Lipid-mediated phase separation of AGO proteins on the ER controls nascent-peptide ubiquitination

Mol Cell. 2022 Apr 7;82(7):1313-1328.e8. doi: 10.1016/j.molcel.2022.02.035. Epub 2022 Mar 23.

Abstract

AGO/miRNA-mediated gene silencing and ubiquitin-mediated protein quality control represent two fundamental mechanisms that control proper gene expression. Here, we unexpectedly discover that fly and human AGO proteins, which are key components in the miRNA pathway, undergo lipid-mediated phase separation and condense into RNP granules on the endoplasmic reticulum (ER) membrane to control protein production. Phase separation on the ER is mediated by electrostatic interactions between a conserved lipid-binding motif within the AGOs and the lipid PI(4,5)P2. The ER-localized AGO condensates recruit the E3 ubiquitin ligase Ltn1 to catalyze nascent-peptide ubiquitination and coordinate with the VCP-Ufd1-Npl4 complex to process unwanted protein products for proteasomal degradation. Collectively, our study provides insight into the understanding of post-transcription-translation coupling controlled by AGOs via lipid-mediated phase separation.

Keywords: AGO1; Drosophila; ER; lipid binding; nascent peptide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Lipids
  • MicroRNAs* / metabolism
  • Peptides / metabolism
  • Ubiquitin-Protein Ligases* / genetics
  • Ubiquitin-Protein Ligases* / metabolism
  • Ubiquitination

Substances

  • Lipids
  • MicroRNAs
  • Peptides
  • Ubiquitin-Protein Ligases