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Truong A, Barton M, Tran U, Mellody M, Berger D, Madory D, Hitch E, Jibrael B, Nikolaidis N, Luchko T, Keppetipola N. Unstructured linker regions play a role in the differential splicing activities of paralogous RNA binding proteins PTBP1 and PTBP2. J Biol Chem 2024; 300:105733. [PMID: 38336291 PMCID: PMC10914480 DOI: 10.1016/j.jbc.2024.105733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 01/23/2024] [Accepted: 02/02/2024] [Indexed: 02/12/2024] Open
Abstract
RNA Binding Proteins regulate, in part, alternative pre-mRNA splicing and, in turn, gene expression patterns. Polypyrimidine tract binding proteins PTBP1 and PTBP2 are paralogous RNA binding proteins sharing 74% amino acid sequence identity. Both proteins contain four structured RNA-recognition motifs (RRMs) connected by linker regions and an N-terminal region. Despite their similarities, the paralogs have distinct tissue-specific expression patterns and can regulate discrete sets of target exons. How two highly structurally similar proteins can exert different splicing outcomes is not well understood. Previous studies revealed that PTBP2 is post-translationally phosphorylated in the unstructured N-terminal, Linker 1, and Linker 2 regions that share less sequence identity with PTBP1 signifying a role for these regions in dictating the paralog's distinct splicing activities. To this end, we conducted bioinformatics analysis to determine the evolutionary conservation of RRMs versus linker regions in PTBP1 and PTBP2 across species. To determine the role of PTBP2 unstructured regions in splicing activity, we created hybrid PTBP1-PTBP2 constructs that had counterpart PTBP1 regions swapped to an otherwise PTBP2 protein and assayed on differentially regulated exons. We also conducted molecular dynamics studies to investigate how negative charges introduced by phosphorylation in PTBP2 unstructured regions can alter their physical properties. Collectively, results from our studies reveal an important role for PTBP2 unstructured regions and suggest a role for phosphorylation in the differential splicing activities of the paralogs on certain regulated exons.
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Affiliation(s)
- Anthony Truong
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California, USA
| | - Michael Barton
- Department of Physics and Astronomy, California State University, Northridge, Northridge, California, USA
| | - Uyenphuong Tran
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California, USA
| | - Montana Mellody
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California, USA
| | - Devon Berger
- Department of Biological Sciences, California State University Fullerton, Fullerton, California, USA
| | - Dean Madory
- Department of Biological Science, Santa Ana College, Santa Ana, California, USA
| | - Elizabeth Hitch
- Department of Biological Sciences, California State University Fullerton, Fullerton, California, USA
| | - Basma Jibrael
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California, USA
| | - Nikolas Nikolaidis
- Department of Biological Sciences, California State University Fullerton, Fullerton, California, USA
| | - Tyler Luchko
- Department of Physics and Astronomy, California State University, Northridge, Northridge, California, USA.
| | - Niroshika Keppetipola
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California, USA.
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Li D, Wang Q, Bayat A, Battig MR, Zhou Y, Bosch DG, van Haaften G, Granger L, Petersen AK, Pérez-Jurado LA, Aznar-Laín G, Aneja A, Hancarova M, Bendova S, Schwarz M, Kremlikova Pourova R, Sedlacek Z, Keena BA, March ME, Hou C, O’Connor N, Bhoj EJ, Harr MH, Lemire G, Boycott KM, Towne M, Li M, Tarnopolsky M, Brady L, Parker MJ, Faghfoury H, Parsley LK, Agolini E, Dentici ML, Novelli A, Wright M, Palmquist R, Lai K, Scala M, Striano P, Iacomino M, Zara F, Cooper A, Maarup TJ, Byler M, Lebel RR, Balci TB, Louie R, Lyons M, Douglas J, Nowak C, Afenjar A, Hoyer J, Keren B, Maas SM, Motazacker MM, Martinez-Agosto JA, Rabani AM, McCormick EM, Falk MJ, Ruggiero SM, Helbig I, Møller RS, Tessarollo L, Tomassoni Ardori F, Palko ME, Hsieh TC, Krawitz PM, Ganapathi M, Gelb BD, Jobanputra V, Wilson A, Greally J, Jacquemont S, Jizi K, Bruel AL, Quelin C, Misra VK, Chick E, Romano C, Greco D, Arena A, Morleo M, Nigro V, Seyama R, Uchiyama Y, Matsumoto N, Taira R, Tashiro K, Sakai Y, Yigit G, Wollnik B, Wagner M, Kutsche B, Hurst AC, Thompson ML, Schmidt R, Randolph L, Spillmann RC, Shashi V, Higginbotham EJ, Cordeiro D, Carnevale A, Costain G, Khan T, Funalot B, Tran Mau-Them F, Fernandez Garcia Moya L, García-Miñaúr S, Osmond M, Chad L, Quercia N, Carrasco D, Li C, Sanchez-Valle A, Kelley M, Nizon M, Jensson BO, Sulem P, Stefansson K, Gorokhova S, Busa T, Rio M, Hadj Habdallah H, Lesieur-Sebellin M, Amiel J, Pingault V, Mercier S, Vincent M, Philippe C, Fatus-Fauconnier C, Friend K, Halligan RK, Biswas S, Rosser J, Shoubridge C, Corbett M, Barnett C, Gecz J, Leppig K, Slavotinek A, Marcelis C, Pfundt R, de Vries BB, van Slegtenhorst MA, Brooks AS, Cogne B, Rambaud T, Tümer Z, Zackai EH, Akizu N, Song Y, Hakonarson H. Spliceosome malfunction causes neurodevelopmental disorders with overlapping features. J Clin Invest 2024; 134:e171235. [PMID: 37962958 PMCID: PMC10760965 DOI: 10.1172/jci171235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 10/31/2023] [Indexed: 11/16/2023] Open
Abstract
Pre-mRNA splicing is a highly coordinated process. While its dysregulation has been linked to neurological deficits, our understanding of the underlying molecular and cellular mechanisms remains limited. We implicated pathogenic variants in U2AF2 and PRPF19, encoding spliceosome subunits in neurodevelopmental disorders (NDDs), by identifying 46 unrelated individuals with 23 de novo U2AF2 missense variants (including 7 recurrent variants in 30 individuals) and 6 individuals with de novo PRPF19 variants. Eight U2AF2 variants dysregulated splicing of a model substrate. Neuritogenesis was reduced in human neurons differentiated from human pluripotent stem cells carrying two U2AF2 hyper-recurrent variants. Neural loss of function (LoF) of the Drosophila orthologs U2af50 and Prp19 led to lethality, abnormal mushroom body (MB) patterning, and social deficits, which were differentially rescued by wild-type and mutant U2AF2 or PRPF19. Transcriptome profiling revealed splicing substrates or effectors (including Rbfox1, a third splicing factor), which rescued MB defects in U2af50-deficient flies. Upon reanalysis of negative clinical exomes followed by data sharing, we further identified 6 patients with NDD who carried RBFOX1 missense variants which, by in vitro testing, showed LoF. Our study implicates 3 splicing factors as NDD-causative genes and establishes a genetic network with hierarchy underlying human brain development and function.
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Affiliation(s)
- Dong Li
- Center for Applied Genomics, and
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Qin Wang
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Allan Bayat
- Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
- Department for Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | | | - Yijing Zhou
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Daniëlle G.M. Bosch
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Gijs van Haaften
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Leslie Granger
- Department of Genetics and Metabolism, Randall Children’s Hospital at Legacy Emanuel Medical Center, Portland, Oregon, USA
| | - Andrea K. Petersen
- Department of Genetics and Metabolism, Randall Children’s Hospital at Legacy Emanuel Medical Center, Portland, Oregon, USA
| | - Luis A. Pérez-Jurado
- Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain
- Genetic Service, Hospital del Mar Research Institute (IMIM), Barcelona, Spain
- Universitat Pompeu Fabra, Barcelona, Spain
| | - Gemma Aznar-Laín
- Universitat Pompeu Fabra, Barcelona, Spain
- Pediatric Neurology, Hospital del Mar Research Institute (IMIM), Barcelona, Spain
| | - Anushree Aneja
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Miroslava Hancarova
- Department of Biology and Medical Genetics, Charles University Second Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Sarka Bendova
- Department of Biology and Medical Genetics, Charles University Second Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Martin Schwarz
- Department of Biology and Medical Genetics, Charles University Second Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Radka Kremlikova Pourova
- Department of Biology and Medical Genetics, Charles University Second Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Zdenek Sedlacek
- Department of Biology and Medical Genetics, Charles University Second Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Beth A. Keena
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | | | | | | | - Elizabeth J. Bhoj
- Center for Applied Genomics, and
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | | | - Gabrielle Lemire
- Children’s Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Kym M. Boycott
- Children’s Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Megan Li
- Invitae, San Francisco, California, USA
| | - Mark Tarnopolsky
- Division of Neuromuscular and Neurometabolic Disorders, Department of Paediatrics, McMaster University Children’s Hospital, Hamilton, Ontario, Canada
| | - Lauren Brady
- Division of Neuromuscular and Neurometabolic Disorders, Department of Paediatrics, McMaster University Children’s Hospital, Hamilton, Ontario, Canada
| | - Michael J. Parker
- Department of Clinical Genetics, Sheffield Children’s Hospital, Sheffield, United Kingdom
| | | | - Lea Kristin Parsley
- University of Illinois College of Medicine, Mercy Health Systems, Rockford, Illinois, USA
| | - Emanuele Agolini
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy
| | - Maria Lisa Dentici
- Medical Genetics Unit, Academic Department of Pediatrics, IRCCS, Ospedale Pediatrico Bambino Gesù, Rome, Italy
- Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
| | - Antonio Novelli
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy
| | - Meredith Wright
- Rady Children’s Institute for Genomic Medicine, San Diego, California, USA
| | - Rachel Palmquist
- Division of Pediatric Neurology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Khanh Lai
- Division of Pediatric Pulmonary and Sleep Medicine, University of Utah, Salt Lake City, Utah, USA
| | - Marcello Scala
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, Università Degli Studi di Genova, Genoa, Italy
- Pediatric Neurology and Muscular Diseases Unit, and
| | - Pasquale Striano
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, Università Degli Studi di Genova, Genoa, Italy
- Pediatric Neurology and Muscular Diseases Unit, and
| | - Michele Iacomino
- Medical Genetics Unit, IRCCS, Istituto Giannina Gaslini, Genoa, Italy
| | - Federico Zara
- Medical Genetics Unit, IRCCS, Istituto Giannina Gaslini, Genoa, Italy
| | - Annina Cooper
- Department of Genetics, Southern California Permanente Medical Group, Kaiser Permanente, San Diego, California, USA
| | - Timothy J. Maarup
- Department of Genetics, Kaiser Permanente, Los Angeles, California, USA
| | - Melissa Byler
- Center for Development, Behavior and Genetics, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Robert Roger Lebel
- Center for Development, Behavior and Genetics, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Tugce B. Balci
- Division of Genetics, Department of Paediatrics, London Health Sciences Centre, London, Ontario, Canada
| | - Raymond Louie
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Michael Lyons
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Jessica Douglas
- Division of Genetics and Genomics, Boston Children’s Hospital, Boston, Massachusetts, USA
| | - Catherine Nowak
- Division of Genetics and Metabolism, Mass General Hospital for Children, Boston, Massachusetts, USA
| | - Alexandra Afenjar
- APHP. SU, Reference Center for Intellectual Disabilities Caused by Rare Causes, Department of Genetics and Medical Embryology, Hôpital Trousseau, Paris, France
| | - Juliane Hoyer
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Boris Keren
- Department of Genetics, Hospital Pitié-Salpêtrière, Paris, France
| | - Saskia M. Maas
- Department of Human Genetics, Academic Medical Center, and
| | - Mahdi M. Motazacker
- Laboratory of Genome Diagnostics, Department of Human Genetics, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Ahna M. Rabani
