scholarly journals Eukaryotic Translation Initiation Factor 4AI: A Potential Novel Target in Neuroblastoma

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 301
Author(s):  
Christina Skofler ◽  
Florian Kleinegger ◽  
Stefanie Krassnig ◽  
Anna Maria Birkl-Toeglhofer ◽  
Georg Singer ◽  
...  
Keyword(s):  
Cell Lines ◽  
Translation Initiation ◽  
Large Body ◽  
Response To Therapy ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cell Cycle Distribution ◽  
Malignant Cells ◽  
Oncogenic Signaling ◽  
Eif4f Complex

Neuroblastoma (NB) is the most common extracranial pediatric solid tumor. Children suffering from high-risk and/or metastatic NB often show no response to therapy, and new therapeutic approaches are urgently needed. Malignant tumor development has been shown to be driven by the dysregulation of eukaryotic initiation factors (eIFs) at the translation initiation. Especially the activity of the heterotrimeric eIF4F complex is often altered in malignant cells, since it is the direct connection to key oncogenic signaling pathways such as the PI3K/AKT/mTOR-pathway. A large body of literature exists that demonstrates targeting the translational machinery as a promising anti-neoplastic approach. The objective of this study was to determine whether eIF4F complex members are aberrantly expressed in NB and whether targeting parts of the complex may be a therapeutic strategy against NB. We show that eIF4AI is overexpressed in NB patient tissue using immunohistochemistry, immunoblotting, and RT-qPCR. NB cell lines exhibit decreased viability, increased apoptosis rates as well as changes in cell cycle distribution when treated with the synthetic rocaglate CR-1-31-B, which clamps eIF4A and eIF4F onto mRNA, resulting in a translational block. Additionally, this study reveals that CR-1-31-B is effective against NB cell lines at low nanomolar doses (≤20 nM), which have been shown to not affect non-malignant cells in previous studies. Thus, our study provides information of the expression status on eIF4AI in NB and offers initial promising insight into targeting translation initiation as an anti-tumorigenic approach for NB.

Increased levels of the translation initiation factor eIF4E in differentiating epithelial lung tumor cell lines

2003 ◽  
Vol 71 (2) ◽  
pp. 126-134 ◽  
Author(s):  
Derek Walsh ◽  
Paula Meleady ◽  
Brendan Power ◽  
Simon J. Morley ◽  
Martin Clynes
Keyword(s):  
Tumor Cell ◽  
Cell Lines ◽  
Translation Initiation ◽  
Lung Tumor ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Tumor Cell Lines ◽  
Lung Tumor Cell

scholarly journals Regulation of Protein Synthesis by Hypoxia via Activation of the Endoplasmic Reticulum Kinase PERK and Phosphorylation of the Translation Initiation Factor eIF2α

2002 ◽  
Vol 22 (21) ◽  
pp. 7405-7416 ◽  
Author(s):  
Constantinos Koumenis ◽  
Christine Naczki ◽  
Marianne Koritzinsky ◽  
Sally Rastani ◽  
Alan Diehl ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Translation Initiation ◽  
Prolonged Exposure ◽  
Response To Therapy ◽  
Dominant Negative ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Hypoxic Stress ◽  
Wild Type

ABSTRACT Hypoxia profoundly influences tumor development and response to therapy. While progress has been made in identifying individual gene products whose synthesis is altered under hypoxia, little is known about the mechanism by which hypoxia induces a global downregulation of protein synthesis. A critical step in the regulation of protein synthesis in response to stress is the phosphorylation of translation initiation factor eIF2α on Ser51, which leads to inhibition of new protein synthesis. Here we report that exposure of human diploid fibroblasts and transformed cells to hypoxia led to phosphorylation of eIF2α, a modification that was readily reversed upon reoxygenation. Expression of a transdominant, nonphosphorylatable mutant allele of eIF2α attenuated the repression of protein synthesis under hypoxia. The endoplasmic reticulum (ER)-resident eIF2α kinase PERK was hyperphosphorylated upon hypoxic stress, and overexpression of wild-type PERK increased the levels of hypoxia-induced phosphorylation of eIF2α. Cells stably expressing a dominant-negative PERK allele and mouse embryonic fibroblasts with a homozygous deletion of PERK exhibited attenuated phosphorylation of eIF2α and reduced inhibition of protein synthesis in response to hypoxia. PERK−/− mouse embryo fibroblasts failed to phosphorylate eIF2α and exhibited lower survival after prolonged exposure to hypoxia than did wild-type fibroblasts. These results indicate that adaptation of cells to hypoxic stress requires activation of PERK and phosphorylation of eIF2α and suggest that the mechanism of hypoxia-induced translational attenuation may be linked to ER stress and the unfolded-protein response.

