scholarly journals IFIT3 and IFIT2/3 promote IFIT1-mediated translation inhibition by enhancing binding to non-self RNA

2018 ◽  
Author(s):  
Renata C Fleith ◽  
Harriet V Mears ◽  
Edward Emmott ◽  
Stephen C Graham ◽  
Daniel S Mansur ◽  
...  
Keyword(s):  
Translation Initiation Factor ◽  
Site Directed Mutagenesis ◽  
Initiation Factor ◽  
Tetratricopeptide Repeats ◽  
Translation Inhibition ◽  
Eukaryotic Translation ◽  
Binding Interface ◽  
Molecular Aspects ◽  
And Function

AbstractInterferon-induced proteins with tetratricopeptide repeats (IFITs) are highly expressed during the cell-intrinsic immune response to viral infection. IFIT1 inhibits translation by binding directly to the 5′ end of foreign RNAs, particularly those with non-self cap structures, precluding the recruitment of the cap-binding eukaryotic translation initiation factor 4F and subsequent 40S recruitment. Interaction of different IFIT family members is well described, but little is known of the molecular basis of IFIT association or its impact on function. Here, we reconstituted different complexes of IFIT1, IFIT2 and IFIT3 in vitro, which enabled us to reveal critical aspects of IFIT complex assembly. IFIT1 interacts rapidly and strongly with IFIT3 forming a stable heterotetramer. IFIT2 and IFIT3 homodimers dissociate to form a more stable heterodimer that associates with IFIT1, forming an IFIT1:IFIT2:IFIT3 trimer. Site-directed mutagenesis revealed a C-terminal ‘YxxxL’ motif in IFIT1 that mediates its association with IFIT3. Using various reporter mRNAs, we demonstrate for the first time that IFIT3 stabilises IFIT1 binding to cap0-mRNA and enhances its translation inhibition activity. Disrupting the binding interface between IFIT1 and IFIT3 abrogated this enhancement. This work reveals molecular aspects of IFIT assembly and provides an important ‘missing link’ between IFIT interaction and function.

scholarly journals Dual modulation of Ras-Mnk and PI3K-AKT-mTOR pathways: A Novel c-FLIP inhibitory mechanism of 3-AWA mediated translational attenuation through dephosphorylation of eIF4E

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Reyaz ur Rasool ◽  
Bilal Rah ◽  
Hina Amin ◽  
Debasis Nayak ◽  
Souneek Chakraborty ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Cell Cycle Progression ◽  
De Novo ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Apoptosis Resistance ◽  
Nih3t3 Cells ◽  
Eukaryotic Translation ◽  
Underlying Mechanisms

Abstract The eukaryotic translation initiation factor 4E (eIF4E) is considered as a key survival protein involved in cell cycle progression, transformation and apoptosis resistance. Herein, we demonstrate that medicinal plant derivative 3-AWA (from Withaferin A) suppressed the proliferation and metastasis of CaP cells through abrogation of eIF4E activation and expression via c-FLIP dependent mechanism. This translational attenuation prevents the de novo synthesis of major players of metastatic cascades viz. c-FLIP, c-Myc and cyclin D1. Moreover, the suppression of c-FLIP due to inhibition of translation initiation complex by 3-AWA enhanced FAS trafficking, BID and caspase 8 cleavage. Further ectopically restored c-Myc and GFP-HRas mediated activation of eIF4E was reduced by 3-AWA in transformed NIH3T3 cells. Detailed underlying mechanisms revealed that 3-AWA inhibited Ras-Mnk and PI3-AKT-mTOR, two major pathways through which eIF4E converges upon eIF4F hub. In addition to in vitro studies, we confirmed that 3-AWA efficiently suppressed tumor growth and metastasis in different mouse models. Given that 3-AWA inhibits c-FLIP through abrogation of translation initiation by co-targeting mTOR and Mnk-eIF4E, it (3-AWA) can be exploited as a lead pharmacophore for promising anti-cancer therapeutic development.

scholarly journals Binding of eukaryotic translation initiation factor 4E (eIF4E) to eIF4G represses translation of uncapped mRNA.

