Radiation-sensitive circRNA hsa_circ_0096498 inhibits radiation-induced liver fibrosis by suppressing EIF4A3 nuclear translocation to decrease CDC42 expression in hepatic stellate cells.

BACKGROUND: Radiation-induced liver fibrosis (RILF) is a common manifestation of radiation-induced liver injury (RILI) and is caused primarily by activated hepatic stellate cells (HSCs). Circular RNAs (circRNAs) play critical roles in various diseases, but little is known about the function and mechanism of circRNAs in RILF. METHODS: RNA pull-down and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to screen binding proteins of hsa_circ_0096498 (circ96498). RNA-binding protein immunoprecipitation, RNA pull-down and nuclear and cytoplasmic protein extraction were conducted to confirm the interaction between circ96498 and eukaryotic initiation factor 4A3 (EIF4A3). RNA sequencing was performed to screen target genes regulated by EIF4A3. HSCs with altered circ96498 and cell division cycle 42 (CDC42) expression were used to assess irradiated HSC activation. Circ96498 inhibition and CDC42 blockade were evaluated in RILF mouse models. RESULTS: In this study, we identified a radiation-sensitive circ96498, which was highly expressed in the irradiated HSCs of paracancerous tissues from RILI patients. Circ96498 inhibited the proliferation but promoted the apoptosis of irradiated HSCs, suppressed the secretion of proinflammatory cytokines IL-1ß, IL-6 and TNF-α, and decreased the expression of profibrotic markers (α-SMA and collagen 1) in irradiated HSCs. Mechanistically, irradiation induced the transport of EIF4A3 into the nucleus, and nuclear EIF4A3 increased the stability of CDC42 mRNA and increased CDC42 expression, thereby promoting HSC activation through the NF-κB and JNK/Smad2 pathways. However, the binding of circ96498 to EIF4A3 impeded the translocation of EIF4A3 into the nucleus, resulting in the inhibition of CDC42 expression and subsequent HSC activation. Furthermore, circ96498 knockdown promoted the development of the early and late stages of RILF in a mouse model, which was mitigated by CDC42 blockade. CONCLUSIONS: Collectively, our findings elucidate the involvement of the circ96498/EIF4A3/CDC42 axis in inhibiting irradiated HSC activation, which offers a novel approach for RILF prevention and treatment.

EIF4A3 is stabilized by the long noncoding RNA BC200 to regulate gene expression during Epstein-Barr virus infection.

Epstein‒Barr virus (EBV) regulates the expression of host genes involved in functional pathways for viral infection and pathogenicity. Long noncoding RNAs (lncRNAs) have been found to be important regulators of cellular biology. However, how EBV affects host biological processes via lncRNAs remains elusive. Eukaryotic initiation factor 4A3 (EIF4A3) was recently identified as an essential controller of cell fate with an unknown role in EBV infection. Here, the expression of lncRNA brain cytoplasmic 200 (BC200) was shown to be significantly upregulated in EBV-infected cell lines. RNA immunoprecipitation and RNA pulldown assays confirmed that BC200 bound to EIF4A3. Moreover, BC200 promoted EIF4A3 expression at the protein level but not at the mRNA level. Mechanistically, BC200 stabilized the EIF4A3 protein by impeding the K48-linked polyubiquitination of the K195 and K198 residues of EIF4A3. In addition, RNA-seq analysis of EBV-positive cells with knockdown of either BC200 or EIF4A3 revealed that a broad range of cellular genes were differentially regulated, particularly those related to virus infection and immune response pathways. This study is the first to reveal the key residues involved in EIF4A3 polyubiquitination and elucidate the novel regulatory role of EBV in host gene expression via the BC200/EIF4A3 axis. These results have implications for the pathogenesis and treatment of EBV-related diseases.

Circ_0005397 inhibits ferroptosis of pancreatic cancer cells by up-regulating PCBP2 through KAT6A/H3K9Ac.

Pancreatic cancer is a highly aggressive and lethal carcinoma. Circular RNAs (circRNAs) serve key regulatory functions in pancreatic cancer. Ferroptosis was induced by erastin treatment and analyzed by examining malondialdehyde (MDA), iron, Fe2+ and glutathione (GSH). C11-BODIPY 581/591 was used to stain cells for analyzing lipid peroxidation. RNA immunoprecipitation, pull-down and chromatin immunoprecipitation assays were applied to evaluate intermolecular interaction. Mice received subcutaneous injection of pancreatic cancer cells as a model of subcutaneous tumor for in vivo tests. Circ_0005397 was abundantly expressed in pancreatic cancer, and its upregulation was associated with low survival of patients with pancreatic cancer. Circ_0005397 expression was induced by EIF4A3. PCBP2 was highly expressed in pancreatic cancer, and circ_0005397 and PCBP2 were positively correlated in patients with pancreatic cancer. Circ_0005397 knockdown sensitized pancreatic carcinoma cells to ferroptosis via downregulating PCBP2. Circ_0005397 promoted PCBP2 transcription via facilitating the binding of KAT6A and H3K9ac to PCBP2 promoter. Silencing of circ_0005397 reduced tumor growth by enhancing erastin-induced ferroptosis in vivo. EIF4A3-induced circ_0005397 inhibited erastin-induced ferroptosis in pancreatic cancer by promoting PCBP2 expression through KAT6A and H3K9ac.

