Translation reinitiation is a gene-specific translational control mechanism. It is characterized by the ability of short upstream ORFs to prevent full ribosomal recycling and allow the post-termination 40S subunit to resume traversing downstream for the next initiation event. It is well known that variable transcript-specific features of various uORFs and their prospective interactions with initiation factors lend them an unequivocal regulatory potential. Here, we investigated the proposed role of the major initiation scaffold protein eIF4G in reinitiation and its prospective interactions with uORF's cis-acting features in yeast. In analogy to the eIF3 complex, we found that eIF4G and eIF4A but not eIF4E (all constituting the eIF4F complex) are preferentially retained on ribosomes elongating and terminating on reinitiation-permissive uORFs. The loss of the eIF4G contact with eIF4A specifically increased this retention and, as a result, increased the efficiency of reinitiation on downstream initiation codons. Combining the eIF4A-binding mutation with that affecting the integrity of the eIF4G1-RNA2-binding domain eliminated this specificity and produced epistatic interaction with a mutation in one specific cis-acting feature. We conclude that similar to humans, eIF4G is retained on ribosomes elongating uORFs to control reinitiation also in yeast.

• MeSH
• DEAD-box RNA-helikasy genetika   MeSH
• eukaryotický iniciační faktor 3 genetika   MeSH
• eukaryotický iniciační faktor 4E genetika   MeSH
• eukaryotický iniciační faktor 4G genetika   MeSH
• iniciace translace peptidového řetězce genetika   MeSH
• kodon iniciační genetika   MeSH
• lidé MeSH
• otevřené čtecí rámce genetika   MeSH
• proteosyntéza genetika   MeSH
• ribozomy genetika   MeSH
• Saccharomyces cerevisiae - proteiny genetika   MeSH
• Saccharomyces cerevisiae genetika   MeSH
• transkripční faktory bZIP genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Alternative polyadenylation is an important and pervasive mechanism that generates heterogeneous 3'-termini of mRNA and is considered an important regulator of gene expression. We performed bioinformatics analyses of ESTs and the 3'-UTRs of the main transcript splice variants of the translational initiation factor eIF4E1 and its family members, eIF4E2 and eIF4E3. This systematic analysis led to the prediction of new polyadenylation signals. All identified polyadenylation sites were subsequently verified by 3'RACE of transcripts isolated from human lymphoblastic cell lines. This led to the observation that multiple simultaneous polyadenylation site utilization occurs in single cell population. Importantly, we described the use of new polyadenylation site in the eIF4E1 mRNA, which lacked any known polyadenylation signal. The proportion of eIF4E1 transcripts derived from the first two polyadenylation sites in eIF4E1 mRNA achieved 15% in a wide range of cell lines. This result demonstrates the ubiquitous presence of ARE-lacking transcripts, which escape HuR/Auf1-mediated control, the main mechanism of eIF4E1 gene expression regulation. We found many EST clones documenting the significant production of transcript variants 2-4 of eIF4E2 gene that encode proteins with C-termini that were distinct from the mainly studied prototypical isoform A. Similarly, eIF4E3 mRNAs are produced as two main variants with the same very long 3'-UTR with potential for heavy post-transcriptional regulation. We identified sparsely documented transcript variant 1 of eIF4E3 gene in human placenta. eIF4E3 truncated transcript variants were found mainly in brain. We propose to elucidate the minor splice variants of eIF4E2 and eIF4E3 in great detail because they might produce proteins with modified features that fulfill different cellular roles from their major counterparts.

• MeSH
• 3' nepřekládaná oblast MeSH
• buněčné linie MeSH
• eukaryotický iniciační faktor 4E genetika   metabolismus   MeSH
• exprimované sekvenční adresy MeSH
• lidé MeSH
• messenger RNA genetika   metabolismus   MeSH
• mozek metabolismus   MeSH
• placenta metabolismus   MeSH
• polyadenylace genetika   MeSH
• proteiny vázající čepičku mRNA genetika   MeSH
• regulace genové exprese MeSH
• sestřih RNA genetika   MeSH
• těhotenství MeSH
• Check Tag
• lidé MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

Elevated levels of eukaryotic initiation factor 4E (eIF4E) are implicated in neoplasia, with cumulative evidence pointing to its role in the etiopathogenesis of hematological diseases. As a node of convergence for several oncogenic signaling pathways, eIF4E has attracted a great deal of interest from biologists and clinicians whose efforts have been targeting this translation factor and its biological circuits in the battle against leukemia. The role of eIF4E in myeloid leukemia has been ascertained and drugs targeting its functions have found their place in clinical trials. Little is known, however, about the pertinence of eIF4E to the biology of lymphocytic leukemia and a paucity of literature is available in this regard that prospectively evaluates the topic to guide practice in hematological cancer. A comprehensive analysis on the significance of eIF4E translation factor in the clinical picture of leukemia arises, therefore, as a compelling need. This review presents aspects of eIF4E involvement in the realm of the lymphoblastic leukemia status; translational control of immunological function via eIF4E and the state-of-the-art in drugs will also be outlined.

