Regulation of eIF4E Guides a Unique Translational Program to Steer 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.

Download Full-text

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

Blood ◽

10.1182/blood.v118.21.2432.2432 ◽

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.

Download Full-text

Cohesin-dependent regulation of gene expression during differentiation is lost in cohesin-mutated myeloid malignancies

Blood ◽

10.1182/blood.2019001553 ◽

2019 ◽

Vol 134 (24) ◽

pp. 2195-2208 ◽

Cited By ~ 9

Author(s):

Daniel Sasca ◽

Haiyang Yun ◽

George Giotopoulos ◽

Jakub Szybinski ◽

Theo Evan ◽

...

Keyword(s):

Gene Expression ◽

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Potential Role ◽

Regulation Of Gene Expression ◽

Specific Gene ◽

Myeloid Malignancy ◽

Erythroid Maturation ◽

Acute Myeloid

Cohesin mutations are common in myeloid malignancy. Sasca et al elucidate the potential role of cohesin loss in myelodysplastic syndrome and acute myeloid leukemia (MDS/AML). They demonstrate that cohesin binding is critical for erythroid-specific gene expression and that reduction in cohesin impairs terminal erythroid maturation and promotes myeloid malignancy.

Download Full-text

OncogenicGata1causes stage-specific megakaryocyte differentiation delay

10.1101/791079 ◽

2019 ◽

Author(s):

Gaëtan Juban ◽

Nathalie Sakakini ◽

Hedia Chagraoui ◽

Qian Cheng ◽

Kelly Soady ◽

...

Keyword(s):

Gene Expression ◽

Es Cells ◽

Erythroid Differentiation ◽

Detailed Examination ◽

S Phase ◽

Myeloproliferative Disorder ◽

Specific Gene ◽

Specific Stage

AbstractThe megakaryocyte/erythroid Transient Myeloproliferative Disorder (TMD) in newborns with Down Syndrome (DS) occurs when N-terminal truncating mutations of the hemopoietic transcription factor GATA1, that produce GATA1short protein (GATA1s), are acquired early in development. Prior work has shown that murine GATA1s, by itself, causes a transient yolk sac myeloproliferative disorder. However, it is unclear where in the hemopoietic cellular hierarchy GATA1s exerts its effects to produce this myeloproliferative state. Here, through a detailed examination of hemopoiesis from murine GATA1s ES cells and GATA1s embryos we define defects in erythroid and megakaryocytic differentiation that occur relatively in hemopoiesis. GATA1s causes an arrest late in erythroid differentiationin vivo, and even more profoundly in ES-cell derived cultures, with a marked reduction of Ter-119 cells and reduced erythroid gene expression. In megakaryopoiesis, GATA1s causes a differentiation delay at a specific stage, with accumulation of immature, kit-expressing CD41himegakaryocytic cells. In this specific megakaryocytic compartment, there are increased numbers of GATA1s cells in S-phase of cell cycle and reduced number of apoptotic cells compared to GATA1 cells in the same cell compartment. There is also a delay in maturation of these immature GATA1s megakaryocytic lineage cells compared to GATA1 cells at the same stage of differentiation. Finally, even when GATA1s megakaryocytic cells mature, they mature aberrantly with altered megakaryocyte-specific gene expression and activity of the mature megakaryocyte enzyme, acetylcholinesterase. These studies pinpoint the hemopoietic compartment where GATA1s megakaryocyte myeloproliferation occurs, defining where molecular studies should now be focussed to understand the oncogenic action of GATA1s.Scientific CategoryHaematopoiesis and Stem CellsKey PointsGATA1s-induced stage-specific differentiation delay increases immature megakaryocytesin vivoandin vitro, during development.Differentiation delay is associated with increased numbers of cells in S-phase and reduced apoptosis.

