scholarly journals Feedback Regulation of O-GlcNAc Transferase through Translation Control to Maintain Intracellular O-GlcNAc Homeostasis

2021 ◽  
Vol 22 (7) ◽  
pp. 3463
Author(s):  
Chia-Hung Lin ◽  
Chen-Chung Liao ◽  
Mei-Yu Chen ◽  
Teh-Ying Chou
Keyword(s):  
Molecular Mechanisms ◽  
Mrna Level ◽  
Feedback Regulation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cell Physiology ◽  
Hydroxyl Groups ◽  
Post Translational Modification ◽  
Translation Control ◽  
Glcnac Transferase

Protein O-GlcNAcylation is a dynamic post-translational modification involving the attachment of N-acetylglucosamine (GlcNAc) to the hydroxyl groups of Ser/Thr residues on numerous nucleocytoplasmic proteins. Two enzymes are responsible for O-GlcNAc cycling on substrate proteins: O-GlcNAc transferase (OGT) catalyzes the addition while O-GlcNAcase (OGA) helps the removal of GlcNAc. O-GlcNAcylation modifies protein functions; therefore, dysregulation of O-GlcNAcylation affects cell physiology and contributes to pathogenesis. To maintain homeostasis of cellular O-GlcNAcylation, there exists feedback regulation of OGT and OGA expression responding to fluctuations of O-GlcNAc levels; yet, little is known about the molecular mechanisms involved. In this study, we investigated the O-GlcNAc-feedback regulation of OGT and OGA expression in lung cancer cells. Results suggest that, upon alterations in O-GlcNAcylation, the regulation of OGA expression occurs at the mRNA level and likely involves epigenetic mechanisms, while modulation of OGT expression is through translation control. Further analyses revealed that the eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) contributes to the downregulation of OGT induced by hyper-O-GlcNAcylation; the S5A/S6A O-GlcNAcylation-site mutant of 4E-BP1 cannot support this regulation, suggesting an important role of O-GlcNAcylation. The results provide additional insight into the molecular mechanisms through which cells may fine-tune intracellular O-GlcNAc levels to maintain homeostasis.

A translation repressor, 4E-BP1, regulates the triglyceride level in rat liver during protein deprivation

2020 ◽  
Vol 318 (5) ◽  
pp. E636-E645
Author(s):  
Yuka Toyoshima ◽  
Fumiaki Yoshizawa ◽  
Reiko Tokita ◽  
Yusuke Taguchi ◽  
Shin-Ichiro Takahashi ◽  
...  
Keyword(s):  
Rat Liver ◽  
Molecular Mechanisms ◽  
Mrna Level ◽  
Translation Initiation Factor ◽  
Protein Diet ◽  
Initiation Factor ◽  
Low Protein Diet ◽  
Acid Oxidation ◽  
Protein Deprivation ◽  
Low Protein

Protein deprivation has been shown to induce fatty liver in humans and animals, but the molecular mechanisms underlying such induction are largely unknown. Our previous studies have shown that a low-protein diet increases eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) protein and triglyceride (TG) levels in rat liver. 4E-BP1 is known to repress translation by binding to eIF4E. There is also evidence indicating that 4E-BP1 regulates lipid metabolism. Here, we examined the role of 4E-BP1 on TG accumulation in the livers of rats under protein deprivation. The low-protein diet rapidly increased the hepatic 4E-BP1 mRNA level within 1 day, followed by the induction of hepatic TG accumulation. The knockdown of hepatic 4E-BP1 attenuated the TG accumulation in rat liver induced by the low-protein diet. 4E-BP1 knockdown also increased the protein level of carnitine palmitoyltransferase 1A (CPT1A), a regulator of fatty acid oxidation, in the liver of rats fed a low-protein diet. These results indicate that a low-protein diet increases the amount of 4E-BP1, leading to TG accumulation in rat liver. We thus conclude that 4E-BP1 plays an important role in inducing hepatic steatosis under protein deprivation.

scholarly journals Bufei Qingyu Granules Inhibit the Development of Systemic Sclerosis via Notch-1/Jagged-2 Signaling Pathway

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Minhui Su ◽  
Fang Tian ◽  
Bingchen Ouyang ◽  
Xiaoyu Wu ◽  
Feng Guo ◽  
...  
Keyword(s):  
Systemic Sclerosis ◽  
Notch Signaling ◽  
Signaling Pathway ◽  
Molecular Mechanisms ◽  
Smooth Muscle Actin ◽  
Notch Signaling Pathway ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Notch 1 ◽  
Bioinformatics Analyses

