Poly(A)-Binding Protein Increases the Binding Affinity and Kinetic Rates of Interaction of Viral Protein Linked to Genome with Translation Initiation Factors eIFiso4F and eIFiso4F·4B Complex

Biochemistry ◽  
2012 ◽  
Vol 51 (7) ◽  
pp. 1388-1395 ◽  
Author(s):  
Mateen A. Khan ◽  
Dixie J. Goss
Keyword(s):  
Binding Affinity ◽  
Translation Initiation ◽  
Viral Protein ◽  
Binding Protein ◽  
Initiation Factors ◽  
Translation Initiation Factors ◽  
Kinetic Rates

scholarly journals The EIF4E1-4EIP cap-binding complex of Trypanosoma brucei interacts with the terminal uridylyl transferase TUT3

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0258903
Author(s):  
Franziska Falk ◽  
Kevin Kamanyi Marucha ◽  
Christine Clayton
Keyword(s):  
Trypanosoma Brucei ◽  
Translation Initiation ◽  
Binding Protein ◽  
Procyclic Form ◽  
Initiation Factors ◽  
Control Gene Expression ◽  
Translation Initiation Factors ◽  
Cap Binding Complex ◽  
The Stability ◽  
Reporter Mrna

Most transcription in Trypanosoma brucei is constitutive and polycistronic. Consequently, the parasite relies on post-transcriptional mechanisms, especially affecting translation initiation and mRNA decay, to control gene expression both at steady-state and for adaptation to different environments. The parasite has six isoforms of the cap-binding protein EIF4E as well as five EIF4Gs. EIF4E1 does not bind to any EIF4G, instead being associated with a 4E-binding protein, 4EIP. 4EIP represses translation and reduces the stability of a reporter mRNA when artificially tethered to the 3’-UTR, whether or not EIF4E1 is present. 4EIP is essential during the transition from the mammalian bloodstream form to the procyclic form that lives in the Tsetse vector. In contrast, EIF4E1 is dispensable during differentiation, but is required for establishment of growing procyclic forms. In Leishmania, there is some evidence that EIF4E1 might be active in translation initiation, via direct recruitment of EIF3. However in T. brucei, EIF4E1 showed no detectable association with other translation initiation factors, even in the complete absence of 4EIP. There was some evidence for interactions with NOT complex components, but if these occur they must be weak and transient. We found that EIF4E1is less abundant in the absence of 4EIP, and RNA pull-down results suggested this might occur through co-translational complex assembly. We also report that 4EIP directly recruits the cytosolic terminal uridylyl transferase TUT3 to EIF4E1/4EIP complexes. There was, however, no evidence that TUT3 is essential for 4EIP function.

scholarly journals Uncoupling Stress Granule Assembly and Translation Initiation Inhibition

2009 ◽  
Vol 20 (11) ◽  
pp. 2673-2683 ◽  
Author(s):  
Sophie Mokas ◽  
John R. Mills ◽  
Cristina Garreau ◽  
Marie-Josée Fournier ◽  
Francis Robert ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Binding Protein ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Ribosomal Subunits ◽  
Initiation Factors ◽  
Eif2α Phosphorylation ◽  
Translation Initiation Factors ◽  
Dependent Pathway ◽  
Regulatory Sites

Cytoplasmic stress granules (SGs) are specialized regulatory sites of mRNA translation that form under different stress conditions known to inhibit translation initiation. The formation of SG occurs via two pathways; the eukaryotic initiation factor (eIF) 2α phosphorylation-dependent pathway mediated by stress and the eIF2α phosphorylation-independent pathway mediated by inactivation of the translation initiation factors eIF4A and eIF4G. In this study, we investigated the effects of targeting different translation initiation factors and steps in SG formation in HeLa cells. By depleting eIF2α, we demonstrate that reduced levels of the eIF2.GTP.Met-tRNAiMet ternary translation initiation complexes is sufficient to induce SGs. Likewise, reduced levels of eIF4B, eIF4H, or polyA-binding protein, also trigger SG formation. In contrast, depletion of the cap-binding protein eIF4E or preventing its assembly into eIF4F results in modest SG formation. Intriguingly, interfering with the last step of translation initiation by blocking the recruitment of 60S ribosome either with 2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamideis or through depletion of the large ribosomal subunits protein L28 does not induce SG assembly. Our study identifies translation initiation steps and factors involved in SG formation as well as those that can be targeted without induction of SGs.

scholarly journals Translation Initiation Factors eIF-iso4G and eIF-4B Interact with the Poly(A)-binding Protein and Increase Its RNA Binding Activity

