scholarly journals Cup is an eIF4E binding protein required for both the translational repression of oskar and the recruitment of Barentsz

2003 ◽  
Vol 163 (6) ◽  
pp. 1197-1204 ◽  
Author(s):  
James E. Wilhelm ◽  
Meredith Hilton ◽  
Quinlan Amos ◽  
William J. Henzel
Keyword(s):  
Translational Control ◽  
Mrna Localization ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Translational Repressor ◽  
Eukaryotic Initiation Factor 4E ◽  
Microtubule Transport ◽  
Rnp Complex ◽  
Made In

In Drosophila oocytes, precise localization of the posterior determinant, Oskar, is required for posterior patterning. This precision is accomplished by a localization-dependent translational control mechanism that ensures translation of only correctly localized oskar transcripts. Although progress has been made in identifying localization factors and translational repressors of oskar, none of the known components of the oskar complex is required for both processes. Here, we report the identification of Cup as a novel component of the oskar RNP complex. cup is required for oskar mRNA localization and is necessary to recruit the plus end–directed microtubule transport factor Barentsz to the complex. Surprisingly, Cup is also required to repress the translation of oskar. Furthermore, eukaryotic initiation factor 4E (eIF4E) is localized within the oocyte in a cup-dependent manner and binds directly to Cup in vitro. Thus, Cup is a translational repressor of oskar that is required to assemble the oskar mRNA localization machinery. We propose that Cup coordinates localization with translation.

scholarly journals Multiple Mechanisms Control Phosphorylation of PHAS-I in Five (S/T)P Sites That Govern Translational Repression

2000 ◽  
Vol 20 (10) ◽  
pp. 3558-3567 ◽  
Author(s):  
Isabelle Mothe-Satney ◽  
Daqing Yang ◽  
Patrick Fadden ◽  
Timothy A. J. Haystead ◽  
John C. Lawrence
Keyword(s):  
Mrna Translation ◽  
Hek293 Cells ◽  
Initiation Factor ◽  
Translational Repression ◽  
Phosphorylation Sites ◽  
Translational Repressor ◽  
Eukaryotic Initiation Factor 4E ◽  
Dependent Processes ◽  
Constitutive Phosphorylation

ABSTRACT Control of the translational repressor, PHAS-I, was investigated by expressing proteins with Ser/Thr → Ala mutations in the five (S/T)P phosphorylation sites. Results of experiments with HEK293 cells reveal at least three levels of control. At one extreme is nonregulated phosphorylation, exemplified by constitutive phosphorylation of Ser82. At an intermediate level, amino acids and insulin stimulate the phosphorylation of Thr36, Thr45, and Thr69 via mTOR-dependent processes that function independently of other sites in PHAS-I. At the third level, the extent of phosphorylation of one site modulates the phosphorylation of another. This control is represented by Ser64 phosphorylation, which depends on the phosphorylation of all three TP sites. The five sites have different influences on the electrophoretic properties of PHAS-I and on the affinity of PHAS-I for eukaryotic initiation factor 4E (eIF4E). Phosphorylation of Thr45 or Ser64 results in the most dramatic decreases in eIF4E binding in vitro. However, each of the sites influences mRNA translation, either directly by modulating the binding affinity of PHAS-I and eIF4E or indirectly by affecting the phosphorylation of other sites.

4E-BP1 and S6K1: translational integration sites for nutritional and hormonal information in muscle

2000 ◽  
Vol 279 (4) ◽  
pp. E715-E729 ◽  
Author(s):  
O. Jameel Shah ◽  
Joshua C. Anthony ◽  
Scot R. Kimball ◽  
Leonard S. Jefferson
Keyword(s):  
Translational Control ◽  
Mrna Translation ◽  
Cellular Protein ◽  
Initiation Factor ◽  
Translational Repressor ◽  
Initiation Factors ◽  
Initiation Phase ◽  
Eukaryotic Initiation Factor 4E ◽  
Integration Sites ◽  
A Site

