Key regulator of the exon junction complex (EJC), a multiprotein complex that associates immediately upstream of the exon-exon junction on mRNAs and serves as a positional landmark for the intron exon structure of genes and directs post-transcriptional processes in the cytoplasm such as mRNA export, nonsense-mediated mRNA decay (NMD) or translation. Acts as an EJC disassembly factor, allowing translation-dependent EJC removal and recycling by disrupting mature EJC from spliced mRNAs. Its association with the 40S ribosomal subunit probably prevents a translation-independent disassembly of the EJC from spliced mRNAs, by restricting its activity to mRNAs that have been translated. Interferes with NMD and enhances translation of spliced mRNAs, probably by antagonizing EJC functions (By similarity). Interacts (via N-terminus) with magoh and rbm8a; the interaction is direct. Associates (eIF2A-like region) with the 40S ribosomal subunit and the 48S preinitiation complex (By similarity). Shuttles between the nucleus and the cytoplasm. Nuclear export is mediated by XPO1/CRM1. Belongs to the pym family.