RBM8A, a new target of TEAD4, promotes breast cancer progression by regulating IGF1R and IRS-2.

BACKGROUND: Breast cancer (BC) is the most common malignant tumor in women worldwide, and further elucidation of the molecular mechanisms involved in BC pathogenesis is essential to improve the prognosis of BC patients. RNA Binding Motif Protein 8 A (RBM8A), with high affinity to a myriad of RNA transcripts, has been shown to play a crucial role in genesis and progression of multiple cancers. We attempted to explore its functional significance and molecular mechanisms in BC. METHODS: Bioinformatics analysis was performed on publicly available BC datasets. qRT-PCR was used to determine the expression of RBM8A in BC tissues. MTT assay, clone formation assay and flow cytometry were employed to examine BC cell proliferation and apoptosis in vitro. RNA immunoprecipitation (RIP) and RIP-seq were used to investigate the binding of RBM8A/EIF4A3 to the mRNA of IGF1R/IRS-2. RBM8A and EIF4A3 interactions were determined by co-immunoprecipitation (Co-IP) and immunofluorescence. Chromatin immunoprecipitation (Ch-IP) and dual-luciferase reporter assay were carried out to investigate the transcriptional regulation of RBM8A by TEAD4. Xenograft model was used to explore the effects of RBM8A and TEAD4 on BC cell growth in vivo. RESULTS: In this study, we showed that RBM8A is abnormally highly expressed in BC and knockdown of RBM8A inhibits BC cell proliferation and induces apoptosis in vitro. EIF4A3, which phenocopy RBM8A in BC, forms a complex with RBM8A in BC. Moreover, EIF4A3 and RBM8A complex regulate the expression of IGF1R and IRS-2 to activate the PI3K/AKT signaling pathway, thereby promoting BC progression. In addition, we identified TEAD4 as a transcriptional activator of RBM8A by Ch-IP, dual luciferase reporter gene and a series of functional rescue assays. Furthermore, we demonstrated the in vivo pro-carcinogenic effects of TEAD4 and RBM8A by xenograft tumor experiments in nude mice. CONCLUSION: Collectively, these findings suggest that TEAD4 novel transcriptional target RBM8A interacts with EIF4A3 to increase IGF1R and IRS-2 expression and activate PI3K/AKT signaling pathway, thereby further promoting the malignant phenotype of BC cells.

LncRNA SSTR5-AS1 promotes esophageal carcinoma through regulating ITGB6/JAK1/STAT3 signaling.

Aim: To investigate function of somatostatin receptor 5 antisense RNA 1 (SSTR5-AS1) in esophageal carcinoma (ESCA).Materials & methods: The cellular function was assessed using EdU staining and Transwell assay. The localization of SSTR5-AS1 was measured using fluorescence in situ hybridization staining.Results: SSTR5-AS1 shRNA repressed invasion and migration and induced apoptosis in ESCA cells. SSTR5-AS1 was distributed in cytoplasm, and it regulated its subunit integrin beta 6 (ITGB6) via eukaryotic translation initiation factor 4A3 (EIF4A3). SSTR5-AS1 shRNA inactivated ITGB6 and JAK1/STAT3 signaling. SSTR5-AS1 silencing attenuated the malignant behavior of ESCA cells through the ITGB6-mediated JAK1/STAT3 axis.Conclusion: SSTR5-AS1 promotes tumorigenesis of ESCA by interacting with EIF4A3 to regulate ITGB6/JAK1/STAT3 axis, which serves a basis for discovering strategies against ESCA.

The development of esophageal carcinoma (ESCA) seriously affects the health of people. Although great efforts have been made for curing ESCA, the outcomes remain limited. In this research, we used large amounts of experiments about the molecular biology. As expected, we found knockdown of lncRNA SSTR5-AS1 could inhibit the tumorigenesis of ESCA through mediation of its subunit integrin beta 6 /JAK1/STAT3 axis. Thus, our research provided new molecular targets for ESCA treatment.

The oncogenic role of EIF4A3/CDC20 axis in the endometrial cancer.