Maintenance of cellular protein stores in skeletal muscle depends on a tightly regulated synthesis-degradation equilibrium that is conditionally modulated under an extensive range of physiological and pathophysiological circumstances. Recent studies have established the initiation phase of mRNA translation as a pivotal site of regulation for global rates of protein synthesis, as well as a site through which the synthesis of specific proteins is controlled. The protein synthetic pathway is exquisitely sensitive to the availability of hormones and nutrients and employs a comprehensive integrative strategy to interpret the information provided by hormonal and nutritional cues. The translational repressor, eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and the 70-kDa ribosomal protein S6 kinase (S6K1) have emerged as important components of this strategy, and together they coordinate the behavior of both eukaryotic initiation factors and the ribosome. This review discusses the role of 4E-BP1 and S6K1 in translational control and outlines the mechanisms through which hormones and nutrients effect changes in mRNA translation through the influence of these translational effectors.

scholarly journals Translational Control of Cell Fate: Availability of Phosphorylation Sites on Translational Repressor 4E-BP1 Governs Its Proapoptotic Potency

2002 ◽  
Vol 22 (8) ◽  
pp. 2853-2861 ◽  
Author(s):  
Shunan Li ◽  
Nahum Sonenberg ◽  
Anne-Claude Gingras ◽  
Mark Peterson ◽  
Svetlana Avdulov ◽  
...  
Keyword(s):  
Cell Fate ◽  
Translational Control ◽  
Phosphorylation Site ◽  
Ectopic Expression ◽  
Initiation Factor ◽  
Wild Type ◽  
Internal Ribosomal Entry Sites ◽  
Translational Repressor ◽  
Eukaryotic Initiation Factor 4E ◽  
Quantitative Changes

ABSTRACT Translational control has been recently added to well-recognized genomic, transcriptional, and posttranslational mechanisms regulating apoptosis. We previously found that overexpressed eukaryotic initiation factor 4E (eIF4E) rescues cells from apoptosis, while ectopic expression of wild-type eIF4E-binding protein 1 (4E-BP1), the most abundant member of the 4E-BP family of eIF4E repressor proteins, activates apoptosis—but only in transformed cells. To test the possibility that nontransformed cells require less cap-dependent translation to suppress apoptosis than do their transformed counterparts, we intensified the level of translational repression in nontransformed fibroblasts. Here, we show that inhibition of 4E-BP1 phosphorylation by rapamycin triggers apoptosis in cells ectopically expressing wild-type 4E-BP1 and that expression of 4E-BP1 phosphorylation site mutants potently activates apoptosis in a phosphorylation site-specific manner. In general, proapoptotic potency paralleled repression of cap-dependent translation. However, this relationship was not a simple monotone. As repression of cap-dependent translation intensified, apoptosis increased to a maximum value. Further repression resulted in less apoptosis—a state associated with activation of translation through internal ribosomal entry sites. These findings show: that phosphorylation events govern the proapoptotic potency of 4E-BP1, that 4E-BP1 is proapoptotic in normal as well as transformed fibroblasts, and that malignant transformation is associated with a higher requirement for cap-dependent translation to inhibit apoptosis. Our results suggest that 4E-BP1-mediated control of apoptosis occurs through qualitative rather than quantitative changes in protein synthesis, mediated by a dynamic interplay between cap-dependent and cap-independent processes.

scholarly journals Translational Control by Neuroguidin, a Eukaryotic Initiation Factor 4E and CPEB Binding Protein

2006 ◽  
Vol 26 (11) ◽  
pp. 4277-4287 ◽  
Author(s):  
Mi-Young Jung ◽  
Lori Lorenz ◽  
Joel D. Richter
Keyword(s):  
Neural Crest ◽  
Neural Tube ◽  
Neural Development ◽  
Translational Control ◽  
Binding Protein ◽  
Neural Tube Closure ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Eukaryotic Initiation Factor ◽  
Eukaryotic Initiation Factor 4E

