1
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Ma T, Xiong ES, Lardelli RM, Lykke-Andersen J. Sm complex assembly and 5' cap trimethylation promote selective processing of snRNAs by the 3' exonuclease TOE1. Proc Natl Acad Sci U S A 2024; 121:e2315259121. [PMID: 38194449 PMCID: PMC10801842 DOI: 10.1073/pnas.2315259121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 12/06/2023] [Indexed: 01/11/2024] Open
Abstract
Competing exonucleases that promote 3' end maturation or degradation direct quality control of small non-coding RNAs, but how these enzymes distinguish normal from aberrant RNAs is poorly understood. The Pontocerebellar Hypoplasia 7 (PCH7)-associated 3' exonuclease TOE1 promotes maturation of canonical small nuclear RNAs (snRNAs). Here, we demonstrate that TOE1 achieves specificity toward canonical snRNAs through their Sm complex assembly and cap trimethylation, two features that distinguish snRNAs undergoing correct biogenesis from other small non-coding RNAs. Indeed, disruption of Sm complex assembly via snRNA mutations or protein depletions obstructs snRNA processing by TOE1, and in vitro snRNA processing by TOE1 is stimulated by a trimethylated cap. An unstable snRNA variant that normally fails to undergo maturation becomes fully processed by TOE1 when its degenerate Sm binding motif is converted into a canonical one. Our findings uncover the molecular basis for how TOE1 distinguishes snRNAs from other small non-coding RNAs and explain how TOE1 promotes maturation specifically of canonical snRNAs undergoing proper processing.
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Affiliation(s)
- Tiantai Ma
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA92093
| | - Erica S. Xiong
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA92093
| | - Rea M. Lardelli
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA92093
| | - Jens Lykke-Andersen
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA92093
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2
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Huynh TN, Parker R. The PARN, TOE1, and USB1 RNA deadenylases and their roles in non-coding RNA regulation. J Biol Chem 2023; 299:105139. [PMID: 37544646 PMCID: PMC10493513 DOI: 10.1016/j.jbc.2023.105139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Revised: 07/28/2023] [Accepted: 07/29/2023] [Indexed: 08/08/2023] Open
Abstract
The levels of non-coding RNAs (ncRNAs) are regulated by transcription, RNA processing, and RNA degradation pathways. One mechanism for the degradation of ncRNAs involves the addition of oligo(A) tails by non-canonical poly(A) polymerases, which then recruit processive sequence-independent 3' to 5' exonucleases for RNA degradation. This pathway of decay is also regulated by three 3' to 5' exoribonucleases, USB1, PARN, and TOE1, which remove oligo(A) tails and thereby can protect ncRNAs from decay in a manner analogous to the deubiquitination of proteins. Loss-of-function mutations in these genes lead to premature degradation of some ncRNAs and lead to specific human diseases such as Poikiloderma with Neutropenia (PN) for USB1, Dyskeratosis Congenita (DC) for PARN and Pontocerebellar Hypoplasia type 7 (PCH7) for TOE1. Herein, we review the biochemical properties of USB1, PARN, and TOE1, how they modulate ncRNA levels, and their roles in human diseases.
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Affiliation(s)
- Thao Ngoc Huynh
- Department of Biochemistry, University of Colorado Boulder, Boulder, Colorado, USA
| | - Roy Parker
- Department of Biochemistry, University of Colorado Boulder, Boulder, Colorado, USA; Howard Hughes Medical Institute, Chevy Chase, Maryland, USA.
