A phosphorylation-regulated eIF3d translation switch mediates cellular adaptation to metabolic stress
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE158249 | GEO | 2020/11/16
REPOSITORIES: GEO
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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:We study here how mRNAs are translated in an eIF4E1-independent manner by blocking eIF4E1 using a constitutively active version of eIF4E-binding protein (4E-BP). Via ribosome profiling we identify a subset of mRNAs that are still efficiently translated when eIF4E1 is inactive. We find that these mRNAs preferentially release eIF4E1 when eIF4E1 is inactive and bind instead to eIF3D via its cap-binding pocket. eIF3D then enables these mRNAs to be efficiently translated due to its cap-binding activity.
2024-08-07 | GSE243708 | GEO
Project description:A prominent hallmark of cancer is deregulated protein synthesis. It is well established that various translation initiation factors (eIFs) are either overexpressed or under-expressed in numerous types of cancer. Recent studies suggest that rather than representing an indirect consequence of neoplasia, imbalanced expression of eIFs significantly contributes to cellular transformation, tumor development, cancer cell survival, metastasis and tumor angiogenesis. Among them, eIF3 stands out as the largest complex composed of 12 subunits with a modular assembly, where aberrant expression of one subunit leads to partially functional subcomplexes. Here we took advantage of well-established knockdowns of subunits d, e and h of human eIF3, all implicated in cancer, and investigated their impact on differential gene expression translatome-wide by Ribo-Seq. We demonstrate that eIF3e and eIF3d knock-downs result in reduced translation efficiency of numerous components of the MAPK signaling pathway, a pathway often upregulated in cancer, and pathways preventing genotoxic stress. Concurrently, depletion of eIF3d increased translation of proteins associated with membrane organelles, whereas eIF3e depletion increased expression of numerous ribosomal proteins, implicating eIF3e in controlling the balanced production of mature ribosomes. Overall, our data illustrate that individual eIF3 subunits exert specific translational control over a broad range of cellular transcripts.
2024-04-25 | GSE216967 | GEO
Project description:Virus infection may shut off host protein synthesis in order to achieve the replicative advantage over host cells. It is well known that human pathogenic viruses, particularly the picornaviruses, can block host protein synthesis by cleavage or inhibition of eukaryotic initiation factors (eIFs). In this study we found a novel mechanism that microRNA (miRNA) is involved in viral pathogenesis. Infection of enteroviruses can disturb the expression of host miRNAs, in which miR-141 is up-regulated and inhibits host protein synthesis by post-transcriptional repression of the target gene eIF4E, a key element for cap-dependent translation of host proteins. Knockdown of miR-141 by a specific siRNA, antagomiR-141, could restore host eIF4E expression, delay the occurrence of cytopathic effect (CPE), and impair virus propagation. We demonstrated that EV71 infection could increase early growth response 1 (EGR1) expression which induced miR-141 causing the eIF4E suppression; while silencing of EGR1 attenuated virus production. Our results suggest that enterovirus infection causes the EGR1-mediated upregulation of host miR-141, further lead to the translational switch from cap-dependent to cap-independent protein synthesis in the host cells, an environmental beneficial for viral propagation. This novel mechanism may highlight a new approach for future development of antiviral therapy. Enteroviruses in the Picornaviridae family are important human pathogens which can cause fatal diseases, including cardiopulmonary failure, aseptic meningitis, paralysis, myocarditis, and encephalomyelitis. Virus infection may induce shutoff of host protein synthesis, particularly in picornavirus, whose protein translation is cap-independent. It is known that poliovirus 2A protease cleaves eIF4G, a scaffold component of mammalian cell translational complex, leading to the shut down of host protein synthesis. Nevertheless, the cleavage of eIF4G may not be sufficient for the complete shutoff of host protein synthesis. Previous studies showed that cleavage of polyA-binding protein (PABP) by viral protease 3C and dephosphorylation of the translational repressor, eIF4E binding protein 1 (4E-BP1), also contribute to this process. The cap-binding protein, eIF4E, is the most crucial factor in determining whether cap-dependent or -independent translation takes place. The mechanism by which viral infection modulates host cell protein synthesis through interfering eIF4E expression is not yet known. miRNAs are a newly discovered class of small non-protein-coding RNAs that may act via endogenous RNA interference. Our understanding of its role in the dynamic interplay between virus and host components is quite limited. Since both virus infection and miRNAs could hinder cellular protein synthesis, whether miRNAs are involved during virus infection in shutting off host protein synthesis is still unknown. To address this issue, we analyze the altered gene and microRNA expression after EV71 infection. ***This submission represents the mRNA expression component of the study only***
2011-01-03 | E-GEOD-15323 | biostudies-arrayexpress
Project description:Cellular responses to environmental stress are frequently mediated by RNA-binding proteins (RBPs). Here, we examined global RBP dynamics in Saccharomyces cerevisiae in response to glucose starvation and heat shock. Each stress induced rapid remodeling of the RNA-protein interactome, without corresponding changes in RBP abundance. Consistent with general translation shutdown, ribosomal proteins contacting the mRNA showed decreased RNA-association. Among translation components, RNA-association was most reduced for initiation factors involved in 40S scanning (eIF4A, eIF4B, and Ded1), indicating a common mechanism of translational repression. In unstressed cells, eIF4A, eIF4B, and Ded1 primarily targeted the 5′-ends of mRNAs. Following glucose withdrawal, 5’-binding was abolished within 30sec, explaining the rapid translation shutdown, but mRNAs remained stable. Heat shock induced progressive loss of 5’ RNA-binding by initiation factors over ~16min. Translation shutoff provoked selective 5′-degradation of mRNAs encoding translation-related factors, mediated by Xrn1. These results reveal mechanisms underlying translational control of gene expression during stress.
