Posttransscriptional regulation of the nanos mRNA in Drosophila melanogaster

The Drosophila nanos mRNA encodes the posterior determinant of embryonic development. Translation of the RNA is allowed only at the posterior pole of the embryo and is repressed elsewhere by the protein Smaug. Smaug also induces deadenylation by the CCR4-NOT complex. We have reproduced both deadenylation and translational repression in extracts of Drosophila embryos. The deadenylation activity, which is associated with rapidly sedimenting particles, depends on the Smaug binding sites in the RNA and on an ATP-regenerating system. Micrococcal nuclease inhibits the reaction. Translational repression is also Smaug- and ATP-dependent and relies on the time-dependent assembly of a stable repressor complex. Translation is blocked at the earliest detectable step. The proposal aims to identify the factors responsible for deadenylation and translational repression by an affinity purification approach with the goal of analyzing the mechanisms involved.