scholarly journals The eukaryotic Initiation Factor 6 (eIF6) regulates ecdysone biosynthesis by modulating translation in Drosophila

2017 ◽  
Author(s):  
Arianna Russo ◽  
Guido Gatti ◽  
Roberta Alfieri ◽  
Elisa Pesce ◽  
Kelly Soanes ◽  
...  
Keyword(s):  
Ribosome Biogenesis ◽  
Biosynthetic Pathway ◽  
Single Gene ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Developmental Models ◽  
Translation Factors ◽  
General Translation

ABSTRACTDuring development, ribosome biogenesis and translation reach peak activities, due to impetuous cell proliferation. Current models predict that protein synthesis elevation is controlled by transcription factors and signalling pathways. Developmental models addressing translation factors overexpression effects are lacking. Eukaryotic Initiation Factor (eIF6) is necessary for ribosome biogenesis and efficient translation. eIF6 is a single gene, conserved from yeasts to mammals, suggesting a tight regulation need. We generated a Drosophila melanogaster in vivo model of eIF6 upregulation, demonstrating a boost in general translation and the shut off of the ecdysone biosynthetic pathway. Translation modulation in S2 cells showed that translational rate and ecdysone biosynthesis are inversely correlated. In vivo, eIF6-driven alterations delayed programmed cell death (PCD), resulting in aberrant phenotypes, partially rescued by ecdysone administration. Our data show that eIF6 triggers a translation program with far-reaching effects on metabolism and development, stressing the driving and central role of translation.

Association and Phosphorylation of Deoxyhypusine Synthase with CK2

2005 ◽  
Vol 277-279 ◽  
pp. 102-106
Author(s):  
Kee Ryeon Kang
Keyword(s):  
Protein Kinase Ck2 ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Deoxyhypusine Synthase ◽  
Cellular Event ◽  
Phosphoamino Acid Analysis ◽  
Kinase Ck2

Deoxyhypusine synthase (DHS) catalyzes the first step in the posttranslational synthesis of hypusine in the eukaryotic initiation factor 5A (eIF5A) precursor protein. As such, the phosphorylation of DHS by the protein kinase CK2 was investigated to define the role of DHS in the regulation of eIF5A in cells. The results showed that DHS was phosphorylated by CK2 in vivo as well as in vitro. The endogenous CK2 in HeLa cells and cell lysates was able to phosphorylate DHS and this modification was enhanced or decreased by the addition of CK2 effectors, such as polylysine, heparin, or poly (Glu, Tyr). A phosphoamino acid analysis of the enzyme revealed that the DHS was mainly phosphorylated into the Thr residue, with the remainder into the Ser residue. Therefore, it would appear that the phosphorylation of DHS was a CK2-dependent cellular event, thereby opening the path for possible regulation of the interaction with the eIF5A precursor for hypusine synthesis.

Cytoskeletal proteins associate with components of the ribosomal maturation and translation apparatus in Xenopus stage I oocytes

Zygote ◽  
2014 ◽  
Vol 23 (5) ◽  
pp. 669-682 ◽  
Author(s):  
Loredana Chierchia ◽  
Margherita Tussellino ◽  
Domenico Guarino ◽  
Rosa Carotenuto ◽  
Nadia DeMarco ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Elongation Factor ◽  
Cytoskeletal Proteins ◽  
Stage I ◽  
Initiation Factor ◽  
Perinuclear Region ◽  
Eukaryotic Initiation Factor ◽  
Translation Apparatus ◽  
Ribosomal Stalk

SummaryActin-based cytoskeleton (CSK) and microtubules may bind to RNAs and related molecules implicated in translation. However, many questions remain to be answered regarding the role of cytoskeletal components in supporting the proteins involved in steps in the maturation and translation processes. Here, we performed co-immunoprecipitation and immunofluorescence to examine the association between spectrins, keratins and tubulin and proteins involved in 60S ribosomal maturation and translation in Xenopus stage I oocytes, including ribosomal rpl10, eukaryotic initiation factor 6 (Eif6), thesaurins A/B, homologs of the eEF1α elongation factor, and P0, the ribosomal stalk protein. We found that rpl10 and eif6 cross-reacted with the actin-based CSK and with tubulin. rpl10 co-localizes with spectrin, particularly in the perinuclear region. eif6 is similarly localized. Given that upon ribosomal maturation, the insertion of rpl10 into the 60S subunit occurs simultaneously with the release of eif6, one can hypothesise that actin-based CSK and microtubules provide the necessary scaffold for the insertion/release of these two molecules and, subsequently, for eif6 transport and binding to the mature 60S subunit. P0 and thesaurins cross-reacted with only spectrin and cytokeratins. Thesaurins aggregated at the oocyte periphery, rendering this a territory favourable site for protein synthesis; the CSK may support the interaction between thesaurins and sites of the translating ribosome. Moreover, given that the assembly of the ribosome stalk, where P0 is located, to the 60S subunit is essential for the release of eif6, it can be hypothesised that the CSK can facilitate the binding of the stalk to the 60S.

