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EIF4A2 drives repression of translation at initiation by Ccr4-Not through purine-rich motifs in the 5’UTR.

ABSTRACT: Regulation of the mRNA life-cycle is central to gene expression control and determination of cell fate. miRNAs represent a critical mRNA regulatory mechanism, but despite decades of research, their mode of action is still not fully understood. Here we show eIF4A2 is a major effector of the repressive miRNA pathway functioning via the Ccr4-Not complex. We demonstrate that while DDX6 interacts with Ccr4-Not, its effects in the mechanism are not as pronounced. Through its interaction with the Ccr4-Not complex eIF4A2 represses mRNAs at translation initiation. We show evidence that native eIF4A2 has similar properties to chemically inhibited eIF4A1. We demonstrate that eIF4A2 exerts it repressive effect by binding purine-rich motifs which are enriched in the 5’UTR directly upstream of the AUG start codon. The data supports a model whereby purine motifs towards the 3’ end of the 5’UTR are associated with increased ribosome occupancy and possible uORF activation similar to that observed for mRNAs affected by inhibited eIF4A1.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Permanent Cell Line Cell

DISEASE(S): Disease Free

SUBMITTER: Kelly Hodge

LAB HEAD: Sara Rossana Zanivan

PROVIDER: PXD014764 | Pride | 2019-10-08

REPOSITORIES: Pride

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eIF4A2 drives repression of translation at initiation by Ccr4-Not through purine-rich motifs in the 5’UTR

Project description:Background: Regulation of the mRNA life cycle is central to gene expression control and determination of cell fate. miRNAs represent a critical mRNA regulatory mechanism, but despite decades of research, their mode of action is still not fully understood. Results: Here, we show that eIF4A2 is a major effector of the repressive miRNA pathway functioning via the Ccr4-Not complex. We demonstrate that while DDX6 interacts with Ccr4-Not, its effects in the mechanism are not as pronounced. Through its interaction with the Ccr4- Not complex, eIF4A2 represses mRNAs at translation initiation. We show evidence that native eIF4A2 has similar RNA-selectivity to chemically inhibited eIF4A1. eIF4A2 exerts its repressive effect by binding purine-rich motifs which are enriched in the 5’UTR of target mRNAs directly upstream of the AUG start codon. Conclusions: Our data support a model whereby purine motifs towards the 3’ end of the 5’UTR are associated with increased ribosome occupancy and possible uORF activation upon eIF4A2 binding.

2019-10-09 | GSE94690 | GEO

eIF4A2 drives repression of translation at initiation by Ccr4-Not through purine rich motifs in th 5'UTR

Project description:Here we show eIF4A2 is a major effector of the represive miRNA pathway functioning via the Ccr4_Not complex; through its interaction with the Ccr4-Not complex eIF4A2 represses mRNAs at translation initiation. We show evidence that native eIF4A2 has similar properties to chemically inhibited eIF4A1. eIF4A2 exerts its repressive effect by binding purine-rich motifs which are enriched in the 5'UTR directly upstream of the AUG codon.

2019-10-10 | PXD015772 | Pride

eIF4A1 unwinding activity is RNA sequence-specifically deployed through eIF4A1-multimerisation to facilitate translation of mRNAs with local repressive RNA structure

Project description:Oncogenic translational programmes are an emerging hallmark of cancer and often driven by dysregulation of signaling pathways including KRAS and mTORC that converge on the eukaryotic translation initiation (eIF) 4F complex. Altered eIF4F activity promotes translation of oncogene mRNAs that typically contain highly structured 5’UTRs rendering their translation strongly dependent on RNA unwinding by DEAD-box helicase eIF4A1 subunit of the eIF4F complex. In addition, eIF4A1 separately functions to load mRNA into the 43S pre-initiation complex (PIC), an essential step for the translation of cellular mRNA. While eIF4A1-dependent mRNAs have been widely investigated, it is still unclear if highly structured mRNAs recruit and activate eIF4A1 unwinding specifically. Here, we uncover that unwinding by eIF4A1 is activated in an RNA sequence-dependent manner in cells. Our data demonstrate that eIF4A1-dependent mRNAs contain specific RNA sequences, particularly enriched for polypurine-motifs, in their 5’UTR which recruit and specifically stimulate unwinding of local repressive RNA structure by eIF4A1 in an RNA sequence-dependent manner to facilitate translation. Mechanistically, we show that polypurine-rich sequences trigger the formation of RNA sequence-specific multimeric eIF4A1-complexes, assembled of catalytically distinct eIF4A1 subunits, the joint activity of which enhances RNA unwinding activity. Together with our structural data, we describe a model in which conformational changes within eIF4A1 and the RNA through the process of eIF4A1 multimerisation, lead to an optimal interaction of eIF4A1-unwinding subunits with the structured RNA region which enhances unwinding. Hence, we conclude that RNA sequences in addition to protein cofactors contribute to the regulation of cellular eIF4A1 function and promotion of translation of eIF4A1-unwinding dependent mRNAs.

