Stress-specific differences in assembly and composition of stress granules and related foci

Abstract

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.

Phospho-Rasputin Stabilization by Sec16 Is Required for Stress Granule Formation upon Amino Acid Starvation

“…Last, they were completely reversible upon 60 min of stress relief (addition of full medium) (Figures 1H and 1H’). This suggests that the stress granules that were formed by amino acid starvation were canonical, as they had the same properties as those formed upon other stresses (Aulas et al, 2017; Farny et al, 2009). …”

“…Stress granules are formed when protein translation initiation is inhibited by cellular stress that leads to elF2α phosphorylation and the accumulation of untranslated mRNAs (Anderson and Kedersha, 2006; Aulas et al, 2017; Kedersha et al, 2016). Stress granule components start to coalesce through protein-protein interactions mediated by proteins containing regions of low-complexity sequences and displaying multivalence interactions.…”

“…Stress granule formation is also driven by a number of critical factors, including G3BP. In all these respects, the cytoplasmic foci that are formed in Drosophila cells upon amino acid starvation and that are positive for RNA-binding proteins are bona fide stress granules, as they share many features of those found in mammalian cells after arsenite treatment, heat stress, and ER stress (Aulas et al, 2017). Furthermore, we show that Rin, the G3BP Drosophila ortholog, is an essential factor for amino acid starvation-driven stress granules.…”

ALS/FTD-Associated C9ORF72 Repeat RNA Promotes Phase Transitions In Vitro and in Cells

“…rG4C2-38X (38 repeats of the G4C2) induced granules decrease when treated with cycloheximide and increase when treated with puromycin (Fig 1E), consistent with these granules being in dynamic equilibrium with polysomes (Kedersha et al, 2000). The presence of SG markers and their dynamic behavior indicates rG4C2-induced foci can be classified as bona fide SGs (Aulas et al, 2017). Fluorescence recovery after photobleaching (FRAP) was employed to assess the dynamics of both the r(G4C2)4 and mCherry-tagged G3BP1.…”

Isolation of yeast and mammalian stress granule cores

“…In addition, some proteins which localize to stress granules contain intrinsically disordered regions (IDR) which could promote physical protein-protein interactions and contribute to stress granule assembly [5,7,8,9,10,11,13]. Stress granules are comprised of a dense network of physical interactions and stress granule composition can change in response to different stressors [1,4,6]. Therefore, a broader understanding of stress granule composition is likely provide insights into RNP granule formation and RNA regulation.…”