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| The EMBO Journal
(2001) 20, 4987–4997, doi:10.1093/emboj/20.17.4987 |
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| The exon–exon junction complex provides a binding platform for factors involved in mRNA export and nonsense-mediated mRNA decay |
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| Hervé Le Hir1, David Gatfield2, Elisa Izaurralde2 and Melissa J. Moore1 |
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1 Howard Hughes Medical Institute, Department of Biochemistry, Brandeis University, 415 South Street, Waltham, MA 02454, USA 2 European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, D-69117 Heidelberg, Germany To whom correspondence should be addressed Melissa J. Moore, mmoore@brandeis.edu Received 22 May 2001; Revised 18 July 2001; Accepted 18 July 2001. |
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| Abstract |
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| We recently reported that spliceosomes alter messenger ribonucleoprotein particle (mRNP) composition by depositing several proteins 20–24 nucleotides upstream of mRNA exon–exon junctions. When assembled in vitro, this so-called 'exon–exon junction complex' (EJC) contains at least five proteins: SRm160, DEK, RNPS1, Y14 and REF. To better investigate its functional attributes, we now describe a method for generating spliced mRNAs both in vitro and in vivo that either do or do not carry the EJC. Analysis of these mRNAs in Xenopus laevis oocytes revealed that this complex is the species responsible for enhancing nucleocytoplasmic export of spliced mRNAs. It does so by providing a strong binding site for the mRNA export factors REF and TAP/p15. Moreover, by serving as an anchoring point for the factors Upf2 and Upf3, the EJC provides a direct link between splicing and nonsense-mediated mRNA decay. Finally, we show that the composition of the EJC is dynamic in vivo and is subject to significant evolution upon mRNA export to the cytoplasm. |
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| Keywords: exon–exon junction complex, mRNA export, nonsense-mediated decay, pre-mRNA splicing |
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