Systemic sclerosis (SSc) is a rare chronic autoimmune disorder, mainly characterized by skin sclerosis. In this study, Bufei Qingyu Granules (BQG), a Chinese herbal formula, was used to treat SSc. To better understand the effects and molecular mechanisms of BQG, we successfully established a Bleomycin- (BLM-) induced SSc mouse model, and the mice were treated by BQG. Meanwhile, transcriptomic and bioinformatics analyses were conducted on those samples. As a result, we visually showed that BQG ameliorated the overall health of mice, including body weight, spleen, and thymus index. Thus, it also significantly alleviated inflammation presented by Chemokine (C-X-C motif) ligand 2 (Cxcl2), vasculopathy characterized by α-smooth muscle actin (α-SMA), and fibrotic changes elaborated by not only pathological images, but also the hydroxyproline (HYP) content. After testing by transcriptomic analysis, Cxcl2, Synaptosomal-associated protein 25 (Snap25), and Eukaryotic translation initiation factor 3, and subunit J2 (Eif3j2) which were differentially expressed genes, were verified, so that the data were credible. We further found that BQG could regulate Notch signaling pathway by significantly decreasing both mRNA and protein expression levels of Notch-1 and Jagged-2. Hence, this study demonstrated that BQG could ameliorate the sclerotic skin in mice model involved in inflammation, vascular changes, and fibrosis effects, which was partly mediated by Notch signaling pathway.

scholarly journals Direct Interaction Between the Rice yellow mottle virus (RYMV) VPg and the Central Domain of the Rice eIF(iso)4G1 Factor Correlates with Rice Susceptibility and RYMV Virulence

2010 ◽  
Vol 23 (11) ◽  
pp. 1506-1513 ◽  
Author(s):  
Eugénie Hébrard ◽  
Nils Poulicard ◽  
Clément Gérard ◽  
Oumar Traoré ◽  
Hui-Chen Wu ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Direct Interaction ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Mottle Virus ◽  
Rice Yellow Mottle Virus ◽  
Recessive Resistance ◽  
In Planta ◽  
Central Domain ◽  
Yellow Mottle

The adaptation of Rice yellow mottle virus (RYMV) to recessive resistance mediated by the rymv1-2 allele has been reported as a model to study the emergence and evolution of virulent variants. The resistance and virulence factors have been identified as eukaryotic translation initiation factor eIF(iso)4G1 and viral genome–linked protein (VPg), respectively, but the molecular mechanisms involved in their interaction are still unknown. In this study, we demonstrated a direct interaction between RYMV VPg and the central domain of rice eIF(iso)4G1 both in vitro, using recombinant proteins, and in vivo, using a yeast two-hybrid assay. Insertion of the E309K mutation in eIF(iso)4G1, conferring resistance in planta, strongly diminished the interaction with avirulent VPg. The efficiency of the major virulence mutations at restoring the interaction with the resistance protein was assessed. Our results explain the prevalence of virulence mutations fixed during experimental evolution studies and are consistent with the respective viral RNA accumulation levels of avirulent and virulent isolates. Our results also explain the origin of the residual multiplication of wild-type isolates in rymv1-2–resistant plants and the role of genetic context in the poor adaptability of the S2/S3 strain. Finally, the strategies of RYMV and members of family Potyviridae to overcome recessive resistance were compared.

scholarly journals The Cap-Binding Complex CBC and the Eukaryotic Translation Factor eIF4E: Co-Conspirators in Cap-Dependent RNA Maturation and Translation

Cancers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 6185
Author(s):  
Jean-Clement Mars ◽  
Mehdi Ghram ◽  
Biljana Culjkovic-Kraljacic ◽  
Katherine L. B. Borden
Keyword(s):  
Nuclear Export ◽  
Mammalian Cells ◽  
Physical Nature ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cell Physiology ◽  
Eukaryotic Translation ◽  
Protein Levels ◽  
Cap Binding Complex ◽  
Rna Maturation

