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Esophageal squamous cell carcinoma (ESCC) is one of most prevalent cancers worldwide, especially in China. Lacking in depth mechanism study, effective targets and therapeutics are desperately needed in the clinic. RNA-binding proteins (RBPs) mediate the localization, stability, and translation of the target transcripts and fine-tune the physiological functions of the proteins encoded. Bioinformatics analysis revealed that IGF2BPs were highly expressed in ESCC tissues and at least participated in the regulation of cell proliferation of ESCC cells. Biological researches demonstrated that IGF2BP2 promoted the cell proliferation, migration and invasion of ESCC KYSE30 and KYSE450 cells. IGF2BP2 could bind to EIF4A1 mRNA by recognition of m6A sites and enhanced translation of EIF4A1. IGF2BPs, as m6A reader, IGF2BPs were oncogenic genes in ESCC by regulating the expression of EIF4A1 through m6A sites. IGF2BP2, EIF4A1 and their targets could serve as potential biomarkers and therapeutic targets for ESCC, offering promising novel approaches for the diagnosis and treatment of ESCC. [ABSTRACT FROM AUTHOR]

Initiation of translation is the first of the three obligatory steps required for protein synthesis and is carried out by a large number of protein factors called initiation factors in conjunction with ribosomes. One of the key conserved protein factors in eukaryotes that plays a role in this process is eIF4A, which has three homologues in humans with eIF4A1 being the primary factor playing a role in translation initiation. eIF4As are members of the family of DEAD-box helicases that carry out different biological functions. eIF4A1s are recruited to translation initiation complexes via association with eIF4G and have ATP binding, ATP hydrolysis, RNA binding, and unwinding activities. Plasmodium and trypanosomatids such as Leishmania and Trypanosoma are parasites that cause human disease. While mechanistically the function of eIF4A1s in eukaryotes is well-understood, the orthologues peIF4A1s and keIF4A1s in Plasmodium and trypanosomatids are not well-studied. Here, we have used bioinformatics tools and homology modelling/structure prediction to study the motifs and functional signatures of Plasmodium and trypanosomatid peIF4A1s/keIF4A1s. We report a high degree of sequence conservation, structural conservation, and conservation of protein–protein interaction signatures of Plasmodium and trypanosomatid peIF4A1s/keIF4A1s in comparison with human eIF4A1. Thus, in spite of the great divergence in evolution between these parasites and higher eukaryotes, there is remarkable conservation of motifs and functional signatures in Plasmodium and trypanosomatid peIF4A1s/keIF4A1s. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is a primary liver tumor with high lethality and increasing incidence worldwide. While tumor resection or liver transplantation is effective in the early stages of the disease, the therapeutic options for advanced HCC remain limited and the benefits are temporary. Thus, novel therapeutic targets and more efficacious treatments against this deadly cancer are urgently needed. Here, we investigated the pathogenetic and therapeutic role of eukaryotic initiation factor 4A1 (eIF4A1) in this tumor type. We observed consistent eIF4A1 upregulation in HCC lesions compared with non-tumorous surrounding liver tissues. In addition, eIF4A1 levels were negatively correlated with the prognosis of HCC patients. In HCC lines, the exposure to various eIF4A inhibitors triggered a remarkable decline in proliferation and augmented apoptosis, paralleled by the inhibition of several oncogenic pathways. Significantly, anti-growth effects were achieved at nanomolar concentrations of the eIF4A1 inhibitors and were further increased by the simultaneous administration of the pan mTOR inhibitor, Rapalink-1. In conclusion, our results highlight the pathogenetic relevance of eIF4A1 in HCC and recommend further evaluation of the potential usefulness of pharmacological combinations based on eIF4A and mTOR inhibitors in treating this aggressive tumor. [ABSTRACT FROM AUTHOR]