Eukaryotic initiation factor 4A-3 (EIF4A3) is a key component of the exon junction complex (EJC) and is extensively involved in RNA splicing, inducing mRNA decay, and regulating the cell cycle and apoptosis. However, the potential role of EIF4A3 in EC has not been comprehensively investigated and remains unknown. Here, we report that the expression level of EIF4A3 is dramatically elevated in endometrial cancer (EC) samples compared with normal EC samples via bioinformatics analysis and immunohistochemistry analysis, and that high expression of EIF4A3 promotes the proliferation, migration, and invasion of EC cells. Mechanistically, we found that high EIF4A3 expression stabilized cell division cyclin 20 (CDC20) mRNA, and high EIF4A3 expression induced pro-carcinogenic effects in EC cells that were efficiently antagonized upon knockdown of CDC20, as well as Apcin, an inhibitor of CDC20. These findings reveal a novel mechanism by which high expression of EIF4A3 induces CDC20 upregulation, thus leading to EC tumorigenesis and metastasis, indicating a potential treatment strategy for EC patients with high EIF4A3 expression using Apcin. KEY MESSAGES: The expression level of EIF4A3 was dramatically elevated in endometrial cancer (EC) samples compared with normal endometrial cancer samples. High EIF4A3 expression stabilized CDC20 mRNA, and high EIF4A3 expression induced pro-carcinogenic effect in EC cells which was efficiently antagonized upon knockdown of CDC20. Apcin, an inhibitor of CDC20, could effectively counteract high expression of EIF4A3 inducing EC tumourigenesis and metastasis, indicating the potential treatment strategy for EC patients with EIF4A3 high expression by using Apcin.

Functional elucidation of the EIF4A3-circR-4225-miR-507-TNFSF11 regulatory axis in LUAD and its role in tumor progression.

Lung adenocarcinoma (LUAD) is the most common subtypes of NSCLC. However, the therapeutic effects for LUAD are unsatisfactory at current stage, so it is important to find new molecular targets and therapeutic strategies. circRNAs can regulate the expression of target genes by binding to microRNAs (miRNAs) to form competitive endogenous RNAs (ceRNAs). Therefore, we investigated the functions of circR-4225 in the tumor progression of LUAD and its molecular mechanism in this paper. circR-4225 is up-regulated in LUAD tissues. EIF4A3, a member of the eukaryotic translation initiation factor 4A (EIF4A) family, promotes the expression of circR-4225. circR-4225 acts as a molecular sponge to down-regulate miR-507, which promotes the up-regulation of the expression of its target gene-tumor necrosis factor superfamily member 11 (TNFSF11). Knockdown of circR-4225 in the LUAD cell lines can inhibit cell proliferation and viability, and promote apoptosis of the LUAD cell lines, which can be reverted by inhibiting miR-507 or overexpressing TNFSF11. To sum it up, this study demonstrated that circR-4225 was significantly up-regulated in LUAD tissues, and circR-4225 promoted LUAD progression by sponging miR-507 and up-regulating TNFSF11. This study can provide new molecular targets for early diagnosis and treatment of LUAD.

EIF4A3-Induced Upregulation of hsa_circ_0049396 Attenuates the Tumorigenesis of Nasopharyngeal Carcinoma by Regulating the Hippo-YAP Pathway.

Circular RNAs (circRNAs) and eukaryotic translation initiation factor 4A3 (EIF4A3) have been reported to participate in the pathogenesis of nasopharyngeal carcinoma (NPC), but their mechanism has not been fully understood. This research aimed to confirm the role and regulatory mechanism of hsa_circ_0049396 interacting with EIF4A3 in NPC tumorigenesis. Quantitative real time polymerase chain reaction (qRT-PCR) was executed to detect the levels of hsa_circ_0049396 and EIF4A3. Cell function experiments and nude mice xenograft assay were used to confirm the role of hsa_circ_0049396 in NPC. The regulatory effect of EIA4A3 on hsa_circ_0049396 was determined by circInteractome prediction, RNA binding protein immunoprecipitation (RIP) assay, and qRT-PCR. In addition, the Hippo-YAP pathway-related proteins and EIF4A3 protein were detected by western blotting. hsa_circ_0049396 was proved to be downregulated in NPC samples, and its low expression indicated the poor prognosis of NPC. After upregulating hsa_circ_0049396 in NPC cells, the proliferation, migration, invasion, and tumor growth in vivo were suppressed by inhibiting the Hippo-YAP pathway. Moreover, EIF4A3 bound to the flanking regions of the hsa_circ_0049396 to enhance hsa_circ_0049396 expression in NPC cells. hsa_circ_0049396 mediated by EIF4A3 in NPC can attenuate NPC tumorigenesis by inhibiting the Hippo-YAP pathway. This finding may provide a potential early diagnostic biomarker or drug target to improve the precision medicine approaches of NPC.