scholarly journals mTORC1 signalling and eIF4E/4E-BP1 translation initiation factor stoichiometry influence recombinant protein productivity from GS-CHOK1 cells

2016 ◽  
Vol 473 (24) ◽  
pp. 4651-4664 ◽  
Author(s):  
Lyne Jossé ◽  
Jianling Xie ◽  
Christopher G. Proud ◽  
C. Mark Smales
Keyword(s):  
Protein Synthesis ◽  
Cell Growth ◽  
Recombinant Protein ◽  
Cell Lines ◽  
Translation Initiation ◽  
Mammalian Cells ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cho Cell

Many protein-based biotherapeutics are produced in cultured Chinese hamster ovary (CHO) cell lines. Recent reports have demonstrated that translation of recombinant mRNAs and global control of the translation machinery via mammalian target of rapamycin (mTOR) signalling are important determinants of the amount and quality of recombinant protein such cells can produce. mTOR complex 1 (mTORC1) is a master regulator of cell growth/division, ribosome biogenesis and protein synthesis, but the relationship between mTORC1 signalling, cell growth and proliferation and recombinant protein yields from mammalian cells, and whether this master regulating signalling pathway can be manipulated to enhance cell biomass and recombinant protein production (rPP) are not well explored. We have investigated mTORC1 signalling and activity throughout batch culture of a panel of sister recombinant glutamine synthetase-CHO cell lines expressing different amounts of a model monoclonal IgG4, to evaluate the links between mTORC1 signalling and cell proliferation, autophagy, recombinant protein expression, global protein synthesis and mRNA translation initiation. We find that the expression of the mTORC1 substrate 4E-binding protein 1 (4E-BP1) fluctuates throughout the course of cell culture and, as expected, that the 4E-BP1 phosphorylation profiles change across the culture. Importantly, we find that the eIF4E/4E-BP1 stoichiometry positively correlates with cell productivity. Furthermore, eIF4E amounts appear to be co-regulated with 4E-BP1 amounts. This may reflect a sensing of either change at the mRNA level as opposed to the protein level or the fact that the phosphorylation status, as well as the amount of 4E-BP1 present, is important in the co-regulation of eIF4E and 4E-BP1.

scholarly journals Stability of Eukaryotic Translation Initiation Factor 4E mRNA Is Regulated by HuR, and This Activity Is Dysregulated in Cancer

2008 ◽  
Vol 29 (5) ◽  
pp. 1152-1162 ◽  
Author(s):  
Ivan Topisirovic ◽  
Nadeem Siddiqui ◽  
Slobodanka Orolicki ◽  
Lucy A. Skrabanek ◽  
Mathieu Tremblay ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Cellular Proliferation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Malignant Cells ◽  
Functional Connection ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Transcript Stability ◽  
Eukaryotic Translation Initiation

ABSTRACT Eukaryotic translation initiation factor 4E (eIF4E) is encoded by a potent oncogene which is highly elevated in many human cancers. Few studies have investigated how the level, and thus activity, of eIF4E is regulated in healthy (noncancerous) cells and how they become elevated in malignant cells. Here, our studies reveal a novel mechanism by which eIF4E levels are regulated at the level of mRNA stability. Two factors known to modulate transcript stability, HuR and the p42 isoform of AUF1, compete for binding to the 3′ untranslated regions (3′UTRs) of eIF4E mRNAs. We identified a distinct AU-rich element in the 3′UTR of eIF4E which is responsible for HuR-mediated binding and stabilization. Our studies show that HuR is upregulated in malignant cancer specimens characterized by high eIF4E levels and that its depletion leads to reduction in eIF4E levels. Further, HuR and eIF4E regulate a common set of transcripts involved in cellular proliferation (cyclin D1 and c-myc) and neoangiogenesis (vascular endothelial growth factor), which suggests a functional connection between HuR and eIF4E in the regulation of these important processes. In summary, we present a novel model for the regulation of eIF4E expression and show that this model is relevant to elevation of eIF4E levels in malignant cells.

