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Yu NK, McClatchy DB, Diedrich JK, Romero S, Choi JH, Martínez-Bartolomé S, Delahunty CM, Muotri AR, Yates JR. Interactome analysis illustrates diverse gene regulatory processes associated with LIN28A in human iPS cell-derived neural progenitor cells. iScience 2021; 24:103321. [PMID: 34816099 PMCID: PMC8593586 DOI: 10.1016/j.isci.2021.103321] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 09/07/2021] [Accepted: 10/19/2021] [Indexed: 12/02/2022] Open
Abstract
A single protein can be multifaceted depending on the cellular contexts and interacting molecules. LIN28A is an RNA-binding protein that governs developmental timing, cellular proliferation, differentiation, stem cell pluripotency, and metabolism. In addition to its best-known roles in microRNA biogenesis, diverse molecular roles have been recognized. In the nervous system, LIN28A is known to play critical roles in proliferation and differentiation of neural progenitor cells (NPCs). We profiled the endogenous LIN28A-interacting proteins in NPCs differentiated from human induced pluripotent stem (iPS) cells using immunoprecipitation and liquid chromatography-tandem mass spectrometry. We identified over 500 LIN28A-interacting proteins, including 156 RNA-independent interactors. Functions of these proteins span a wide range of gene regulatory processes. Prompted by the interactome data, we revealed that LIN28A may impact the subcellular distribution of its interactors and stress granule formation upon oxidative stress. Overall, our analysis opens multiple avenues for elaborating molecular roles and characteristics of LIN28A.
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Affiliation(s)
- Nam-Kyung Yu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Daniel B. McClatchy
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jolene K. Diedrich
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Sarah Romero
- Department of Pediatrics/Rady Children’s Hospital San Diego, Department of Cellular & Molecular Medicine, School of Medicine, University of California, San Diego, San Diego, CA 92037, USA
| | - Jun-Hyeok Choi
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | | | - Claire M. Delahunty
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Alysson R. Muotri
- Department of Pediatrics/Rady Children’s Hospital San Diego, Department of Cellular & Molecular Medicine, School of Medicine, University of California, San Diego, San Diego, CA 92037, USA
- Stem Cell Program, Center for Academic Research and Training in Anthropogeny (CARTA), Archealization Center (ArchC), Kavli Institute for Brain and Mind, La Jolla, CA 92037, USA
| | - John R. Yates
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
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2
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Wood KA, Eadsforth MA, Newman WG, O'Keefe RT. The Role of the U5 snRNP in Genetic Disorders and Cancer. Front Genet 2021; 12:636620. [PMID: 33584830 PMCID: PMC7876476 DOI: 10.3389/fgene.2021.636620] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/04/2021] [Indexed: 12/14/2022] Open
Abstract
Pre-mRNA splicing is performed by the spliceosome, a dynamic macromolecular complex consisting of five small uridine-rich ribonucleoprotein complexes (the U1, U2, U4, U5, and U6 snRNPs) and numerous auxiliary splicing factors. A plethora of human disorders are caused by genetic variants affecting the function and/or expression of splicing factors, including the core snRNP proteins. Variants in the genes encoding proteins of the U5 snRNP cause two distinct and tissue-specific human disease phenotypes – variants in PRPF6, PRPF8, and SNRP200 are associated with retinitis pigmentosa (RP), while variants in EFTUD2 and TXNL4A cause the craniofacial disorders mandibulofacial dysostosis Guion-Almeida type (MFDGA) and Burn-McKeown syndrome (BMKS), respectively. Furthermore, recurrent somatic mutations or changes in the expression levels of a number of U5 snRNP proteins (PRPF6, PRPF8, EFTUD2, DDX23, and SNRNP40) have been associated with human cancers. How and why variants in ubiquitously expressed spliceosome proteins required for pre-mRNA splicing in all human cells result in tissue-restricted disease phenotypes is not clear. Additionally, why variants in different, yet interacting, proteins making up the same core spliceosome snRNP result in completely distinct disease outcomes – RP, craniofacial defects or cancer – is unclear. In this review, we define the roles of different U5 snRNP proteins in RP, craniofacial disorders and cancer, including how disease-associated genetic variants affect pre-mRNA splicing and the proposed disease mechanisms. We then propose potential hypotheses for how U5 snRNP variants cause tissue specificity resulting in the restricted and distinct human disorders.
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Affiliation(s)
- Katherine A Wood
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester, United Kingdom.,Manchester Centre for Genomic Medicine, Manchester Academic Health Science Centre, Manchester University NHS Foundation Trust, Manchester, United Kingdom
| | - Megan A Eadsforth
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester, United Kingdom
| | - William G Newman
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester, United Kingdom.,Manchester Centre for Genomic Medicine, Manchester Academic Health Science Centre, Manchester University NHS Foundation Trust, Manchester, United Kingdom
| | - Raymond T O'Keefe
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester, United Kingdom
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3
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Jia J, Ganichkin OM, Preußner M, Absmeier E, Alings C, Loll B, Heyd F, Wahl MC. A Snu114-GTP-Prp8 module forms a relay station for efficient splicing in yeast. Nucleic Acids Res 2020; 48:4572-4584. [PMID: 32196113 PMCID: PMC7192624 DOI: 10.1093/nar/gkaa182] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 02/26/2020] [Accepted: 03/10/2020] [Indexed: 01/24/2023] Open
Abstract
The single G protein of the spliceosome, Snu114, has been proposed to facilitate splicing as a molecular motor or as a regulatory G protein. However, available structures of spliceosomal complexes show Snu114 in the same GTP-bound state, and presently no Snu114 GTPase-regulatory protein is known. We determined a crystal structure of Snu114 with a Snu114-binding region of the Prp8 protein, in which Snu114 again adopts the same GTP-bound conformation seen in spliceosomes. Snu114 and the Snu114–Prp8 complex co-purified with endogenous GTP. Snu114 exhibited weak, intrinsic GTPase activity that was abolished by the Prp8 Snu114-binding region. Exchange of GTP-contacting residues in Snu114, or of Prp8 residues lining the Snu114 GTP-binding pocket, led to temperature-sensitive yeast growth and affected the same set of splicing events in vivo. Consistent with dynamic Snu114-mediated protein interactions during splicing, our results suggest that the Snu114–GTP–Prp8 module serves as a relay station during spliceosome activation and disassembly, but that GTPase activity may be dispensable for splicing.
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Affiliation(s)
- Junqiao Jia
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Oleg M Ganichkin
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Marco Preußner
- Freie Universität Berlin, Laboratory of RNA Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Eva Absmeier
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Claudia Alings
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Bernhard Loll
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Florian Heyd
- Freie Universität Berlin, Laboratory of RNA Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Markus C Wahl
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany.,Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
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4
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Thomas HB, Wood KA, Buczek WA, Gordon CT, Pingault V, Attié-Bitach T, Hentges KE, Varghese VC, Amiel J, Newman WG, O'Keefe RT. EFTUD2 missense variants disrupt protein function and splicing in mandibulofacial dysostosis Guion-Almeida type. Hum Mutat 2020; 41:1372-1382. [PMID: 32333448 DOI: 10.1002/humu.24027] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/26/2020] [Accepted: 04/19/2020] [Indexed: 12/20/2022]
Abstract
Pathogenic variants in the core spliceosome U5 small nuclear ribonucleoprotein gene EFTUD2/SNU114 cause the craniofacial disorder mandibulofacial dysostosis Guion-Almeida type (MFDGA). MFDGA-associated variants in EFTUD2 comprise large deletions encompassing EFTUD2, intragenic deletions and single nucleotide truncating or missense variants. These variants are predicted to result in haploinsufficiency by loss-of-function of the variant allele. While the contribution of deletions within EFTUD2 to allele loss-of-function are self-evident, the mechanisms by which missense variants are disease-causing have not been characterized functionally. Combining bioinformatics software prediction, yeast functional growth assays, and a minigene (MG) splicing assay, we have characterized how MFDGA missense variants result in EFTUD2 loss-of-function. Only four of 19 assessed missense variants cause EFTUD2 loss-of-function through altered protein function when modeled in yeast. Of the remaining 15 missense variants, five altered the normal splicing pattern of EFTUD2 pre-messenger RNA predominantly through exon skipping or cryptic splice site activation, leading to the introduction of a premature termination codon. Comparison of bioinformatic predictors for each missense variant revealed a disparity amongst different software packages and, in many cases, an inability to correctly predict changes in splicing subsequently determined by MG interrogation. This study highlights the need for laboratory-based validation of bioinformatic predictions for EFTUD2 missense variants.
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Affiliation(s)
- Huw B Thomas
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Katherine A Wood
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Weronika A Buczek
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Christopher T Gordon
- Laboratory of Embryology and Genetics of Human Malformation, Institut National de la Santé et de la Recherche Médicale (INSERM) UMR 1163, Institut Imagine, Paris, France.,Paris Descartes-Sorbonne Paris Cité University, Institut Imagine, Paris, France
| | - Véronique Pingault
- Laboratory of Embryology and Genetics of Human Malformation, Institut National de la Santé et de la Recherche Médicale (INSERM) UMR 1163, Institut Imagine, Paris, France.,Paris Descartes-Sorbonne Paris Cité University, Institut Imagine, Paris, France.,Département de Génétique, Hôpital Necker-Enfants Malades, AP-HP, Paris, France
| | - Tania Attié-Bitach
- Paris Descartes-Sorbonne Paris Cité University, Institut Imagine, Paris, France.,Département de Génétique, Hôpital Necker-Enfants Malades, AP-HP, Paris, France.,INSERM UMR 1163, Institut Imagine, Paris, France
| | - Kathryn E Hentges
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | | | - Jeanne Amiel
- Laboratory of Embryology and Genetics of Human Malformation, Institut National de la Santé et de la Recherche Médicale (INSERM) UMR 1163, Institut Imagine, Paris, France.,Paris Descartes-Sorbonne Paris Cité University, Institut Imagine, Paris, France.,Département de Génétique, Hôpital Necker-Enfants Malades, AP-HP, Paris, France
| | - William G Newman
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK.,Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, Center for Genomic Medicine, St. Mary's Hospital, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Raymond T O'Keefe
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
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5
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Wood KA, Rowlands CF, Qureshi WMS, Thomas HB, Buczek WA, Briggs TA, Hubbard SJ, Hentges KE, Newman WG, O’Keefe RT. Disease modeling of core pre-mRNA splicing factor haploinsufficiency. Hum Mol Genet 2019; 28:3704-3723. [PMID: 31304552 PMCID: PMC6935387 DOI: 10.1093/hmg/ddz169] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/04/2019] [Accepted: 07/08/2019] [Indexed: 12/12/2022] Open
Abstract
The craniofacial disorder mandibulofacial dysostosis Guion-Almeida type is caused by haploinsufficiency of the U5 snRNP gene EFTUD2/SNU114. However, it is unclear how reduced expression of this core pre-mRNA splicing factor leads to craniofacial defects. Here we use a CRISPR-Cas9 nickase strategy to generate a human EFTUD2-knockdown cell line and show that reduced expression of EFTUD2 leads to diminished proliferative ability of these cells, increased sensitivity to endoplasmic reticulum (ER) stress and the mis-expression of several genes involved in the ER stress response. RNA-Seq analysis of the EFTUD2-knockdown cell line revealed transcriptome-wide changes in gene expression, with an enrichment for genes associated with processes involved in craniofacial development. Additionally, our RNA-Seq data identified widespread mis-splicing in EFTUD2-knockdown cells. Analysis of the functional and physical characteristics of mis-spliced pre-mRNAs highlighted conserved properties, including length and splice site strengths, of retained introns and skipped exons in our disease model. We also identified enriched processes associated with the affected genes, including cell death, cell and organ morphology and embryonic development. Together, these data support a model in which EFTUD2 haploinsufficiency leads to the mis-splicing of a distinct subset of pre-mRNAs with a widespread effect on gene expression, including altering the expression of ER stress response genes and genes involved in the development of the craniofacial region. The increased burden of unfolded proteins in the ER resulting from mis-splicing would exceed the capacity of the defective ER stress response, inducing apoptosis in cranial neural crest cells that would result in craniofacial abnormalities during development.
