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Mol Cell. 2018 Dec 20;72(6):1013-1020.e6. doi: 10.1016/j.molcel.2018.11.023.

Decoding the Function of Expansion Segments in Ribosomes.

Author information

1
Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA.
2
Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA.
3
Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA. Electronic address: mbarna@stanford.edu.

Abstract

Expansion segments (ESs) are enigmatic insertions within the eukaryotic ribosome, the longest of which resemble tentacle-like extensions that vary in length and sequence across evolution, with a largely unknown function. By selectively engineering rRNA in yeast, we find that one of the largest ESs, ES27L, has an unexpected function in translation fidelity. Ribosomes harboring a deletion in the distal portion of ES27L have increased amino acid misincorporation, as well as readthrough and frameshifting errors. By employing quantitative mass spectrometry, we further find that ES27L acts as an RNA scaffold to facilitate binding of a conserved enzyme, methionine amino peptidase (MetAP). We show that MetAP unexpectedly controls the accuracy of ribosome decoding, which is coupled to an increase in its enzymatic function through its interaction with ES27L. These findings reveal that variable ESs of the ribosome serve important functional roles and act as platforms for the binding of proteins that modulate translation across evolution.

KEYWORDS:

ES; ES27L; MetAP; expansion segment; methionine amino peptidase; rRNA; ribosome; translation fidelity

PMID:
30576652
PMCID:
PMC6407129
DOI:
10.1016/j.molcel.2018.11.023
[Indexed for MEDLINE]
Free PMC Article

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