CELF1 is an EIF4E binding protein that promotes translation of epithelial-mesenchymal transition effector mRNAs

AbstractMounting evidence is revealing a granularity within gene regulation that occurs at the level of mRNA translation. Within mammalian cells, canonical cap-dependent mRNA translation is dependent upon the interaction between the m7G cap-binding protein eukaryotic initiation factor 4E (eIF4E) and the scaffolding protein eukaryotic initiation factor 4G (eIF4G), the latter of which facilitates pre-translation initiation complex assembly, mRNA circularization, and ultimately ribosomal scanning. In breast epithelial cells, we previously demonstrated that the CELF1 RNA-binding protein promotes the translation of epithelial to mesenchymal transition (EMT) effector mRNAs containing GU-rich elements (GREs) within their 3’ untranslated regions (UTRs). Here we show that within this context, CELF1 directly binds to both the eIF4E cap-binding protein and Poly(A) binding protein (PABP), promoting translation of GRE-containing mRNAs in mesenchymal cells. Disruption of this CELF1/eIF4E interaction inhibits both EMT induction and experimental metastasis. Our findings illustrate a novel way in which non-canonical mechanisms of translation initiation underlie transitional cellular states within the context of development or human disease.

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CPEB3-mediated MTDH mRNA translational suppression restrains hepatocellular carcinoma progression

Cell Death and Disease ◽

10.1038/s41419-020-02984-y ◽

2020 ◽

Vol 11 (9) ◽

Author(s):

He Zhang ◽

Chendan Zou ◽

Zini Qiu ◽

Fang E ◽

Qiang Li ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Cancer Progression ◽

Rna Binding ◽

Epithelial Mesenchymal Transition ◽

Binding Protein ◽

Mrna Translation ◽

Luciferase Assay ◽

Mesenchymal Transition

Abstract Cytoplasmic polyadenylation element-binding protein 3 (CPEB3) is a sequence-specific RNA-binding protein. We had reported that CPEB3 is involved in hepatocellular carcinoma (HCC) progression. However, the underlying mechanisms of CPEB3 in HCC remain unclear. In this study, we firstly performed RNA immunoprecipitation to uncover the transcriptome-wide CPEB3-bound mRNAs (CPEB3 binder) in HCC. Bioinformatic analysis indicates that CPEB3 binders are closely related to cancer progression, especially HCC metastasis. Further studies confirmed that metadherin (MTDH) is a direct target of CPEB3. CPEB3 can suppress the translation of MTDH mRNA in vivo and in vitro. Besides, luciferase assay demonstrated that CPEB3 interacted with 3′-untranslated region of MTDH mRNA and inhibited its translation. Subsequently, CPEB3 inhibited the epithelial–mesenchymal transition and metastasis of HCC cells through post-transcriptional regulation of MTDH. In addition, cpeb3 knockout mice are more susceptible to carcinogen-induced hepatocarcinogenesis and subsequent lung metastasis. Our results also indicated that CPEB3 was a good prognosis marker, which is downregulated in HCC tissue. In conclusion, our results demonstrated that CPEB3 played an important role in HCC progression and targeting CPEB3-mediated mRNA translation might be a favorable therapeutic approach.

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Epstein-Barr Virus Protein EB2 Stimulates Translation Initiation of mRNAs through Direct Interactions with both Poly(A)-Binding Protein and Eukaryotic Initiation Factor 4G

Journal of Virology ◽

10.1128/jvi.01917-17 ◽

2017 ◽

Vol 92 (3) ◽

Cited By ~ 4

Author(s):

Fabrice Mure ◽

Baptiste Panthu ◽

Isabelle Zanella-Cléon ◽

Frédéric Delolme ◽

Evelyne Manet ◽

...

Keyword(s):

Translation Initiation ◽

Epstein Barr Virus ◽

Rna Binding ◽

Binding Protein ◽

Initiation Factor ◽

Translation Efficiency ◽

Eukaryotic Initiation Factor ◽

Barr Virus ◽

Intronless Genes ◽

Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) expresses several mRNAs produced from intronless genes that could potentially be unfavorably translated compared to cellular spliced mRNAs. To overcome this situation, the virus encodes an RNA-binding protein (RBP) called EB2, which was previously found to both facilitate the export of nuclear mRNAs and increase their translational yield. Here, we show that EB2 binds both nuclear and cytoplasmic cap-binding complexes (CBC and eukaryotic initiation factor 4F [eIF4F], respectively) as well as the poly(A)-binding protein (PABP) to enhance translation initiation of a given messenger ribonucleoparticle (mRNP). Interestingly, such an effect can be obtained only if EB2 is initially bound to the native mRNPs in the nucleus. We also demonstrate that the EB2-eIF4F-PABP association renders translation of these mRNPs less sensitive to translation initiation inhibitors. Taken together, our data suggest that EB2 binds and stabilizes cap-binding complexes in order to increase mRNP translation and furthermore demonstrate the importance of the mRNP assembly process in the nucleus to promote protein synthesis in the cytoplasm. IMPORTANCE Most herpesvirus early and late genes are devoid of introns. However, it is now well documented that mRNA splicing facilitates recruitment on the mRNAs of cellular factors involved in nuclear mRNA export and translation efficiency. To overcome the absence of splicing of herpesvirus mRNAs, a viral protein, EB2 in the case of Epstein-Barr virus, is produced to facilitate the cytoplasmic accumulation of viral mRNAs. Although we previously showed that EB2 also specifically enhances translation of its target mRNAs, the mechanism was unknown. Here, we show that EB2 first is recruited to the mRNA cap structure in the nucleus and then interacts with the proteins eIF4G and PABP to enhance the initiation step of translation.

