Funding Organization(s): National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS), European Molecular Biology Organization (EMBO), Swiss National Science Foundation, Natural Sciences and Engineering Research Council (NSERC, Canada), Human Frontier Science Program (HFSP)
The small-subunit processome represents the earliest stable precursor of the eukaryotic small ribosomal subunit. Here we present the cryo-EM structure of the Saccharomyces cerevisiae small-subunit processome at an overall resolution of 3.8 ?, which provides an essentially complete near-atomic model of this assembly. In this nucleolar superstructure, 51 ribosome-assembly factors and two RNAs encapsulate the 18S rRNA precursor and 15 ribosomal proteins in a state that precedes pre-rRNA cleavage at site A1. Extended flexible proteins are employed to connect distant sites in this particle. Molecular mimicry and steric hindrance, as well as protein- and RNA-mediated RNA remodeling, are used in a concerted fashion to prevent the premature formation of the central pseudoknot and its surrounding elements within the small ribosomal subunit.
Organizational Affiliation:
Laboratory of Protein and Nucleic Acid Chemistry, The Rockefeller University, New York, New York, USA.
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