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1.
Mol Cell ; 84(11): 2009-2010, 2024 Jun 06.
Artículo en Inglés | MEDLINE | ID: mdl-38848688

RESUMEN

In this issue, Diamond et al.1 and Kim et al.2 report that depletion of eIF4E leads to translational upregulation of GCN4, a key player in the integrated stress response, in an eIF2α phosphorylation-independent manner, suggesting a new mode of translational adaptation.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Estrés Fisiológico , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Fosforilación , Humanos , Factor 2 Eucariótico de Iniciación/metabolismo , Factor 2 Eucariótico de Iniciación/genética , Biosíntesis de Proteínas , Animales , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética
2.
Mol Cell ; 84(11): 2119-2134.e5, 2024 Jun 06.
Artículo en Inglés | MEDLINE | ID: mdl-38848691

RESUMEN

Protein synthesis is metabolically costly and must be tightly coordinated with changing cellular needs and nutrient availability. The cap-binding protein eIF4E makes the earliest contact between mRNAs and the translation machinery, offering a key regulatory nexus. We acutely depleted this essential protein and found surprisingly modest effects on cell growth and recovery of protein synthesis. Paradoxically, impaired protein biosynthesis upregulated genes involved in the catabolism of aromatic amino acids simultaneously with the induction of the amino acid biosynthetic regulon driven by the integrated stress response factor GCN4. We further identified the translational control of Pho85 cyclin 5 (PCL5), a negative regulator of Gcn4, that provides a consistent protein-to-mRNA ratio under varied translation environments. This regulation depended in part on a uniquely long poly(A) tract in the PCL5 5' UTR and poly(A) binding protein. Collectively, these results highlight how eIF4E connects protein synthesis to metabolic gene regulation, uncovering mechanisms controlling translation during environmental challenges.


Asunto(s)
Aminoácidos , Factor 4E Eucariótico de Iniciación , Regulación Fúngica de la Expresión Génica , Biosíntesis de Proteínas , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Aminoácidos/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , ARN Mensajero/metabolismo , ARN Mensajero/genética , Regiones no Traducidas 5' , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/genética , Ciclinas/genética , Ciclinas/metabolismo , Proteínas de Unión a Poli(A)/metabolismo , Proteínas de Unión a Poli(A)/genética
3.
Mol Cell ; 84(11): 2135-2151.e7, 2024 Jun 06.
Artículo en Inglés | MEDLINE | ID: mdl-38848692

RESUMEN

In response to stress, eukaryotes activate the integrated stress response (ISR) via phosphorylation of eIF2α to promote the translation of pro-survival effector genes, such as GCN4 in yeast. Complementing the ISR is the target of rapamycin (TOR) pathway, which regulates eIF4E function. Here, we probe translational control in the absence of eIF4E in Saccharomyces cerevisiae. Intriguingly, we find that loss of eIF4E leads to de-repression of GCN4 translation. In addition, we find that de-repression of GCN4 translation is accompanied by neither eIF2α phosphorylation nor reduction in initiator ternary complex (TC). Our data suggest that when eIF4E levels are depleted, GCN4 translation is de-repressed via a unique mechanism that may involve faster scanning by the small ribosome subunit due to increased local concentration of eIF4A. Overall, our findings suggest that relative levels of eIF4F components are key to ribosome dynamics and may play important roles in translational control of gene expression.


Asunto(s)
Factores de Transcripción con Cremalleras de Leucina de Carácter Básico , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Estrés Fisiológico , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Fosforilación , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/genética , Factor 4F Eucariótico de Iniciación/metabolismo , Factor 4F Eucariótico de Iniciación/genética , Biosíntesis de Proteínas , Regulación Fúngica de la Expresión Génica , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Factor 2 Eucariótico de Iniciación/metabolismo , Factor 2 Eucariótico de Iniciación/genética , Transducción de Señal , Ribosomas/metabolismo , Ribosomas/genética , Factor 4A Eucariótico de Iniciación/metabolismo , Factor 4A Eucariótico de Iniciación/genética
4.
Nucleus ; 15(1): 2360196, 2024 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-38880976