2020-06-08 | GSE148166 | GEO
Project description:A phosphorylation-regulated eIF3d translation switch mediates cellular adaptation to metabolic stress
| PRJNA664584 | ENA
Project description:Cellular responses to environmental stress are frequently mediated by RNA-binding proteins (RBPs). Here, we examined global RBP dynamics in Saccharomyces cerevisiae in response to glucose starvation and heat shock. Each stress induced rapid remodeling of the protein:RNA interactome, without corresponding changes in RBP abundance. Consistent with general translation shutdown, ribosomal proteins contacting the mRNA showed decreased RNA-association. Among translation components, RNA-association was most reduced for initiation factors involved in 40S scanning (eIF4A, eIF4B, and Ded1), indicating a common mechanism of translational repression. In unstressed cells, eIF4A, eIF4B, and Ded1 primarily targeted the 5′-ends of mRNAs. Following glucose withdrawal, mRNAs remained stable, but 5’-binding was abolished within 30sec, explaining the rapid translation shutdown. Heat shock induced progressive loss of 5’ RNA-binding by initiation factors over ~16min, and translation shutoff provoked 5′-degradation by Xrn1, selectively for mRNAs encoding translation-related factors. These results reveal mechanisms underlying translational control of gene expression during stress.
2020-10-13 | PXD019141 | Pride
Project description:Integrated Stress Response (ISR) is a homeostatic mechanism induced by endoplasmic reticulum (ER) stress. With acute/transient ER stress, decreased global protein synthesis and increased uORF mRNA translation are followed by translation normalization. Here, we report a dramatically different response during more physiologically relevant chronic ER stress. This unique ISR program is characterized by persistently elevated uORF mRNA translation and concurrent gene expression reprogramming, which permits simultaneous stress sensing and proteostasis. PERK-dependent switching from eIF4F/eIF2B- to eIF3D/GADD34-regulated translation initiation results in partial but not complete translation recovery, and together with transcriptional reprogramming, selectively bolsters expression of proteins with ER functions. Coordination of these transcriptional and translational changes prevents ER dysfunction and inhibits “foamy cell” development, thus establishing a molecular basis for understanding human diseases associated with ER dysfunction.
2018-01-05 | GSE90070 | GEO
Project description:Enterovirus 71 (EV71) infection causes a profound shutoff of cellular protein synthesis. Deep RNA-sequencing and ribosome profiling were employed to systematically analyze messenger RNA and ribosome-protected RNA in EV71-infected rhabdomyosarcoma cells at progressive time points following infection. The analysis characterized the dynamic transcriptional and translational landscapes of both the virus and host cells. The results indicated that reduced translation of cellular mRNAs played a key role in EV71-induced host shutoff rather than mRNA depletion. During the host shutoff, EV71 protein was preferably synthesized through both a translational advantage and abundant mRNA production. Moreover, a small number of cellular genes were resistant to the host shutoff through both transcriptional and translational regulation, including genes in mitogen-activated protein kinase (MAPK) signaling pathway that is important for EV71 replication. These results indicated selective cellular protein synthesis during EV71-induced host shutoff as a mechanism the virus utilizes to benefit its replication.
2018-05-03 | GSE103308 | GEO
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
2017-07-26 | GSE101865 | GEO