Download Full-text

Expression Of Mutant Spliceosomal Protein SF3B1 Results In Dysregulated Hematopoietic Maturation

Blood ◽

10.1182/blood.v122.21.2773.2773 ◽

2013 ◽

Vol 122 (21) ◽

pp. 2773-2773

Author(s):

Alexander C. Minella ◽

Oscar Ramirez ◽

Yanfei Xu ◽

Tushar Murthy ◽

Xiaodong Yang ◽

...

Keyword(s):

Molecular Mechanisms ◽

Conflicts Of Interest ◽

Erythroid Differentiation ◽

Retroviral Vectors ◽

Peptide Sequence ◽

Causative Role ◽

Wild Type ◽

Erythroid Maturation

Abstract Whole genome sequencing has recently revealed the prevalence of mutations in proteins directing splicing of RNA in up to half of the patients with Myelodysplastic Syndrome (MDS). Mutations in the protein SF3B1 are particularly common in MDS patients with the phenotypic abnormality termed ring sideroblasts (dysplastic erythroid precursors with perinculear rings formed by iron-laden mitochondria). The most common SF3B1 mutation in MDS patients results in a change from lysine to glutamic acid at amino acid position 700 (K700E). Given that splicing of RNA is a ubiquitous phenomenon, it is unclear how these mutations result in clonal proliferation and dysplastic hematopoiesis; two hallmark features of MDS. Furthermore, direct experimental evidence demonstrating a causative role for SF3B1 mutations in MDS-related phenotypes is lacking. To better understand how mutations of spliceosomal proteins contribute to MDS pathogenesis, we sought to define how expression of mutant SF3B1 changes erythroid maturation in vitro and in vivo. Native SF3B1 cDNA constructs are not amenable to bacterial propagation due to toxicity of its HEAT-domain repeats. We overcame this problem by codon optimization (changing the DNA sequence while preserving the native peptide sequence). Human cord blood derived CD34+ cells were transduced with retroviral vectors to express either the wild-type or K700E mutant of SF3B1. After a week of expansion in cytokines (IL-3, SCF and IL6), cells were induced to erythroid differentiation by addition of erythropoietin (EPO) and analyzed for surface markers of erythroid differentiation (CD 71, CD117, CD105, CD45 and CD235A) at regular intervals. K700E mutant expressing cells were found to have significantly reduced expression of CD105 when compared to wild-type SF3B1-expressing cells (average 50% recuction, n =8). CD105 or endoglin is a TGF-beta receptor accessory receptor expressed at high levels during intermediate stages of erythroid maturation. A more modest reduction of CD71 expression was also noted in K700E-SF3B1 cells. MDS bone marrow is known to express low levels of both CD105 and CD71 making our results clinically relevant. To further characterize how mutant SF3B1 may cause dysplastic hematopoiesis, we studied transduced and transplanted murine progenitor cells in vivo and in colony forming assays. Murine data demonstrate significantly reduced K700E-transduced hematopoietic progenitors (as defined by flow-cytometry) in vivo and impaired erythroid colony formation in vitro. Together, our results suggest that enforced expression of K700E-SF3B1 induces aberrant erythroid maturation and impairs homeostasis of hematopoietic precursor cells. Thus, we provide direct evidence that MDS-associated SF3B1 mutations perturb normal hematopoiesis and offer rationale for using our complementary experimental approach as a platform for elucidating the molecular mechanisms through which mutations in RNA splicing factors promote hematologic disease. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

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

10.1101/806125 ◽

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.

Download Full-text

A spatiotemporal translatome of mouse tissue development

10.1101/2020.04.14.041079 ◽

2020 ◽

Author(s):

Hongwei Wang ◽

Yan Wang ◽

Jiaqi Yang ◽

Nan Tang ◽

Huihui Li ◽

...

