases as well as the need to exert caution when interpreting incomplete analyses.
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Affiliation(s)
- Alexander G McLennan
- Institute of Integrative Biology, University of Liverpool, Biosciences Building, Crown St., Liverpool, L69 7ZB, UK.
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33
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Chuang TW, Chang WL, Lee KM, Tarn WY. The RNA-binding protein Y14 inhibits mRNA decapping and modulates processing body formation. Mol Biol Cell 2013; 24:1-13. [PMID: 23115303 PMCID: PMC3530774 DOI: 10.1091/mbc.e12-03-0217] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 10/22/2012] [Accepted: 10/24/2012] [Indexed: 01/12/2023] Open
Abstract
The exon-junction complex (EJC) deposited on a newly spliced mRNA plays an important role in subsequent mRNA metabolic events. Here we show that an EJC core heterodimer, Y14/Magoh, specifically associates with mRNA-degradation factors, including the mRNA-decapping complex and exoribonucleases, whereas another core factor, eIF4AIII/MLN51, does not. We also demonstrate that Y14 interacts directly with the decapping factor Dcp2 and the 5' cap structure of mRNAs via different but overlapping domains and that Y14 inhibits the mRNA-decapping activity of Dcp2 in vitro. Accordingly, overexpression of Y14 prolongs the half-life of a reporter mRNA. Therefore Y14 may function independently of the EJC in preventing mRNA decapping and decay. Furthermore, we observe that depletion of Y14 disrupts the formation of processing bodies, whereas overexpression of a phosphomimetic Y14 considerably increases the number of processing bodies, perhaps by sequestering the mRNA-degradation factors. In conclusion, this report provides unprecedented evidence for a role of Y14 in regulating mRNA degradation and processing body formation and reinforces the influence of phosphorylation of Y14 on its activity in postsplicing mRNA metabolism.
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Affiliation(s)
- Tzu-Wei Chuang
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Wei-Lun Chang
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Kuo-Ming Lee
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Woan-Yuh Tarn
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
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Arribas-Layton M, Wu D, Lykke-Andersen J, Song H. Structural and functional control of the eukaryotic mRNA decapping machinery. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:580-9. [PMID: 23287066 DOI: 10.1016/j.bbagrm.2012.12.006] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 12/15/2012] [Accepted: 12/17/2012] [Indexed: 01/12/2023]
Abstract
The regulation of mRNA degradation is critical for proper gene expression. Many major pathways for mRNA decay involve the removal of the 5' 7-methyl guanosine (m(7)G) cap in the cytoplasm to allow for 5'-to-3' exonucleolytic decay. The most well studied and conserved eukaryotic decapping enzyme is Dcp2, and its function is aided by co-factors and decapping enhancers. A subset of these factors can act to enhance the catalytic activity of Dcp2, while others might stimulate the remodeling of proteins bound to the mRNA substrate that may otherwise inhibit decapping. Structural studies have provided major insights into the mechanisms by which Dcp2 and decapping co-factors activate decapping. Additional mRNA decay factors can function by recruiting components of the decapping machinery to target mRNAs. mRNA decay factors, decapping factors, and mRNA substrates can be found in cytoplasmic foci named P bodies that are conserved in eukaryotes, though their function remains unknown. In addition to Dcp2, other decapping enzymes have been identified, which may serve to supplement the function of Dcp2 or act in independent decay or quality control pathways. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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35
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Abstract
Messenger RNAs transcribed by RNA polymerase II are modified at their 5'-end by the cotranscriptional addition of a 7-methylguanosine (m(7)G) cap. The cap is an important modulator of gene expression and the mechanism and components involved in its removal have been extensively studied. At least two decapping enzymes, Dcp2 and Nudt16, and an array of decapping regulatory proteins remove the m(7)G cap from an mRNA exposing the 5'-end to exonucleolytic decay. In contrast, relatively less is known about the decay of mRNAs that may be aberrantly capped. The recent demonstration that the Saccharomyces cerevisiae Rai1 protein selectively hydrolyzes aberrantly capped mRNAs provides new insights into the modulation of mRNA that lack a canonical m(7)G cap 5'-end. Whether an mRNA is uncapped or capped but missing the N7 methyl moiety, Rai1 hydrolyzes its 5'-end to generate an mRNA with a 5' monophosphate. Interestingly, Rai1 heterodimerizes with the Rat1 5'-3' exoribonuclease, which subsequently degrades the 5'-end monophosphorylated mRNA. Importantly, Rat1 stimulates the 5'-end hydrolysis activities of Rai1 to generate a 5'-end unprotected mRNA substrate for Rat1 and, in turn, Rai1 stimulates the activity of Rat1. The Rai1-Rat1 heterodimer functions as a molecular motor to detect and degrade mRNAs with aberrant caps and defines a novel quality control mechanism that ensures mRNA 5'-end integrity. The increase in aberrantly capped mRNA population following nutritional stress in S. cerevisiae demonstrates the presence of aberrantly capped mRNAs in cells and further reinforces the functional significance of the Rai1 in ensuring mRNA 5'-end integrity.