RESUMEN

The eukaryotic translation initiation factor eIF4E acts as a multifunctional factor that simultaneously influences mRNA processing, export, and translation in many organisms. Its multifactorial effects are derived from its capacity to bind to the methyl-7-guanosine cap on the 5'end of mRNAs and thus can act as a cap chaperone for transcripts in the nucleus and cytoplasm. In this review, we describe the multifactorial roles of eIF4E in major mRNA-processing events including capping, splicing, cleavage and polyadenylation, nuclear export and translation. We discuss the evidence that eIF4E acts at two levels to generate widescale changes to processing, export and ultimately the protein produced. First, eIF4E alters the production of components of the mRNA processing machinery, supporting a widescale reprogramming of multiple mRNA processing events. In this way, eIF4E can modulate mRNA processing without physically interacting with target transcripts. Second, eIF4E also physically interacts with both capped mRNAs and components of the RNA processing or translation machineries. Further, specific mRNAs are sensitive to eIF4E only in particular mRNA processing events. This selectivity is governed by the presence of cis-acting elements within mRNAs known as USER codes that recruit relevant co-factors engaging the appropriate machinery. In all, we describe the molecular bases for eIF4E's multifactorial function and relevant regulatory pathways, discuss the basis for selectivity, present a compendium of ~80 eIF4E-interacting factors which play roles in these activities and provide an overview of the relevance of its functions to its oncogenic potential. Finally, we summarize early-stage clinical studies targeting eIF4E in cancer.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Biosíntesis de Proteínas , ARN Mensajero , Humanos , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , ARN Mensajero/metabolismo , ARN Mensajero/genética , Animales , Transporte de ARN , Procesamiento Postranscripcional del ARN
5.
J Clin Invest ; 134(9)2024 05 01.
Artículo en Inglés | MEDLINE | ID: mdl-38690739
6.
mBio ; 15(6): e0295423, 2024 Jun 12.
Artículo en Inglés | MEDLINE | ID: mdl-38747593

RESUMEN

The protozoan parasite Toxoplasma gondii causes serious opportunistic disease due to its ability to persist in patients as latent tissue cysts. The molecular mechanisms coordinating conversion between proliferative parasites (tachyzoites) and latent cysts (bradyzoites) are not fully understood. We previously showed that phosphorylation of eIF2α accompanies bradyzoite formation, suggesting that this clinically relevant process involves regulation of mRNA translation. In this study, we investigated the composition and role of eIF4F multi-subunit complexes in translational control. Using CLIPseq, we find that the cap-binding subunit, eIF4E1, localizes to the 5'-end of all tachyzoite mRNAs, many of which show evidence of stemming from heterogeneous transcriptional start sites. We further show that eIF4E1 operates as the predominant cap-binding protein in two distinct eIF4F complexes. Using genetic and pharmacological approaches, we found that eIF4E1 deficiency triggers efficient spontaneous formation of bradyzoites without stress induction. Consistent with this result, we also show that stress-induced bradyzoites exhibit reduced eIF4E1 expression. Overall, our findings establish a novel role for eIF4F in translational control required for parasite latency and microbial persistence. IMPORTANCE: Toxoplasma gondii is an opportunistic pathogen important to global human and animal health. There are currently no chemotherapies targeting the encysted form of the parasite. Consequently, a better understanding of the mechanisms controlling encystation is required. Here we show that the mRNA cap-binding protein, eIF4E1, regulates the encystation process. Encysted parasites reduce eIF4E1 levels, and depletion of eIF4E1 decreases the translation of ribosome-associated machinery and drives Toxoplasma encystation. Together, these data reveal a new layer of mRNA translational control that regulates parasite encystation and latency.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Proteínas Protozoarias , ARN Mensajero , Toxoplasma , Toxoplasma/genética , Toxoplasma/metabolismo , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/genética , ARN Mensajero/metabolismo , ARN Mensajero/genética , Biosíntesis de Proteínas , Factor 4F Eucariótico de Iniciación/metabolismo , Factor 4F Eucariótico de Iniciación/genética , Humanos , Animales , Ratones , Toxoplasmosis/parasitología , Toxoplasmosis/metabolismo
7.
Cancer Lett ; 593: 216939, 2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38729556

