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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Montemayor EJ, Virta JM, Hayes SM, Nomura Y, Brow DA, Butcher SE. Molecular basis for the distinct cellular functions of the Lsm1-7 and Lsm2-8 complexes. RNA (NEW YORK, N.Y.) 2020; 26:1400-1413. [PMID: 32518066 PMCID: PMC7491322 DOI: 10.1261/rna.075879.120] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Accepted: 06/03/2020] [Indexed: 05/04/2023]
Abstract
Eukaryotes possess eight highly conserved Lsm (like Sm) proteins that assemble into circular, heteroheptameric complexes, bind RNA, and direct a diverse range of biological processes. Among the many essential functions of Lsm proteins, the cytoplasmic Lsm1-7 complex initiates mRNA decay, while the nuclear Lsm2-8 complex acts as a chaperone for U6 spliceosomal RNA. It has been unclear how these complexes perform their distinct functions while differing by only one out of seven subunits. Here, we elucidate the molecular basis for Lsm-RNA recognition and present four high-resolution structures of Lsm complexes bound to RNAs. The structures of Lsm2-8 bound to RNA identify the unique 2',3' cyclic phosphate end of U6 as a prime determinant of specificity. In contrast, the Lsm1-7 complex strongly discriminates against cyclic phosphates and tightly binds to oligouridylate tracts with terminal purines. Lsm5 uniquely recognizes purine bases, explaining its divergent sequence relative to other Lsm subunits. Lsm1-7 loads onto RNA from the 3' end and removal of the Lsm1 carboxy-terminal region allows Lsm1-7 to scan along RNA, suggesting a gated mechanism for accessing internal binding sites. These data reveal the molecular basis for RNA binding by Lsm proteins, a fundamental step in the formation of molecular assemblies that are central to eukaryotic mRNA metabolism.
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Affiliation(s)
- Eric J Montemayor
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
| | - Johanna M Virta
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Samuel M Hayes
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Yuichiro Nomura
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - David A Brow
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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3
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Vindry C, Weil D, Standart N. Pat1 RNA-binding proteins: Multitasking shuttling proteins. WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 10:e1557. [PMID: 31231973 DOI: 10.1002/wrna.1557] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 05/02/2019] [Accepted: 05/07/2019] [Indexed: 12/11/2022]
Abstract
Post-transcriptional regulation of gene expression is largely achieved at the level of splicing in the nucleus, and translation and mRNA decay in the cytosol. While the regulation may be global, through the direct inhibition of central factors, such as the spliceosome, translation initiation factors and mRNA decay enzymes, in many instances transcripts bearing specific sequences or particular features are regulated by RNA-binding factors which mobilize or impede recruitment of these machineries. This review focuses on the Pat1 family of RNA-binding proteins, conserved from yeast to man, that enhance the removal of the 5' cap by the decapping enzyme Dcp1/2, leading to mRNA decay and also have roles in translational repression. Like Dcp1/2, other decapping coactivators, including DDX6 and Edc3, and translational repressor proteins, Pat1 proteins are enriched in cytoplasmic P-bodies, which have a principal role in mRNA storage. They also concentrate in nuclear Cajal-bodies and splicing speckles and in man, impact splice site choice in some pre-mRNAs. Pivotal to these functions is the association of Pat1 proteins with distinct heptameric Lsm complexes: the cytosolic Pat1/Lsm1-7 complex mediates mRNA decay and the nuclear Pat1/Lsm2-8 complex alternative splicing. This dual role of human Pat1b illustrates the power of paralogous complexes to impact distinct processes in separate compartments. The review highlights our recent findings that Pat1b mediates the decay of AU-rich mRNAs, which are particularly enriched in P-bodies, unlike the decapping activator DDX6, which acts on GC-rich mRNAs, that tend to be excluded from P-bodies, and discuss the implications for mRNA decay pathways. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNRNA Processing > Splicing Regulation/Alternative Splicing Translation > Translation Regulation.