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Affiliation(s)
- Megerditch Kiledjian
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA.
| | - Mi Zhou
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
| | - Xinfu Jiao
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
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36
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Su W, Slepenkov S, Grudzien-Nogalska E, Kowalska J, Kulis M, Zuberek J, Lukaszewicz M, Darzynkiewicz E, Jemielity J, Rhoads RE. Translation, stability, and resistance to decapping of mRNAs containing caps substituted in the triphosphate chain with BH3, Se, and NH. RNA (NEW YORK, N.Y.) 2011; 17:978-88. [PMID: 21447710 PMCID: PMC3078746 DOI: 10.1261/rna.2430711] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Accepted: 02/15/2011] [Indexed: 05/23/2023]
Abstract
Decapping is an essential step in multiple pathways of mRNA degradation. Previously, we synthesized mRNAs containing caps that were resistant to decapping, both to dissect the various pathways for mRNA degradation and to stabilize mRNA for more sustained protein expression. mRNAs containing an α-β CH(2) group are resistant to in vitro cleavage by the decapping enzyme hDcp2 but poorly translated. mRNAs containing an S substitution at the β-phosphate are well translated but only partially resistant to hDcp2. We now describe seven new cap analogs substituted at the β-phosphate with BH(3) or Se, or substituted at either the α-β or β-γ O with NH. The analogs differ in affinity for eIF4E and efficiency of in vitro incorporation into mRNA by T7 RNA polymerase. Luciferase mRNAs capped with these analogs differ in resistance to hDcp2 hydrolysis in vitro, translational efficiency in rabbit reticulocyte lysate and in HeLa cells, and stability in HeLa cells. Whereas mRNAs capped with m(2)(7,2'-O)Gpp(S)pG were previously found to have the most favorable properties of translational efficiency and stability in mammalian cells, mRNAs capped with m(7)Gpp(BH3)pm(7)G are translated with the same efficiency but are more stable. Interestingly, some mRNAs exhibit a lag of up to 60 min before undergoing first-order decay (t(1/2) ≅ 25 min). Only mRNAs that are efficiently capped, resistant to decapping in vitro, and actively translated have long lag phases.
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Affiliation(s)
- Wei Su
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, USA
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37
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Lu G, Zhang J, Li Y, Li Z, Zhang N, Xu X, Wang T, Guan Z, Gao GF, Yan J. hNUDT16: a universal decapping enzyme for small nucleolar RNA and cytoplasmic mRNA. Protein Cell 2011; 2:64-73. [PMID: 21337011 DOI: 10.1007/s13238-011-1009-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 01/19/2011] [Indexed: 11/26/2022] Open
Abstract
Human NUDT16 (hNUDT16) is a decapping enzyme initially identified as the human homolog to the Xenopus laevis X29. As a metalloenzyme, hNUDT16 relies on divalent cations for its cap-hydrolysis activity to remove m⁷GDP and m²²⁷GDP from RNAs. Metal also determines substrate specificity of the enzyme. So far, only U8 small nucleolar RNA (snoRNA) has been identified as the substrate of hNUDT16 in the presence of Mg²(+). Here we demonstrate that besides U8, hNUDT16 can also actively cleave the m⁷GDP cap from mRNAs in the presence of Mg²(+) or Mn²(+). We further show that hNUDT16 does not preferentially recognize U8 or mRNA substrates by our cross-inhibition and quantitative decapping assays. In addition, our mutagenesis analysis identifies several key residues involved in hydrolysis and confirms the key role of the REXXEE motif in catalysis. Finally an investigation into the subcellular localization of hNUDT16 revealed its abundance in both cytoplasm and nucleus. These findings extend the substrate spectrum of hNUDT16 beyond snoRNAs to also include mRNA, demonstrating the pleiotropic decapping activity of hNUDT16.
