UV damage induces G3BP1-dependent stress granule formation that is not driven by translation arrest via mTOR inhibition

Abstract

Translation arrest is a part of the cellular stress response that decreases energy consumption and enables rapid reprioritisation of gene expression. Often translation arrest leads to condensation of untranslated messenger ribonucleoproteins (mRNPs) into stress granules (SGs). Studies into mechanisms of SG formation and functions are complicated because various types of stress cause formation of SGs with different properties and composition. In this work we focused on the mechanism of SG formation triggered by UV damage. We demonstrate that UV-induced inhibition of translation does not cause dissociation of the 48S preinitiation complexes. The catalytic activity of the general control non-derepressible 2 (GCN2) kinase contributes to UV-induced SG formation, which is independent of the GCN2-mediated phosphorylation of the eukaryotic translation initiation factor 2. Like many other types of SGs, condensation of UV-induced granules specifically requires the Ras-GTPase-Activating Protein SH3-Domain-Binding Protein 1 (G3BP1). Our work reveals that in UV-treated cells the mechanisms of translation arrest and SG formation may be unlinked, resulting in condensation of ribonucleoproteins that do not represent the major type of polysome-free preinitiation complexes that accumulate in the cytoplasm.