scholarly journals The eukaryotic translation initiation factor eIF4E reprogrammes the splicing machinery and drives alternative splicing

2021 ◽  
Author(s):  
Mehdi Ghram ◽  
Gavin Morris ◽  
Biljana Culjkovic-Kraljacic ◽  
Patrick Gendron ◽  
Lucy Skrabanek ◽  
...  
Keyword(s):  
Cell Lines ◽  
Translation Initiation ◽  
Rna Splicing ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Model Cell ◽  
Eukaryotic Translation Initiation ◽  
Aberrant Rna

Aberrant RNA splicing contributes to the pathogenesis of many malignancies including Acute Myeloid Leukemia (AML). While mutation is the best described mechanism underpinning aberrant splicing, recent studies show that predictions based on mutations alone likely underestimate the extent of this dysregulation1 . Here, we show that elevation of the eukaryotic translation initiation factor eIF4E reprogrammes splicing of nearly a thousand RNAs in model cell lines. In AML patient specimens which did not harbour known splice factor mutations, ~4000 transcripts were differentially spliced based on eIF4E levels and this was associated with poor prognosis. Inhibition of eIF4E in cell lines reverted the eIF4E-dependent splice events examined. Splicing targets of eIF4E act in biological processes consistent with its role in malignancy. This altered splicing program likely arose from eIF4E-dependnet increases in the production of many components of the spliceosome including SF3B1 and U2AF1 which are frequently mutated in AML. Notably, eIF4E did not drive mutation of these factors, only their production. eIF4E also physically associated with many splice factors including SF3B1, U2AF1, and UsnRNAs. Importantly, many eIF4E-dependent splice events differed from those arising from SF3B1 mutation, and were more extensive highlighting that these splicing profiles arise from distinct mechanisms. In all, our studies provide a paradigm for how dysregulation of a single factor, eIF4E, can alter splicing.

scholarly journals The Eukaryotic Translation Initiation Factor 4F Complex Restricts Rotavirus Infection via Regulating the Expression of IRF1 and IRF7

2019 ◽  
Vol 20 (7) ◽  
pp. 1580 ◽  
Author(s):  
Sunrui Chen ◽  
Cui Feng ◽  
Yan Fang ◽  
Xinying Zhou ◽  
Lei Xu ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Negative Regulator ◽  
Initiation Factor ◽  
Loss Of Function ◽  
Rotavirus Infection ◽  
Eukaryotic Translation ◽  
Initiation Factors ◽  
Eif4f Complex ◽  
Translation Initiation Factors

The eIF4F complex is a translation initiation factor that closely regulates translation in response to a multitude of environmental conditions including viral infection. How translation initiation factors regulate rotavirus infection remains poorly understood. In this study, the knockdown of the components of the eIF4F complex using shRNA and CRISPR/Cas9 were performed, respectively. We have demonstrated that loss-of-function of the three components of eIF4F, including eIF4A, eIF4E and eIF4G, remarkably promotes the levels of rotavirus genomic RNA and viral protein VP4. Consistently, knockdown of the negative regulator of eIF4F and programmed cell death protein 4 (PDCD4) inhibits the expression of viral mRNA and the VP4 protein. Mechanically, we confirmed that the silence of the eIF4F complex suppressed the protein level of IRF1 and IRF7 that exert potent antiviral effects against rotavirus infection. Thus, these results demonstrate that the eIF4F complex is an essential host factor restricting rotavirus replication, revealing new targets for the development of new antiviral strategies against rotavirus infection.

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