Cell Biology

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Science  06 May 2011:
Vol. 332, Issue 6030, pp. 643
DOI: 10.1126/science.332.6030.643-b

Localized translation of mRNA in eukaryotes is essential for regulating gene expression. Localized mRNAs contain specific sequences that target them for recognition and incorporation into messenger ribonucleoprotein particles (mRNPs) and also recruit motor proteins; however, how selective transport is achieved remains unclear. Müller et al. used in vitro reconstitution assays and in vivo experiments to investigate how Saccharomyces cerevisiae ASH1-mRNA, which is transported from the mother to the daughter cell during mitosis, is incorporated into mRNPs. Surprisingly, two RNA-binding proteins, She2p and Puf6p, implicated in escorting ASH1 mRNA from the nucleus to the cytoplasm, were found to display little specificity for cargo RNAs. Instead, She3p, which was previously identified as an adaptor that brings the motor myosin V into the mRNAp, bound to She2p and also bound weakly to cargo RNAs. The RNA binding of She2p and She3p was synergistic, so that together the two form a specific ternary complex with the mRNA, stabilizing the She2p:She3p interaction. These data suggest that the mRNA cargos are bound with only limited specificity for nuclear export. A stable and specific transport complex then forms in the cytoplasm and mediates appropriate localization of the cargo mRNA.

PLoS Biol. 9, e1000611 (2011).

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