- Division of Medical Genetics, Department of Pediatrics, UCLA, Los Angeles, California, USA
| | - Elizabeth M. McCormick
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics
| | - Marni J. Falk
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics
| | - Sarah M. Ruggiero
- Division of Neurology, and
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Ingo Helbig
- Division of Neurology, and
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Rikke S. Møller
- Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark
| | - Lino Tessarollo
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute (NCI), Frederick, Maryland, USA
| | - Francesco Tomassoni Ardori
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute (NCI), Frederick, Maryland, USA
| | - Mary Ellen Palko
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute (NCI), Frederick, Maryland, USA
| | - Tzung-Chien Hsieh
- Institute for Genomic Statistics and Bioinformatics, University Hospital Bonn, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Peter M. Krawitz
- Institute for Genomic Statistics and Bioinformatics, University Hospital Bonn, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Mythily Ganapathi
- New York Genome Center, New York, New York, USA
- Department of Pathology, Columbia University Irving Medical Center, New York, New York, USA
| | - Bruce D. Gelb
- Mindich Child Health and Development Institute and the Departments of Pediatrics and Genetics and Genomic Sciences, Icahn School of Medicine, New York, New York, USA
| | - Vaidehi Jobanputra
- New York Genome Center, New York, New York, USA
- Department of Pathology, Columbia University Irving Medical Center, New York, New York, USA
| | | | - John Greally
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Sébastien Jacquemont
- Division of Genetics and Genomics, CHU Ste-Justine Hospital and CHU Sainte-Justine Research Centre, University of Montreal, Montreal, Quebec, Canada
| | - Khadijé Jizi
- Division of Genetics and Genomics, CHU Ste-Justine Hospital and CHU Sainte-Justine Research Centre, University of Montreal, Montreal, Quebec, Canada
| | - Ange-Line Bruel
- INSERM UMR 1231, Genetics of Developmental Anomalies, Université de Bourgogne Franche-Comté, Dijon, France
- UF Innovation en Diagnostic Génomique des Maladies Rares, CHU Dijon Bourgogne, Dijon, France
- FHU-TRANSLAD, Fédération Hospitalo-Universitaire Translational Medicine in Developmental Anomalies, CHU Dijon Bourgogne, Dijon, France
| | - Chloé Quelin
- Medical Genetics Department, Centre de Référence Maladies Rares CLAD-Ouest, CHU Hôpital Sud, Rennes, France
| | - Vinod K. Misra
- Division of Genetic, Genomic, and Metabolic Disorders, Children’s Hospital of Michigan, Detroit, Michigan, USA
- Central Michigan University College of Medicine, Discipline of Pediatrics, Mount Pleasant, Michigan, USA
| | - Erika Chick
- Division of Genetic, Genomic, and Metabolic Disorders, Children’s Hospital of Michigan, Detroit, Michigan, USA
| | - Corrado Romano
- Research Unit of Rare Diseases and Neurodevelopmental Disorders, Oasi Research Institute-IRCCS, Troina, Italy
- Medical Genetics, Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | | | | | - Manuela Morleo
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Naples, Italy
- Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, Naples, Italy
| | - Vincenzo Nigro
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Naples, Italy
- Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, Naples, Italy
| | - Rie Seyama
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
- Department of Obstetrics and Gynecology, Juntendo University, Tokyo, Japan
| | - Yuri Uchiyama
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
- Department of Rare Disease Genomics, Yokohama City University Hospital, Yokohama, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Ryoji Taira
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Katsuya Tashiro
- Department of Pediatrics, Karatsu Red Cross Hospital, Saga, Japan
| | - Yasunari Sakai
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Gökhan Yigit
- Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany
- DZHK (German Center for Cardiovascular Research), partner site Göttingen, Göttingen, Germany
| | - Bernd Wollnik
- Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany
- DZHK (German Center for Cardiovascular Research), partner site Göttingen, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), University of Göttingen, Göttingen, Germany
| | - Michael Wagner
- Kinderzentrum Oldenburg, Sozialpädiatrisches Zentrum, Diakonisches Werk Oldenburg, Oldenburg, Germany
| | - Barbara Kutsche
- Kinderzentrum Oldenburg, Sozialpädiatrisches Zentrum, Diakonisches Werk Oldenburg, Oldenburg, Germany
| | - Anna C.E. Hurst
- Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | | | - Ryan Schmidt
- Department of Pathology and Laboratory Medicine, Children’s Hospital Los Angeles, Los Angeles, California, USA
- Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
| | - Linda Randolph
- Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
- Division of Medical Genetics, Children’s Hospital Los Angeles, California, USA
| | - Rebecca C. Spillmann
- Department of Pediatrics–Medical Genetics, Duke University School of Medicine, Durham, North Carolina, USA
| | - Vandana Shashi
- Department of Pediatrics–Medical Genetics, Duke University School of Medicine, Durham, North Carolina, USA
| | | | - Dawn Cordeiro
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Amanda Carnevale
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Gregory Costain
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Tayyaba Khan
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Benoît Funalot
- Department of Genetics, Hôpital Henri-Mondor APHP and CHI Creteil, University Paris Est Creteil, IMRB, Inserm U.955, Creteil, France
| | - Frederic Tran Mau-Them
- INSERM UMR 1231, Genetics of Developmental Anomalies, Université de Bourgogne Franche-Comté, Dijon, France
- UF Innovation en Diagnostic Génomique des Maladies Rares, CHU Dijon Bourgogne, Dijon, France
| | | | - Sixto García-Miñaúr
- Institute of Medical and Molecular Genetics (INGEMM), Hospital Universitario La Paz, Madrid, Spain
| | - Matthew Osmond
- Children’s Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Lauren Chad
- Department of Pediatrics, Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Nada Quercia
- Department of Genetic Counselling, Division of Clinical and Metabolic Genetics, Hospital for Sick Children, Ottawa, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Diana Carrasco
- Department of Clinical Genetics, Cook Children’s Hospital, Fort Worth, Texas, USA
| | - Chumei Li
- Division of Genetics, Department of Paediatrics, McMaster University, Hamilton, Ontario, Canada
| | - Amarilis Sanchez-Valle
- Division of Genetics and Metabolism, Department of Pediatrics, University of South Florida, Tampa, Florida, USA
| | - Meghan Kelley
- Division of Genetics and Metabolism, Department of Pediatrics, University of South Florida, Tampa, Florida, USA
| | - Mathilde Nizon
- Nantes Université, CHU Nantes, Medical Genetics Department, Nantes, France
- Nantes Université, CNRS, INSERM, l’Institut du Thorax, Nantes, France
| | | | | | - Kari Stefansson
- deCODE genetics/Amgen Inc., Reykjavik, Iceland
- Faculty of Medicine, School of Health Sciences, University of Iceland, Reykjavik, Iceland
| | - Svetlana Gorokhova
- Aix Marseille University, Inserm, U1251-MMG, Marseille Medical Genetics, Marseille, France
- Department of Medical Genetics, Timone Hospital, APHM, Marseille, France
| | - Tiffany Busa
- Department of Medical Genetics, Timone Hospital, APHM, Marseille, France
| | - Marlène Rio
- Department of Genomic Medicine of Rare Disorders, Necker Hospital, APHP Center, University Paris Cité, Paris, France
| | - Hamza Hadj Habdallah
- Department of Genomic Medicine of Rare Disorders, Necker Hospital, APHP Center, University Paris Cité, Paris, France
| | - Marion Lesieur-Sebellin
- Department of Genomic Medicine of Rare Disorders, Necker Hospital, APHP Center, University Paris Cité, Paris, France
| | - Jeanne Amiel
- Rare Disease Genetics Department, APHP, Hôpital Necker, Paris, France
- Université Paris Cité, Inserm, Institut Imagine, Embryology and Genetics of Malformations Laboratory, Paris, France
| | - Véronique Pingault
- Rare Disease Genetics Department, APHP, Hôpital Necker, Paris, France
- Université Paris Cité, Inserm, Institut Imagine, Embryology and Genetics of Malformations Laboratory, Paris, France
- Laboratoire de Biologie Médicale Multi-Sites SeqOIA (laboratoire-seqoia.fr), Paris, France
| | - Sandra Mercier
- Nantes Université, CHU Nantes, Medical Genetics Department, Nantes, France
- Nantes Université, CNRS, INSERM, l’Institut du Thorax, Nantes, France
| | - Marie Vincent
- Nantes Université, CHU Nantes, Medical Genetics Department, Nantes, France
- Nantes Université, CNRS, INSERM, l’Institut du Thorax, Nantes, France
| | - Christophe Philippe
- INSERM UMR 1231, Genetics of Developmental Anomalies, Université de Bourgogne Franche-Comté, Dijon, France
| | | | - Kathryn Friend
- Genetics and Molecular Pathology, SA Pathology, Adelaide, South Australia, Australia
| | | | | | - Jane Rosser
- Department of General Medicine, Women’s and Children’s Hospital, Adelaide, South Australia, Australia
| | - Cheryl Shoubridge
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, South Australia, Australia
| | - Mark Corbett
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, South Australia, Australia
| | - Christopher Barnett
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, South Australia, Australia
- Pediatric and Reproductive Genetics Unit, Women’s and Children’s Hospital, North Adelaide, South Australia, Australia
| | - Jozef Gecz
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
| | - Kathleen Leppig
- Genetic Services, Kaiser Permenante of Washington, Seattle, Washington, USA
| | - Anne Slavotinek
- Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA
| | - Carlo Marcelis
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rolph Pfundt
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bert B.A. de Vries
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Alice S. Brooks
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Benjamin Cogne
- Nantes Université, CHU Nantes, Medical Genetics Department, Nantes, France
- Nantes Université, CNRS, INSERM, l’Institut du Thorax, Nantes, France
- Laboratoire de Biologie Médicale Multi-Sites SeqOIA (laboratoire-seqoia.fr), Paris, France
| | - Thomas Rambaud
- Laboratoire de Biologie Médicale Multi-Sites SeqOIA (laboratoire-seqoia.fr), Paris, France
| | - Zeynep Tümer
- Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Glostrup, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Elaine H. Zackai
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Naiara Akizu
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Yuanquan Song
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Hakon Hakonarson
- Center for Applied Genomics, and
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
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Farshadyeganeh P, Nazim M, Zhang R, Ohkawara B, Nakajima K, Rahman MA, Nasrin F, Ito M, Takeda JI, Ohe K, Miyasaka Y, Ohno T, Masuda A, Ohno K. Splicing regulation of GFPT1 muscle-specific isoform and its roles in glucose metabolisms and neuromuscular junction. iScience 2023; 26:107746. [PMID: 37744035 PMCID: PMC10514471 DOI: 10.1016/j.isci.2023.107746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 07/29/2023] [Accepted: 08/24/2023] [Indexed: 09/26/2023] Open
Abstract
Glutamine:fructose-6-phosphate transaminase 1 (GFPT1) is the rate-limiting enzyme of the hexosamine biosynthetic pathway (HBP). A 54-bp exon 9 of GFPT1 is specifically included in skeletal and cardiac muscles to generate a long isoform of GFPT1 (GFPT1-L). We showed that SRSF1 and Rbfox1/2 cooperatively enhance, and hnRNP H/F suppresses, the inclusion of human GFPT1 exon 9 by modulating recruitment of U1 snRNP. Knockout (KO) of GFPT1-L in skeletal muscle markedly increased the amounts of GFPT1 and UDP-HexNAc, which subsequently suppressed the glycolytic pathway. Aged KO mice showed impaired insulin-mediated glucose uptake, as well as muscle weakness and fatigue likely due to abnormal formation and maintenance of the neuromuscular junction. Taken together, GFPT1-L is likely to be acquired in evolution in mammalian striated muscles to attenuate the HBP for efficient glycolytic energy production, insulin-mediated glucose uptake, and the formation and maintenance of the neuromuscular junction.
