Protein products of nonstop mRNA disrupt nucleolar homeostasis

Cell Stress Chaperones. 2021 May;26(3):549-561. doi: 10.1007/s12192-021-01200-w. Epub 2021 Feb 22.

Abstract

Stalled mRNA translation results in the production of incompletely synthesized proteins that are targeted for degradation by ribosome-associated quality control (RQC). Here we investigated the fate of defective proteins translated from stall-inducing, nonstop mRNA that escape ubiquitylation by the RQC protein LTN1. We found that nonstop protein products accumulated in nucleoli and this localization was driven by polylysine tracts produced by translation of the poly(A) tails of nonstop mRNA. Nucleolar sequestration increased the solubility of invading proteins but disrupted nucleoli, altering their dynamics, morphology, and resistance to stress in cell culture and intact flies. Our work elucidates how stalled translation may affect distal cellular processes and may inform studies on the pathology of diseases caused by failures in RQC and characterized by nucleolar stress.

Keywords: LTN1; Nonstop mRNA; Nucleolus; Phase separation; Protein quality control; Ribosome-associated quality control (RQC).

Publication types

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

MeSH terms

  • Homeostasis / physiology*
  • Humans
  • Protein Biosynthesis / physiology
  • RNA, Messenger / metabolism*
  • Ribosomes / genetics
  • Ribosomes / metabolism*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination / physiology

Substances

  • RNA, Messenger
  • Saccharomyces cerevisiae Proteins
  • Ubiquitin-Protein Ligases