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Affiliation(s)
- Guangwen Lu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology (CASPMI), Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, 100101, China
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38
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Song MG, Li Y, Kiledjian M. Multiple mRNA decapping enzymes in mammalian cells. Mol Cell 2010; 40:423-32. [PMID: 21070968 DOI: 10.1016/j.molcel.2010.10.010] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 07/10/2010] [Accepted: 08/25/2010] [Indexed: 01/18/2023]
Abstract
Regulation of RNA degradation plays an important role in the control of gene expression. One mechanism of eukaryotic mRNA decay proceeds through an initial deadenylation followed by 5' end decapping and exonucleolytic decay. Dcp2 is currently believed to be the only cytoplasmic decapping enzyme responsible for decapping of all mRNAs. Here we report that Dcp2 protein modestly contributes to bulk mRNA decay and surprisingly is not detectable in a subset of mouse and human tissues. Consistent with these findings, a hypomorphic knockout of Dcp2 had no adverse consequences in mice. In contrast, the previously reported Xenopus nucleolar decapping enzyme, Nudt16, is an ubiquitous cytoplasmic decapping enzyme in mammalian cells. Like Dcp2, Nudt16 also regulates the stability of a subset of mRNAs including a member of the motin family of proteins involved in angiogenesis, Angiomotin-like 2. These data demonstrate mammalian cells possess multiple mRNA decapping enzymes, including Nudt16 to regulate mRNA turnover.
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Affiliation(s)
- Man-Gen Song
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854, USA
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39
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Ling SHM, Qamra R, Song H. Structural and functional insights into eukaryotic mRNA decapping. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 2:193-208. [PMID: 21957006 DOI: 10.1002/wrna.44] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The control of messenger RNA (mRNA) translation and degradation is important in regulation of eukaryotic gene expression. In the general and specialized mRNA decay pathways which involve 5(') →3(') decay, decapping is the central step because it is the controlling gate preceding the actual degradation of mRNA and is a site of numerous control inputs. Removal of the cap structure is catalyzed by a decapping holoenzyme composed of the catalytic Dcp2 subunit and the coactivator Dcp1. Decapping is regulated by decapping activators and inhibitors. Recent structural and kinetics studies indicated that Dcp1 and the substrate RNA promote the closed form of the enzyme and the catalytic step of decapping is rate limiting and accelerated by Dcp1. The conformational change between the open and closed decapping enzyme is important for controlling decapping, and regulation of this transition has been proposed to be a checkpoint for determining the fate of mRNAs. Here we summarize the past and recent advances on the structural and functional studies of protein factors involved in regulating mRNA decapping.
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Affiliation(s)
- Sharon H M Ling
- Laboratory of Macromolecular Structure, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673
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40
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Jiao X, Xiang S, Oh C, Martin CE, Tong L, Kiledjian M. Identification of a quality-control mechanism for mRNA 5'-end capping. Nature 2010; 467:608-11. [PMID: 20802481 PMCID: PMC2948066 DOI: 10.1038/nature09338] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 07/06/2010] [Indexed: 11/11/2022]
Abstract
The 7-methylguanosine cap structure at the 5′-end of eukaryotic mRNAs is a critical determinant of their stability and translational efficiency1–3. It is generally believed that 5’-end capping is a constitutive process that occurs during mRNA maturation and lacks the need for a quality control mechanism to ensure its fidelity. We recently reported that the yeast Rai1 protein has pyrophosphohydrolase activity towards mRNAs lacking a 5’-end cap4. Here we show that, in vitro as well as in yeast cells, Rai1 possess a novel decapping endonuclease activity that can also remove the entire cap structure dinucleotide from an mRNA. Interestingly this activity is targeted preferentially towards mRNAs with unmethylated caps in contrast to the canonical decapping enzyme, Dcp2, that targets mRNAs with a methylated cap. Capped but unmethylated mRNAs generated in yeast cells with a defect in the methyltransferase gene are more stable in a rai1 gene disrupted background. Moreover, rai1Δ yeast cells with wild-type capping enzymes show significant accumulation of mRNAs with 5’-end capping defects under nutritional stress conditions of glucose or amino acid starvation. These findings provide evidence that 5’-end capping is not a constitutive process that necessarily always proceeds to completion and demonstrates that Rai1 plays an essential role in clearing mRNAs with aberrant 5’-end caps. We propose Rai1 is involved in a hitherto-uncharacterized quality control process that ensures mRNA 5’-end integrity by an aberrant-cap mediated mRNA decay mechanism.