1997 ◽  
Vol 17 (12) ◽  
pp. 6876-6886 ◽  
Author(s):  
S Z Tarun ◽  
A B Sachs
Keyword(s):  
Translation Initiation ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Stimulation Of

mRNA translation in crude extracts from the yeast Saccharomyces cerevisiae is stimulated by the cap structure and the poly(A) tail through the binding of the cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) and the poly(A) tail-binding protein Pab1p. These proteins also bind to the translation initiation factor eIF4G and thereby link the mRNA to the general translational apparatus. In contrast, uncapped, poly(A)-deficient mRNA is translated poorly in yeast extracts, in part because of the absence of eIF4E and Pab1p binding sites on the mRNA. Here, we report that uncapped-mRNA translation is also repressed in yeast extracts due to the binding of eIF4E to eIF4G. Specifically, we find that mutations which weaken the eIF4E binding site on the yeast eIF4G proteins Tif4631p and Tif4632p lead to temperature-sensitive growth in vivo and the stimulation of uncapped-mRNA translation in vitro. A mutation in eIF4E which disturbs its ability to interact with eIF4G also leads to a stimulation of uncapped-mRNA translation in vitro. Finally, overexpression of eIF4E in vivo or the addition of excess eIF4E in vitro reverses these effects of the mutations. These data support the hypothesis that the eIF4G protein can efficiently stimulate translation of exogenous uncapped mRNA in extracts but is prevented from doing so as a result of its association with eIF4E. They also suggest that some mRNAs may be translationally regulated in vivo in response to the amount of free eIF4G in the cell.

scholarly journals Coupled Release of Eukaryotic Translation Initiation Factors 5B and 1A from 80S Ribosomes following Subunit Joining

2007 ◽  
Vol 27 (6) ◽  
pp. 2384-2397 ◽  
Author(s):  
Jeanne M. Fringer ◽  
Michael G. Acker ◽  
Christie A. Fekete ◽  
Jon R. Lorsch ◽  
Thomas E. Dever
Keyword(s):  
Translation Initiation ◽  
Ribosomal Subunit ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Cell Extracts ◽  
Eukaryotic Translation Initiation ◽  
Subunit Joining

ABSTRACT The translation initiation GTPase eukaryotic translation initiation factor 5B (eIF5B) binds to the factor eIF1A and catalyzes ribosomal subunit joining in vitro. We show that rapid depletion of eIF5B in Saccharomyces cerevisiae results in the accumulation of eIF1A and mRNA on 40S subunits in vivo, consistent with a defect in subunit joining. Substituting Ala for the last five residues in eIF1A (eIF1A-5A) impairs eIF5B binding to eIF1A in cell extracts and to 40S complexes in vivo. Consistently, overexpression of eIF5B suppresses the growth and translation initiation defects in yeast expressing eIF1A-5A, indicating that eIF1A helps recruit eIF5B to the 40S subunit prior to subunit joining. The GTPase-deficient eIF5B-T439A mutant accumulated on 80S complexes in vivo and was retained along with eIF1A on 80S complexes formed in vitro. Likewise, eIF5B and eIF1A remained associated with 80S complexes formed in the presence of nonhydrolyzable GDPNP, whereas these factors were released from the 80S complexes in assays containing GTP. We propose that eIF1A facilitates the binding of eIF5B to the 40S subunit to promote subunit joining. Following 80S complex formation, GTP hydrolysis by eIF5B enables the release of both eIF5B and eIF1A, and the ribosome enters the elongation phase of protein synthesis.

scholarly journals Implications of the Use of Eukaryotic Translation Initiation Factor 5A (eIF5A) for Prognosis and Treatment of Hepatocellular Carcinoma

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Felix H. Shek ◽  
Sarwat Fatima ◽  
Nikki P. Lee
Keyword(s):  
Hepatocellular Carcinoma ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Initiation Of Translation ◽  
Eukaryotic Translation Initiation ◽  
Hcc Cells

Hepatocellular carcinoma (HCC) is a primary liver malignancy and accounts for most of the total liver cancer cases. Lack of treatment options and late diagnosis contribute to high mortality rate of HCC. In eukaryotes, translation of messenger RNA (mRNA) to protein is a key process in protein biosynthesis in which initiation of translation involves interaction of different eukaryotic translation initiation factors (eIFs), ribosome subunits and mRNAs. Eukaryotic translation initiation factor 5A (eIF5A) is one of the eIFs involved in translation initiation and eIF5A2, one of its isoforms, is upregulated in various cancers including HCC as a result of chromosomal instability, where it resides. In HCC, eIF5A2 expression is associated with adverse prognosis such as presence of tumor metastasis and venous infiltration. Based on eIF5A2 functional studies, suppressing eIF5A2 expression by short interfering RNA alleviates the tumorigenic properties of HCC cellsin vitrowhile ectopic expression of eIF5A2 enhances the aggressiveness of HCC cellsin vivoandin vitroby inducing epithelial-mesenchymal transition. In conclusion, eIF5A2 is a potential prognostic marker as well as a therapeutic target for HCC.

scholarly journals The role of hypusine depletion in cytostasis induced by S-adenosyl-l-methionine decarboxylase inhibition: new evidence provided by 1-methylspermidine and 1,12-dimethylspermine

1994 ◽  
Vol 303 (2) ◽  
pp. 363-368 ◽  
Author(s):  
T L Byers ◽  
J R Lakanen ◽  
J K Coward ◽  
A E Pegg
Keyword(s):  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Decarboxylase Inhibitor ◽  
Deoxyhypusine Synthase ◽  
Eukaryotic Translation ◽  
Polyamine Analogues ◽  
L1210 Cells ◽  
Eukaryotic Translation Initiation ◽  
New Evidence