Keyword(s):

Gene Expression ◽

Translational Control ◽

Translational Regulation ◽

Regulation Of Gene Expression ◽

Open Reading Frames ◽

Mouse Tissue ◽

Specific Gene ◽

Translational Efficiency ◽

Tissue Development ◽

Mouse Tissues

AbstractThe precise regulation of gene expression in mammalian tissues during development results in their functional specification. Although previous transcriptomic and proteomic analyses have provided great biological insights into tissue-specific gene expression and the physiological relevance of these tissues in development, our understanding of translational regulation in developing tissues is lacking. In this study, we performed a spatiotemporally resolved translatome analysis of six mouse tissues at the embryonic and adult stages to quantify the effects of translational regulation and identify new translational components. We quantified the spatial and temporal divergences of gene expression and detected specific changes in gene expression and pathways underlying these divergences. We further showed that dynamic translational control can be achieved by modulating the translational efficiency, which resulted in the enhancement of tissue specificity during development. We also discovered thousands of actively translated upstream open reading frames (ORFs) that exhibited spatiotemporal patterns and demonstrated their regulatory roles in translational regulation. Furthermore, we identified known and novel micropeptides encoded by small ORFs from long noncoding RNAs that are functionally relevant to tissue development. Our data and analyses facilitate a better understanding of the complexity of translational regulation across tissue and developmental spectra and serve as a useful resource of the mouse translatome.

Download Full-text

Acetylation-Dependent Interaction of GATA-1 with the Potential Mitotic “Bookmarking” Protein Brd3.

Blood ◽

10.1182/blood.v116.21.2598.2598 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2598-2598

Author(s):

Janine M Lamonica ◽

Stephan Kadauke ◽

Wulan Deng ◽

Gerd Blobel

Keyword(s):

Gene Expression ◽

Conflicts Of Interest ◽

Memory Function ◽

Great Majority ◽

Underlying Mechanism ◽

Regulatory Elements ◽

Specific Gene ◽

Dependent Manner

Abstract Abstract 2598 Acetylation of the transcription factor GATA-1 facilitates its ability to drive erythroid differentiation by enhancing its association with in vivo target sites. However, the underlying mechanism through which GATA-1 acetylation functions has remained elusive. To test whether GATA-1 acetylation serves to recruit essential cofactors, we performed a peptide affinity screen and identified Brd3 as an acetylated GATA-1 interacting partner. Brd3 belongs to the BET protein family that also includes Brd2, Brd4, and Brdt, and is characterized by tandem bromodomains (BD1 and BD2) and an extraterminal (ET) domain. We show that Brd3 and GATA-1 physically interact in an acetylation-dependent manner in vitro and in vivo. Mapping studies revealed that the interaction depends on BD1 of Brd3 and one of the two major acetylation sites that resides near the C terminal zinc finger of GATA-1. By ChIP-seq and ChIP-qPCR, endogenous Brd3 is recruited to virtually all GATA-1-occupied regulatory elements in erythroid cells, including both GATA-1activated and repressed genes. Although Brd3 has been reported to associate with acetylated histones along the entire length of transcribed genes, we found that Brd3 recruitment correlates poorly with histone acetylation along gene bodies. In agreement with our biochemical data, an intact BD1 is essential for the in vivo recruitment of Brd3 to GATA-1-occupied elements, further demonstrating that acetylation of GATA-1 is essential for Brd3 association in vivo. Notably, a pharmacological compound that targets acetyl lysine binding sites in BD1 and BD2 disrupts the Brd3/GATA-1 interaction in vitro, diminishes Brd3 and GATA-1 association at key erythroid genes in vivo, and impairs GATA-1 target gene expression and erythroid maturation. In concert, these findings suggest a mechanism by which the first bromodomain of Brd3 recognizes acetyl-lysines on GATA-1 to facilitate GATA-1 chromatin occupancy. These studies raise an interesting question: In contrast to the great majority of transcription factors, BET family proteins bind to chromatin during mitosis and might serve an epigenetic memory function to properly reactivate gene transcription upon exit of mitosis. We are currently investigating whether Brd3 functions by bookmarking GATA-1-bound sites throughout mitosis to aid in transcriptional memory and stability of lineage specific gene expression. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Role of ZBP-89 in human globin gene regulation and erythroid differentiation