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Affiliation(s)
- Paniz Farshadyeganeh
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Mohammad Nazim
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ruchen Zhang
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Kazuki Nakajima
- Institute for Glyco-core Research (iGCORE), Gifu University, Gifu 501-1193, Japan
| | - Mohammad Alinoor Rahman
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Department of Biochemistry and Molecular Biology, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences (UAMS), Little Rock, AR 72205, USA
| | - Farhana Nasrin
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Department of Biochemistry and Molecular Biology, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences (UAMS), Little Rock, AR 72205, USA
| | - Mikako Ito
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Jun-ichi Takeda
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Kenji Ohe
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan
| | - Yuki Miyasaka
- Division of Experimental Animals, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Tamio Ohno
- Division of Experimental Animals, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Akio Masuda
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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Mukherjee A, Nongthomba U. To RNA-binding and beyond: Emerging facets of the role of Rbfox proteins in development and disease. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023:e1813. [PMID: 37661850 DOI: 10.1002/wrna.1813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 07/23/2023] [Accepted: 07/25/2023] [Indexed: 09/05/2023]
Abstract
The RNA-binding Fox-1 homologue (Rbfox) proteins represent an ancient family of splicing factors, conserved through evolution. All members share an RNA recognition motif (RRM), and a particular affinity for the GCAUG signature in target RNA molecules. The role of Rbfox, as a splice factor, deciding the tissue-specific inclusion/exclusion of an exon, depending on its binding position on the flanking introns, is well known. Rbfox often acts in concert with other splicing factors, and forms splicing regulatory networks. Apart from this canonical role, recent studies show that Rbfox can also function as a transcription co-factor, and affects mRNA stability and translation. The repertoire of Rbfox targets is vast, including genes involved in the development of tissue lineages, such as neurogenesis, myogenesis, and erythropoeiesis, and molecular processes, including cytoskeletal dynamics, and calcium handling. A second layer of complexity is added by the fact that Rbfox expression itself is regulated by multiple mechanisms, and, in vertebrates, exhibits tissue-specific expression. The optimum dosage of Rbfox is critical, and its misexpression is etiological to various disease conditions. In this review, we discuss the contextual roles played by Rbfox as a tissue-specific regulator for the expression of many important genes with diverse functions, through the lens of the emerging data which highlights its involvement in many human diseases. Furthermore, we explore the mechanistic details provided by studies in model organisms, with emphasis on the work with Drosophila. This article is categorized under: RNA Processing > Splicing Mechanisms RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Turnover and Surveillance > Regulation of RNA Stability RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
- Amartya Mukherjee
- Department of Developmental Biology and Genetics, Indian Institute of Science, Bangalore, India
| | - Upendra Nongthomba
- Department of Developmental Biology and Genetics, Indian Institute of Science, Bangalore, India
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5
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Chen X, Yang HT, Zhang B, Phillips JW, Cheng D, Rigo F, Witte ON, Xing Y, Black DL. The RNA-binding proteins hnRNP H and F regulate splicing of a MYC-dependent HRAS exon in prostate cancer cells. Proc Natl Acad Sci U S A 2023; 120:e2220190120. [PMID: 37399401 PMCID: PMC10334793 DOI: 10.1073/pnas.2220190120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 05/31/2023] [Indexed: 07/05/2023] Open
Abstract
The MYC proto-oncogene contributes to the pathogenesis of more than half of human cancers. Malignant transformation by MYC transcriptionally up-regulates the core pre-mRNA splicing machinery and causes misregulation of alternative splicing. However, our understanding of how splicing changes are directed by MYC is limited. We performed a signaling pathway-guided splicing analysis to identify MYC-dependent splicing events. These included an HRAS cassette exon repressed by MYC across multiple tumor types. To molecularly dissect the regulation of this HRAS exon, we used antisense oligonucleotide tiling to identify splicing enhancers and silencers in its flanking introns. RNA-binding motif prediction indicated multiple binding sites for hnRNP H and hnRNP F within these cis-regulatory elements. Using siRNA knockdown and cDNA expression, we found that both hnRNP H and F activate the HRAS cassette exon. Mutagenesis and targeted RNA immunoprecipitation implicate two downstream G-rich elements in this splicing activation. Analyses of ENCODE RNA-seq datasets confirmed hnRNP H regulation of HRAS splicing. Analyses of RNA-seq datasets across multiple cancers showed a negative correlation of HNRNPH gene expression with MYC hallmark enrichment, consistent with the effect of hnRNP H on HRAS splicing. Interestingly, HNRNPF expression showed a positive correlation with MYC hallmarks and thus was not consistent with the observed effects of hnRNP F. Loss of hnRNP H/F altered cell cycle progression and induced apoptosis in the PC3 prostate cancer cell line. Collectively, our results reveal mechanisms for MYC-dependent regulation of splicing and point to possible therapeutic targets in prostate cancers.
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Affiliation(s)
- Xinyuan Chen
- Molecular Biology Interdepartmental Doctoral Program, University of California, Los Angeles, CA90095
| | - Harry Taegyun Yang
- Bioinformatics Interdepartmental Graduate Program, University of California, Los Angeles, CA90095
| | - Beatrice Zhang
- Center for Computational and Genomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA19104
| | - John W. Phillips
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
| | - Donghui Cheng
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
| | - Frank Rigo
- Ionis Pharmaceuticals, Inc., 2855 Gazelle Ct., Carlsbad, CA92010
| | - Owen N. Witte
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA90095
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA90095
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA90095
- Molecular Biology Institute, University of California, Los Angeles, CA90095
| | - Yi Xing
- Center for Computational and Genomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA19104
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Douglas L. Black
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA90095
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA90095
- Molecular Biology Institute, University of California, Los Angeles, CA90095
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6
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Koh E, Shin D, Kim KS. Exon definitive regions for MPC1 microexon splicing and its usage for splicing modulation. MOLECULAR THERAPY. NUCLEIC ACIDS 2023; 31:398-410. [PMID: 36817727 PMCID: PMC9929638 DOI: 10.1016/j.omtn.2023.01.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 01/20/2023] [Indexed: 01/26/2023]
Abstract
Alternative splicing of microexons (3-30 base pairs [bp]) is involved in important biological processes in brain development and human cancers. However, understanding a splicing process of non-3x bp microexons is scarce. We showed that 4 bp microexon of mitochondrial pyruvate carrier1 (MPC1) is constitutively included in mRNA. Based on our studies with minigene and exon island constructs, we found the strong exon definition region in the proximal introns bordering MPC1 microexon. Ultimately, we defined a nucleotide fragment from the 3'ss 67 bp of MPC1 microexon to the 5'ss consensus sequence, as a core exon island, which can concatenate its microexon and neighboring exons by splicing. Furthermore, we showed that insertion of the core exon island into a target exon or intron induced skip the target exon or enhance the splicing of an adjacent exon, respectively. Collectively, we suggest that the exon island derived from MPC1 microexon modifies genuine splicing patterns depending on its position, thereby providing insights on strategies for splicing-mediated gene correction.
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Affiliation(s)
- Eunjin Koh
- Department of Biochemistry and Molecular Biology, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 03722, Korea
| | - Daye Shin
- Department of Biochemistry and Molecular Biology, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 03722, Korea
| | - Kyung-Sup Kim
- Department of Biochemistry and Molecular Biology, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 03722, Korea,Corresponding author: Kyung-Sup Kim, Department of Biochemistry and Molecular Biology, Institute of Genetic Science, College of Medicine, Yonsei University, Seoul 03722, Korea.
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7
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Horn T, Gosliga A, Li C, Enculescu M, Legewie S. Position-dependent effects of RNA-binding proteins in the context of co-transcriptional splicing. NPJ Syst Biol Appl 2023; 9:1. [PMID: 36653378 PMCID: PMC9849329 DOI: 10.1038/s41540-022-00264-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 12/08/2022] [Indexed: 01/19/2023] Open
Abstract
Alternative splicing is an important step in eukaryotic mRNA pre-processing which increases the complexity of gene expression programs, but is frequently altered in disease. Previous work on the regulation of alternative splicing has demonstrated that splicing is controlled by RNA-binding proteins (RBPs) and by epigenetic DNA/histone modifications which affect splicing by changing the speed of polymerase-mediated pre-mRNA transcription. The interplay of these different layers of splicing regulation is poorly understood. In this paper, we derived mathematical models describing how splicing decisions in a three-exon gene are made by combinatorial spliceosome binding to splice sites during ongoing transcription. We additionally take into account the effect of a regulatory RBP and find that the RBP binding position within the sequence is a key determinant of how RNA polymerase velocity affects splicing. Based on these results, we explain paradoxical observations in the experimental literature and further derive rules explaining why the same RBP can act as inhibitor or activator of cassette exon inclusion depending on its binding position. Finally, we derive a stochastic description of co-transcriptional splicing regulation at the single-cell level and show that splicing outcomes show little noise and follow a binomial distribution despite complex regulation by a multitude of factors. Taken together, our simulations demonstrate the robustness of splicing outcomes and reveal that quantitative insights into kinetic competition of co-transcriptional events are required to fully understand this important mechanism of gene expression diversity.
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Affiliation(s)
- Timur Horn
- grid.424631.60000 0004 1794 1771Institute of Molecular Biology (IMB), Ackermannweg 4, 55128 Mainz, Germany
| | - Alison Gosliga
- grid.424631.60000 0004 1794 1771Institute of Molecular Biology (IMB), Ackermannweg 4, 55128 Mainz, Germany ,grid.5719.a0000 0004 1936 9713University of Stuttgart, Department of Systems Biology and Stuttgart Research Center Systems Biology (SRCSB), Allmandring 31, 70569 Stuttgart, Germany
| | - Congxin Li
- grid.5719.a0000 0004 1936 9713University of Stuttgart, Department of Systems Biology and Stuttgart Research Center Systems Biology (SRCSB), Allmandring 31, 70569 Stuttgart, Germany
| | - Mihaela Enculescu
- Institute of Molecular Biology (IMB), Ackermannweg 4, 55128, Mainz, Germany.
| | - Stefan Legewie
- Institute of Molecular Biology (IMB), Ackermannweg 4, 55128, Mainz, Germany. .,University of Stuttgart, Department of Systems Biology and Stuttgart Research Center Systems Biology (SRCSB), Allmandring 31, 70569, Stuttgart, Germany.
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8
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Paterson HAB, Yu S, Artigas N, Prado MA, Haberman N, Wang YF, Jobbins AM, Pahita E, Mokochinski J, Hall Z, Guerin M, Paulo JA, Ng SS, Villarroya F, Rashid ST, Le Goff W, Lenhard B, Cebola I, Finley D, Gygi SP, Sibley CR, Vernia S. Liver RBFOX2 regulates cholesterol homeostasis via Scarb1 alternative splicing in mice. Nat Metab 2022; 4:1812-1829. [PMID: 36536133 PMCID: PMC9771820 DOI: 10.1038/s42255-022-00681-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 10/10/2022] [Indexed: 12/24/2022]
Abstract
RNA alternative splicing (AS) expands the regulatory potential of eukaryotic genomes. The mechanisms regulating liver-specific AS profiles and their contribution to liver function are poorly understood. Here, we identify a key role for the splicing factor RNA-binding Fox protein 2 (RBFOX2) in maintaining cholesterol homeostasis in a lipogenic environment in the liver. Using enhanced individual-nucleotide-resolution ultra-violet cross-linking and immunoprecipitation, we identify physiologically relevant targets of RBFOX2 in mouse liver, including the scavenger receptor class B type I (Scarb1). RBFOX2 function is decreased in the liver in diet-induced obesity, causing a Scarb1 isoform switch and alteration of hepatocyte lipid homeostasis. Our findings demonstrate that specific AS programmes actively maintain liver physiology, and underlie the lipotoxic effects of obesogenic diets when dysregulated. Splice-switching oligonucleotides targeting this network alleviate obesity-induced inflammation in the liver and promote an anti-atherogenic lipoprotein profile in the blood, underscoring the potential of isoform-specific RNA therapeutics for treating metabolism-associated diseases.
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Affiliation(s)
- Helen A B Paterson
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Sijia Yu
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Natalia Artigas
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Miguel A Prado
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Instituto de Investigación Sanitaria del Principado de Asturias, Avenida Hospital Universitario, Oviedo, Spain
| | - Nejc Haberman
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Yi-Fang Wang
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Andrew M Jobbins
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Elena Pahita
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Joao Mokochinski
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Zoe Hall
- Division of Systems Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Maryse Guerin
- Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Paris, France
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Soon Seng Ng
- Division of Systems Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Francesc Villarroya
- Biochemistry and Molecular Biomedicine Department, Institute of Biomedicine, University of Barcelona & Research Institute Sant Joan de Déu, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), ISCIII, Madrid, Spain
| | - Sheikh Tamir Rashid
- Division of Systems Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Wilfried Le Goff
- Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Paris, France
| | - Boris Lenhard
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Inês Cebola
- Section of Genetics and Genomics, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Christopher R Sibley
- Institute of Quantitative Biology, Biochemistry and Biotechnology. School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Santiago Vernia
- MRC London Institute of Medical Sciences, London, UK.
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK.
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9
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Ontiveros RJ, Hernandez L, Nguyen H, Hernandez Lopez AL, Shankar A, Kim E, Keppetipola NM. Identification and Characterization of a Minimal Functional Splicing Regulatory Protein, PTBP1. Biochemistry 2020; 59:4766-4774. [PMID: 33284593 DOI: 10.1021/acs.biochem.0c00664] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polypyrimidine tract binding protein 1 (PTBP1) is a well-studied RNA binding protein that serves as an important model for understanding molecular mechanisms underlying alternative splicing regulation. PTBP1 has four RNA binding domains (RBDs) connected via linker regions. Additionally, PTBP1 has an N-terminal unstructured region that contains nuclear import and export sequences. Each RBD can bind to pyrimidine rich elements with high affinity to mediate splicing activity. Studies support a variety of models for how PTBP1 can mediate splicing regulation on target exons. Obtaining a detailed atomic view hinges on determining a crystal structure of PTBP1 bound to a target RNA transcript. Here, we created a minimal functional PTBP1 with deletions in both linker 1 and linker 2 regions and assayed for activity on certain regulated exons, including the c-Src N1 exon. We show that for a subset of PTBP1-regulated exons the linker regions are not necessary for splicing repression activity. Gel mobility shift assays reveal the linker deletion mutant binds with 12-fold higher affinity to a target RNA sequence compared to wild-type PTBP1. A minimal PTBP1 that also contains an N-terminal region deletion binds to a target RNA with an affinity higher than that of wild-type PTBP1. Moreover, this minimal protein oligomerizes readily to form a distinct higher-order complex previously shown to be required for mediating splicing repression. This minimal functional PTBP1 protein can serve as a candidate for future structure studies to understand the mechanism of splicing repression for certain regulated exons.
