The G3BP Stress-Granule Proteins Reinforce the Translation Program of the Integrated Stress Response
When mammalian cells are exposed to extracellular stress, they coordinate the condensation of stress granules (SGs) through the action of key nucleating proteins G3BP1 and G3BP2 (G3BPs) and, simultaneously, undergo a massive reduction in translation. Although SGs and G3BPs have been linked to this translation response, their overall impact has been unclear. Here, we investigate the longstanding question of how, and indeed whether, G3BPs and SGs shape the stress translation response. We find that SGs are enriched for mRNAs that are resistant to the stress-induced translation shutdown. Although the accurate recruitment of these stress-resistant mRNAs does require the context of stress, a combination of optogenetic tools and spike-normalized ribosome profiling demonstrates that G3BPs and SGs are necessary and sufficient to both help prioritize the translation of their enriched mRNAs and help suppress cytosolic translation. Together these results support a model in which G3BPs and SGs reinforce the stress translation program by prioritizing the translation of their resident mRNAs. Overall design: Ribo-seq and RNA-seq were performed on replicate samples from HCT116 cells treated with 500 uM sodium arsenite for 1 hour, heat shocked at 45C for 25 min, depleted of their endogenous G3BPs using Auxin induced degrons, or that had  SGs, OGs, or SOGs, purified from them and were subsequently sequeneced.