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 Study of Staphylococcus aureusPathogenic Genes by Transfer and Expression in the Less Virulent Organism Streptococcus gordonii

2001 ◽  
Vol 69 (2) ◽  
pp. 657-664 ◽  
Author(s):  
P. Stutzmann Meier ◽  
J. M. Entenza ◽  
P. Vaudaux ◽  
P. Francioli ◽  
M. P. Glauser ◽  
...  
Keyword(s):  
Single Gene ◽  
Individual Factors ◽  
Gene Products ◽  
Streptococcus Gordonii ◽  
Pathogenic Role ◽  
Gain Of Function ◽  
Function Strategy

ABSTRACT Because Staphylococcus aureus strains contain multiple virulence factors, studying their pathogenic role by single-gene inactivation generated equivocal results. To circumvent this problem, we have expressed specific S. aureus genes in the less virulent organism Streptococcus gordonii and tested the recombinants for a gain of function both in vitro and in vivo. Clumping factor A (ClfA) and coagulase were investigated. Both gene products were expressed functionally and with similar kinetics during growth by streptococci and staphylococci. ClfA-positive S. gordoniiwas more adherent to platelet-fibrin clots mimicking cardiac vegetations in vitro and more infective in rats with experimental endocarditis (P < 0.05). Moreover, deletingclfA from clfA-positive streptococcal transformants restored both the low in vitro adherence and the low in vivo infectivity of the parent. Coagulase-positive transformants, on the other hand, were neither more adherent nor more infective than the parent. Furthermore, coagulase did not increase the pathogenicity ofclfA-positive streptococci when both clfA andcoa genes were simultaneously expressed in an artificial minioperon in streptococci. These results definitively attribute a role for ClfA, but not coagulase, in S. aureus endovascular infections. This gain-of-function strategy might help solve the role of individual factors in the complex the S. aureus-host relationship.

Expression of mutant eukaryotic initiation factor 2 alpha subunit (eIF-2 alpha) reduces inhibition of guanine nucleotide exchange activity of eIF-2B mediated by eIF-2 alpha phosphorylation

1994 ◽  
Vol 14 (7) ◽  
pp. 4546-4553
Author(s):  
K V Ramaiah ◽  
M V Davies ◽  
J J Chen ◽  
R J Kaufman
Keyword(s):  
Protein Synthesis ◽  
Initiation Factor ◽  
Guanine Nucleotide ◽  
Eukaryotic Initiation Factor ◽  
Nucleotide Exchange ◽  
Wild Type ◽  
Guanine Nucleotide Exchange ◽  
Initiation Factor 2 ◽  
Exchange Activity

The inhibition of protein synthesis that occurs upon phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2 alpha) at serine 51 correlates with reduced guanine nucleotide exchange activity of eIF-2B in vivo and inhibition of eIF-2B activity in vitro, although it is not known if phosphorylation is the cause of the reduced eIF-2B activity in vivo. To characterize the importance of eIF-2 alpha phosphorylation in the regulation of eIF-2B activity, we studied the overexpression of mutant eIF-2 alpha subunits in which serine 48 or 51 was replaced by an alanine (48A or 51A mutant). Previous studies demonstrated that the 51A mutant was resistant to phosphorylation, whereas the 48A mutant was a substrate for phosphorylation. Additionally, expression of either mutant partially protected Chinese hamster ovary (CHO) cells from the inhibition of protein synthesis in response to heat shock treatment (P. Murtha-Riel, M. V. Davies, J. B. Scherer, S. Y. Choi, J. W. B. Hershey, and R. J. Kaufman, J. Biol. Chem. 268:12946-12951, 1993). In this study, we show that eIF-2B activity was inhibited in parental CHO cell extracts upon addition of purified reticulocyte heme-regulated inhibitor (HRI), an eIF-2 alpha kinase that phosphorylates Ser-51. Preincubation with purified HRI also reduced the eIF-2B activity in extracts from cells overexpressing wild-type eIF-2 alpha. In contrast, the eIF-2B activity was not readily inhibited in extracts from cells overexpressing either the eIF-2 alpha 48A or 51A mutant. In addition, eIF-2B activity was decreased in extracts prepared from heat-shocked cells overexpressing wild-type eIF-2 alpha, whereas the decrease in eIF-2B activity was less in heat-shocked cells overexpressing either mutant 48A or mutant 51A. While the phosphorylation at serine 51 in eIF-2 alpha impairs the eIF-2B activity, we propose that serine 48 acts to maintain a high affinity between phosphorylated eIF-2 alpha and eIF-2B, thereby inactivating eIF-2B activity. These findings support the hypothesis that phosphorylation of eIF-2 alpha inhibits protein synthesis directly through reducing eIF-2B activity and emphasize the importance of both serine 48 and serine 51 in the interaction with eIF-2B and regulation of eIF-2B activity.