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Affiliation(s)
- Katherine A Wood
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
- Center for Genomic Medicine, Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, St. Mary’s Hospital, The University of Manchester, Manchester Academic Health Science Centre Manchester, M13 9PT, UK
| | - Charlie F Rowlands
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
- Center for Genomic Medicine, Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, St. Mary’s Hospital, The University of Manchester, Manchester Academic Health Science Centre Manchester, M13 9PT, UK
| | - Wasay Mohiuddin Shaikh Qureshi
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
| | - Huw B Thomas
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
| | - Weronika A Buczek
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
| | - Tracy A Briggs
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
- Center for Genomic Medicine, Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, St. Mary’s Hospital, The University of Manchester, Manchester Academic Health Science Centre Manchester, M13 9PT, UK
| | - Simon J Hubbard
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
| | - Kathryn E Hentges
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
| | - William G Newman
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
- Center for Genomic Medicine, Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, St. Mary’s Hospital, The University of Manchester, Manchester Academic Health Science Centre Manchester, M13 9PT, UK
| | - Raymond T O’Keefe
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester
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6
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Plaschka C, Newman AJ, Nagai K. Structural Basis of Nuclear pre-mRNA Splicing: Lessons from Yeast. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a032391. [PMID: 30765413 DOI: 10.1101/cshperspect.a032391] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Noncoding introns are removed from nuclear precursor messenger RNA (pre-mRNA) in a two-step phosphoryl transfer reaction by the spliceosome, a dynamic multimegadalton enzyme. Cryo-electron microscopy (cryo-EM) structures of the Saccharomyces cerevisiae spliceosome were recently determined in eight key states. Combined with the wealth of available genetic and biochemical data, these structures have revealed new insights into the mechanisms of spliceosome assembly, activation, catalysis, and disassembly. The structures show how a single RNA catalytic center forms during activation and accomplishes both steps of the splicing reaction. The structures reveal how spliceosomal helicases remodel the spliceosome for active site formation, substrate docking, reaction product undocking, and spliceosome disassembly and how they facilitate splice site proofreading. Although human spliceosomes contain additional proteins, their cryo-EM structures suggest that the underlying mechanism is conserved across all eukaryotes. In this review, we summarize the current structural understanding of pre-mRNA splicing.
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Affiliation(s)
- Clemens Plaschka
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Andrew J Newman
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Kiyoshi Nagai
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
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7
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Vijayakumari D, Sharma AK, Bawa PS, Kumar R, Srinivasan S, Vijayraghavan U. Early splicing functions of fission yeast Prp16 and its unexpected requirement for gene Silencing is governed by intronic features. RNA Biol 2019; 16:754-769. [PMID: 30810475 DOI: 10.1080/15476286.2019.1585737] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Prp16 is a DEAH box pre-mRNA splicing factor that triggers a key spliceosome conformational switch to facilitate second step splicing in Saccharomyces cerevisiae. However, Prp16 functions are largely unexplored in Schizosaccharomyces pombe, an attractive model with exon-intron architecture more relevant to several other eukaryotes. Here, we generated mis-sense alleles in SpPrp16 whose consequences on genome-wide splicing uncover its nearly global splicing role with only a small subset of unaffected introns. Prp16 dependent and independent intron categories displayed a striking difference in the strength of intronic 5' splice site (5'SS)-U6 snRNA and branch site (BS)-U2 snRNA interactions. Selective weakening of these interactions could convert a Prp16 dependent intron into an independent one. These results point to the role of SpPrp16 in destabilizing 5'SS-U6snRNA and BS-U2snRNA interactions which plausibly trigger structural alterations in the spliceosome to facilitate first step catalysis. Our data suggest that SpPrp16 interactions with early acting factors, its enzymatic activities and association with intronic elements collectively account for efficient and accurate first step catalysis. In addition to splicing derangements in the spprp16F528S mutant, we show that SpPrp16 influences cell cycle progression and centromeric heterochromatinization. We propose that strong 5'SS-U6 snRNA and BS-U2 snRNA complementarity of intron-like elements in non-coding RNAs which lead to complete splicing arrest and impaired Seb1 functions at the pericentromeric loci may cumulatively account for the heterochromatin defects in spprp16F528S cells. These findings suggest that the diverse Prp16 functions within a genome are likely governed by its intronic features that influence splice site-snRNA interaction strength.
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Affiliation(s)
- Drisya Vijayakumari
- a Department of Microbiology and Cell Biology , Indian Institute of Science , Bangalore , India
| | - Amit Kumar Sharma
- a Department of Microbiology and Cell Biology , Indian Institute of Science , Bangalore , India
| | | | - Rakesh Kumar
- a Department of Microbiology and Cell Biology , Indian Institute of Science , Bangalore , India
| | | | - Usha Vijayraghavan
- a Department of Microbiology and Cell Biology , Indian Institute of Science , Bangalore , India
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8
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Gautam A, Beggs JD. Mutagenesis of Snu114 domain IV identifies a developmental role in meiotic splicing. RNA Biol 2019; 16:185-195. [PMID: 30672374 PMCID: PMC6380292 DOI: 10.1080/15476286.2018.1561145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 12/03/2018] [Accepted: 12/16/2018] [Indexed: 11/23/2022] Open
Abstract
Snu114, a component of the U5 snRNP, plays a key role in activation of the spliceosome. It controls the action of Brr2, an RNA-stimulated ATPase/RNA helicase that disrupts U4/U6 snRNA base-pairing prior to formation of the spliceosome's catalytic centre. Snu114 has a highly conserved domain structure that resembles that of the GTPase EF-2/EF-G in the ribosome. It has been suggested that the regulatory function of Snu114 in activation of the spliceosome is mediated by its C-terminal region, however, there has been only limited characterisation of the interactions of the C-terminal domains. We show a direct interaction between protein phosphatase PP1 and Snu114 domain 'IVa' and identify sequence 'YGVQYK' as a PP1 binding motif. Interestingly, this motif is also required for Cwc21 binding. We provide evidence for mutually exclusive interaction of Cwc21 and PP1 with Snu114 and show that the affinity of Cwc21 and PP1 for Snu114 is influenced by the different nucleotide-bound states of Snu114. Moreover, we identify a novel mutation in domain IVa that, while not affecting vegetative growth of yeast cells, causes a defect in splicing transcripts of the meiotic genes, SPO22, AMA1 and MER2, thereby inhibiting an early stage of meiosis.
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Affiliation(s)
- Amit Gautam
- a Wellcome Centre for Cell Biology , University of Edinburgh , Edinburgh , UK
| | - Jean D Beggs
- a Wellcome Centre for Cell Biology , University of Edinburgh , Edinburgh , UK
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9
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Abstract
Pre-mRNA splicing must occur with extremely high fidelity. Spliceosomes assemble onto pre-mRNA guided by specific sequences (5' splice site, 3' splice site, and branchpoint). When splice sites are mutated, as in many hereditary diseases, the spliceosome can aberrantly select nearby pseudo- or "cryptic" splice sites, often resulting in nonfunctional protein. How the spliceosome distinguishes authentic splice sites from cryptic splice sites is poorly understood. We performed a Caenorhabditis elegans genetic screen to find cellular factors that affect the frequency with which the spliceosome uses cryptic splice sites and identified two alleles in core spliceosome component Prp8 that alter cryptic splicing frequency. Subsequent complementary genetic and structural analyses in yeast implicate these alleles in the stability of the spliceosome's catalytic core. However, despite a clear effect on cryptic splicing, high-throughput mRNA sequencing of these prp-8 mutant C. elegans reveals that overall alternative splicing patterns are relatively unchanged. Our data suggest the spliceosome evolved intrinsic mechanisms to reduce the occurrence of cryptic splicing and that these mechanisms are distinct from those that impact alternative splicing.
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10
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Peters DT, Kay L, Eswaran J, Lakey JH, Soundararajan M. Human Miro Proteins Act as NTP Hydrolases through a Novel, Non-Canonical Catalytic Mechanism. Int J Mol Sci 2018; 19:ijms19123839. [PMID: 30513825 PMCID: PMC6321465 DOI: 10.3390/ijms19123839] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 11/27/2018] [Accepted: 11/28/2018] [Indexed: 01/13/2023] Open
Abstract
Mitochondria are highly dynamic organelles that play a central role in multiple cellular processes, including energy metabolism, calcium homeostasis and apoptosis. Miro proteins (Miros) are “atypical” Ras superfamily GTPases that display unique domain architecture and subcellular localisation regulating mitochondrial transport, autophagy and calcium sensing. Here, we present systematic catalytic domain characterisation and structural analyses of human Miros. Despite lacking key conserved catalytic residues (equivalent to Ras Y32, T35, G60 and Q61), the Miro N-terminal GTPase domains display GTPase activity. Surprisingly, the C-terminal GTPase domains previously assumed to be “relic” domains were also active. Moreover, Miros show substrate promiscuity and function as NTPases. Molecular docking and structural analyses of Miros revealed unusual features in the Switch I and II regions, facilitating promiscuous substrate binding and suggesting the usage of a novel hydrolytic mechanism. The key substitution in position 13 in the Miros leads us to suggest the existence of an “internal arginine finger”, allowing an unusual catalytic mechanism that does not require GAP protein. Together, the data presented here indicate novel catalytic functions of human Miro atypical GTPases through altered catalytic mechanisms.
