exon junction complex (EJC)

Function

• dynamic structure consisting of a few core proteins & several more peripheral nuclear & cytoplasmic associated factors that join the complex only transiently either during assembly or during subsequent mRNA metabolism
• core components that remain bound to spliced mRNAs throughout all stages of mRNA metabolism, function to mark the position of the exon-exon junction in the mature mRNA & thus influence downstream processes of gene expression including
  • mRNA splicing
  • nuclear mRNA export
  • subcellular mRNA localization
  • translation efficiency
  • nonsense-mediated mRNA decay (NMD)
• remains associated with mRNAs in the cytoplasm until the mRNAs engage the translation machinery
• its removal from cytoplasmic mRNAs requires translation initiation from EJC-bearing spliced mRNAs
• associates preferentially with mRNAs produced by splicing
• does not interact with pre-mRNAs, introns, or mRNAs produced from intronless cDNAs
• associates with both nuclear mRNAs & newly exported cytoplasmic mRNAs

Structure

• subunits: NCBP1, NCBP2, RNPS1, RBM8A, SRRM1, NXF1, NFX1, RENT1, RENT2, RENT3A, RENT3B, THOC4, MAGOH, CASC3, EIF4A3, ACIN1, DEK, EIF4A3, PNN, SAP18

Compartment

translocates from nucleus to cytoplasm

More general terms

• molecular complex

Components

• THO/TREX complex
• nuclear mRNA cap-binding protein