Eukaryotic ribosomes are assembled by a complex pathway that extends from the nucleolus to the cytoplasm and is powered by many energy-consuming enzymes 1-3. Nuclear export is a key, irreversible step in pre-ribosome maturation4-8, but mechanisms underlying the timely acquisition of export competence remain poorly understood. Here we show that a conserved GTPase Nug2/ Nog2 (called NGP-1, Gnl2 o...