Simple Summary: Lung cancer is a common cancer throughout the world. Despite advanced treatment strategies, the outcome is still poor. Based on the results of the present study, EIF4A1 interacting with EIF4H manipulates cell cycle regulation and immune microenvironment reprogramming in lung adenocarcinoma. The results specify EIF4A1 in lung adenocarcinoma tumorigenesis. Treatment derived from EIF4A1 would be worthy of further investigation. Lung adenocarcinoma (LUAD) is a common type of lung cancer. Although the diagnosis and treatment of LUAD have significantly improved in recent decades, the survival for advanced LUAD is still poor. It is necessary to identify more targets for developing potential agents against LUAD. This study explored the dysregulation of translation initiation factors, specifically eukaryotic initiation factors 4A1 (EIF4A1) and EIF4A2, in developing LUAD, as well as their underlying mechanisms. We found that the expression of EIF4A1, but not EIF4A2, was higher in tumor tissue and associated with poor clinical outcomes in LUAD patients. Elevated expression of EIF4H with poor prognosis may potentiate the oncogenic role of EIF4A1. Functional enrichment analysis revealed that upregulation of EIF4A1 was related to cell cycle regulation and DNA repair. The oncogenic effect of EIF4A1 was further elucidated by Gene Set Variation Analysis (GSVA). The GSVA score of the gene set positively correlated with EIF4A1 was higher in tumors and significantly associated with worse survival. In the meantime, gene set enrichment analysis (GSEA) also indicated that elevated EIF4A1 expression in LUAD patients was associated with a decreased infiltration score for immune cells by reducing anticancer immune cell types and recruiting immunosuppressive cells. Consistent with the results, the GSVA score of genes whose expression was negatively correlated with EIF4A1 was lower in the tumor tissue of LUAD cases with worse clinical outcomes and was strongly associated with the disequilibrium of anti-cancer immunity by recruiting anticancer immune cells. Based on the results from the present study, we hypothesize that the dysregulation of EIF4A1 might be involved in the pathophysiology of LUAD development by promoting cancer growth and changing the tumor immune microenvironment. This can be used to develop potential diagnostic biomarkers or therapeutic targets for LUAD. [ABSTRACT FROM AUTHOR]

Eukaryotic initiation factor (eIF) 4F plays a central role in the ribosome recruitment phase of cap-dependent translation. This heterotrimeric complex consists of a cap binding subunit (eIF4E), a DEAD-box RNA helicase (eIF4A), and a large bridging protein (eIF4G). In mammalian cells, there are two genes encoding eIF4A (eIF4A1 and eIF4A2) and eIF4G (eIF4G1 and eIF4G3) paralogs that can assemble into eIF4F complexes. To query the essential nature of the eIF4F subunits in normal development, we used CRISPR/Cas9 to generate mouse strains with targeted ablation of each gene encoding the different eIF4F subunits. We find that Eif4e, Eif4g1, and Eif4a1 are essential for viability in the mouse, whereas Eif4g3 and Eif4a2 are not. However, Eif4g3 and Eif4a2 do play essential roles in spermatogenesis. Crossing of these strains to the lymphoma-prone Eμ-Myc mouse model revealed that heterozygosity at the Eif4e or Eif4a1 loci significantly delayed tumor onset. Lastly, tumors derived from Eif4e∆38 fs/+/Eμ-Myc or Eif4a1∆5 fs/+/Eμ-Myc mice show increased sensitivity to the chemotherapeutic agent doxorubicin, in vivo. Our study reveals that eIF4A2 and eIF4G3 play non-essential roles in gene expression regulation during embryogenesis; whereas reductions in eIF4E or eIF4A1 levels are protective against tumor development in a murine Myc-driven lymphoma setting. [ABSTRACT FROM AUTHOR]

