ABSTRACT
Regulated recruitment and activity of motor proteins is essential for intracellular transport of cargoes, including messenger ribonucleoprotein complexes (RNPs). Here we show that orchestration of oskar RNP transport in the Drosophila germline relies on the interplay of two double-stranded RNA binding proteins, Staufen and the dynein adaptor Egalitarian (Egl). We find that Staufen antagonizes Egl-mediated transport of oskar mRNA by dynein both in vitro and in vivo. Following delivery of nurse cell-synthesized oskar mRNA into the oocyte by dynein, recruitment of Staufen to the RNPs results in dissociation of Egl and a switch to kinesin-1-mediated translocation of the mRNA to its final destination at the posterior pole of the oocyte. We additionally show that Egl associates with staufen (stau) mRNA in the nurse cells, mediating its enrichment and translation in the ooplasm. Our observations identify a novel feed-forward mechanism, whereby dynein-dependent accumulation of stau mRNA, and thus protein, in the oocyte enables motor switching on oskar RNPs by downregulating dynein activity.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Section 'Staufen suppresses minus...' updated with motility data stratified by relative RNA content and section 'Staufen antagonizes dynein...' updated with analysis of RNA independent dynein motility to clarify the effect of Staufen on dynein-mediated (RNP) transport. Section 'Staufen activity is controlled by Egl...' updated with analysis of endogenous Staufen/stau localization and analysis of GFP-Staufen overexpression to provide further evidence on the importance of stau RNA localization. Discussion is updated to improve clarity. All figures are updated to include the new findings and/or improve clarity.
