Meeting Abstract

99.6  Monday, Jan. 6 14:45  Understanding Translational Regulation Using the Model System Drosophila KANKE, MR*; MACDONALD, PM; University of Texas at Austin; University of Texas at Austin matthew.r.kanke@gmail.com

Translational regulation of localized RNAs is crucial for development across the animal kingdom. In the model system Drosophila, proper regulation of localized mRNAs is essential for patterning of the embryo and acts as an ideal model for the study of translational regulation. One of these localized RNAs, osk mRNA, is required for posterior patterning. osk is synthesized in the nurse cells and subsequently localized to the posterior of the oocyte in a translationally repressed state. Upon posterior localization, translation is initiated and osk is translated into two Osk isoforms, Long Osk and Short Osk. Repression has been extensively characterized and relies on defined elements in the osk 3’ UTR as well as known regulatory factors. Translational activation is less well understood. The current model proposes that a 5’ regulatory element, positioned in a protein coding region, acts to override repression specifically at the posterior pole of the oocyte. We have used an osk::GFP reporter to better characterize this 5’ element. Introduction of the inversion mutation used to define the 5’ element results in both lower protein level and loss of the Long Osk anchoring function, providing clear evidence of a protein defect. To determine if there was also an effect at the RNA level, we took advantage of the fact that Long Osk is not essential for Osk function. The proposed regulatory element is within the coding region unique to Long Osk. When the Long Osk start codon is mutated, now only Short Osk is made and any mutation in the proposed regulatory region only affects the RNA sequence, not the protein sequence. We find that indeed there is a translational activation element in the proposed region, and that this element is essential for Short Osk expression.