Research Article

Architecture of the yeast small subunit processome

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Science  15 Dec 2016:
aal1880
DOI: 10.1126/science.aal1880

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Abstract

The small subunit (SSU) processome, a large ribonucleoprotein particle, organizes the assembly of the eukaryotic small ribosomal subunit by coordinating the folding, cleavage and modification of nascent pre-rRNA. Here, we present the cryo-EM structure of the yeast SSU processome at 5.1 Å resolution. The structure reveals how large ribosome biogenesis complexes assist the 5′ external transcribed spacer and U3 snoRNA in providing an intertwined RNA-protein assembly platform for the separate maturation of 18S rRNA domains. The strategic placement of a molecular motor at the center of the particle further suggests a mechanism for mediating conformational changes within this giant particle. This study provides a structural framework for a mechanistic understanding of eukaryotic ribosome assembly in the model organism Saccharomyces cerevisiae.

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