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3
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Jeong HC, Shukla S, Fok WC, Huynh TN, Batista LFZ, Parker R. USB1 is a miRNA deadenylase that regulates hematopoietic development. Science 2023; 379:901-907. [PMID: 36862787 PMCID: PMC10827040 DOI: 10.1126/science.abj8379] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 02/03/2023] [Indexed: 03/04/2023]
Abstract
Mutations in the 3' to 5' RNA exonuclease USB1 cause hematopoietic failure in poikiloderma with neutropenia (PN). Although USB1 is known to regulate U6 small nuclear RNA maturation, the molecular mechanism underlying PN remains undetermined, as pre-mRNA splicing is unaffected in patients. We generated human embryonic stem cells harboring the PN-associated mutation c.531_delA in USB1 and show that this mutation impairs human hematopoiesis. Dysregulated microRNA (miRNA) levels in USB1 mutants during blood development contribute to hematopoietic failure, because of a failure to remove 3'-end adenylated tails added by PAPD5/7. Modulation of miRNA 3'-end adenylation through genetic or chemical inhibition of PAPD5/7 rescues hematopoiesis in USB1 mutants. This work shows that USB1 acts as a miRNA deadenylase and suggests PAPD5/7 inhibition as a potential therapy for PN.
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Affiliation(s)
- Ho-Chang Jeong
- Division of Hematology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
- Center for Genome Integrity, Siteman Cancer Center, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Siddharth Shukla
- Department of Biochemistry, University of Colorado, Boulder, CO 80303, USA
- Howard Hughes Medical Institute, Chevy Chase MD 20815, USA
| | - Wilson Chun Fok
- Division of Hematology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
- Center for Genome Integrity, Siteman Cancer Center, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Thao Ngoc Huynh
- Department of Biochemistry, University of Colorado, Boulder, CO 80303, USA
- Howard Hughes Medical Institute, Chevy Chase MD 20815, USA
| | - Luis Francisco Zirnberger Batista
- Division of Hematology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
- Center for Genome Integrity, Siteman Cancer Center, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Roy Parker
- Department of Biochemistry, University of Colorado, Boulder, CO 80303, USA
- Howard Hughes Medical Institute, Chevy Chase MD 20815, USA
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4
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Love SL, Emerson JD, Koide K, Hoskins AA. Pre-mRNA splicing-associated diseases and therapies. RNA Biol 2023; 20:525-538. [PMID: 37528617 PMCID: PMC10399480 DOI: 10.1080/15476286.2023.2239601] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2023] [Indexed: 08/03/2023] Open
Abstract
Precursor mRNA (pre-mRNA) splicing is an essential step in human gene expression and is carried out by a large macromolecular machine called the spliceosome. Given the spliceosome's role in shaping the cellular transcriptome, it is not surprising that mutations in the splicing machinery can result in a range of human diseases and disorders (spliceosomopathies). This review serves as an introduction into the main features of the pre-mRNA splicing machinery in humans and how changes in the function of its components can lead to diseases ranging from blindness to cancers. Recently, several drugs have been developed that interact directly with this machinery to change splicing outcomes at either the single gene or transcriptome-scale. We discuss the mechanism of action of several drugs that perturb splicing in unique ways. Finally, we speculate on what the future may hold in the emerging area of spliceosomopathies and spliceosome-targeted treatments.