EIF4A3-induced hsa_circ_0078136 inhibits the tumorigenesis of retinoblastoma via IL-17 signaling pathway.

PURPOSE: Retinoblastoma (RB) is one of the most common intraocular cancers, with the highest prevalence among infants and young children under the age five. Numerous findings across the literature illustrate the involvement and significance of circular RNAs (circRNAs) in human malignancies, including RB. The current investigation attempted to decipher the exact roles and underlying mechanisms of a novel circRNA, hsa_circ_0078136, in RB progression. METHODS: The hsa_circ_0078136 expression was evaluated in RB tumors and cell lines via qRT-PCR. The significance of hsa_circ_0078136 in RB was examined by performing CCK8 assay, transwell assays, western blotting of apoptotic and IL-17 signaling ligand molecules, and a subcutaneous xenograft tumor model. In addition, the interaction of circRNA and eukaryotic translation initiation factor 4A3 (EIF4A3) was determined with bioinformatics, western blot, and RIP assay. RESULTS: The hsa_circ_0078136 expression was reduced in RB tumor samples and cells. Additionally, its overexpression restricted the oncogenic properties of RB cells in vitro. Moreover, hsa_circ_0078136 overexpression lowered the protein levels of cytokine ligand molecules of IL-17 signaling pathway in RB cell lines. In vivo, hsa_circ_0078136 overexpression in subcutaneous tumor xenografts reduced tumor growth. We also observed that EIF4A3 binds to the downstream flanking sequence of hsa_circ_0078136 in the SHRPH pre-mRNA transcript, and EIF4A3 overexpression reduced hsa_circ_0078136 expression, suggesting that EIF4A3 inhibited hsa_circ_0078136 formation. CONCLUSIONS: Our results demonstrate that hsa_circ_0078136 is regulated by EIF4A3 and functions as a tumor suppressor via the IL-17 signaling pathway in RB.

CircAKR1B10 interacts with EIF4A3 to stabilize AURKA and promotes IL-22-induced proliferation, migration and invasion in keratinocytes.

Circular RNAs (circRNAs) are demonstrated to be involved in psoriasis progression. CircRNAs can act as RNA-binding protein (RBP) sponges. Here, we investigated the action of circAKR1B10 in psoriasis, and explored the potential proteins interacted with circAKR1B10. Levels of genes and proteins were assayed by qRT-PCR and western blotting analyses. Keratinocytes in functional groups were treated with interleukin (IL)-22. Functional analysis were conducted using MTT, 5-ethynyl-2'-deoxyuridine (EdU), and transwell assays, respectively. Interaction analysis among circAKR1B10, Eukaryotic initiation factor 4 A-III (EIF4A3) and Aurora Kinase A (AURKA) was conducted using bioinformatics analysis, RNA pull-down assay, and RNA immunoprecipitation (RIP) assay. CircAKR1B10 was highly expressed in psoriasis patients and IL-22-induced keratinocytes. Functionally, knockdown of circAKR1B10 abolished IL-22-induced proliferation, migration and invasion in keratinocytes. AURKA expression was also higher in psoriasis patients and IL-22-induced keratinocytes, and was negatively correlated with circAKR1B10 expression. Moreover, AURKA silencing reduced the proliferative, migratory and invasive abilities of IL-22-induced keratinocytes. Mechanistically, circAKR1B10 interacted with EIF4A3 protein to stabilize and regulate AURKA expression. CircAKR1B10 contributes to IL-22-induced proliferation, migration and invasion in keratinocytes via up-regulating AURKA expression through interacting with EIF4A3 protein.

The RNA-binding protein EIF4A3 promotes axon development by direct control of the cytoskeleton.

The exon junction complex (EJC), nucleated by EIF4A3, is indispensable for mRNA fate and function throughout eukaryotes. We discover that EIF4A3 directly controls microtubules, independent of RNA, which is critical for neural wiring. While neuronal survival in the developing mouse cerebral cortex depends upon an intact EJC, axonal tract development requires only Eif4a3. Using human cortical organoids, we show that EIF4A3 disease mutations also impair neuronal growth, highlighting conserved functions relevant for neurodevelopmental pathology. Live imaging of growing neurons shows that EIF4A3 is essential for microtubule dynamics. Employing biochemistry and competition experiments, we demonstrate that EIF4A3 directly binds to microtubules, mutually exclusive of the EJC. Finally, in vitro reconstitution assays and rescue experiments demonstrate that EIF4A3 is sufficient to promote microtubule polymerization and that EIF4A3-microtubule association is a major contributor to axon growth. This reveals a fundamental mechanism by which neurons re-utilize core gene expression machinery to directly control the cytoskeleton.

EIF4A3-Induced Circ_0059914 Promoted Angiogenesis and EMT of Glioma via the miR-1249/VEGFA Pathway.

