Epstein-Barr virus protein EB2 stimulates translation initiation of mRNAs through direct interactions with both PABP and eIF4G
Ontology highlight
ABSTRACT:
INSTRUMENT(S): LTQ XL ETD
ORGANISM(S): Homo Sapiens (human)
TISSUE(S): Cell Culture, Early Embryonic Cell
SUBMITTER: 
Frederic DELOLME
LAB HEAD: Frederic DELOLME
PROVIDER: PXD003800 | Pride | 2022-03-03
REPOSITORIES: Pride
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| 1099.raw | Raw | |||
| 1099_SprotDBPanthuB.msf-pride.pride.mgf.gz | Mgf | |||
| 1099_SprotDBPanthuB.msf-pride.pride.mztab.gz | Mztab | |||
| 1099_SprotDBPanthuB.msf-pride.xml.gz | Xml | |||
| 1100.raw | Raw |
Items per page: 5 1 - 5 of 12 |
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Project description:In eukaryotic cells, protein synthesis typically begins with the binding of eIF4F to the 7-methylguanylate (m7G)cap found on the 5’ end of the majority of mRNAs. Surprisingly, overall translational output remains robust under eIF4F inhibition. The sustained protein synthesis has been largely attributed to cap-independent translation mediated by internal ribosome entry sites (IRES). However, the IRES-driven translation is substrate-specific and largely incompatible with the broad spectrum of eIF4F-resistant translatomes.Here, we report that N6-methyladenosine (m6A)-mediated translation prevails on capped mRNAs and is resistant to eIF4F inactivation.Depletion of the methyltransferase METTL3 selectively inhibits translation of mRNAs bearing 5’UTR methylation, but not mRNAs with 5’ terminal oligopyrimidine (TOP) elements. Mechanistically, we identify ABCF1 as a critical mediator of m6A-promoted translation under both stress and physiological conditions. Supporting the role of ABCF1 in m6A-mediated cap-independent translation, ABCF1-sensitive transcripts largely overlap with METTL3-responsible mRNA targets. By illustrating the scope and the mechanism of translation initiation that is neither cap- nor IRES-dependent, these findingsreshape our current perceptions of cellular translational pathways
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Project description:All mRNAs are bound in vivo by proteins to form mRNA–protein complexes (mRNPs), but changes in the composition of mRNPs during post-transcriptional regulation remain largely unexplored. Here, we have analyzed, on a transcriptome-wide scale, how microRNA-mediated repression modulates the associations of core components (eIF4E, eIF4G, and PABP) and of the decay factor DDX6 in human cells. Despite the transient nature of repressed intermediates, we detected significant changes in mRNP composition, marked by dissociation of eIF4G and PABP, and by recruitment of DDX6. Furthermore, although poly(A)-tail length has been considered critical in post-transcriptional regulation, differences in steady-state tail length explained little of the variation in either PABP association or mRNP organization more generally. Instead, relative occupancy of core components correlated best with gene expression. Together, these results indicate that posttranscriptional regulatory factors influence the associations of PABP and other core factors, and do so without substantially affecting steady-state tail length.
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Project description:Gene expression results from mRNA - RNA-binding protein (RBP) interactions within messenger ribonucleoprotein (mRNP) particles. We identified heterogeniety of nuclear mRNP composition involved in mRNA biogenesis and export with different occupancy and stoichiometry of RNA-binding proteins. Especially, mRNA export adopter protein Yra1 showed large variation of its stoichiometry on single mRNPs. We identified stoichiometry of Yra1 in the nuclear cap binding complex (Cbp80) bound mRNPs and it can be dissected into two categories (one and multiple Yra1 bound mRNPs). Multiple Yra1 containing mRNPs specifically co-occupied with THO complex (Hpr1). To investigate gene dependency to form different Yra1 stoichiometry mRNPs, we performed RNA-IP experiment for Yra1 with two step purification by Cbp80/Yra1 and Hpr1/Yra1.
