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Ubiquitin release from eL 40 is required for cytoplasmic maturation and function of 60S ribosomal subunits in Saccharomyces cerevisiae
Author(s) -
MartínVillanueva Sara,
FernándezPevida Antonio,
FernándezFernández José,
Kressler Dieter,
de la Cruz Jesús
Publication year - 2020
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.14999
Subject(s) - saccharomyces cerevisiae , ubiquitin , cytoplasm , function (biology) , ribosomal rna , yeast , chemistry , ribosomal protein , microbiology and biotechnology , biochemistry , biology , gene , ribosome , rna
Ubiquitin is generated by proteolytic cleavage of precursor proteins in which it is fused either to itself, constituting a linear polyubiquitin protein of head‐to‐tail monomers, or as a single N‐terminal moiety to one of two ribosomal proteins, eL 40 (Ubi1/2 precursors) and eS 31 (Ubi3 precursor). It has been proposed that the ubiquitin moiety fused to these ribosomal proteins could act as a chaperone by facilitating their efficient production, folding and ribosome assembly in Saccharomyces cerevisiae . We have previously shown that ubiquitin release from eS 31 is required for yeast viability and that noncleaved Ubi3 can get incorporated into translation‐competent 40S subunits. In this study, we have analysed the effects of mutations that partially or totally impair cleavage of the ubiquitin‐ eL 40A fusion protein. While noncleaved Ubi1 is not able to support growth when it is the sole cellular source of eL 40, it can assemble into nascent pre‐60S particles. However, Ubi1‐containing 60S ribosomal subunits are not competent for translation. This is likely due to a steric interference of the unprocessed ubiquitin with the binding and function of factors that interact with the ribosome's GTP ase‐associated centre. In agreement with this suggestion, Ubi1‐containing ribosomes affect the efficient recycling of the anti‐association factor Tif6 and have a reduced presence of translation elongation factors. We conclude that the removal of the ubiquitin moiety from ribosomal protein eL 40 is an essential prerequisite for both the cytoplasmic maturation and the functionality of 60S ribosomal subunits.