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Affiliation(s)
- Robert J Ontiveros
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Luis Hernandez
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Haylena Nguyen
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California 92831, United States
| | - Adrian Lino Hernandez Lopez
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90035, United States
| | - Archana Shankar
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Enoch Kim
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Niroshika M Keppetipola
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California 92831, United States
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10
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Protein 4.1R Exon 16 3' Splice Site Activation Requires Coordination among TIA1, Pcbp1, and RBM39 during Terminal Erythropoiesis. Mol Cell Biol 2017; 37:MCB.00446-16. [PMID: 28193846 DOI: 10.1128/mcb.00446-16] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 02/03/2017] [Indexed: 12/18/2022] Open
Abstract
Exon 16 of protein 4.1R encodes a spectrin/actin-binding peptide critical for erythrocyte membrane stability. Its expression during erythroid differentiation is regulated by alternative pre-mRNA splicing. A UUUUCCCCCC motif situated between the branch point and the 3' splice site is crucial for inclusion. We show that the UUUU region and the last three C residues in this motif are necessary for the binding of splicing factors TIA1 and Pcbp1 and that these proteins appear to act in a collaborative manner to enhance exon 16 inclusion. This element also activates an internal exon when placed in a corresponding intronic position in a heterologous reporter. The impact of these two factors is further enhanced by high levels of RBM39, whose expression rises during erythroid differentiation as exon 16 inclusion increases. TIA1 and Pcbp1 associate in a complex containing RBM39, which interacts with U2AF65 and SF3b155 and promotes U2 snRNP recruitment to the branch point. Our results provide a mechanism for exon 16 3' splice site activation in which a coordinated effort among TIA1, Pcbp1, and RBM39 stabilizes or increases U2 snRNP recruitment, enhances spliceosome A complex formation, and facilitates exon definition through RBM39-mediated splicing regulation.
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11
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Keppetipola NM, Yeom KH, Hernandez AL, Bui T, Sharma S, Black DL. Multiple determinants of splicing repression activity in the polypyrimidine tract binding proteins, PTBP1 and PTBP2. RNA (NEW YORK, N.Y.) 2016; 22:1172-1180. [PMID: 27288314 PMCID: PMC4931110 DOI: 10.1261/rna.057505.116] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 05/16/2016] [Indexed: 06/06/2023]
Abstract
Most human genes generate multiple protein isoforms through alternative pre-mRNA splicing, but the mechanisms controlling alternative splicing choices by RNA binding proteins are not well understood. These proteins can have multiple paralogs expressed in different cell types and exhibiting different splicing activities on target exons. We examined the paralogous polypyrimidine tract binding proteins PTBP1 and PTBP2 to understand how PTBP1 can exhibit greater splicing repression activity on certain exons. Using both an in vivo coexpression assay and an in vitro splicing assay, we show that PTBP1 is more repressive than PTBP2 per unit protein on a target exon. Constructing chimeras of PTBP1 and 2 to determine amino acid features that contribute to their differential activity, we find that multiple segments of PTBP1 increase the repressive activity of PTBP2. Notably, when either RRM1 of PTBP2 or the linker peptide separating RRM2 and RRM3 are replaced with the equivalent PTBP1 sequences, the resulting chimeras are highly active for splicing repression. These segments are distinct from the known region of interaction for the PTBP1 cofactors Raver1 and Matrin3 in RRM2. We find that RRM2 of PTBP1 also increases the repression activity of an otherwise PTBP2 sequence, and that this is potentially explained by stronger binding by Raver1. These results indicate that multiple features over the length of the two proteins affect their ability to repress an exon.
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Affiliation(s)
- Niroshika M Keppetipola
- California State University Fullerton, Department of Chemistry and Biochemistry, Fullerton, California 92831, USA
| | - Kyu-Hyeon Yeom
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA
| | - Adrian L Hernandez
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA
| | - Tessa Bui
- California State University Fullerton, Department of Chemistry and Biochemistry, Fullerton, California 92831, USA
| | - Shalini Sharma
- Department of Basic Medical Sciences, University of Arizona, College of Medicine-Phoenix, Phoenix, Arizona 85004, USA
| | - Douglas L Black
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA
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12
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Carvalho AS, Penque D, Matthiesen R. Bottom up proteomics data analysis strategies to explore protein modifications and genomic variants. Proteomics 2015; 15:1789-92. [DOI: 10.1002/pmic.201400186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 01/19/2015] [Accepted: 02/09/2015] [Indexed: 11/12/2022]
Affiliation(s)
- Ana Sofia Carvalho
- Computational and Experimental Biology Group; Human Genetics Department; National Health Institute Doutor Ricardo Jorge Lisbon; Portugal
| | - Deborah Penque
- Computational and Experimental Biology Group; Human Genetics Department; National Health Institute Doutor Ricardo Jorge Lisbon; Portugal
| | - Rune Matthiesen
- Computational and Experimental Biology Group; Human Genetics Department; National Health Institute Doutor Ricardo Jorge Lisbon; Portugal
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13
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Alternative Splicing Shapes the Phenotype of a Mutation in BBS8 To Cause Nonsyndromic Retinitis Pigmentosa. Mol Cell Biol 2015; 35:1860-70. [PMID: 25776555 DOI: 10.1128/mcb.00040-15] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 03/10/2015] [Indexed: 01/27/2023] Open
Abstract
Bardet-Biedl syndrome (BBS) is a genetic disorder affecting multiple systems and organs in the body. Several mutations in genes associated with BBS affect only photoreceptor cells and cause nonsyndromic retinitis pigmentosa (RP), raising the issue of why certain mutations manifest as a systemic disorder whereas other changes in the same gene affect only a specific cell type. Here, we show that cell-type-specific alternative splicing is responsible for confining the phenotype of the A-to-G substitution in the 3' splice site of BBS8 exon 2A (IVS1-2A>G mutation) in the BBS8 gene to photoreceptor cells. The IVS1-2A>G mutation leads to missplicing of BBS8 exon 2A, producing a frameshift in the BBS8 reading frame and thus eliminating the protein specifically in photoreceptor cells. Cell types other than photoreceptors skip exon 2A from the mature BBS8 transcript, which renders them immune to the mutation. We also show that the splicing of Bbs8 exon 2A in photoreceptors is directed exclusively by redundant splicing enhancers located in the adjacent introns. These intronic sequences are sufficient for photoreceptor-cell-specific splicing of heterologous exons, including an exon with a randomized sequence.
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14
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Sharma S, Wongpalee SP, Vashisht A, Wohlschlegel JA, Black DL. Stem-loop 4 of U1 snRNA is essential for splicing and interacts with the U2 snRNP-specific SF3A1 protein during spliceosome assembly. Genes Dev 2015; 28:2518-31. [PMID: 25403181 PMCID: PMC4233244 DOI: 10.1101/gad.248625.114] [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] [Indexed: 11/25/2022]
Abstract
The pairing of 5′ and 3′ splice sites across an intron is a critical step in spliceosome formation and its regulation. Sharma et al. report a new interaction between stem–loop 4 (SL4) of the U1 snRNA, which recognizes the 5′ splice, and a component of the U2 snRNP complex, which assembles across the intron at the 3′ splice site. U1-SL4 interacts with the SF3A1 protein of the U2 snRNP, and this interaction occurs within prespliceosomal complexes assembled on the pre-mRNA. The pairing of 5′ and 3′ splice sites across an intron is a critical step in spliceosome formation and its regulation. Interactions that bring the two splice sites together during spliceosome assembly must occur with a high degree of specificity and fidelity to allow expression of functional mRNAs and make particular alternative splicing choices. Here, we report a new interaction between stem–loop 4 (SL4) of the U1 snRNA, which recognizes the 5′ splice site, and a component of the U2 small nuclear ribonucleoprotein particle (snRNP) complex, which assembles across the intron at the 3′ splice site. Using a U1 snRNP complementation assay, we found that SL4 is essential for splicing in vivo. The addition of free U1-SL4 to a splicing reaction in vitro inhibits splicing and blocks complex assembly prior to formation of the prespliceosomal A complex, indicating a requirement for a SL4 contact in spliceosome assembly. To characterize the interactions of this RNA structure, we used a combination of stable isotope labeling by amino acids in cell culture (SILAC), biotin/Neutravidin affinity pull-down, and mass spectrometry. We show that U1-SL4 interacts with the SF3A1 protein of the U2 snRNP. We found that this interaction between the U1 snRNA and SF3A1 occurs within prespliceosomal complexes assembled on the pre-mRNA. Thus, SL4 of the U1 snRNA is important for splicing, and its interaction with SF3A1 mediates contact between the 5′ and 3′ splice site complexes within the assembling spliceosome.
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Affiliation(s)
- Shalini Sharma
- Department of Basic Medical Sciences, University of Arizona, College of Medicine-Phoenix, Phoenix, Arizona 85004, USA; Department of Microbiology, Immunology, and Molecular Genetics
| | | | | | | | - Douglas L Black
- Department of Microbiology, Immunology, and Molecular Genetics, Howard Hughes Medical Institute, University of California at Los Angeles, Los Angeles, California 90095, USA
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15
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Rbfox3 controls the biogenesis of a subset of microRNAs. Nat Struct Mol Biol 2014; 21:901-10. [PMID: 25240799 PMCID: PMC4189996 DOI: 10.1038/nsmb.2892] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/23/2014] [Indexed: 12/21/2022]
Abstract
RNA-binding proteins (RBPs) regulate numerous aspects of gene expression; thus, identification of their endogenous targets is important for understanding their cellular functions. Here we identified transcriptome-wide targets of Rbfox3 in neuronally differentiated P19 cells and mouse brain by using photoactivatable ribonucleoside-enhanced cross-linking and immunoprecipitation (PAR-CLIP). Although Rbfox3 is known to regulate pre-mRNA splicing through binding the UGCAUG motif, PAR-CLIP analysis revealed diverse Rbfox3 targets including primary microRNAs (pri-miRNAs) that lack the UGCAUG motif. Induced expression and depletion of Rbfox3 led to changes in the expression levels of a subset of PAR-CLIP-detected miRNAs. In vitro analyses revealed that Rbfox3 functions as a positive and a negative regulator at the stage of pri-miRNA processing to precursor miRNA (pre-miRNA). Rbfox3 binds directly to pri-miRNAs and regulates the recruitment of the microprocessor complex to pri-miRNAs. Our study proposes a new function for Rbfox3 in miRNA biogenesis.
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16
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Kłossowicz M, Marek-Bukowiec K, Arbulo-Echevarria MM, Ścirka B, Majkowski M, Sikorski AF, Aguado E, Miazek A. Identification of functional, short-lived isoform of linker for activation of T cells (LAT). Genes Immun 2014; 15:449-56. [PMID: 25008862 DOI: 10.1038/gene.2014.35] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 05/04/2014] [Accepted: 05/23/2014] [Indexed: 12/13/2022]
Abstract
Linker for activation of T cells (LAT) is a transmembrane adaptor protein playing a key role in the development, activation and maintenance of peripheral homeostasis of T cells. In this study we identified a functional isoform of LAT. It originates from an intron 6 retention event generating an in-frame splice variant of LAT mRNA denoted as LATi6. Comparison of LATi6 expression in peripheral blood leukocytes of human and several other mammalian species revealed that it varied from being virtually absent in the mouse to being predominant in the cow. Analysis of LAT isoform frequency expressed from minigene splicing reporters carrying loss- or gain-of-function point mutations within intronic polyguanine sequences showed that these elements are critical for controlling the intron 6 removal. The protein product of LATi6 isoform (LATi6) ectopically expressed in LAT-deficient JCam 2.5 cell line localized correctly to subcellular compartments and supported T-cell receptor signaling but differed from the canonical LAT protein by displaying a shorter half-life and mediating an increased interleukin-2 secretion upon prolonged CD3/CD28 crosslinking. Altogether, our data suggest that the appearance of LATi6 isoform is an evolutionary innovation that may contribute to a more efficient proofreading control of effector T-cell response.
