The G3BP1-Family-USP10 Deubiquitinase Complex Rescues Ubiquitinated 40S Subunits of Ribosomes Stalled in Translation from Lysosomal Degradation

Ribosome-associated quality control (RQC) purges aberrant mRNAs and nascent polypeptides in a multi-step molecular process initiated by the E3 ligase ZNF598 through sensing of ribosomes collided at aberrant mRNAs and monoubiquitination of distinct small ribosomal subunit proteins. We show that G3BP1-family-USP10 complexes are required for deubiquitination of RPS2, RPS3, and RPS10 to rescue modified 40S subunits from programmed degradation. Knockout of USP10 or G3BP1 family proteins increased lysosomal ribosomal degradation and perturbed ribosomal subunit stoichiometry, both of which were rescued by a single K214R substitution of RPS3. While the majority of RPS2 and RPS3 monoubiquitination resulted from ZNF598-dependent sensing of ribosome collisions initiating RQC, another minor pathway contributed to their monoubiquitination. G3BP1 family proteins have long been considered RNA-binding proteins, however, our results identified 40S subunits and associated mRNAs as their predominant targets, a feature shared by stress granules to which G3BP1 family proteins localize under stress. [Display omitted] •G3BP1-family-USP10 complexes crosslink mRNA coding sequences and 18S rRNA•USP10 deubiquitinates site-specifically monoubiquitinated RPS2, RPS3, and RPS10•Deubiquitination of 40S ribosomal proteins prevents 40S lysosomal degradation•Sensing of ribosome collision is responsible for the majority of 40S ubiquitination Translation of aberrant mRNAs causes ribosome collisions and triggers monoubiquitination of 40S ribosomal proteins located near the mRNA entry channel. Meyer et al. show that complexes composed of the RNA-binding proteins of the G3BP1 family and the deubiquitinase USP10 counteract the otherwise programmed lysosomal degradation of these modified 40S subunits.