Gliomas are common brain tumors. Despite extensive research, the 5-year survival rate of glioma remains low. Many studies have reported that circular RNAs (circRNAs) play a role in promoting the malignant progression of glioma; however, the role of circ_0059914 in this process remains unclear. In this study, we aimed to investigate the function and underlying mechanism of circ_0059914 in glioma. Western blotting and qRT-PCR were used to determine the levels of circ_0059914, miR-1249, VEGFA, N-cadherin, vimentin, Snail, and EIF4A3. EDU and colony formation assays were conducted to evaluate cell proliferation. Transwell assays were used to explore cell migration and invasion and tube formation assays were used to analyze angiogenesis. RNA immunoprecipitation (RIP) and dual-luciferase reporter assays were used to explore the relationship between EIF4A3, circ_0059914, miR-1249, and VEGFA. A xenograft tumor assay was performed to determine the role of circ_0059914 in vivo. Circ_0059914 expression was upregulated in gliomas. Knockdown of gliomal circ_0059914 expression reduced the proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), angiogenesis, and growth of glioma cells in vivo. Circ_0059914 sponged miR-1249, and miR-1249 inhibition reversed the circ_0059914 knockdown-mediated effects in glioma cells. VEGFA was found to be a target gene of miR1249; overexpression of VEGFA reversed the effect of miR-1249 up-regulation in glioma. Finally, EIF4A3 increased the expression of circ_0059914. EIF4A3-induced circ_0059914 expression plays a role in promoting glioma via the miR-1249/VEGFA axis.

EIF4A3-Induced CircDHTKD1 regulates glycolysis in non-small cell lung cancer via stabilizing PFKL.

Lung cancer (LC) is one of the malignancies with the highest incidence and mortality in the world, approximately 85% of which is non-small cell lung cancer (NSCLC). Circular RNAs (circRNAs) exert multiple roles in NSCLC occurrence and development. The sequencing results in previous literature have illustrated that multiple circRNAs exhibit upregulation in NSCLC. We attempted to figure out which circRNA exerts an oncogenic role in NSLCL progression. RT-qPCR evaluated circDHTKD1 level in NSCLC tissue specimens and cells. Reverse transcription as well as RNase R digestion assay evaluated circDHTKD1 circular characterization in NSCLC cells. FISH determined circDHTKD1 subcellular distribution in NSCLC cells. Loss- and gain-of-function assays clarified circDHTKD1 role in NSCLC cell growth, tumour growth and glycolysis. Bioinformatics and RIP and RNA pull-down assessed association of circDHTKD1 with upstream molecule Eukaryotic initiation factor 4A-III (EIF4A3) or downstream molecule phosphofructokinase-1 liver type (PFKL) and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) in NSCLC cells. Rescue assays assessed regulatory function of PFKL in circDHTKD1-meidated NSCLC cellular phenotypes. CircDHTKD1 exhibited upregulation and stable circular nature in NSCLC cells. EIF4A3 upregulated circDHTKD1 in NSCLC cells. CircDHTKD1 exerted a promoting influence on NSCLC cell malignant phenotypes and tumour growth. CircDHTKD1 exerted a promoting influence on NSCLC glucose metabolism. CircDHTKD1 exerts a promoting influence on NSCLC glucose metabolism through PFKL upregulation. RIP and RNA pull-down showed that circDHTKD1 could bind to IGF2BP, PFKL could bind to IGF2BP2, and circDHTKD1 promoted the binding of PFKL to IGF2BP2. In addition, RT-qPCR showed that IGF2BP2 knockdown promoted PFKL mRNA degradation, suggesting that IGF2BP2 stabilized PFKL in NSCLC cells. CircDHTKD1 exhibits upregulation in NSCLC. We innovatively validate that EIF4A3-triggered circDHTKD1 upregulation facilitates NSCLC glycolysis through recruiting m6A reader IGF2BP2 to stabilize PFKL, which may provide a new direction for seeking targeted therapy plans of NSCLC.

Circular RNA hsa_circ_0000467 promotes colorectal cancer progression by promoting eIF4A3-mediated c-Myc translation.