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Affiliation(s)
- Daniel T Peters
- Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
| | - Laura Kay
- Department of Applied Sciences Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK.
| | - Jeyanthy Eswaran
- Northern Institute for Cancer Research, Newcastle University, Herschel Building, Newcastle upon Tyne, NE1 7RU, UK.
| | - Jeremy H Lakey
- Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
| | - Meera Soundararajan
- Department of Applied Sciences Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK.
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11
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Absmeier E, Santos KF, Wahl MC. Functions and regulation of the Brr2 RNA helicase during splicing. Cell Cycle 2016; 15:3362-3377. [PMID: 27792457 DOI: 10.1080/15384101.2016.1249549] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Pre-mRNA splicing entails the stepwise assembly of an inactive spliceosome, its catalytic activation, splicing catalysis and spliceosome disassembly. Transitions in this reaction cycle are accompanied by compositional and conformational rearrangements of the underlying RNA-protein interaction networks, which are driven and controlled by 8 conserved superfamily 2 RNA helicases. The Ski2-like helicase, Brr2, provides the key remodeling activity during spliceosome activation and is additionally implicated in the catalytic and disassembly phases of splicing, indicating that Brr2 needs to be tightly regulated during splicing. Recent structural and functional analyses have begun to unravel how Brr2 regulation is established via multiple layers of intra- and inter-molecular mechanisms. Brr2 has an unusual structure, including a long N-terminal region and a catalytically inactive C-terminal helicase cassette, which can auto-inhibit and auto-activate the enzyme, respectively. Both elements are essential, also serve as protein-protein interaction devices and the N-terminal region is required for stable Brr2 association with the tri-snRNP, tri-snRNP stability and retention of U5 and U6 snRNAs during spliceosome activation in vivo. Furthermore, a C-terminal region of the Prp8 protein, comprising consecutive RNase H-like and Jab1/MPN-like domains, can both up- and down-regulate Brr2 activity. Biochemical studies revealed an intricate cross-talk among the various cis- and trans-regulatory mechanisms. Comparison of isolated Brr2 to electron cryo-microscopic structures of yeast and human U4/U6•U5 tri-snRNPs and spliceosomes indicates how some of the regulatory elements exert their functions during splicing. The various modulatory mechanisms acting on Brr2 might be exploited to enhance splicing fidelity and to regulate alternative splicing.
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Affiliation(s)
- Eva Absmeier
- a Freie Universität Berlin, Laboratory of Structural Biochemistry , Berlin , Germany
| | - Karine F Santos
- a Freie Universität Berlin, Laboratory of Structural Biochemistry , Berlin , Germany
| | - Markus C Wahl
- a Freie Universität Berlin, Laboratory of Structural Biochemistry , Berlin , Germany.,b Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography , Berlin , Germany
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12
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Mayerle M, Guthrie C. Prp8 retinitis pigmentosa mutants cause defects in the transition between the catalytic steps of splicing. RNA (NEW YORK, N.Y.) 2016; 22:793-809. [PMID: 26968627 PMCID: PMC4836653 DOI: 10.1261/rna.055459.115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 02/11/2016] [Indexed: 05/14/2023]
Abstract
Pre-mRNA splicing must occur with high fidelity and efficiency for proper gene expression. The spliceosome uses DExD/H box helicases to promote on-pathway interactions while simultaneously minimizing errors. Prp8 and Snu114, an EF2-like GTPase, regulate the activity of the Brr2 helicase, promoting RNA unwinding by Brr2 at appropriate points in the splicing cycle and repressing it at others. Mutations linked to retinitis pigmentosa (RP), a disease that causes blindness in humans, map to the Brr2 regulatory region of Prp8. Previous in vitro studies of homologous mutations in Saccharomyces cerevisiaes how that Prp8-RP mutants cause defects in spliceosome activation. Here we show that a subset of RP mutations in Prp8 also causes defects in the transition between the first and second catalytic steps of splicing. Though Prp8-RP mutants do not cause defects in splicing fidelity, they result in an overall decrease in splicing efficiency. Furthermore, genetic analyses link Snu114 GTP/GDP occupancy to Prp8-dependent regulation of Brr2. Our results implicate the transition between the first and second catalytic steps as a critical place in the splicing cycle where Prp8-RP mutants influence splicing efficiency. The location of the Prp8-RP mutants, at the "hinge" that links the Prp8 Jab1-MPN regulatory "tail" to the globular portion of the domain, suggests that these Prp8-RP mutants inhibit regulated movement of the Prp8 Jab1/MPN domain into the Brr2 RNA binding channel to transiently inhibit Brr2. Therefore, in Prp8-linked RP, disease likely results not only from defects in spliceosome assembly and activation, but also because of defects in splicing catalysis.
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Affiliation(s)
- Megan Mayerle
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94143, USA
| | - Christine Guthrie
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94143, USA
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13
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Nguyen THD, Galej WP, Bai XC, Oubridge C, Newman AJ, Scheres SHW, Nagai K. Cryo-EM structure of the yeast U4/U6.U5 tri-snRNP at 3.7 Å resolution. Nature 2016; 530:298-302. [PMID: 26829225 PMCID: PMC4762201 DOI: 10.1038/nature16940] [Citation(s) in RCA: 162] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 12/18/2015] [Indexed: 12/12/2022]
Abstract
U4/U6.U5 tri-snRNP represents a substantial part of the spliceosome before activation. A cryoEM structure of Saccharomyces cerevisiae U4/U6.U5 tri-snRNP at 3.7Å resolution led to an essentially complete atomic model comprising 30 proteins plus U4/U6 and U5 snRNAs. The structure reveals striking interweaving interactions of the protein and RNA components including extended polypeptides penetrating into subunit interfaces. The invariant ACAGAGA sequence of U6 snRNA, which base-pairs with the 5′-splice site during catalytic activation, forms a hairpin stabilised by Dib1 and Prp8 while the adjacent nucleotides interact with the exon binding loop 1 of U5 snRNA. Snu114 harbours GTP but its putative catalytic histidine is held away from the γ-phosphate by hydrogen bonding to a tyrosine in Prp8’s N-terminal domain. Mutation of this histidine to alanine has no detectable effect on yeast growth. The structure provides important new insights into the spliceosome activation process leading to the formation of the catalytic centre.
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Affiliation(s)
| | - Wojciech P Galej
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Xiao-Chen Bai
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Chris Oubridge
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Andrew J Newman
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Sjors H W Scheres
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Kiyoshi Nagai
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
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14
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CryoEM structures of two spliceosomal complexes: starter and dessert at the spliceosome feast. Curr Opin Struct Biol 2016; 36:48-57. [PMID: 26803803 PMCID: PMC4830896 DOI: 10.1016/j.sbi.2015.12.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 12/21/2015] [Indexed: 12/31/2022]
Abstract
Recent advances in cryoEM are revolutionizing our understanding of how molecular machines function. The structure of Saccharomyces cerevisiae U4/U6.U5 tri-snRNP has been revealed. The structure of Schizosaccharomyces pombe U2.U6.U5 spliceosomal complex has been revealed. These structures greatly advanced our understanding of the mechanism of pre-mRNA splicing.
The spliceosome is formed on pre-mRNA substrates from five small nuclear ribonucleoprotein particles (U1, U2, U4/U6 and U5 snRNPs), and numerous non-snRNP factors. Saccharomyces cerevisiae U4/U6.U5 tri-snRNP comprises U5 snRNA, U4/U6 snRNA duplex and approximately 30 proteins and represents a substantial part of the spliceosome before activation. Schizosaccharomyces pombe U2.U6.U5 spliceosomal complex is a post-catalytic intron lariat spliceosome containing U2 and U5 snRNPs, NTC (nineteen complex), NTC-related proteins (NTR), U6 snRNA, and an RNA intron lariat. Two recent papers describe near-complete atomic structures of these complexes based on cryoEM single-particle analysis. The U4/U6.U5 tri-snRNP structure provides crucial insight into the activation mechanism of the spliceosome. The U2.U6.U5 complex reveals the striking architecture of NTC and NTR and important features of the group II intron-like catalytic RNA core remaining after spliced mRNA is released. These two structures greatly advance our understanding of the mechanism of pre-mRNA splicing.
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15
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Absmeier E, Wollenhaupt J, Mozaffari-Jovin S, Becke C, Lee CT, Preussner M, Heyd F, Urlaub H, Lührmann R, Santos KF, Wahl MC. The large N-terminal region of the Brr2 RNA helicase guides productive spliceosome activation. Genes Dev 2015; 29:2576-87. [PMID: 26637280 PMCID: PMC4699386 DOI: 10.1101/gad.271528.115] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 11/13/2015] [Indexed: 01/06/2023]
Abstract
In this study, Absmeier et al. used a combination of X-ray crystallography, cross-linking/mass spectrometry, and in vivo and in vitro biochemical functional investigations to investigate the structural organization, functions, and molecular mechanisms of the NTR of the Brr2 helicase. The findings reveal molecular mechanisms that prevent premature and unproductive tri-snRNP disruption and suggest novel regulation of Brr2-dependent splicing. The Brr2 helicase provides the key remodeling activity for spliceosome catalytic activation, during which it disrupts the U4/U6 di-snRNP (small nuclear RNA protein), and its activity has to be tightly regulated. Brr2 exhibits an unusual architecture, including an ∼500-residue N-terminal region, whose functions and molecular mechanisms are presently unknown, followed by a tandem array of structurally similar helicase units (cassettes), only the first of which is catalytically active. Here, we show by crystal structure analysis of full-length Brr2 in complex with a regulatory Jab1/MPN domain of the Prp8 protein and by cross-linking/mass spectrometry of isolated Brr2 that the Brr2 N-terminal region encompasses two folded domains and adjacent linear elements that clamp and interconnect the helicase cassettes. Stepwise N-terminal truncations led to yeast growth and splicing defects, reduced Brr2 association with U4/U6•U5 tri-snRNPs, and increased ATP-dependent disruption of the tri-snRNP, yielding U4/U6 di-snRNP and U5 snRNP. Trends in the RNA-binding, ATPase, and helicase activities of the Brr2 truncation variants are fully rationalized by the crystal structure, demonstrating that the N-terminal region autoinhibits Brr2 via substrate competition and conformational clamping. Our results reveal molecular mechanisms that prevent premature and unproductive tri-snRNP disruption and suggest novel principles of Brr2-dependent splicing regulation.
