Resolving Late-Stage Intermediates of Eukaryotic Ribosome Assembly

The assembly of eukaryotic ribosomes requires about 200 assembly factors promoting RNA modification, folding, cleavage, and ribosomal protein association. In this issue of Structure , Johnson et al. (2017) report structures of several late-stage intermediates of pre-40S ribosomal subunit assembly. This work provides detailed testable insights into assembly factor function.