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Affiliation(s)
- Sierra L. Love
- Genetics Training Program, University of Wisconsin-Madison, Madison, WI, USA
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Joseph D. Emerson
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kazunori Koide
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Aaron A. Hoskins
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
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5
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Jung S, von Thülen T, Yang I, Laukemper V, Rupf B, Janga H, Panagiotidis GD, Schoen A, Nicolai M, Schulte LN, Obermann HL, Weber F, Kaufmann A, Bauer S. A ribosomal RNA fragment with 2',3'-cyclic phosphate and GTP-binding activity acts as RIG-I ligand. Nucleic Acids Res 2020; 48:10397-10412. [PMID: 32946572 PMCID: PMC7544222 DOI: 10.1093/nar/gkaa739] [Citation(s) in RCA: 8] [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: 10/31/2019] [Revised: 08/19/2020] [Accepted: 08/26/2020] [Indexed: 12/13/2022] Open
Abstract
The RNA helicase RIG-I plays a key role in sensing pathogen-derived RNA. Double-stranded RNA structures bearing 5'-tri- or diphosphates are commonly referred to as activating RIG-I ligands. However, endogenous RNA fragments generated during viral infection via RNase L also activate RIG-I. Of note, RNase-digested RNA fragments bear a 5'-hydroxyl group and a 2',3'-cyclic phosphate. How endogenous RNA fragments activate RIG-I despite the lack of 5'-phosphorylation has not been elucidated. Here we describe an endogenous RIG-I ligand (eRL) that is derived from the internal transcribed spacer 2 region (ITS2) of the 45S ribosomal RNA after partial RNase A digestion in vitro, RNase A protein transfection or RNase L activation. The immunostimulatory property of the eRL is dependent on 2',3'-cyclic phosphate and its sequence is characterized by a G-quadruplex containing sequence motif mediating guanosine-5'-triphosphate (GTP) binding. In summary, RNase generated self-RNA fragments with 2',3'-cyclic phosphate function as nucleotide-5'-triphosphate binding aptamers activating RIG-I.
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Affiliation(s)
- Stephanie Jung
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Tina von Thülen
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Ines Yang
- Institut für Medizinische Mikrobiologie und Krankenhaushygiene, Medizinische Hochschule Hannover, Carl Neuberg Straße 1, 30625 Hannover, Germany
| | - Viktoria Laukemper
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Benjamin Rupf
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Harshavardhan Janga
- Institut für Lungenforschung/iLung, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Georgios-Dimitrios Panagiotidis
- Institut für Virologie, Fachbereich Veterinärmedizin (FB10), Justus-Liebig-Universität Gießen, Schubertstr. 81, 35392 Gießen, Germany
| | - Andreas Schoen
- Institut für Virologie, Fachbereich Veterinärmedizin (FB10), Justus-Liebig-Universität Gießen, Schubertstr. 81, 35392 Gießen, Germany
| | - Marina Nicolai
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Leon N Schulte
- Institut für Lungenforschung/iLung, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
- Deutsches Zentrum für Lungenforschung (DZL), 35392 Gießen, Germany
| | - Hannah-Lena Obermann
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Friedemann Weber
- Institut für Virologie, Fachbereich Veterinärmedizin (FB10), Justus-Liebig-Universität Gießen, Schubertstr. 81, 35392 Gießen, Germany
| | - Andreas Kaufmann
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
| | - Stefan Bauer
- Institut für Immunologie, Philipps-Universität Marburg, BMFZ, Hans-Meerwein-Straße 2, 35043 Marburg, Germany
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6
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Liudkovska V, Dziembowski A. Functions and mechanisms of RNA tailing by metazoan terminal nucleotidyltransferases. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 12:e1622. [PMID: 33145994 PMCID: PMC7988573 DOI: 10.1002/wrna.1622] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/25/2020] [Accepted: 06/26/2020] [Indexed: 12/28/2022]
Abstract
Termini often determine the fate of RNA molecules. In recent years, 3' ends of almost all classes of RNA species have been shown to acquire nontemplated nucleotides that are added by terminal nucleotidyltransferases (TENTs). The best-described role of 3' tailing is the bulk polyadenylation of messenger RNAs in the cell nucleus that is catalyzed by canonical poly(A) polymerases (PAPs). However, many other enzymes that add adenosines, uridines, or even more complex combinations of nucleotides have recently been described. This review focuses on metazoan TENTs, which are either noncanonical PAPs or terminal uridylyltransferases with varying processivity. These enzymes regulate RNA stability and RNA functions and are crucial in early development, gamete production, and somatic tissues. TENTs regulate gene expression at the posttranscriptional level, participate in the maturation of many transcripts, and protect cells against viral invasion and the transposition of repetitive sequences. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Processing > 3' End Processing RNA Turnover and Surveillance > Regulation of RNA Stability.
