Apontic binds the translational repressor Bruno and is implicated in regulation of oskar mRNA translation

The product of the oskar gene directs posterior patterning in the Drosophil a oocyte, where it must be deployed specifically at the posterior pole. Pro per expression relies on the coordinated localization and translational con trol of the oskar mRNA. Translational repression prior to localization of t he transcript is mediated, in part, by the Bruno protein, which binds to di screte sites in the 3 ' untranslated region of the oskar mRNA, To begin to understand how Bruno acts in translational repression, we performed a yeast two-hybrid screen to identify Bruno-interacting proteins. One interactor, described here, is the product of the apontic gene. Coimmunoprecipitation e xperiments lend biochemical support to the idea that Bruno and Apontic prot eins physically interact in Drosophila, Genetic experiments using mutants d efective in apontic and bruno reveal a functional interaction between these genes. Given this interaction, Apontic is likely to act together with Brun o in translational repression of oskar mRNA, Interestingly, Apontic, like B runo, is an RNA-binding protein and specifically binds certain regions of t he oskar mRNA 3' untranslated region.