• MeSH
• antitumorózní látky farmakologie   terapeutické užití   MeSH
• eukaryotický iniciační faktor 4E metabolismus   MeSH
• lidé MeSH
• lymfoidní leukemie farmakoterapie   metabolismus   MeSH
• regulace genové exprese u leukemie * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Although the involvement of the extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in the regulation of cytostatic factor (CSF) activity; as well as in microtubules organization during meiotic maturation of oocytes; has already been described in detail; rather less attention has been paid to the role of ERK1/2 in the regulation of mRNA translation. However; important data on the role of ERK1/2 in translation during oocyte meiosis have been documented. This review focuses on recent findings regarding the regulation of translation and the role of ERK1/2 in this process in the meiotic cycle of mammalian oocytes. The specific role of ERK1/2 in the regulation of mammalian target of rapamycin (mTOR); eukaryotic translation initiation factor 4E (eIF4E) and cytoplasmic polyadenylation element binding protein 1 (CPEB1) activity is addressed along with additional focus on the other key players involved in protein translation.

• MeSH
• cytoplazma genetika   metabolismus   MeSH
• eukaryotický iniciační faktor 4E metabolismus   MeSH
• faktory štěpení a polyadenylace mRNA metabolismus   MeSH
• fosfatidylinositol-3-kinasy metabolismus   MeSH
• lidé MeSH
• meióza * MeSH
• messenger RNA genetika   metabolismus   MeSH
• mitogenem aktivovaná proteinkinasa 1 metabolismus   MeSH
• mitogenem aktivovaná proteinkinasa 3 metabolismus   MeSH
• mitogenem aktivované proteinkinasy metabolismus   MeSH
• oocyty metabolismus   MeSH
• polyadenylace MeSH
• proteosyntéza * MeSH
• signální transdukce MeSH
• TOR serin-threoninkinasy metabolismus   MeSH
• vazba proteinů MeSH
• vývojová regulace genové exprese MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

BACKGROUND: Eukaryotic translation initiation factor 4E (eIF4E) plays a pivotal role in the control of cap-dependent translation initiation, modulates the fate of specific mRNAs, occurs in processing bodies (PBs) and is required for formation of stress granules (SGs). In this study, we focused on the subcellular localization of a representative compendium of eIF4E protein isoforms, particularly on the less studied members of the human eIF4E protein family, eIF4E2 and eIF4E3. RESULTS: We showed that unlike eIF4E1, its less studied isoform eIF4E3_A, encoded by human chromosome 3, localized to stress granules but not PBs upon both heat shock and arsenite stress. Furthermore, we found that eIF4E3_A interacts with human translation initiation factors eIF4G1, eIF4G3 and PABP1 in vivo and sediments into the same fractions as canonical eIF4E1 during polysome analysis in sucrose gradients. Contrary to this finding, the truncated human eIF4E3 isoform, eIF4E3_B, showed no localization to SGs and no binding to eIF4G. We also highlighted that eIF4E2 may exhibit distinct functions under different stresses as it readily localizes to P-bodies during arsenite and heat stresses, whereas it is redirected to stress granules only upon heat shock. We extended our study to a number of protein variants, arising from alternative mRNA splicing, of each of the three eIF4E isoforms. Our results surprisingly uncovered differences in the ability of eIF4E1_1 and eIF4E1_3 to form stress granules in response to cellular stresses. CONCLUSION: Our comparison of all three human eIF4E isoforms and their protein variants enriches the intriguing spectrum of roles attributed to the eukaryotic initiation translation factors of the 4E family, which exhibit a distinctive localization within different RNA granules under different stresses. The localization of eIF4E3_A to stress granules, but not to processing bodies, along with its binding to eIF4G and PABP1 suggests a role of human eIF4E3_A in translation initiation rather than its involvement in a translational repression and mRNA decay and turnover. The localization of eIF4E2 to stress granules under heat shock but not arsenite stress indicates its distinct function in cellular response to these stresses and points to the variable protein content of SGs as a consequence of different stress insults.