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Project description:Identification of eukaryotic mRNAs that are translated at reduced cap binding complex eIF4F concentrations using a cDNA microarray. Although most eukaryotic mRNAs need a functional cap binding complex eIF4F for efficient 5' end-dependent scanning to initiate translation, picornaviral, hepatitis C viral, and a few cellular RNAs have been shown to be translated by internal ribosome entry, a mechanism that can operate in the presence of low levels of functional eIF4F. To identify cellular mRNAs that can be translated when eIF4F is depleted or in low abundance and that, therefore, may contain internal ribosome entry sites, mRNAs that remained associated with polysomes were isolated from human cells after infection with poliovirus and were identified by using a cDNA microarray. Approximately 200 of the 7000 mRNAs analyzed remained associated with polysomes under these conditions. Among the gene products encoded by these polysome-associated mRNAs were immediate-early transcription factors, kinases, and phosphatases of the mitogen-activated protein kinase pathways and several protooncogenes, including c-myc and Pim-1. In addition, the mRNA encoding Cyr61, a secreted factor that can promote angiogenesis and tumor growth, was selectively mobilized into polysomes when eIF4F concentrations were reduced, although its overall abundance changed only slightly. Subsequent tests confirmed the presence of internal ribosome entry sites in the 5' noncoding regions of both Cyr61 and Pim-1 mRNAs. Overall, this study suggests that diverse mRNAs whose gene products have been implicated in a variety of stress responses, including inflammation, angiogenesis, and the response to serum, can use translational initiation mechanisms that require little or no intact cap binding protein complex eIF4F. This study is described more fully in Johannes G et al.(1999) Proc Natl Acad Sci U S A 96:13118-23.
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Project description:Although most eukaryotic mRNAs need a functional cap binding complex eIF4F for efficient 5' end- dependent scanning to initiate translation, picornaviral, hepatitis C viral, and a few cellular RNAs have been shown to be translated by internal ribosome entry, a mechanism that can operate in the presence of low levels of functional eIF4F. To identify cellular mRNAs that can be translated when eIF4F is depleted or in low abundance and that, therefore, may contain internal ribosome entry sites, mRNAs that remained associated with polysomes were isolated from human cells after infection with poliovirus and were identified by using a cDNA microarray. Approximately 200 of the 7000 mRNAs analyzed remained associated with polysomes under these conditions. Among the gene products encoded by these polysome-associated mRNAs were immediate-early transcription factors, kinases, and phosphatases of the mitogen-activated protein kinase pathways and several protooncogenes, including c-myc and Pim-1. In addition, the mRNA encoding Cyr61, a secreted factor that can promote angiogenesis and tumor growth, was selectively mobilized into polysomes when eIF4F concentrations were reduced, although its overall abundance changed only slightly. Subsequent tests confirmed the presence of internal ribosome entry sites in the 5' noncoding regions of both Cyr61 and Pim-1 mRNAs. Overall, this study suggests that diverse mRNAs whose gene products have been implicated in a variety of stress responses, including inflammation, angiogenesis, and the response to serum, can use translational initiation mechanisms that require little or no intact cap binding protein complex eIF4F.
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Project description:Many eIF4F subunits and PABP paralogues are found in trypanosomes: six eIF4E, five eIF4G, one eIF4A and two PABPs. They are expressed simultaneously and assemble into different complexes, contrasting the situation in metazoans that use distinct complexes in different cell types or developmental stages. Each eIF4F complex has its own proteins, mRNAs and, consequently, a distinct function. We set out to study the function and regulation of the two major eIF4F complexes of Trypanosoma cruzi. We identified the associated proteins and mRNAs of eIF4E3 and eIF4E4 in cells in exponential growth and in nutritional stress. Upon stress, eIF4G/eIF4A and PABP remain associated to the eIF4E, but the association with other 43S pre-initiation factors decreases, indicating that ribosome attachment is impaired. Most eIF4E3-associated mRNAs encode for metabolic proteins, while eIF4E4 associate to mRNAs encoding ribosomal proteins. Interestingly, for both eIF4E3/4, more mRNAs were associated in stressed cells than in non-stressed cells, even though stress causes ribosome disassembly. In summary, trypanosomes have two co-existing eIF4F complexes involved in translation of distinct mRNA cohorts important for growth. Under stress conditions, both complexes exit translation but remain bound to their mRNA targets.