Blood ◽

10.1182/blood-2011-03-341446 ◽

2011 ◽

Vol 118 (13) ◽

pp. 3684-3693 ◽

Cited By ~ 14

Author(s):

Andrew J. Woo ◽

Jonghwan Kim ◽

Jian Xu ◽

Hui Huang ◽

Alan B. Cantor

Keyword(s):

Gene Expression ◽

Gene Regulation ◽

Globin Gene ◽

Erythroid Differentiation ◽

Regulatory Elements ◽

Specific Gene ◽

Specific Gene Expression ◽

Erythroid Maturation ◽

Globin Gene Regulation

Abstract The molecular mechanisms underlying erythroid-specific gene regulation remain incompletely understood. Closely spaced binding sites for GATA, NF-E2/maf, and CACCC interacting transcription factors play functionally important roles in globin and other erythroid-specific gene expression. We and others recently identified the CACCC-binding transcription factor ZBP-89 as a novel GATA-1 and NF-E2/mafK interacting partner. Here, we examined the role of ZBP-89 in human globin gene regulation and erythroid maturation using a primary CD34+ cell ex vivo differentiation system. We show that ZBP-89 protein levels rise dramatically during human erythroid differentiation and that ZBP-89 occupies key cis-regulatory elements within the globin and other erythroid gene loci. ZBP-89 binding correlates strongly with RNA Pol II occupancy, active histone marks, and high-level gene expression. ZBP-89 physically associates with the histone acetyltransferases p300 and Gcn5/Trrap, and occupies common sites with Gcn5 within the human globin loci. Lentiviral short hairpin RNAs knockdown of ZBP-89 results in reduced Gcn5 occupancy, decreased acetylated histone 3 levels, lower globin and erythroid-specific gene expression, and impaired erythroid maturation. Addition of the histone deacetylase inhibitor valproic acid partially reverses the reduced globin gene expression. These findings reveal an activating role for ZBP-89 in human globin gene regulation and erythroid differentiation.

Download Full-text

Erythron Database: Gene Expression From Primary Murine Embryonic, Fetal and Adult Erythroid Cell Precursors.

Blood ◽

10.1182/blood.v114.22.780.780 ◽

2009 ◽

Vol 114 (22) ◽

pp. 780-780

Author(s):

Paul D Kingsley ◽

Jenna M Frame ◽

Emily Greenfest-Allen ◽

Jeffrey Malik ◽

Kathleen E. McGrath ◽

...

Keyword(s):

