Oskar

oskar is a gene required for the development of the Drosophila embryo. It defines the posterior pole during early embryogenesis.

oskar is translationally repressed prior to reaching the posterior pole of the oocyte by Bruno, which binds to three bruno response elements (BREs) on the 3' end of the transcribed oskar mRNA. The Bruno inhibitor has two distinct modes of action: recruiting the Cup eIF4E binding protein, which is also required for oskar mRNA localization due to interactions with the Barentsz microtubule-linked transporter, and promoting oligomerization of oskar mRNA. Oskar mRNA harbours a stem-loop structure in the 3’UTR, called the oocyte entry signal (OES), that promotes dynein-based mRNA accumulation in the oocyte.