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Affiliation(s)
- Caroline Vindry
- Centre International de Recherche en Infectiologie, CIRI, Lyon, France
| | - Dominique Weil
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire de Biologie du Développement, Paris, France
| | - Nancy Standart
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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4
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Chowdhury A, Kalurupalle S, Tharun S. Mutagenic Analysis of the C-Terminal Extension of Lsm1. PLoS One 2016; 11:e0158876. [PMID: 27434131 PMCID: PMC4951014 DOI: 10.1371/journal.pone.0158876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 06/23/2016] [Indexed: 11/18/2022] Open
Abstract
The Sm-like proteins (also known as Lsm proteins) are ubiquitous in nature and exist as hexa or heptameric RNA binding complexes. They are characterized by the presence of the Sm-domain. The Lsm1 through Lsm7 proteins are highly conserved in eukaryotes and they form a hetero-octameric complex together with the protein Pat1. The Lsm1-7-Pat1 complex plays a key role in mRNA decapping and 3’-end protection and therefore is required for normal mRNA decay rates in vivo. Lsm1 is a key subunit that is critical for the unique RNA binding properties of this complex. We showed earlier that unlike most Sm-like proteins, Lsm1 uniquely requires both its Sm domain and its C-terminal extension to contribute to the function of the Lsm1-7-Pat1 complex and that the C-terminal segment can associate with the rest of the complex and support the function even in trans. The studies presented here identify a set of residues at the very C-terminal end of Lsm1 to be functionally important and suggest that these residues support the function of the Lsm1-7-Pat1 complex by facilitating RNA binding either directly or indirectly.
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Affiliation(s)
- Ashis Chowdhury
- Department of Biochemistry, Uniformed Services University of the Health Sciences (USUHS), 4301, Jones Bridge Road, Bethesda, MD, 20814–4799, United States of America
| | - Swathi Kalurupalle
- Department of Biochemistry, Uniformed Services University of the Health Sciences (USUHS), 4301, Jones Bridge Road, Bethesda, MD, 20814–4799, United States of America
| | - Sundaresan Tharun
- Department of Biochemistry, Uniformed Services University of the Health Sciences (USUHS), 4301, Jones Bridge Road, Bethesda, MD, 20814–4799, United States of America
- * E-mail:
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5
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Jungfleisch J, Chowdhury A, Alves-Rodrigues I, Tharun S, Díez J. The Lsm1-7-Pat1 complex promotes viral RNA translation and replication by differential mechanisms. RNA (NEW YORK, N.Y.) 2015; 21:1469-79. [PMID: 26092942 PMCID: PMC4509936 DOI: 10.1261/rna.052209.115] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 05/11/2015] [Indexed: 05/20/2023]
Abstract
The Lsm1-7-Pat1 complex binds to the 3' end of cellular mRNAs and promotes 3' end protection and 5'-3' decay. Interestingly, this complex also specifically binds to cis-acting regulatory sequences of viral positive-strand RNA genomes promoting their translation and subsequent recruitment from translation to replication. Yet, how the Lsm1-7-Pat1 complex regulates these two processes remains elusive. Here, we show that Lsm1-7-Pat1 complex acts differentially in these processes. By using a collection of well-characterized lsm1 mutant alleles and a system that allows the replication of Brome mosaic virus (BMV) in yeast we show that the Lsm1-7-Pat1 complex integrity is essential for both, translation and recruitment. However, the intrinsic RNA-binding ability of the complex is only required for translation. Consistent with an RNA-binding-independent function of the Lsm1-7-Pat1 complex on BMV RNA recruitment, we show that the BMV 1a protein, the sole viral protein required for recruitment, interacts with this complex in an RNA-independent manner. Together, these results support a model wherein Lsm1-7-Pat1 complex binds consecutively to BMV RNA regulatory sequences and the 1a protein to promote viral RNA translation and later recruitment out of the host translation machinery to the viral replication complexes.
