Structure of a eukaryotic cytoplasmic pre-40S ribosomal subunit

Final maturation of eukaryotic ribosomes occurs in the cytoplasm and requires the sequential removal of associated assembly factors and processing of the immature 20S pre-RNA. Using cryo-electron microscopy (cryo-EM), we have determined the structure of a yeast cytoplasmic pre-40S particle in complex with Enp1, Ltv1, Rio2, Tsr1, and Pno1 assembly factors poised to initiate final maturation. The structure reveals that the pre-rRNA adopts a highly distorted conformation of its 3' major and 3' minor domains stabilized by the binding of the assembly factors. This observation is consistent with a mechanism that involves concerted release of the assembly factors orchestrated by the folding of the rRNA in the head of the pre-40S subunit during the final stages of maturation. Our results provide a structural framework for the coordination of the final maturation events that drive a pre-40S particle toward the mature form capable of engaging in translation.

Source: EMBO Journal - April 3, 2018 Category: Molecular Biology Authors: Scaiola, A., Pena, C., Weisser, M., Böhringer, D., Leibundgut, M., Klingauf-Nerurkar, P., Gerhardy, S., Panse, V. G., Ban, N. Tags: Protein Biosynthesis & Quality Control, RNA Biology, Structural Biology Articles Source Type: research