Abstract
ABSTRACTWhen exposed to stressful conditions, eukaryotic cells respond by inducing the formation of cytoplasmic ribonucleoprotein complexes called stress granules. Here, we use C. elegans to study two proteins that are important for stress granule assembly in human cells – PQN-59, the human UBAP2L ortholog, and GTBP-1, the human G3BP1 and G3BP2 ortholog. Both proteins assemble into stress granules in the embryo and in the germline when C. elegans is exposed to stressful conditions. Neither of the two proteins is essential for the assembly of stress-induced granules, as shown by the single and combined depletions by RNAi, and neither pqn-59 nor gtbp-1 mutant embryos show higher sensitivity to stress than control embryos. We find that pqn-59 mutants display reduced progeny and a high percentage of embryonic lethality, phenotypes that are not dependent on stress exposure and that are not shared with gtbp-1 mutants. Our data indicate that, in contrast to human cells, PQN-59 and GTBP-1 are not required for stress granule formation but that PQN-59 is important for C. elegans development.
Highlights
Eukaryotic cells are sensitive to changes in internal or environmental parameters, including variations in oxygen supply, salt concentration, pH, temperature or viral infection
In contrast to what has been shown in human cells, we find that neither of the two proteins is essential for stress granule assembly in the embryo, but each contribute to the recruitment of the other to granules
Similar to stress granules in human cells (Wheeler et al, 2016), lowering the temperature to 20°C following heat-shock exposure resulted in dissolution of the PQN-59/GTBP-1 granules after about 10-15 minutes of recovery (Fig. 1C)
Summary
Eukaryotic cells are sensitive to changes in internal or environmental parameters, including variations in oxygen supply, salt concentration, pH, temperature or viral infection. Each one of these conditions might be sensed as a stressful stimulus by the cell. Different protein entities and RNA molecules are recruited into stress granules and their composition varies according to the cell type and the triggering stress (Aulas et al, 2017; Markmiller et al, 2018). The current model describing the pathway through which cells assemble stress granules involves disassembly of the polysomes with consequent translation inhibition either via phosphorylation of the translation initiation factor eIF2α
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