The abilities of the natural polyamines, spermidine and spermine, and of the synthetic analogues, 1-methylspermidine and 1,12-dimethylspermine, to reverse the effects of the S-adenosyl-L-methionine decarboxylase inhibitor 5′-([(Z)-4-aminobut-2-enyl]methylamino)-5′-deoxyadenosine (AbeAdo) on L1210-cell growth were studied. L1210 cells were exposed to AbeAdo for 12 days to induce cytostasis and then exposed to spermidine, spermine, 1-methylspermidine or 1,12-dimethylspermine in the continued presence of AbeAdo. AbeAdo-induced cytostasis was overcome by the natural polyamines, spermidine and spermine. The cytostasis was also reversed by 1-methylspermidine. 1,12-Dimethylspermine had no effect on the AbeAdo-induced cytostasis of chronically treated cells, although it was active in permitting growth of cells treated with the ornithine decarboxylase inhibitor, alpha-difluoromethylornithine. The initial 12-day exposure to AbeAdo elevated intracellular putrescine levels, depleted intracellular spermidine and spermine, and resulted in the accumulation of unmodified eukaryotic translation initiation factor 5A (eIF-5A). Exposure of these cells to exogenous spermidine, which is the natural substrate for deoxyhypusine synthase, resulted in a decrease in the unmodified eIF-5A content. 1-Methylspermidine, which was found to be a substrate of deoxyhypusine synthase in vitro, also decreased the levels of unmodified eIF-5A in the AbeAdo-treated cells. Although spermine is not a substrate of deoxyhypusine synthase, spermine was converted into spermidine in the L1210 cells, and spermine addition to AbeAdo-treated cells resulted in the appearance of both intracellular spermine and spermidine and in the decrease in unmodified eIF-5A. Exogenous 1,12-dimethylspermine, which was not metabolized to spermine or to 1-methylspermidine and was not a substrate of deoxyhypusine synthase in vitro, did not decrease levels of unmodified eIF-5A. The finding that AbeAdo-induced cytostasis was only reversed by polyamines and polyamine analogues that result in the formation of hypusine or an analogue in eIF-5A is consistent with the hypothesis [Byers, Wiest, Wechter and Pegg (1993) Biochem. J. 290, 115-121] that AbeAdo-induced cytostasis is due to the depletion of the hypusine-containing form of eIF-5A, which is secondary to the depletion of spermidine by inhibition of S-adenosyl-L-methionine decarboxylase.

scholarly journals Homocysteine induces melanocytes apoptosis via PERK–eIF2α–CHOP pathway in vitiligo

2020 ◽  
Vol 134 (10) ◽  
pp. 1127-1141 ◽  
Author(s):  
Jiaxi Chen ◽  
Tongtian Zhuang ◽  
Jianru Chen ◽  
Yangzi Tian ◽  
Xiuli Yi ◽  
...  
Keyword(s):  
Folic Acid ◽  
Stress Protein ◽  
Folic Acid Supplementation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Homologous Protein ◽  
Apoptotic Effect ◽  
Induced Apoptosis

Abstract Vitiligo is a depigmentation disorder that develops as a result of the progressive disappearance of epidermal melanocytes. The elevated level of amino acid metabolite homocysteine (Hcy) has been identified as circulating marker of oxidative stress and known as a risk factor for vitiligo. However, the mechanism underlying Hcy-regulated melanocytic destruction is currently unknown. The present study aims to elucidate the effect of Hcy on melanocytic destruction and its involvement in the pathogenesis of vitiligo. Our results showed that Hcy level was significantly elevated in the serum of progressive vitiligo patients. Notably, Hcy induced cell apoptosis in melanocytes via activating reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress protein kinase RNA-like ER kinase (PERK)–eukaryotic translation initiation factor 2α (eIF2α)–C/EBP homologous protein (CHOP) pathway. More importantly, folic acid, functioning in the transformation of Hcy, could lower the intracellular Hcy level and further reverse the apoptotic effect of Hcy on melanocytes. Additionally, Hcy disrupted melanogenesis whereas folic acid supplementation could reverse the melanogenesis defect induced by Hcy in melanocytes. Taken together, Hcy is highly increased in vitiligo patients at progressive stage, and our in vitro studies revealed that folic acid could protect melanocytes from Hcy-induced apoptosis and melanin synthesis inhibition, indicating folic acid as a potential benefit agent for patients with progressive vitiligo.

scholarly journals Cytoplasmic eIF6 promotes OSCC malignant behavior through AKT pathway

