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Mol Cell. 2003 Mar;11(3):837-43.

SR splicing factors serve as adapter proteins for TAP-dependent mRNA export.

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Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, CT 06536, USA.


The only mammalian RNA binding adapter proteins known to partner with TAP/NXF1, the primary receptor for general mRNA export, are members of the REF family. We demonstrate that at least three shuttling SR (serine/arginine-rich) proteins interact with the same domain of TAP/NXF1 that binds REFs. Included are 9G8 and SRp20, previously shown to promote the export of intronless RNAs. A peptide derived from the N terminus of 9G8 inhibits the binding of both REF and SR proteins to TAP/NXF1 in vitro, and this finding argues for competitive interactions. In Xenopus oocytes, the N terminus of 9G8 exhibits a dominant-negative effect on mRNA export from the nucleus, while addition of excess TAP/NXF1 overcomes this inhibition. Thus, multiple adapters including SR proteins most likely cooperate to recruit multiple copies of TAP/NXF1 for efficient mRNA export.

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