RESUMEN

Helicobacter pylori (H. pylori) infection is the main risk factor for gastric cancer. The SRY-Box Transcription Factor 9 (SOX9) serves as a marker of stomach stem cells. We detected strong associations between AURKA and SOX9 expression levels in gastric cancers. Utilizing in vitro and in vivo mouse models, we demonstrated that H. pylori infection induced elevated levels of both AURKA and SOX9 proteins. Notably, the SOX9 protein and transcription activity levels were dependent on AURKA expression. AURKA knockdown led to a reduction in the number and size of gastric gland organoids. Conditional knockout of AURKA in mice resulted in a decrease in SOX9 baseline level in AURKA-knockout gastric glands, accompanied by diminished SOX9 induction following H. pylori infection. We found an AURKA-dependent increase in EIF4E and cap-dependent translation with an AURKA-EIF4E-dependent increase in SOX9 polysomal RNA levels. Immunoprecipitation assays demonstrated binding of AURKA to EIF4E with a decrease in EIF4E ubiquitination. Immunohistochemistry analysis on tissue arrays revealed moderate to strong immunostaining of AURKA and SOX9 with a significant correlation in gastric cancer tissues. These findings elucidate the mechanistic role of AURKA in regulating SOX9 levels via cap-dependent translation in response to H. pylori infection in gastric tumorigenesis.


Asunto(s)
Aurora Quinasa A , Factor 4E Eucariótico de Iniciación , Infecciones por Helicobacter , Helicobacter pylori , Factor de Transcripción SOX9 , Neoplasias Gástricas , Animales , Infecciones por Helicobacter/metabolismo , Infecciones por Helicobacter/microbiología , Infecciones por Helicobacter/genética , Factor de Transcripción SOX9/metabolismo , Factor de Transcripción SOX9/genética , Humanos , Neoplasias Gástricas/microbiología , Neoplasias Gástricas/patología , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismo , Aurora Quinasa A/metabolismo , Aurora Quinasa A/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Ratones Noqueados , Ratones , Biosíntesis de Proteínas , Línea Celular Tumoral , Regulación Neoplásica de la Expresión Génica , Ubiquitinación
8.
Mol Cells ; 47(4): 100049, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38513766

RESUMEN

Translation of messenger ribonucleic acids (mRNAs) encoding integral membrane proteins or secreted proteins occurs on the surface of the endoplasmic reticulum (ER). When a nascent signal peptide is synthesized from the mRNAs, the ribosome-nascent chain complex (RNC) is recognized by the signal recognition particle (SRP) and then transported to the surface of the ER. The appropriate targeting of the RNC-SRP complex to the ER is monitored by a quality control pathway, a nuclear cap-binding complex (CBC)-ensured translational repression of RNC-SRP (CENTRE). In this study, using ribosome profiling of CBC-associated and eukaryotic translation initiation factor 4E-associated mRNAs, we reveal that, at the transcriptomic level, CENTRE is in charge of the translational repression of the CBC-RNC-SRP until the complex is specifically transported to the ER. We also find that CENTRE inhibits the nonsense-mediated mRNA decay (NMD) of mRNAs within the CBC-RNC-SRP. The NMD occurs only after the CBC-RNC-SRP is targeted to the ER and after eukaryotic translation initiation factor 4E replaces CBC. Our data indicate dual surveillance for properly targeting mRNAs encoding integral membrane or secretory proteins to the ER. CENTRE blocks gene expression at the translation level before the CBC-RNC-SRP delivery to the ER, and NMD monitors mRNA quality after its delivery to the ER.


Asunto(s)
Retículo Endoplásmico , Degradación de ARNm Mediada por Codón sin Sentido , ARN Mensajero , Partícula de Reconocimiento de Señal , Retículo Endoplásmico/metabolismo , ARN Mensajero/metabolismo , ARN Mensajero/genética , Humanos , Partícula de Reconocimiento de Señal/metabolismo , Partícula de Reconocimiento de Señal/genética , Señales de Clasificación de Proteína/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Células HeLa , Ribosomas/metabolismo , Complejo Proteico Nuclear de Unión a la Caperuza/metabolismo , Complejo Proteico Nuclear de Unión a la Caperuza/genética , Biosíntesis de Proteínas
9.
Mol Oncol ; 18(6): 1397-1416, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38429970

