Discordant regulation of eIF2 kinase GCN2 and mTORC1 during nutrient stress
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA659366 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR12515026_1.fastq.gz | Fastqsanger.gz | |||
| SRR12515026_2.fastq.gz | Fastqsanger.gz | |||
| SRR12515027_1.fastq.gz | Fastqsanger.gz | |||
| SRR12515027_2.fastq.gz | Fastqsanger.gz | |||
| SRR12515028_1.fastq.gz | Fastqsanger.gz |
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Project description:Here we report Total RNA seq and RiboSeq on MEF cells treated with halofuginone. Halofuginone is a competitive inhibitor of the Prolyl-tRNA synthetase that results in an accumulation of uncharged Prolyl-tRNA upon treatment that leads to an activation of the protein kinase Gcn2.
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Project description:Appropriate regulation of the Integrated stress response (ISR) and mTORC1 signaling are central for cell adaptation to starvation for amino acids. Halofuginone (HF) is a potent inhibitor of aminoacylation of tRNAPro with broad biomedical applications. Here, we show that in addition to translational control directed by activation of the ISR by general control nonderepressible 2 (GCN2), HF increased free amino acids and directed translation of genes involved in protein biogenesis via sustained mTORC1 signaling. Deletion of GCN2 reduced cell survival to HF whereas pharmacological inhibition of mTORC1 afforded protection. HF treatment of mice synchronously activated the GCN2-mediated ISR and mTORC1 in liver whereas Gcn2-null mice allowed greater mTORC1 activation to HF, resulting in liver steatosis and cell death. We conclude that HF causes an amino acid imbalance that uniquely activates both GCN2 and mTORC1. Loss of GCN2 during HF creates a disconnect between metabolic state and need, triggering proteostasis collapse.
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Project description:Diverse environmental insults induce the integrated stress response (ISR), which features eIF2 phosphorylation and translational control that serves to restore protein homeostasis. The eIF2 kinase GCN2 is a first responder in the ISR that is activated by amino acid depletion and other unrelated stresses. Two processes are suggested to trigger an ordered process of GCN2 activation during stress: GCN2 monitoring stress via accumulating uncharged tRNAs or by stalled and colliding ribosomes. Our results suggest that while ribosomal collisions are indeed essential for GCN2 activation in response to translational elongation inhibitors, conditions that trigger deacylation of tRNAs activate GCN2 via its direct association with affected tRNAs. Both process require the GCN2 regulatory domain related to histidyl tRNA synthetases. GCN2 activation by UV irradiation features lowered amino acids and increased uncharged tRNAs and ribosome collisions are dispensable. We conclude that there are multiple mechanisms that activate GCN2 during diverse stresses.
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Project description:La-related protein 1 (LARP1) has been identified as a key translational inhibitor of terminal oligopyrimidine tract (TOP) mRNAs downstream of the nutrient sensing protein kinase complex, mTORC1. LARP1 exerts this inhibitory effect on TOP mRNA translation by binding to the mRNA cap and the adjacent 5’TOP motif, resulting in the displacement of the eIF4E complex from TOP mRNAs. In the present study, we identify a second nutrient sensing kinase GCN2 that converges on LARP1 to control TOP mRNA translation. GCN2 inhibits TOP mRNA translation via ATF4-dependent transcriptional induction of LARP1 mRNAs and GCN1-mediated recruitment of LARP1 to stalled ribosomes. We performed ATF4 ChIP-seq experiments in both WT and GCN2 KO MEFs with or without leucine deprivation.
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Project description:Cancers invoke response pathways to mitigate external and internal stresses to aid growth and proliferation. For example, we reported that GCN2 eIF2 kinase and the Integrated Stress Response are constitutively active in prostate cancer (PCa) and are required to maintain amino acid homeostasis needed to fuel tumor growth. However, while genetic or pharmacological loss of GCN2 lowers intracellular amino acids and deters PCa growth, there does not appear to be appreciable cell death. Using biochemical and molecular approaches, RNA-seq and CRISPRi-based screens, along with in vitro and in vivo PCa models, we discovered that the loss of GCN2 in PCa induces p53 signaling and tumor senescence. Activation of p53 occurs by reductions in purine nucleobases and lowered rRNA synthesis that induce the Impaired Ribosome Biogenesis Checkpoint. Loss of GCN2 combined with depletion of p53 or pharmacological inhibition of de novo purine biosynthesis with the GART inhibitor pelitrexol sharply reduces PCa growth and triggers apoptosis, emphasizing the importance of coordinated GCN2 and p53 regulation and their utility in PCa therapeutics.
