Human CWC22 escorts the helicase eIF4AIII to spliceosomes and promotes exon junction complex assembly

Nat Struct Mol Biol. 2012 Oct;19(10):983-90. doi: 10.1038/nsmb.2380. Epub 2012 Sep 9.


The exon-junction complex (EJC) functionally links splicing to subsequent mRNA localization, translation and stability. Sequence-independent binding of the EJC core to RNA is ensured by the DEAD-box helicase eIF4AIII. Here, we identified the splicing factor CWC22 as a new eIF4AIII partner in flies and humans. CWC22 coexists with eIF4AIII in large protein complexes distinct from EJCs. Recombinant CWC22 directly contacts eIF4AIII and prevents it from binding RNA. In vitro splicing assays revealed that CWC22 introduces eIF4AIII to spliceosomes before remodeling to facilitate eIF4AIII incorporation into the EJC. Finally, using knockdowns in vivo, we showed that CWC22 is essential for EJC assembly. We elucidated the initial step of EJC assembly and the duality of CWC22 function that hinders eIF4AIII from nonspecifically binding RNA and escorts it to the splicing machinery to promote EJC assembly on mature mRNAs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / metabolism*
  • DNA Repair Enzymes / genetics
  • DNA Repair Enzymes / metabolism
  • Eukaryotic Initiation Factor-4A / genetics
  • Eukaryotic Initiation Factor-4A / metabolism*
  • Exons*
  • Gene Knockdown Techniques
  • Humans
  • Molecular Sequence Data
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Peptidylprolyl Isomerase
  • Protein Interaction Domains and Motifs
  • Protein Structure, Tertiary
  • RNA / metabolism
  • RNA Splicing
  • RNA Splicing Factors
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Spliceosomes / metabolism*


  • CWC22 protein, human
  • Carrier Proteins
  • Nuclear Proteins
  • RNA Splicing Factors
  • RNA, Messenger
  • RNA-Binding Proteins
  • Recombinant Proteins
  • RNA
  • Eukaryotic Initiation Factor-4A
  • EIF4A3 protein, human
  • DEAD-box RNA Helicases
  • Peptidylprolyl Isomerase
  • DNA Repair Enzymes
  • PRPF19 protein, human