RESUMEN

The effect of grainyhead-like transcription factor 3 (GRHL3) on cancer development depends on the cancer subtypes as shown in tumor entities such as colorectal or oral squamous cell carcinomas. Here, we analyzed the subtype-specific role of GRHL3 in bladder carcinogenesis, comparing common urothelial carcinoma (UC) with squamous bladder cancer (sq-BLCA). We examined GRHL3 mRNA and protein expression in cohorts of patient samples, its prognostic role and its functional impact on tumorigeneses in different molecular and histopathological subtypes of bladder cancer. We showed for GRHL3 a reverse expression in squamous and urothelial bladder cancer subtypes. Stably GRHL3-overexpressing EJ28, J82, and SCaBER in vitro models revealed a tumor-suppressive function in squamous and an oncogenic role in the urothelial cancer cells affecting cell and colony growth, and migratory and invasive capacities. Transcriptomic profiling demonstrated highly subtype-specific GRHL3-regulated expression networks coined by the enrichment of genes involved in integrin-mediated pathways. In SCaBER, loss of ras homolog family member A (RHOA) GTPase activity was demonstrated to be associated with co-regulation of eukaryotic translation initiation factor 4E family member 3 (EIF4E3), a potential tumor suppressor gene. Thus, our data provide for the first time a detailed insight into the role of the transcription factor GRHL3 in different histopathological subtypes of bladder cancer.


Asunto(s)
Carcinogénesis , Proteínas de Unión al ADN , Regulación Neoplásica de la Expresión Génica , Factores de Transcripción , Neoplasias de la Vejiga Urinaria , Neoplasias de la Vejiga Urinaria/genética , Neoplasias de la Vejiga Urinaria/patología , Neoplasias de la Vejiga Urinaria/metabolismo , Humanos , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Línea Celular Tumoral , Carcinogénesis/genética , Carcinogénesis/patología , Femenino , Masculino , Proteína de Unión al GTP rhoA/metabolismo , Proteína de Unión al GTP rhoA/genética , Movimiento Celular/genética , Proliferación Celular/genética , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/patología , Carcinoma de Células Escamosas/metabolismo , Pronóstico , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Anciano
10.
Mol Cell ; 84(9): 1727-1741.e12, 2024 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-38547866

RESUMEN

Heat-shocked cells prioritize the translation of heat shock (HS) mRNAs, but the underlying mechanism is unclear. We report that HS in budding yeast induces the disassembly of the eIF4F complex, where eIF4G and eIF4E assemble into translationally arrested mRNA ribonucleoprotein particles (mRNPs) and HS granules (HSGs), whereas eIF4A promotes HS translation. Using in vitro reconstitution biochemistry, we show that a conformational rearrangement of the thermo-sensing eIF4A-binding domain of eIF4G dissociates eIF4A and promotes the assembly with mRNA into HS-mRNPs, which recruit additional translation factors, including Pab1p and eIF4E, to form multi-component condensates. Using extracts and cellular experiments, we demonstrate that HS-mRNPs and condensates repress the translation of associated mRNA and deplete translation factors that are required for housekeeping translation, whereas HS mRNAs can be efficiently translated by eIF4A. We conclude that the eIF4F complex is a thermo-sensing node that regulates translation during HS.


Asunto(s)
Factor 4F Eucariótico de Iniciación , Factor 4G Eucariótico de Iniciación , Respuesta al Choque Térmico , Proteínas de Unión a Poli(A) , Biosíntesis de Proteínas , ARN Mensajero , Ribonucleoproteínas , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Respuesta al Choque Térmico/genética , Factor 4F Eucariótico de Iniciación/metabolismo , Factor 4F Eucariótico de Iniciación/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factor 4G Eucariótico de Iniciación/metabolismo , Factor 4G Eucariótico de Iniciación/genética , Ribonucleoproteínas/metabolismo , Ribonucleoproteínas/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Factor 4A Eucariótico de Iniciación/metabolismo , Factor 4A Eucariótico de Iniciación/genética , Regulación Fúngica de la Expresión Génica , Unión Proteica , ARN de Hongos/metabolismo , ARN de Hongos/genética
11.
Phys Chem Chem Phys ; 26(14): 10660-10672, 2024 Apr 03.
Artículo en Inglés | MEDLINE | ID: mdl-38511550