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Affiliation(s)
- Jennifer Jungfleisch
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Ashis Chowdhury
- Department of Biochemistry, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland 20814-4799, USA
| | - Isabel Alves-Rodrigues
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Sundaresan Tharun
- Department of Biochemistry, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland 20814-4799, USA
| | - Juana Díez
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
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6
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Dimastrogiovanni D, Fröhlich KS, Bandyra KJ, Bruce HA, Hohensee S, Vogel J, Luisi BF. Recognition of the small regulatory RNA RydC by the bacterial Hfq protein. eLife 2014; 3. [PMID: 25551292 PMCID: PMC4337610 DOI: 10.7554/elife.05375] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 12/29/2014] [Indexed: 01/24/2023] Open
Abstract
Bacterial small RNAs (sRNAs) are key elements of regulatory networks that modulate gene expression. The sRNA RydC of Salmonella sp. and Escherichia coli is an example of this class of riboregulators. Like many other sRNAs, RydC bears a ‘seed’ region that recognises specific transcripts through base-pairing, and its activities are facilitated by the RNA chaperone Hfq. The crystal structure of RydC in complex with E. coli Hfq at a 3.48 Å resolution illuminates how the protein interacts with and presents the sRNA for target recognition. Consolidating the protein–RNA complex is a host of distributed interactions mediated by the natively unstructured termini of Hfq. Based on the structure and other data, we propose a model for a dynamic effector complex comprising Hfq, small RNA, and the cognate mRNA target. DOI:http://dx.doi.org/10.7554/eLife.05375.001 A crucial step in the production of proteins is the translation of messenger RNA molecules. Other RNA molecules called small RNAs are also involved in this process: these small RNAs bind to the messenger RNA molecules to either increase or decrease the production of proteins. Bacteria and other microorganisms use small RNA molecules to help them respond to stress conditions and to changes in their environment, such as fluctuations in temperature or the availability of nutrients. The ability to rapidly adapt to these changes enables bacteria to withstand harmful conditions and to make efficient use of resources available to them. Many small RNA molecules use a protein called Hfq to help them interact with their target messenger RNAs. In some cases this protein protects the small RNA molecules when they are not bound to their targets. Hfq also helps the small RNA to bind to the messenger RNA, and then recruits other enzymes that eventually degrade the complex formed by the different RNA molecules. Previous research has shown that six Hfq subunits combine to form a ring-shaped structure and has also provided some clues about the way in which Hfq can recognise a short stretch of a small RNA molecule, but the precise details of the interaction between them are not fully understood. Now Dimastrogiovanni et al. have used a technique called X-ray crystallography to visualize the interaction between Hfq and a small RNA molecule called RydC. These experiments reveal that a particular region of RydC adopts a structure known as a pseudoknot and that this structure is critical for the interactions between the RydC molecules and the Hfq ring. Dimastrogiovanni et al. find that one RydC molecule interacts with one Hfq ring, and they identify the contact points between the RydC molecule and different regions of the Hfq ring. Based on this information, Dimastrogiovanni et al. propose a model for how the RydC:Hfq complex is likely to interact with a messenger RNA molecule. The next step will be to test this model in experiments. DOI:http://dx.doi.org/10.7554/eLife.05375.002
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Affiliation(s)
| | - Kathrin S Fröhlich
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Katarzyna J Bandyra
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Heather A Bruce
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Susann Hohensee
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Jörg Vogel
- Institute for Molecular Infection Biology, University of Würzburg, Würzburg, Germany
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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7
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Chowdhury A, Kalurupalle S, Tharun S. Pat1 contributes to the RNA binding activity of the Lsm1-7-Pat1 complex. RNA (NEW YORK, N.Y.) 2014; 20:1465-75. [PMID: 25035297 PMCID: PMC4138329 DOI: 10.1261/rna.045252.114] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 06/03/2014] [Indexed: 05/20/2023]
