Human eIF2A has a minimal role in translation initiation and in uORFmediated translational control
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ABSTRACT:
PROVIDER: PRJNA1189055 | ENA |
REPOSITORIES: ENA
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Project description:We apply ribosome profiling here to assess the role of eIF2A in translation initiation. For this we test the change in translation efficiency between HeLa control and eIF2A-KO cells, however we do not find any transcript to depend on eIF2A. Since eIF2A is thought to take over the function of eIF2 when eIF2 is inhibited, we also test conditions where the integrated stress response is activated, thereby leading to eIF2 inactivation. In none of our assays, however, could we detect a role of eIF2A in translation initiation.
2024-11-29 | GSE282509 | GEO
Project description:Yeast eIF2A plays a minimal role in translation initiation in vivo
| PRJNA1008247 | ENA
Project description:Earlier investigations have associated mammalian eIF2A with Met-tRNAi binding to the 40S subunit and its recruitment to specialized mRNAs in a GTP-independent manner. Additionally, eIF2A has been implicated in non-AUG start codon initiation, particularly under conditions where eIF2 function is attenuated by phosphorylation of its α-subunit during stress or starvation. However, the precise role of eIF2A in vivo translation remains unclear. Moreover, it's uncertain if the conserved ortholog in budding yeast can functionally substitute for eIF2 during stress. To address these questions, we conducted ribosome profiling on a yeast deletion mutant lacking eIF2A, alongside isogenic wild-type (WT) cells, both in the presence or absence of eIF2α phosphorylation induced by amino acid starvation.
2024-01-03 | GSE241473 | GEO
Project description:Endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) helps decide b cell survival in diabetes. The alternative eukaryotic initiation factor 2A (EIF2A) has been proposed to mediate EIF2S1-independent translation during cellular stress and viral infection, but its role in b cells is unknown. EIF2A abundance is high in human and mouse islets relative to other tissues, and both thapsigargin and palmitate significantly increased EIF2A mRNA and EIF2A protein levels in MIN6 cells, mouse islets and human islets. Knockdowns of EIF2A, the related factor EIF2D, or both EIF2A and EIF2D, were not sufficient to cause apoptosis. On the other hand, transient or stable EIF2A over-expression protected MIN6 cells, primary mouse islets, and human islets from ER stress-induced, caspase-3-dependent apoptosis. Mechanistically, EIF2A overexpression decreased ERN1 (also known as IRE1a) expression in thapsigargin-treated MIN6 cells or human islets. In vivo, b cell specific EIF2A viral overexpression reduced ER stress, improved insulin signaling, and abrogated hyperglycemia in Ins2Akita/WT mice. EIF2A overexpression significantly increased expression of genes involved protein translation and reduced expression of pro-apoptotic genes (e.g. ALDH1A3). Remarkably, the decrease in global protein synthesis during UPR was prevented by EIF2A, despite ER stress-induced EIF2S1 phosphorylation. The protective effects of EIF2A were additive to those of ISRIB, a drug that counteracts the effects of EIF2S1 phosphorylation. Cells overexpressing EIF2A showed higher expression of translation factor EIF2B5, which may contribute to the lack of translational inhibition in these cells. We conclude that EIF2A is a novel target for b cell protection and the circumvention of EIF2S1-mediated translational repression.
2022-08-31 | GSE166829 | GEO
Project description:Many positive-strand RNA viruses, including all known coronaviruses, employ programmed –1 ribosomal frameshifting (–1 PRF) to regulate the translation of polycistronic viral RNAs. However, only a few host factors have been shown to regulate –1 PRF. Through a reporter-based genome-wide CRISPR/Cas9 knockout screen, we identified several host factors that either suppressed or enhanced –1 PRF of SARS-CoV-2. One of these factors is eukaryotic translation initiation factor 2A (eIF2A), which specifically and directly enhanced –1 PRF in vitro and in cells. Consistent with the crucial role of efficient –1 PRF in transcriptase/replicase expression, loss of eIF2A reduced SARS-CoV-2 replication in cells. Transcriptome-wide analysis of eIF2A-interacting RNAs showed that eIF2A primarily interacted with 18S ribosomal RNA near the contacts between the SARS-CoV-2 frameshift-stimulatory element (FSE) and the ribosome. Thus, our results revealed an unexpected role for eIF2A in modulating the translation of specific RNAs independent of its previously described role during initiation.
