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

1996 ◽  
Vol 16 (10) ◽  
pp. 5450-5457 ◽  
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.

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.

scholarly journals An essential E box in the promoter of the gene encoding the mRNA cap-binding protein (eukaryotic initiation factor 4E) is a target for activation by c-myc.

1996 ◽  
Vol 16 (9) ◽  
pp. 4754-4764 ◽  
Author(s):  
R M Jones ◽  
J Branda ◽  
K A Johnston ◽  
M Polymenis ◽  
M Gadd ◽  
...  
Keyword(s):  
Electrophoretic Mobility ◽  
Promoter Region ◽  
Binding Protein ◽  
Dominant Negative ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Mobility Shift ◽  
Gene Encoding ◽  
Eukaryotic Initiation Factor 4E ◽  
E Box

The mRNA cap-binding protein (eukaryotic initiation factor 4E [eIF4E]) binds the m7 GpppN cap on mRNA, thereby initiating translation. eIF4E is essential and rate limiting for protein synthesis. Overexpression of eIF4E transforms cells, and mutations in eIF4E arrest cells in G, in cdc33 mutants. In this work, we identified the promoter region of the gene encoding eIF4E, because we previously identified eIF4E as a potential myc-regulated gene. In support of our previous data, a minimal, functional, 403-nucleotide promoter region of eIF4E was found to contain CACGTG E box repeats, and this core eIF4E promoter was myc responsive in cotransfections with c-myc. A direct role for myc in activating the eIF4E promoter was demonstrated by cotransfections with two dominant negative mutants of c-myc (MycdeltaTAD and MycdeltaBR) which equally suppressed promoter function. Furthermore, electrophoretic mobility shift assays demonstrated quantitative binding to the E box motifs that correlated with myc levels in the electrophoretic mobility shift assay extracts; supershift assays demonstrated max and USF binding to the same motif. cis mutations in the core or flank of the eIF4E E box simultaneously altered myc-max and USF binding and inactivated the promoter. Indeed, mutations of this E box inactivated the promoter in all cells tested, suggesting it is essential for expression of eIF4E. Furthermore, the GGCCACGTG(A/T)C(C/G) sequence is shared with other in vivo targets for c-myc, but unlike other targets, it is located in the immediate promoter region. Its critical function in the eIF4E promoter coupled with the known functional significance of eIF4E in growth regulation makes it a particularly interesting target for c-myc regulation.

scholarly journals Cell type-specific control of protein synthesis and proliferation by FGF-dependent signaling to the translation repressor 4E-BP

2016 ◽  
Vol 113 (27) ◽  
pp. 7545-7550 ◽  
Author(s):  
Rachel Ruoff ◽  
Olga Katsara ◽  
Victoria Kolupaeva
Keyword(s):  
Protein Synthesis ◽  
Translational Control ◽  
Bone Development ◽  
Binding Protein ◽  
Initiation Factor ◽  
Start Codon ◽  
Dependent Manner ◽  
Fgf Signaling ◽  
Cell Type

Regulation of protein synthesis plays a vital role in posttranscriptional modulation of gene expression. Translational control most commonly targets the initiation of protein synthesis: loading 40S ribosome complexes onto mRNA and AUG start codon recognition. This step is initiated by eukaryotic initiation factor 4E (eIF4E) (the m7GTP cap-binding protein), whose binding to eIF4G (a scaffolding subunit) and eIF4A (an ATP-dependent RNA helicase) leads to assembly of active eIF4F complex. The ability of eIF4E to recognize the cap is prevented by its binding to eIF4E binding protein (4E-BP), which thereby inhibits cap-dependent translation by sequestering eIF4E. The 4E-BP activity is, in turn, inhibited by mTORC1 [mTOR (the mechanistic target of rapamycin) complex 1] mediated phosphorylation. Here, we define a previously unidentified mechanism of mTOR-independent 4E-BP1 regulation that is used by chondrocytes upon FGF signaling. Chondrocytes are responsible for the formation of the skeleton long bones. Unlike the majority of cell types where FGF signaling triggers proliferation, chondrocytes respond to FGF with inhibition. We establish that FGF specifically suppresses protein synthesis in chondrocytes, but not in any other cells of mesenchymal origin. Furthermore, 4E-BP1 repressor activity is necessary not only for suppression of protein synthesis, but also for FGF-induced cell-cycle arrest. Importantly, FGF-induced changes in the 4E-BP1 activity observed in cell culture are likewise detected in vivo and reflect the action of FGF signaling on downstream targets during bone development. Thus, our findings demonstrate that FGF signaling differentially impacts protein synthesis through either stimulation or repression, in a cell-type–dependent manner, with 4E-BP1 being a key player.

scholarly journals Acute Regulation of Translation Initiation by Gonadotropin-Releasing Hormone in the Gonadotrope Cell Line LβT2

2004 ◽  
Vol 18 (5) ◽  
pp. 1301-1312 ◽  
Author(s):  
Kathryn A. Nguyen ◽  
Sharon J. Santos ◽  
Marit K. Kreidel ◽  
Alejandro L. Diaz ◽  
Rodolfo Rey ◽  
...  
Keyword(s):  
Cell Line ◽  
Translation Initiation ◽  
Translational Control ◽  
Promoter Activity ◽  
Gnrh Receptor ◽  
Initiation Factor ◽  
Dependent Manner ◽  
Eukaryotic Initiation Factor ◽  
Western Blots ◽  
Stimulation Of

Abstract The hypothalamic neuropeptide hormone GnRH is the central regulator of reproductive function. GnRH stimulates the synthesis and release of the gonadotropins LH and FSH by the gonadotropes of the anterior pituitary through activation of the G-protein-coupled GnRH receptor. In this study, we investigated the role of translational control of hormone synthesis by the GnRH receptor in the novel gonadotrope cell line LβT2. Using immunohistochemical and RIA studies with this model, we show that acute GnRH-induced synthesis and secretion of LH are dependent upon new protein synthesis but not new mRNA synthesis. We examined the response to GnRH and found that activation of cap-dependent translation occurs within 4 h. LHβ promoter activity was also examined, and we found no increases in LHβ promoter activity after 6 h of GnRH stimulation. Additionally, we show that increased phosphorylation of translation initiation proteins, 4E-binding protein 1, eukaryotic initiation factor 4E, and eukaryotic initiation factor 4G, occur in a dose- and time-dependent manner in response to GnRH stimulation. Quantitative luminescent image analysis of Western blots shows that 10 nm GnRH is sufficient to cause a maximal increase in factor phosphorylation, and maximal responses occur within 30 min of stimulation. Further, we demonstrate that the MAPK kinase inhibitor, PD 98059, abolishes the GnRH-mediated stimulation of a cap-dependent translation reporter. More specifically, we demonstrate that PD 98059 abolishes the GnRH-mediated stimulation of a downstream target of the ERK pathway, MAPK-interacting kinase. Based on these findings, we conclude that acute GnRH stimulation of LβT2 cells increases translation initiation through ERK signaling. This may contribute to the acute increases in LHβ subunit production.

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