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Affiliation(s)
- Xinfu Jiao
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854, USA
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41
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Floor SN, Jones BN, Hernandez GA, Gross JD. A split active site couples cap recognition by Dcp2 to activation. Nat Struct Mol Biol 2010; 17:1096-101. [PMID: 20711189 PMCID: PMC2933276 DOI: 10.1038/nsmb.1879] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 06/18/2010] [Indexed: 01/25/2023]
Abstract
Decapping by Dcp2 is an essential step in 5'-to-3' mRNA decay. In yeast, decapping requires an open-to-closed transition in Dcp2, though the link between closure and catalysis remains elusive. Here we show using NMR that cap binds conserved residues on both the catalytic and regulatory domains of Dcp2. Lesions in the cap-binding site on the regulatory domain reduce the catalytic step by two orders of magnitude and block the formation of the closed state, whereas Dcp1 enhances the catalytic step by a factor of 10 and promotes closure. We conclude that closure occurs during the rate-limiting catalytic step of decapping, juxtaposing the cap-binding region of each domain to form a composite active site. This work suggests a model for regulation of decapping where coactivators trigger decapping by stabilizing a labile composite active site.
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Affiliation(s)
- Stephen N Floor
- Graduate Group in Biophysics, University of California, San Francisco, California, USA
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42
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Li Y, Kiledjian M. Regulation of mRNA decapping. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:253-65. [PMID: 21935889 DOI: 10.1002/wrna.15] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Decapping is a critical step in the control of mRNA stability and the regulation of gene expression. Two major decapping enzymes involved in mRNA turnover have been identified, each functioning in one of the two exonucleolytic mRNA decay pathways in eukaryotic cells. The Dcp2 protein cleaves capped mRNA and initiates 5' to 3' degradation; the scavenger decapping enzyme, DcpS, hydrolyzes the cap structure generated by the 3' to 5' decay pathway. Consistent with the important role of decapping in gene expression, cap hydrolysis is exquisitely controlled by multiple regulators that influence association with the cap and the catalytic step. In this review, we will discuss the functions of the two different decapping enzymes, their regulation by cis-elements and trans-factors, and the potential role of the decapping enzymes in human neurological disorders.
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Affiliation(s)
- You Li
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854-8082, USA
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43
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Parrish S, Hurchalla M, Liu SW, Moss B. The African swine fever virus g5R protein possesses mRNA decapping activity. Virology 2009; 393:177-82. [PMID: 19695654 PMCID: PMC3392020 DOI: 10.1016/j.virol.2009.07.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/23/2009] [Indexed: 01/29/2023]
Abstract
The African Swine Fever Virus (ASFV) encodes a single Nudix enzyme in its genome, termed the g5R protein (g5Rp). Nudix phosphohydrolases cleave a variety of substrates, such as nucleotides and diphosphoinositol polyphosphates. Previously, ASFV g5Rp was shown to hydrolyze diphosphoinositol polyphosphates and GTP, but was unable to cleave methylated mRNA cap analogues. In vaccinia virus (VACV), a distant relative of ASFV, the D9 and D10 Nudix enzymes were shown to cleave the mRNA cap, but only when the cap was attached to an RNA body. Here, we show that recombinant ASFV g5Rp hydrolyzes the mRNA cap when tethered to an RNA moiety, liberating m(7)GDP as a product. Mutations in the Nudix motif abolished mRNA decapping activity, confirming that g5Rp was responsible for cap cleavage. The decapping activity of g5Rp was potently inhibited by excess uncapped RNA but not by methylated cap analogues, suggesting that substrate recognition occurs by RNA binding.
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Affiliation(s)
- Susan Parrish
- McDaniel College, 2 College Hill, Eaton Hall, Room 212, Westminster, MD 21157, USA.
