The transcriptional response to oxidative stress is independent of stress-granule formation

Abstract

Cells respond to stress with translational arrest, robust transcriptional changes, and transcription-independent formation of mRNP assemblies termed stress granules (SGs). Despite considerable interest in the role of SGs in oxidative, unfolded-protein and viral stress responses, whether and how SGs contribute to stress-induced transcription has not been rigorously examined. To address this, we characterized transcriptional changes in Drosophila S2 cells induced by acute oxidative-stress and assessed how these were altered under conditions that disrupted SG assembly. Oxidative stress for 3-hours predominantly resulted in induction or upregulation of stress-responsive mRNAs whose levels peaked during recovery after stress cessation. The stress-transcriptome is enriched in mRNAs coding for chaperones, including HSP70s, small heat shock proteins, glutathione transferases, and several non-coding RNAs. Oxidative stress also induced cytoplasmic SGs that disassembled 3-hours after stress cessation. As expected, RNAi-mediated knockdown of the conserved G3BP1/Rasputin protein inhibited SG assembly. However, this disruption had no significant effect on the stress-induced transcriptional response or stress-induced translational arrest. Thus, SG assembly and stress-induced gene expression alterations appear to be driven by distinctive signaling processes. We suggest that while SG assembly represents a fast, transient mechanism, the transcriptional response enables a slower, longer-lasting mechanism for adaptation to and recovery from cell stress.

Identification of the stress granule transcriptome via RNA-editing in single cells and in vivo

“…However, translation initiation of the RNAs stored in stress granules has been shown not to be required for growth, as translation can resume before stress granule clearance is complete ( Loschi et al., 2009 ; Walters et al., 2015 ). Furthermore, a recent study suggests that the mRNAs that are upregulated upon oxidative stress are vastly excluded from stress granules ( Singh et al., 2021 ), strengthening the notion that stress granules might not be needed to protect RNA from degradation, but simply store them. Last, contrary to the finding that stress granules do not contain fully assembled ribosomes (only 40S) ( Kedersha et al., 1999 ; Anderson and Kedersha, 2002 ), single-molecule imaging has revealed that the translation machinery can be activated in stress granules ( Mateju et al., 2020 ).…”

Genomic Profiling of Insecticide Resistance in Malaria Vectors: Insights into Molecular Mechanisms.

“…Amongst them is Rootletin, which is known to play a role in behavioural response in Drosophila [ 64 ] and was previously linked to resistance as a key hub in response to insecticide exposure [ 45 ], whilst Grau has been linked to pyrethroid resistance in Aedes populations [ 65 ]. Other transcription factors enriched in insecticide resistance-related terms that are consistent with known roles in Drosophila includes Cabut, which has been shown to regulate stress response [ 66 ], E(spl)m3-HLH which is linked with stress granules [ 67 ], Grh that is involved in cuticular repair [ 68 ], Exex is involved in neuronal function [ 69 ], Onecut with synapse organisation [ 70 ] and Tfam is a mitochondrial transcription factor, with a role in oxidative stress response [ 71 ].…”

Reorganization of Cell Compartmentalization Induced by Stress

“…A systematic analysis was shown that perturbations of at least 128 genes cause nucleolar enlargement with subsequent formation of stress granules, an increase in the number of Cajal bodies, and splicing speckles in mammalian cells [ 214 ]. In addition, this work established a correlation between an increase in the nucleolus and a decrease in P-bodies, wherein no relationship was found between changes in gene expression and the formation of cytoplasmic stress granules [ 215 ].…”