EIF4E-independent translation is largely eIF3d-dependent
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE243708 | GEO | 2024/08/07
REPOSITORIES: GEO
Similar Datasets
Project description:Shutoff of global protein synthesis is a conserved response to cellular stresses. This general phenomenon is accompanied by induction of distinct gene programs tailored to each stress condition. Although the mechanisms that lead to general repression of protein synthesis are well characterized, how cells reprogram the translation machinery for selective gene expression remains poorly understood. Here we show that the noncanonical 5′ cap-binding protein eIF3d is specifically activated in response to metabolic stress, due to loss of CK2-mediated phosphorylation near the eIF3d cap-binding pocket. Activated eIF3d controls a gene program enriched in factors important for glucose homeostasis, including members of the mTOR pathway, and eIF3d-mediated translation adaptation is essential for cell survival during chronic glucose deprivation. Our findings reveal a new mechanism of translation reprogramming engaged in response to metabolic stress.
2020-11-16 | GSE158249 | GEO
Project description:All cells respond to intrinsic and extrinsic stresses by reducing global protein synthesis and activating select gene programs necessary for survival. Here, we show the fundamental integrated stress response (ISR) is driven by the non-canonical cap-binding protein eIF3d which acts as a master effector to control core stress response orchestrators, the translation factor eIF2ɑ and the transcription factor ATF4. We find that during persistent stress, eIF3d activates translation of the protein kinase GCN2, inducing eIF2ɑ phosphorylation and inhibiting global protein synthesis. In parallel, eIF3d upregulates the m6A demethylase enzyme ALKBH5 to drive 5′ UTR-specific demethylation of stress response genes, including ATF4. Ultimately, this cascade converges on ATF4 expression by increasing mRNA engagement of translation machinery and enhancing ribosome bypass of upstream open reading frames. Our results reveal that eIF3d acts as a critical life-or-death decision point during adaptation to chronic stress and uncover a synergistic signaling mechanism in which translational cascades dynamically complement transcriptional amplification to control essential cellular processes.
2023-09-11 | GSE236188 | GEO
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.
2023-11-02 | GSE243206 | GEO
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.
2023-11-02 | GSE243203 | GEO
Project description:The protozoan parasite Toxoplasma gondii causes serious opportunistic disease due to its ability to persist in patients as latent tissue cysts. The molecular mechanisms coordinating conversion between proliferative parasites (tachyzoites) and latent cysts (bradyzoites) are not fully understood. We previously showed that phosphorylation of eIF2α accompanies bradyzoite formation, suggesting that this clinically relevant process involves regulation of mRNA translation. In this study, we investigated the composition and role of eIF4F multi-subunit complexes in translational control. Using CLIPseq, we find that the cap-binding subunit, eIF4E1, localizes to the 5’-end of all tachyzoite mRNAs, many of which show evidence of stemming from heterogenous transcriptional start sites. We further show that eIF4E1 operates as the predominant cap-binding protein in two distinct eIF4F complexes. Using genetic and pharmacological approaches, we found that eIF4E1 deficiency triggers efficient spontaneous formation of bradyzoites without stress induction. Consistent with this result, we also show that stress-induced bradyzoites exhibit reduced eIF4E1 expression. Overall, our findings establish a novel role for eIF4F in translational control required for parasite latency and microbial persistence.
2024-03-26 | GSE262241 | GEO
Project description:Viral infection often triggers eukaryotic initiator factor 2α (eIF2α) phosphorylation, leading to global 5’-cap-dependent translation inhibition. RSV encodes messenger RNAs (mRNAs) mimicking 5’-cap structures of host mRNAs and thus inhibition of cap-dependent translation initiation would likely also reduce viral translation. We confirmed that RSV limits widespread translation initiation inhibition and unexpectedly found that the fraction of ribosomes within polysomes increases during infection, indicating higher ribosome loading on mRNAs during infection. We found that AU-rich host transcripts that are less efficiently translated under normal conditions become more efficient at recruiting ribosomes, similar to RSV transcripts. Viral transcripts are transcribed in cytoplasmic inclusion bodies, where the viral AU-rich binding protein M2-1 has been shown to bind viral transcripts and shuttle them into the cytoplasm. We further demonstrated that M2-1 is found on polysomes, and that M2-1 might deliver host AU-rich transcripts for translation.