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Affiliation(s)
- Vladyslava Liudkovska
- Laboratory of RNA Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Andrzej Dziembowski
- Laboratory of RNA Biology, International Institute of Molecular and Cell Biology, Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
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7
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Nomura Y, Montemayor EJ, Virta JM, Hayes SM, Butcher SE. Structural basis for the evolution of cyclic phosphodiesterase activity in the U6 snRNA exoribonuclease Usb1. Nucleic Acids Res 2020; 48:1423-1434. [PMID: 31832688 PMCID: PMC7026655 DOI: 10.1093/nar/gkz1177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/02/2019] [Accepted: 12/05/2019] [Indexed: 11/28/2022] Open
Abstract
U6 snRNA undergoes post-transcriptional 3′ end modification prior to incorporation into the active site of spliceosomes. The responsible exoribonuclease is Usb1, which removes nucleotides from the 3′ end of U6 and, in humans, leaves a 2′,3′ cyclic phosphate that is recognized by the Lsm2–8 complex. Saccharomycescerevisiae Usb1 has additional 2′,3′ cyclic phosphodiesterase (CPDase) activity, which converts the cyclic phosphate into a 3′ phosphate group. Here we investigate the molecular basis for the evolution of Usb1 CPDase activity. We examine the structure and function of Usb1 from Kluyveromyces marxianus, which shares 25 and 19% sequence identity to the S. cerevisiae and Homo sapiens orthologs of Usb1, respectively. We show that K. marxianus Usb1 enzyme has CPDase activity and determined its structure, free and bound to the substrate analog uridine 5′-monophosphate. We find that the origin of CPDase activity is related to a loop structure that is conserved in yeast and forms a distinct penultimate (n – 1) nucleotide binding site. These data provide structural and mechanistic insight into the evolutionary divergence of Usb1 catalysis.
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Affiliation(s)
- Yuichiro Nomura
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Eric J Montemayor
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Johanna M Virta
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Samuel M Hayes
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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8
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Abstract
Long interspersed element-1s (L1s) encode 2 proteins (ORF1p and ORF2p) that preferentially mobilize (i.e., retrotranspose) their encoding messenger RNA (mRNA) transcript. ORF1p and/or ORF2p can also mobilize other cellular RNAs, including short interspersed elements (SINEs), U6 small nuclear RNA (snRNA), and mRNAs. Here, we demonstrate the RNA ligase RtcB can join U6 snRNA to L1 or other cellular RNAs to create chimeric RNAs; retrotransposition of the resultant chimeric RNAs leads to chimeric pseudogene formation; and chimeric U6/L1 RNAs are part of the transcriptome in multiple human cells. These data suggest RNA ligation contributes to the plasticity of the transcriptome and that the retrotransposition of chimeric RNAs can generate genetic variation in the human genome. Long interspersed element-1 (LINE-1 or L1) amplifies via retrotransposition. Active L1s encode 2 proteins (ORF1p and ORF2p) that bind their encoding transcript to promote retrotransposition in cis. The L1-encoded proteins also promote the retrotransposition of small-interspersed element RNAs, noncoding RNAs, and messenger RNAs in trans. Some L1-mediated retrotransposition events consist of a copy of U6 RNA conjoined to a variably 5′-truncated L1, but how U6/L1 chimeras are formed requires elucidation. Here, we report the following: The RNA ligase RtcB can join U6 RNAs ending in a 2′,3′-cyclic phosphate to L1 RNAs containing a 5′-OH in vitro; depletion of endogenous RtcB in HeLa cell extracts reduces U6/L1 RNA ligation efficiency; retrotransposition of U6/L1 RNAs leads to U6/L1 pseudogene formation; and a unique cohort of U6/L1 chimeric RNAs are present in multiple human cell lines. Thus, these data suggest that U6 small nuclear RNA (snRNA) and RtcB participate in the formation of chimeric RNAs and that retrotransposition of chimeric RNA contributes to interindividual genetic variation.