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Affiliation(s)
- M Kłossowicz
- Laboratory of Tumor Immunology, Department of Tumor Immunology, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
| | - K Marek-Bukowiec
- Laboratory of Tumor Immunology, Department of Tumor Immunology, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
| | - M M Arbulo-Echevarria
- Department of Biomedicine, Biotechnology and Public Health (Immunology), Core Research Facility for Health Sciences, University of Cadiz and Puerto Real University Hospital Research Unit, School of Medicine, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cadiz, Spain
| | - B Ścirka
- Laboratory of Tumor Immunology, Department of Tumor Immunology, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
| | - M Majkowski
- Laboratory of Cytobiochemistry, Biotechnology Faculty, University of Wrocław, Wroclaw, Poland
| | - A F Sikorski
- Laboratory of Cytobiochemistry, Biotechnology Faculty, University of Wrocław, Wroclaw, Poland
| | - E Aguado
- Department of Biomedicine, Biotechnology and Public Health (Immunology), Core Research Facility for Health Sciences, University of Cadiz and Puerto Real University Hospital Research Unit, School of Medicine, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cadiz, Spain
| | - A Miazek
- 1] Laboratory of Tumor Immunology, Department of Tumor Immunology, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland [2] Department of Biochemistry, Pharmacology and Toxicology, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland
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17
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Hall MP, Nagel RJ, Fagg WS, Shiue L, Cline MS, Perriman RJ, Donohue JP, Ares M. Quaking and PTB control overlapping splicing regulatory networks during muscle cell differentiation. RNA (NEW YORK, N.Y.) 2013; 19:627-38. [PMID: 23525800 PMCID: PMC3677278 DOI: 10.1261/rna.038422.113] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 02/20/2013] [Indexed: 05/26/2023]
Abstract
Alternative splicing contributes to muscle development, but a complete set of muscle-splicing factors and their combinatorial interactions are unknown. Previous work identified ACUAA ("STAR" motif) as an enriched intron sequence near muscle-specific alternative exons such as Capzb exon 9. Mass spectrometry of myoblast proteins selected by the Capzb exon 9 intron via RNA affinity chromatography identifies Quaking (QK), a protein known to regulate mRNA function through ACUAA motifs in 3' UTRs. We find that QK promotes inclusion of Capzb exon 9 in opposition to repression by polypyrimidine tract-binding protein (PTB). QK depletion alters inclusion of 406 cassette exons whose adjacent intron sequences are also enriched in ACUAA motifs. During differentiation of myoblasts to myotubes, QK levels increase two- to threefold, suggesting a mechanism for QK-responsive exon regulation. Combined analysis of the PTB- and QK-splicing regulatory networks during myogenesis suggests that 39% of regulated exons are under the control of one or both of these splicing factors. This work provides the first evidence that QK is a global regulator of splicing during muscle development in vertebrates and shows how overlapping splicing regulatory networks contribute to gene expression programs during differentiation.
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18
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The RNA-binding protein Rbfox2: an essential regulator of EMT-driven alternative splicing and a mediator of cellular invasion. Oncogene 2013; 33:1082-92. [PMID: 23435423 DOI: 10.1038/onc.2013.50] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 01/18/2013] [Accepted: 01/21/2013] [Indexed: 12/15/2022]
Abstract
The epithelial-mesenchymal transition (EMT), a prerequisite for cancer progression and metastasis formation, is regulated not only at the transcriptional but also at the post-transcriptional level, including at the level of alternative pre-mRNA splicing. Several recent studies have highlighted the involvement of splicing factors, including epithelial splicing regulatory proteins (Esrps) and RNA-binding Fox protein 2 (Rbfox2), in this process. Esrps regulate epithelial-specific splicing, and their expression is downregulated during EMT. By contrast, the role of Rbfox2 is controversial because Rbfox2 regulates epithelial as well as mesenchymal splicing events. Here, we have used several established cell culture models to investigate the functions of Rbfox2 during EMT. We demonstrate that induction of an EMT upregulates the expression of Rbfox2, which correlates with an increase in Rbfox2-regulated splicing events in the cortactin (Cttn), Pard3 and dynamin 2 (Dnm2) transcripts. At the same time, however, the epithelial-specific ability to splice the Enah, Slk and Tsc2 transcripts is either reduced or lost completely by Rbfox2, which might be due, in part, to downregulation of the expression of the Esrps cooperative factors. Depletion of Rbfox2 during EMT did not prevent the activation of transforming growth factor-β signaling, the upregulation of mesenchymal markers or changes in cell morphology toward a mesenchymal phenotype. In addition, this depletion did not influence cell migration. However, depletion of Rbfox2 in cells that have completed an EMT significantly reduced their invasive potential. Taken together, our results suggest that during an EMT, Rbfox2-regulated splicing shifts from epithelial-to mesenchymal-specific events, leading to a higher degree of tissue invasiveness.
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19
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Combinatorial mutagenesis of MBNL1 zinc fingers elucidates distinct classes of regulatory events. Mol Cell Biol 2012; 32:4155-67. [PMID: 22890842 DOI: 10.1128/mcb.00274-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The RNA binding protein and alternative splicing factor Muscleblind-like 1 (MBNL1) has been a topic of intense study due to its role in myotonic dystrophy (DM) pathogenesis. MBNL1 contains four zinc finger (ZF) RNA binding domains arranged in two pairs. Through combinatorial mutagenesis of the ZF domains, we demonstrate that the pairs of ZFs have differential affinity for RNA and subsequently differential splicing activities. We evaluated splicing and binding activity for six MBNL1-mediated splicing events and found that the splicing activity profiles for the ZF mutants vary among transcripts. Clustering analysis of splicing profiles revealed that two distinct classes of MBNL1 pre-mRNA substrates exist. For some of the RNA transcripts tested, binding and splicing activity of the ZF mutants correlated. However, for some transcripts it appears that MBNL1 exerts robust splicing activity in the absence of RNA binding. We demonstrate that functionally distinct classes of MBNL1-mediated splicing events exist as defined by requirements for ZF-RNA interactions.
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20
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Davis LK, Maltman N, Mosconi MW, Macmillan C, Schmitt L, Moore K, Francis SM, Jacob S, Sweeney JA, Cook EH. Rare inherited A2BP1 deletion in a proband with autism and developmental hemiparesis. Am J Med Genet A 2012; 158A:1654-61. [PMID: 22678932 DOI: 10.1002/ajmg.a.35396] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 03/03/2012] [Indexed: 12/15/2022]
Abstract
Ataxin 2 binding protein 1 (A2BP1 aka FOX1, RBFOX1) is an RNA binding protein responsible for regulation of pre-mRNA splicing events in a number of critical developmental genes expressed in muscle, heart and neuronal cells [Shibata et al. (2000); Mamm Genome 12:595-601; Jin et al. (2003); EMBO J 22:905-912; Underwood et al. (2005); Mol Cell Biol 25:10005-10016]. Rare copy number abnormalities of A2BP1 have been previously associated with cognitive impairment, attention deficit disorder and autism [Martin et al. (2007); Am J Med Gen Part B 144B:869-876; Elia et al. (2010); Mol Psychiatry 15:637-646.]. Using a 1M Illumina SNP microarray, we identified a 1.3 kb deletion in A2BP1, which was subsequently validated by quantitative PCR. Here we present an in depth case study of an individual with autism and mild developmental hemiparesis in whom the deletion was detected. This study provides further support for the possible role of rare copy number variants in A2BP1 in the development of autism and associated motor asymmetries.
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Affiliation(s)
- L K Davis
- Department of Psychiatry, University of Illinois, Chicago, Illinois 60637, USA.
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21
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Flanigan KM, Dunn DM, von Niederhausern A, Soltanzadeh P, Howard MT, Sampson JB, Swoboda KJ, Bromberg MB, Mendell JR, Taylor LE, Anderson CB, Pestronk A, Florence JM, Connolly AM, Mathews KD, Wong B, Finkel RS, Bonnemann CG, Day JW, McDonald C, Weiss RB. Nonsense mutation-associated Becker muscular dystrophy: interplay between exon definition and splicing regulatory elements within the DMD gene. Hum Mutat 2012; 32:299-308. [PMID: 21972111 DOI: 10.1002/humu.21426] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Nonsense mutations are usually predicted to function as null alleles due to premature termination of protein translation. However, nonsense mutations in the DMD gene, encoding the dystrophin protein, have been associated with both the severe Duchenne Muscular Dystrophy (DMD) and milder Becker Muscular Dystrophy (BMD) phenotypes. In a large survey, we identified 243 unique nonsense mutations in the DMD gene, and for 210 of these we could establish definitive phenotypes. We analyzed the reading frame predicted by exons flanking those in which nonsense mutations were found, and present evidence that nonsense mutations resulting in BMD likely do so by inducing exon skipping, confirming that exonic point mutations affecting exon definition have played a significant role in determining phenotype. We present a new model based on the combination of exon definition and intronic splicing regulatory elements for the selective association of BMD nonsense mutations with a subset of DMD exons prone to mutation-induced exon skipping.
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Affiliation(s)
- Kevin M Flanigan
- Center for Gene Therapy, Nationwide Children's Hospital, Columbus, Ohio, USA.
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22
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Fisette JF, Montagna DR, Mihailescu MR, Wolfe MS. A G-rich element forms a G-quadruplex and regulates BACE1 mRNA alternative splicing. J Neurochem 2012; 121:763-73. [PMID: 22303960 DOI: 10.1111/j.1471-4159.2012.07680.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
β-Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is the transmembrane aspartyl protease that catalyzes the first cleavage step in the proteolysis of the APP to the amyloid β-protein (Aβ), a process involved in the pathogenesis of Alzheimer disease. BACE1 pre-mRNA undergoes complex alternative splicing, the regulation of which is not well understood. We identified a G-rich sequence within exon 3 of BACE1 involved in controlling splice site selection. Mutation of the G-rich sequence decreased use of the normal 5' splice site of exon 3, which leads to full-length and proteolytically active BACE1, and increased use of an alternative splice site, which leads to a shorter, essentially inactive isoform. Nuclease protection assays, nuclear magnetic resonance, and circular dichroism spectroscopy revealed that this sequence folds into a G-quadruplex structure. Several proteins were identified as capable of binding to the G-rich sequence, and one of these, heterogeneous nuclear ribonucleoprotein H, was found to regulate BACE1 exon 3 alternative splicing and in a manner dependent on the G-rich sequence. Knockdown of heterogeneous nuclear ribonucleoprotein H led to a decrease in the full-length BACE1 mRNA isoform as well as a decrease in Aβ production from APP, suggesting new possibilities for therapeutic approaches to Alzheimer's disease.
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Affiliation(s)
- Jean-François Fisette
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
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23
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Preussner M, Schreiner S, Hung LH, Porstner M, Jäck HM, Benes V, Rätsch G, Bindereif A. HnRNP L and L-like cooperate in multiple-exon regulation of CD45 alternative splicing. Nucleic Acids Res 2012; 40:5666-78. [PMID: 22402488 PMCID: PMC3384337 DOI: 10.1093/nar/gks221] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
CD45 encodes a trans-membrane protein-tyrosine phosphatase expressed in diverse cells of the immune system. By combinatorial use of three variable exons 4–6, isoforms are generated that differ in their extracellular domain, thereby modulating phosphatase activity and immune response. Alternative splicing of these CD45 exons involves two heterogeneous ribonucleoproteins, hnRNP L and its cell-type specific paralog hnRNP L-like (LL). To address the complex combinatorial splicing of exons 4–6, we investigated hnRNP L/LL protein expression in human B-cells in relation to CD45 splicing patterns, applying RNA-Seq. In addition, mutational and RNA-binding analyses were carried out in HeLa cells. We conclude that hnRNP LL functions as the major CD45 splicing repressor, with two CA elements in exon 6 as its primary target. In exon 4, one element is targeted by both hnRNP L and LL. In contrast, exon 5 was never repressed on its own and only co-regulated with exons 4 and 6. Stable L/LL interaction requires CD45 RNA, specifically exons 4 and 6. We propose a novel model of combinatorial alternative splicing: HnRNP L and LL cooperate on the CD45 pre-mRNA, bridging exons 4 and 6 and looping out exon 5, thereby achieving full repression of the three variable exons.
