New Roles for Igf-II mRNA-binding Protein During Early Drosophila Development

Abstract

The coupling of mRNA localization and translational control is an effective means of establishing spatiotemporal control over gene expression. These controls are established through the combined action of cis-acting elements within the transcript, trans-acting factors that bind them, and the factors that are subsequently recruited to the transcript. Together, the full complement of regulatory elements determines where and when the target mRNA will be translated into protein. A powerful model for the study of mRNA localization and translational control is the tight control of nanos (nos) mRNA during early Drosophila development. Translation of nos mRNA must be restricted to the embryo posterior, and defects in nos localization and translational control significantly impact the formation of the anterior-posterior axis. This thesis presents the identification of novel cis-acting elements and trans-acting factors in translational regulation of nos; in particular, elements in the distal nos 3' untranslated region and Igf-II mRNA-binding protein (Imp). Additionally, this thesis describes the analysis of Imp function in post-transcriptional regulation of oskar (osk), another developmentally important mRNA that functions in germ cell formation and acts upstream of nos in anterior-posterior axis development. Together, these newly identified roles for Imp provide a foundation for future studies aimed at gaining further insight into the regulation of nos and osk, how multiple post-transcriptional regulatory mechanisms are layered to regulate a given transcript, and how one protein regulates multiple transcripts.