1997 ◽  
Vol 272 (26) ◽  
pp. 16247-16255 ◽  
Author(s):  
Hanh Le ◽  
Robert L. Tanguay ◽  
M. Luisa Balasta ◽  
Chin-Chuan Wei ◽  
Karen S. Browning ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Rna Binding ◽  
Binding Protein ◽  
Binding Activity ◽  
Initiation Factors ◽  
Translation Initiation Factors

scholarly journals Resistance to Plum pox virus Strain C in Arabidopsis thaliana and Chenopodium foetidum Involves Genome-Linked Viral Protein and Other Viral Determinants and Might Depend on Compatibility With Host Translation Initiation Factors

2014 ◽  
Vol 27 (11) ◽  
pp. 1291-1301 ◽  
Author(s):  
María Calvo ◽  
Sandra Martínez-Turiño ◽  
Juan Antonio García
Keyword(s):  
Arabidopsis Thaliana ◽  
Translation Initiation ◽  
Viral Protein ◽  
Molecular Mechanisms ◽  
Viral Infections ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Plum Pox Virus ◽  
Initiation Factors ◽  
Translation Initiation Factors

Research performed on model herbaceous hosts has been useful to unravel the molecular mechanisms that control viral infections. The most common Plum pox virus (PPV) strains are able to infect Nicotiana species as well as Chenopodium and Arabidopsis species. However, isolates belonging to strain C (PPV-C) that have been adapted to Nicotiana spp. are not infectious either in Chenopodium foetidum or in Arabidopsis thaliana. In order to determine the mechanism underlying this interesting host-specific behavior, we have constructed chimerical clones derived from Nicotiana-adapted PPV isolates from the D and C strains, which differ in their capacity to infect A. thaliana and C. foetidum. With this approach, we have identified the nuclear inclusion a protein (VPg+Pro) as the major pathogenicity determinant that conditions resistance in the presence of additional secondary determinants, different for each host. Genome-linked viral protein (VPg) mutations similar to those involved in the breakdown of eIF4E-mediated resistance to other potyviruses allow some PPV chimeras to infect A. thaliana. These results point to defective interactions between a translation initiation factor and the viral VPg as the most probable cause of host-specific incompatibility, in which other viral factors also participate, and suggest that complex interactions between multiple viral proteins and translation initiation factors not only define resistance to potyviruses in particular varieties of susceptible hosts but also contribute to establish nonhost resistance.

scholarly journals Mechanisms of translation repression by the EIF4E1-4EIP cap-binding complex of Trypanosoma brucei: potential roles of the NOT complex and a terminal uridylyl transferase

2021 ◽  
Author(s):  
Franziska Falk ◽  
Kevin Kamanyi Marucha ◽  
Christine Clayton
Keyword(s):  
Trypanosoma Brucei ◽  
Translation Initiation ◽  
Binding Protein ◽  
Initiation Factors ◽  
Control Gene Expression ◽  
Translation Initiation Factors ◽  
Cap Binding Complex ◽  
Competing Models ◽  
The Stability ◽  
Reporter Mrna

Most transcription in Trypanosoma brucei is constitutive and polycistronic. Consequently, the parasite relies on post-transcriptional mechanisms, especially affecting translation initiation and mRNA decay, to control gene expression both at steady-state and for adaptation to different environments. The parasite has six isoforms of the cap-binding protein EIF4E as well as five EIF4Gs. EIF4E1 does not bind to any EIF4G, instead being associated with a 4E-binding protein, 4EIP. 4EIP represses translation and reduces the stability of a reporter mRNA when artificially tethered to the 3'-UTR, whether or not EIF4E1 is present. 4EIP is essential during the transition from the mammalian bloodstream form to the procyclic form that lives in the Tsetse vector. In contrast, EIF4E1 is dispensable during differentiation, but is required for establishment of growing procyclic forms. There are two competing models for EIF4E1 function: either EIF4E1 has translation initiation activity that is inhibited by 4EIP, or EIF4E1 acts only as an inhibitor. We here provide evidence for the second hypothesis. Even in the complete absence of 4EIP, EIF4E1 showed no detectable association with other translation initiation factors, and 4EIP loss caused no detectable change in 4E1-associated mRNAs. We found that 4EIP stabilises EIF4E1, probably through co-translational complex assembly, and that 4EIP directly recruits the cytosolic terminal uridylyl transferase TUT3 to EIF4E1/4EIP complexes. There was, however, no evidence that TUT3 is essential for 4EIP function; instead, some evidence implicated the NOT deadenylase complex.

scholarly journals Composition of Herpesvirus Ribonucleoprotein Complexes

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 119
Author(s):  
Eric S. Pringle ◽  
Craig McCormick
Keyword(s):  
Protein Synthesis ◽  
Translation Initiation ◽  
Viral Protein ◽  
Lytic Replication ◽  
Viral Mrna ◽  
Viral Protein Synthesis ◽  
Initiation Factors ◽  
Ribonucleoprotein Complexes ◽  
Virion Production ◽  
Translation Initiation Factors

