Stress granule condensation (SGC) of translationally arrested mRNAs requires G3BP, and G3BP-mediated SGC is inhibited by serine 149 phosphorylation, regulated by mutually exclusive binding of Caprin1 and USP10, and requires its RGG region for SGC and for interactions with 40S ribosomal subunits.

Highlights d Stress granule formation requires RNA-binding nodes with high network connectivity d Capping of nodes by ligands lacking connectivity prevents condensation d Protein disorder and RNA-binding specificity play nonessential, modulatory roles d Competition of RNP networks for connecting nodes controls multiphase organization

Cells have developed different mechanisms to respond to stress, including the formation of cytoplasmic foci known as stress granules (SGs). SGs are dynamic and formed as a result of stress-induced inhibition of translation. Despite enormous interest in SGs due to their contribution to the pathogenesis of several human diseases, many aspects of SG formation are poorly understood. SGs induced by different stresses are generally assumed to be uniform, although some studies suggest that different SG subtypes and SG-like cytoplasmic foci exist. Here, we investigated the molecular mechanisms of SG assembly and characterized their composition when induced by various stresses. Our data revealed stress-specific differences in composition, assembly and dynamics of SGs and SGlike cytoplasmic foci. Using a set of genetically modified haploid human cells, we determined the molecular circuitry of stress-specific translation inhibition upstream of SG formation and its relation to cell survival. Finally, our studies characterize cytoplasmic stress-induced foci related to, but distinct from, canonical SGs, and also introduce haploid cells as a valuable resource to study RNA granules and translation control mechanisms.