Perispeckles are major assembly sites for the exon junction core complex

Mol Biol Cell. 2012 May;23(9):1765-82. doi: 10.1091/mbc.E12-01-0040. Epub 2012 Mar 14.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Nucleus / chemistry
  • Cell Nucleus / metabolism*
  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / metabolism*
  • Eukaryotic Initiation Factor-4A
  • Exons*
  • HeLa Cells
  • Humans
  • Mutation
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Protein Binding
  • RNA Splicing / genetics*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Transfection


  • CASC3 protein, human
  • MAGOH protein, human
  • Neoplasm Proteins
  • Nuclear Proteins
  • RBM8A protein, human
  • RNA, Messenger
  • RNA-Binding Proteins
  • Eukaryotic Initiation Factor-4A
  • EIF4A3 protein, human
  • DEAD-box RNA Helicases