Translational regulation of oskar mRNA occurs independent of the cap and poly(A) tail in Drosophila ovarian extracts

Translational regulation plays a prominent role in Drosophila body patterni ng. Progress in elucidating the underlying mechanisms has been limited by t he lack of a homologous in vitro system that supports regulation. Here we s how that extracts prepared from Drosophila tissues are competent for transl ation. Ovarian extracts, but not embryonic extracts, support the Bruno resp onse element-and Bruno-dependent repression of oskar mRNA translation, whic h acts in vivo to prevent protein synthesis from transcripts not localized to the posterior pole of the oocyte. Consistent with suggestive evidence fr om in vivo experiments, regulation in vitro does not involve changes in pol y(A) tail length. Moreover, inhibition studies strongly suggest that repres sion does not interfere with the process of 5' cap recognition. Translation al regulation mediated through the Bruno response elements is thus likely t o occur via a novel mechanism.