Herpesvirus genomes are decoded by host RNA polymerase enzymes, generating messenger ribonucleotides (mRNA) that are post-transcriptionally modified and exported to the cytoplasm through the combined work of host and viral factors. These viral mRNA bear 5′-m7GTP caps and poly(A) tails that should permit the assembly of canonical host eIF4F cap-binding complexes to initiate protein synthesis. However, the precise mechanisms of translation initiation remain to be investigated for Kaposi’s sarcoma-associated herpesvirus (KSHV) and other herpesviruses. During KSHV lytic replication in lymphoid cells, the activation of caspases leads to the cleavage of eIF4G and depletion of eIF4F. Translating mRNPs depleted of eIF4F retain viral mRNA, suggesting that non-eIF4F translation initiation is sufficient to support viral protein synthesis. To identify proteins required to support viral protein synthesis, we isolated and characterized actively translating messenger ribonucleoprotein (mRNP) complexes by ultracentrifugation and sucrose-gradient fractionation followed by quantitative mass spectrometry. The abundance of host translation initiation factors available to initiate viral protein synthesis were comparable between cells undergoing KSHV lytic or latent replication. The translation initiation factors eIF4E2, NCBP1, eIF4G2, and eIF3d were detected in association with actively translating mRNP complexes during KSHV lytic replication, but their depletion by RNA silencing did not affect virion production. By contrast, the N6-methyladenosine methyltransferase METTL3 was required for optimal late gene expression and virion production, but was dispensable for genome replication. Furthermore, we detected several KSHV proteins in actively translating mRNP complexes that had not previously been shown to play roles in viral protein synthesis. We conclude that KSHV usurps distinct host translation initiation systems during latent and lytic phases of infection.

scholarly journals Insights from a Paradigm Shift: How the Poly(A)-Binding Protein Brings Translating mRNAs Full Circle

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Daniel R. Gallie
Keyword(s):  
Translation Initiation ◽  
Paradigm Shift ◽  
Binding Protein ◽  
Ribosomal Subunit ◽  
Physical Interaction ◽  
New Paradigm ◽  
Initiation Factors ◽  
Full Circle ◽  
Translation Initiation Factors ◽  
Cap Binding Complex

In recent years, our thinking of how the initiation of protein synthesis occurs has changed dramatically. Initiation was thought to involve only events occurring at or near the 5′-cap structure, which serves as the binding site for the cap-binding complex, a group of translation initiation factors (eIFs) that facilitate the binding of the 40 S ribosomal subunit to an mRNA. Because the poly(A)-binding protein (PABP) binds the poly(A) tail present at the 3′-terminus of an mRNA, it was long thought to play no role in translation initiation. In this review, I present evidence from my laboratory that has contributed to the paradigm shift in how we think of mRNAs during translation. The depiction of mRNAs as straight molecules in which the poly(A) tail is far from events occurring at the 5′-end has now been replaced by the concept of a circular mRNA where the interaction between PABP and the cap-binding complex bridges the termini of an mRNA and promotes translation initiation. The research from my laboratory supports the new paradigm that translation of most mRNAs requires a functional and physical interaction between the termini of an mRNA.

scholarly journals The helicase, DDX3X, interacts with poly(A)-binding protein 1 (PABP1) and caprin-1 at the leading edge of migrating fibroblasts and is required for efficient cell spreading

2017 ◽  
Vol 474 (18) ◽  
pp. 3109-3120 ◽  
Author(s):  
Alice C. Copsey ◽  
Simon Cooper ◽  
Robert Parker ◽  
Ella Lineham ◽  
Cuzack Lapworth ◽  
...  
Keyword(s):  
Cell Motility ◽  
Translation Initiation ◽  
Protein Interactions ◽  
Cell Cycle Progression ◽  
Binding Protein ◽  
Leading Edge ◽  
Actin Dynamics ◽  
Functional Link ◽  
Initiation Factors ◽  
Translation Initiation Factors

DDX3X, a helicase, can interact directly with mRNA and translation initiation factors, regulating the selective translation of mRNAs that contain a structured 5′ untranslated region. This activity modulates the expression of mRNAs controlling cell cycle progression and mRNAs regulating actin dynamics, contributing to cell adhesion and motility. Previously, we have shown that ribosomes and translation initiation factors localise to the leading edge of migrating fibroblasts in loci enriched with actively translating ribosomes, thereby promoting steady-state levels of ArpC2 and Rac1 proteins at the leading edge of cells during spreading. As DDX3X can regulate Rac1 levels, cell motility and metastasis, we have examined DDX3X protein interactions and localisation using many complementary approaches. We now show that DDX3X can physically interact and co-localise with poly(A)-binding protein 1 and caprin-1 at the leading edge of spreading cells. Furthermore, as depletion of DDX3X leads to decreased cell motility, this provides a functional link between DDX3X, caprin-1 and initiation factors at the leading edge of migrating cells to promote cell migration and spreading.

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