The translation of RNA into protein is a dynamic process which is heavily regulated during normal cell physiology and can be dysregulated in human malignancies. Its dysregulation can impact selected groups of RNAs, modifying protein levels independently of transcription. Integral to their suitability for translation, RNAs undergo a series of maturation steps including the addition of the m7G cap on the 5′ end of RNAs, splicing, as well as cleavage and polyadenylation (CPA). Importantly, each of these steps can be coopted to modify the transcript signal. Factors that bind the m7G cap escort these RNAs through different steps of maturation and thus govern the physical nature of the final transcript product presented to the translation machinery. Here, we describe these steps and how the major m7G cap-binding factors in mammalian cells, the cap binding complex (CBC) and the eukaryotic translation initiation factor eIF4E, are positioned to chaperone transcripts through RNA maturation, nuclear export, and translation in a transcript-specific manner. To conceptualize a framework for the flow and integration of this genetic information, we discuss RNA maturation models and how these integrate with translation. Finally, we discuss how these processes can be coopted by cancer cells and means to target these in malignancy.

scholarly journals eIF6 Promotes the Malignant Progression of Human Hepatocellular Carcinoma via the mTOR Signaling Pathway

2020 ◽  
Author(s):  
Liping Sun ◽  
Shuguang Liu ◽  
Xiaopai Wang ◽  
Xuefeng Zheng ◽  
Ya Chen ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Signaling Pathway ◽  
Prognostic Value ◽  
Molecular Mechanisms ◽  
Protein Translation ◽  
Translation Initiation Factor ◽  
Gene Set Enrichment Analysis ◽  
The Cancer Genome Atlas ◽  
Initiation Factor ◽  
Hcc Cells

Abstract Background Eukaryotic translation initiation factor 6 (eIF6) has a crucial function in the maturation of 60S ribosomal subunits, and it controls the initiation of protein translation. Although emerging studies indicate that eIF6 is aberrantly expressed in various types of cancers, the functions and underlying molecular mechanisms of eIF6 in the pathological progression of hepatocellular carcinoma (HCC) remain unclear. This study aimed to evaluate the potential diagnostic and prognostic value of eIF6 in patients with HCC. Methods HCC samples enrolled from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and our cohort were used to explore the role and mechanism of eIF6 in HCC. The diagnostic power of eIF6 was verified by receiver operating characteristic curve (ROC) analysis and its prognostic value was assessed by Kaplan-Meier analysis, and then related biological functions of eIF6 were determined in vitro and in vivo cancer models. In addition, potential molecular mechanism of eIF6 in HCC was unveiled by the gene set enrichment analysis and western blot assay. Results We demonstrated that eIF6 expression was markedly increased in HCC, and elevated eIF6 expression correlated with pathological progression of HCC. Besides, eIF6 served as not only a new diagnostic biomarker but also an independent risk factor for OS in HCC patients. Functional studies indicated that the deletion of eIF6 displayed tumor-suppressor activity in HCC cells. Furthermore, we found that eIF6 could activate the mTOR-related signaling pathway and regulate the expression level of its target genes, such as CCND1, CDK4, CDK6, MYC, CASP3 and CTNNBL1, and these activities promoted proliferation and invasion of HCC cells. Conclusions The findings of this study provided a novel basis for understanding the potential role of eIF6 in promoting tumor growth and invasion, and exploited a promising strategy for improving diagnosis and prognosis of HCC.

YAP-Induced Endothelial-Mesenchymal Transition in Oral Submucous Fibrosis

2019 ◽  
Vol 98 (8) ◽  
pp. 920-929 ◽  
Author(s):  
J. Li ◽  
M. Yao ◽  
X. Zhu ◽  
Q. Li ◽  
J. He ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Oral Submucous Fibrosis ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Mesenchymal Transition ◽  
Eukaryotic Translation ◽  
Initiation Factor 2 ◽  
Potentially Malignant ◽  
Submucous Fibrosis ◽  
Mesenchymal Transformation

Oral submucous fibrosis (OSF) is a potentially malignant disorder. Current studies have shown that chewing areca nut is considered the main cause of OSF, and endothelial-mesenchymal transformation (EndMT) participates in the occurrence and development of the fibrotic lesion. However, the specific molecular mechanisms and treatments remain unclear. Here, we report the mechanism of arecoline-induced EndMT and the importance of this mechanism in OSF, and we also identify potential therapeutics for decreasing OSF incidence. We demonstrate the overexpression of Yes-associated protein (YAP) in human samples and that it was significantly associated with OSF pathologic stage. Arecoline activated YAP by increasing reactive oxygen species levels and inducing the PERK pathway (eukaryotic translation initiation factor 2 alpha kinase 3), resulting in the initiation of EndMT and leading to OSF. Verteporfin, a YAP–TEA domain pathway inhibitor, suppressed EndMT and decreased collagen accumulation, resulting in the alleviation of OSF in mice. These data indicate that arecoline regulates the activity of YAP and highlight an alternative method for treating OSF.