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Affiliation(s)
- Eva Absmeier
- Laboratory of Structural Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Jan Wollenhaupt
- Laboratory of Structural Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Sina Mozaffari-Jovin
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
| | - Christian Becke
- Laboratory of Structural Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Chung-Tien Lee
- Research Group Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany; Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, Georg-August-Universität, D-37099 Göttingen, Germany
| | - Marco Preussner
- Laboratory of RNA Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Florian Heyd
- Laboratory of RNA Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Henning Urlaub
- Research Group Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany; Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, Georg-August-Universität, D-37099 Göttingen, Germany
| | - Reinhard Lührmann
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
| | - Karine F Santos
- Laboratory of Structural Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Markus C Wahl
- Laboratory of Structural Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
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16
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Nguyen THD, Galej WP, Bai XC, Savva CG, Newman AJ, Scheres SHW, Nagai K. The architecture of the spliceosomal U4/U6.U5 tri-snRNP. Nature 2015; 523:47-52. [PMID: 26106855 PMCID: PMC4536768 DOI: 10.1038/nature14548] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 05/06/2015] [Indexed: 12/12/2022]
Abstract
U4/U6.U5 tri-snRNP is a 1.5-megadalton pre-assembled spliceosomal complex comprising U5 small nuclear RNA (snRNA), extensively base-paired U4/U6 snRNAs and more than 30 proteins, including the key components Prp8, Brr2 and Snu114. The tri-snRNP combines with a precursor messenger RNA substrate bound to U1 and U2 small nuclear ribonucleoprotein particles (snRNPs), and transforms into a catalytically active spliceosome after extensive compositional and conformational changes triggered by unwinding of the U4 and U6 (U4/U6) snRNAs. Here we use cryo-electron microscopy single-particle reconstruction of Saccharomyces cerevisiae tri-snRNP at 5.9 Å resolution to reveal the essentially complete organization of its RNA and protein components. The single-stranded region of U4 snRNA between its 3' stem-loop and the U4/U6 snRNA stem I is loaded into the Brr2 helicase active site ready for unwinding. Snu114 and the amino-terminal domain of Prp8 position U5 snRNA to insert its loop I, which aligns the exons for splicing, into the Prp8 active site cavity. The structure provides crucial insights into the activation process and the active site of the spliceosome.
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Affiliation(s)
| | - Wojciech P Galej
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Xiao-chen Bai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Christos G Savva
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Andrew J Newman
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Sjors H W Scheres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Kiyoshi Nagai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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17
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Lehalle D, Wieczorek D, Zechi-Ceide RM, Passos-Bueno MR, Lyonnet S, Amiel J, Gordon CT. A review of craniofacial disorders caused by spliceosomal defects. Clin Genet 2015; 88:405-15. [PMID: 25865758 DOI: 10.1111/cge.12596] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 03/26/2015] [Accepted: 04/07/2015] [Indexed: 02/04/2023]
Abstract
The spliceosome is a large ribonucleoprotein complex that removes introns from pre-mRNA transcripts. Mutations in EFTUD2, encoding a component of the major spliceosome, have recently been identified as the cause of mandibulofacial dysostosis, Guion-Almeida type (MFDGA), characterized by mandibulofacial dysostosis, microcephaly, external ear malformations and intellectual disability. Mutations in several other genes involved in spliceosomal function or linked aspects of mRNA processing have also recently been identified in human disorders with specific craniofacial malformations: SF3B4 in Nager syndrome, an acrofacial dysostosis (AFD); SNRPB in cerebrocostomandibular syndrome, characterized by Robin sequence and rib defects; EIF4A3 in the AFD Richieri-Costa-Pereira syndrome, characterized by Robin sequence, median mandibular cleft and limb defects; and TXNL4A in Burn-McKeown syndrome, involving specific craniofacial dysmorphisms. Here, we review phenotypic and molecular aspects of these syndromes. Given the apparent sensitivity of craniofacial development to defects in mRNA processing, it is possible that mutations in other proteins involved in spliceosomal function will emerge in the future as causative for related human disorders.
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Affiliation(s)
- D Lehalle
- Department of Genetics, APHP, Hôpital Necker-Enfants Malades, Paris, France
| | - D Wieczorek
- Institut für Humangenetik, Universitätsklinikum Essen, Essen, Germany
| | - R M Zechi-Ceide
- Departamento de Genetica Clinica, Hospital de Reabilitacao de Anomalias Craniofaciais, Universidade de Sao Paulo (HRAC-USP), Bauru, Brasil
| | - M R Passos-Bueno
- Centro de Estudos do Genoma Humano, Instituto de Biociencias, Universidade de Sao Paulo, Sao Paulo, Brasil
| | - S Lyonnet
- Department of Genetics, APHP, Hôpital Necker-Enfants Malades, Paris, France.,INSERM UMR 1163, Institut Imagine, Paris, France.,Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Paris, France
| | - J Amiel
- Department of Genetics, APHP, Hôpital Necker-Enfants Malades, Paris, France.,INSERM UMR 1163, Institut Imagine, Paris, France.,Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Paris, France
| | - C T Gordon
- INSERM UMR 1163, Institut Imagine, Paris, France.,Université Paris Descartes-Sorbonne Paris Cité, Institut Imagine, Paris, France
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18
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O’Connor BP, Danhorn T, De Arras L, Flatley BR, Marcus RA, Farias-Hesson E, Leach SM, Alper S. Regulation of toll-like receptor signaling by the SF3a mRNA splicing complex. PLoS Genet 2015; 11:e1004932. [PMID: 25658809 PMCID: PMC4450051 DOI: 10.1371/journal.pgen.1004932] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 12/02/2014] [Indexed: 12/31/2022] Open
Abstract
The innate immune response plays a key role in fighting infection by activating inflammation and stimulating the adaptive immune response. However, chronic activation of innate immunity can contribute to the pathogenesis of many diseases with an inflammatory component. Thus, various negatively acting factors turn off innate immunity subsequent to its activation to ensure that inflammation is self-limiting and to prevent inflammatory disease. These negatively acting pathways include the production of inhibitory acting alternate proteins encoded by alternative mRNA splice forms of genes in Toll-like receptor (TLR) signaling pathways. We previously found that the SF3a mRNA splicing complex was required for a robust innate immune response; SF3a acts to promote inflammation in part by inhibiting the production of a negatively acting splice form of the TLR signaling adaptor MyD88. Here we inhibit SF3a1 using RNAi and subsequently perform an RNAseq study to identify the full complement of genes and splicing events regulated by SF3a in murine macrophages. Surprisingly, in macrophages, SF3a has significant preference for mRNA splicing events within innate immune signaling pathways compared with other biological pathways, thereby affecting the splicing of specific genes in the TLR signaling pathway to modulate the innate immune response. Within minutes after we are exposed to pathogens, our bodies react with a rapid response known as the “innate immune response.” This arm of the immune response regulates the process of inflammation, in which various immune cells are recruited to sites of infection and are activated to produce a host of antimicrobial compounds. This response is critical to fight infection. However, this response, if it is activated too strongly or if it becomes chronic, can do damage and can contribute to numerous very common diseases ranging from atherosclerosis to asthma to cancer. Thus it is essential that this response be tightly regulated, turned on when we have an infection, and turned off when not needed. We are investigating a mechanism that helps turn off this response, to ensure that inflammation is limited to prevent inflammatory disease. This mechanism involves the production of alternate forms of RNAs and proteins that control inflammation. We have discovered that a protein known as SF3a1 can regulate the expression of these alternate inhibitory RNA forms and are investigating how to use this knowledge to better control inflammation.
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Affiliation(s)
- Brian P. O’Connor
- Department of Pediatrics, National Jewish Health, Denver, Colorado, United States of America
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
- Department of Biomedical Research, National Jewish Health, Denver, Colorado, United States of America
- Department of Immunology and Microbiology, University of Colorado, Aurora, Colorado, United States of America
| | - Thomas Danhorn
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Lesly De Arras
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Brenna R. Flatley
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
- Department of Biomedical Research, National Jewish Health, Denver, Colorado, United States of America
- Department of Immunology and Microbiology, University of Colorado, Aurora, Colorado, United States of America
| | - Roland A. Marcus
- Department of Pediatrics, National Jewish Health, Denver, Colorado, United States of America
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Eveline Farias-Hesson
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Sonia M. Leach
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Scott Alper
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
- Department of Biomedical Research, National Jewish Health, Denver, Colorado, United States of America
- Department of Immunology and Microbiology, University of Colorado, Aurora, Colorado, United States of America
- * E-mail:
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19
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De Arras L, Laws R, Leach SM, Pontis K, Freedman JH, Schwartz DA, Alper S. Comparative genomics RNAi screen identifies Eftud2 as a novel regulator of innate immunity. Genetics 2014; 197:485-96. [PMID: 24361939 PMCID: PMC4063909 DOI: 10.1534/genetics.113.160499] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 12/15/2013] [Indexed: 01/08/2023] Open
Abstract
The extent of the innate immune response is regulated by many positively and negatively acting signaling proteins. This allows for proper activation of innate immunity to fight infection while ensuring that the response is limited to prevent unwanted complications. Thus mutations in innate immune regulators can lead to immune dysfunction or to inflammatory diseases such as arthritis or atherosclerosis. To identify novel innate immune regulators that could affect infectious or inflammatory disease, we have taken a comparative genomics RNAi screening approach in which we inhibit orthologous genes in the nematode Caenorhabditis elegans and murine macrophages, expecting that genes with evolutionarily conserved function also will regulate innate immunity in humans. Here we report the results of an RNAi screen of approximately half of the C. elegans genome, which led to the identification of many candidate genes that regulate innate immunity in C. elegans and mouse macrophages. One of these novel conserved regulators of innate immunity is the mRNA splicing regulator Eftud2, which we show controls the alternate splicing of the MyD88 innate immunity signaling adaptor to modulate the extent of the innate immune response.