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Project description:Identification of eukaryotic mRNAs that are translated at reduced cap binding complex eIF4F concentrations using a cDNA microarray. Although most eukaryotic mRNAs need a functional cap binding complex eIF4F for efficient 5' end-dependent scanning to initiate translation, picornaviral, hepatitis C viral, and a few cellular RNAs have been shown to be translated by internal ribosome entry, a mechanism that can operate in the presence of low levels of functional eIF4F. To identify cellular mRNAs that can be translated when eIF4F is depleted or in low abundance and that, therefore, may contain internal ribosome entry sites, mRNAs that remained associated with polysomes were isolated from human cells after infection with poliovirus and were identified by using a cDNA microarray. Approximately 200 of the 7000 mRNAs analyzed remained associated with polysomes under these conditions. Among the gene products encoded by these polysome-associated mRNAs were immediate-early transcription factors, kinases, and phosphatases of the mitogen-activated protein kinase pathways and several protooncogenes, including c-myc and Pim-1. In addition, the mRNA encoding Cyr61, a secreted factor that can promote angiogenesis and tumor growth, was selectively mobilized into polysomes when eIF4F concentrations were reduced, although its overall abundance changed only slightly. Subsequent tests confirmed the presence of internal ribosome entry sites in the 5' noncoding regions of both Cyr61 and Pim-1 mRNAs. Overall, this study suggests that diverse mRNAs whose gene products have been implicated in a variety of stress responses, including inflammation, angiogenesis, and the response to serum, can use translational initiation mechanisms that require little or no intact cap binding protein complex eIF4F. This study is described more fully in Johannes G et al.(1999) Proc Natl Acad Sci U S A 96:13118-23. Keywords: other
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Project description:Ingestion of Toxoplasma gondii results in life-long infection due to its ability to convert from the rapidly disseminating tachyzoite stage to the chronic, encysted bradyzoite stage. The control of mRNA translation has been suggested to play a key role in the signaling required to trigger bradyzoite formation. In eukaryotes, translational control primarily operates at two key points during the assembly of translation initiation factors. The phosphorylation of eIF2 affects mRNA start codon recognition and promotes differentiation in a variety of parasites. Modulating eIF4F function is the second pan-eukaryote regulatory point but remains unexplored in Toxoplasma. Here, we uncover the role that eIF4F-centric regulation plays in regulating bradyzoite formation by targeting the cap-binding subunit, eIF4E1. We discover that eIF4E1 coordinates two eIF4F complexes and binds the 5’-end of all mRNAs transcribed in tachyzoites, many of which show evidence of stemming from heterogenous transcriptional start sites. Together, this indicates that eIF4E1 is the predominant cap-binding protein in Toxoplasma tachyzoites. We also demonstrate that eIF4E1 knockdown or its chemical inhibition triggers the efficient formation of bradyzoites in the absence of other stresses and that stress-induced bradyzoites reduce their eIF4E1 expression. This study unearths a role for eIF4F-centric translational control in controlling Toxoplasma differentiation, suggesting that control of cap-dependent translation regulates the process of bradyzoite formation.
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Project description:Hepatitis C Virus protein NS5A was found to upregulate assembly of cap binding initiation complex eIF4F in Huh7.5 cells. NS5A also was found to associate with translation machinery. To understand consequences of NS5A mediation in host translation, we analyzed mRNA associated with polysome fractions of NS5A expressing Huh7.5 cells and compared them with the corresponding fractions from control cells. Agilent-027114 Genotypic Technology designed Custom Human Whole Genome 8x60k Microarray
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