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9
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Nomura Y, Roston D, Montemayor EJ, Cui Q, Butcher SE. Structural and mechanistic basis for preferential deadenylation of U6 snRNA by Usb1. Nucleic Acids Res 2018; 46:11488-11501. [PMID: 30215753 PMCID: PMC6265477 DOI: 10.1093/nar/gky812] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 08/27/2018] [Accepted: 08/29/2018] [Indexed: 01/08/2023] Open
Abstract
Post-transcriptional modification of snRNA is central to spliceosome function. Usb1 is an exoribonuclease that shortens the oligo-uridine tail of U6 snRNA, resulting in a terminal 2',3' cyclic phosphate group in most eukaryotes, including humans. Loss of function mutations in human Usb1 cause the rare disorder poikiloderma with neutropenia (PN), and result in U6 snRNAs with elongated 3' ends that are aberrantly adenylated. Here, we show that human Usb1 removes 3' adenosines with 20-fold greater efficiency than uridines, which explains the presence of adenylated U6 snRNAs in cells lacking Usb1. We determined three high-resolution co-crystal structures of Usb1: wild-type Usb1 bound to the substrate analog adenosine 5'-monophosphate, and an inactive mutant bound to RNAs with a 3' terminal adenosine and uridine. These structures, along with QM/MM MD simulations of the catalytic mechanism, illuminate the molecular basis for preferential deadenylation of U6 snRNA. The extent of Usb1 processing is influenced by the secondary structure of U6 snRNA.
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Affiliation(s)
- Yuichiro Nomura
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Daniel Roston
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
- Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Eric J Montemayor
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Qiang Cui
- Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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10
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Warkocki Z, Liudkovska V, Gewartowska O, Mroczek S, Dziembowski A. Terminal nucleotidyl transferases (TENTs) in mammalian RNA metabolism. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2018.0162. [PMID: 30397099 PMCID: PMC6232586 DOI: 10.1098/rstb.2018.0162] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2018] [Indexed: 12/15/2022] Open
Abstract
In eukaryotes, almost all RNA species are processed at their 3′ ends and most mRNAs are polyadenylated in the nucleus by canonical poly(A) polymerases. In recent years, several terminal nucleotidyl transferases (TENTs) including non-canonical poly(A) polymerases (ncPAPs) and terminal uridyl transferases (TUTases) have been discovered. In contrast to canonical polymerases, TENTs' functions are more diverse; some, especially TUTases, induce RNA decay while others, such as cytoplasmic ncPAPs, activate translationally dormant deadenylated mRNAs. The mammalian genome encodes 11 different TENTs. This review summarizes the current knowledge about the functions and mechanisms of action of these enzymes. This article is part of the theme issue ‘5′ and 3′ modifications controlling RNA degradation’.
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Affiliation(s)
- Zbigniew Warkocki
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, Poznan, Poland
| | - Vladyslava Liudkovska
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Olga Gewartowska
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Seweryn Mroczek
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Andrzej Dziembowski
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland .,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
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11
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Architecture of the U6 snRNP reveals specific recognition of 3'-end processed U6 snRNA. Nat Commun 2018; 9:1749. [PMID: 29717126 PMCID: PMC5931518 DOI: 10.1038/s41467-018-04145-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 04/06/2018] [Indexed: 01/09/2023] Open
Abstract
The spliceosome removes introns from precursor messenger RNA (pre-mRNA) to produce mature mRNA. Prior to catalysis, spliceosomes are assembled de novo onto pre-mRNA substrates. During this assembly process, U6 small nuclear RNA (snRNA) undergoes extensive structural remodeling. The early stages of this remodeling process are chaperoned by U6 snRNP proteins Prp24 and the Lsm2-8 heteroheptameric ring. We now report a structure of the U6 snRNP from Saccharomyces cerevisiae. The structure reveals protein-protein contacts that position Lsm2-8 in close proximity to the chaperone "active site" of Prp24. The structure also shows how the Lsm2-8 ring specifically recognizes U6 snRNA that has been post-transcriptionally modified at its 3' end, thereby elucidating the mechanism by which U6 snRNPs selectively recruit 3' end-processed U6 snRNA into spliceosomes. Additionally, the structure reveals unanticipated homology between the C-terminal regions of Lsm8 and the cytoplasmic Lsm1 protein involved in mRNA decay.