RESUMEN

The cap-dependent mRNA translation is dysregulated in many kinds of cancers. The interaction between eIF4E and eIF4G through a canonical eIF4E-binding motif (CEBM) determines the efficacy of the cap-dependent mRNA translation. eIF4E-binding proteins (4E-BPs) share the CEBM and compete with eIF4G for the same binding surface of eIF4E and then inhibit the mRNA translation. 4E-BPs function as tumor repressors in nature. Hyperphosphorylation of 4E-BPs regulates the structure folding and causes the dissociation of 4E-BPs from eIF4E. However, until now, there has been no structure of the full-length 4E-BPs in complex with eIF4E. The regulation mechanism of phosphorylation is still unclear. In this work, we first investigate the interactions of human eIF4E with the CEBM and an auxiliary eIF4E-binding motif (AEBM) in eIF4G and 4E-BPs. The results unravel that the structure and interactions of the CEBM are highly conserved between eIF4G and 4E-BPs. However, the extended CEBM (ECEBM) in 4E-BPs forms a longer helix than that in eIF4G. The residue R62 in the ECEBM of 4E-BP2 forms salt bridges with E32 and E70 of eIF4E. The residue R63 of 4E-BP2 forms two special hydrogen bonds with N77 of eIF4E. Both of these interactions are missing in eIF4G. The AEBM of 4E-BPs folds into a ß-sheet conformation, which protects V81 inside a hydrophobic core in 4E-BP2. In eIF4G, the AEBM exists in a random coil state. The hydrophilic residues S637 and D638 of eIF4G open the hydrophobic core for solvents. The results show that the ECEBM and AEBM may be responsible for the competing advantage of 4E-BP2. Finally, based on our previous work (J. Zeng, F. Jiang and Y. D. Wu, J. Chem. Theory Comput., 2017, 13, 320), the human eIF4E:4E-BP2 complex (eIF4E:BP2P18-I88) including all reported phosphorylation sites is predicted. The eIF4E:BP2P18-I88 complex is different from the existing experimental eIF4E:eIF4G complex and provides an important structure for further studying the regulation mechanism of phosphorylation in 4E-BPs.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Factor 4G Eucariótico de Iniciación , Humanos , Proteínas Portadoras/metabolismo , Factor 4E Eucariótico de Iniciación/química , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Factor 4G Eucariótico de Iniciación/química , Factor 4G Eucariótico de Iniciación/genética , Factor 4G Eucariótico de Iniciación/metabolismo , Unión Proteica , Biosíntesis de Proteínas
12.
Sci Rep ; 14(1): 4237, 2024 02 20.
Artículo en Inglés | MEDLINE | ID: mdl-38378793

RESUMEN

Eukaryotic initiation factor 4E (eIF4E) is a pivotal protein involved in the regulatory mechanism for global protein synthesis in both physiological and pathological conditions. MicroRNAs (miRNAs) play a significant role in regulating gene expression by targeting mRNA. However, the ability of miRNAs to regulate eIF4E and its phosphorylation remains relatively unknown. In this study, we predicted and experimentally verified targets for miR-483-5p, including eukaryotic translation initiation factor eIF4E and its binding proteins, 4E-BPs, that regulate protein synthesis. Using the Web of Science database, we identified 28 experimentally verified miR-483-5p targets, and by the TargetScan database, we found 1818 predicted mRNA targets, including EIF4E, EIF4EBP1, and EIF4EBP2. We verified that miR-483-5p significantly reduced ERK1 and MKNK1 mRNA levels in HEK293 cells. Furthermore, we discovered that miR-483-5p suppressed EIF4EBP1 and EIF4EBP2, but not EIF4E. Finally, we found that miR-483-5p reduced the level of phosphorylated eIF4E (pSer209eIF4E) but not total eIF4E. In conclusion, our study suggests that miR-483-5p's multi-targeting effect on the ERK1/ MKNK1 axis modulates the phosphorylation state of eIF4E. Unlike siRNA, miRNA can have multiple targets in the pathway, and thereby exploring the role of miR-483-5p in various cancer models may uncover therapeutic options.


