1. Academic Validation
  2. An E3 ligase network engages GCN1 to promote the degradation of translation factors on stalled ribosomes

An E3 ligase network engages GCN1 to promote the degradation of translation factors on stalled ribosomes

  • Cell. 2023 Jan 5;S0092-8674(22)01538-0. doi: 10.1016/j.cell.2022.12.025.
Keely Oltion 1 Jordan D Carelli 1 Tangpo Yang 2 Stephanie K See 1 Hao-Yuan Wang 2 Martin Kampmann 3 Jack Taunton 4
Affiliations

Affiliations

  • 1 Chemistry and Chemical Biology Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA.
  • 2 Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA.
  • 3 Institute for Neurodegenerative Diseases, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA.
  • 4 Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA. Electronic address: [email protected]
Abstract

Ribosomes frequently stall during mRNA translation, resulting in the context-dependent activation of quality control pathways to maintain proteostasis. However, surveillance mechanisms that specifically respond to stalled ribosomes with an occluded A site have not been identified. We discovered that the elongation factor-1α (eEF1A) inhibitor, ternatin-4, triggers the ubiquitination and degradation of eEF1A on stalled ribosomes. Using a chemical genetic approach, we unveiled a signaling network comprising two E3 Ligases, RNF14 and RNF25, which are required for eEF1A degradation. Quantitative proteomics revealed the RNF14 and RNF25-dependent ubiquitination of eEF1A and a discrete set of ribosomal proteins. The ribosome collision sensor GCN1 plays an essential role by engaging RNF14, which directly ubiquitinates eEF1A. The site-specific, RNF25-dependent ubiquitination of the ribosomal protein RPS27A/eS31 provides a second essential signaling input. Our findings illuminate a ubiquitin signaling network that monitors the ribosomal A site and promotes the degradation of stalled translation factors, including eEF1A and the termination factor eRF1.

Keywords

CRISPRi screen; E3 ligase; K6-linked ubiquitin; RWD domain; diGly proteomics; natural product; protein synthesis; ribosomal ubiquitination; ribosome quality control; translation factor.

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