scholarly journals Selective Translation Complex Profiling Reveals Staged Initiation and Co-translational Assembly of Initiation Factor Complexes

2019 ◽  
Author(s):  
Susan Wagner ◽  
Anna Herrmannová ◽  
Vladislava Hronová ◽  
Neelam Sen ◽  
Ross D. Hannan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Translational Control ◽  
Mammalian Cells ◽  
Regulation Of Gene Expression ◽  
Ribosome Profiling ◽  
Initiation Factor ◽  
Start Codon ◽  
Codon Recognition ◽  
Initiation Phase ◽  
Gene Expression Studies

SUMMARYTranslational control targeting mainly the initiation phase is central to the regulation of gene expression. Understanding all of its aspects requires substantial technological advancements. Here we modified yeast Translational Complex Profile sequencing (TCP-seq), related to ribosome profiling, and adopted it for mammalian cells. Human TCP-seq, capable of capturing footprints of 40S subunits (40Ses) in addition to 80S ribosomes (80Ses), revealed that mammalian and yeast 40Ses distribute similarly across 5’UTRs indicating considerable evolutionary conservation. We further developed a variation called Selective TCP-seq (Sel-TCP-seq) enabling selection for 40Ses and 80Ses associated with an immuno-targeted factor in yeast and human. Sel-TCP-seq demonstrated that eIF2 and eIF3 travel along 5’UTRs with scanning 40Ses to successively dissociate upon start codon recognition. Manifesting the Sel-TCP-seq versatility for gene expression studies, we also identified four initiating 48S conformational intermediates, provided novel insights into ATF4 and GCN4 mRNA translational control, and demonstrated co-translational assembly of initiation factor complexes.

scholarly journals Regulation of eIF4E Guides a Unique Translational Program to Steer Erythroid Maturation

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 156-156
Author(s):  
Craig M Forester ◽  
Gun Woo-Byeon ◽  
Juan Oses-Prieto ◽  
Al Burlingame ◽  
Maria Barna ◽  
...  
Keyword(s):  
Gene Expression ◽  
Translational Control ◽  
Conflicts Of Interest ◽  
Regulation Of Gene Expression ◽  
Erythroid Differentiation ◽  
Initiation Factor ◽  
Specific Gene ◽  
Erythroid Precursors ◽  
Erythroid Maturation

Erythropoiesis is an intricately orchestrated process responsible for rapidly responding to an array of signaling cues to direct cell fates. While gene expression during erythropoiesis has mainly been studied at the transcription level, regulation of gene expression at the level of translation is still poorly understood. As translational control is one of the fastest steps to regulate protein abundance in the cell, we hypothesize that this mechanism plays an important role to rapidly control protein levels in response to extracellular cues during erythroid differentiation. However, outstanding questions remain on how translational control regulates specific gene programs in early erythroid states including 1.) how mRNA are selected for translation in normal erythropoiesis and 2.) how components of the translational machinery are regulated by upstream signaling pathways to orchestrate the translational landscape. In addressing these questions, we have nuncovered a dynamic interplay between Eukaryotic Initiation Factor 4E (eIF4E), the major mRNA cap binding protein that controls translation initiation and its repressor protein, 4EBP1 in erythropoiesis. Specifically, using in vivo phospho-flow cytometry analysis of the eIF4E-4EBP1 axis, eIF4E activity is high in early erythroid phases and is repressed by 4EBP1 in order to allow erythroid maturation. Surprisingly, high eIF4E activity in early erythroid precursors occurs without an increase in global protein synthesis. Utilizing a model of CD34+ human cord blood cells (HUDEP-2), we show that constitutive overexpression of eIF4E impaired erythropoietic maturation. To capture the specific proteins potentially regulated by eIF4E activity during erythropoiesis, we performed quantitative TMT mass spectrometry during HUDEP-2 erythroid differentiation. Our results revealed that eIF4E controls a specific key network of genes necessary for maintenance of early erythroid precursors. By analyzing the 5' untranslated region (5'UTR) of the eIF4E-dependent mRNA network, we identify a highly conserved, CT-rich motif which is required for these mRNAs to be more efficiently translated with increasing eIF4E levels. These results demonstrate wide-spread translational control of CT-rich mRNAs by eIF4E during early erythropoiesis. We are currently employing DMS-MaPseq to understand whether these motifs are also part of structured RNA elements that confer sensitivity to eIF4E levels. We have further extended these findings to a novel transgenic mouse model we have developed that allows in vivo assessment of increased eIF4E temporally at concise phases of erythroid maturation. Understanding this balance of eIF4E activity provides a novel insight into how of translational control dictates gene expression to determine phases of maturation in a crucial differentiation process. Disclosures No relevant conflicts of interest to declare.

