Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 1, 2016 | Published + Supplemental Material
Journal Article Open

Ribosomal proteins produced in excess are degraded by the ubiquitin-proteasome system


Ribosome assembly is an essential process that consumes prodigious quantities of cellular resources. Ribosomal proteins cannot be overproduced in Saccharomyces cerevisiae because the excess proteins are rapidly degraded. However, the responsible quality-control (QC) mechanisms remain poorly characterized. Here, we demonstrate that overexpression of multiple proteins of the small and large yeast ribosomal subunits is suppressed. Rpl26 overexpressed from a plasmid can be detected in the nucleolus and nucleoplasm, but it largely fails to assemble into ribosomes and is rapidly degraded. However, if the endogenous RPL26 loci are deleted, plasmid-encoded Rpl26 assembles into ribosomes and localizes to the cytosol. Chemical and genetic perturbation studies indicate that overexpressed ribosomal proteins are degraded by the ubiquitin-proteasome system, and not by autophagy. Inhibition of the proteasome led to accumulation of multiple endogenous ribosomal proteins in insoluble aggregates, consistent with the operation of this QC mechanism in the absence of ribosomal protein overexpression. Our studies reveal that ribosomal proteins that fail to assemble into ribosomes are rapidly distinguished from their assembled counterparts and are ubiquitinated and degraded within the nuclear compartment.

Additional Information

© 2016 Sung et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0). Submitted May 10, 2016; Revised June 24, 2016; Accepted June 30, 2016; Published online before print July 6, 2016. We are grateful to members of the Deshaies' laboratory for helpful advice and Rati Verma for critical reading of this manuscript and numerous helpful suggestions regarding biochemical experiments. We thank Jonathan Warner for generously providing reagents and helpful discussions. This work was supported by the Gordon and Betty Moore Foundation, through Grant GBMF775 and the Beckman Institute (to S.H.) and NIH Grant F32 GM112308 (to J.R.). R.J.D. is an Investigator of the HHMI and this work was supported by HHMI.

Attached Files

Published - Mol._Biol._Cell-2016-Sung-2642-52.pdf

Supplemental Material - CombinedSupMats.pdf

Supplemental Material - mc-E16-05-0290-s06.xlsx

Supplemental Material - mc-E16-05-0290-s07.xlsx


Files (5.2 MB)
Name Size Download all
2.4 MB Preview Download
2.7 MB Preview Download
206.6 kB Download
16.6 kB Download

Additional details

August 20, 2023
October 20, 2023