WD repeat domain 77 protein (WDR77) is required for cellular proliferation of lung and prostate epithelial cells during earlier stages of development and re-activated during prostate and lung tumorigenesis. WDR77 plays an essential role for prostate tumorigenesis and cell growth mediated by growth regulatory factors. Here, we identified E2F mRNAs as translational targets of WDR77. We demonstrated that WDR77 regulated the translation of E2F mRNAs through the five prime untranslated regions (5'UTRs) of E2F1/3 mRNAs. WDR77 physically interacted with programmed cell death 4 (PDCD4) that suppresses translation of mRNAs containing structured 5'UTRs by interacting with translation initiation factor eIF4A and inhibiting its helicase activity. Further, we demonstrated that the interaction between WDR77 and PDCD4 prevented the binding of PDCD4 to eIF4A and relieved PDCD4's inhibitory effect on eIF4A1. Overall, our work reveals for the first time that WDR77 is directly involved in translational regulation of E2F1/3 mRNAs through their 5'-structured UTRs, PDCD4, and eIF4A1 and provides novel insight into the cell growth controlled by WDR77. [ABSTRACT FROM AUTHOR]

Background: Currently, multiple circular RNAs (circRNAs) have been verified to act as essential regulators in the progression of gastric cancer (GC). We aimed to investigate the role of circ_0008035 in GC progression. Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to measure the expression of circ_0008035 and miR-599. 3-(4,5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay was employed to evaluate cell proliferation and ferroptosis. Western blot assay was performed to measure the levels of cyclin D1, proliferating cell nuclear antigen (PCNA) and eukaryotic initiation factor 4A1 (EIF4A1). Flow cytometry analysis was conducted to assess cell apoptosis. The iron accumulation, lipid peroxidation and mitochondrial membrane potential were examined by relevant kits. Dual-luciferase reporter assay was conducted to determine the targeting relationship between miR-599 and circ_0008035 or EIF4A1. A murine xenograft model was established to investigate the function of circ_0008035 in vivo. Results: Circ_0008035 was up-regulated in GC tissues and cells. Silencing of circ_0008035 repressed cell proliferation and induced cell apoptosis and ferroptosis in GC cells. Circ_0008035 acted as a sponge of miR-599. The effects of circ_0008035 knockdown on GC cell proliferation, apoptosis and ferroptosis were abolished by miR-599 inhibition. EIF4A1 was confirmed to be a target gene of miR-599. Circ_0008035 knockdown inhibited EIF4A1 expression by targeting miR-599. Moreover, the suppressive role of circ_0008035 deficiency in GC progression could be restored by EIF4A1. Additionally, circ-0008035 knockdown hampered tumorigenesis in vivo. Conclusion: Circ_0008035 promoted GC cell growth and repressed apoptosis and ferroptosis by up-regulating EIF4A1 through sponging miR-599. [ABSTRACT FROM AUTHOR]

Key message: Co-expression of Na+/H+ antiporter NHX1 and DEAD-box RNA helicase eIF4A1 from Arabidopsis positively regulates drought stress tolerance by improving ROS scavenging capacity and maintaining membrane integrity in sweetpotato. Plants evolve multiple strategies for stress adaptation in nature. To improve sweetpotato resistance to drought stress, transgenic sweetpotato plants overexpressing the Arabidopsis Na+/H+ antiporter, NHX1, and the translation initiation factor elF4A1 were characterized for phenotypic traits and physiological performance. Without drought treatment, the NHX1–elF4A1 stacked lines (NE lines) showed normal, vigorous growth comparable to the WT plants. The NE plants showed dense green foliage with delayed leaf senescence and developed more roots than WT plants under drought treatment for 18 days. Compared to WT plants, higher level of reactive oxygen scavenging capacity was detected in NE lines as indicated by reduced H2O2 accumulation as well as increased superoxide dismutase activity and proline content. The relative ion leakage and malondialdehyde content were reduced in NE plants, indicating improved maintenance of intact membranes system. Both NE plants and NHX1-overexpressing plants (N lines) showed larger aerial parts and well-developed root system compared to WT plants under the drought stress conditions, likely due to the improved antioxidant capacity. The NE plants showed better ROS scavenging than N-line plants. All N- and NE-line plants produced normal storage roots with similar yields as WT in the field under normal growth conditions. These results demonstrated the potential to enhance sweetpotato productivity through stacking genes that are involved in ion compartmentalization and translation initiation. [ABSTRACT FROM AUTHOR]