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Zechen Zhao ◽  
Weiming Chu ◽  
Yang Zheng ◽  
Chao Wang ◽  
Yuemei Yang ◽  
...  
Keyword(s):  
Western Blot ◽  
Direct Interaction ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Migration And Invasion ◽  
Eukaryotic Translation ◽  
Mesenchymal Transformation

Abstract Background Eukaryotic translation initiation factor 6 (eIF6), also known as integrin β4 binding protein, is involved in ribosome formation and mRNA translation, acting as an anti-association factor. It is also essential for the growth and reproduction of cells, including tumor cells. Yet, its role in oral squamous cell carcinoma (OSCC) remains unclear. Methods The expression characteristics of eIF6 in 233 samples were comprehensively analyzed by immunohistochemical staining (IHC). Effects of eIF6 over-expression and knockdown on cell proliferation, migration and invasion were determined by CCK-8, wound healing and Transwell assays. Western blot, immunofluorescence (IF) and co-immunoprecipitation (co-IP) were performed for mechanical verification. Results We found that cytoplasmic eIF6 was abnormally highly expressed in OSCC tissues, and its expression was associated with tumor size and the clinical grade. Amplification of eIF6 promoted the growth, migration and invasion capabilities of OSCC cell lines in vitro and tumor growth in vivo. Through Western blot analysis, we further discovered that eIF6 significantly promotes epithelial-mesenchymal transformation (EMT) in OSCC cells, while depletion of eIF6 can reverse this process. Mechanistically, eIF6 promoted tumor progression by activating the AKT signaling pathway. By performing co-immunoprecipitation, we discovered a direct interaction between endogenous eIF6 and AKT protein in the cytoplasm. Conclusion These results demonstrated that eIF6 could be a new therapeutic target in OSCC, thus providing a new basis for the prognosis of OSCC patients in the future.

scholarly journals Knockdown of EIF3H inhibits the development and progression of pancreatic cancer by regulating cell proliferation and apoptosis in vitro

2022 ◽  
Vol 67 (4) ◽  
pp. 83-90
Author(s):  
Yuqiang Shan ◽  
Wencheng Kong ◽  
Akao Zhu ◽  
Jiangtao Li ◽  
Huicheng Jin ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cancer Cells ◽  
Critical Role ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Loss Of Function ◽  
Eukaryotic Translation ◽  
Proliferation Capacity ◽  
Pancreatic Cancer Cells

Nowadays, pancreatic cancer has been recognized as one of the most fatal malignancies worldwide, the molecular mechanism of which is still not fully understood. In this study, we aimed to uncover the fundamental functions of the eukaryotic translation initiation factor 3H subunit (EIF3H) in the development and progression of pancreatic cancer. Firstly, the results of immunohistochemical (IHC) staining revealed that EIF3H was highly expressed in pancreatic cancer. Moreover, lentiviruses were used to deliver shRNAs into pancreatic cancer cells for silencing EIF3H. Furthermore, the loss-of-function assays demonstrated that knockdown of EIF3H could inhibit the progression of pancreatic cancer cells by reducing proliferation capacity, promoting apoptosis, arresting cell cycle in G2 and suppressing cell migration. In summary, EIF3H may play a critical role in the development and progression of pancreatic cancer, which possesses the potential to act as a therapeutic target for pancreatic cancer treatment.

scholarly journals Interaction in vitro between the proteinase of Tomato ringspot virus (genus Nepovirus) and the eukaryotic translation initiation factor iso4E from Arabidopsis thaliana

2002 ◽  
Vol 83 (8) ◽  
pp. 2085-2089 ◽  
Author(s):  
Simon Léonard ◽  
Joan Chisholm ◽  
Jean-François Laliberté ◽  
Hélène Sanfaçon
Keyword(s):  
Virus Genome ◽  
Translation Initiation Factor ◽  
Ringspot Virus ◽  
Initiation Factor ◽  
Virus Infectivity ◽  
Eukaryotic Translation ◽  
Tomato Ringspot Virus ◽  
Cellular Mrnas ◽  
Eukaryotic Translation Initiation

Eukaryotic initiation factor eIF(iso)4E binds to the cap structure of mRNAs leading to assembly of the translation complex. This factor also interacts with the potyvirus VPg and this interaction has been correlated with virus infectivity. In this study, we show an interaction between eIF(iso)4E and the proteinase (Pro) of a nepovirus (Tomato ringspot virus; ToRSV) in vitro. The ToRSV VPg did not interact with eIF(iso)4E although its presence on the VPg-Pro precursor increased the binding affinity of Pro for the initiation factor. A major determinant of the interaction was mapped to the first 93 residues of Pro. Formation of the complex was inhibited by addition of m7GTP (a cap analogue), suggesting that Pro-containing molecules compete with cellular mRNAs for eIF(iso)4E binding. The possible implications of this interaction for translation and/or replication of the virus genome are discussed.

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