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Affiliation(s)
- Marco Preussner
- Institute of Biochemistry, Justus Liebig University of Giessen, D-35392 Giessen, Germany
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24
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Gehman LT, Meera P, Stoilov P, Shiue L, O'Brien JE, Meisler MH, Ares M, Otis TS, Black DL. The splicing regulator Rbfox2 is required for both cerebellar development and mature motor function. Genes Dev 2012; 26:445-60. [PMID: 22357600 DOI: 10.1101/gad.182477.111] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Rbfox proteins (Rbfox1, Rbfox2, and Rbfox3) regulate the alternative splicing of many important neuronal transcripts and have been implicated in a variety of neurological disorders. However, their roles in brain development and function are not well understood, in part due to redundancy in their activities. Here we show that, unlike Rbfox1 deletion, the CNS-specific deletion of Rbfox2 disrupts cerebellar development. Genome-wide analysis of Rbfox2(-/-) brain RNA identifies numerous splicing changes altering proteins important both for brain development and mature neuronal function. To separate developmental defects from alterations in the physiology of mature cells, Rbfox1 and Rbfox2 were deleted from mature Purkinje cells, resulting in highly irregular firing. Notably, the Scn8a mRNA encoding the Na(v)1.6 sodium channel, a key mediator of Purkinje cell pacemaking, is improperly spliced in RbFox2 and Rbfox1 mutant brains, leading to highly reduced protein expression. Thus, Rbfox2 protein controls a post-transcriptional program required for proper brain development. Rbfox2 is subsequently required with Rbfox1 to maintain mature neuronal physiology, specifically Purkinje cell pacemaking, through their shared control of sodium channel transcript splicing.
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Affiliation(s)
- Lauren T Gehman
- Molecular Biology Institute, University of California at Los Angeles, CA 90095, USA
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25
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Abstract
The erythroid differentiation-specific splicing switch of protein 4.1R exon 16, which encodes a spectrin/actin-binding peptide critical for erythrocyte membrane stability, is modulated by the differentiation-induced splicing factor RBFOX2. We have now characterized the mechanism by which RBFOX2 regulates exon 16 splicing through the downstream intronic element UGCAUG. Exon 16 possesses a weak 5' splice site (GAG/GTTTGT), which when strengthened to a consensus sequence (GAG/GTAAGT) leads to near-total exon 16 inclusion. Impaired RBFOX2 binding reduces exon 16 inclusion in the context of the native weak 5' splice site, but not the engineered strong 5' splice site, implying that RBFOX2 achieves its effect by promoting utilization of the weak 5' splice site. We further demonstrate that RBFOX2 increases U1 snRNP recruitment to the weak 5' splice site through direct interaction between its C-terminal domain (CTD) and the zinc finger region of U1C and that the CTD is required for the effect of RBFOX2 on exon 16 splicing. Our data suggest a novel mechanism for exon 16 5' splice site activation in which the binding of RBFOX2 to downstream intronic splicing enhancers stabilizes the pre-mRNA-U1 snRNP complex through interactions with U1C.
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26
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O'Brien JE, Drews VL, Jones JM, Dugas JC, Barres BA, Meisler MH. Rbfox proteins regulate alternative splicing of neuronal sodium channel SCN8A. Mol Cell Neurosci 2011; 49:120-6. [PMID: 22044765 DOI: 10.1016/j.mcn.2011.10.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 10/10/2011] [Accepted: 10/14/2011] [Indexed: 12/17/2022] Open
Abstract
The SCN8A gene encodes the voltage-gated sodium channel Na(v)1.6, a major channel in neurons of the CNS and PNS. SCN8A contains two alternative exons,18N and 18A, that exhibit tissue specific splicing. In brain, the major SCN8A transcript contains exon 18A and encodes the full-length sodium channel. In other tissues, the major transcript contains exon 18N and encodes a truncated protein, due to the presence of an in-frame stop codon. Selection of exon 18A is therefore essential for generation of a functional channel protein, but the proteins involved in this selection have not been identified. Using a 2.6 kb Scn8a minigene containing exons 18N and 18A, we demonstrate that co-transfection with Fox-1 or Fox-2 initiates inclusion of exon 18A. This effect is dependent on the consensus Fox binding site located 28 bp downstream of exon 18A. We examined the alternative splicing of human SCN8A and found that the postnatal switch to exon 18A is completed later than 10 months of age. In purified cell populations, transcripts containing exon 18A predominate in neurons but are not present in oligodendrocytes or astrocytes. Transcripts containing exon 18N appear to be degraded by nonsense-mediated decay in HEK cells. Our data indicate that RBFOX proteins contribute to the cell-specific expression of Na(v)1.6 channels in mature neurons.
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Affiliation(s)
- Janelle E O'Brien
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
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27
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Sharma S, Liao W, Zhou X, Wong DTW, Lichtenstein A. Exon 11 skipping of E-cadherin RNA downregulates its expression in head and neck cancer cells. Mol Cancer Ther 2011; 10:1751-9. [PMID: 21764905 DOI: 10.1158/1535-7163.mct-11-0248] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
E-cadherin is an important tumor suppressor gene whose expression is lost when cells acquire a metastatic phenotype. We analyzed the role of E-cadherin missplicing as a mechanism of its downregulation by analyzing a misspliced E-cadherin transcript that lacks exon 11 of this gene. This results in a frameshift and a premature termination codon that targets this transcript for degradation. Tumor tissues, including breast (20%, n = 9), prostate (30%, n = 9) and head and neck (75%, n = 8) cancer, express the exon 11-skipped transcripts (vs. nonmalignant controls) and its levels inversely correlate with E-cadherin expression. This is a novel mechanism of E-cadherin downregulation by missplicing in tumor cells, which is observed in highly prevalent human tumors. In the head and neck cancer model, nontumorigenic keratinocytes express exon 11-skipped splice product two- to sixfold lower than the head and neck tumor cell lines. Mechanistic studies reveal that SFRS2 (SC35), a splicing factor, as one of the regulators that increases missplicing and downregulates E-cadherin expression. Furthermore, this splicing factor was found to be overexpressed in 5 of 7 head and neck cell lines and primary head and neck tumors. Also, methylation of E-cadherin gene acts as a regulator of this aberrant splicing process. In 2 head and neck cell lines, wild-type transcript expression increased 16- to 25-folds, whereas the percentage of exon 11-skipped transcripts in both the cell lines decreased five- to 30-folds when cells were treated with a hypomethylating agent, azacytidine. Our findings reveal that promoter methylation and an upregulated splicing factor (SFRS2) are involved in the E-cadherin missplicing in tumors.
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Affiliation(s)
- Sanjai Sharma
- Division of Hematology Oncology, UCLA West Los Angeles VA Medical Center, 11301 Wilshire Blvd, Bldg 304, Rm E1-115, Los Angeles, CA 90073, USA.
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28
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Gehman LT, Stoilov P, Maguire J, Damianov A, Lin CH, Shiue L, Ares M, Mody I, Black DL. The splicing regulator Rbfox1 (A2BP1) controls neuronal excitation in the mammalian brain. Nat Genet 2011; 43:706-11. [PMID: 21623373 PMCID: PMC3125461 DOI: 10.1038/ng.841] [Citation(s) in RCA: 258] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 05/02/2011] [Indexed: 11/09/2022]
Abstract
The Rbfox family of RNA binding proteins regulates alternative splicing of many important neuronal transcripts, but its role in neuronal physiology is not clear. We show here that central nervous system-specific deletion of the gene encoding Rbfox1 results in heightened susceptibility to spontaneous and kainic acid-induced seizures. Electrophysiological recording revealed a corresponding increase in neuronal excitability in the dentate gyrus of the knockout mice. Whole-transcriptome analyses identified multiple splicing changes in the Rbfox1(-/-) brain with few changes in overall transcript abundance. These splicing changes alter proteins that mediate synaptic transmission and membrane excitation. Thus, Rbfox1 directs a genetic program required in the prevention of neuronal hyperexcitation and seizures. The Rbfox1 knockout mice provide a new model to study the post-transcriptional regulation of synaptic function.
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Affiliation(s)
- Lauren T Gehman
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, USA
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Tang ZZ, Sharma S, Zheng S, Chawla G, Nikolic J, Black DL. Regulation of the mutually exclusive exons 8a and 8 in the CaV1.2 calcium channel transcript by polypyrimidine tract-binding protein. J Biol Chem 2011; 286:10007-16. [PMID: 21282112 PMCID: PMC3060452 DOI: 10.1074/jbc.m110.208116] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
CaV1.2 calcium channels play roles in diverse cellular processes such as gene regulation, muscle contraction, and membrane excitation and are diversified in their activity through extensive alternative splicing of the CaV1.2 mRNA. The mutually exclusive exons 8a and 8 encode alternate forms of transmembrane segment 6 (IS6) in channel domain 1. The human genetic disorder Timothy syndrome is caused by mutations in either of these two CaV1.2 exons, resulting in disrupted Ca2+ homeostasis and severe pleiotropic disease phenotypes. The tissue-specific pattern of exon 8/8a splicing leads to differences in symptoms between patients with exon 8 or 8a mutations. Elucidating the mechanisms controlling the exon 8/8a splicing choice will be important in understanding the spectrum of defects associated with the disease. We found that the polypyrimidine tract-binding protein (PTB) mediates a switch from exon 8 to 8a splicing. PTB and its neuronal homolog, nPTB, are widely studied splicing regulators controlling large sets of alternative exons. During neuronal development, PTB expression is down-regulated with a concurrent increase in nPTB expression. Exon 8a is largely repressed in embryonic mouse brain but is progressively induced during neuronal differentiation as PTB is depleted. This splicing repression is mediated by the direct binding of PTB to sequence elements upstream of exon 8a. The nPTB protein is a weaker repressor of exon 8a, resulting in a shift in exon choice when nPTB replaces PTB in cells. These results provide mechanistic understanding of how these two exons, important for human disease, are controlled.
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Affiliation(s)
- Zhen Zhi Tang
- Howard Hughes Medical Institute, UCLA, Los Angeles, California 90095, USA
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30
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Xiao X, Lee JH. Systems analysis of alternative splicing and its regulation. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2011; 2:550-565. [PMID: 20836047 DOI: 10.1002/wsbm.84] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Alternative splicing (AS) has emerged as a key mechanism that accounts for gene expression diversity in metazoan organisms. Splicing is tightly regulated by a repertoire of RNA and protein factors and RNA sequence elements that function in a cooperative manner. Systems-level experimental and computational approaches have been instrumental in establishing comprehensive profiles of transcript variants generated by AS. In addition, systems biology approaches are starting to define how combinatorial splicing regulation shapes the complex splicing phenotypes observed in different tissue types and developmental stages and under different conditions. Here, we review recent progress in these areas.
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Affiliation(s)
- Xinshu Xiao
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA.,Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Jae-Hyung Lee
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA.,Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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31
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Kim KK, Kim YC, Adelstein RS, Kawamoto S. Fox-3 and PSF interact to activate neural cell-specific alternative splicing. Nucleic Acids Res 2010; 39:3064-78. [PMID: 21177649 PMCID: PMC3082911 DOI: 10.1093/nar/gkq1221] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Fox-1 family (Fox) proteins, which consist of Fox-1 (A2BP1), Fox-2 (Rbm9) and Fox-3 (NeuN) in mammals, bind to the RNA element UGCAUG and regulate alternative pre-mRNA splicing. However the mechanisms for Fox-regulated splicing are largely unknown. We analyzed the expression pattern of the three Fox proteins as well as neural cell-specific alternative splicing of a cassette exon N30 of nonmuscle myosin heavy chain (NMHC) II-B in the mouse central nervous system. Histological and biochemical analyses following fluorescence-activated cell sorting demonstrate a positive correlation of N30 inclusion and Fox-3 expression. Further, we identified polypyrimidine tract binding protein-associated splicing factor (PSF) as an interacting protein with Fox-3 by affinity-chromatography. In cultured cells, enhancement of N30 inclusion by Fox-3 depends on the presence of PSF. PSF enhances N30 inclusion in a UGCAUG-dependent manner, although it does not bind directly to this element. Fox-3 is recruited to the UGCAUG element downstream of N30 in the endogenous NMHC II-B transcript in a PSF-dependent manner. This study is the first to identify PSF as a coactivator of Fox proteins and provides evidence that the Fox-3 and PSF interaction is an integral part of the mechanism by which Fox proteins regulate activation of alternative exons via a downstream intronic enhancer.
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Affiliation(s)
- Kee K Kim
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD 20892, USA
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32
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SR proteins induce alternative exon skipping through their activities on the flanking constitutive exons. Mol Cell Biol 2010; 31:793-802. [PMID: 21135118 DOI: 10.1128/mcb.01117-10] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SR proteins are well known to promote exon inclusion in regulated splicing through exonic splicing enhancers. SR proteins have also been reported to cause exon skipping, but little is known about the mechanism. We previously characterized SRSF1 (SF2/ASF)-dependent exon skipping of the CaMKIIδ gene during heart remodeling. By using mouse embryo fibroblasts derived from conditional SR protein knockout mice, we now show that SR protein-induced exon skipping depends on their prevalent actions on a flanking constitutive exon and requires collaboration of more than one SR protein. These findings, coupled with other established rules for SR proteins, provide a theoretical framework to understand the complex effect of SR protein-regulated splicing in mammalian cells. We further demonstrate that heart-specific CaMKIIδ splicing can be reconstituted in fibroblasts by downregulating SR proteins and upregulating a RBFOX protein and that SR protein overexpression impairs regulated CaMKIIδ splicing and neuronal differentiation in P19 cells, illustrating that SR protein-dependent exon skipping may constitute a key strategy for synergism with other splicing regulators in establishing tissue-specific alternative splicing critical for cell differentiation programs.
