Maintenance of p-eIF2 alpha levels by the eIF2B complex is vital for colorectal cancer
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ABSTRACT:
PROVIDER: PRJNA1047524 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR27012908.fastq.gz | Fastqsanger.gz | |||
| SRR27012909.fastq.gz | Fastqsanger.gz | |||
| SRR27012910.fastq.gz | Fastqsanger.gz | |||
| SRR27012911.fastq.gz | Fastqsanger.gz | |||
| SRR27012912.fastq.gz | Fastqsanger.gz |
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Project description:Various stressors such as viral infection lead to the suppression of cap-dependent translation and the activation of the integrated stress response (ISR), since the stress-induced phosphorylated eukaryotic translation initiation factor 2 [eIF2(αP)] tightly binds to eIF2B to prevent it from exchanging guanine nucleotide molecules on its substrate, unphosphorylated eIF2. Sandfly fever Sicilian virus (SFSV) evades this cap-dependent translation suppression through the interaction between its nonstructural protein NSs and host eIF2B. However, its precise mechanism has remained unclear. Here, our cryo-electron microscopy (cryo-EM) analysis revealed that SFSV NSs binds to the α-subunit of eIF2B in a competitive manner with eIF2(αP). Together with SFSV NSs, eIF2B retains nucleotide exchange activity even in the presence of eIF2(αP), in line with the cryo-EM structures of the eIF2B•SFSV NSs•unphosphorylated eIF2 complex. A genome-wide ribosome profiling analysis clarified that SFSV NSs expressed in cultured human cells attenuates the ISR triggered by thapsigargin, an endoplasmic reticulum stress inducer. Furthermore, SFSV NSs introduced in rat hippocampal neurons and human induced-pluripotent stem (iPS) cell-derived motor neurons exhibited neuroprotective effects against the ISR-inducing stress. Since ISR inhibition is beneficial in various neurological disease models, SFSV NSs is promising as a therapeutic ISR inhibitor.
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Project description:In times of cellular stress, such as during virus infections, the integrated stress response (ISR) blocks translation initiation through phosphorylation of the essential translation initiation factor eIF2. Phosphorylated eIF2 (p-eIF2) sequesters the eIF2-specific guanidine exchange factor (GEF) eIF2B, thereby preventing eIF2 recycling. Here we describe the first example of a viral ISR antagonist that inhibits the ISR at its most central step: the interplay between p-eIF2 and eIF2B. Using AP-MS, we determine that BW10 binds eIF2B. There, it selectively displaces eIF2B’s inhibitor p-eIF2 without affecting the association of its substrate eIF2. By this mechanism, BW10 renders cellular translation immune to regulation by eIF2 phosphorylation. Thus, under stress conditions BW10 creates the unprecedented situation of high levels of p-eIF2 coinciding with unimpaired translation.
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Project description:Disruption of protein folding in the endoplasmic reticulum triggers the Unfolded Protein Response (UPR), a transcriptional and translational control network designed to restore protein homeostasis. Central to the UPR is PERK phosphorylation of the alpha subunit of eIF2 (eIF2~P), which represses global translation coincident with preferential translation of mRNAs, such as ATF4 and CHOP, that serve to implement the UPR transcriptional regulation. In this study, we used sucrose gradient ultracentrifugation and a genome-wide microarray approach to measure changes in mRNA translation during ER stress. Our analysis suggests that translational efficiencies vary across a broad range during ER stress, with the majority of transcripts being either repressed or resistant to eIF2~P, while a notable cohort of key regulators are subject to preferential translation. From this latter group, we identify IBTKa as being subject to both translation and transcriptional induction during eIF2~P in both cell lines and a mouse model of ER stress. Translational regulation of IBTKalpha mRNA involves the stress-induced relief of two inhibitory uORFs in the 5'-leader of the transcript. Depletion of IBTKalpha by shRNA reduced viability of cultured cells coincident with increased caspase 3/7 cleavage, suggesting that IBTKalpha is a key regulator in determining cell fate during the UPR. We used a genome-wide microarray approach to determine how individual mRNAs were differentially translated during endoplasmic reticulum stress. A microarray analysis from our laboratory identified gene transcripts suggested to be under translation control in mouse embryonic fibroblast (MEF) cells following a 6 hour treatment with thapsigargin, a potent inducer of ER stress, or no stress. The mRNAs were separated by sucrose gradient analyses to yield three fractions, those transcripts associated with large polysomes (?4 ribosomes per mRNA), those associated with monosome, disomes, or trisomes, and those fractionated at the top of the gradient with free ribosomes. RNA was extracted from sucrose gradients corresponding to these fractions and hybridized on Affymetrix microarrays. In parallel, we also measured total levels for each gene transcript in the presence or absence of thapsigargin treatment to address transcription regulation coincident with translational control. Please note that the treatment plus fractionation based on association with different numbers of ribosomes did yield different populations of mRNAs, which resulted in considerable variation in normalized data across the samples.
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