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Expression and Functional Roles of Eukaryotic Initiation Factor 4A Family Proteins in Human Cancers

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.711965 ◽

2021 ◽

Vol 9 ◽

Author(s):

Chen Xue ◽

Xinyu Gu ◽

Ganglei Li ◽

Zhengyi Bao ◽

Lanjuan Li

Keyword(s):

Epithelial Mesenchymal Transition ◽

Mrna Translation ◽

Initiation Factor ◽

Eukaryotic Initiation Factor ◽

Mesenchymal Transition ◽

Functional Roles ◽

Tumorigenesis And Progression ◽

Cancer Types ◽

Early Tumor ◽

Clinical Grading

The dysregulation of mRNA translation is common in malignancies and may lead to tumorigenesis and progression. Eukaryotic initiation factor 4A (eIF4A) proteins are essential for translation, exhibit bidirectional RNA helicase function, and act as RNA-dependent ATPases. In this review, we explored the predicted structures of the three eIF4A isoforms (eIF4A1, eIF4A2, and eIF4A3), and discussed possible explanations for which function during different translation stages (initiation, mRNA localization, export, and mRNA splicing). These proteins also frequently served as targets of microRNAs (miRNAs) or long noncoding RNAs (lncRNAs) to mediate epithelial-mesenchymal transition (EMT), which was associated with tumor cell invasion and metastasis. To define the differential expression of eIF4A family members, we applied the Tumor Immune Estimation Resource website. We figured out that the eIF4A family genes were differently expressed in specific cancer types. We also found that the level of the eIF4A family genes were associated with abundant immune cells infiltration and tumor purity. The associations between eIF4A proteins and cancer patient clinicopathological features suggested that eIF4A proteins might serve as biomarkers for early tumor diagnosis, histological classification, and clinical grading/staging, providing new tools for precise and individualized cancer treatment.

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Cap-binding protein (eukaryotic initiation factor 4E) and 4E-inactivating protein BP-1 independently regulate cap-dependent translation.

Molecular and Cellular Biology ◽

10.1128/mcb.16.10.5450 ◽

1996 ◽

Vol 16 (10) ◽

pp. 5450-5457 ◽

Cited By ~ 47

Author(s):

D Feigenblum ◽

R J Schneider

Keyword(s):

Heat Shock ◽

Translation Initiation ◽

Binding Protein ◽

Initiation Factor ◽

Eukaryotic Initiation Factor ◽

Metaphase Arrest ◽

Animal Cells ◽

Eukaryotic Initiation Factor 4E ◽

Dependent Protein

Cap-dependent protein synthesis in animal cells is inhibited by heat shock, serum deprivation, metaphase arrest, and infection with certain viruses such as adenovirus (Ad). At a mechanistic level, translation of capped mRNAs is inhibited by dephosphorylation of eukaryotic initiation factor 4E (eIF-4E) (cap-binding protein) and its physical sequestration with the translation repressor protein BP-1 (PHAS-I). Dephosphorylation of BP-I blocks cap-dependent translation by promoting sequestration of eIF-4E. Here we show that heat shock inhibits translation of capped mRNAs by simultaneously inducing dephosphorylation of eIF-4E and BP-1, suggesting that cells might coordinately regulate translation of capped mRNAs by impairing both the activity and the availability of eIF-4E. Like heat shock, late Ad infection is shown to induce dephosphorylation of eIF-4E. However, in contrast to heat shock, Ad also induces phosphorylation of BP-1 and release of eIF-4E. BP-1 and eIF-4E can therefore act on cap-dependent translation in either a mutually antagonistic or cooperative manner. Three sets of experiments further underscore this point: (i) rapamycin is shown to block phosphorylation of BP-1 without inhibiting dephosphorylation of eIF-4E induced by heat shock or Ad infection, (ii) eIF-4E is efficiently dephosphorylated during heat shock or Ad infection regardless of whether it is in a complex with BP-1, and (iii) BP-1 is associated with eIF-4E in vivo regardless of the state of eIF-4E phosphorylation. These and other studies establish that inhibition of cap-dependent translation does not obligatorily involve sequestration of eIF-4E by BP-1. Rather, translation is independently regulated by the phosphorylation states of eIF-4E and the 4E-binding protein, BP-1. In addition, these results demonstrate that BP-1 and eIF-4E can act either in concert or in opposition to independently regulate cap-dependent translation. We suggest that independent regulation of eIF-4E and BP-1 might finely regulate the efficiency of translation initiation or possibly control cap-dependent translation for fundamentally different purposes.

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