Gene expression in 501mel melanoma cells treated with Salubrinal.
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE86806 | GEO | 2017/03/01
SECONDARY ACCESSION(S): PRJNA342589
REPOSITORIES: GEO
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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:The primary cause of cancer deaths is metastasis. While studies have identified multiple signals that drive invasiveness, the first step in metastatic colonization, the reason for cells to move away from the primary tumor is less well understood. The dataset presented here examines the effect of different culture conditions on gene expression by comparing expression of a melanoma cell line in nutrient rich DMEM to MEM. The results were used to generate a gene expression signature that correlates in human melanomas to dedifferentiation, invasiveness and drug resistance.
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Project description:Purpose: The integrated stress response (ISR) attenuates the rate of protein synthesis while inducing expression of stress proteins in cells. Various insults activate kinases that phosphorylate the GTPase eIF2 leading to inhibition of its exchange factor eIF2B. Vanishing White Matter (VWM) is a neurological disease caused by eIF2B mutations that, like phosphorylated eIF2, reduce its activity. We performed RNA-seq analysis of cerebellum collected from mice harboring a homozygous point mutation in eIF2B5 (HO R191H), a mutation that causes a severe form of VWM in humans and compared gene expression to wildtype age-matched littermates to identify transcriptomic differences at early, mid and late time points during disease progression. We also performed RNA-seq on cerebellum collected from animals treated with the eIF2B activator 2BAct for 1 month to determine to what extent small molecule treatment could normalize the VWM transcriptome. Methods: Samples were collected at 2, 5, and 7 months of age. In addition, HO R191H and WT mice treated with and without with the eIF2B activator 2BAct for 1 month were profiled. RNA-seq libraries were prepared using purified RNA isolated from frozen tissue using the RNeasy Mini kit. RNA quality and concentration were assayed using a Fragment Analyzer instrument. RNA-seq libraries were prepared using the TruSeq Stranded Total RNA kit paired with the Ribo-Zero rRNA removal kit. Libraries were sequenced on an Illumina HiSeq 4000 instrument. For the experiment comparing different ages, N = 3 males/genotype/time point. For the 4-week 2BAct treatment experiment, N = 3 females/condition. Conclusions: HO R191H mutant brains show an elevated gene expression signature of the Integrated Stress Reponse in mice as early as 2 months, preceding the appearance of overt pathology in these animals. The expression of the ISR-related genes does not significantly increases at 5 months and 7 months of age. One month of treatment with 2BAct completely prevented the expression of ISR-related in genes in 2 month old animals.
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Project description:Down syndrome (DS) is the most common genetic cause of intellectual disability and a major biomedical concern. Despite a general consensus that protein homeostasis is essential for normal brain function, little is known about its role in DS. Here, we show that the integrated stress response (ISR)—a conserved signaling network that maintains proteostasis by controlling protein synthesis—is activated in the brains of DS mice and individuals with DS, leading to reduced translation. Genetic and pharmacological suppression of the ISR, either by inhibiting the ISR-initiating double-stranded RNA-activated protein kinase (PKR) or boosting the function of the eIF2•eIF2B complex, which becomes limiting upon ISR activation, de-repressed translation, reversed enhanced inhibitory synaptic transmission, and rescued the deficits in synaptic plasticity and memory in DS mice. Our findings unveil a crucial role for the ISR in DS pathophysiology and suggest tuning of the ISR as a promising therapeutic intervention for DS.
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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.
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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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