Eukaryotic initiation factor 6, an evolutionarily conserved regulator of ribosome biogenesis and protein translation

The eukaryotic initiation factor 4E (eIF4E) is a major mRNA cap-binding protein that has a central role in translation initiation. Ser209 is the single phosphorylation site within eIF4E and modulates its activity in response to MAPK pathway activation. It has been reported that phosphorylation of eIF4E at Ser209 promotes translation of key mRNAs, such as cyclin D1, that regulate ribosome biogenesis. We hypothesized that phosphorylation at Ser209 is required for skeletal muscle growth in response to a hypertrophic stimulus by promoting ribosome biogenesis. To test this hypothesis, wild-type (WT) and eIF4E knocked-in (KI) mice were subjected to synergist ablation to induce muscle hypertrophy of the plantaris muscle as the result of mechanical overload; in the KI mouse, Ser209 of eIF4E was replaced with a nonphosphorylatable alanine. Contrary to our hypothesis, we observed no difference in the magnitude of hypertrophy between WT and KI groups in response to 14 days of mechanical overload induced by synergist ablation. Similarly, the increases in cyclin D1 protein levels, ribosome biogenesis, and translational capacity did not differ between WT and KI groups. Based on these findings, we conclude that phosphorylation of eIF4E at Ser209 is dispensable for skeletal muscle hypertrophy in response to mechanical overload.

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Eukaryotic initiation factor 6 mediates a continuum between 60S ribosome biogenesis and translation

EMBO Reports ◽

10.1038/embor.2009.70 ◽

2009 ◽

Vol 10 (5) ◽

pp. 459-465 ◽

Cited By ~ 65

Author(s):

Annarita Miluzio ◽

Anne Beugnet ◽

Viviana Volta ◽

Stefano Biffo

Keyword(s):

Ribosome Biogenesis ◽

Initiation Factor ◽

Eukaryotic Initiation Factor

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Phosphorylation of Eukaryotic Translation Initiation Factor 2α Coordinates rRNA Transcription and Translation Inhibition during Endoplasmic Reticulum Stress

Molecular and Cellular Biology ◽

10.1128/mcb.00260-09 ◽

2009 ◽

Vol 29 (15) ◽

pp. 4295-4307 ◽

Cited By ~ 65

Author(s):

Jenny B. DuRose ◽

Donalyn Scheuner ◽

Randal J. Kaufman ◽

Lawrence I. Rothblum ◽

Maho Niwa

Keyword(s):

Endoplasmic Reticulum ◽

Ribosome Biogenesis ◽

Critical Role ◽

Mammalian Target Of Rapamycin ◽

Protein Translation ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Rrna Synthesis ◽

Cell Physiology ◽

Rrna Transcription

ABSTRACT The endoplasmic reticulum (ER) is the major cellular compartment where folding and maturation of secretory and membrane proteins take place. When protein folding needs exceed the capacity of the ER, the unfolded protein response (UPR) pathway modulates gene expression and downregulates protein translation to restore homeostasis. Here, we report that the UPR downregulates the synthesis of rRNA by inactivation of the RNA polymerase I basal transcription factor RRN3/TIF-IA. Inhibition of rRNA synthesis does not appear to involve the well-characterized mTOR (mammalian target of rapamycin) pathway; instead, PERK-dependent phosphorylation of eIF2α plays a critical role in the inactivation of RRN3/TIF-IA. Downregulation of rRNA transcription occurs simultaneously or slightly prior to eIF2α phosphorylation-induced translation repression. Since rRNA is the most abundant RNA species, constituting ∼90% of total cellular RNA, its downregulation exerts a significant impact on cell physiology. Our study demonstrates the first link between regulation of translation and rRNA synthesis with phosphorylation of eIF2α, suggesting that this pathway may be broadly utilized by stresses that activate eIF2α kinases in order to coordinately regulate translation and ribosome biogenesis during cellular stress.

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Eukaryotic initiation factor 3, subunit C silencing inhibits cell proliferation and promotes apoptosis in human ovarian cancer cells

Bioscience Reports ◽

10.1042/bsr20191124 ◽

2019 ◽

Vol 39 (8) ◽

Cited By ~ 3

Author(s):

Fang Wen ◽

Zhang-Ying Wu ◽

Lei Nie ◽

Qi-Zhu Zhang ◽

Yuan-Kun Qin ◽

...

