scholarly journals Poliovirus 2APro Increases Viral mRNA and Polysome Stability Coordinately in Time with Cleavage of eIF4G

2008 ◽  
Vol 82 (12) ◽  
pp. 5847-5859 ◽  
Author(s):  
Brian J. Kempf ◽  
David J. Barton
Keyword(s):  
De Novo ◽  
Mrna Translation ◽  
Viral Mrna ◽  
Site Mutation ◽  
Initiation Factors ◽  
Eukaryotic Initiation Factors ◽  
Messenger Ribonucleoprotein ◽  
Infected Cells ◽  
The Stability ◽  
Polysome Stability

ABSTRACT Poliovirus (PV) 2A protease (2APro) cleaves eukaryotic initiation factors 4GI and 4GII (eIF4GI and eIF4GII) within virus-infected cells, effectively halting cap-dependent mRNA translation. PV mRNA, which does not possess a 5′ cap, is translated via cap-independent mechanisms within viral protease-modified messenger ribonucleoprotein (mRNP) complexes. In this study, we determined that 2APro activity was required for viral polysome formation and stability. 2APro cleaved eIF4GI and eIF4GII as PV polysomes assembled. A 2ACys109Ser (2APro with a Cys109Ser mutation) protease active site mutation that prevented cleavage of eIF4G coordinately inhibited the de novo formation of viral polysomes, the stability of viral polysomes, and the stability of PV mRNA within polysomes. 2ACys109Ser-associated defects in PV mRNA and polysome stability correlated with defects in PV mRNA translation. 3CPro activity was not required for viral polysome formation or stability. 2APro-mediated cleavage of eIF4G along with poly(rC) binding protein binding to the 5′ terminus of uncapped PV mRNA appear to be concerted mechanisms that allow PV mRNA to form mRNP complexes that evade cellular mRNA degradation machinery.

scholarly journals EIF3 p170, a Mediator of Mimosine Effect on Protein Synthesis and Cell Cycle Progression

2003 ◽  
Vol 14 (9) ◽  
pp. 3942-3951 ◽  
Author(s):  
Zizheng Dong ◽  
Jian-Ting Zhang
Keyword(s):  
Cell Cycle ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
De Novo ◽  
Mrna Translation ◽  
Early Response ◽  
Initiation Factors ◽  
Cycle Arrest ◽  
Eukaryotic Initiation Factors ◽  
Complex Process

l-Mimosine, a plant amino acid, can reversibly block mammalian cells at late G1 phase and has been suggested to affect translation of mRNAs such as p27, the CDK inhibitor. However, the mechanism of this effect is not known. Regulation of translation generally occurs at the initiation step that, in mammalian cells, is a complex process that requires multiple eukaryotic initiation factors (eIFs) and ribosome. The effects of mimosine on initiation factors or regulators consequently will influence translation initiation. P170, a putative subunit of eIF3, has been suggested to be nonessential for eIF3 function to form preinitiation complexes and it may function as a regulator for translation of a subset of mRNAs. In this article, we tested this hypothesis and investigated whether eIF3 p170 mediates mimosine effect on mRNA translation. We found that p170 translation was dramatically reduced by mimosine due to its iron-chelating function. The decreased expression of p170 by mimosine caused diminished de novo synthesis of tyrosinated α-tubulin and elevated translation of p27 before cell cycle arrest. These observations suggest that p170 is likely an early response gene to mimosine treatment and a mediator for mimosine effect on mRNA translation. The effect of p170 on the synthesis of tyrosinated α-tubulin and p27 in a reciprocal manner also suggests that p170 functions as a regulator for mRNA translation.

scholarly journals Adenovirus E1B proteins are required for accumulation of late viral mRNA and for effects on cellular mRNA translation and transport.

1985 ◽  
Vol 5 (10) ◽  
pp. 2552-2558 ◽  
Author(s):  
L E Babiss ◽  
H S Ginsberg ◽  
J E Darnell
Keyword(s):  
Mrna Translation ◽  
Mutant Virus ◽  
Viral Mrna ◽  
Mrna Synthesis ◽  
Mrna Transport ◽  
Normal Delivery ◽  
Single Function ◽  
Infected Cells ◽  
Steady State Levels ◽  
Adenovirus E1b

