Poster abstracts
Poster number 61 submitted by Noah Helton
Ribosome association excludes stress-induced gene mRNAs from stress granules
Noah S. Helton (Department of Human Genetics, University of Michigan ), Ben Dodd (Department of Human Genetics, University of Michigan ), Stephanie Moon (Department of Human Genetics, University of Michigan )
Abstract:
Cells respond to stress via the integrated stress response (ISR), which causes translation suppression, stress-induced gene expression, and assembly of biomolecular condensates called stress granules. Despite the temporal connection between stress-induced gene expression and stress granules, little is known about how these two ISR branches interface. No direct, quantitative, and mechanistic analysis of the relationship between stress-induced gene mRNAs and stress granules has been performed. Stress granules sequester non-translating mRNAs away from the translation machinery and stress-induced genes evade translational suppression via mechanisms including upstream open reading frames (uORFs). These genes include the transcription factor ATF4 and the translation depressor GADD34, which are crucial for remodeling gene expression in response to stress. Therefore, we hypothesized that stress-induced gene mRNAs would be excluded from stress granules to enable their expression. Using a panel of small-molecule translation inhibitors and single-molecule imaging, our data reveal that the translationally upregulated mRNAs, ATF4 and GADD34, are excluded from stress granules in part by their association with one or more ribosomes. This suggests a role for uORFs in preventing mRNA condensation during stress. Further, we show that trapping a single ribosome on mRNAs is sufficient to inhibit stress granule formation, supporting that translation complexes prevent mRNA assembly into stress granules independently of ribosomal translocation or occupancy across the open reading frame. We also observed reduced ATF4 and GADD34 expression and cellular resilience to stress in a stress granule deficient G3BP1/2 knock-out cell line. Together, we provide evidence that the major stress-induced genes that reprogram gene expression evade stress granule sequestration through ribosome association and G3BP1/2 promote their expression during the recovery from stress.
Keywords: Translation, Stress Granules, Integrated stress response