Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
J Cell Biol. 2010 May 17;189(4):755-67. doi: 10.1083/jcb.200912011. Epub 2010 May 10.
In Saccharomyces cerevisiae, ASH1 mRNA is transported to the bud tip by the class V myosin Myo4. In vivo, Myo4 moves RNA in a rapid and continuous fashion, but in vitro Myo4 is a nonprocessive, monomeric motor that forms a complex with She3. To understand how nonprocessive motors generate continuous transport, we used a novel purification method to show that Myo4, She3, and the RNA-binding protein She2 are the sole major components of an active ribonucleoprotein transport unit. We demonstrate that a single localization element contains multiple copies of Myo4 and a tetramer of She2, which suggests that She2 may recruit multiple motors to an RNA. Furthermore, we show that increasing the number of Myo4-She3 molecules bound to ASH1 RNA in the absence of She2 increases the efficiency of RNA transport to the bud. Our data suggest that multiple, nonprocessive Myo4 motors can generate continuous transport of mRNA to the bud tip.
在酿酒酵母中，ASH1 mRNA 由 V 类肌球蛋白 Myo4 运送到芽尖。在体内，Myo4 以快速和连续的方式移动 RNA，但在体外，Myo4 是一种非进展性的单体马达，它与 She3 形成复合物。为了理解非进展性马达如何产生连续运输，我们使用一种新的纯化方法表明，Myo4、She3 和 RNA 结合蛋白 She2 是活性核糖核蛋白运输单元的唯一主要成分。我们证明，单个定位元件包含多个 Myo4 拷贝和 She2 的四聚体，这表明 She2 可能将多个马达募集到一个 RNA 上。此外，我们表明，在没有 She2 的情况下，增加与 ASH1 RNA 结合的 Myo4-She3 分子的数量会增加 RNA 向芽运输的效率。我们的数据表明，多个非进展性的 Myo4 马达可以产生 mRNA 向芽尖的连续运输。