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Glubb DM, Innocenti F. Mechanisms of genetic regulation in gene expression: examples from drug metabolizing enzymes and transporters. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2010; 3:299-313. [PMID: 20865777 DOI: 10.1002/wsbm.125] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Interindividual variability in the response to drug therapy is due, in part, to genetic mechanisms which influence the expression of genes involved with drug metabolism and transport. Genetic elements and processes such as DNA methylation, histone deacetylation, transcription factors, DNA sequence variants, and microRNAs (miRNAs) can impact at either the transcriptional or translational levels to modulate gene expression. Identification of such genetic regulators has greatly advanced in the last decade. Genome-wide analyses, using different types of approaches and methodologies, have uncovered many potential regulators of the expression of drug metabolizing enzymes and transporters. However, confirming the function of these putative regulators is necessary and requires further work in the laboratory, using techniques which are still evolving. It also still remains to be seen whether these findings have clinical implications for drug therapy but the realization of personalized medicine is a possible consequence of this research.
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Affiliation(s)
- Dylan M Glubb
- Department of Medicine, University of Chicago, Chicago, IL, USA
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Seth P, Yeowell HN. Fox-2 protein regulates the alternative splicing of scleroderma-associated lysyl hydroxylase 2 messenger RNA. ACTA ACUST UNITED AC 2010; 62:1167-75. [PMID: 20131247 DOI: 10.1002/art.27315] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Scleroderma (systemic sclerosis [SSc]) is a complex connective tissue disorder characterized by hardening and thickening of the skin. One hallmark of scleroderma is excessive accumulation of collagen accompanied by increased levels of pyridinoline collagen crosslinks derived from hydroxylysine residues in the collagen telopeptide domains. Lysyl hydroxylase 2 (LH2), an important alternatively spliced enzyme in collagen biosynthesis, acts as a collagen telopeptide hydroxylase. Changes in the pattern of LH2 alternative splicing, favoring increased inclusion of the alternatively spliced LH2 exon 13A, thereby increasing the levels of the long transcript of LH2 (LH2[long]), are linked to scleroderma disease. This study was undertaken to examine the role played by RNA binding protein Fox-2 in regulating exon 13A inclusion, which leads to the generation of scleroderma-associated LH2(long) messenger RNA (mRNA). METHODS Phylogenetic sequence analysis of introns flanking exon 13A was performed. A tetracycline-inducible system in T-Rex 293 cells was used to induce Fox-2 protein, and endogenous LH2(long) mRNA was determined by reverse transcriptase-polymerase chain reaction. An LH2 minigene was designed, validated, and used in Fox-2 overexpression and mutagenesis experiments. Knockdown of Fox-2 was performed in mouse embryonic fibroblasts and in fibroblasts from SSc patients. RESULTS Overexpression of Fox-2 enhanced the inclusion of exon 13A and increased the generation of LH2(long) mRNA, whereas knockdown of Fox-2 decreased LH2(long) transcripts. Mutational analysis of an LH2 minigene demonstrated that 2 of the 4 Fox binding motifs flanking LH2 exon 13A are required for inclusion of exon 13A. In early passage fibroblasts derived from patients with scleroderma, the knockdown of Fox-2 protein significantly decreased the endogenous levels of LH2(long) mRNA. CONCLUSION Our findings indicate that Fox-2 plays an integral role in the regulation of LH2 splicing. Knockdown of Fox-2 and other methods to decrease the levels of fibrosis-associated LH2(long) mRNA in primary scleroderma cells may suggest a novel approach to strategies directed against scleroderma.
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Affiliation(s)
- Puneet Seth
- Duke University Medical Center, Durham, North Carolina 27710, USA
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35
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RNA looping by PTB: Evidence using FRET and NMR spectroscopy for a role in splicing repression. Proc Natl Acad Sci U S A 2010; 107:4105-10. [PMID: 20160105 DOI: 10.1073/pnas.0907072107] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Alternative splicing plays an important role in generating proteome diversity. The polypyrimidine tract-binding protein (PTB) is a key alternative splicing factor involved in exon repression. It has been proposed that PTB acts by looping out exons flanked by pyrimidine tracts. We present fluorescence, NMR, and in vivo splicing data in support of a role of PTB in inducing RNA loops. We show that the RNA recognition motifs (RRMs) 3 and 4 of PTB can bind two distant pyrimidine tracts and bring their 5' and 3' ends in close proximity, thus looping the RNA. Efficient looping requires an intervening sequence of 15 nucleotides or longer between the pyrimidine tracts. RRM3 and RRM4 bind the 5' and the 3' pyrimidine tracts, respectively, in a specific directionality and work synergistically for efficient splicing repression in vivo.
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Damianov A, Black DL. Autoregulation of Fox protein expression to produce dominant negative splicing factors. RNA (NEW YORK, N.Y.) 2010; 16:405-16. [PMID: 20042473 PMCID: PMC2811669 DOI: 10.1261/rna.1838210] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 10/19/2009] [Indexed: 05/23/2023]
Abstract
The Fox proteins are a family of regulators that control the alternative splicing of many exons in neurons, muscle, and other tissues. Each of the three mammalian paralogs, Fox-1 (A2BP1), Fox-2 (RBM9), and Fox-3 (HRNBP3), produces proteins with a single RNA-binding domain (RRM) flanked by N- and C-terminal domains that are highly diversified through the use of alternative promoters and alternative splicing patterns. These genes also express protein isoforms lacking the second half of the RRM (FoxDeltaRRM), due to the skipping of a highly conserved 93-nt exon. Fox binding elements overlap the splice sites of these exons in Fox-1 and Fox-2, and the Fox proteins themselves inhibit exon inclusion. Unlike other cases of splicing autoregulation by RNA-binding proteins, skipping the RRM exon creates an in-frame deletion in the mRNA to produce a stable protein. These FoxDeltaRRM isoforms expressed from cDNA exhibit highly reduced binding to RNA in vivo. However, we show that they can act as repressors of Fox-dependent splicing, presumably by competing with full-length Fox isoforms for interaction with other splicing factors. Interestingly, the Drosophila Fox homolog contains a nearly identical exon in its RRM domain that also has flanking Fox-binding sites. Thus, rather than autoregulation of splicing controlling the abundance of the regulator, the Fox proteins use a highly conserved mechanism of splicing autoregulation to control production of a dominant negative isoform.
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Affiliation(s)
- Andrey Damianov
- Howard Hughes Medical Institute, University of California at Los Angeles, Los Angeles, California 90095, USA
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37
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Russo A, Siciliano G, Catillo M, Giangrande C, Amoresano A, Pucci P, Pietropaolo C, Russo G. hnRNP H1 and intronic G runs in the splicing control of the human rpL3 gene. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1799:419-28. [PMID: 20100605 DOI: 10.1016/j.bbagrm.2010.01.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 01/15/2010] [Accepted: 01/19/2010] [Indexed: 11/29/2022]
Abstract
By generating mRNA containing a premature termination codon (PTC), alternative splicing (AS) can quantitatively regulate the expression of genes that are degraded by nonsense-mediated mRNA decay (NMD). We previously demonstrated that AS-induced retention of part of intron 3 of rpL3 pre-mRNA produces an mRNA isoform that contains a PTC and is targeted for decay by NMD. We also demonstrated that overexpression of rpL3 downregulates canonical splicing and upregulates the alternative splicing of its pre-mRNA. We are currently investigating the molecular mechanism underlying rpL3 autoregulation. Here we report that the heterogeneous nuclear ribonucleoprotein (hnRNP) H1 is a transacting factor able to interact in vitro and in vivo with rpL3 and with intron 3 of the rpL3 gene. We investigated the role played by hnRNP H1 in the regulation of splicing of rpL3 pre-mRNA by manipulating its expression level. Depletion of hnRNP H1 reduced the level of the PTC-containing mRNA isoform, whereas its overexpression favored the selection of the cryptic 3' splice site of intron 3. We also identified and characterized the cis-acting regulatory elements involved in hnRNP H1-mediated regulation of splicing. RNA electromobility shift assay demonstrated that hnRNP H1 specifically recognizes and binds directly to the intron 3 region that contains seven copies of G-rich elements. Site-directed mutagenesis analysis and in vivo studies showed that the G3 and G6 elements are required for hnRNP H1-mediated regulation of rpL3 pre-mRNA splicing. We propose a working model in which rpL3 recruits hnRNP H1 and, through cooperation with other splicing factors, promotes selection of the alternative splice site.
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Affiliation(s)
- Annapina Russo
- Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Napoli 80131, Italy
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38
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Kuroyanagi H. Fox-1 family of RNA-binding proteins. Cell Mol Life Sci 2009; 66:3895-907. [PMID: 19688295 PMCID: PMC2777236 DOI: 10.1007/s00018-009-0120-5] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 07/14/2009] [Accepted: 07/24/2009] [Indexed: 01/04/2023]
Abstract
The Fox-1 family of RNA-binding proteins are evolutionarily conserved regulators of tissue-specific alternative splicing in metazoans. The Fox-1 family specifically recognizes the (U)GCAUG stretch in regulated exons or in flanking introns, and either promotes or represses target exons. Recent unbiased bioinformatics analyses of alternatively spliced exons and comparison of various vertebrate genomes identified the (U)GCAUG stretch as a highly conserved and widely distributed element enriched in intronic regions surrounding exons with altered inclusion in muscle, heart, and brain, consistent with specific expression of Fox-1 and Fox-2 in these tissues. Global identification of Fox-2 target RNAs in living cells revealed that many of the Fox-2 target genes themselves encode splicing regulators. Further systematic elucidation of target genes of the Fox-1 family and other splicing regulators in various tissues will lead to a comprehensive understanding of splicing regulatory networks.
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Affiliation(s)
- Hidehito Kuroyanagi
- Laboratory of Gene Expression, Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.
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39
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Lee JA, Tang ZZ, Black DL. An inducible change in Fox-1/A2BP1 splicing modulates the alternative splicing of downstream neuronal target exons. Genes Dev 2009; 23:2284-93. [PMID: 19762510 DOI: 10.1101/gad.1837009] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Neuronal depolarization and CaM kinase IV signaling alter the splicing of multiple exons in transcripts for ion channels, neurotransmitter receptors, and other synaptic proteins. These splicing changes are mediated in part by special CaM kinase-responsive RNA elements, within or adjacent to exons that are repressed in the initial phase of chronic depolarization. The splicing of many neuronal transcripts is also regulated by members of the Fox (Feminizing gene on X) protein family, and these Fox targets are also often proteins affecting synaptic activity. We show that Fox-1/Ataxin 2-Binding Protein 1 (A2BP1), a protein implicated in a variety of neurological diseases, can counteract the effects of chronic depolarization on splicing. We find that exon 19 of Fox-1 is itself repressed by depolarization. Fox-1 transcripts missing exon 19 encode a nuclear isoform of Fox-1 that progressively replaces the cytoplasmic Fox-1 isoform as cells are maintained depolarizing media. The resulting increase in nuclear Fox-1 leads to the reactivation of many Fox-1 target exons, including exon 5 of the NMDA receptor 1, that were initially repressed by the high-KCl medium. These results reveal a novel mechanism for the slow modulation of splicing as cells adapt to chronic stimuli: The subcellular localization of a splicing regulator is controlled through its own alternative splicing.
