Tap and NXT promote translation of unspliced mRNA
Abstract
Tap has been proposed to play a role in general mRNA export and also functions in expression of RNA with retained introns that contain the MPMV CTE (constitutive transport element). Tap forms a functional heterodimer with NXT/p15. We have previously demonstrated that unspliced intron-containing CTE RNA is efficiently exported to the cytoplasm in mammalian cells. Here we show that Tap and NXT proteins function together to enhance translation of proteins from the exported CTE RNA. Pulse chase experiments show that Tap/NXT significantly increases the rate of protein synthesis. Sucrose gradient analysis demonstrates that Tap and NXT efficiently shift the unspliced RNA into polyribosomal fractions. Furthermore, Tap, but not NXT is detected in polyribosomes. Taken together, our results indicate that Tap and NXT serve a role in translational regulation of RNA after export to the cytoplasm. They further suggest that Tap/NXT may play a role in remodeling of cytoplasmic RNP complexes, providing a link between export pathways and cytoplasmic fate.
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Footnotes
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Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1155703.
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↵1 Present address: Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA.
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↵2 Corresponding author. E-MAIL mh7g{at}virginia.edu; FAX (434) 982-1590.
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- Accepted October 28, 2003.
- Received September 26, 2003.
- Cold Spring Harbor Laboratory Press