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Project description:When eukaryotic cells are deprived of amino acids, uncharged tRNAs accumulate and activate the conserved GCN2 protein kinase. We examine how yeast growth and tRNA charging or aminoacylation is affected during amino acid depletion in the presence and absence of GCN2. tRNA charging is measured using a microarray technique which allows for simultaneous measurement of all cytosolic tRNAs. A fully prototrophic and its isogenic GCN2 deletion strain were used. We measured relative tRNA charging levels in yeast strains with an intact and deleted GCN2.
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Project description:Multiple mechanisms activate GCN2 eIF2 kinase in response to diverse stress conditions
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Project description:When eukaryotic cells are deprived of amino acids, uncharged tRNAs accumulate and activate the conserved GCN2 protein kinase. We examine how yeast growth and tRNA charging or aminoacylation is affected during amino acid depletion in the presence and absence of GCN2. tRNA charging is measured using a microarray technique which allows for simultaneous measurement of all cytosolic tRNAs. A fully prototrophic and its isogenic GCN2 deletion strain were used.
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Project description:Circadian clocks are evolved to adapt to the daily environment changes under different conditions. The ability to maintain circadian clock functions in response to various stress and perturbations is important for organismal fitness. Here, we show that the nutrient sensing GCN2 signaling pathway is required for robust circadian clock function under amino acid starvation in Neurospora. The deletion of GCN2 pathway components disrupts rhythmic transcription of clock gene frq by suppressing WC complex binding at the frq promoter due to its reduced histone H3 acetylation levels. Under amino acid starvation, the activation of GCN2 kinase and its downstream transcription factor CPC-1 establish a proper chromatin state at the frq promoter by recruiting the histone acetyltransferase GCN-5. The arrhythmic phenotype of the GCN2 kinase mutants under amino acid starvation can be rescued by inhibiting histone deacetylation. Finally, genome-wide transcriptional analysis indicates that the GCN2 signaling pathway maintains robust rhythmic expression of metabolic genes under amino acid starvation. Together, these results uncover an essential role of GCN2 signaling pathway in maintaining robust circadian clock function in response to amino acid starvation and the importance of histone acetylation at the frq locus in rhythmic gene expression.
2023-05-08 | GSE220169 | GEO
Project description:In eukaryotes, regulation of mRNA translation enables a fast, localized and finely tuned expression of gene products. Within the translation process, the first stage of translation initiation is most rigorously modulated by the actions of eukaryotic initiation factors (eIFs) and their associated proteins. These 11 eIFs catalyze the joining of the tRNA, mRNA and rRNA into a functional translation complex. Their activity is influenced by a wide variety of extra- and intracellular signals, ranging from global, such as hormone signaling and unfolded proteins, to specific, such as single amino acid imbalance and iron deficiency. Their action is correspondingly comprehensive, in increasing or decreasing recruitment and translation of most cellular mRNAs, and specialized, in targeting translation of mRNAs with regulatory features such as a 5’ terminal oligopyrimidine tract (TOP), upstream open reading frames (uORFs), or an internal ribosomal entry site (IRES). In mammals, two major pathways are linked to targeted mRNA translation. The target of rapamycin (TOR) kinase induces translation of TOP and perhaps other subsets of mRNAs, whereas a family of eIF2 kinases does so with mRNAs containing uORFs or an IRES. TOR targets translation of mRNAs that code for proteins involved in translation, an action compatible with its widely accepted role in regulating cellular growth. The four members of the eIF2 kinase family increase translation of mRNAs coding for stress response proteins such as transcription factors and chaperones. Though all four kinases act on one main substrate, eIF2, published literature demonstrates both common and unique effects by each kinase in response to its specific activating stress. This suggests that the activated eIF2 kinases regulate the translation of both a global and a specific set of mRNAs. Up to now, few studies have attempted to test such a hypothesis; none has been done in mammals. We use array analysis to determine the global mRNA shift into polysomes following a stress response, and to compare the translational response following activation of GCN2 versus PERK, two of the four eIF2alpha kinases. Experiment Overall Design: Gcn2 wild-type or knockout mouse liver were perfused with complete amino acids media or media lacking methionine for RNA extraction and hybridization of Affymetrix microarrays. RNA was extracted from unfractionated liver samples and polysome fraction of samples separated on sucrose density gradient. To minimize biological variations, we pooled RNA from two perfused liver samples to use in each array analysis. The conditions were total and polysome fraction of Gcn2+/+, +Met or -Met; total and polysome fraction of Gcn2-/-, +Met or -Met. Each array analysis was done in duplicate.
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