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Direct observation of translational activation by a ribonucleoprotein granule

Affiliations
  • 1Whitehead Institute for Biomedical Research, Cambridge, MA, USA.
  • 2Vilcek Institute of Graduate Studies, NYU School of Medicine, New York, NY, USA.
  • 3Immunobiology Laboratory, The Francis Crick Institute, London, UK.
  • 4Institut de Génétique Moléculaire de Montpellier, University of Montpellier, Montpellier, France.
  • 5Institut de Recherche en Infectiologie de Montpellier, University of Montpellier, Montpellier, France.
  • 6Whitehead Institute for Biomedical Research, Cambridge, MA, USA. lehmann@wi.mit.edu.
  • 7Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA. lehmann@wi.mit.edu.

Published on:

July 4, 2024

Abstract

Biomolecular condensates organize biochemical processes at the subcellular level and can provide spatiotemporal regulation within a cell. Among these, ribonucleoprotein (RNP) granules are storage hubs for translationally repressed mRNA. Whether RNP granules can also activate translation and how this could be achieved remains unclear. Here, using single-molecule imaging, we demonstrate that the germ cell-determining RNP granules in Drosophila embryos are sites for active translation of nanos mRNA. Nanos translation occurs preferentially at the germ granule surface with the 3′ UTR buried within the granule. Smaug, a cytosolic RNA-binding protein, represses nanos translation, which is relieved when Smaug is sequestered to the germ granule by the scaffold protein Oskar. Together, our findings uncover a molecular process by which RNP granules achieve localized protein synthesis through the compartmentalized loss of translational repression.

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