biostudies-literatureLeesch FAustrian Science Fund FWFSwiss National Science FoundationWellcome Trust712-720https://www.ebi.ac.uk/biostudies/studies/S-EPMC7614339biostudies-literatureUnknown613(7945)Ribosomes are produced in large quantities during oogenesis and are stored in the egg. However, the egg and early embryo are translationally repressed^1-4. Here, using mass spectrometry and cryo-electron microscopy analyses of ribosomes isolated from zebrafish (Danio rerio) and Xenopus laevis eggs and embryos, we provide molecular evidence that ribosomes transition from a dormant state to an active state during the first hours of embryogenesis. Dormant ribosomes are associated with four conserved factors that form two modules, consisting of Habp4-eEF2 and death associated protein 1b (Dap1b) or Dap in complex with eIF5a. Both modules occupy functionally important sites and act together to stabilize ribosomes and repress translation. Dap1b (also known as Dapl1 in mammals) is a newlNatureA molecular network of conserved factors keeps ribosomes dormant in the egg.PMC7614339Y 1031-B28191204EM BI25222Y 1031Lorenzo-Orts LMechtler KMatzinger MKandolf SHaselbach DGrishkovskaya IBelacic KLeesch FPauli AChugunova APribitzer CRoitinger EMeinhart ARoehsner JLin TYfalseA molecular network of conserved factors keeps ribosomes dormant in the egg.Ribosomes are produced in large quantities during oogenesis and are stored in the egg. However, the egg and early embryo are translationally repressed^1-4. Here, using mass spectrometry and cryo-electron microscopy analyses of ribosomes isolated from zebrafish (Danio rerio) and Xenopus laevis eggs and embryos, we provide molecular evidence that ribosomes transition from a dormant state to an active state during the first hours of embryogenesis. Dormant ribosomes are associated with four conserved factors that form two modules, consisting of Habp4-eEF2 and death associated protein 1b (Dap1b) or Dap in complex with eIF5a. Both modules occupy functionally important sites and act together to stabilize ribosomes and repress translation. Dap1b (also known as Dapl1 in mammals) is a newl2023-01-01T00:00:00Z2023 Jan2026-05-29T02:17:55.308Z2025-02-19T02:22:42.783ZS-EPMC76143393665345110.1038/s41586-022-05623-y