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

2009 ◽  
Vol 29 (15) ◽  
pp. 4295-4307 ◽  
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.

scholarly journals Post-translational modification of the protein-synthesis initiation factor eIF-4D by spermidine in rat hepatoma cells

1986 ◽  
Vol 239 (2) ◽  
pp. 379-386 ◽  
Author(s):  
E W Gerner ◽  
P S Mamont ◽  
A Bernhardt ◽  
M Siat
Keyword(s):  
Growth Rates ◽  
Exponential Phase ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Polyamine Metabolism ◽  
Synthesis Rate ◽  
Post Translational Modification ◽  
Irreversible Inhibitor ◽  
Rat Hepatoma ◽  
In Cells

The rates of synthesis and turnover of the rare amino acid hypusine [N6-(4-amino-2-hydroxybutyl)-2,6-diaminohexanoic acid] in protein were studied in relationship to polyamine metabolism and growth rates in rat hepatoma tissue-culture (HTC) cells. Hypusine is selectively formed in the eukaryotic translation initiation factor eIF-4D, by a post-translational mechanism involving spermidine [Cooper, Park, Folk, Safer & Braverman (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 1854-1857]. The half-life of the hypusine-containing protein was longer than 24 h. In cells whose intracellular spermidine pools had been initially depleted, by using DL-alpha-difluoromethylornithine (DFMO), maximum synthesis rates of hypusine in protein were 5-10 times higher, on restoration of endogenous spermidine contents by exogenous addition, than those observed in untreated exponential-phase cultures. In cells pretreated with DFMO, the rate of hypusine synthesis was constant for up to 1 h after the addition of 5 microM-spermidine, whereas endogenous spermidine contents varied from less than 1 to more than 10 nmol/mg of protein. However, the overall amount of hypusine formed, during the first 1 h after the addition of various concentrations of spermidine (0.05-10 microM) to the culture medium, was markedly dependent on the final endogenous spermidine content achieved at the end of the 1 h measurement interval. Early in exponential-phase growth, protein-bound hypusine was synthesized at a rate of 1-2 pmol/h per mg of protein. This rate decreased to less than 0.5 pmol/h per mg of protein when cell growth rates decreased as cultures reached high cell densities. Analysis of the polyamine substrate specificity for hypusine formation showed that N1-acetylspermidine did not compete with spermidine in the reaction, nor did N1-(buta-2,3-dienyl)-N2-methylbutane-1,4-diamine, and irreversible inhibitor of polyamine oxidase, block the reaction. On the basis of comparative radiolabelling experiments, spermine was either a poor substrate, or not a substrate, for hypusine formation. These results confirm that spermidine is the likely precursor of the aminohydroxybutyl moiety of hypusine, and show that overall hypusine formation, but not necessarily the synthesis rate, is dependent on the endogenous spermidine concentration, especially under conditions where spermidine concentrations are initially low, as is the case after DFMO treatment, and then increase.

scholarly journals The O-GlcNAc transferase OGT is a conserved and essential regulator of the cellular and organismal response to hypertonic stress

2020 ◽  
Author(s):  
Sarel J. Urso ◽  
Marcella Comly ◽  
John A. Hanover ◽  
Todd Lamitina
Keyword(s):  
Stress Response ◽  
Cell Volume ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Cell Physiology ◽  
Hypertonic Stress ◽  
C Elegans ◽  
Intracellular Proteins ◽  
Molecular Functions ◽  
Glcnac Transferase