2024-09-03 | GSE268742 | GEO
Project description:Cap homeostasis is the cyclical process of decapping and recapping that maintains the translation and stability of a subset of the transcriptome. Previous work showed levels of some recapping targets decline following transient expression of an inactive form of RNMT (ΔN-RNMT), likely due to degradation of mRNAs with improperly methylated caps. The current study examined transcriptome-wide changes following inhibition of cytoplasmic cap methylation. This identified mRNAs with 5’-terminal oligopyrimidine (TOP) sequences as the largest single class of recapping targets. Cap end mapping of several TOP mRNAs identified recapping events at native 5’ ends and downstream of the TOP sequence of EIF3K and EIF3D. This provides the first direct evidence for downstream recapping. Inhibition of cytoplasmic cap methylation was also associated with mRNA abundance increases for a number of transcription, splicing, and 3’ processing factors. Previous work suggested a role for alternative polyadenylation in target selection, but this proved not to be the case. However, inhibition of cytoplasmic cap methylation resulted in a shift of upstream polyadenylation sites to annotated 3’ ends. Together, these results solidify cap homeostasis as a fundamental process of gene expression control and show cytoplasmic recapping can impact regulatory elements present at the ends of mRNA molecules.
2020-01-16 | GSE142848 | GEO
Project description:Mammalian mRNAs are generated by complex and coordinated biogenesis pathways and acquire 5'-end m7G caps that play fundamental roles in processing and translation. Here we show that several selenoprotein mRNAs are not recognized efficiently by translation initiation factor eIF4E because they bear a hypermethylated cap. This cap modification is acquired via a 5M-bM-^@M-^Yend maturation pathway similar to that of the small nucle(ol)ar RNAs (sn- and snoRNAs). Our findings also establish that the trimethylguanosine synthase 1 (Tgs1) interacts with selenoprotein mRNAs for cap hypermethylation and that assembly chaperones and core proteins devoted to sn- and snoRNP maturation contribute to recruiting Tgs1 to selenoprotein mRNPs. We further demonstrate that the hypermethylated-capped selenoprotein mRNAs localize to the cytoplasm, are associated with polysomes and thus translated. Moreover, we found that the activity of Tgs1, but not of eIF4E, is required for the synthesis of the GPx1 selenoprotein in vivo. In total 7 samples; 3 control IP (HeLa 1,2 & 9), 2 TGS1-SF IP(C2 & C2b) and 2 TGS1-LF IP(C7 & C7b)
2014-05-14 | E-GEOD-57625 | biostudies-arrayexpress
Project description:The phosphorylation of eIF4E1 at serine 209 by MNK1 or MNK2 has been shown to initiate oncogenic mRNA translation, a process that favours cancer development and maintenance. Here, we interrogate the MNK-eIF4E axis in diffuse large B-cell lymphoma (DLBCL) and show a distinct distribution of MNK1 and MNK2 in germinal centre B-cell (GCB) and activated B-cell (ABC) DLBCL. Despite displaying a differential distribution in GCB and ABC, both MNKs functionally complement each other to sustain cell survival. MNK inhibition ablates eIF4E1 phosphorylation and concurrently enhances eIF4E3 expression. Loss of MNK protein itself down-regulates total eIF4E1 protein level by reducing eIF4E1 mRNA polysomal loading without affecting total mRNA level or stability. Enhanced eIF4E3 expression marginally suppresses eIF4E1-driven translation but exhibits a unique translatome that unveils a novel role for eIF4E3 in translation initiation. Together, we propose that MNKs can modulate oncogenic translation by regulating eIF4E1-eIF4E3 levels and activity in DLBCL. As the knockdown of eIF4E1 or eIF4E3 caused significant cell death, we overexpressed either protein in HLY-1 cells and performed sucrose density gradient fractionation. RNA was extracted from polysome fractions #9-10, containing highly translated polysome-bound mRNAs, from total RNA and from an empty vector control. These samples, in triplicate, were used for either translatome or transcriptome analysis using Illumina HumanHT-12 v4 BeadChips for gene expression analysis.
2014-11-18 | E-GEOD-61691 | biostudies-arrayexpress
Project description:Regulation of HCMV replication by eIF3d
| PRJEB45749 | ENA