scholarly journals Loss of PTEN in Fallopian Tube Epithelium Results in Multicellular Tumor Spheroid Formation and Metastasis to the Ovary

Cancers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 884 ◽  
Author(s):  
Matthew Dean ◽  
Vivian Jin ◽  
Tova M. Bergsten ◽  
Julia R. Austin ◽  
Daniel D. Lantvit ◽  
...  
Keyword(s):  
Fallopian Tube ◽  
Single Gene ◽  
Similar Rate ◽  
Genetic Alterations ◽  
Wild Type ◽  
Spheroid Formation ◽  
Multicellular Tumor Spheroid ◽  
Ovarian Stroma

High-grade serous ovarian cancer (HGSOC) can originate in the fallopian tube and then spread to the ovary. Our objective was to evaluate the role of multicellular tumor spheroids (MTS) in ovarian metastasis. By testing a panel of murine oviductal epithelial (MOE) cells with genetic alterations mimicking those seen in HGSOC, we found that loss of PTEN allowed MTS formation under ultra-low adhesion conditions. Confirming these results in vivo, MTS-like structures were observed in the oviducts of PAX8Cre/+ PTENflox/flox mice. MOE PTENshRNA cells could incorporate up to 25% wild type cells into MTS, while higher percentages of wild type cells resulted in a loss of MTS formation. MTS formation allowed MOE PTENshRNA cells to survive better under ultra-low adhesion conditions than control cells. MTS also attached to the ovarian stroma, as would be exposed during ovulation. Interestingly, MTS more robustly cleared monolayers of murine ovarian surface epithelia than murine ovarian fibroblasts. When xenografted into the ovarian bursa, OVCAR8 MTS were able to form tumors in the ovary at a similar rate as an equal number of OVCAR8 cells grown on traditional cell culture plastic. In conclusion, loss of a single gene (PTEN) allows the fallopian tube epithelia to form MTS, which survive better under ultra-low adhesion conditions, attach to the extracellular matrix exposed during ovulation, and colonize the ovary. These results suggest that MTS may contribute to seeding of the ovary in HGSOC patients.

scholarly journals NADPH Oxidases Are Required for Full Platelet Activation In Vitro and Thrombosis In Vivo but Dispensable for Plasma Coagulation and Hemostasis

2020 ◽  
Author(s):  
Dina Vara ◽  
Reiner K. Mailer ◽  
Anuradha Tarafdar ◽  
Nina Wolska ◽  
Marco Heestermans ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Single Gene ◽  
Coagulation Cascade ◽  
Intracellular Cgmp ◽  
Antithrombotic Effects ◽  
Tail Tip ◽  
Synthase Inhibitor

Objective: Using 3KO (triple NOX [NADPH oxidase] knockout) mice (ie, NOX1 −/− /NOX2 −/− /NOX4 −/− ), we aimed to clarify the role of this family of enzymes in the regulation of platelets in vitro and hemostasis in vivo. Approach and Results: 3KO mice displayed significantly reduced platelet superoxide radical generation, which was associated with impaired platelet aggregation, adhesion, and thrombus formation in response to the key agonists collagen and thrombin. A comparison with single-gene knockouts suggested that the phenotype of 3KO platelets is the combination of the effects of the genetic deletion of NOX1 and NOX2, while NOX4 does not show any significant function in platelet regulation. 3KO platelets displayed significantly higher levels of cGMP—a negative platelet regulator that activates PKG (protein kinase G). The inhibition of PKG substantially but only partially rescued the defective phenotype of 3KO platelets, which are responsive to both collagen and thrombin in the presence of the PKG inhibitors KT5823 or Rp-8-pCPT-cGMPs, but not in the presence of the NOS (NO synthase) inhibitor L-NG-monomethyl arginine. In vivo, triple NOX deficiency protected against ferric chloride–driven carotid artery thrombosis and experimental pulmonary embolism, while hemostasis tested in a tail-tip transection assay was not affected. Procoagulatory activity of platelets (ie, phosphatidylserine surface exposure) and the coagulation cascade in platelet-free plasma were normal. Conclusions: This study indicates that inhibiting NOXs has strong antithrombotic effects partially caused by increased intracellular cGMP but spares hemostasis. NOXs are, therefore, pharmacotherapeutic targets to develop new antithrombotic drugs without bleeding side effects.

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.

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