Background: MicroRNAs (miRNAs) play a key role in the development of gastric cancer (GC). MiRNA arrays showed that lymph node metastasis in GC is correlated with the expression of miR-1284. Although its function and mechanisms in GC have not been fully described, the regulation of EIF4A1 by miR-1284 and its role in drug-resistant GC has been reported in our previous studies. Methods: qRT-PCR was used to study the level of miR-1284 expression in GC cell lines and tissues. Subsequently, the CCK-8 assay was used to detect cell proliferation, while transwell assay was used to detect invasion and migration of the GC cells. Flow cytometry was used to detect the effect of miR-1284 on GC cells in vivo by building subcutaneous GC nude mice transplantation tumor model. In addition, the influence of miR-1284 gene expression profile in SGC-7901 cells was detected by total gene expression chip, and the target gene of miR-1284 was detected by luciferase reporter assay, qRT-PCR, and western blotting. Results: The miR-1284 level was down-regulated in GC tssues and cell lines. MiR-1284 was significantly associated with tumor size, degree of differentiation and patients' distant metastasis. MiR-1284 inhibited invasion, migration, and proliferation of GC cells. During the G1/S phase, miR-1284 arrested the cycle of GC cells in vitro. MiR-1284 also suppressed tumor from growing and metastasizing in xenograft models as well as influenced the gene expression profile in SGC-7901 cells. Also, EIF4A1 was the direct target gene for miR-1284. Further, an inverse correlation between the miR-1284 expression and EIF4A1 was found in GC tissues. Over-expressed miR-1284 decreased c-Myc, MMP12, JUN expression, while increased CDH1 expression. Conclusion: These data suggested that miR-1284 acts as a tumor suppressor, and directly blocked EIF4A1 in GC. [ABSTRACT FROM AUTHOR]

The previously developed technology RNA enhancement (RNAe) is reported to increase specific gene expression at post-transcriptional level via a long noncoding RNA (lncRNA). The mechanism for SINEB2-dependent enhancement of translation remains not well understood. Here we present the result of experiments with the folded states of lncRNA in doubly deionized water obtained by slowcool method. These lncRNA were used in RNA pull-down assay that yielded six lncRNA-binding proteins potentially involved in RNAe. The direct interactions of lncRNA with interleukin enhancer-binding factor 3 (ILF3) and eukaryotic initiation factor 4A-I (eIF4A1) in vivo and in vitro were confirmed in RNA-binding protein affinity experiment and electrophoretic mobility shift assay (EMSA), respectively. These observations could explain RNAe phenomenon through lncRNA-dependent guiding of ILF3 protein, which, in turn, recruits polysomes or the factors for translation initiation, and attracting eIF4A1 proteins accelerating the unwinding of the secondary structure at the 5'-end of mRNA during translation initiation. Therefore, the hypothetical mechanism through which lncRNAs may regulate the translation of a specific mRNA is proposed. [ABSTRACT FROM AUTHOR]