BACKGROUND: Colorectal cancer (CRC) is the second most common malignant tumor worldwide, and its incidence rate increases annually. Early diagnosis and treatment are crucial for improving the prognosis of patients with colorectal cancer. Circular RNAs are noncoding RNAs with a closed-loop structure that play a significant role in tumor development. However, the role of circular RNAs in CRC is poorly understood. METHODS: The circular RNA hsa_circ_0000467 was screened in CRC circRNA microarrays using a bioinformatics analysis, and the expression of hsa_circ_0000467 in CRC tissues was determined by in situ hybridization. The associations between the expression level of hsa_circ_0000467 and the clinical characteristics of CRC patients were evaluated. Then, the role of hsa_circ_0000467 in CRC growth and metastasis was assessed by CCK8 assay, EdU assay, plate colony formation assay, wound healing assay, and Transwell assay in vitro and in a mouse model of CRC in vivo. Proteomic analysis and western blotting were performed to investigate the effect of hsa_circ_0000467 on c-Myc signaling. Polysome profiling, RT‒qPCR and dual-luciferase reporter assays were performed to determine the effect of hsa_circ_0000467 on c-Myc translation. RNA pull-down, RNA immunoprecipitation (RIP) and immunofluorescence staining were performed to assess the effect of hsa_circ_0000467 on eIF4A3 distribution. RESULTS: In this study, we found that the circular RNA hsa_circ_0000467 is highly expressed in colorectal cancer and is significantly correlated with poor prognosis in CRC patients. In vitro and in vivo experiments revealed that hsa_circ_0000467 promotes the growth and metastasis of colorectal cancer cells. Mechanistically, hsa_circ_0000467 binds eIF4A3 to suppress its nuclear translocation. In addition, it can also act as a scaffold molecule that binds eIF4A3 and c-Myc mRNA to form complexes in the cytoplasm, thereby promoting the translation of c-Myc. In turn, c-Myc upregulates its downstream targets, including the cell cycle-related factors cyclin D2 and CDK4 and the tight junction-related factor ZEB1, and downregulates E-cadherin, which ultimately promotes the growth and metastasis of CRC. CONCLUSIONS: Our findings revealed that hsa_circRNA_0000467 plays a role in the progression of CRC by promoting eIF4A3-mediated c-Myc translation. This study provides a theoretical basis and molecular target for the diagnosis and treatment of CRC.

Hypoxia-enhanced YAP1-EIF4A3 interaction drives circ_0007386 circularization by competing with CRIM1 pre-mRNA linear splicing and promotes non-small cell lung cancer progression.

BACKGROUND: The progression of non-small cell lung cancer (NSCLC) is significantly influenced by circular RNAs (circRNAs), especially in tumor hypoxia microenvironment. However, the precise functions and underlying mechanisms of dysregulated circRNAs in NSCLC remain largely unexplored. METHODS: Differentially expressed circRNAs in NSCLC tissues were identified through high-throughput RNA sequencing. The characteristics of circ_0007386 were rigorously confirmed via Sanger sequencing, RNase R treatment and actinomycin D treatment. The effects of circ_0007386 on proliferation and apoptosis were investigated using CCK8, cloning formation assays, TUNEL staining, and flow cytometry assays in vitro. In vivo, xenograft tumor models were used to evaluate its impact on proliferation. Mechanistically, the regulatory relationships of circ_0007386, miR-383-5p and CIRBP were examined through dual luciferase reporter assays and rescue experiments. Additionally, we detected the binding of EIF4A3 to CRIM1 pre-mRNA by RNA immunoprecipitation and the interaction between YAP1 and EIF4A3 under hypoxic conditions by co-immunoprecipitation. RESULTS: Our investigation revealed a novel circRNA, designated as circ_0007386, that was upregulated in NSCLC tissues and cell lines. Circ_0007386 modulated proliferation and apoptosis in NSCLC both in vitro and in vivo. Functionally, circ_0007386 acted as a sponge for miR-383-5p, targeting CIRBP, which influenced NSCLC cell proliferation and apoptosis via the PI3K/AKT signaling pathway. Furthermore, under hypoxic conditions, the interaction between YAP1 and EIF4A3 was enhanced, leading to the displacement of EIF4A4 from binding to CRIM1 pre-mRNA. This facilitated the back-splicing of CRIM1 pre-mRNA, increasing the formation of circ_0007386. The circ_0007386/miR-383-5p/CIRBP axis was significantly associated with the clinical features and prognosis of NSCLC patients. CONCLUSIONS: Circ_0007386, regulated by YAP1-EIF4A3 interaction under hypoxia conditions, plays an oncogenic role in NSCLC progression via the miR-383-5p/CIRBP axis.

Extracellular vesicle-delivered hsa_circ_0090081 regulated by EIF4A3 enhances gastric cancer tumorigenesis.