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12
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Didychuk AL, Butcher SE, Brow DA. The life of U6 small nuclear RNA, from cradle to grave. RNA (NEW YORK, N.Y.) 2018; 24:437-460. [PMID: 29367453 PMCID: PMC5855946 DOI: 10.1261/rna.065136.117] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Removal of introns from precursor messenger RNA (pre-mRNA) and some noncoding transcripts is an essential step in eukaryotic gene expression. In the nucleus, this process of RNA splicing is carried out by the spliceosome, a multi-megaDalton macromolecular machine whose core components are conserved from yeast to humans. In addition to many proteins, the spliceosome contains five uridine-rich small nuclear RNAs (snRNAs) that undergo an elaborate series of conformational changes to correctly recognize the splice sites and catalyze intron removal. Decades of biochemical and genetic data, along with recent cryo-EM structures, unequivocally demonstrate that U6 snRNA forms much of the catalytic core of the spliceosome and is highly dynamic, interacting with three snRNAs, the pre-mRNA substrate, and >25 protein partners throughout the splicing cycle. This review summarizes the current state of knowledge on how U6 snRNA is synthesized, modified, incorporated into snRNPs and spliceosomes, recycled, and degraded.
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Affiliation(s)
- Allison L Didychuk
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - David A Brow
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA
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13
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Abstract
Numerous surveillance pathways sculpt eukaryotic transcriptomes by degrading unneeded, defective, and potentially harmful noncoding RNAs (ncRNAs). Because aberrant and excess ncRNAs are largely degraded by exoribonucleases, a key characteristic of these RNAs is an accessible, protein-free 5' or 3' end. Most exoribonucleases function with cofactors that recognize ncRNAs with accessible 5' or 3' ends and/or increase the availability of these ends. Noncoding RNA surveillance pathways were first described in budding yeast, and there are now high-resolution structures of many components of the yeast pathways and significant mechanistic understanding as to how they function. Studies in human cells are revealing the ways in which these pathways both resemble and differ from their yeast counterparts, and are also uncovering numerous pathways that lack equivalents in budding yeast. In this review, we describe both the well-studied pathways uncovered in yeast and the new concepts that are emerging from studies in mammalian cells. We also discuss the ways in which surveillance pathways compete with chaperone proteins that transiently protect nascent ncRNA ends from exoribonucleases, with partner proteins that sequester these ends within RNPs, and with end modification pathways that protect the ends of some ncRNAs from nucleases.
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Affiliation(s)
- Cedric Belair
- RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 21702 , United States
| | - Soyeong Sim
- RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 21702 , United States
| | - Sandra L Wolin
- RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 21702 , United States
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14
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Abstract
Much evidence is now accumulating that, in addition to their general role in splicing, the components of the core splicing machinery have extensive regulatory potential. In particular, recent evidence has demonstrated that de-regulation of these factors cause the highest extent of alternative splicing changes compared to de-regulation of the classical splicing regulators. This lack of a general inhibition of splicing resonates the differential splicing effects observed in different disease pathologies associated with specific mutations targeting core spliceosomal components. In this review we will summarize what is currently known regarding the involvement of core spliceosomal U-snRNP complexes in perturbed tissue development and human diseases and argue for the existence of a compensatory mechanism enabling cells to cope with drastic perturbations in core splicing components. This system maintains the correct balance of spliceosomal snRNPs through differential expression of variant (v)U-snRNPs.
