cl03715

Mago nashi proteins, integral members of the exon junction complex; Members of this family, which was originally identified in Drosophila and called mago nashi, are integral members of the exon junction complex (EJC). The EJC is a multiprotein complex that is deposited on spliced mRNAs after intron removal at a conserved position upstream of the exon-exon junction, and transported to the cytoplasm where it has been shown to influence translation, surveillance, and localization of the spliced mRNA. It consists of four core proteins (eIF4AIII, Barentsz [Btz], Mago, and Y14), mRNA, and ATP and is supposed to be a binding platform for more peripherally and transiently associated factors along mRNA travel. Mago and Y14 form a stable heterodimer that stabilizes the complex by inhibiting eIF4AIII's ATPase activity. In humans, but not Drosophila, EJC is involved in nonsense-mediated mRNA decay (NMD) via binding to Upf3b, a central NMD effector. EJC is stripped off the mRNA during the first round of translation and then the complex components are transported back into the nucleus and recycled. The Mago-Y14 heterodimer has been shown to interact with the cytoplasmic protein PYM, an EJC disassembly factor, and specifically binds to the karyopherin nuclear receptor importin 13.