2023-01-17 | PXD034343 | Pride

Transcriptomic and proteomic profiling of KEAP1 disrupted and sulforaphane treated human breast epithelial cells

Project description:Sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables, is a potent inhibitor of experimental mammary carcinogenesis and may be an effective, safe chemopreventive agent for use in humans. SFN acts in part on the Keap1/Nrf2 pathway to regulate a battery of cytoprotective genes. In this study transcriptomic and proteomic changes in the estrogen receptor negative, non tumorigenic human breast epithelial MCF10A cell line were analyzed following SFN treatment or KEAP1 knockdown with siRNA using microarray and stable isotopic labeling with amino acids in culture (SILAC), respectively. Changes in selected transcripts and proteins were confirmed by PCR and Western blot in MCF10A and MCF12A cells. There was strong correlation between the transcriptomic and proteomic responses in both the SFN treatment (R=0.679, P<0.05) and KEAP1 knockdown (R=0.853, P<0.05) experiments. Common pathways for SFN treatment and KEAP1 knockdown were xenobiotic metabolism and antioxidants, glutathione metabolism, carbohydrate metabolism and NADH/NADPH regeneration. Moreover, these pathways were most prominent in both the transcriptomic and proteomic analyses. The aldo-keto reductase family members, AKR1B10, AKR1C1, AKR1C2 and AKR1C3, as well as NQO1 and ALDH3A1, were highly upregulated at both the transcriptomic and proteomic level. Collectively, these studies served to identify potential biomarkers that can be used in clinical trials to investigate the initial pharmacodynamic action of SFN in the breast. MCF10A cells were treated with SFN or had KEAP1 knocked down by siRNA.

2011-04-22 | E-GEOD-28813 | biostudies-arrayexpress

Selective translation mechanism through two paralogs of eukaryotic initiation factor 4A

Project description:Eukaryotic initiation factor (eIF) 4A is a DEAD-box RNA-binding protein that plays a pivotal role in translation initiation. Although mammals have two eIF4A paralogs, eIF4A1 and eIF4A2, their redundancy has been long assumed because of high homology and their functional difference has been poorly understood. Here we show that eIF4A paralogs employ differential translation programs. Ribosome profiling of eIF4A1- and eIF4A2-knockout HEK293T cell lines revealed that translation efficiency changes were divergent across transcriptome and distinct group of mRNAs were regulated by each paralog. Our analysis indicates that eIF4A1 and eIF4A2 facilitate translation of specific mRNAs.

2019-10-26 | GSE126298 | GEO

ASB11 controls purinosome formation through PAICS ubiquitination

Project description:Purine act as building block for DNA and RNA, provide cellular energy and signaling, and can generate cofactors such as NADH and coenzyme A. Purine de novo synthesis pathway begins with amino acids, ribose 5-phosphate, CO2 and NH3 with 6 enzymes and 10 enzymatic steps to convert PRPP to IMP. In previous study, under purine-depleted or other stimuli the six enzymes will form dynamic and reversible complex called purinosome to enhance the pathway flux. However, the mechanism of purinosome formation is unknown. Phosphoribosyl aminoimidazole succinocarboxamide synthetase (PAICS), an enzyme involved in the step7 and 8 of purine biosynthesis. In our lab, we used interactome and ubiquiylome to identify PAICS, which is a substrate of ASB11. ASB11 is a substrate adaptor of cullin 5 ubiquitin ligase complex and is able to bind PAICS for ubiquitination. Here, we found that ASB11 could increase purinosome formation without any stimuli. This effect depends on ASB11 E3 function, which can ubiquitinate PAICS on K74 site. We generate K74R mutation of PAICS so that ASB11 couldn’t ubiquitinate it. Interestingly, this mutant reduces the formation of purinosomes under purine-depleted and other stressed conditions. After further research, we found ASB11 expression level will increase under some specific conditions. Moreover, we analyzed TCGA database and found that the expression of ASB11 in melanoma cell is higher than normal cell. Consistent with our finding, melanoma cell has partially formed purinosome under basal condition because of the higher expression of ASB11. We guess that ASB11 may plays an important role in cancer cell.