scholarly journals The DAZL and PABP families: RNA-binding proteins with interrelated roles in translational control in oocytes

Reproduction ◽  
2009 ◽  
Vol 137 (4) ◽  
pp. 595-617 ◽  
Author(s):  
Matthew Brook ◽  
Joel W S Smith ◽  
Nicola K Gray
Keyword(s):  
Gene Expression ◽  
Germ Cells ◽  
Translational Control ◽  
Translational Regulation ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Regulation Of Gene Expression ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor

Gametogenesis is a highly complex process that requires the exquisite temporal, spatial and amplitudinal regulation of gene expression at multiple levels. Translational regulation is important in a wide variety of cell types but may be even more prevalent in germ cells, where periods of transcriptional quiescence necessitate the use of post-transcriptional mechanisms to effect changes in gene expression. Consistent with this, studies in multiple animal models have revealed an essential role for mRNA translation in the establishment and maintenance of reproductive competence. While studies in humans are less advanced, emerging evidence suggests that translational regulation plays a similarly important role in human germ cells and fertility. This review highlights specific mechanisms of translational regulation that play critical roles in oogenesis by activating subsets of mRNAs. These mRNAs are activated in a strictly determined temporal manner via elements located within their 3′UTR, which serve as binding sites fortrans-acting factors. While we concentrate on oogenesis, these regulatory events also play important roles during spermatogenesis. In particular, we focus on the deleted in azoospermia-like (DAZL) family of proteins, recently implicated in the translational control of specific mRNAs in germ cells; their relationship with the general translation initiation factor poly(A)-binding protein (PABP) and the process of cytoplasmic mRNA polyadenylation.

scholarly journals eIF3 and Its mRNA-Entry-Channel Arm Contribute to the Recruitment of mRNAs With Long 5′-Untranslated Regions

2022 ◽  
Vol 8 ◽  
Author(s):  
Andrei Stanciu ◽  
Juncheng Luo ◽  
Lucy Funes ◽  
Shanya Galbokke Hewage ◽  
Colin Echeverría Aitken
Keyword(s):  
Translation Initiation ◽  
Ribosome Profiling ◽  
Yeast Cells ◽  
Initiation Factor ◽  
Start Codon ◽  
Untranslated Regions ◽  
Initiation Factors ◽  
Codon Recognition ◽  
Entire Complex ◽  
The Individual

Translation initiation in eukaryotes is a multi-step pathway and the most regulated phase of translation. Eukaryotic initiation factor 3 (eIF3) is the largest and most complex of the translation initiation factors, and it contributes to events throughout the initiation pathway. In particular, eIF3 appears to play critical roles in mRNA recruitment. More recently, eIF3 has been implicated in driving the selective translation of specific classes of mRNAs. However, unraveling the mechanism of these diverse contributions—and disentangling the roles of the individual subunits of the eIF3 complex—remains challenging. We employed ribosome profiling of budding yeast cells expressing two distinct mutations targeting the eIF3 complex. These mutations either disrupt the entire complex or subunits positioned near the mRNA-entry channel of the ribosome and which appear to relocate during or in response to mRNA binding and start-codon recognition. Disruption of either the entire eIF3 complex or specific targeting of these subunits affects mRNAs with long 5′-untranslated regions and whose translation is more dependent on eIF4A, eIF4B, and Ded1 but less dependent on eIF4G, eIF4E, and PABP. Disruption of the entire eIF3 complex further affects mRNAs involved in mitochondrial processes and with structured 5′-untranslated regions. Comparison of the suite of mRNAs most sensitive to both mutations with those uniquely sensitive to disruption of the entire complex sheds new light on the specific roles of individual subunits of the eIF3 complex.