Abstract
A major mRNA decay pathway in eukaryotes is initiated by deadenylation followed by decapping of the oligoadenylated mRNAs and subsequent 5'-to-3' exonucleolytic degradation of the capless mRNA. In this pathway, decapping is a rate-limiting step that requires the hetero-octameric Lsm1-7-Pat1 complex to occur at normal rates in vivo. This complex is made up of the seven Sm-like proteins, Lsm1 through Lsm7, and the Pat1 protein. It binds RNA and has a unique binding preference for oligoadenylated RNAs over polyadenylated RNAs. Such binding ability is crucial for its mRNA decay function in vivo. In order to determine the contribution of Pat1 to the function of the Lsm1-7-Pat1 complex, we compared the RNA binding properties of the Lsm1-7 complex purified from pat1Δ cells and purified Pat1 fragments with that of the wild-type Lsm1-7-Pat1 complex. Our studies revealed that both the Lsm1-7 complex and purified Pat1 fragments have very low RNA binding activity and are impaired in the ability to recognize the oligo(A) tail on the RNA. However, reconstitution of the Lsm1-7-Pat1 complex from these components restored these abilities. We also observed that Pat1 directly contacts RNA in the context of the Lsm1-7-Pat1 complex. These studies suggest that the unique RNA binding properties and the mRNA decay function of the Lsm1-7-Pat1 complex involve cooperation of residues from both Pat1 and the Lsm1-7 ring. Finally our studies also revealed that the middle domain of Pat1 is essential for the interaction of Pat1 with the Lsm1-7 complex in vivo.
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Affiliation(s)
- Ashis Chowdhury
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Swathi Kalurupalle
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
| | - Sundaresan Tharun
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
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8
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Jalkanen AL, Coleman SJ, Wilusz J. Determinants and implications of mRNA poly(A) tail size--does this protein make my tail look big? Semin Cell Dev Biol 2014; 34:24-32. [PMID: 24910447 DOI: 10.1016/j.semcdb.2014.05.018] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 05/31/2014] [Indexed: 12/22/2022]
Abstract
While the phenomenon of polyadenylation has been well-studied, the dynamics of poly(A) tail size and its impact on transcript function and cell biology are less well-appreciated. The goal of this review is to encourage readers to view the poly(A) tail as a dynamic, changeable aspect of a transcript rather than a simple static entity that marks the 3' end of an mRNA. This could open up new angles of regulation in the post-transcriptional control of gene expression throughout development, differentiation and cancer.
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Affiliation(s)
- Aimee L Jalkanen
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA
| | - Stephen J Coleman
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA
| | - Jeffrey Wilusz
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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9
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Kim HJ, Raphael AR, LaDow ES, McGurk L, Weber RA, Trojanowski JQ, Lee VMY, Finkbeiner S, Gitler AD, Bonini NM. Therapeutic modulation of eIF2α phosphorylation rescues TDP-43 toxicity in amyotrophic lateral sclerosis disease models. Nat Genet 2014; 46:152-60. [PMID: 24336168 PMCID: PMC3934366 DOI: 10.1038/ng.2853] [Citation(s) in RCA: 288] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 11/22/2013] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal, late-onset neurodegenerative disease primarily affecting motor neurons. A unifying feature of many proteins associated with ALS, including TDP-43 and ataxin-2, is that they localize to stress granules. Unexpectedly, we found that genes that modulate stress granules are strong modifiers of TDP-43 toxicity in Saccharomyces cerevisiae and Drosophila melanogaster. eIF2α phosphorylation is upregulated by TDP-43 toxicity in flies, and TDP-43 interacts with a central stress granule component, polyA-binding protein (PABP). In human ALS spinal cord neurons, PABP accumulates abnormally, suggesting that prolonged stress granule dysfunction may contribute to pathogenesis. We investigated the efficacy of a small molecule inhibitor of eIF2α phosphorylation in ALS models. Treatment with this inhibitor mitigated TDP-43 toxicity in flies and mammalian neurons. These findings indicate that the dysfunction induced by prolonged stress granule formation might contribute directly to ALS and that compounds that mitigate this process may represent a novel therapeutic approach.