BACKGROUND: Circular RNA (circRNA) and extracellular vesicles (EVs) in tumors are crucial for the malignant phenotype of tumor cells. Nevertheless, the mechanisms and clinical effects of EV-delivered hsa_circ_0090081 in gastric cancer (GC) are unclear. This study aimed to reveal the effect of eukaryotic translation initiation factor 4A3 (EIF4A3)-mediated hsa_circ_0090081 expression and EV-delivered hsa_circ_0090081 on GC progression. METHODS: qRT-PCR was conducted to clarify hsa_circ_0090081 and EIF4A3 levels in GC tissues. Transmission electronic microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting identified the EVs isolated from GC cells by ultracentrifugation. The roles of hsa_circ_0090081, EIF4A3, and EV-delivered hsa_circ_0090081 in GC cells were analyzed using Transwell, EdU, and CCK-8 assays. The regulatory role between EIF4A3 and hsa_circ_0090081 was investigated using RIP, qRT-PCR, and Pearson's analysis. RESULTS: Our study showed that hsa_circ_0090081 and EIF4A3 were highly expressed in GC, and hsa_circ_0090081 was associated with poor prognosis. Data revealed that hsa_circ_0090081 inhibition restrained GC cell proliferation, invasion, and migration. Additionally, EIF4A3 could bind to the pre-mRNA of PHEX (linear form of hsa_circ_0090081) to enhance hsa_circ_0090081 expression in GC cells. Moreover, EIF4A3 overexpression nullified the malignant phenotypic suppression caused by hsa_circ_0090081 silencing in GC cells. Furthermore, EVs secreted by GC cells delivered hsa_circ_0090081 to facilitate the malignant progression of targeted GC cells. CONCLUSION: This study showed that hsa_circ_0090081 was enhanced by EIF4A3 to play a promotive role in GC development. The results may help understand the mechanism of EIF4A3 and EV-delivered hsa_circ_0090081 and offer a valuable GC therapeutic target.

Hsa_circ_0004872 mitigates proliferation, metastasis and immune escape of meningioma cells by suppressing PD-L1.

Meningioma is a prevalent intracranial malignancy known for its aggressive growth. Circular RNAs (circRNAs) play a crucial role in the development of various cancers. However, their involvement in meningioma remains understudied. This study aimed to investigate the function and underlying mechanism of hsa_circ_0004872 in meningioma. The molecular expression of hsa_circ_0004872, PD-L1 and EIF4A3 was identified by RT-qPCR and/or western blot assays. Cell viability, migration, and invasion were assessed through CCK-8 and Transwell assays, respectively. Cytotoxicity was determined using an LDH assay, and cell apoptosis was monitored by flow cytometry. The RNA and protein interactions were assessed through RNA-protein immunoprecipitation (RIP) and RNA pull down analyses. Our findings revealed that hsa_circ_0004872 expression was significantly downregulated in both meningioma tissue samples and cells. Overexpression of hsa_circ_0004872 inhibited the proliferation, metastasis, and immune escape of meningioma cells, as well as enhanced the cytotoxicity of CD8+ T cells by suppressing PD-L1. Furthermore, hsa_circ_0004872 directly interacted with EIF4A3, leading to the degradation of PD-L1 mRNA. Finally, inhibiting EIF4A3 improved the proliferation, metastasis, and immune escape of meningioma cells, as well as the cytotoxicity of CD8+ T cells. Our study demonstrated that hsa_circ_0004872 mitigated the proliferation, metastasis,and immune escape of meningioma cells by targeting the EIF4A3/PD-L1 axis. These findings suggested that hsa_circ_0004872 and EIF4A3 might serve as promising biological markers and therapeutic targets for meningioma treatment.

Regulatory feedback loop between circ-EIF4A3 and EIF4A3 Enhances autophagy and growth in colorectal cancer cells.

Recent studies indicate that circular RNAs (circRNAs) are crucial in the progression of colorectal cancer (CRC). Eukaryotic translation initiation factor 4A3 (EIF4A3) has been identified as a promoter of circRNA production. The biological roles and mechanisms of EIF4A3-derived circRNA (circEIF4A3) in CRC cell autophagy remain poorly understood. This study explores the effects of circEIF4A3 on CRC cell growth and autophagy, aiming to elucidate the underlying molecular mechanisms. We discovered that EIF4A3 and circEIF4A3 synergistically enhance CRC cell growth. CircEIF4A3 sequesters miR-3126-5p, consequently upregulating EIF4A3. Further, circEIF4A3 increases EIF4A3 expression, which promotes autophagy by stabilizing ATG5 mRNA and enhances ATG7 protein stability through the stabilization of USP14 mRNA, a deubiquitinating enzyme. Upregulation of ATG5 and ATG7 counteracts the growth-inhibitory effects of EIF4A3 knockdown on CRC cells. Moreover, our findings demonstrate that EIF4A3 induces the formation of circEIF4A3 in CRC cells. In conclusion, a positive feedback loop between circEIF4A3 and EIF4A3 supports CRC cell growth by facilitating autophagy.

circular RNA circ-231 promotes protein biogenesis of TPI1 and PRDX6 through mediating the interaction of eIF4A3 with STAU1 to facilitate unwinding of secondary structure in 5' UTR, enhancing progression of human esophageal squamous cell carcinoma (ESCC).

