Aggregation of CAT Tails Blocks Their Degradation and Causes Proteotoxicity in S. Cerevisiae

PLoS One. 2020 Jan 16;15(1):e0227841. doi: 10.1371/journal.pone.0227841. eCollection 2020.


The Ribosome-associated Quality Control (RQC) pathway co-translationally marks incomplete polypeptides from stalled translation with two signals that trigger their proteasome-mediated degradation. The E3 ligase Ltn1 adds ubiquitin and Rqc2 directs the large ribosomal subunit to append carboxy-terminal alanine and threonine residues (CAT tails). When excessive amounts of incomplete polypeptides evade Ltn1, CAT-tailed proteins accumulate and can self-associate into aggregates. CAT tail aggregation has been hypothesized to either protect cells by sequestering potentially toxic incomplete polypeptides or harm cells by disrupting protein homeostasis. To distinguish between these possibilities, we modulated CAT tail aggregation in Saccharomyces cerevisiae with genetic and chemical tools to analyze CAT tails in aggregated and un-aggregated states. We found that enhancing CAT tail aggregation induces proteotoxic stress and antagonizes degradation of CAT-tailed proteins, while inhibiting aggregation reverses these effects. Our findings suggest that CAT tail aggregation harms RQC-compromised cells and that preventing aggregation can mitigate this toxicity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / genetics
  • DNA Polymerase III / genetics
  • Peptides / genetics*
  • Proteasome Endopeptidase Complex / genetics
  • Protein Biosynthesis*
  • Proteolysis
  • RNA, Transfer / genetics
  • RNA-Binding Proteins / genetics*
  • Ribosomes / genetics*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics*
  • Threonine / genetics
  • Ubiquitin / genetics
  • Ubiquitin-Protein Ligases / genetics*


  • Peptides
  • RNA-Binding Proteins
  • Saccharomyces cerevisiae Proteins
  • Tae2 protein, S cerevisiae
  • Ubiquitin
  • Threonine
  • RNA, Transfer
  • Ltn1 protein, S cerevisiae
  • Ubiquitin-Protein Ligases
  • DNA Polymerase III
  • Proteasome Endopeptidase Complex
  • Alanine