Clear cell renal cell carcinoma (ccRCC) is a worldwide malignancy with high morbidity and mortality. Translation initiation factor 4A1 (eIF4A1), which is an ATP-dependent RNA helicase as a part of eIF4F complex, has been linked to malignant transformation and progression, and a variety of cancers display dysregulation of this enzyme. However, its role in ccRCC remains unclear. In our study, we examined its potential effects in ccRCC. Based on Proteomic data, TCGA and ONCOMINE database, RCC cell lines and tissues, the expression of eIF4A1 between ccRCC and normal tissues were investigated. A correlation was evaluated between the prognostic model for OS and ccRCC progression. Analysis of functional enrichment and PPI network were performed. After examining differentially expressed genes between the eIF4A1 high and low-expression groups, we performed GSEA analysis. Furthermore, we investigated immune cell infiltration of eIF4A1. Then we determined eIF4A1 functions in the establishment and maintenance of cell viability, migration and invasion of cell lines. Flow cytometry was utilized to detect cell cycle. The eIF4A1 was up-regulated in ccRCC tissues and cell lines. An increased level of eIF4A1 was linked to lower survival rates and impaired immunity. Depletion of eIF4A1 could arrest tumor cells in G1 phase, so as to seriously limit cell proliferation and weaken the capacity of cell migration. ccRCC patients with high eIF4A1 expression are at increased risk of poor prognosis, furthermore eIF4A1 plays a prominent role in facilitating tumor cell proliferation and migration which may further be a potential prognostic biomarker and therapeutic target. • High-expression of eIF4A1 in ccRCC. • Interference of eIF4A1 inhibited the cell viability, migration and invasion. • Knockdown of eIF4A1 induced cell cycle arrest. [ABSTRACT FROM AUTHOR]

Highlights: [•] eIF4A1 is the direct target gene of miR-US25-2-3p. [•] Over-expression of miR-US25-2-3p inhibits HCMV replication by targeting eIF4A1. [•] Over-expression of miR-US25-2-3p decreases eIF4A1-mediated translation. [•] miR-US25-2-3p significantly inhibits host cell proliferation and genomic DNA synthesis. [ABSTRACT FROM AUTHOR]

eIF4A is a DEAD box containing RNA helicase that plays crucial roles in regulating translation initiation, growth and abiotic stress tolerance in plants. It also functions as an ATP-dependent RNA binding protein to curb granule formation by limiting RNA-RNA interactions that promote RNA condensation and formation of ribonucleoprotein particles in vivo. Helicase activity of eIF4A is known to be dictated by its binding partners. Proteins interacting with eIF4A have been identified across land plants. In monocots a close link between eIF4A regulated processes and DNA methylation in epigenetic regulation of plant development is inferred from interaction between OseIF4A and the de novo methyltransferase OsDRM2 and loss-of-function studies of these genes in Oryza sativa and Brachypodium distachyon. In the moss Physcomitrella patens , eIF4A1 encoded by Pp3c6_1080V3.1 interacts with the heterogeneous nuclear ribonucleoprotein (hnRNP) PpLIF2L1, homolog of which in Arabidopsis regulates transcription of stress-responsive genes. In this study, using different protein-protein interaction methods, targeted gene knockout strategy and quantitative expression analysis we show genetic interaction between PpeIF4A1 and the putative nucleosome remodeler protein PpDDM1 and between PpDDM1 and PpLIF2L1 in vivo. Stress-induced co-expression of PpeIF4A1 , PpDDM1 and PpLIF2L1 , their roles in salt stress tolerance and differences in subnuclear distribution of PpLIF2L1 in ppeif4a1 cells in comparison to wild type suggest existence of a regulatory network comprising of RNA helicases, chromatin remodelling proteins and hnRNP active in stress-responsive biological processes in P. patens. • In moss RNA helicase eIF4A1 and DDM1 interact and are essential for stress recovery. • Genetic interaction between PpeIF4A1 and hnRNP LIF2L1 may regulate speckle formation. • PpeIF4A1, PpDDM1 and PpLIF2L1 regulated activities may be linked in stress response. [ABSTRACT FROM AUTHOR]