Background: The nuclear cap-binding complex (CBC)-dependent translation (CT) is an important initial translation pathway for 5'-cap-dependent translation in normal mammal cells. Eukaryotic translation initiation factor 4A-III (eIF4A3), as an RNA helicase, is recruited to CT complex and enhances CT efficiency through participating in unwinding of secondary structure in the 5' UTR. However, the detailed mechanism for eIF4A3 implicated in unwinding of secondary structure in the 5' UTR in normal mammal cells is still unclear. Specially, we need to investigate whether the kind of mechanism in normal mammal cells extrapolates to cancer cells, e.g. ESCC, and further interrogate whether and how the mechanism triggers malignant phenotype of ESCC, which are important for identifying a potential therapeutic target for patients with ESCC. Methods: Bioinformatics analysis, RNA immunoprecipitation and RNA pulldown assays were performed to detect the interaction of circular RNA circ-231 with eIF4A3. In vitro and in vivo assays were performed to detect biological roles of circ-231 in ESCC. RNA immunoprecipitation, RNA pulldown, mass spectrometry analysis and co-immunoprecipitation assays were used to measure the interaction of circ-231, eIF4A3 and STAU1 in HEK293T and ESCC. In vitro EGFP reporter and 5' UTR of mRNA pulldown assays were performed to probe for the binding of circ-231, eIF4A3 and STAU1 to secondary structure of 5' UTR. Results: RNA immunoprecipitation assays showed that circ-231 interacted with eIF4A3 in HEK293T and ESCC. Further study confirmed that circ-231 orchestrated with eIF4A3 to control protein expression of TPI1 and PRDX6, but not for mRNA transcripts. The in-depth mechanism study uncovered that both circ-231 and eIF4A3 were involved in unwinding of secondary structure in 5' UTR of TPI1 and PRDX6. More importantly, circ-231 promoted the interaction between eIF4A3 and STAU1. Intriguingly, both circ-231 and eIF4A3 were dependent on STAU1 binding to secondary structure in 5' UTR. Biological function assays revealed that circ-231 promoted the migration and proliferation of ESCC via TPI1 and PRDX6. In ESCC, the up-regulated expression of circ-231 was observed and patients with ESCC characterized by higher expression of circ-231 have concurrent lymph node metastasis, compared with control. Conclusions: Our data unravels the detailed mechanism by which STAU1 binds to secondary structure in 5' UTR of mRNAs and recruits eIF4A3 through interacting with circ-231 and thereby eIF4A3 is implicated in unwinding of secondary structure, which is common to HEK293T and ESCC. However, importantly, our data reveals that circ-231 promotes migration and proliferation of ESCC and the up-regulated circ-231 greatly correlates with tumor lymph node metastasis, insinuating that circ-231 could be a therapeutic target and an indicator of risk of lymph node metastasis for patients with ESCC.

Circ_0005615 enhances multiple myeloma progression through interaction with EIF4A3 to regulate MAP3K4 m6A modification mediated by ALKBH5.

BACKGROUND: Circular RNAs (circRNAs) are associated with development and progression of multiple myeloma (MM). However, the role and mechanism of circ_0005615 in MM have not been elucidated. METHODS: Circ_0005615 was determined by GEO database. quantitative RT-PCR was performed to confirm the expression of circ_0005615 in peripheral blood of MM patients and MM cells. The roles of circ_0005615 in MM were analyzed using CCK8, transwell invasion, cell apoptosis and tumor xenograft experiments. Bioinformatics tools, RIP and RNA pull down assays were conducted to explore the downstream of circ_0005615. Furthermore, the mechanism was investigated by quantitative RT-PCR, western blot, dot blot and meRIP-PCR assays. RESULTS: Circ_0005615 was upregulated in MM. Overexpression of circ_0005615 promoted cell viability and invasion, and suppressed apoptosis in vitro, which were opposite when circ_0005615 was knockdowned. Mechanistically, EIF4A3, a RNA-binding protein (RBP), could directly bind to circ_0005615 and ALKBH5, where ALKBH5 could directly combine with MAP3K4, forming a circ_0005615- EIF4A3-ALKBH5-MAP3K4 module. Furthermore, circ_0005615 overexpression increased m6A methylation of MAP3K4 by inhibiting ALKBH5, leading to decreased MAP3K4. Further functional experiments indicated that ALKBH5 overexpression weakened the promoting roles of circ_0005615 overexpression in MAP3K4 m6A methylation and tumor progression in MM. The above functions and mechanism were also verified in vivo. CONCLUSIONS: Elevated circ_0005615 decreased MAP3K4 mediated by ALKBH5 through interacting with EIF4A3, thereby accelerating MM progression. Circ_0005615 might be a promising biomarker and target of MM.