Lieberfarb M E, Chu T, Wreden C, Theurkauf W, Gergen J P, Strickland S
Department of Pharmacology, University Medical Center at Stony Brook, NY 11794-8651, USA.
Development. 1996 Feb;122(2):579-88. doi: 10.1242/dev.122.2.579.
Translational recruitment of maternal mRNAs is an essential process in early metazoan development. To identify genes required for this regulatory pathway, we have examined a collection of Drosophila female-sterile mutants for defects in translation of maternal mRNAs. This strategy has revealed that maternal-effect mutations in the cortex and grauzone genes impair translational activation and cytoplasmic polyadenylation of bicoid and Toll mRNAs. Cortex embryos contain a bicoid mRNA indistinguishable in amount, localization, and structure from that in wild-type embryos. However, the bicoid mRNA in cortex embryos contains a shorter than normal polyadenosine (poly(A)) tail. Injection of polyadenylated bicoid mRNA into cortex embryos allows translation demonstrating that insufficient polyadenylation prevents endogenous bicoid mRNA translation. In contrast nanos mRNA, which is activated by a poly(A)-independent mechanism, is translated in cortex embryos, indicating that the block in maternal mRNA activation is specific to a class of mRNAs. Cortex embryos are fertilized, but arrest at the onset of embryogenesis. Characterization of grauzone mutations indicates that the phenotype of these embryos is similar to cortex. These results identify a fundamental pathway that serves a vital role in the initiation of development.
母源mRNA的转译募集是后生动物早期发育中的一个重要过程。为了鉴定这一调控途径所需的基因，我们检查了一系列果蝇雌性不育突变体，以寻找母源mRNA翻译方面的缺陷。这一策略表明，皮层（cortex）基因和格劳佐内（grauzone）基因的母性效应突变会损害双尾（bicoid）和Toll mRNA的转译激活及细胞质多聚腺苷酸化。皮层突变体胚胎中的双尾mRNA在数量、定位和结构上与野生型胚胎中的并无差异。然而，皮层突变体胚胎中的双尾mRNA含有比正常短的多聚腺苷酸（poly(A)）尾。将多聚腺苷酸化的双尾mRNA注入皮层突变体胚胎可使其发生转译，这表明多聚腺苷酸化不足会阻止内源性双尾mRNA的转译。相比之下，通过一种不依赖于poly(A)的机制被激活的纳米（nanos）mRNA在皮层突变体胚胎中能够转译，这表明母源mRNA激活受阻是一类mRNA所特有的。皮层突变体胚胎能够受精，但在胚胎发生开始时就会停滞发育。对格劳佐内突变的特征分析表明，这些胚胎的表型与皮层突变体相似。这些结果确定了一条在发育起始中起关键作用的基本途径。