scholarly journals The Role of Translation Initiation Regulation in Haematopoiesis

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Godfrey Grech ◽  
Marieke von Lindern
Keyword(s):  
Gene Expression ◽  
Translation Initiation ◽  
Translational Control ◽  
Molecular Mechanisms ◽  
Rna Binding ◽  
Regulation Of Gene Expression ◽  
Mrna Translation ◽  
Translation Control ◽  
Haematological Disorders

Organisation of RNAs into functional subgroups that are translated in response to extrinsic and intrinsic factors underlines a relatively unexplored gene expression modulation that drives cell fate in the same manner as regulation of the transcriptome by transcription factors. Recent studies on the molecular mechanisms of inflammatory responses and haematological disorders indicate clearly that the regulation of mRNA translation at the level of translation initiation, mRNA stability, and protein isoform synthesis is implicated in the tight regulation of gene expression. This paper outlines how these posttranscriptional control mechanisms, including control at the level of translation initiation factors and the role of RNA binding proteins, affect hematopoiesis. The clinical relevance of these mechanisms in haematological disorders indicates clearly the potential therapeutic implications and the need of molecular tools that allow measurement at the level of translational control. Although the importance of miRNAs in translation control is well recognised and studied extensively, this paper will exclude detailed account of this level of control.

4E-BP1 and S6K1: translational integration sites for nutritional and hormonal information in muscle

2000 ◽  
Vol 279 (4) ◽  
pp. E715-E729 ◽  
Author(s):  
O. Jameel Shah ◽  
Joshua C. Anthony ◽  
Scot R. Kimball ◽  
Leonard S. Jefferson
Keyword(s):  
Translational Control ◽  
Mrna Translation ◽  
Cellular Protein ◽  
Initiation Factor ◽  
Translational Repressor ◽  
Initiation Factors ◽  
Initiation Phase ◽  
Eukaryotic Initiation Factor 4E ◽  
Integration Sites ◽  
A Site

Maintenance of cellular protein stores in skeletal muscle depends on a tightly regulated synthesis-degradation equilibrium that is conditionally modulated under an extensive range of physiological and pathophysiological circumstances. Recent studies have established the initiation phase of mRNA translation as a pivotal site of regulation for global rates of protein synthesis, as well as a site through which the synthesis of specific proteins is controlled. The protein synthetic pathway is exquisitely sensitive to the availability of hormones and nutrients and employs a comprehensive integrative strategy to interpret the information provided by hormonal and nutritional cues. The translational repressor, eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and the 70-kDa ribosomal protein S6 kinase (S6K1) have emerged as important components of this strategy, and together they coordinate the behavior of both eukaryotic initiation factors and the ribosome. This review discusses the role of 4E-BP1 and S6K1 in translational control and outlines the mechanisms through which hormones and nutrients effect changes in mRNA translation through the influence of these translational effectors.

scholarly journals Ribosome profiling reveals a functional role for autophagy in mRNA translational control

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Juliet Goldsmith ◽  
Timothy Marsh ◽  
Saurabh Asthana ◽  
Andrew M. Leidal ◽  
Deepthisri Suresh ◽  
...  
Keyword(s):  
Dna Damage ◽  
Protein Synthesis ◽  
Translational Control ◽  
Mammalian Cells ◽  
Dna Damage Repair ◽  
Protein Translation ◽  
Ribosome Profiling ◽  
Parp Inhibition ◽  
Genetic Ablation ◽  
Damage Repair

AbstractAutophagy promotes protein degradation, and therefore has been proposed to maintain amino acid pools to sustain protein synthesis during metabolic stress. To date, how autophagy influences the protein synthesis landscape in mammalian cells remains unclear. Here, we utilize ribosome profiling to delineate the effects of genetic ablation of the autophagy regulator, ATG12, on translational control. In mammalian cells, genetic loss of autophagy does not impact global rates of cap dependent translation, even under starvation conditions. Instead, autophagy supports the translation of a subset of mRNAs enriched for cell cycle control and DNA damage repair. In particular, we demonstrate that autophagy enables the translation of the DNA damage repair protein BRCA2, which is functionally required to attenuate DNA damage and promote cell survival in response to PARP inhibition. Overall, our findings illuminate that autophagy impacts protein translation and shapes the protein landscape.