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Affiliation(s)
- Pilar Vazquez-Arango
- a Nuffield Department of Obstetrics and Gynaecology, Level 3 , Women's Centre, John Radcliffe Hospital , Oxford , England
| | - Dawn O'Reilly
- b Sir William Dunn School of pathology , University of Oxford , South Parks Road, Oxford , England
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15
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Didychuk AL, Montemayor EJ, Carrocci TJ, DeLaitsch AT, Lucarelli SE, Westler WM, Brow DA, Hoskins AA, Butcher SE. Usb1 controls U6 snRNP assembly through evolutionarily divergent cyclic phosphodiesterase activities. Nat Commun 2017; 8:497. [PMID: 28887445 PMCID: PMC5591277 DOI: 10.1038/s41467-017-00484-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 07/02/2017] [Indexed: 01/06/2023] Open
Abstract
U6 small nuclear ribonucleoprotein (snRNP) biogenesis is essential for spliceosome assembly, but not well understood. Here, we report structures of the U6 RNA processing enzyme Usb1 from yeast and a substrate analog bound complex from humans. Unlike the human ortholog, we show that yeast Usb1 has cyclic phosphodiesterase activity that leaves a terminal 3' phosphate which prevents overprocessing. Usb1 processing of U6 RNA dramatically alters its affinity for cognate RNA-binding proteins. We reconstitute the post-transcriptional assembly of yeast U6 snRNP in vitro, which occurs through a complex series of handoffs involving 10 proteins (Lhp1, Prp24, Usb1 and Lsm2-8) and anti-cooperative interactions between Prp24 and Lhp1. We propose a model for U6 snRNP assembly that explains how evolutionarily divergent and seemingly antagonistic proteins cooperate to protect and chaperone the nascent snRNA during its journey to the spliceosome.The mechanism of U6 small nuclear ribonucleoprotein (snRNP) biogenesis is not well understood. Here the authors characterize the enzymatic activities and structures of yeast and human U6 RNA processing enzyme Usb1, reconstitute post-transcriptional assembly of yeast U6 snRNP in vitro, and propose a model for U6 snRNP assembly.
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Affiliation(s)
- Allison L Didychuk
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - Eric J Montemayor
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - Tucker J Carrocci
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - Andrew T DeLaitsch
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - Stefani E Lucarelli
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - William M Westler
- National Magnetic Resonance Facility at Madison, Biochemistry Department, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - David A Brow
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - Aaron A Hoskins
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706, USA.
- National Magnetic Resonance Facility at Madison, Biochemistry Department, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA.
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16
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Zinder JC, Lima CD. Targeting RNA for processing or destruction by the eukaryotic RNA exosome and its cofactors. Genes Dev 2017; 31:88-100. [PMID: 28202538 PMCID: PMC5322736 DOI: 10.1101/gad.294769.116] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In this review, Zinder and Lima highlight recent advances that have illuminated roles for the RNA exosome and its cofactors in specific biological pathways, alongside studies that attempted to dissect these activities through structural and biochemical characterization of nuclear and cytoplasmic RNA exosome complexes. The eukaryotic RNA exosome is an essential and conserved protein complex that can degrade or process RNA substrates in the 3′-to-5′ direction. Since its discovery nearly two decades ago, studies have focused on determining how the exosome, along with associated cofactors, achieves the demanding task of targeting particular RNAs for degradation and/or processing in both the nucleus and cytoplasm. In this review, we highlight recent advances that have illuminated roles for the RNA exosome and its cofactors in specific biological pathways, alongside studies that attempted to dissect these activities through structural and biochemical characterization of nuclear and cytoplasmic RNA exosome complexes.
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Affiliation(s)
- John C Zinder
- Tri-Institutional Training Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Structural Biology Program, Sloan Kettering Institute, New York, New York, 10065, USA
| | - Christopher D Lima
- Structural Biology Program, Sloan Kettering Institute, New York, New York, 10065, USA.,Howard Hughes Medical Institute, New York, New York, 10065 USA
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