title: Perispeckles are major assembly sites for the exon junction core complex.
abstract: The exon junction complex (EJC) is loaded onto mRNAs as a consequence of splicing and regulates multiple posttranscriptional events. MLN51, Magoh, Y14, and eIF4A3 form a highly stable EJC core, but where this tetrameric complex is assembled in the cell remains unclear. Here we show that EJC factors are enriched in domains that we term perispeckles and are visible as doughnuts around nuclear speckles. Fluorescence resonance energy transfer analyses and EJC assembly mutants show that perispeckles do not store free subunits, but instead are enriched for assembled cores. At the ultrastructural level, perispeckles are distinct from interchromatin granule clusters that may function as storage sites for splicing factors and intermingle with perichromatin fibrils, where nascent RNAs and active RNA Pol II are present. These results support a model in which perispeckles are major assembly sites for the tetrameric EJC core. This subnuclear territory thus represents an intermediate region important for mRNA maturation, between transcription sites and splicing factor reservoirs and assembly sites.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, Unité Mixte de Recherche 7104, Centre National de la Recherche Scientifique/U964 Institut National de Santé et de Recherche Médicale/Université de Strasbourg, 67404 Illkirch, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Daguenet
authors.forename: Aurélie
authors.initials: A
authors.lastname: Baguet
authors.forename: Sébastien
authors.initials: S
authors.lastname: Degot
authors.forename: Ute
authors.initials: U
authors.lastname: Schmidt
authors.forename: Fabien
authors.initials: F
authors.lastname: Alpy
authors.forename: Corinne
authors.initials: C
authors.lastname: Wendling
authors.forename: Coralie
authors.initials: C
authors.lastname: Spiegelhalter
authors.forename: Pascal
authors.initials: P
authors.lastname: Kessler
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Rio
authors.forename: Hervé
authors.initials: H
authors.lastname: Le Hir
authors.forename: Edouard
authors.initials: E
authors.lastname: Bertrand
authors.forename: Catherine
authors.initials: C
authors.lastname: Tomasetto
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D039601:Eukaryotic Initiation Factor-4A; D005091:Exons; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: C459802:CASC3 protein, human; C491494:MAGOH protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C406243:RBM8A protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D039601:Eukaryotic Initiation Factor-4A; C403493:EIF4A3 protein, human; D053487:DEAD-box RNA Helicases