2024-07-11 | GSE223690 | GEO
Project description:Cellular signaling controls translation through cis regulatory elements found in mRNAs. Gcn2 is the master regulator of translation during nutrient limitation in normal and cancer cells. Activated Gcn2 phosphorylates eIF2a, thereby repressing general translation while activating translation of specific mRNAs with upstream ORFs (uORFs) in its leader regions. Here we performed genome-wide measurement of mRNA translation during histidine starvation in fission yeast Schizosaccharomyces pombe. Polysomal microarray hybridization experiments identified a group of 1779 genes whose translation is up-regulated in Gcn2-dependent manner. We find that translation is reprogrammed to enhance organellar synthesis and transcription and repress ribosome synthesis. The 1779 genes included gcn5 and hri2 shown to promote growth under histidine starvation. They encode histone acetyl transferase and heme-binding eIF2a kinase activated by oxidative stress, and their 5’-leader contains 3 or 4 uORFs, respectively. Our reporter studies show that uORFs in gcn5 and hri2 operate similarly to those found in S. cerevisiae GCN4, the founding case for uORF-dependent regulation. Moreover, motif analysis identified 5’-UGA(C/G)GG-3’ as a motif promoting translation during starvation. Using hrd1 5’UTR with such a motif, we demonstrated its requirement in Gcn2-dependent translational control. To our knowledge, this is the first nucleotide motif found to be responsible for translational control by Gcn2. We propose that Gcn2 mediates translational control of more specific mRNAs than previously anticipated
2020-09-23 | GSE143299 | GEO
Project description:DUX4, an embryonic transcription factor normally silenced in somatic tissues, was recently shown to reduce major histocompatibility complex I (MHC-I) and promote immune evasion in numerous cancer types. We report that transient expression of DUX4 results in the long-term suppression of interferon-gamma induction of MHC-I and the immunoproteasome. Brief expression of transcriptionally active DUX4 leads to a prolonged decrease in protein synthesis, altering the activity of translation initiation regulators eIF2a, eIF4E, 4EBP1, and translation elongation factor eEF2. Translational profiling identified mRNAs susceptible to DUX4-induced inhibition of translation initiation and elongation, including mRNAs encoding antigen presentation factors. We show that DUX4 orchestrates translational reprogramming by broadly attenuating protein synthesis while inducing the expression of RNAs encoding early embryonic proteins that are translationally up regulated and predicted to be less vulnerable to translational inhibition. Endogenous expression of DUX4 and its target genes in FSHD muscle cells and SuSa germinoma cells also correlates with suppression of protein synthesis and reduced MHC-I presentation. Our findings reveal a novel role of DUX4 in modulating translational control to reshape the cellular translatome with important implications for development and disease.
2023-02-01 | GSE206438 | GEO
Project description:DUX4, an embryonic transcription factor normally silenced in somatic tissues, was recently shown to reduce major histocompatibility complex I (MHC-I) and promote immune evasion in numerous cancer types. We report that transient expression of DUX4 results in the long-term suppression of interferon-gamma induction of MHC-I and the immunoproteasome. Brief expression of transcriptionally active DUX4 leads to a prolonged decrease in protein synthesis, altering the activity of translation initiation regulators eIF2a, eIF4E, 4EBP1, and translation elongation factor eEF2. Translational profiling identified mRNAs susceptible to DUX4-induced inhibition of translation initiation and elongation, including mRNAs encoding antigen presentation factors. We show that DUX4 orchestrates translational reprogramming by broadly attenuating protein synthesis while inducing the expression of RNAs encoding early embryonic proteins that are translationally up regulated and predicted to be less vulnerable to translational inhibition. Endogenous expression of DUX4 and its target genes in FSHD muscle cells and SuSa germinoma cells also correlates with suppression of protein synthesis and reduced MHC-I presentation. Our findings reveal a novel role of DUX4 in modulating translational control to reshape the cellular translatome with important implications for development and disease.
2023-04-11 | GSE206436 | GEO
Project description:DUX4, an embryonic transcription factor normally silenced in somatic tissues, was recently shown to reduce major histocompatibility complex I (MHC-I) and promote immune evasion in numerous cancer types. We report that transient expression of DUX4 results in the long-term suppression of interferon-gamma induction of MHC-I and the immunoproteasome. Brief expression of transcriptionally active DUX4 leads to a prolonged decrease in protein synthesis, altering the activity of translation initiation regulators eIF2a, eIF4E, 4EBP1, and translation elongation factor eEF2. Translational profiling identified mRNAs susceptible to DUX4-induced inhibition of translation initiation and elongation, including mRNAs encoding antigen presentation factors. We show that DUX4 orchestrates translational reprogramming by broadly attenuating protein synthesis while inducing the expression of RNAs encoding early embryonic proteins that are translationally up regulated and predicted to be less vulnerable to translational inhibition. Endogenous expression of DUX4 and its target genes in FSHD muscle cells and SuSa germinoma cells also correlates with suppression of protein synthesis and reduced MHC-I presentation. Our findings reveal a novel role of DUX4 in modulating translational control to reshape the cellular translatome with important implications for development and disease.
2023-02-01 | GSE206437 | GEO
Project description:Translation initiation is a complex and highly regulated process that represents an important mechanism, controlling gene expression. eIF2A was proposed as an alternative initiation factor, however, its role and biological targets remain to be discovered. To further gain insight into the function of eIF2A in Saccharomyces cerevisiae, we identified mRNAs associated with the eIF2A complex and showed that 24% of the most enriched mRNAs encode proteins related to cell wall biogenesis and maintenance. In agreement with this result, we showed that an eIF2A deletion sensitized cells to cell wall damage induced by calcofluor white. eIF2A overexpression led to a growth defect, correlated with decreased synthesis of several cell wall proteins. In contrast, no changes were observed in the transcriptome, suggesting that eIF2A controls the expression of cell wall-related proteins at a translational level. The biochemical characterization of the eIF2A complex revealed that it strongly interacts with the RNA binding protein, Ssd1, which is a negative translational regulator, controlling the expression of cell wall-related genes. Interestingly, eIF2A and Ssd1 bind several common mRNA targets and we found that the binding of eIF2A to some targets was mediated by Ssd1. Surprisingly, we further showed that eIF2A is physically and functionally associated with the exonuclease Xrn1 and other mRNA degradation factors, suggesting an additional level of regulation. Altogether, our results highlight new aspects of this complex and redundant fine-tuned regulation of proteins expression related to the cell wall, a structure required to maintain cell shape and rigidity, providing protection against harmful environmental stress.
2023-09-15 | PXD043985 | Pride