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44
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Structure and biological function of the RNA pyrophosphohydrolase BdRppH from Bdellovibrio bacteriovorus. Structure 2009; 17:472-81. [PMID: 19278661 DOI: 10.1016/j.str.2008.12.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 12/08/2008] [Accepted: 12/29/2008] [Indexed: 11/22/2022]
Abstract
Until recently, the mechanism of mRNA decay in bacteria was thought to be different from that of eukaryotes. This paradigm changed with the discovery that RppH (ORF176/NudH/YgdP), an Escherichia coli enzyme that belongs to the Nudix superfamily, is an RNA pyrophosphohydrolase that initiates mRNA decay by cleaving pyrophosphate from the 5'-triphosphate. Here we report the 1.9 Angstroms resolution structure of the Nudix hydrolase BdRppH from Bdellovibrio bacteriovorus, a bacterium that feeds on other Gram-negative bacteria. Based on the structure of the enzyme alone and in complex with GTP-Mg2+, we propose a mode of RNA binding similar to that of the nuclear decapping enzyme from Xenopus laevis, X29. In additional experiments, we show that BdRppH can indeed function in vitro and in vivo as an RNA pyrophosphohydrolase. These findings set the basis for the identification of possible decapping enzymes in other bacteria.
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Li Y, Ho ES, Gunderson SI, Kiledjian M. Mutational analysis of a Dcp2-binding element reveals general enhancement of decapping by 5'-end stem-loop structures. Nucleic Acids Res 2009; 37:2227-37. [PMID: 19233875 PMCID: PMC2673433 DOI: 10.1093/nar/gkp087] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
mRNA decapping is a critical step in the control of mRNA stability and gene expression and is carried out by the Dcp2 protein. Dcp2 is an RNA-binding protein that must bind the RNA in order to recognize the cap for hydrolysis. We previously demonstrated that a 60 nucleotide (nt) element at the 5' end of the mRNA encoding Rrp41 is preferentially bound and decapped by Dcp2. Here, we demonstrate that enhanced decapping of this element is dependent on the structural integrity of its first 33 nt and not its primary sequence. The structure consists of a stem-loop positioned <10 nt from the 5' end of the mRNA. The generality of a stem-loop structure in enhanced Dcp2-mediated decapping was underscored by the identification of additional potential Dcp2 substrate mRNAs by a global analysis of human mRNAs containing a similar predicted stem-loop structure at their respective 5' end. These studies suggest a general role for 5' stem-loops in enhancing decapping activity and the utilization of this structure as a predictive tool for Dcp2 target substrates. These studies also demonstrate that Dcp2 alone in the absence of additional proteins can preferentially associate with and modulate mRNA decapping.
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Affiliation(s)
- You Li
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854-8082, USA
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Identification of a cytoplasmic complex that adds a cap onto 5'-monophosphate RNA. Mol Cell Biol 2009; 29:2155-67. [PMID: 19223470 DOI: 10.1128/mcb.01325-08] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endonuclease decay of nonsense-containing beta-globin mRNA in erythroid cells generates 5'-truncated products that were reported previously to have a cap or caplike structure. We confirmed that this 5' modification is indistinguishable from the cap on full-length mRNA, and Western blotting, immunoprecipitation, and active-site labeling identified a population of capping enzymes in the cytoplasm of erythroid and nonerythroid cells. Cytoplasmic capping enzyme sediments in a 140-kDa complex that contains a kinase which, together with capping enzyme, converts 5'-monophosphate RNA into 5'-GpppX RNA. Capping enzyme shows diffuse and punctate staining throughout the cytoplasm, and its staining does not overlap with P bodies or stress granules. Expression of inactive capping enzyme in a form that is restricted to the cytoplasm reduced the ability of cells to recover from oxidative stress, thus supporting a role for capping in the cytoplasm and suggesting that some mRNAs may be stored in an uncapped state.
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Xiang S, Cooper-Morgan A, Jiao X, Kiledjian M, Manley JL, Tong L. Structure and function of the 5'-->3' exoribonuclease Rat1 and its activating partner Rai1. Nature 2009; 458:784-8. [PMID: 19194460 PMCID: PMC2739979 DOI: 10.1038/nature07731] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Accepted: 12/18/2008] [Indexed: 11/09/2022]
Abstract
The 5’→3’ exoribonucleases (XRNs) comprise a large family of conserved enzymes in eukaryotes with crucial functions in RNA metabolism and RNA interference1–5. XRN2, or Rat1 in yeast6, functions primarily in the nucleus and also plays an important role in transcription termination by RNA polymerase II (Pol II)7–14. Rat1 exoribonuclease activity is stimulated by the protein Rai115, 16. Here we report the crystal structure at 2.2 Å resolution of S. pombe Rat1 in complex with Rai1, as well as the structures of Rai1 and its murine homolog DOM3Z alone at 2.0 Å resolution. The structures reveal the molecular mechanism for the activation of Rat1 by Rai1 and for the exclusive exoribonuclease activity of Rat1. Biochemical studies confirm these observations, and show that Rai1 allows Rat1 to more effectively degrade RNAs with stable secondary structure. There are large differences in the active site landscape of Rat1 compared to related and PIN (PilT N-terminus) domain-containing nucleases17–20. Unexpectedly, we identified a large pocket in Rai1 and DOM3Z that contains highly conserved residues, including three acidic side chains that coordinate a divalent cation. Mutagenesis and biochemical studies demonstrate that Rai1 possesses pyrophosphohydrolase activity towards 5’ triphosphorylated RNA. Such an activity is important for mRNA degradation in bacteria21, but ours is the first demonstration of this activity in eukaryotes and suggests that Rai1/DOM3Z may have additional important functions in RNA metabolism.
