Multiple mechanisms collaborate to repress XXXX translation in the @entity238 ovary and embryo.

@entity23059 @entity2270 @entity72716 @entity23061 @entity238
Translational control of gene expression is essential for development in organisms that rely on maternal mRNAs. In @entity238 , translation of maternal @entity23061 (nos) mRNA must be restricted to the posterior of the early embryo for proper patterning of the anterior-posterior @entity2270 . Spatial control of nos translation is coordinated through the localization of a small subset of nos mRNA to the posterior pole late in oogenesis, activation of this localized mRNA, and repression of the remaining unlocalized nos mRNA throughout the bulk cytoplasm. Translational repression is mediated by the interaction of a cis-acting element in the nos 3' untranslated region with two proteins, @entity72716 ( @entity72716 ) and @entity23059 ( @entity23059 ), that function in the oocyte and embryo, respectively. The mechanism of @entity72716 -dependent repression is unknown. Previous work suggests that @entity23059 represses translation initiation but this model is not easily reconciled with evidence for polysome association of repressed nos mRNA. Using an in vitro translation system, we have decoupled translational repression of nos imposed during oogenesis from repression during embryogenesis. Our results suggest that both @entity72716 and @entity23059 regulate translation initiation, but by different mechanisms. Furthermore, we show that, during late oogenesis, nos translation is also repressed post-initiation and provide evidence that @entity72716 mediates this event. This post-initiation block is maintained into embryogenesis during the transition to @entity23059 -dependent regulation. We propose that the use of multiple modes of repression ensures inactivation of nos RNA that is translated at earlier stages of oogenesis and maintenance of this inactivate state throughout late oogenesis into embryogenesis.