Asunto(s)
Factor 4E Eucariótico de Iniciación , MicroARNs , Humanos , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Células HEK293 , Péptidos y Proteínas de Señalización Intracelular/metabolismo , MicroARNs/genética , MicroARNs/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosforilación , Proteínas Serina-Treonina Quinasas/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo
13.
Proc Natl Acad Sci U S A ; 121(5): e2313589121, 2024 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-38266053

RESUMEN

The canonical eukaryotic initiation factor 4F (eIF4F) complex, composed of eIF4G1, eIF4A1, and the cap-binding protein eIF4E, plays a crucial role in cap-dependent translation initiation in eukaryotic cells. An alternative cap-independent initiation can occur, involving only eIF4G1 and eIF4A1 through internal ribosome entry sites (IRESs). This mechanism is considered complementary to cap-dependent initiation, particularly in tumors under stress conditions. However, the selection and molecular mechanism of specific translation initiation remains poorly understood in human cancers. Thus, we analyzed gene copy number variations (CNVs) in TCGA tumor samples and found frequent amplification of genes involved in translation initiation. Copy number gains in EIF4G1 and EIF3E frequently co-occur across human cancers. Additionally, EIF4G1 expression strongly correlates with genes from cancer cell survival pathways including cell cycle and lipogenesis, in tumors with EIF4G1 amplification or duplication. Furthermore, we revealed that eIF4G1 and eIF4A1 protein levels strongly co-regulate with ribosomal subunits, eIF2, and eIF3 complexes, while eIF4E co-regulates with 4E-BP1, ubiquitination, and ESCRT proteins. Utilizing Alphafold predictions, we modeled the eIF4F structure with and without eIF4E binding. For cap-dependent initiation, our modeling reveals extensive interactions between the N-terminal eIF4E-binding domain of eIF4G1 and eIF4E. Furthermore, the eIF4G1 HEAT-2 domain positions eIF4E near the eIF4A1 N-terminal domain (NTD), resulting in the collaborative enclosure of the RNA binding cavity within eIF4A1. In contrast, during cap-independent initiation, the HEAT-2 domain directly binds the eIF4A1-NTD, leading to a stronger interaction between eIF4G1 and eIF4A1, thus closing the mRNA binding cavity without the involvement of eIF4E.


Asunto(s)
Factor 4F Eucariótico de Iniciación , Neoplasias , Humanos , Factor 4F Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/genética , Variaciones en el Número de Copia de ADN , Factor 3 de Iniciación Eucariótica , Neoplasias/genética
14.
Mol Plant Pathol ; 25(1): e13418, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38279849

RESUMEN

Eukaryotic translation initiation factor 4E (eIF4E), which plays a pivotal role in initiating translation in eukaryotic organisms, is often hijacked by the viral genome-linked protein to facilitate the infection of potyviruses. In this study, we found that the naturally occurring amino acid substitution D71G in eIF4E is widely present in potyvirus-resistant watermelon accessions and disrupts the interaction between watermelon eIF4E and viral genome-linked protein of papaya ringspot virus-watermelon strain, zucchini yellow mosaic virus or watermelon mosaic virus. Multiple sequence alignment and protein modelling showed that the amino acid residue D71 located in the cap-binding pocket of eIF4E is strictly conserved in many plant species. The mutation D71G in watermelon eIF4E conferred resistance against papaya ringspot virus-watermelon strain and zucchini yellow mosaic virus, and the equivalent mutation D55G in tobacco eIF4E conferred resistance to potato virus Y. Therefore, our finding provides a potential precise target for breeding plants resistant to multiple potyviruses.


Asunto(s)
Aminoácidos , Potyvirus , Secuencia de Aminoácidos , Sustitución de Aminoácidos/genética , Aminoácidos/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Enfermedades de las Plantas/genética , Potyvirus/genética , Potyvirus/metabolismo , Citrullus/virología
15.
EMBO Rep ; 25(1): 404-427, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38177902

RESUMEN

Maternal mRNAs are essential for protein synthesis during oogenesis and early embryogenesis. To adapt translation to specific needs during development, maternal mRNAs are translationally repressed by shortening the polyA tails. While mRNA deadenylation is associated with decapping and degradation in somatic cells, maternal mRNAs with short polyA tails are stable. Here we report that the germline-specific eIF4E paralog, eIF4E1b, is essential for zebrafish oogenesis. eIF4E1b localizes to P-bodies in zebrafish embryos and binds to mRNAs with reported short or no polyA tails, including histone mRNAs. Loss of eIF4E1b results in reduced histone mRNA levels in early gonads, consistent with a role in mRNA storage. Using mouse and human eIF4E1Bs (in vitro) and zebrafish eIF4E1b (in vivo), we show that unlike canonical eIF4Es, eIF4E1b does not interact with eIF4G to initiate translation. Instead, eIF4E1b interacts with the translational repressor eIF4ENIF1, which is required for eIF4E1b localization to P-bodies. Our study is consistent with an important role of eIF4E1b in regulating mRNA dormancy and provides new insights into fundamental post-transcriptional regulatory principles governing early vertebrate development.