Keyword(s):

Ovarian Cancer ◽

Cancer Cells ◽

Cancer Cell ◽

Molecular Mechanisms ◽

Protein Translation ◽

Initiation Factor ◽

Ovarian Cancer Cells ◽

Human Ovarian Cancer ◽

Eukaryotic Initiation Factor ◽

Translational Initiation

Abstract Ovarian cancer remains the leading cause of death among all gynaecological cancers, illustrating the urgent need to understand the molecular mechanisms involved in this disease. Eukaryotic initiation factor 3c (EIF3c) plays an important role in protein translation and cancer cell growth and proliferation, but its role in human ovarian cancer is unclear. Our results showed that EIF3c silencing significantly up-regulated 217 and down-regulated 340 genes. Ingenuity Pathway Analysis (IPA) indicated that the top differentially expressed genes are involved in ‘Classical Pathways’, ‘Diseases and Functions’ and ‘Networks’, especially those involved in signalling and cellular growth and proliferation. In addition, eIF3c silencing inhibited cellular proliferation, enhanced apoptosis and regulated the expression of apoptosis-associated proteins. In conclusion, these results indicate that by dysregulating translational initiation, eIF3c plays an important role in the proliferation and survival of human ovarian cancer cells. These results should provide experimental directions for further in-depth studies on important human ovarian cancer cell pathways.

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The Integrated Stress Response and Phosphorylated Eukaryotic Initiation Factor 2α in Neurodegeneration

Journal of Neuropathology & Experimental Neurology ◽

10.1093/jnen/nlz129 ◽

2020 ◽

Vol 79 (2) ◽

pp. 123-143 ◽

Cited By ~ 16

Author(s):

Sarah Bond ◽

Claudia Lopez-Lloreda ◽

Patrick J Gannon ◽

Cagla Akay-Espinoza ◽

Kelly L Jordan-Sciutto

Keyword(s):

Stress Response ◽

Molecular Mechanisms ◽

Protein Translation ◽

Cell Types ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Integrated Stress Response ◽

Eukaryotic Initiation Factor ◽

Pharmacological Agents ◽

Eif2α Phosphorylation

Abstract The proposed molecular mechanisms underlying neurodegenerative pathogenesis are varied, precluding the development of effective therapies for these increasingly prevalent disorders. One of the most consistent observations across neurodegenerative diseases is the phosphorylation of eukaryotic initiation factor 2α (eIF2α). eIF2α is a translation initiation factor, involved in cap-dependent protein translation, which when phosphorylated causes global translation attenuation. eIF2α phosphorylation is mediated by 4 kinases, which, together with their downstream signaling cascades, constitute the integrated stress response (ISR). While the ISR is activated by stresses commonly observed in neurodegeneration, such as oxidative stress, endoplasmic reticulum stress, and inflammation, it is a canonically adaptive signaling cascade. However, chronic activation of the ISR can contribute to neurodegenerative phenotypes such as neuronal death, memory impairments, and protein aggregation via apoptotic induction and other maladaptive outcomes downstream of phospho-eIF2α-mediated translation inhibition, including neuroinflammation and altered amyloidogenic processing, plausibly in a feed-forward manner. This review examines evidence that dysregulated eIF2a phosphorylation acts as a driver of neurodegeneration, including a survey of observations of ISR signaling in human disease, inspection of the overlap between ISR signaling and neurodegenerative phenomenon, and assessment of recent encouraging findings ameliorating neurodegeneration using developing pharmacological agents which target the ISR. In doing so, gaps in the field, including crosstalk of the ISR kinases and consideration of ISR signaling in nonneuronal central nervous system cell types, are highlighted.

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ICP34.5 Protein of Herpes Simplex Virus Facilitates the Initiation of Protein Translation by Bridging Eukaryotic Initiation Factor 2α (eIF2α) and Protein Phosphatase 1

Journal of Biological Chemistry ◽

10.1074/jbc.m111.232439 ◽

2011 ◽

Vol 286 (28) ◽

pp. 24785-24792 ◽

Cited By ~ 54

Author(s):

Yapeng Li ◽

Cuizhu Zhang ◽

Xiangdong Chen ◽

Jia Yu ◽

Yu Wang ◽

...

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Protein Phosphatase ◽

Protein Translation ◽

Protein Phosphatase 1 ◽

Initiation Factor ◽

Eukaryotic Initiation Factor ◽

Simplex Virus

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Eukaryotic initiation factor 6 regulates mechanical responses in endothelial cells

The Journal of Cell Biology ◽

10.1083/jcb.202005213 ◽

2022 ◽

Vol 221 (2) ◽

Author(s):

Adam N. Keen ◽

Luke A. Payne ◽

Vedanta Mehta ◽

Alistair Rice ◽

Lisa J. Simpson ◽

...