Gene Expression ◽

Expression Patterns ◽

Gene Interaction ◽

Surface Expression ◽

Cell Surface Expression ◽

Specific Gene ◽

Gene Interaction Networks ◽

Erythroid Precursors ◽

Erythroid Maturation ◽

Lineage Specific Gene

Abstract Abstract 780 Gene expression analyses of mammalian erythroid precursors have been limited to time series generated from in vitro maturation model systems, one or two time point analyses from in vivo-derived samples, or pairwise comparisons of grouped precursors compared with a mutant phenotype. Despite the fact that erythroid cells comprise >25% of the cells of the mammalian fetus and adult, there have been no analyses of gene expression 1) of multiple stages of primary erythroid precursors, or 2) of similar maturational stages derived from primitive, fetal definitive and adult definitive erythroid lineages. Erythroid precursors have classically been defined using morphological characteristics following Wright-Giemsa staining, including cell size, nuclear condensation, nuclear to cytoplasmic ratio, and loss of cytoplasmic basophilia due to decreased ribosomes and increased hemoglobin. Recently, progressive stages of erythroid precursors have been defined by cell surface expression of glycophorin A/Ter-119, CD71 and CD44. It has been difficult to compare and interpret data derived from these two different approaches. We devised a cell sorting strategy utilizing a combination of cell surface expression and scatter related to size with stains for RNA and DNA to purify progressive stages of erythroid precursors (proerythroblast, ProE; basophilic erythroblast, BasoE; polychromatophilic/orthochromatic erythroblast, Poly/OrthoE; reticulocyte, Retic) that correlate well with the morphological series identified by Wright-Giemsa staining. RNA was isolated from four maturational stages (ProE, BasoE, Poly/OrthoE, and Retic) derived from three erythroid lineages: 1) “primitive” erythroid, from yolk sac and embryonic bloodstream, 2) “fetal definitive” erythroid, from E14.5 liver, and 3) “adult definitive” erythroid, from the bone marrow. Gene expression data from these samples were obtained using Affymetrix Genechip arrays. Initial analysis of the dataset indicates robust, reproducible clustering of samples within replicates of each stage/lineage. Hierarchical clustering analysis reveals both stage- and lineage-specific gene sets. A large number of genes are differentially expressed in the reticulocyte stage, regardless of lineage. Intriguingly, initial analysis also indicates that of the 12 stage/lineage data sets, the adult ProE and primitive Poly/OrthoE had the most divergent gene expression patterns distinguishing them from the other samples. Genes representing different expression patterns predicted by abundance data were confirmed using qPCR analysis. Cluster analysis as well as gene ontology mapping indicate a diverse set of expression patterns and molecular functions are present during erythroid maturation. Lineage-specific gene-interaction networks have been constructed and we are analyzing their topology to determine those most essential to erythroid maturation. Gene interactions were determined based on ranked co-expression of genes across our cell stages. These interactions are annotated by known and computationally predicted transcription factor targets, pathways (e.g., metabolic, cellular process, cell-signaling), and known erythroid-specific interactions and can be filtered according to cell-stage specific gene expression and gene function. We are developing a public access website that will aid in the analyses of these data through a searchable database of predicted and known gene-interactions. The site will facilitate comparison of gene-expression and function among the erythropoietic lineages by allowing the visualization and annotation of lineage-specific local-gene interaction networks. These studies provide the first gene expression data from defined stages of normal, primary erythroid precursors that constitute a significant portion of the embryonic, fetal and adult erythron. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Brd4 modulates the innate immune response through Mnk2–eIF4E pathway-dependent translational control of IκBα

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1700109114 ◽

2017 ◽

Vol 114 (20) ◽

pp. E3993-E4001 ◽

Cited By ~ 20

Author(s):

Yan Bao ◽

Xuewei Wu ◽

Jinjing Chen ◽

Xiangming Hu ◽

Fuxing Zeng ◽

...

Keyword(s):

Gene Expression ◽

Inflammatory Response ◽

Translational Control ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Small Subset ◽

Inflammatory Gene Expression ◽

Inflammatory Genes ◽

Inflammatory Gene

Bromodomain-containing factor Brd4 has emerged as an important transcriptional regulator of NF-κB–dependent inflammatory gene expression. However, the in vivo physiological function of Brd4 in the inflammatory response remains poorly defined. We now demonstrate that mice deficient for Brd4 in myeloid-lineage cells are resistant to LPS-induced sepsis but are more susceptible to bacterial infection. Gene-expression microarray analysis of bone marrow-derived macrophages (BMDMs) reveals that deletion of Brd4 decreases the expression of a significant amount of LPS-induced inflammatory genes while reversing the expression of a small subset of LPS-suppressed genes, including MAP kinase-interacting serine/threonine-protein kinase 2 (Mknk2). Brd4-deficient BMDMs display enhanced Mnk2 expression and the corresponding eukaryotic translation initiation factor 4E (eIF4E) activation after LPS stimulation, leading to an increased translation of IκBα mRNA in polysomes. The enhanced newly synthesized IκBα reduced the binding of NF-κB to the promoters of inflammatory genes, resulting in reduced inflammatory gene expression and cytokine production. By modulating the translation of IκBα via the Mnk2–eIF4E pathway, Brd4 provides an additional layer of control for NF-κB–dependent inflammatory gene expression and inflammatory response.

Download Full-text