The process of mRNA localization, often used for regulation of gene expression in polarized cells, requires recognition of cis-acting signals by components of the localization machinery. Many known RNA signals are active in the contexts of both the Drosophila ovary and the blastoderm embryo, suggesting a conserved recognition mechanism. We used variants of the bicoid mRNA localization signal to explore recognition requirements in the embryo. We found that bicoid stem-loop IV/V, which is sufficient for ovarian localization, was necessary but not sufficient for full embryonic localization. RNAs containing bicoid stem-loops III/IV/V did localize within the embryo, demonstrating a requirement for dimerization and other activities supplied by stem-loop III. Protein complexes that bound specifically to III/IV/V and fushi tarazu localization signals copurified through multiple fractionation steps, suggesting that they are related. Binding to these two signals was competitive but not equivalent. Thus, the binding complexes are not identical but appear to have some components in common. We have proposed a model for a conserved mechanism of localization signal recognition in multiple contexts.
展开▼
机译:mRNA定位过程通常用于调节极化细胞中的基因表达,需要通过定位机制的组件来识别顺式作用信号。在果蝇卵巢和胚盘胚的背景下,许多已知的RNA信号均具有活性,这提示了保守的识别机制。我们使用了二倍体mRNA定位信号的变体来探索胚胎中的识别要求。我们发现,对于卵巢定位来说足够的二倍体茎环IV / V是必需的,但对于完整的胚胎定位是不够的。包含二倍体茎环III / IV / V的RNA确实位于胚胎内,表明需要二聚化和茎环III提供的其他活性。特异性结合III / IV / V和fushi tarazu定位信号的蛋白复合物通过多个分级分离步骤共纯化,表明它们是相关的。绑定到这两个信号是竞争性的,但并不等效。因此,结合复合物并不相同,但似乎具有一些共同的成分。我们提出了一种在多种情况下用于定位信号识别的保守机制的模型。
展开▼