Magoh, a human homolog of Drosophila mago nashi protein, is a component of the splicing-dependent exon-exon junction complex

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Abstract
The RNA‐binding protein Y14 binds preferentially to mRNAs produced by splicing and is a component of a multiprotein complex that assembles ∼20 nucleotides upstream of exon–exon junctions. This complex probably has important functions in post‐splicing events including nuclear export and nonsense‐mediated decay of mRNA. We show that Y14 binds to two previously reported components, Aly/REF and RNPS1, and to the mRNA export factor TAP. Moreover, we identified magoh, a human homolog of the Drosophila mago nashi gene product, as a novel component of the complex. Magoh binds avidly and directly to Y14 and TAP, but not to other known components of the complex, and is found in Y14‐containing mRNPs in vivo . Importantly, magoh also binds to mRNAs produced by splicing upstream (∼20 nucleotides) of exon– exon junctions and its binding to mRNA persists after export. These experiments thus reveal specific protein–protein interactions among the proteins of the splicing‐dependent mRNP complex and suggest an important role for the highly evolutionarily conserved magoh protein in this complex.