Asunto(s)
ARN Mensajero Almacenado , Pez Cebra , Animales , Humanos , Ratones , ARN Mensajero Almacenado/genética , ARN Mensajero Almacenado/metabolismo , Pez Cebra/genética , Pez Cebra/metabolismo , Histonas/metabolismo , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Biosíntesis de Proteínas
16.
Exp Dermatol ; 33(1): e14997, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38284198

RESUMEN

Psoriasis is a complex inflammatory skin disease with uncertain pathogenesis. eIF4E (eukaryotic translation initiation factor 4E) and its phosphorylation state p-eIF4E are highly expressed in psoriatic tissues. However, the role eIF4E played in psoriasis is still unclear. To investigate the function of eIF4E and p-eIF4E in psoriasis and to figure out whether eFT-508 (Tomivosertib, eIF4E phosphorylation inhibitor) can relieve the disease severity and become a promising candidate for the psoriasis treatment. We first verified the expression of eIF4E and p-eIF4E in psoriasis patients' lesional skin. Then, we demonstrated the effect of eIF4E and p-eIF4E on the abnormal proliferation and inflammatory state of keratinocytes by using eIF4E-specific small interfering RNA (si-eIF4E) and eFT-508. In this study, all cell experiments were performed under the psoriasis-model condition. Moreover, the external application of eFT-508 on imiquimod (IMQ)-induced psoriasis mice was performed to explore its potential clinical value. Results showed that eIF4E and p-eIF4E were significantly overexpressed in skin lesions of psoriasis patients. Knocking down eIF4E or adding eFT-508 can relieve the abnormal proliferation and the excessive inflammatory state of keratinocytes by reducing the expression of cyclin D1, IL-1ß, CXCL10, IL23, Wnt 5a, NBS1 and p-AKT from mRNA or protein levels. Furthermore, these results were consistent with those obtained from the in vitro experiments. Then, we conclude that eIF4E plays the role of the pathogenic gene in psoriasis, and eFT-508 may be a promising candidate for anti-prosoriasis drugs.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Psoriasis , Animales , Humanos , Ratones , Modelos Animales de Enfermedad , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Imiquimod/efectos adversos , Queratinocitos/metabolismo , Fosforilación , Psoriasis/tratamiento farmacológico , Psoriasis/genética , Psoriasis/metabolismo , Piel/metabolismo
17.
Int J Biol Macromol ; 254(Pt 3): 128062, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-37967597

RESUMEN

Some viral proteins are translated cap-independently via the internal ribosome entry site (IRES), which maintains conservative characteristic among different isolates of the same virus species. However, IRES activity showed a 7-fold variance in RNA2 of wheat yellow mosaic virus (WYMV) HC and LYJN isolates in this study. Based on RNA structure probing and mutagenesis assay, the loosened middle stem of H1 and the hepta-nucleotide top loop of H2 in the LYJN isolate synergistically ensured higher IRES activity than that in the HC isolate. In addition, the conserved top loop of H1 ensured basic IRES activity in HC and LYJN isolates. WYMV RNA2 5'-UTR specifically interacted with the wheat eIF4E, accomplished by the top loop of H1 in the HC isolate or the top loop of H1 and H2 in the LYJN isolate. The high IRES activity of the WYMV RNA2 LYJN isolate was regulated by two eIF4E-binding sites, which showed a synergistic effect mediated by the proximity of the H1 and H2 top loops owing to the flexibility of the middle stem in H1. This report presents a novel evolution pattern of IRES, which altered the number of eIF4E-binding sites to regulate IRES activity.