scholarly journals Hepatic Gene Expression Changes in Hypothyroid Juvenile Mice: Characterization of a Novel Negative Thyroid-Responsive Element

Endocrinology ◽  
2007 ◽  
Vol 148 (8) ◽  
pp. 3932-3940 ◽  
Author(s):  
Hongyan Dong ◽  
Carole L. Yauk ◽  
Andrew Williams ◽  
Alice Lee ◽  
George R. Douglas ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Microarrays ◽  
Molecular Mechanisms ◽  
Regulation Of Gene Expression ◽  
Transient Gene Expression ◽  
Early Response ◽  
Response Element ◽  
Gene Expression Studies ◽  
Maternal Thyroid ◽  
Responsive Element

The molecular mechanisms involved in the response of developing mice to disruptions in maternal thyroid hormone (TH) homeostasis are poorly characterized. We used DNA microarrays to examine a broad spectrum of genes from the livers of mice rendered hypothyroid by treating pregnant mice from gestational d 13 to postnatal d 15 with 6-propyl-2-thiouracil in drinking water. Twenty-four individuals (one male and one female pup from six litters of control or 6-propyl-2-thiouracil treatment groups, respectively) were profiled using Agilent oligonucleotide microarrays. MAANOVA identified 96 differentially expressed genes (false discovery rate adjusted P < 0.1 and fold change > 2 in at least one gender). Of these, 72 genes encode proteins of known function, 15 of which had previously been identified as regulated by TH. Pathway analysis revealed these genes are involved in metabolism, development, cell proliferation, apoptosis, and signal transduction. An immediate-early response gene, Nr4a1 (nuclear receptor subfamily 4, group A, member 1), was up-regulated by 3-fold in hypothyroid juvenile mouse liver; treatment of HepG2 cells with T3 resulted in down-regulation of Nr4a1. A potential thyroid response element −1218 to −1188 bp upstream of the promoter region of Nr4a1 was identified and demonstrated to bind TH receptor (TR)-α and TRβ. Point mutation or deletion of the sequence containing the potential Nr4a1-thyroid response element in transient gene expression studies resulted in both higher basal expression and loss of T3 regulatory capacity, suggesting that this site is responsible for the negative regulation of gene expression by TR and TH.

Upregulation of eIF4E in Nucleophosmin 1 (NPM1) Haploinsufficient Cells Alters CCAAT Enhancer Binding Protein Alpha (C/EBPα) Activity: Implications for MDS and AML

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2432-2432
Author(s):  
Nirmalee Abayasekara ◽  
Michelle Levine ◽  
Niccolo Bolli ◽  
Hong Sun ◽  
Matthew Silver ◽  
...  
Keyword(s):  
Gene Expression ◽  
Translation Initiation ◽  
Translational Control ◽  
Conflicts Of Interest ◽  
Mrna Translation ◽  
Dominant Negative ◽  
Full Length ◽  
Initiation Factor ◽  
Specific Gene ◽  
Specific Gene Expression