The eukaryotic translation initiation factor 4F complex (eIF4F) is a potential chemotherapeutic target in triple-negative breast cancer (TNBC). This complex regulates cap-dependent translational initiation and consists of three core proteins: eIF4E, eIF4G, and eIF4A1. In this study, we focus on repositioning compounds as novel inhibitors of eIF4A1-mediated translation. In order to accomplish this goal, a modified synthetic reporter assay was established. More specifically, a (CGG)4 motif, which confers eIF4A dependency, was incorporated into the 5'-leader region of a luciferase-tdTomato lentiviral reporter construct. The Prestwick Chemical Library was then screened in multiple TNBC cell lines by measuring the tdTomato fluorescent intensity. We identified several cardiac glycosides as potential inhibitors of eIF4A1-mediated translation. Based on our studies, we find that cardiac glycosides inhibit the expression of eIF4A1. To identify a potential mechanism by which this was occurring, we utilized the Integrative Library of Integrated Network-Based Cellular Signatures (iLINCS). Our pursuits led us to the discovery that cardiac glycosides also decrease levels of c-MYC. Quantitative PCR confirmed that decreases in c-MYC and eIF4A were occurring at the transcriptional level. As such, disruption of the eIF4A1-c-MYC axis may be a viable approach in the treatment of TNBC. The novel combination of rocaglamide A and digoxin exhibited synergistic anti-cancer activity against TNBC cells in vitro. The findings in this study and others are important for formulating potential combination chemotherapies against eIF4A1 in vivo. Thus, drug repositioning may be one classical approach to successfully target eIF4A1 in TNBC patients. [ABSTRACT FROM AUTHOR]

DExD (DDX)- and DExH (DHX)-box RNA helicases, named after their Asp-Glu-x-Asp/His motifs, are integral to almost all RNA metabolic processes in eukaryotic cells. They play myriad roles in processes ranging from transcription and mRNA-protein complex remodeling, to RNA decay and translation. This last facet, translation, is an intricate process that involves DDX/DHX helicases and presents a regulatory node that is highly targetable. Studies aimed at better understanding this family of conserved proteins have revealed insights into their structures, catalytic mechanisms, and biological roles. They have also led to the development of chemical modulators that seek to exploit their essential roles in diseases. Herein, we review the most recent insights on several general and target-specific DDX/DHX helicases in eukaryotic translation initiation. [ABSTRACT FROM AUTHOR]

Background: Pancreatic cancer is one of the most malignant cancers. The overall 5-year survival rate of its patients is 8%, the lowest among major cancer types. It is very urgent to study the development mechanisms of this cancer and provide potential targets for therapeutics design. Glucose, one of the most essential nutrients, is highly exploited for aerobic glycolysis in tumor cells to provide building blocks. However, the glucose consumption manner in pancreatic cancer cells is unclear. And the mechanism of the substantial metabolic pathway promoting pancreatic cancer development is also unrevealed. Methods: 13C6 glucose was used to trace the glucose carbon flux and detected by mass spectrum. The expressions of PHGDH were determined in cells and pancreatic adenocarcinomas. Knockdown and overexpression were performed to investigate the roles of PHGDH on pancreatic cancer cell proliferation, colony formation and tumor growth. The mechanisms of PHGDH promoting pancreatic cancer development were studied by identifying the interacting proteins and detecting the regulatory functions on translation initiations. Results: Pancreatic cancer cells PANC-1 consumed large amounts of glucose in the serine and glycine de novo synthesis. Phosphoglycerate dehydrogenase (PHGDH) highly expressed and controlled this pathway. Knockdown of PHGDH significantly attenuated the tumor growth and prolonged the survival of tumor bearing mice. The pancreatic adenocarcinoma patients with low PHGDH expression had better overall survival. Mechanistically, knockdown of PHGDH inhibited cell proliferation and tumorigenesis through disrupting the cell-cell tight junctions and the related proteins expression. Besides catalyzing serine synthesis to activate AKT pathway, PHGDH was found to interact with the translation initiation factors eIF4A1 and eIF4E and facilitated the assembly of the complex eIF4F on 5' mRNA structure to promote the relevant proteins expression. Conclusion: Besides catalyzing serine synthesis, PHGDH promotes pancreatic cancer development through enhancing the translation initiations by interacting with eIF4A1 and eIF4E. Inhibiting the interactions of PHGDH/eIF4A1 and PHGDH/eIF4E will provide potential targets for anti-tumor therapeutics development. [ABSTRACT FROM AUTHOR]