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Nat Struct Mol Biol. 2017 Nov;24(11):944-953. doi: 10.1038/nsmb.3472. Epub 2017 Sep 25.

The complete structure of the small-subunit processome.

Author information

1
Laboratory of Protein and Nucleic Acid Chemistry, The Rockefeller University, New York, New York, USA.
2
Tri-Institutional Training Program in Chemical Biology, The Rockefeller University, New York, New York, USA.
3
Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, New York, USA.

Abstract

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 Å, 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.

PMID:
28945246
DOI:
10.1038/nsmb.3472
[Indexed for MEDLINE]

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