AbstractThe conserved O-GlcNAc transferase OGT O-GlcNAcylates serine and threonine residues of intracellular proteins to regulate their function. OGT is required for viability in mammalian cells, but its specific roles in cellular physiology are poorly understood. Here we describe a conserved requirement for OGT in an essential aspect of cell physiology: the hypertonic stress response. Through a forward genetic screen in Caenorhabditis elegans, we discovered OGT is acutely required for osmoprotective protein expression and adaptation to hypertonic stress. Gene expression analysis shows that ogt-1 functions through a post-transcriptional mechanism. Human OGT partially rescues the C. elegans phenotypes, suggesting that the osmoregulatory functions of OGT are ancient. Intriguingly, mutations that ablate O-GlcNAcylation activity in either human or C. elegans OGT rescue the hypertonic stress response phenotype. Our findings are among the first to demonstrate a specific physiological role for OGT at the organismal level and demonstrate that OGT engages in important molecular functions outside of its well described roles in post-translational O-GlcNAcylation of intracellular proteins.Author SummaryThe ability to sense and adapt to changes in the environment is an essential feature of cellular life. Changes in environmental salt and water concentrations can rapidly cause cell volume swelling or shrinkage and, if left unchecked, will lead to cell and organismal death. All organisms have developed similar physiological strategies for maintaining cell volume. However, the molecular mechanisms that control these physiological outputs are not well understood in animals. Using unbiased genetic screening in C. elegans, we discovered that a highly conserved enzyme called O-GlcNAc transferase (OGT) is essential for regulating physiological responses to increased environmental solute levels. A human form of OGT can functionally substitute for worm OGT, showing that this role is conserved across evolution. Surprisingly, the only known enzymatic activity of OGT was not required for this role, suggesting this enzyme has important undescribed molecular functions. Our studies reveal a new animal-specific role for OGT in the response to osmotic stress and show that C. elegans is an important model for defining the conserved molecular mechanisms that respond to alterations in cell volume.

scholarly journals Rotavirus NSP3 Is a Translational Surrogate of the Poly(A) Binding Protein-Poly(A) Complex

2015 ◽  
Vol 89 (17) ◽  
pp. 8773-8782 ◽  
Author(s):  
Matthieu Gratia ◽  
Emeline Sarot ◽  
Patrice Vende ◽  
Annie Charpilienne ◽  
Carolina Hilma Baron ◽  
...  
Keyword(s):  
Binding Protein ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cell Physiology ◽  
Transfected Cells ◽  
Rotavirus Infection ◽  
Cellular Translation ◽  
Infected Cells ◽  
Polyadenylated Mrna

ABSTRACTThrough its interaction with the 5′ translation initiation factor eIF4G, poly(A) binding protein (PABP) facilitates the translation of 5′-capped and 3′-poly(A)-tailed mRNAs. Rotavirus mRNAs are capped but not polyadenylated, instead terminating in a 3′ GACC motif that is recognized by the viral protein NSP3, which competes with PABP for eIF4G binding. Upon rotavirus infection, viral, GACC-tailed mRNAs are efficiently translated, while host poly(A)-tailed mRNA translation is, in contrast, severely impaired. To explore the roles of NSP3 in these two opposing events, the translational capabilities of three capped mRNAs, distinguished by either a GACC, a poly(A), or a non-GACC and nonpoly(A) 3′ end, have been monitored after electroporation of cells expressing all rotavirus proteins (infected cells) or only NSP3 (stably or transiently transfected cells). In infected cells, we found that the magnitudes of translation induction (GACC-tailed mRNA) and translation reduction [poly(A)-tailed mRNA] both depended on the rotavirus strain used but that translation reduction not genetically linked to NSP3. In transfected cells, even a small amount of NSP3 was sufficient to dramatically enhance GACC-tailed mRNA translation and, surprisingly, to slightly favor the translation of both poly(A)- and nonpoly(A)-tailed mRNAs, likely by stabilizing the eIF4E-eIF4G interaction. These data suggest that NSP3 is a translational surrogate of the PABP-poly(A) complex; therefore, it cannot by itself be responsible for inhibiting the translation of host poly(A)-tailed mRNAs upon rotavirus infection.IMPORTANCETo control host cell physiology and to circumvent innate immunity, many viruses have evolved powerful mechanisms aimed at inhibiting host mRNA translation while stimulating translation of their own mRNAs. How rotavirus tackles this challenge is still a matter of debate. Using rotavirus-infected cells, we show that the magnitude of cellular poly(A) mRNA translation differs with respect to rotavirus strains but is not genetically linked to NSP3. Using cells expressing rotavirus NSP3, we show that NSP3 alone not only dramatically enhances rotavirus-like mRNA translation but also enhances poly(A) mRNA translation rather than inhibiting it, likely by stabilizing the eIF4E-eIF4G complex. Thus, the inhibition of cellular polyadenylated mRNA translation during rotavirus infection cannot be attributed solely to NSP3 and is more likely the result of global competition between viral and host mRNAs for the cellular translation machinery.

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