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Affiliation(s)
- Ji-Ann Lee
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
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40
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The CUGBP2 splicing factor regulates an ensemble of branchpoints from perimeter binding sites with implications for autoregulation. PLoS Genet 2009; 5:e1000595. [PMID: 19680430 PMCID: PMC2715136 DOI: 10.1371/journal.pgen.1000595] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 07/13/2009] [Indexed: 12/30/2022] Open
Abstract
Alternative pre-mRNA splicing adjusts the transcriptional output of the genome by generating related mRNAs from a single primary transcript, thereby expanding protein diversity. A fundamental unanswered question is how splicing factors achieve specificity in the selection of target substrates despite the recognition of information-poor sequence motifs. The CUGBP2 splicing regulator plays a key role in the brain region-specific silencing of the NI exon of the NMDA R1 receptor. However, the sequence motifs utilized by this factor for specific target exon selection and its role in splicing silencing are not understood. Here, we use chemical modification footprinting to map the contact sites of CUGBP2 to GU-rich motifs closely positioned at the boundaries of the branch sites of the NI exon, and we demonstrate a mechanistic role for this specific arrangement of motifs for the regulation of branchpoint formation. General support for a branch site-perimeter–binding model is indicated by the identification of a group of novel target exons with a similar configuration of motifs that are silenced by CUGBP2. These results reveal an autoregulatory role for CUGBP2 as indicated by its direct interaction with functionally significant RNA motifs surrounding the branch sites upstream of exon 6 of the CUGBP2 transcript itself. The perimeter-binding model explains how CUGBP2 can effectively embrace the branch site region to achieve the specificity needed for the selection of exon targets and the fine-tuning of alternative splicing patterns. Alternative splicing is a precisely controlled process that determines whether an exon will be included or skipped in the mature mRNA transcript. Factors that control alternative splicing bind to RNA sequence motifs in the exon or flanking introns and guide tissue and developmental specific splicing events. CUGBP2 is a dual functional regulator of alternative splicing that can cause inclusion or skipping of a target exon, depending on the context of its binding motifs. Previously, the mechanisms of regulation by this protein and the positional significance of its target motifs have not been characterized. In this study, the authors dissected the mechanism of exon skipping by CUGBP2 and demonstrate that a specific configuration of motifs at the perimeters of a functional reference point are intimately involved in this event. Furthermore, this mechanism of regulation is shown to have general significance because novel CUGBP2 target exons contain a similar arrangement of motifs. The most interesting of this group is an exon within the CUGBP2 transcript itself. This study underscores the importance of a functional reference point in the specificity of regulation by an alternative splicing factor and reveals a novel autoregulatory role for CUGBP2.
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Developmental control of CaV1.2 L-type calcium channel splicing by Fox proteins. Mol Cell Biol 2009; 29:4757-65. [PMID: 19564422 DOI: 10.1128/mcb.00608-09] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CaV1.2 voltage-gated calcium channels play critical roles in the control of membrane excitability, gene expression, and muscle contraction. These channels show diverse functional properties generated by alternative splicing at multiple sites within the CaV1.2 pre-mRNA. The molecular mechanisms controlling this splicing are not understood. We find that two exons in the CaV1.2 channel are controlled in part by members of the Fox family of splicing regulators. Exons 9* and 33 confer distinct electrophysiological properties on the channel and show opposite patterns of regulation during cortical development, with exon 9* progressively decreasing its inclusion in the CaV1.2 mRNA over time and exon 33 progressively increasing. Both exons contain Fox protein binding elements within their adjacent introns, and Fox protein expression is induced in cortical neurons in parallel with the changes in CaV1.2 splicing. We show that knocking down expression of Fox proteins in tissue culture cells has opposite effects on exons 9* and 33. The loss of Fox protein increases exon 9* splicing and decreases exon 33, as predicted by the positions of the Fox binding elements and by the pattern of splicing in development. Conversely, overexpression of Fox1 and Fox2 proteins represses exon 9* and enhances exon 33 splicing in the endogenous CaV1.2 mRNA. These effects of Fox proteins on exons 9* and 33 can be recapitulated in transfected minigene reporters. Both the repressive and the enhancing effects of Fox proteins are dependent on the Fox binding elements within and adjacent to the target exons, indicating that the Fox proteins are directly regulating both exons. These results demonstrate that the Fox protein family is playing a key role in tuning the properties of CaV1.2 calcium channels during neuronal development.
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42
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Li H, Liu G, Yu J, Cao W, Lobo VG, Xie J. In vivo selection of kinase-responsive RNA elements controlling alternative splicing. J Biol Chem 2009; 284:16191-16201. [PMID: 19386606 DOI: 10.1074/jbc.m900393200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Alternative pre-mRNA splicing is often controlled by cell signals, for example, those activating the cAMP-dependent protein kinase (PKA) or the Ca2+/calmodulin-dependent protein kinase IV (CaMKIV). We have shown that CaMKIV regulates alternative splicing through short CA repeats and hnRNP L. Here we use a splicing reporter that shows PKA/CaMKIV promotion of exon inclusion to select from exons containing random 13-nt sequences for RNA elements responsive to the kinases in cultured cells. This selection not only identified both PKA- and CaMKIV-responsive elements that are similar to the CaMKIV-responsive RNA element 1 (CaRRE1) or CA repeats, but also A-rich elements not previously known to respond to these kinases. Consistently, hnRNP L is identified as a factor binding the CA-rich elements. Analyses of the motifs in the highly responsive elements indicate that they are indeed critical for the kinase effect and are enriched in alternative exons. Interestingly, a CAAAAAA motif is sufficient for the PKA/CaMKIV-regulated splicing of the exon 16 of the CaMK kinase beta1 (CaMKK2) transcripts, implying a role of this motif in signaling cross-talk or feedback regulation between these kinases through alternative splicing. Therefore, these experiments identified a group of RNA elements responsive to PKA and CaMKIV from in vivo selection. This also provides an approach for selecting RNA elements similarly responsive to other cell signals controlling alternative splicing.
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Affiliation(s)
- Hongzhao Li
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Guodong Liu
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Jiankun Yu
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Wenguang Cao
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Vincent G Lobo
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Jiuyong Xie
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada.
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43
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Abstract
We recently characterized human hnRNP L as a global regulator of alternative splicing, binding to CA-repeat and CA-rich elements. Here we report that hnRNP L autoregulates its own expression on the level of alternative splicing. Intron 6 of the human hnRNP L gene contains a short exon that, if used, introduces a premature termination codon, resulting in nonsense-mediated decay (NMD). This "poison exon" is preceded by a highly conserved CA-rich cluster extending over 800 nucleotides that binds hnRNP L and functions as an unusually extended, intronic enhancer, promoting inclusion of the poison exon. As a result, excess hnRNP L activates NMD of its own mRNA, thereby creating a negative autoregulatory feedback loop and contributing to homeostasis of hnRNP L levels. We present experimental evidence for this mechanism, based on NMD inactivation, hnRNP L binding assays, and hnRNP L-dependent alternative splicing of heterologous constructs. In addition, we demonstrate that hnRNP L cross-regulates inclusion of an analogous poison exon in the hnRNP L-like pre-mRNA, which explains the reciprocal expression of the two closely related hnRNP L proteins.
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44
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Nicholls CD, Beattie TL. Multiple factors influence the normal and UV-inducible alternative splicing of PIG3. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1779:838-49. [DOI: 10.1016/j.bbagrm.2008.08.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Revised: 08/15/2008] [Accepted: 08/20/2008] [Indexed: 10/21/2022]
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45
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David CJ, Manley JL. The search for alternative splicing regulators: new approaches offer a path to a splicing code. Genes Dev 2008; 22:279-85. [PMID: 18245441 DOI: 10.1101/gad.1643108] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Charles J David
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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Abstract
The sequencing of the human genome and ensuing wave of data generation have brought new light upon the extent and importance of alternative splicing as an RNA regulatory mechanism. Alternative splicing could potentially explain the complexity of protein repertoire during evolution, and defects in the splicing mechanism are responsible for diseases as complex as cancer. Among the challenges that rise in light of these discoveries are cataloguing splice variation in the human and other eukaryotic genomes, and identifying and characterizing the splicing regulatory elements that control their expression. Bioinformatics efforts tackling these two questions are just at the beginning. This article is a survey of these methods.
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Affiliation(s)
- Liliana Florea
- Department of Computer Science, George Washington University, Academic Center-Rm 714, Washington DC 20052, USA.
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Caffeine regulates alternative splicing in a subset of cancer-associated genes: a role for SC35. Mol Cell Biol 2007; 28:883-95. [PMID: 18025108 DOI: 10.1128/mcb.01345-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alternative splicing of pre-mRNA contributes significantly to human proteomic complexity, playing a key role in development, gene expression and, when aberrant, human disease onset. Many of the factors involved in alternative splicing have been identified, but little is known about their regulation. Here we report that caffeine regulates alternative splicing of a subset of cancer-associated genes, including the tumor suppressor KLF6. This regulation is at the level of splice site selection, occurs rapidly and reversibly, and is concentration dependent. We have recapitulated caffeine-induced alternative splicing of KLF6 using a cell-based minigene assay and identified a "caffeine response element" within the KLF6 intronic sequence. Significantly, a chimeric minigene splicing assay demonstrated that this caffeine response element is functional in a heterologous context; similar elements exist within close proximity to caffeine-regulated exons of other genes in the subset. Furthermore, the SR splicing factor, SC35, was shown to be required for induction of the alternatively spliced KLF6 transcript. Importantly, SC35 is markedly induced by caffeine, and overexpression of SC35 is sufficient to mimic the effect of caffeine on KLF6 alternative splicing. Taken together, our data implicate SC35 as a key player in caffeine-mediated splicing regulation. This novel effect of caffeine provides a valuable tool for dissecting the regulation of alternative splicing of a large gene subset and may have implications with respect to splice variants associated with disease states.
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48
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Abstract
Alternative pre-mRNA splicing has an important role in the control of neuronal gene expression. Many neuronal proteins are structurally diversified through the differential inclusion and exclusion of sequences in the final spliced mRNA. Here, we discuss common mechanisms of splicing regulation and provide examples of how alternative splicing has important roles in neuronal development and mature neuron function. Finally, we describe regulatory proteins that control the splicing of some neuronally expressed transcripts.
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Affiliation(s)
- Qin Li
- Howard Hughes Medical Institute, University of California, Los Angeles, 6-762 MacDonald Research Laboratories, 675 Charles E. Young Drive South, Los Angeles, California 90095, USA
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The Fox-1 family and SUP-12 coordinately regulate tissue-specific alternative splicing in vivo. Mol Cell Biol 2007; 27:8612-21. [PMID: 17923701 DOI: 10.1128/mcb.01508-07] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many pre-mRNAs are alternatively spliced in a tissue-specific manner in multicellular organisms. The Fox-1 family of RNA-binding proteins regulate alternative splicing by either activating or repressing exon inclusion through specific binding to UGCAUG stretches. However, the precise cellular contexts that determine the action of the Fox-1 family in vivo remain to be elucidated. We have recently demonstrated that ASD-1 and FOX-1, members of the Fox-1 family in Caenorhabditis elegans, regulate tissue-specific alternative splicing of the fibroblast growth factor receptor gene, egl-15, which eventually determines the ligand specificity of the receptor in vivo. Here we report that another RNA-binding protein, SUP-12, coregulates the egl-15 alternative splicing. By screening for mutants defective in the muscle-specific expression of our alternative splicing reporter, we identified the muscle-specific RNA-binding protein SUP-12. We identified juxtaposed conserved stretches as the cis elements responsible for the regulation. The Fox-1 family and the SUP-12 proteins form a stable complex with egl-15 RNA, depending on the cis elements. Furthermore, the asd-1; sup-12 double mutant is defective in sex myoblast migration, phenocopying the isoform-specific egl-15(5A) mutant. These results establish an in vivo model that coordination of the two families of RNA-binding proteins regulates tissue-specific alternative splicing of a specific target gene.
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Yang G, Huang SC, Wu JY, Benz EJ. Regulated Fox-2 isoform expression mediates protein 4.1R splicing during erythroid differentiation. Blood 2007; 111:392-401. [PMID: 17715393 PMCID: PMC2200819 DOI: 10.1182/blood-2007-01-068940] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A regulated splicing event in protein 4.1R pre-mRNA-the inclusion of exon 16-encoding peptides for spectrin-actin binding-occurs in late erythroid differentiation. We defined the functional significance of an intronic splicing enhancer, UGCAUG, and its cognate splicing factor, mFox2A, on exon 16 splicing during differentiation. UGCAUG displays cell-type-specific splicing regulation in a test neutral reporter and has a dose-dependent enhancing effect. Erythroid cells express 2 UGCAUG-binding mFox-2 isoforms, an erythroid differentiation-inducible mFox-2A and a commonly expressed mFox-2F. When overexpressed, both enhanced internal exon splicing in an UGCAUG-dependent manner, with mFox-2A exerting a much stronger effect than mFox-2F. A significant reciprocal increase in mFox-2A and decrease in mFox-2F occurred during erythroid differentiation and correlated with exon 16 inclusion. Furthermore, isoform-specific expression reduction reversed mFox-2A-enhancing activity, but not that of mFox-2F on exon 16 inclusion. Our results suggest that an erythroid differentiation-inducible mFox-2A isoform is a critical regulator of the differentiation-specific exon 16 splicing switch, and that its up-regulation in late erythroid differentiation is vital for exon 16 splicing.
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Affiliation(s)
- Guang Yang
- Department of Medical Oncology, Dana-Farber Cancer Institute, 44 Binney St, Boston, MA 02115, USA
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