• MeSH
• buněčné linie MeSH
• cytosol metabolismus   MeSH
• eukaryotický iniciační faktor 4E analýza   genetika   metabolismus   MeSH
• HEK293 buňky MeSH
• klonování DNA MeSH
• lidé MeSH
• messenger RNA genetika   MeSH
• oxidační stres * MeSH
• poly(A)-vazebný protein I analýza   metabolismus   MeSH
• proteiny vázající čepičku mRNA analýza   genetika   metabolismus   MeSH
• reakce na tepelný šok * MeSH
• sekvence aminokyselin MeSH
• sekvenční seřazení MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Protein synthesis is a highly efficient process and is under exacting control. Yet, the actual abundance of translation factors present in translating complexes and how these abundances change during the transit of a ribosome across an mRNA remains unknown. Using analytical ultracentrifugation with fluorescent detection we have determined the stoichiometry of the closed-loop translation factors for translating ribosomes. A variety of pools of translating polysomes and monosomes were identified, each containing different abundances of the closed-loop factors eIF4E, eIF4G, and PAB1 and that of the translational repressor, SBP1. We establish that closed-loop factors eIF4E/eIF4G dissociated both as ribosomes transited polyadenylated mRNA from initiation to elongation and as translation changed from the polysomal to monosomal state prior to cessation of translation. eIF4G was found to particularly dissociate from polyadenylated mRNA as polysomes moved to the monosomal state, suggesting an active role for translational repressors in this process. Consistent with this suggestion, translating complexes generally did not simultaneously contain eIF4E/eIF4G and SBP1, implying mutual exclusivity in such complexes. For substantially deadenylated mRNA, however, a second type of closed-loop structure was identified that contained just eIF4E and eIF4G. More than one eIF4G molecule per polysome appeared to be present in these complexes, supporting the importance of eIF4G interactions with the mRNA independent of PAB1. These latter closed-loop structures, which were particularly stable in polysomes, may be playing specific roles in both normal and disease states for specific mRNA that are deadenylated and/or lacking PAB1. These analyses establish a dynamic snapshot of molecular abundance changes during ribosomal transit across an mRNA in what are likely to be critical targets of regulation.

• MeSH
• elongace translace peptidového řetězce * MeSH
• eukaryotický iniciační faktor 4E metabolismus   MeSH
• eukaryotický iniciační faktor 4G metabolismus   MeSH
• iniciace translace peptidového řetězce * MeSH
• messenger RNA genetika   metabolismus   MeSH
• multiproteinové komplexy metabolismus   MeSH
• poly A MeSH
• polyribozomy metabolismus   MeSH
• proteiny vázající selen metabolismus   MeSH
• proteosyntéza MeSH
• ribozomy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

The main aims of the project are —using both human cell lines and clinical samples— to dissect and unravel a role of proteins belonging to the translation initiation factor 4E family in initiation and relapse of the acute lymphoblastic leukemia (ALL) and to evaluate them as predictive markers and potential targets for therapy. We expect that obtained results will positively influence both diagnostics of ALL as well as preclinical and clinical research aimed to new molecular targets evaluation and new therapies development.

Hlavním cílem projektu je s využitím buněčných linií i klinických vzorků zkoumat a objasnit roli proteinů z rodiny translačního iniciačního faktoru eIF4E při vzniku a relapsu akutní lymfoblastické leukémie a zhodnotit vhodnost těchto proteinů jako potenciálních prediktivních ukazatelů a případných cílů pro léčbu. Předpokládáme, že získané výsledky a vyvinuté metodiky ovlivní jednak diagnostiku ALL, jednak preklinický a klinický výzkum zacílený na hledání nových molekulárních cílů a vývoj nových terapeutických strategií u ALL.

• MeSH
• akutní lymfatická leukemie diagnóza   terapie   MeSH
• bcr-abl fúzové proteiny MeSH
• diagnostické techniky molekulární MeSH
• eukaryotický iniciační faktor 4E analýza   MeSH
• homeoboxové geny MeSH
• messenger RNA MeSH
• nádorové biomarkery analýza   MeSH
• prediktivní hodnota testů MeSH
• ribavirin MeSH
• sirolimus analogy a deriváty   MeSH
• TOR serin-threoninkinasy antagonisté a inhibitory   MeSH
• transformace genetická MeSH

• Konspekt
• Biochemie. Molekulární biologie. Biofyzika
• NLK Obory
• molekulární biologie, molekulární medicína
• hematologie a transfuzní lékařství
• onkologie
• NLK Publikační typ
• závěrečné zprávy o řešení grantu IGA MZ ČR

The fully grown mammalian oocyte is transcriptionally quiescent and utilizes only transcripts synthesized and stored during early development. However, we find that an abundant RNA population is retained in the oocyte nucleus and contains specific mRNAs important for meiotic progression. Here we show that during the first meiotic division, shortly after nuclear envelope breakdown, translational hotspots develop in the chromosomal area and in a region that was previously surrounded the nucleus. These distinct translational hotspots are separated by endoplasmic reticulum and Lamin, and disappear following polar body extrusion. Chromosomal translational hotspots are controlled by the activity of the mTOR-eIF4F pathway. Here we reveal a mechanism that-following the resumption of meiosis-controls the temporal and spatial translation of a specific set of transcripts required for normal spindle assembly, chromosome alignment and segregation.