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Affiliation(s)
- Lesly De Arras
- Integrated Department of Immunology, National Jewish Health and University of Colorado, Denver, Colorado 80206 Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
| | - Rebecca Laws
- Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts 02118
| | - Sonia M Leach
- Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
| | - Kyle Pontis
- Integrated Department of Immunology, National Jewish Health and University of Colorado, Denver, Colorado 80206 Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
| | - Jonathan H Freedman
- Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, North Carolina 27709
| | - David A Schwartz
- Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206 Department of Medicine, University of Colorado, Aurora, Colorado 80045
| | - Scott Alper
- Integrated Department of Immunology, National Jewish Health and University of Colorado, Denver, Colorado 80206 Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
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20
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Galej WP, Nguyen THD, Newman AJ, Nagai K. Structural studies of the spliceosome: zooming into the heart of the machine. Curr Opin Struct Biol 2014; 25:57-66. [PMID: 24480332 PMCID: PMC4045393 DOI: 10.1016/j.sbi.2013.12.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 12/09/2013] [Accepted: 12/11/2013] [Indexed: 11/30/2022]
Abstract
Spliceosomes are large, dynamic ribonucleoprotein complexes that catalyse the removal of introns from messenger RNA precursors via a two-step splicing reaction. The recent crystal structure of Prp8 has revealed Reverse Transcriptase-like, Linker and Endonuclease-like domains. The intron branch-point cross-link with the Linker domain of Prp8 in active spliceosomes and together with suppressors of 5' and 3' splice site mutations this unambiguously locates the active site cavity. Structural and mechanistic similarities with group II self-splicing introns have encouraged the notion that the spliceosome is at heart a ribozyme, and recently the ligands for two catalytic magnesium ions were identified within U6 snRNA. They position catalytic divalent metal ions in the same way as Domain V of group II intron RNA, suggesting that the spliceosome and group II intron use the same catalytic mechanisms.
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Affiliation(s)
- Wojciech P Galej
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom.
| | - Thi Hoang Duong Nguyen
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Andrew J Newman
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Kiyoshi Nagai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom.
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21
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Nguyen THD, Li J, Galej WP, Oshikane H, Newman AJ, Nagai K. Structural basis of Brr2-Prp8 interactions and implications for U5 snRNP biogenesis and the spliceosome active site. Structure 2014; 21:910-19. [PMID: 23727230 PMCID: PMC3677097 DOI: 10.1016/j.str.2013.04.017] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 04/08/2013] [Accepted: 04/19/2013] [Indexed: 12/12/2022]
Abstract
The U5 small nuclear ribonucleoprotein particle (snRNP) helicase Brr2 disrupts the U4/U6 small nuclear RNA (snRNA) duplex and allows U6 snRNA to engage in an intricate RNA network at the active center of the spliceosome. Here, we present the structure of yeast Brr2 in complex with the Jab1/MPN domain of Prp8, which stimulates Brr2 activity. Contrary to previous reports, our crystal structure and mutagenesis data show that the Jab1/MPN domain binds exclusively to the N-terminal helicase cassette. The residues in the Jab1/MPN domain, whose mutations in human Prp8 cause the degenerative eye disease retinitis pigmentosa, are found at or near the interface with Brr2, clarifying its molecular pathology. In the cytoplasm, Prp8 forms a precursor complex with U5 snRNA, seven Sm proteins, Snu114, and Aar2, but after nuclear import, Brr2 replaces Aar2 to form mature U5 snRNP. Our structure explains why Aar2 and Brr2 are mutually exclusive and provides important insights into the assembly of U5 snRNP. We report the structure of Brr2 helicase in complex with the Jab1/MPN domain of Prp8 Retinitis pigmentosa mutations in the Jab1/MPN domain of Prp8 disrupt this complex Mechanism is proposed for the U4/U6 snRNA duplex unwinding and spliceosome activation The Brr2-Jab1/MPN and Aar2-Prp8 complexes provide insight into U5 snRNP biogenesis
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22
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Livesay SB, Collier SE, Bitton DA, Bähler J, Ohi MD. Structural and functional characterization of the N terminus of Schizosaccharomyces pombe Cwf10. EUKARYOTIC CELL 2013; 12:1472-89. [PMID: 24014766 PMCID: PMC3837936 DOI: 10.1128/ec.00140-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 09/03/2013] [Indexed: 01/10/2023]
Abstract
The spliceosome is a dynamic macromolecular machine that catalyzes the removal of introns from pre-mRNA, yielding mature message. Schizosaccharomyces pombe Cwf10 (homolog of Saccharomyces cerevisiae Snu114 and human U5-116K), an integral member of the U5 snRNP, is a GTPase that has multiple roles within the splicing cycle. Cwf10/Snu114 family members are highly homologous to eukaryotic translation elongation factor EF2, and they contain a conserved N-terminal extension (NTE) to the EF2-like portion, predicted to be an intrinsically unfolded domain. Using S. pombe as a model system, we show that the NTE is not essential, but cells lacking this domain are defective in pre-mRNA splicing. Genetic interactions between cwf10-ΔNTE and other pre-mRNA splicing mutants are consistent with a role for the NTE in spliceosome activation and second-step catalysis. Characterization of Cwf10-NTE by various biophysical techniques shows that in solution the NTE contains regions of both structure and disorder. The first 23 highly conserved amino acids of the NTE are essential for its role in splicing but when overexpressed are not sufficient to restore pre-mRNA splicing to wild-type levels in cwf10-ΔNTE cells. When the entire NTE is overexpressed in the cwf10-ΔNTE background, it can complement the truncated Cwf10 protein in trans, and it immunoprecipitates a complex similar in composition to the late-stage U5.U2/U6 spliceosome. These data show that the structurally flexible NTE is capable of independently incorporating into the spliceosome and improving splicing function, possibly indicating a role for the NTE in stabilizing conformational rearrangements during a splice cycle.
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Affiliation(s)
- S. Brent Livesay
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Scott E. Collier
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Danny A. Bitton
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Jürg Bähler
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Melanie D. Ohi
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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23
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Abstract
Yeast U5 small nuclear ribonucleoprotein particle (snRNP) is assembled via a cytoplasmic precursor that contains the U5-specific Prp8 protein but lacks the U5-specific Brr2 helicase. Instead, pre-U5 snRNP includes the Aar2 protein not found in mature U5 snRNP or spliceosomes. Aar2p and Brr2p bind competitively to a C-terminal region of Prp8p that comprises consecutive RNase H-like and Jab1/MPN-like domains. To elucidate the molecular basis for this competition, we determined the crystal structure of Aar2p in complex with the Prp8p RNase H and Jab1/MPN domains. Aar2p binds on one side of the RNase H domain and extends its C terminus to the other side, where the Jab1/MPN domain is docked onto a composite Aar2p-RNase H platform. Known Brr2p interaction sites of the Jab1/MPN domain remain available, suggesting that Aar2p-mediated compaction of the Prp8p domains sterically interferes with Brr2p binding. Moreover, Aar2p occupies known RNA-binding sites of the RNase H domain, and Aar2p interferes with binding of U4/U6 di-snRNA to the Prp8p C-terminal region. Structural and functional analyses of phospho-mimetic mutations reveal how phosphorylation reduces affinity of Aar2p for Prp8p and allows Brr2p and U4/U6 binding. Our results show how Aar2p regulates both protein and RNA binding to Prp8p during U5 snRNP assembly.
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24
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Galej WP, Oubridge C, Newman AJ, Nagai K. Crystal structure of Prp8 reveals active site cavity of the spliceosome. Nature 2013; 493:638-43. [PMID: 23354046 PMCID: PMC3672837 DOI: 10.1038/nature11843] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 12/18/2012] [Indexed: 12/21/2022]
Abstract
The active centre of the spliceosome consists of an intricate network formed by U5, U2 and U6 snRNAs, and a pre-mRNA substrate. Prp8, a component of the U5 snRNP, crosslinks extensively with this RNA catalytic core. We present the crystal structure of yeast Prp8 (residues 885-2413) in complex with the U5 snRNP assembly factor Aar2. The structure reveals new tightly associated domains of Prp8 resembling a bacterial group II intron reverse transcriptase and a type II restriction endonuclease. Suppressors of splice site mutations and an intron branchpoint crosslink map to a large cavity formed by the reverse transcriptase thumb, endonuclease-like and the RNaseH-like domains. This cavity is large enough to accommodate the catalytic core of group II intron RNA. The structure provides crucial insights into the architecture of the spliceosome’s active site and reinforces the notion that nuclear pre-mRNA splicing and group II intron splicing have a common origin.
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Affiliation(s)
- Wojciech P Galej
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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25
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Abstract
RNA splicing is one of the fundamental processes in gene expression in eukaryotes. Splicing of pre-mRNA is catalysed by a large ribonucleoprotein complex called the spliceosome, which consists of five small nuclear RNAs and numerous protein factors. The spliceosome is a highly dynamic structure, assembled by sequential binding and release of the small nuclear RNAs and protein factors. DExD/H-box RNA helicases are required to mediate structural changes in the spliceosome at various steps in the assembly pathway and have also been implicated in the fidelity control of the splicing reaction. Other proteins also play key roles in mediating the progression of the spliceosome pathway. In this review, we discuss the functional roles of the protein factors involved in the spliceosome pathway primarily from studies in the yeast system.
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26
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Lines MA, Huang L, Schwartzentruber J, Douglas SL, Lynch DC, Beaulieu C, Guion-Almeida ML, Zechi-Ceide RM, Gener B, Gillessen-Kaesbach G, Nava C, Baujat G, Horn D, Kini U, Caliebe A, Alanay Y, Utine GE, Lev D, Kohlhase J, Grix AW, Lohmann DR, Hehr U, Böhm D, Majewski J, Bulman DE, Wieczorek D, Boycott KM. Haploinsufficiency of a spliceosomal GTPase encoded by EFTUD2 causes mandibulofacial dysostosis with microcephaly. Am J Hum Genet 2012; 90:369-77. [PMID: 22305528 DOI: 10.1016/j.ajhg.2011.12.023] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 12/12/2011] [Accepted: 12/30/2011] [Indexed: 12/11/2022] Open
Abstract
Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EFTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the first multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome.
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Affiliation(s)
- Matthew A Lines
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ontario, Canada
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27
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Abstract
Plant reproduction occurs through the production of gametes by a haploid generation, the gametophyte. Flowering plants have highly reduced male and female gametophytes, called pollen grains and embryo sacs, respectively, consisting of only a few cells. Gametophytes are critical for sexual reproduction, but detailed understanding of their development remains poor as compared to the diploid sporophyte. This article reviews recent progress in understanding the mechanisms underlying gametophytic development and function in flowering plants. The focus is on genes and molecules involved in the processes of initiation, growth, cell specification, and fertilization of the male and female gametophytes derived primarily from studies in model systems.
