Takizawa P A, Sil A, Swedlow J R, Herskowitz I, Vale R D
Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California, San Francisco 94143-0450, USA.
Nature. 1997 Sep 4;389(6646):90-3. doi: 10.1038/38015.
The cytoplasmic localization of messenger RNA creates an asymmetric distribution of proteins that specify cell fate during development in multicellular eukaryotes. The protein Ash1 is a cell-fate determinant in budding yeast which localizes preferentially to the presumptive daughter nucleus, where it inhibits mating-type switching. Here we show that Ash1 mRNA is localized to the distal tip of daughter buds in post-anaphase cells. Three-dimensional imaging reveals that Ash1 mRNA is assembled into particles that associate with the cell cortex. To achieve this localization, Ash1 mRNA must have its 3' untranslated region and the actin cytoskeleton must be intact. Ash1 mRNA is not localized correctly in the absence of a myosin (Myo4) and is mislocalized to the mother-bud neck in the absence of a regulator of the actin cytoskeleton known as Bnil. We propose that Ash1 mRNA particles are transported into the daughter bud along actin filaments and are anchored at the distal tip. Thus, as in higher eukaryotes, Saccharomyces cerevisiae employs RNA localization to generate an asymmetric distribution of proteins and hence to determine cell fate.
信使核糖核酸（mRNA）的细胞质定位产生了蛋白质的不对称分布，这种分布在多细胞真核生物发育过程中决定细胞命运。蛋白质Ash1是芽殖酵母中的一种细胞命运决定因子，它优先定位于推测的子细胞核，在那里它抑制交配型转换。我们在此表明，Ash1 mRNA定位于后期细胞中芽体的远端。三维成像显示，Ash1 mRNA组装成与细胞皮层相关的颗粒。为实现这种定位，Ash1 mRNA必须有其3'非翻译区，并且肌动蛋白细胞骨架必须完整。在没有肌球蛋白（Myo4）的情况下，Ash1 mRNA不能正确定位，而在没有一种称为Bnil的肌动蛋白细胞骨架调节因子的情况下，它会错误定位于母-芽颈。我们提出，Ash1 mRNA颗粒沿着肌动蛋白丝被转运到芽体中，并锚定在远端。因此，正如在高等真核生物中一样，酿酒酵母利用RNA定位来产生蛋白质的不对称分布，从而决定细胞命运。