• MeSH
• časové faktory MeSH
• down regulace MeSH
• eukaryotický iniciační faktor 4F metabolismus   MeSH
• fertilizace MeSH
• jaderný obal metabolismus   MeSH
• lidé MeSH
• meióza MeSH
• messenger RNA genetika   metabolismus   MeSH
• myši MeSH
• nestabilita genomu MeSH
• oocyty metabolismus   MeSH
• proteosyntéza * MeSH
• RNA čepičky metabolismus   MeSH
• savčí chromozomy metabolismus   MeSH
• savci metabolismus   MeSH
• signální transdukce * MeSH
• TOR serin-threoninkinasy metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The eukaryotic translation initiation factor 4E was shown to be involved in resistance against several potyviruses in plants, including pea. We combined our knowledge of pea germplasm diversity with that of the eIF4E gene to identify novel genetic diversity. METHODOLOGY/PRINCIPAL FINDINGS: Germplasm of 2803 pea accessions was screened for eIF4E intron 3 length polymorphism, resulting in the detection of four eIF4E(A-B-C-S) variants, whose distribution was geographically structured. The eIF4E(A) variant conferring resistance to the P1 PSbMV pathotype was found in 53 accessions (1.9%), of which 15 were landraces from India, Afghanistan, Nepal, and 7 were from Ethiopia. A newly discovered variant, eIF4E(B), was present in 328 accessions (11.7%) from Ethiopia (29%), Afghanistan (23%), India (20%), Israel (25%) and China (39%). The eIF4E(C) variant was detected in 91 accessions (3.2% of total) from India (20%), Afghanistan (33%), the Iberian Peninsula (22%) and the Balkans (9.3%). The eIF4E(S) variant for susceptibility predominated as the wild type. Sequencing of 73 samples, identified 34 alleles at the whole gene, 26 at cDNA and 19 protein variants, respectively. Fifteen alleles were virologically tested and 9 alleles (eIF4E(A-1-2-3-4-5-6-7), eIF4E(B-1), eIF4E(C-2)) conferred resistance to the P1 PSbMV pathotype. CONCLUSIONS/SIGNIFICANCE: This work identified novel eIF4E alleles within geographically structured pea germplasm and indicated their independent evolution from the susceptible eIF4E(S1) allele. Despite high variation present in wild Pisum accessions, none of them possessed resistance alleles, supporting a hypothesis of distinct mode of evolution of resistance in wild as opposed to crop species. The Highlands of Central Asia, the northern regions of the Indian subcontinent, Eastern Africa and China were identified as important centers of pea diversity that correspond with the diversity of the pathogen. The series of alleles identified in this study provides the basis to study the co-evolution of potyviruses and the pea host.

• MeSH
• alely MeSH
• eukaryotický iniciační faktor 4E genetika   fyziologie   MeSH
• hrách setý genetika   metabolismus   virologie   MeSH
• nemoci rostlin virologie   MeSH
• Potyvirus patogenita   MeSH
• rostlinné proteiny genetika   fyziologie   MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

The eukaryotic translation initiation factor 4E is an essential and highly conserved protein. As a part of the translational machinery, it plays a key role in the recruitment of mRNA via binding to its m(7)GpppN 5' terminal cap structure. The opportunistic human pathogen Candida albicans is the only known eukaryotic organism with the ability to survive defects in mRNA capping, which suggests unique features of its eIF4E protein. Here, we provide the first experimental evidence of the function of the C. albicans putative gene orf19.7626 as an eIF4E protein. We also show that Ca4E(Leu116) and Ca4E(Ser116) protein variants, both of which occur naturally in C. albicans due to the ambiguous decoding of the CUG(116) codon, display different sensitivities to elevated temperature. Our results clearly point to the importance of the S4-H4 loop for the function of the Ca4E translation initiation factor, and suggest the possible regulatory role of the codon-reading ambiguity within this loop in C. albicans. We proved Saccharomyces cerevisiae as a useful tool organism for studies of C. albicans translation initiation apparatus.

• MeSH
• Candida albicans genetika   růst a vývoj   metabolismus   účinky záření   MeSH
• esenciální geny MeSH
• eukaryotický iniciační faktor 4E metabolismus   MeSH
• fungální proteiny metabolismus   MeSH
• geny hub MeSH
• kodon MeSH
• molekulární modely MeSH
• molekulární sekvence - údaje MeSH
• proteosyntéza MeSH
• sekvence aminokyselin MeSH
• sekvenční homologie MeSH
• sekvenční seřazení MeSH
• substituce aminokyselin genetika   MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH