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 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 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 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 Mutations in Translation Initiation Factors Lead to Increased Rates of Deadenylation and Decapping of mRNAs inSaccharomyces cerevisiae

1999 ◽  
Vol 19 (8) ◽  
pp. 5247-5256 ◽  
Author(s):  
David C. Schwartz ◽  
Roy Parker
Keyword(s):  
Translation Initiation ◽  
Mrna Decay ◽  
Critical Role ◽  
Critical Factor ◽  
Decay Rates ◽  
Initiation Factors ◽  
Translation Initiation Factors ◽  
The Status ◽  
Cap Binding Complex ◽  
Mrna Half Life

ABSTRACT The turnover of most mRNAs in Saccharomyces cerevisiaebegins with deadenylation followed by decapping and 5′→3′ exonucleolytic digestion. An important question involves the mechanisms that allow particular mRNAs to exhibit different rates of both deadenylation and decapping. Since the cap structure plays a critical role in the assembly of translation initiation factors, we hypothesized that the status of the cytoplasmic cap binding complex would affect the rate of decapping. To test this hypothesis, we examined mRNA decay rates in yeast strains that were defective in several translation initiation factors that are part of the cap binding complex. These experiments yielded three significant observations. First, any mutation known to inhibit translation initiation also increased the rate of decapping. Second, decapping still occurred only after deadenylation, suggesting that the ability of the poly(A) tail to inhibit decapping does not require efficient translation of the transcript. Third, mutants with defects in translation initiation factors also showed an increase in the rate of deadenylation, suggesting that the rate of deadenylation may be controlled primarily by the translation status of the transcript. These results argue that the nature of the translation initiation complex is a critical factor in determining the mRNA half-life. This view also implies that some cis-acting sequences that modulate mRNA decay rate do so by affecting the translation status of the transcript.

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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