Abstract Abstract 2432 NPM1, is a highly conserved, ubiquitous nucleolar phosphoprotein that belongs to the nucleoplasmin family of nuclear chaperones. NPM1−/− mice die at mid-gestation (E11.5) from anemia, underscoring the gene's role in embryonic development. NPM1 is one of the most frequently mutated genes in AML. Mutations in NPM1 are found in 50% of normal karyotype AML patients, and mutant NPM1 (NPMc+) is aberrantly located in the cytoplasm of leukemic blasts in about 35% of all AML patients. Furthermore, NPM1 maps to a region on chromosome 5q that is the target of deletions in both de novo and therapy-associated human MDS. NPM1 thus acts as a haploinsufficient tumor suppressor in the hematological compartment, although the mechanism of its contribution to dysmyelopoiesis remains unknown. NPM-1+/− mice develop a hematological syndrome similar to that observed in human MDS, and develop AML over time. The NPM1 deficient model therefore provides a platform to interrogate the molecular basis of MDS. We identified nucleophosmin (NPM1) in a screen for protein binding partners of C/EBPα. C/EBPα is a single exon gene, but is expressed as two isoforms that arise by alternate translation start sites to yield a full length C/EBPα p42 and a truncated dominant negative C/EBPα p30 isoform. Translational control of isoform expression is orchestrated by a conserved upstream open reading frame (uORF) in the 5' untranslated region (5'UTR) and modulated by the translation initiation factors eIF4E and eIF2. We generated factor-dependent myeloid cell lines from the bone marrow of Npm1+/+ and Npm1+/− mice. These lines are IL-3-dependent and inducible toward neutrophil maturation with GM-CSF and/ or all- trans retinoic acid (ATRA). Neutrophils derived from MNPM1+/− cells display defective neutrophil-specific gene expression, including a cassette of C/EBPα-dependent genes. These observations led us to postulate that myeloid abnormalities in NPM1 deficiency reflect an aberrant NPM1-C/EBPα axis. We show that NPM1 haploinsufficiency upregulates eIF4E (eukaryotic initiation factor 4E) (but not eIF2), which binds the mRNA-Cap (m7-GTP) as part of the mRNA translation initiation complex, eIF4F. Increased eIF4E is observed in about 30% of all malignancies. Initial increased eIF4E levels in MNPM+/− cells likely reflect transcriptional activation by the oncoprotein c-Myc, protein levels of which are also elevated in MNPM1+/− cells. We propose that increased eIF4E then induces increased C/EBPαp30 translation. C/EBPαp30 is a dominant negative inhibitor of full length C/EBPαp42 activity and disrupts normal neutrophil development. Furthermore, we demonstrate that C/EBPαp30 but not C/EBPαp42, activates the eIF4E promoter. We propose a positive feedback loop, wherein increased C/EBPαp30 induced by eIF4E further increases the expression of eIF4E. Our data suggest that NPM1 deficiency modulates neutrophil-specific gene expression by altering C/EBPα. We propose an aberrant feed-forward mechanism that increases levels of both eIF4E and C/EBPαp30 and likely contributes to MDS associated with NPM1 deficiency. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Cell type-specific control of protein synthesis and proliferation by FGF-dependent signaling to the translation repressor 4E-BP

2016 ◽  
Vol 113 (27) ◽  
pp. 7545-7550 ◽  
Author(s):  
Rachel Ruoff ◽  
Olga Katsara ◽  
Victoria Kolupaeva
Keyword(s):  
Protein Synthesis ◽  
Translational Control ◽  
Bone Development ◽  
Binding Protein ◽  
Initiation Factor ◽  
Start Codon ◽  
Dependent Manner ◽  
Fgf Signaling ◽  
Cell Type

Regulation of protein synthesis plays a vital role in posttranscriptional modulation of gene expression. Translational control most commonly targets the initiation of protein synthesis: loading 40S ribosome complexes onto mRNA and AUG start codon recognition. This step is initiated by eukaryotic initiation factor 4E (eIF4E) (the m7GTP cap-binding protein), whose binding to eIF4G (a scaffolding subunit) and eIF4A (an ATP-dependent RNA helicase) leads to assembly of active eIF4F complex. The ability of eIF4E to recognize the cap is prevented by its binding to eIF4E binding protein (4E-BP), which thereby inhibits cap-dependent translation by sequestering eIF4E. The 4E-BP activity is, in turn, inhibited by mTORC1 [mTOR (the mechanistic target of rapamycin) complex 1] mediated phosphorylation. Here, we define a previously unidentified mechanism of mTOR-independent 4E-BP1 regulation that is used by chondrocytes upon FGF signaling. Chondrocytes are responsible for the formation of the skeleton long bones. Unlike the majority of cell types where FGF signaling triggers proliferation, chondrocytes respond to FGF with inhibition. We establish that FGF specifically suppresses protein synthesis in chondrocytes, but not in any other cells of mesenchymal origin. Furthermore, 4E-BP1 repressor activity is necessary not only for suppression of protein synthesis, but also for FGF-induced cell-cycle arrest. Importantly, FGF-induced changes in the 4E-BP1 activity observed in cell culture are likewise detected in vivo and reflect the action of FGF signaling on downstream targets during bone development. Thus, our findings demonstrate that FGF signaling differentially impacts protein synthesis through either stimulation or repression, in a cell-type–dependent manner, with 4E-BP1 being a key player.

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