Core component of the splicing-dependent multiprotein exon junction complex (EJC) deposited at splice junctions on mRNAs. The EJC is a dynamic structure consisting of core proteins and several peripheral nuclear and cytoplasmic associated factors that join the complex only transiently either during EJC assembly or during subsequent mRNA metabolism. The EJC marks the position of the exon-exon junction in the mature mRNA for the gene expression machinery and the core components remain bound to spliced mRNAs throughout all stages of mRNA metabolism thereby influencing downstream processes including nuclear mRNA export, subcellular mRNA localization, translation efficiency and nonsense-mediated mRNA decay (NMD). The MAGO-Y14 heterodimer inhibits the ATPase activity of EIF4A3, thereby trapping the ATP-bound EJC core onto spliced mRNA in a stable conformation. The MAGO-Y14 heterodimer interacts with the EJC key regulator PYM leading to EJC disassembly in the cytoplasm (By similarity). EJC core heterodimers play essential roles in plant growth and development, and pollen and seed development (PubMed:25230811, PubMed:24820023). The MAGO-Y14 heterodimer selectively binds to the UDT1 (UNDEVELOPED TAPETUM 1) pre-mRNA transcript and regulates the splicing of UDT1, a key regulator in stamen development (PubMed:24820023). Heterodimers with MAGO1 and MAGO2 (PubMed:24416299, PubMed:25230811, PubMed:24820023). Interacts with EIF4A3/RH2 and RH34 (PubMed:27071313). Part of the mRNA splicing-dependent exon junction complex (EJC); the core complex contains MLN51/CASC3, EIF4A3, MAGO and Y14 (Probable). Nucleocytoplasmic shuttling protein. Travels to the cytoplasm as part of the exon junction complex (EJC) bound to mRNA. Belongs to the RBM8A family. Sequencing errors.