Structure-function studies of nucleocytoplasmic transport of retroviral genomic RNA by mRNA export factor TAP

Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.
Nature Structural & Molecular Biology (Impact Factor: 13.31). 08/2011; 18(9):990-8. DOI: 10.1038/nsmb.2094
Source: PubMed


mRNA export is mediated by the TAP-p15 heterodimer, which belongs to the family of NTF2-like export receptors. TAP-p15 heterodimers also bind to the constitutive transport element (CTE) present in simian type D retroviral RNAs, and they mediate the export of viral unspliced RNAs to the host cytoplasm. We have solved the crystal structure of the RNA recognition and leucine-rich repeat motifs of TAP bound to one symmetrical half of the CTE RNA. L-shaped conformations of protein and RNA are involved in a mutual molecular embrace on complex formation. We have monitored the impact of structure-guided mutations on binding affinities in vitro and transport assays in vivo. Our studies define the principles by which CTE RNA subverts the mRNA export receptor TAP, thereby facilitating the nuclear export of viral genomic RNAs, and, more generally, provide insights on cargo RNA recognition by mRNA export receptors.

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Available from: Elisa Izaurralde, Sep 09, 2014
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    • "Possible explanations for this effect are changes in mRNA stability, a preferential export of specific transcripts, or as our RT-qPCR data suggests, the defect in mRNA export likely leads to a lengthened nuclear residency and might increase the likelihood of splicing, increasing the green to red ratio (Fig. 2B). It is also important to note that others have used translationally competent reporter pre-mRNAs as mRNA export reporters, providing further support for the green-shifted effect we observe (Galy et al. 2004; Dufu et al. 2010; Teplova et al. 2011; Caporilli et al. 2013). One interesting green-shifted phenograph was that of the mlp1Δ mutant (Fig. 4D), a result of a nearly 80% decrease in mCherry signal, with a minor change in GFP. "
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    • "Later, TAP was demonstrated to be involved in the nuclear-cytoplasmic transport of the unspliced or partially spliced RNA of retroviruses. TAP directly recognizes only one sequence—CTE (Constitutive Transport Element)—which was initially discovered in RNAs of retroviruses [15] [16] [17] [18]. Adaptor proteins mediate the interaction between NXF1 and cellular mRNAs in metazoan [19] [20] [21]. "
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    • "Moreover, our results suggest that RNH1 binds to pri-miR-21 as well. Indeed, the mRNA export factor TAP/hNXF1 binds to retroviral genomic RNA through the LRRs [40]. Therefore, RNH1 may bind directly to pri-miR-21 through the LRRs. "
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