ABSTRACT CPEB-mediated translation is important in early development and neuronal synaptic plasticity. Here, we describe a new eukaryotic initiation factor 4E (eIF4E) binding protein, Neuroguidin (Ngd), and its interaction with CPEB. In the mammalian nervous system, Ngd is detected as puncta in axons and dendrites and in growth cones and filopodia. Ngd contains three motifs that resemble those present in eIF4G, 4EBP, Cup, and Maskin, all of which are eIF4E binding proteins. Ngd binds eIF4E directly, and all three motifs must be deleted to abrogate the interaction between these two proteins. In injected Xenopus oocytes, Ngd binds CPEB and, most importantly, represses translation in a cytoplasmic polyadenylation element (CPE)-dependent manner. In Xenopus embryos, Ngd is found in both neural tube and neural crest cells. The injection of morpholino-containing antisense oligonucleotides directed against ngd mRNA disrupts neural tube closure and neural crest migration; however, the wild-type phenotype is restored by the injection of a rescuing ngd mRNA. These data suggest that Ngd guides neural development by regulating the translation of CPE-containing mRNAs.

scholarly journals Phosphorylation of eukaryotic initiation factor 4E (eIF4E) at Ser209 is not required for protein synthesis in vitro and in vivo

2001 ◽  
Vol 268 (20) ◽  
pp. 5375-5385 ◽  
Author(s):  
Linda McKendrick ◽  
Simon J. Morley ◽  
Virginia M. Pain ◽  
Rosemary Jagus ◽  
Bhavesh Joshi
Keyword(s):  
Protein Synthesis ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Eukaryotic Initiation Factor 4E

scholarly journals The viral nucleocapsid protein and the human RNA-binding protein Mex3A promote translation of the Andes orthohantavirus small mRNA

2021 ◽  
Vol 17 (9) ◽  
pp. e1009931
Author(s):  
Jorge Vera-Otarola ◽  
Estefania Castillo-Vargas ◽  
Jenniffer Angulo ◽  
Francisco M. Barriga ◽  
Eduard Batlle ◽  
...  
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Initiation Factor ◽  
Cellular Proteins ◽  
Dependent Manner ◽  
The Andes ◽  
Viral Nucleocapsid

The capped Small segment mRNA (SmRNA) of the Andes orthohantavirus (ANDV) lacks a poly(A) tail. In this study, we characterize the mechanism driving ANDV-SmRNA translation. Results show that the ANDV-nucleocapsid protein (ANDV-N) promotes in vitro translation from capped mRNAs without replacing eukaryotic initiation factor (eIF) 4G. Using an RNA affinity chromatography approach followed by mass spectrometry, we identify the human RNA chaperone Mex3A (hMex3A) as a SmRNA-3’UTR binding protein. Results show that hMex3A enhances SmRNA translation in a 3’UTR dependent manner, either alone or when co-expressed with the ANDV-N. The ANDV-N and hMex3A proteins do not interact in cells, but both proteins interact with eIF4G. The hMex3A–eIF4G interaction showed to be independent of ANDV-infection or ANDV-N expression. Together, our observations suggest that translation of the ANDV SmRNA is enhanced by a 5’-3’ end interaction, mediated by both viral and cellular proteins.

Molecular cloning of a centrin homolog from Marsilea vestita and evidence for its translational control during spermiogenesis

1999 ◽  
Vol 77 (2) ◽  
pp. 101-108 ◽  
Author(s):  
Peter E Hart ◽  
Stephen M Wolniak
Keyword(s):  
Translational Control ◽  
De Novo ◽  
Basal Bodies ◽  
Motile Cells ◽  
Marsilea Vestita ◽  
Stored Mrna ◽  
Eukaryotic Organisms ◽  
Alpha Amanitin ◽  
Made In

Spermiogenesis in the water fern Marsilea vestita is a process that reaches completion 11 h after dry microspores are immersed in an aqueous medium at 20°C. Each microspore produces 32 spermatozoids and each spermatozoid has a coiled cell body and approximately 140 cilia. The spermatids make basal bodies de novo, from a structure known as a blepharoplast. From the onset of development, the spores contain a large quantity of protein and stored mRNA. We have found previously that centrin, a protein involved in the function of microtubule organizing centers and present in association with basal bodies in motile cells, is made in large quantity approximately 4 h after the microspores are placed into liquid medium. In this paper, we show that a centrin cDNA (MvCen1) we isolated from M. vestita closely resembles centrin cDNAs from other eukaryotic organisms. MvCen1, synthesized in Escherichia coli as a GST-fusion protein, reacted with anti-centrin monoclonal antibodies on immunoblots. Northern blot analysis demonstrates that centrin mRNA is present in the dry microspore at the time of imbibition, at levels that remain constant over 10 h of development and are unaffected by treatment of spores with alpha-amanitin. The centrin transcripts, stored in dry microspores, cannot be translated in vitro for at least 30 min after imbibition.Key words: Marsilea vestita, spermatozoid, spermiogenesis, centrin, MTOC.