2023-10-06 | PXD025298 | Pride

Dynamic profiling of the protein life cycle in response to pathogens (protein)

Project description:Protein expression is regulated by production and degradation of mRNAs and proteins, but their specific relationships remain unknown. We combine measurements of protein production and degradation and mRNA dynamics to build a quantitative genomic model of the differential regulation of gene expression in LPS stimulated mouse dendritic cells. Changes in mRNA abundance play a dominant role in determining most dynamic fold changes in protein levels. Conversely, the preexisting proteome of proteins performing basic cellular functions is remodeled primarily through changes in protein production or degradation, accounting for over half of the absolute change in protein molecules in the cell. Thus, the proteome is regulated by transcriptional induction of novel cellular functions and remodeling of preexisting functions through the protein life cycle. Mouse primary dendritic cells were treated with LPS or mock stimulus and profiled over a 12-hour time course. Cells were grown in M-labeled SILAC media, which was replaced with H-labeled SILAC media at time 0. Aliquots were taken at 0, 0.5, 1, 2, 3, 4, 5, 6, 9, and 12 hours post-stimulation and added to equal volumes of a master mix of unlabeled (L) cells for the purpose of normalization. RNA-Seq was performed at 0, 1, 2, 4, 6, 9, and 12 hours post-stimulation.

2015-03-06 | E-GEOD-59792 | biostudies-arrayexpress

Transcriptional profiling of mouse small intestinal tissue with Eif4a1/4a2 mutation

Project description:Small intestinal tissue was collected for RNAseq analysis from mice with short term Apc inactivation or Apc inactivation with Kras mutation, in the presence or absence of Eif4a1 or Eif4a2 inactivaton.

2023-08-31 | GSE240283 | GEO

Saccharomyces cerevisiae mutant strain with R1158 strain background: Fold change after doxycycline treatment

Project description:To understand the extent that Heat shock protein 90 (Hsp90) regulated its target proteins at the transcription level, transcriptomic change was profiled in yeast cells upon Hsp90 compromising. We genetically modified the R1158 strain (resulting genotype of mutant strain: TETp-HSC82 hsp82Δ arg4Δ lys5Δ car2Δ::URA3) and then reduced the Hsp90 amount with doxycycline treatment. Fold change of mRNA from untreated to treated cells indicated the transcriptomic change. Totally, we identified 1104 genes mis-regulated with a fold change of no less than 1.5 (P <0.05) upon Hsp90 compromising. Two-condition experiment, treated vs. untreated cells. Biological duplicates, independently grown and harvested. Technical triplicates for RNA isolation.

2014-03-26 | E-GEOD-56186 | biostudies-arrayexpress

RNA helicase EIF4A1-mediated translation is essential for the GC response

Project description:EIF4A1 and cofactors EIF4B and EIF4H have been well characterised in cancers, including B cell malignancies, for their ability to promote the translation of oncogenes with structured 5’ untranslated regions. However, very little is known of their roles in non-malignant cells. Using mouse models to delete Eif4a1, Eif4b or Eif4h in B cells we show that EIF4A1, but not EIF4B or EIF4H, is essential for B cell development and the germinal centre response. Following B cell activation in vitro, EIF4A1 facilitates an increased rate of protein synthesis, MYC expression and expression of cell cycle regulators. However, EIF4A1-deficient cells remain viable whereas inhibition of EIF4A1 and EIF4A2 by Hippuristanol treatment induces cell death.

2023-11-09 | PXD046710 | Pride

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