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Affiliation(s)
- Hong Ma
- State Key Laboratory of Genetic Engineering and School of Life Sciences, Institute of Plant Biology, Fudan University, Shanghai, China
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28
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Sundaresan V, Alandete-Saez M. Pattern formation in miniature: the female gametophyte of flowering plants. Development 2010; 137:179-89. [DOI: 10.1242/dev.030346] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Plant reproduction involves gamete production by a haploid generation, the gametophyte. For flowering plants, a defining characteristic in the evolution from the ‘naked-seed’ plants, or gymnosperms, is a reduced female gametophyte, comprising just seven cells of four different types – a microcosm of pattern formation and gamete specification about which only little is known. However, several genes involved in the differentiation, fertilization and post-fertilization functions of the female gametophyte have been identified and, recently, the morphogenic activity of the plant hormone auxin has been found to mediate patterning and egg cell specification. This article reviews recent progress in understanding the pattern formation, maternal effects and evolution of this essential unit of plant reproduction.
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Affiliation(s)
- Venkatesan Sundaresan
- Department of Plant Biology, University of California, 1 Shields Avenue, Davis, CA 95616, USA
- Department of Plant Sciences, University of California, 1 Shields Avenue, Davis, CA 95616, USA
| | - Monica Alandete-Saez
- Department of Plant Biology, University of California, 1 Shields Avenue, Davis, CA 95616, USA
- Department of Plant Sciences, University of California, 1 Shields Avenue, Davis, CA 95616, USA
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29
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Gunderson FQ, Johnson TL. Acetylation by the transcriptional coactivator Gcn5 plays a novel role in co-transcriptional spliceosome assembly. PLoS Genet 2009; 5:e1000682. [PMID: 19834536 PMCID: PMC2752994 DOI: 10.1371/journal.pgen.1000682] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 09/14/2009] [Indexed: 11/23/2022] Open
Abstract
In the last several years, a number of studies have shown that spliceosome assembly and splicing catalysis can occur co-transcriptionally. However, it has been unclear which specific transcription factors play key roles in coupling splicing to transcription and the mechanisms through which they act. Here we report the discovery that Gcn5, which encodes the histone acetyltransferase (HAT) activity of the SAGA complex, has genetic interactions with the genes encoding the heterodimeric U2 snRNP proteins Msl1 and Lea1. These interactions are dependent upon the HAT activity of Gcn5, suggesting a functional relationship between Gcn5 HAT activity and Msl1/Lea1 function. To understand the relationship between Gcn5 and Msl1/Lea1, we carried out an analysis of Gcn5's role in co-transcriptional recruitment of Msl1 and Lea1 to pre-mRNA and found that Gcn5 HAT activity is required for co-transcriptional recruitment of the U2 snRNP (and subsequent snRNP) components to the branchpoint, while it is not required for U1 recruitment. Although previous studies suggest that transcription elongation can alter co-transcriptional pre-mRNA splicing, we do not observe evidence of defective transcription elongation for these genes in the absence of Gcn5, while Gcn5-dependent histone acetylation is enriched in the promoter regions. Unexpectedly, we also observe Msl1 enrichment in the promoter region for wild-type cells and cells lacking Gcn5, indicating that Msl1 recruitment during active transcription can occur independently of its association at the branchpoint region. These results demonstrate a novel role for acetylation by SAGA in co-transcriptional recruitment of the U2 snRNP and recognition of the intron branchpoint. Pre-messenger RNA splicing, the removal of non-coding RNA sequences (introns) that interrupt the protein-coding sequence of genes, is required for proper gene expression. While recent studies have revealed that intron recognition begins while the RNA is actively being synthesized by RNA polymerase II, little is known about how the proteins involved in gene transcription and RNA splicing interact to coordinate the two reactions. Here we show that the protein complex SAGA, which allows RNA polymerase II to navigate the three-dimensional structure of packaged DNA by acetylating histone proteins, has an additional role in pre-messenger RNA splicing. Our genetic analysis shows that the SAGA complex has functional interactions with specific components of the splicing machinery. Furthermore, SAGA's acetylation activity, which we find to be targeted toward promoter-bound histones of intron-containing genes, is required for proper recruitment of these components to RNA during active transcription. Our work supports a model whereby SAGA–dependent acetylation facilitates recruitment of the splicing machinery to the pre–mRNA for proper co-transcriptional splicing.
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Affiliation(s)
- Felizza Q. Gunderson
- Department of Biology, Molecular Biology Section, University of California San Diego, La Jolla, California, United States of America
| | - Tracy L. Johnson
- Department of Biology, Molecular Biology Section, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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30
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Analysis of synthetic lethality reveals genetic interactions between the GTPase Snu114p and snRNAs in the catalytic core of the Saccharomyces cerevisiae spliceosome. Genetics 2009; 183:497-515-1SI-4SI. [PMID: 19620389 DOI: 10.1534/genetics.109.107243] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conformational changes of snRNAs in the spliceosome required for pre-mRNA splicing are regulated by eight ATPases and one GTPase Snu114p. The Snu114p guanine state regulates U4/U6 unwinding during spliceosome activation and U2/U6 unwinding during spliceosome disassembly through the ATPase Brr2p. We investigated 618 genetic interactions to identify an extensive genetic interaction network between SNU114 and snRNAs. Snu114p G domain alleles were exacerbated by mutations that stabilize U4/U6 base pairing. G domain alleles were made worse by U2 and U6 mutations that stabilize or destabilize U2/U6 base pairing in helix I. Compensatory mutations that restored U2/U6 base pairing in helix I relieved synthetic lethality. Snu114p G domain alleles were also worsened by mutations in U6 predicted to increase 5' splice site base pairing. Both N-terminal and G domain alleles were exacerbated by U5 loop 1 mutations at positions involved in aligning exons while C-terminus alleles were synthetically lethal with U5 internal loop 1 mutations. This suggests a spatial orientation for Snu114p with U5. We propose that the RNA base pairing state is directly or indirectly sensed by the Snu114p G domain allowing the Snu114p C-terminal domain to regulate Brr2p or other proteins to bring about RNA/RNA rearrangements required for splicing.
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31
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Zhang L, Xu T, Maeder C, Bud LO, Shanks J, Nix J, Guthrie C, Pleiss JA, Zhao R. Structural evidence for consecutive Hel308-like modules in the spliceosomal ATPase Brr2. Nat Struct Mol Biol 2009; 16:731-9. [PMID: 19525970 PMCID: PMC2743687 DOI: 10.1038/nsmb.1625] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 05/22/2009] [Indexed: 11/29/2022]
Abstract
Brr2 is a DExD/H-box helicase responsible for U4/U6 unwinding during spliceosomal activation. Brr2 contains two helicase-like domains, each of which is followed by a Sec63 domain with unknown function. We determined the crystal structure of the second Sec63 domain, which unexpectedly resembles domains 4 and 5 of DNA helicase Hel308. This, together with sequence similarities between Brr2’s helicase-like domains and domains 1–3 of Hel308, led us to hypothesize that Brr2 contains two consecutive Hel308-like modules (Hel308-I and II). Our structural model and mutagenesis data suggest that Brr2 shares a similar helicase mechanism with Hel308. We demonstrate that Hel308-II interacts with Prp8 and Snu114 in vitro and in vivo. We further find that the C-terminal region of Prp8 (Prp8-CTR) facilitates the binding of the Brr2/Prp8-CTR complex to U4/U6. Our results have important implications for the mechanism and regulation of Brr2’s activity.
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Affiliation(s)
- Lingdi Zhang
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, Colorado, USA
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32
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Liu M, Yuan L, Liu NY, Shi DQ, Liu J, Yang WC. GAMETOPHYTIC FACTOR 1, involved in pre-mRNA splicing, is essential for megagametogenesis and embryogenesis in Arabidopsis. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2009; 51:261-71. [PMID: 19261069 DOI: 10.1111/j.1744-7909.2008.00783.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
RNA biogenesis is essential and vital for accurate expression of genes. It is obvious that cells cannot continue normal metabolism when RNA splicing is interfered with. sgt13018 is such a mutant, with partial loss of function of GAMETOPHYTIC FACTOR 1 (GFA1); a gene likely involved in RNA biogenesis in Arabidopsis. The mutant is featured in the phenotype of diminished female gametophyte development at stage FG5 and is associated with the arrest of early embryo development in Arabidopsis. Bioinformatics data showed that homologs of gene GFA1 in yeast and human encode putative U5 snRNP-specific proteins required for pre-mRNA splicing. Furthermore, the result of yeast two-hybrid assay indicated that GFA1 physically interacted with AtBrr2 and AtPrp8, the putative U5 snRNP components, of Arabidopsis. This investigation suggests that GFA1 is involved in mRNA biogenesis through interaction with AtBrr2 and AtPrp8 and functions in megagametogenesis and embryogenesis in plant.
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Affiliation(s)
- Man Liu
- Key Laboratory of Molecular and Developmental Biology, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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33
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Yagi N, Takeda S, Matsumoto N, Okada K. VAJ/GFA1/CLO is involved in the directional control of floral organ growth. PLANT & CELL PHYSIOLOGY 2009; 50:515-527. [PMID: 19168457 DOI: 10.1093/pcp/pcp011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Flowers assume variant forms of reproductive structures, a phenomenon which may be partially due to the diversity among species in the shape and size of floral organs. However, the organ size and shape of flowers usually remain constant within a species when grown under the same environmental conditions. The molecular and genetic mechanisms that control organ size and shape are largely unknown. We isolated an Arabidopsis mutant, vajra-1 (vaj-1), exhibiting defects in the regulation of floral organ size and shape. In vaj-1, alterations in the size and shape of floral organs were caused by changes in both cell size and cell number. The vaj-1 mutation also affected the number of floral organs. In vaj-1, a mutation was found in GAMETOPHYTIC FACTOR 1 (GFA1)/CLOTHO (CLO), recently shown to be required for female gametophyte development. The VAJ/GFA1/CLO gene encodes a translational elongation factor-2 (EF-2) family protein, of which the human U5-116 kD and yeast Snu114p counterparts are U5 small nuclear ribonucleoprotein (snRNP)-specific proteins. A transient expression assay using Arabidopsis protoplasts revealed that VAJ protein co-localized with SC35, a serine/arginine-rich (SR) protein involved in pre-mRNA splicing. Our results showed that VAJ/GFA1/CLO has a novel role in the directional control of floral organ growth in Arabidopsis, possibly acting through pre-mRNA splicing.