scholarly journals Dengue Virus Utilizes a Novel Strategy for Translation Initiation When Cap-Dependent Translation Is Inhibited

2006 ◽  
Vol 80 (6) ◽  
pp. 2976-2986 ◽  
Author(s):  
Dianna Edgil ◽  
Charlotta Polacek ◽  
Eva Harris
Keyword(s):  
Dengue Virus ◽  
Translation Initiation ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Eukaryotic Initiation Factor 4E ◽  
Cellular Translation ◽  
Cellular Mrnas ◽  
Novel Strategy

ABSTRACT Viruses have developed numerous mechanisms to usurp the host cell translation apparatus. Dengue virus (DEN) and other flaviviruses, such as West Nile and yellow fever viruses, contain a 5′ m7GpppN-capped positive-sense RNA genome with a nonpolyadenylated 3′ untranslated region (UTR) that has been presumed to undergo translation in a cap-dependent manner. However, the means by which the DEN genome is translated effectively in the presence of capped, polyadenylated cellular mRNAs is unknown. This report demonstrates that DEN replication and translation are not affected under conditions that inhibit cap-dependent translation by targeting the cap-binding protein eukaryotic initiation factor 4E, a key regulator of cellular translation. We further show that under cellular conditions in which translation factors are limiting, DEN can alternate between canonical cap-dependent translation initiation and a noncanonical mechanism that appears not to require a functional m7G cap. This DEN noncanonical translation is not mediated by an internal ribosome entry site but requires the interaction of the DEN 5′ and 3′ UTRs for activity, suggesting a novel strategy for translation of animal viruses.

Translational control in early development: CPEB, P-bodies and germinal granules

2008 ◽  
Vol 36 (4) ◽  
pp. 671-676 ◽  
Author(s):  
Nancy Standart ◽  
Nicola Minshall
Keyword(s):  
Early Development ◽  
Translational Control ◽  
Binding Proteins ◽  
Rna Binding ◽  
Binding Protein ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Cytoplasmic Polyadenylation ◽  
P Bodies ◽  
Germinal Granules

Selective protein synthesis in oocytes, eggs and early embryos of many organisms drives several critical aspects of early development, including meiotic maturation and entry into mitosis, establishment of embryonic axes and cell fate determination. mRNA-binding proteins which (usually) recognize 3′-UTR (untranslated region) elements in target mRNAs influence the recruitment of the small ribosomal subunit to the 5′ cap. Probably the best studied such protein is CPEB (cytoplasmic polyadenylation element-binding protein), which represses translation in the oocyte in a cap-dependent manner, and activates translation in the meiotically maturing egg, via cytoplasmic polyadenylation. Co-immunoprecipitation and gel-filtration assays revealed that CPEB in Xenopus oocytes is in a very large RNP (ribonucleoprotein) complex and interacts with other RNA-binding proteins including Xp54 RNA helicase, Pat1, RAP55 (RNA-associated protein 55) and FRGY2 (frog germ cell-specific Y-box protein 2), as well as the eIF4E (eukaryotic initiation factor 4E)-binding protein 4E-T (eIF4E-transporter) and an ovary-specific eIF4E1b, which binds the cap weakly. Functional tests which implicate 4E-T and eIF4E1b in translational repression in oocytes led us to propose a model for the specific inhibition of translation of a target mRNA by a weak cap-binding protein. The components of the CPEB RNP complex are common to P-bodies (processing bodies), neuronal granules and germinal granules, suggesting that a highly conserved ‘masking’ complex operates in early development, neurons and somatic cells.

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