Late in adenovirus infection, large amounts of viral mRNA accumulate while cell mRNA transport and translation decrease. Viruses deleted in the E1B region of type 5 adenovirus do not produce the same outcome: (i) viral mRNA synthesis by the mutants is normal, delivery to the cytoplasm is 50 to 75% of normal, but steady-state levels of viral mRNA are decreased 10-fold; (ii) cell mRNA synthesis and transport continue normally in the mutant virus-infected cell; and (iii) translation of preexisting cell mRNA which is disrupted in wild-type infection remains normal in mutant-virus-infected cells. Thus E1B proteins are required for accumulation of virus mRNA and for induction of the failure of host cell mRNA transport and translation. If a single function is involved, by inference the transport and some aspect of translation of mRNAs could be linked.

scholarly journals Potyvirus Genome-linked Protein, VPg, Directly Affects Wheat Germ in Vitro Translation

2007 ◽  
Vol 283 (3) ◽  
pp. 1340-1349 ◽  
Author(s):  
Mateen A. Khan ◽  
Hiroshi Miyoshi ◽  
Daniel R. Gallie ◽  
Dixie J. Goss
Keyword(s):  
Translation Initiation ◽  
Wheat Germ ◽  
Mrna Translation ◽  
Kinetic Studies ◽  
Dissociation Rate ◽  
In Vitro Translation ◽  
Translation Efficiency ◽  
Viral Mrna ◽  
Initiation Factors

Potyvirus genome linked protein, VPg, interacts with translation initiation factors eIF4E and eIFiso4E, but its role in protein synthesis has not been elucidated. We show that addition of VPg to wheat germ extract leads to enhancement of uncapped viral mRNA translation and inhibition of capped viral mRNA translation. This provides a significant competitive advantage to the uncapped viral mRNA. To understand the molecular basis of these effects, we have characterized the interaction of VPg with eIF4F, eIFiso4F, and a structured RNA derived from tobacco etch virus (TEV RNA). When VPg formed a complex with eIF4F, the affinity for TEV RNA increased more than 4-fold compared with eIF4F alone (19.4 and 79.0 nm, respectively). The binding affinity of eIF4F to TEV RNA correlates with translation efficiency. VPg enhanced eIFiso4F binding to TEV RNA 1.6-fold (178 nm compared with 108 nm). Kinetic studies of eIF4F and eIFiso4F with VPg show ∼2.6-fold faster association for eIFiso4F·VPg as compared with eIF4F·VPg. The dissociation rate was ∼2.9-fold slower for eIFiso4F than eIF4F with VPg. These data demonstrate that eIFiso4F can kinetically compete with eIF4F for VPg binding. The quantitative data presented here suggest a model where eIF4F·VPg interaction enhances cap-independent translation by increasing the affinity of eIF4F for TEV RNA. This is the first evidence of direct participation of VPg in translation initiation.

scholarly journals Structural differences in translation initiation between pathogenic trypanosomatids and their mammalian hosts

2019 ◽  
Author(s):  
Anthony Bochler ◽  
Jailson Brito Querido ◽  
Terezie Prilepskaja ◽  
Heddy Soufari ◽  
Angelita Simonetti ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Trypanosoma Cruzi ◽  
Translation Initiation ◽  
Ribosomal Subunit ◽  
Mrna Translation ◽  
Mass Spectrometry Data ◽  
Initiation Complex ◽  
Initiation Factors ◽  
Eukaryotic Initiation Factors ◽  
Structural Differences

SUMMARYCanonical mRNA translation in eukaryotes begins with the formation of the 43S pre-initiation complex (PIC). Its assembly requires the binding of several eukaryotic initiation factors (eIF 1, 1A, 2, 3 and 5), Met-tRNAiMet and the small ribosomal subunit (40S). Compared to their mammalian hosts, trypanosomatids present significant structural differences in their 40S suggesting substantial variability in translation initiation. Here we determined the structure of the 43S PIC from Trypanosoma cruzi, the parasite causing the Chagas disease. Our structure shows numerous specific features, such as the variant eIF3 structure and its unique interactions with the large rRNA ESs 9S, 7S and 6S, and the association of a kinetoplastid-specific ~245 kDa DDX60-like helicase. It also revealed the so-far-elusive 40S-binding site of the eIF5 C-terminal domain and the structures of key terminal tails of several conserved eIFs underlying their activities within the PIC. Our results are corroborated by GST-pulldown assays in both human and T. cruzi and mass-spectrometry data.