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Affiliation(s)
- Noriyoshi Yagi
- Department of Botany, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, Kyoto 606-8502, Japan
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34
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Moll C, von Lyncker L, Zimmermann S, Kägi C, Baumann N, Twell D, Grossniklaus U, Gross-Hardt R. CLO/GFA1 and ATO are novel regulators of gametic cell fate in plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 56:913-21. [PMID: 18702672 DOI: 10.1111/j.1365-313x.2008.03650.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The formation of gametes is a key step in the life cycle of any sexually reproducing organism. In flowering plants, gametes develop in haploid structures termed gametophytes that comprise a few cells. The female gametophyte forms gametic cells and flanking accessory cells. During a screen for regulators of egg-cell fate, we isolated three mutants, lachesis (lis), clotho (clo) and atropos (ato), that show deregulated expression of an egg-cell marker. We have previously shown that, in lis mutants, which are defective for the splicing factor PRP4, accessory cells can differentiate gametic cell fate. Here, we show that CLOTHO/GAMETOPHYTIC FACTOR 1 (CLO/GFA1) is necessary for the restricted expression of egg- and central-cell fate and hence reproductive success. Surprisingly, infertile gametophytes can be expelled from the maternal ovule tissue, thereby preventing the needless allocation of maternal resources to sterile tissue. CLO/GFA1 encodes the Arabidopsis homologue of Snu114, a protein that is considered to be an essential component of the spliceosome. In agreement with their proposed role in pre-mRNA splicing, CLO/GFA1 and LIS co-localize to nuclear speckles. Our data also suggest that CLO/GFA1 is necessary for the tissue-specific expression of LIS. Furthermore, we demonstrate that ATO encodes the Arabidopsis homologue of SF3a60, a protein that has been implicated in pre-spliceosome formation. Our results thus establish that the restriction of gametic cell fate is specifically coupled to the function of various core spliceosomal components.
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Affiliation(s)
- Cordula Moll
- ZMBP Developmental Genetics, University of Tübingen, D-72076 Tübingen, Germany
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35
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Abstract
Pre-mRNA splicing is an essential step in gene expression where intron regions are removed and coding exon sequences are joined to form an mRNA for translation. Splicing is catalysed by an RNA-protein complex called the spliceosome. A number of spliceosome proteins are required for assembly and remodelling of the spliceosome with pre-mRNA to orient the splice sites correctly and catalyse the two steps of splicing. The spliceosome protein Snu114p is a GTPase that is related to the translation elongation factor EF-2. Snu114p plays a key role in spliceosome remodelling. In the present review, we briefly summarize the current knowledge of the function of Snu114p in pre-mRNA splicing and the role it plays in spliceosome dynamics.
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36
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Localization of Prp8, Brr2, Snu114 and U4/U6 proteins in the yeast tri-snRNP by electron microscopy. Nat Struct Mol Biol 2008; 15:1206-12. [DOI: 10.1038/nsmb.1506] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Accepted: 09/26/2008] [Indexed: 12/22/2022]
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37
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Bellare P, Small EC, Huang X, Wohlschlegel JA, Staley JP, Sontheimer EJ. A role for ubiquitin in the spliceosome assembly pathway. Nat Struct Mol Biol 2008; 15:444-51. [PMID: 18425143 DOI: 10.1038/nsmb.1401] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 02/13/2008] [Indexed: 01/15/2023]
Abstract
The spliceosome uses numerous strategies to regulate its function in mRNA maturation. Ubiquitin regulates many cellular processes, but its potential roles during splicing are unknown. We have developed a new strategy that reveals a direct role for ubiquitin in the dynamics of splicing complexes. A ubiquitin mutant (I44A) that can enter the conjugation pathway but is compromised in downstream functions diminishes splicing activity by reducing the levels of the U4/U6-U5 small nuclear ribonucleoprotein (snRNP). Similarly, an inhibitor of ubiquitin's protein-protein interactions, ubistatin A, reduces U4/U6-U5 triple snRNP levels in vitro. When ubiquitin interactions are blocked, ATP-dependent disassembly of purified U4/U6-U5 particles is accelerated, indicating a direct role for ubiquitin in repressing U4/U6 unwinding. Finally, we show that the conserved splicing factor Prp8 is ubiquitinated within purified triple snRNPs. These results reveal a previously unknown ubiquitin-dependent mechanism for controlling the pre-mRNA splicing pathway.
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Affiliation(s)
- Priya Bellare
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, 2205 Tech Drive, Evanston, Illinois 60208, USA
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38
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McManus CJ, Schwartz ML, Butcher SE, Brow DA. A dynamic bulge in the U6 RNA internal stem-loop functions in spliceosome assembly and activation. RNA (NEW YORK, N.Y.) 2007; 13:2252-65. [PMID: 17925343 PMCID: PMC2080595 DOI: 10.1261/rna.699907] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 08/15/2007] [Indexed: 05/20/2023]
Abstract
The highly conserved internal stem-loop (ISL) of U6 spliceosomal RNA is unwound for U4/U6 complex formation during spliceosome assembly and reformed upon U4 release during spliceosome activation. The U6 ISL is structurally similar to Domain 5 of group II self-splicing introns, and contains a dynamic bulge that coordinates a Mg++ ion essential for the first catalytic step of splicing. We have analyzed the causes of growth defects resulting from mutations in the Saccharomyces cerevisiae U6 ISL-bulged nucleotide U80 and the adjacent C67-A79 base pair. Intragenic suppressors and enhancers of the cold-sensitive A79G mutation, which replaces the C-A pair with a C-G pair, suggest that it stabilizes the ISL, inhibits U4/U6 assembly, and may also disrupt spliceosome activation. The lethality of mutations C67A and C67G results from disruption of base-pairing potential between U4 and U6, as these mutations are fully suppressed by compensatory mutations in U4 RNA. Strikingly, suppressor analysis shows that the lethality of the U80G mutation is due not only to formation of a stable base pair with C67, as previously proposed, but also another defect. A U6-U80G strain in which mispairing with position 67 is prevented grows poorly and assembles aberrant spliceosomes that retain U1 snRNP and fail to fully unwind the U4/U6 complex at elevated temperatures. Our data suggest that the U6 ISL bulge is important for coupling U1 snRNP release with U4/U6 unwinding during spliceosome activation.
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Affiliation(s)
- C Joel McManus
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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39
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prp8 mutations that cause human retinitis pigmentosa lead to a U5 snRNP maturation defect in yeast. Nat Struct Mol Biol 2007; 14:1077-83. [PMID: 17934474 DOI: 10.1038/nsmb1303] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Accepted: 08/28/2007] [Indexed: 12/12/2022]
Abstract
Prp8 protein (Prp8p) is a highly conserved pre-mRNA splicing factor and a component of spliceosomal U5 small nuclear ribonucleoproteins (snRNPs). Although it is ubiquitously expressed, mutations in the C terminus of human Prp8p cause the retina-specific disease retinitis pigmentosa (RP). The biogenesis of U5 snRNPs is poorly characterized. We present evidence for a cytoplasmic precursor U5 snRNP in yeast that lacks the mature U5 snRNP component Brr2p and depends on a nuclear localization signal in Prp8p for its efficient nuclear import. The association of Brr2p with the U5 snRNP occurs within the nucleus. RP mutations in Prp8p in yeast result in nuclear accumulation of the precursor U5 snRNP, apparently as a consequence of disrupting the interaction of Prp8p with Brr2p. We therefore propose a novel assembly pathway for U5 snRNP complexes that is disrupted by mutations that cause human RP.
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40
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Valadkhan S. The spliceosome: caught in a web of shifting interactions. Curr Opin Struct Biol 2007; 17:310-5. [PMID: 17574835 DOI: 10.1016/j.sbi.2007.05.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 03/27/2007] [Accepted: 05/25/2007] [Indexed: 11/23/2022]
Abstract
Splicing is a crucial, ubiquitous and highly complex step in eukaryotic gene expression. The daunting complexity of the splicing reaction, although fascinating, has severely limited our understanding of its mechanistic details. Recent advances have begun to provide exciting new insights into the dynamic interactions that govern the function of the spliceosome, the multi-megadalton complex that performs splicing. An emerging paradigm is the presence of a succession of distinct conformational states, which are stabilized by an intricate network of interactions. Recent data suggest that even subtle changes in the composition of the interaction network can result in interconversion of the different conformational states, providing opportunities for regulation and proofreading of spliceosome function. Significant progress in proteomics has elucidated the protein composition of the spliceosome at different stages of assembly. Also, the increased sophistication and resolution of cryo-electron microscopy techniques, combined with high-resolution structural studies on a smaller scale, promise to create detailed images of the global structure of the spliceosome and its main components, which in turn will provide a plethora of mechanistic insights. Overall, the past two years have seen a convergence of data from different lines of research into what promises to become a holistic picture of spliceosome function.
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Affiliation(s)
- Saba Valadkhan
- Center for RNA Molecular Biology, Case Western Reserve University, 10900 Euclid Avenue, Wood RT 100-8, Cleveland, OH 44106, USA.
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41
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Segregation distortion in Arabidopsis gametophytic factor 1 (gfa1) mutants is caused by a deficiency of an essential RNA splicing factor. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/s00497-007-0046-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Small EC, Leggett SR, Winans AA, Staley JP. The EF-G-like GTPase Snu114p regulates spliceosome dynamics mediated by Brr2p, a DExD/H box ATPase. Mol Cell 2006; 23:389-99. [PMID: 16885028 PMCID: PMC3777414 DOI: 10.1016/j.molcel.2006.05.043] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Revised: 05/30/2006] [Accepted: 05/31/2006] [Indexed: 11/26/2022]
Abstract
Binding of a pre-mRNA substrate triggers spliceosome activation, whereas the release of the mRNA product triggers spliceosome disassembly. The mechanisms that underlie the regulation of these rearrangements remain unclear. We find evidence that the GTPase Snu114p mediates the regulation of spliceosome activation and disassembly. Specifically, both unwinding of U4/U6, required for spliceosome activation, and disassembly of the postsplicing U2/U6.U5.intron complex are repressed by Snu114p bound to GDP and derepressed by Snu114p bound to GTP or nonhydrolyzable GTP analogs. Further, similar to U4/U6 unwinding, spliceosome disassembly requires the DExD/H box ATPase Brr2p. Together, our data define a common mechanism for regulating and executing spliceosome activation and disassembly. Although sequence similarity with EF-G suggests Snu114p functions as a molecular motor, our findings indicate that Snu114p functions as a classic regulatory G protein. We propose that Snu114p serves as a signal-dependent switch that transduces signals to Brr2p to control spliceosome dynamics.
