European Molecular Biology Laboratory, Heidelberg, Germany.
RNA. 2011 Dec;17(12):2049-57. doi: 10.1261/rna.2686411. Epub 2011 Oct 25.
mRNA localization coupled with translational control is a highly conserved and widespread mechanism for restricting protein expression to specific sites within eukaryotic cells. In Drosophila, patterning of the embryo requires oskar mRNA transport to the posterior pole of the oocyte and translational repression prior to localization. oskar RNA splicing and the 3' untranslated region (UTR) are required for posterior enrichment of the mRNA. However, reporter RNAs harboring the oskar 3' UTR can localize by hitchhiking with endogenous oskar transcripts. Here we show that the oskar 3' UTR contains a stem-loop structure that promotes RNA dimerization in vitro and hitchhiking in vivo. Mutations in the loop that abolish in vitro dimerization interfere with reporter RNA localization, and restoring loop complementarity restores hitchhiking. Our analysis provides insight into the molecular basis of RNA hitchhiking, whereby localization-incompetent RNA molecules can become locally enriched in the cytoplasm, by virtue of their association with transport-competent RNAs.
mRNA 定位与翻译调控是一种高度保守且广泛存在的机制，可将蛋白质表达限制在真核细胞内的特定部位。在果蝇中，胚胎的模式形成需要 Oskar mRNA 运输到卵母细胞的后极，并在定位之前进行翻译抑制。Oskar RNA 剪接和 3'非翻译区（UTR）对于 mRNA 的后极富集是必需的。然而，携带 Oskar 3'UTR 的报告 RNA 可以通过与内源性 Oskar 转录物的搭便车而定位。在这里，我们表明 Oskar 3'UTR 包含一个茎环结构，该结构可促进体外 RNA 二聚化和体内搭便车。消除体外二聚化的环突变会干扰报告 RNA 的定位，而恢复环互补性则恢复搭便车。我们的分析提供了对 RNA 搭便车分子基础的深入了解，即由于与运输能力强的 RNA 相关联，定位能力不足的 RNA 分子可以在细胞质中局部富集。