Translational control by influenza virus: suppression of the kinase that phosphorylates the alpha subunit of initiation factor eIF-2 and selective translation of influenza viral mRNAs

1986 ◽  
Vol 6 (5) ◽  
pp. 1741-1750
Author(s):  
M G Katze ◽  
B M Detjen ◽  
B Safer ◽  
R M Krug
Keyword(s):  
Protein Synthesis ◽  
Influenza Virus ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Alpha Subunit ◽  
Viral Mrna ◽  
Viral Mrnas ◽  
Double Stranded Rna ◽  
Selective Translation ◽  
Infected Cells

Selective translation of influenza viral mRNAs occurs after influenza virus superinfection of cells infected with the VAI RNA-negative adenovirus mutant dl331 (M. G. Katze, Y.-T. Chen, and R. M. Krug, Cell 37:483-490, 1984). Cell extracts from these doubly infected cells catalyze the initiation of essentially only influenza viral protein synthesis, reproducing the in vivo situation. This selective translation is correlated with a 5- to 10-fold suppression of the dl331-induced kinase that phosphorylates the alpha subunit of eucaryotic initiation factor eIF-2. This strongly suggests that influenza virus encodes a gene product that, analogous to the adenoviral VAI RNA, prevents the shutdown of overall protein synthesis caused by an eIF-2 alpha kinase turned on by viral infection. Adenoviral mRNA translation was restored to the extract from the doubly infected cells by the addition of the guanine nucleotide exchange factor eIF-2B, which is responsible for the normal recycling of eIF-2 during protein synthesis. This indicates that the residual kinase in the doubly infected cells leads to a limitation in functional (nonsequestered) eIF-2B and hence functional (GTP-containing) eIF-2 and that under these conditions influenza viral mRNAs are selectively translated over adenoviral mRNAs. Addition of double-stranded RNA to the extracts from these cells restored the eIF-2 alpha kinase to a level approaching that seen in extracts from cells infected with dl331 alone and caused the inhibition of influenza viral mRNA translation. This suggests that the putative influenza viral gene product acts against the double-stranded RNA activation of the kinase and indicates that influenza viral mRNA translation is also linked to the level of functional eIF-2. Our results thus indicate that a limitation in functional eIF-2 which causes a nonspecific reduction in the rate of initiation of protein synthesis results in the preferential translation of the better mRNAs (influenza viral mRNAs) at the expense of the poorer mRNAs (adenoviral mRNAs).

scholarly journals Role of Eukaryotic Initiation Factors during Cellular Stress and Cancer Progression

2016 ◽  
Vol 2016 ◽  
pp. 1-19 ◽  
Author(s):  
Divya Khandige Sharma ◽  
Kamiko Bressler ◽  
Harshil Patel ◽  
Nirujah Balasingam ◽  
Nehal Thakor
Keyword(s):  
Protein Synthesis ◽  
Cancer Progression ◽  
Translation Initiation ◽  
Tumor Development ◽  
Mrna Translation ◽  
Translation Control ◽  
Initiation Factors ◽  
Eukaryotic Initiation Factors ◽  
Rate Limiting Step ◽  
Precise Understanding

Protein synthesis can be segmented into distinct phases comprising mRNA translation initiation, elongation, and termination. Translation initiation is a highly regulated and rate-limiting step of protein synthesis that requires more than 12 eukaryotic initiation factors (eIFs). Extensive evidence shows that the transcriptome and corresponding proteome do not invariably correlate with each other in a variety of contexts. In particular, translation of mRNAs specific to angiogenesis, tumor development, and apoptosis is altered during physiological and pathophysiological stress conditions. In cancer cells, the expression and functions of eIFs are hampered, resulting in the inhibition of global translation and enhancement of translation of subsets of mRNAs by alternative mechanisms. A precise understanding of mechanisms involving eukaryotic initiation factors leading to differential protein expression can help us to design better strategies to diagnose and treat cancer. The high spatial and temporal resolution of translation control can have an immediate effect on the microenvironment of the cell in comparison with changes in transcription. The dysregulation of mRNA translation mechanisms is increasingly being exploited as a target to treat cancer. In this review, we will focus on this context by describing both canonical and noncanonical roles of eIFs, which alter mRNA translation.

scholarly journals The Role of Mcl-1 inS. aureus-Induced Cytoprotection of Infected Macrophages

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Joanna Koziel ◽  
Katarzyna Kmiecik ◽  
Daniela Chmiest ◽  
Katarzyna Maresz ◽  
Danuta Mizgalska ◽  
...  
Keyword(s):  
De Novo ◽  
Myeloid Cell ◽  
Underlying Mechanism ◽  
Host Cells ◽  
Intracellular Pathogen ◽  
Dependent Inhibition ◽  
Infected Cells ◽  
The Stability