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Affiliation(s)
- Eliza C. Small
- Department of Biochemistry and Molecular Biology, The University of Chicago Chicago, IL 60637
| | - Stephanie R. Leggett
- Department of Molecular Genetics and Cell Biology The University of Chicago Chicago, IL 60637
| | - Adrienne A. Winans
- Department of Molecular Genetics and Cell Biology The University of Chicago Chicago, IL 60637
| | - Jonathan P. Staley
- Department of Molecular Genetics and Cell Biology The University of Chicago Chicago, IL 60637
- Correspondence: 773-834-5886 (phone); 773-834-9064 (fax)
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Boon KL, Auchynnikava T, Edwalds-Gilbert G, Barrass JD, Droop AP, Dez C, Beggs JD. Yeast ntr1/spp382 mediates prp43 function in postspliceosomes. Mol Cell Biol 2006; 26:6016-23. [PMID: 16880513 PMCID: PMC1592814 DOI: 10.1128/mcb.02347-05] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Ntr1 and Ntr2 proteins of Saccharomyces cerevisiae have been reported to interact with proteins involved in pre-mRNA splicing, but their roles in the splicing process are unknown. We show here that they associate with a postsplicing complex containing the excised intron and the spliceosomal U2, U5, and U6 snRNAs, supporting a link with a late stage in the pre-mRNA splicing process. Extract from cells that had been metabolically depleted of Ntr1 has low splicing activity and accumulates the excised intron. Also, the level of U4/U6 di-snRNP is increased but those of the free U5 and U6 snRNPs are decreased in Ntr1-depleted extract, and increased levels of U2 and decreased levels of U4 are found associated with the U5 snRNP protein Prp8. These results suggest a requirement for Ntr1 for turnover of the excised intron complex and recycling of snRNPs. Ntr1 interacts directly or indirectly with the intron release factor Prp43 and is required for its association with the excised intron. We propose that Ntr1 promotes release of excised introns from splicing complexes by acting as a spliceosome receptor or RNA-targeting factor for Prp43, possibly assisted by the Ntr2 protein.
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Affiliation(s)
- Kum-Loong Boon
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, United Kingdom
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44
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Liu S, Rauhut R, Vornlocher HP, Lührmann R. The network of protein-protein interactions within the human U4/U6.U5 tri-snRNP. RNA (NEW YORK, N.Y.) 2006; 12:1418-30. [PMID: 16723661 PMCID: PMC1484429 DOI: 10.1261/rna.55406] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The human 25S U4/U6.U5 tri-snRNP is a major building block of the U2-type spliceosome and contains, in addition to the U4, U6, and U5 snRNAs, at least 30 distinct proteins. To learn more about the molecular architecture of the tri-snRNP, we have investigated interactions between tri-snRNP proteins using the yeast two-hybrid assay and in vitro binding assays, and, in addition, have identified distinct protein domains that are critical for the connectivity of this protein network in the human tri-snRNP. These studies revealed multiple interactions between distinct domains of the U5 proteins hPrp8, hBrr2 (a DExH/D-box helicase), and hSnu114 (a putative GTPase), which are key players in the catalytic activation of the spliceosome, during which the U4/U6 base-pairing interaction is disrupted and U4 is released from the spliceosome. Both the U5-specific, TPR/HAT-repeat-containing hPrp6 protein and the tri-snRNP-specific hSnu66 protein interact with several U5- and U4/U6-associated proteins, including hBrr2 and hPrp3, which contacts the U6 snRNA. Thus, both proteins are located at the interface between U5 and U4/U6 in the tri-snRNP complex, and likely play an important role in transmitting the activity of hBrr2 and hSnu114 in the U5 snRNP to the U4/U6 duplex during spliceosome activation. A more detailed analysis of these protein interactions revealed that different HAT repeats mediate interactions with specific hPrp6 partners. Taken together, data presented here provide a detailed picture of the network of protein interactions within the human tri-snRNP.
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Affiliation(s)
- Sunbin Liu
- Department of Cellular Biochemistry, MPI of Biophysical Chemistry, Göttingen, Germany
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45
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Brenner TJ, Guthrie C. Assembly of Snu114 into U5 snRNP requires Prp8 and a functional GTPase domain. RNA (NEW YORK, N.Y.) 2006; 12:862-71. [PMID: 16540695 PMCID: PMC1440915 DOI: 10.1261/rna.2319806] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Snu114 is a U5 snRNP protein essential for pre-mRNA splicing. Based on its homology with the ribosomal translocase EF-G, it is thought that GTP hydrolysis by Snu114 induces conformational rearrangements in the spliceosome. We recently identified allele-specific genetic interactions between SNU114 and genes encoding three other U5 snRNP components, Prp8 and two RNA-dependent ATPases, Prp28 and Brr2, required for destabilization of U1 and U4 snRNPs prior to catalysis. To shed more light onto the function of Snu114, we have now directly analyzed snRNP and spliceosome assembly in SNU114 mutant extracts. The Snu114-60 C-terminal truncation mutant, which is synthetically lethal with the ATPase mutants prp28-1 and brr2-1, assembles spliceosomes but subsequently blocks U4 snRNP release. Conversely, mutants in the GTPase domain fail to assemble U5 snRNPs. These mutations prevent the interaction of Snu114 with Prp8 as well as with U5 snRNA. Since Prp8 is thought to regulate the activity of the DEAD-box ATPases, this strategy of snRNP assembly could ensure that Prp8 activity is itself regulated by a GTP-dependent mechanism.
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Affiliation(s)
- Tamara J Brenner
- Department of Biochemistry and Biophysics, University of California, San Francisco 94143-2200, USA
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46
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Boon KL, Norman CM, Grainger RJ, Newman AJ, Beggs JD. Prp8p dissection reveals domain structure and protein interaction sites. RNA (NEW YORK, N.Y.) 2006; 12:198-205. [PMID: 16373487 PMCID: PMC1370899 DOI: 10.1261/rna.2281306] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We describe a novel approach to characterize the functional domains of a protein in vivo. This involves the use of a custom-built Tn5-based transposon that causes the expression of a target gene as two contiguous polypeptides. When used as a genetic screen to dissect the budding yeast PRP8 gene, this showed that Prp8 protein could be dissected into three distinct pairs of functional polypeptides. Thus, four functional domains can be defined in the 2413-residue Prp8 protein, with boundaries in the regions of amino acids 394-443, 770, and 2170-2179. The central region of the protein was resistant to dissection by this approach, suggesting that it represents one large functional unit. The dissected constructs allowed investigation of factors that associate strongly with the N- or the C-terminal Prp8 protein fragments. Thus, the U5 snRNP protein Snu114p associates with Prp8p in the region 437-770, whereas fragmenting Prp8p at residue 2173 destabilizes its association with Aar2p.
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Affiliation(s)
- Kum-Loong Boon
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, UK
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Brenner TJ, Guthrie C. Genetic analysis reveals a role for the C terminus of the Saccharomyces cerevisiae GTPase Snu114 during spliceosome activation. Genetics 2005; 170:1063-80. [PMID: 15911574 PMCID: PMC1451163 DOI: 10.1534/genetics.105.042044] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Snu114 is the only GTPase required for mRNA splicing. As a homolog of elongation factor G, it contains three domains (III-V) predicted to undergo a large rearrangement following GTP hydrolysis. To assess the functional importance of the domains of Snu114, we used random mutagenesis to create conditionally lethal alleles. We identified three main classes: (1) mutations that are predicted to affect GTP binding and hydrolysis, (2) mutations that are clustered in 10- to 20-amino-acid stretches in each of domains III-V, and (3) mutations that result in deletion of up to 70 amino acids from the C terminus. Representative mutations from each of these classes blocked the first step of splicing in vivo and in vitro. The growth defects caused by most alleles were synthetically exacerbated by mutations in PRP8, a U5 snRNP protein that physically interacts with Snu114, as well as in genes involved in snRNP biogenesis, including SAD1 and BRR1. The allele snu114-60, which truncates the C terminus, was synthetically lethal with factors required for activation of the spliceosome, including the DExD/H-box ATPases BRR2 and PRP28. We propose that GTP hydrolysis results in a rearrangement between Prp8 and the C terminus of Snu114 that leads to release of U1 and U4, thus activating the spliceosome for catalysis.
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Affiliation(s)
| | - Christine Guthrie
- Corresponding author: Department of Biochemistry and Biophysics, 600 16th St., Genentech Hall, San Francisco, CA 94143-2200. E-mail:
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48
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Abstract
Pre-messenger RNA (pre-mRNA) splicing is a central step in gene expression. Lying between transcription and protein synthesis, pre-mRNA splicing removes sequences (introns) that would otherwise disrupt the coding potential of intron-containing transcripts. This process takes place in the nucleus, catalyzed by a large RNA-protein complex called the spliceosome. Prp8p, one of the largest and most highly conserved of nuclear proteins, occupies a central position in the catalytic core of the spliceosome, and has been implicated in several crucial molecular rearrangements that occur there. Recently, Prp8p has also come under the spotlight for its role in the inherited human disease, Retinitis Pigmentosa.Prp8 is unique, having no obvious homology to other proteins; however, using bioinformatical analysis we reveal the presence of a conserved RNA recognition motif (RRM), an MPN/JAB domain and a putative nuclear localization signal (NLS). Here, we review biochemical and genetical data, mostly related to the human and yeast proteins, that describe Prp8's central role within the spliceosome and its molecular interactions during spliceosome formation, as splicing proceeds, and in post-splicing complexes.
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Affiliation(s)
- Richard J Grainger
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, United Kingdom
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Turner IA, Norman CM, Churcher MJ, Newman AJ. Roles of the U5 snRNP in spliceosome dynamics and catalysis. Biochem Soc Trans 2005; 32:928-31. [PMID: 15506927 DOI: 10.1042/bst0320928] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Most protein-coding genes in eukaryotes are interrupted by non-coding intervening sequences (introns), which must be precisely removed from primary gene transcripts (pre-mRNAs) before translation of the message into protein. Intron removal by pre-mRNA splicing occurs in the nucleus and is catalysed by complex ribonucleoprotein machines called spliceosomes. These molecular machines consist of several small nuclear RNA molecules and their associated proteins [together termed snRNP (small nuclear ribonucleoprotein) particles], plus multiple accessory factors. Of particular interest are the U2, U5 and U6 snRNPs, which play crucial roles in the catalytic steps of splicing. In the present review, we summarize our current understanding of the role played by the protein components of the U5 snRNP in pre-mRNA splicing, which include some of the largest and most highly conserved nuclear proteins.
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Affiliation(s)
- I A Turner
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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50
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Abstract
RNA is structurally very flexible, which provides the basis for its functional diversity. An RNA molecule can often adopt different conformations, which enables the regulation of its function through folding. Proteins help RNAs reach their functionally active conformation by increasing their structural stability or by chaperoning the folding process. Large, dynamic RNA-protein complexes, such as the ribosome or the spliceosome, require numerous proteins that coordinate conformational switches of the RNA components during assembly and during their respective activities.
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Affiliation(s)
- Renée Schroeder
- Max F. Perutz Laboratories, Department of Microbiology and Genetics, University of Vienna, Austria.
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