Asunto(s)
Virus del Mosaico , Biosíntesis de Proteínas , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Sitios Internos de Entrada al Ribosoma/genética , Triticum/genética , Triticum/metabolismo , Sitios de Unión , Virus del Mosaico/genética , Virus del Mosaico/metabolismo , ARN Viral/genética
18.
J Invest Dermatol ; 144(3): 500-508.e3, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-37865179

RESUMEN

Eukaryotic initiation factor 4E (eIF4E) has been known to play a critical role in the regulation of gene expression and essential cellular processes, such as proliferation, apoptosis and differentiation. In this study, we explored its role in the pathophysiology of psoriasis. The inhibition of eIF4E by small interfering RNA or briciclib, an eIF4E small molecule inhibitor, downregulated the expression of eIF4E itself and its two complex partners eIF4A and G, as well as other eIFs (eg, eIF1A, eIF2α, eIF3A, eIF3B, eIF5, and eIF6). This inhibition also abolished psoriatic inflammation in both the imiquimod and TGFß mouse model, as well as in a human 3 dimensional-psoriasis tissue model. Downregulation of eIF4E and the other eIFs by application of briciclib (particularly when given topically) was linked to the normalization of cellular proliferation, epidermal hyperplasia, levels of proinflammatory cytokines (eg, TNFα, IL-1b, IL-17, and IL-22), and keratinocyte differentiation markers (eg, KRT16 and FLG). These results demonstrate translational imbalance and underline the crucial role played by eIF4E and other eIFs in the pathophysiology of psoriasis. This work opens up avenues for the development of novel topical antipsoriatic treatment strategies by targeting eIF4E.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Psoriasis , Animales , Ratones , Humanos , Factor 4E Eucariótico de Iniciación/genética , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Procesamiento Proteico-Postraduccional , Psoriasis/tratamiento farmacológico
19.
Adv Biol (Weinh) ; 8(2): e2300494, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-37997253

RESUMEN

The nuanced heterogeneity and specialized functions of translation machinery are increasingly recognized as crucial for precise translational regulation. Here, high-throughput ribosomal profiling (ribo-seq) is used to analyze the specialized roles of eukaryotic initiation factors (eIFs) in the budding yeast. By examining changes in ribosomal distribution across the genome resulting from knockouts of eIF4A, eIF4B, eIF4G1, CAF20, or EAP1, or knockdowns of eIF1, eIF1A, eIF4E, or PAB1, two distinct initiation-factor groups, the "looping" and "scanning" groups are discerned, based on similarities in the ribosomal landscapes their perturbation induced. The study delves into the cis-regulatory sequence features of genes influenced predominantly by each group, revealing that genes more dependent on the looping-group factors generally have shorter transcripts and poly(A) tails. In contrast, genes more dependent on the scanning-group factors often possess upstream open reading frames and exhibit a higher GC content in their 5' untranslated regions. From the ribosomal RNA fragments identified in the ribo-seq data, ribosomal heterogeneity associated with perturbation of specific initiation factors is further identified, suggesting their potential roles in regulating ribosomal components. Collectively, the study illuminates the complexity of translational regulation driven by heterogeneity and specialized functions of translation machinery, presenting potential approaches for targeted gene translation manipulation.


Asunto(s)
Perfilado de Ribosomas , Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , ARN Mensajero/genética , Ribosomas/genética , Factor 4E Eucariótico de Iniciación/genética
20.
Bioessays ; 46(1): e2300145, 2024 01.
Artículo en Inglés | MEDLINE | ID: mdl-37926700

RESUMEN

Recent findings position the eukaryotic translation initiation factor eIF4E as a novel modulator of mRNA splicing, a process that impacts the form and function of resultant proteins. eIF4E physically interacts with the spliceosome and with some intron-containing transcripts implying a direct role in some splicing events. Moreover, eIF4E drives the production of key components of the splicing machinery underpinning larger scale impacts on splicing. These drive eIF4E-dependent reprogramming of the splicing signature. This work completes a series of studies demonstrating eIF4E acts in all the major mRNA maturation steps whereby eIF4E drives production of the RNA processing machinery and escorts some transcripts through various maturation steps. In this way, eIF4E couples the mRNA processing-export-translation axis linking nuclear mRNA processing to cytoplasmic translation. eIF4E elevation is linked to worse outcomes in acute myeloid leukemia patients where these activities are dysregulated. Understanding these effects provides new insight into post-transcriptional control and eIF4E-driven cancers.


Asunto(s)
Factor 4E Eucariótico de Iniciación , Leucemia Mieloide Aguda , Humanos , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Regulación de la Expresión Génica , Empalme del ARN/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo
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