As a facultative intracellular pathogen,Staphylococcus aureusinvades macrophages and then promotes the cytoprotection of infected cells thus stabilizing safe niche for silent persistence. This process occurs through the upregulation of crucial antiapoptotic genes, in particular,myeloid cell leukemia-1 (MCL-1). Here, we investigated the underlying mechanism and signal transduction pathways leading to increasedMCL-1expression in infected macrophages. LiveS. aureusnot only stimulatedde novosynthesis of Mcl-1, but also prolonged the stability of this antiapoptotic protein. Consistent with this, we proved a crucial role of Mcl-1 inS. aureus-induced cytoprotection, since silencing ofMCL1by siRNA profoundly reversed the cytoprotection of infected cells leading to apoptosis. IncreasedMCL1expression in infected cells was associated with enhanced NFκB activation and subsequent IL-6 secretion, since the inhibition of both NFκB and IL-6 signalling pathways abrogated Mcl-1 induction and cytoprotection. Finally, we confirmed our observationin vivoin murine model of septic arthritis showing the association between the severity of arthritis and Mcl-1 expression. Therefore, we propose thatS. aureusis hijacking the Mcl-1-dependent inhibition of apoptosis to prevent the elimination of infected host cells, thus allowing the intracellular persistence of the pathogen, its dissemination by infected macrophages, and the progression of staphylococci diseases.

scholarly journals The Paradoxes of Viral mRNA Translation during Mammalian Orthoreovirus Infection

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 275
Author(s):  
Yingying Guo ◽  
John S. L. Parker
Keyword(s):  
De Novo ◽  
Mrna Translation ◽  
Host Cells ◽  
Viral Mrna ◽  
Host Defenses ◽  
Viral Protein Synthesis ◽  
Translational Machinery ◽  
Current State ◽  
Eukaryotic Mrnas ◽  
Mammalian Orthoreovirus

De novo viral protein synthesis following entry into host cells is essential for viral replication. As a consequence, viruses have evolved mechanisms to engage the host translational machinery while at the same time avoiding or counteracting host defenses that act to repress translation. Mammalian orthoreoviruses are dsRNA-containing viruses whose mRNAs were used as models for early investigations into the mechanisms that underpin the recognition and engagement of eukaryotic mRNAs by host cell ribosomes. However, there remain many unanswered questions and paradoxes regarding translation of reoviral mRNAs in the context of infection. This review summarizes the current state of knowledge about reovirus translation, identifies key unanswered questions, and proposes possible pathways toward a better understanding of reovirus translation.

scholarly journals Translational control by influenza virus: suppression of the kinase that phosphorylates the alpha subunit of initiation factor eIF-2 and selective translation of influenza viral mRNAs.

1986 ◽  
Vol 6 (5) ◽  
pp. 1741-1750 ◽  
Author(s):  
M G Katze ◽  
B M Detjen ◽  
B Safer ◽  
R M Krug
Keyword(s):  
Protein Synthesis ◽  
Influenza Virus ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Alpha Subunit ◽  
Viral Mrna ◽  
Viral Mrnas ◽  
Double Stranded Rna ◽  
Selective Translation ◽  
Infected Cells

Selective translation of influenza viral mRNAs occurs after influenza virus superinfection of cells infected with the VAI RNA-negative adenovirus mutant dl331 (M. G. Katze, Y.-T. Chen, and R. M. Krug, Cell 37:483-490, 1984). Cell extracts from these doubly infected cells catalyze the initiation of essentially only influenza viral protein synthesis, reproducing the in vivo situation. This selective translation is correlated with a 5- to 10-fold suppression of the dl331-induced kinase that phosphorylates the alpha subunit of eucaryotic initiation factor eIF-2. This strongly suggests that influenza virus encodes a gene product that, analogous to the adenoviral VAI RNA, prevents the shutdown of overall protein synthesis caused by an eIF-2 alpha kinase turned on by viral infection. Adenoviral mRNA translation was restored to the extract from the doubly infected cells by the addition of the guanine nucleotide exchange factor eIF-2B, which is responsible for the normal recycling of eIF-2 during protein synthesis. This indicates that the residual kinase in the doubly infected cells leads to a limitation in functional (nonsequestered) eIF-2B and hence functional (GTP-containing) eIF-2 and that under these conditions influenza viral mRNAs are selectively translated over adenoviral mRNAs. Addition of double-stranded RNA to the extracts from these cells restored the eIF-2 alpha kinase to a level approaching that seen in extracts from cells infected with dl331 alone and caused the inhibition of influenza viral mRNA translation. This suggests that the putative influenza viral gene product acts against the double-stranded RNA activation of the kinase and indicates that influenza viral mRNA translation is also linked to the level of functional eIF-2. Our results thus indicate that a limitation in functional eIF-2 which causes a nonspecific reduction in the rate of initiation of protein synthesis results in the preferential translation of the better mRNAs (influenza viral mRNAs) at the expense of the poorer mRNAs (adenoviral mRNAs).

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