Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
Elife. 2018 Jun 26;7:e36312. doi: 10.7554/eLife.36312.
Polarised mRNA transport is a prevalent mechanism for spatial control of protein synthesis. However, the composition of transported ribonucleoprotein particles (RNPs) and the regulation of their movement are poorly understood. We have reconstituted microtubule minus end-directed transport of mRNAs using purified components. A Bicaudal-D (BicD) adaptor protein and the RNA-binding protein Egalitarian (Egl) are sufficient for long-distance mRNA transport by the dynein motor and its accessory complex dynactin, thus defining a minimal transport-competent RNP. Unexpectedly, the RNA is required for robust activation of dynein motility. We show that a -acting RNA localisation signal promotes the interaction of Egl with BicD, which licenses the latter protein to recruit dynein and dynactin. Our data support a model for BicD activation based on RNA-induced occupancy of two Egl-binding sites on the BicD dimer. Scaffolding of adaptor protein assemblies by cargoes is an attractive mechanism for regulating intracellular transport.
极化的 mRNA 运输是蛋白质合成空间控制的一种普遍机制。然而，运输核糖核蛋白颗粒（RNP）的组成及其运动的调节仍知之甚少。我们使用纯化的成分重新构建了微管负端导向的 mRNA 运输。Bicaudal-D（BicD）衔接蛋白和 RNA 结合蛋白平等主义者（Egl）足以通过动力蛋白及其辅助复合物 dynactin 进行长距离 mRNA 运输，从而定义了最小的运输活性 RNP。出乎意料的是，RNA 对于动力蛋白运动的强烈激活是必需的。我们表明，一种肌动蛋白定位信号促进了 Egl 与 BicD 的相互作用，从而使后者蛋白能够招募动力蛋白和 dynactin。我们的数据支持基于 RNA 诱导的 BicD 二聚体上两个 Egl 结合位点占据的 BicD 激活模型。货物支架衔接蛋白组装是调节细胞内运输的一种有吸引力的机制。