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Affiliation(s)
- Hyung-Jun Kim
- 1] Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. [2]
| | - Alya R Raphael
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Eva S LaDow
- Gladstone Institute of Neurological Disease, San Francisco, California, USA
| | - Leeanne McGurk
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ross A Weber
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Virginia M-Y Lee
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Steven Finkbeiner
- Gladstone Institute of Neurological Disease, San Francisco, California, USA
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Nancy M Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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10
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Architecture of the Lsm1-7-Pat1 complex: a conserved assembly in eukaryotic mRNA turnover. Cell Rep 2013; 5:283-91. [PMID: 24139796 DOI: 10.1016/j.celrep.2013.10.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 10/03/2013] [Accepted: 10/03/2013] [Indexed: 12/31/2022] Open
Abstract
The decay of mRNAs is a key step in eukaryotic gene expression. The cytoplasmic Lsm1-7-Pat1 complex is a conserved component of the 5'-to-3' mRNA decay pathway, linking deadenylation to decapping. Lsm1-7 is similar to the nuclear Sm complexes that bind oligo-uridine tracts in snRNAs. The 2.3 Å resolution structure of S. cerevisiae Lsm1-7 shows the presence of a heptameric ring with Lsm1-2-3-6-5-7-4 topology. A distinct structural feature of the cytoplasmic Lsm ring is the C-terminal extension of Lsm1, which plugs the exit site of the central channel and approaches the RNA binding pockets. The 3.7 Å resolution structure of Lsm1-7 bound to the C-terminal domain of Pat1 reveals that Pat1 recognition is not mediated by the distinguishing cytoplasmic subunit, Lsm1, but by Lsm2 and Lsm3. These results show how the auxiliary domains and the canonical Sm folds of the Lsm1-7 complex are organized in order to mediate and modulate macromolecular interactions.
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11
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Abstract
The bacterial Hfq protein is a versatile modulator of RNA function and is particularly important for regulation mediated by small non-coding RNAs. Hfq is a bacterial Sm protein but bears more similarity to the eukaryotic Sm-like (Lsm) family of proteins than the prototypical Sm proteins. Hfq and Lsm proteins share the ability to chaperone RNA-RNA and RNA/protein interactions and an interesting penchant for protecting the 3′ end of a transcript from exonucleolytic decay while encouraging degradation through other pathways. Our view of Lsm function in eukaryotes has historically been informed by studies of Hfq structure and function but mutational analyses and structural studies of Lsm sub-complexes have given important insights as well. Here, we aim to compare and contrast the roles of these evolutionarily related complexes and to highlight areas for future investigation.
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Affiliation(s)
- Carol J Wilusz
- Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, CO, USA.
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12
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Moon SL, Barnhart MD, Wilusz J. Inhibition and avoidance of mRNA degradation by RNA viruses. Curr Opin Microbiol 2012; 15:500-5. [PMID: 22626865 DOI: 10.1016/j.mib.2012.04.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 04/27/2012] [Indexed: 11/27/2022]
Abstract
The cellular mRNA decay machinery plays a major role in regulating the quality and quantity of gene expression in cells. This machinery involves multiple enzymes and pathways that converge to promote the exonucleolytic decay of mRNAs. The transcripts made by RNA viruses are susceptible to degradation by this machinery and, in fact, can be actively targeted. Thus, to maintain gene expression and replication, RNA viruses have evolved a number of strategies to avoid and/or inactivate aspects of the cellular mRNA decay machinery. Recent work uncovering the mechanisms used by RNA viruses to maintain the stability of their transcripts is described below.
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Affiliation(s)
- Stephanie L Moon
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, United States
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