mRNP assembly and remodeling for transport and translational control in Drosophila

• Applicant: Dr. Anne Ephrussi, Ph.D.
• Subject Area: General Genetics and Functional Genome Biology ; Biochemistry ; Developmental Biology ; Cell Biology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270067186

Cytoplasmic mRNA localization is a powerful and conserved mechanism for achieving localized protein expression in eukaryotic cells; it is prevalent in Drosophila, whose oocyte-localized transcripts encoding embryonic axis determinants have become models for the study of mRNA transport, local translation and anchoring. With its highly developed tools for experimental analysis, Drosophila is an ideal model system for biochemical, genetic and cell biological investigation of mRNA localization mechanisms as they occur in vivo. A paradigm is Drosophila oskar mRNA, whose localization is a multi-step process that includes: (1) nuclear splicing-dependent generation of a bipartite localization signal within the oskar mRNA coding region and (2) concomitant, splicing dependent deposition of the Exon Junction Complex (EJC) on the mRNA; (3) cytoplasmic recruitment of proteins required for (4) microtubule motor-dependent transport of oskar messenger ribonucleoproteins (mRNPs) from the nurse cells into the oocyte by the microtubule motor, dynein and to the posterior pole by kinesin-1; (5) translational repression of the mRNA in transport and (6) localized translational activation of oskar mRNA at the oocyte posterior, which is required for the (7) Oskar protein dependent mRNA anchoring at the posterior pole. While (mainly) genetics has led to the identification of a few of the proteins involved in this complex regulation, neither is the full complement of proteins known, nor are how and when they (inter)act in the process understood. As a first aim of our project, we plan to address the broader role of the Drosophila EJC in mRNA localization in the fly and to understand cellular events and molecular features that determine its stable and selective binding to specific sites on mRNAs. The second aim of the project is to develop and apply a method for transcript- and translational status-specific purification of intracellular transport mRNPs in Drosophila. As a proof of principle, we will use oskar mRNA, then extend to other Drosophila localized mRNAs towards a systemic view of localization mRNP composition and its functional analysis in vivo in the fly.

• DFG Programme: Research Units
• Subproject of: FOR 2333: Macromolecular Complexes in mRNA translocation