Keyword(s):

Endothelial Cells ◽

Protein Synthesis ◽

Traction Force ◽

Protein Translation ◽

Initiation Factor ◽

Eukaryotic Initiation Factor ◽

Cellular Mechanics ◽

Mechanical Responses ◽

Cell Signaling Networks ◽

Cellular Cytoskeleton

The repertoire of extratranslational functions of components of the protein synthesis apparatus is expanding to include control of key cell signaling networks. However, very little is known about noncanonical functions of members of the protein synthesis machinery in regulating cellular mechanics. We demonstrate that the eukaryotic initiation factor 6 (eIF6) modulates cellular mechanobiology. eIF6-depleted endothelial cells, under basal conditions, exhibit unchanged nascent protein synthesis, polysome profiles, and cytoskeleton protein expression, with minimal effects on ribosomal biogenesis. In contrast, using traction force and atomic force microscopy, we show that loss of eIF6 leads to reduced stiffness and force generation accompanied by cytoskeletal and focal adhesion defects. Mechanistically, we show that eIF6 is required for the correct spatial mechanoactivation of ERK1/2 via stabilization of an eIF6–RACK1–ERK1/2–FAK mechanocomplex, which is necessary for force-induced remodeling. These results reveal an extratranslational function for eIF6 and a novel paradigm for how mechanotransduction, the cellular cytoskeleton, and protein translation constituents are linked.

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Discovery of a small molecule that inhibits bacterial ribosome biogenesis

eLife ◽

10.7554/elife.03574 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 39

Author(s):

Jonathan M Stokes ◽

Joseph H Davis ◽

Chand S Mangat ◽

James R Williamson ◽

Eric D Brown

Keyword(s):

Small Molecule ◽

Ribosome Biogenesis ◽

Anticonvulsant Drug ◽

Protein Translation ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Bacterial Ribosome ◽

Cold Sensitive

While small molecule inhibitors of the bacterial ribosome have been instrumental in understanding protein translation, no such probes exist to study ribosome biogenesis. We screened a diverse chemical collection that included previously approved drugs for compounds that induced cold sensitive growth inhibition in the model bacterium Escherichia coli. Among the most cold sensitive was lamotrigine, an anticonvulsant drug. Lamotrigine treatment resulted in the rapid accumulation of immature 30S and 50S ribosomal subunits at 15°C. Importantly, this was not the result of translation inhibition, as lamotrigine was incapable of perturbing protein synthesis in vivo or in vitro. Spontaneous suppressor mutations blocking lamotrigine activity mapped solely to the poorly characterized domain II of translation initiation factor IF2 and prevented the binding of lamotrigine to IF2 in vitro. This work establishes lamotrigine as a widely available chemical probe of bacterial ribosome biogenesis and suggests a role for E. coli IF2 in ribosome assembly.

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The eukaryotic Initiation Factor 6 (eIF6) regulates ecdysone biosynthesis by modulating translation in Drosophila

10.1101/201558 ◽

2017 ◽

Author(s):

Arianna Russo ◽

Guido Gatti ◽

Roberta Alfieri ◽

Elisa Pesce ◽

Kelly Soanes ◽

...

Keyword(s):

Ribosome Biogenesis ◽

Biosynthetic Pathway ◽

Single Gene ◽

Initiation Factor ◽

Eukaryotic Initiation Factor ◽

Developmental Models ◽

Translation Factors ◽

General Translation

ABSTRACTDuring development, ribosome biogenesis and translation reach peak activities, due to impetuous cell proliferation. Current models predict that protein synthesis elevation is controlled by transcription factors and signalling pathways. Developmental models addressing translation factors overexpression effects are lacking. Eukaryotic Initiation Factor (eIF6) is necessary for ribosome biogenesis and efficient translation. eIF6 is a single gene, conserved from yeasts to mammals, suggesting a tight regulation need. We generated a Drosophila melanogaster in vivo model of eIF6 upregulation, demonstrating a boost in general translation and the shut off of the ecdysone biosynthetic pathway. Translation modulation in S2 cells showed that translational rate and ecdysone biosynthesis are inversely correlated. In vivo, eIF6-driven alterations delayed programmed cell death (PCD), resulting in aberrant phenotypes, partially rescued by ecdysone administration. Our data show that eIF6 triggers a translation program with far-reaching effects on metabolism and development, stressing the driving and central role of translation.

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