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Affiliation(s)
- Song Xiang
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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Franks TM, Lykke-Andersen J. The control of mRNA decapping and P-body formation. Mol Cell 2009; 32:605-15. [PMID: 19061636 DOI: 10.1016/j.molcel.2008.11.001] [Citation(s) in RCA: 321] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Indexed: 01/24/2023]
Abstract
mRNA decapping is a critical step in eukaryotic cytoplasmic mRNA turnover. Cytoplasmic mRNA decapping is catalyzed by Dcp2 in conjunction with its coactivator Dcp1 and is stimulated by decapping enhancer proteins. mRNAs associated with the decapping machinery can assemble into cytoplasmic mRNP granules called processing bodies (PBs). Evidence suggests that PB-associated mRNPs are translationally repressed and can be degraded or stored for subsequent translation. However, whether mRNP assembly into a PB is important for translational repression, decapping, or decay has remained controversial. Here, we discuss the regulation of decapping machinery recruitment to specific mRNPs and how their assembly into PBs is governed by the relative rates of translational repression, mRNP multimerization, and mRNA decay.
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Affiliation(s)
- Tobias M Franks
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
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Floor SN, Jones BN, Gross JD. Control of mRNA decapping by Dcp2: An open and shut case? RNA Biol 2008; 5:189-92. [PMID: 18971632 DOI: 10.4161/rna.6859] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
mRNA decapping by Dcp2 is a critical step in several major eukaryotic mRNA decay pathways. Dcp2 forms the catalytic core of a mRNP that is configured for processing diverse substrates by pathway-specific activators. Here we elaborate a model of catalysis by Dcp2 which posits that activity is controlled by a conformational equilibrium between an open, inactive and closed, active form of the enzyme. Structural studies on yeast Dcp2 indicate that the general activator Dcp1 and substrate promote the closed form of the enzyme. Kinetic studies indicate the catalytic step of decapping is rate-limiting and accelerated by Dcp1. We propose that regulation of conformational transitions in Dcp2 during a rate-limiting step after assembly of the decapping mRNP provides a checkpoint for determining if an mRNA is degraded or recycled to translation.
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Affiliation(s)
- Stephen N Floor
- Graduate Group in Biophysics, University of California, San Francisco, California 94158-2517, USA
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Taylor MJ, Peculis BA. Evolutionary conservation supports ancient origin for Nudt16, a nuclear-localized, RNA-binding, RNA-decapping enzyme. Nucleic Acids Res 2008; 36:6021-34. [PMID: 18820299 PMCID: PMC2566886 DOI: 10.1093/nar/gkn605] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Nudt16p is a nuclear RNA decapping protein initially identified in Xenopus (X29) and known to exist in mammals. Here, we identified putative orthologs in 57 different organisms ranging from humans to Cnidaria (anemone/coral). In vitro analysis demonstrated the insect ortholog can bind RNA and hydrolyze the m(7)G cap from the 5'-end of RNAs indicating the Nudt16 gene product is functionally conserved across metazoans. This study also identified a closely related paralogous protein, known as Syndesmos, which resulted from a gene duplication that occurred in the tetrapod lineage near the amniote divergence. While vertebrate Nudt16p is a nuclear RNA decapping protein, Syndesmos is associated with the cytoplasmic membrane in tetrapods. Syndesmos is inactive for RNA decapping but retains RNA-binding activity. This structure/function analysis demonstrates evolutionary conservation of the ancient Nudt16 protein suggesting the existence and maintenance of a nuclear RNA degradation pathway in metazoans.
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Affiliation(s)
- Melissa J Taylor
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
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