EDAG positively regulates erythroid differentiation and modifies GATA1 acetylation through recruiting p300

Single-cell RNA seq analysis of erythroid cells reveals a specific sub-population of stress erythroid progenitors

BACKGROUND

: Erythroid cells play important roles in hemostasis and disease. However, there is still significant knowledge gap regarding stress erythropoiesis.

METHODS

: Two single-cell RNAseq datasets of erythroid cells on GEO with accession numbers GSE149938 and GSE184916 were obtained. The datasets from two sources, bone marrow and peripheral blood were analyzed using Seurat v4.1.1, and other tools in R. QC metrics were performed, data were normalized and scaled. Principal components that capture the variation of the data were determined. In clustering the cells, KNN graph was constructed and Louvain algorithm was applied to optimize the standard modularity function. Clusters were defined via differential expression of features.

RESULTS

We identified 9 different cell types, with a particular cluster representing the stress erythroids. The clusters showed differentially expressed genes as observed from the gene signature plot. The stress erythroid cluster differentially expressed some genes including ALAS2, HEMGN, and GUK1.

CONCLUSION

The erythroid population was found to be heterogeneous, with a distinct sub-cell type constituting the stress erythroids; this may have important implications for our knowledge of steady-state and stress erythropoiesis, and the markers found in this cluster may prove useful for future research into the dynamics of stress erythroid progenitor cell differentiation.

The role of GATA switch in benzene metabolite hydroquinone inhibiting erythroid differentiation in K562 cells

The phenolic metabolite of benzene, hydroquinone (HQ), has potential risks for hematological disorders and hematotoxicity in humans. Previous studies have revealed that reactive oxygen species, DNA methylation, and histone acetylation participate in benzene metabolites inhibiting erythroid differentiation in hemin-induced K562 cells. GATA1 and GATA2 are crucial erythroid-specific transcription factors that exhibit dynamic expression patterns during erythroid differentiation. We investigated the role of GATA factors in HQ-inhibited erythroid differentiation in K562 cells. When K562 cells were induced with 40 μM hemin for 0-120 h, the mRNA and protein levels of GATA1 and GATA2 changed dynamically. After exposure to 40 μM HQ for 72 h, K562 cells were induced with 40 μM hemin for 48 h. HQ considerably reduced the percentage of hemin-induced Hb-positive cells, decreased the GATA1 mRNA, protein, and occupancy levels at α-globin and β-globin gene clusters, and increased the GATA2 mRNA and protein levels significantly. ChIP-seq analysis revealed that HQ reduced GATA1 occupancy, and increased GATA2 occupancy at most gene loci in hemin-induced K562 cells. And GATA1 and GATA2 might play essential roles in the erythroid differentiation protein interaction network. These results elucidate that HQ decreases GATA1 occupancy and increases GATA2 occupancy at the erythroid gene loci, thereby downregulating GATA1 and upregulating GATA2 expression, which in turn modulates the expression of erythroid genes and inhibits erythroid differentiation. This partially explains the mechanism of benzene hematotoxicity.

Germline ERCC excision repair 6 like 2 (ERCC6L2) mutations lead to impaired erythropoiesis and reshaping of the bone marrow microenvironment

Despite the inclusion of inherited myeloid malignancies as a separate entity in the World Health Organization Classification, many established predisposing loci continue to lack functional characterization. While germline mutations in the DNA repair factor ERCC excision repair 6 like 2 (ERCC6L2) give rise to bone marrow failure and acute myeloid leukaemia, their consequences on normal haematopoiesis remain unclear. To functionally characterise the dual impact of germline ERCC6L2 loss on human primary haematopoietic stem/progenitor cells (HSPCs) and mesenchymal stromal cells (MSCs), we challenged ERCC6L2-silenced and patient-derived cells ex vivo. Here, we show for the first time that ERCC6L2-deficiency in HSPCs significantly impedes their clonogenic potential and leads to delayed erythroid differentiation. This observation was confirmed by CIBERSORTx RNA-sequencing deconvolution performed on ERCC6L2-silenced erythroid-committed cells, which demonstrated higher proportions of polychromatic erythroblasts and reduced orthochromatic erythroblasts versus controls. In parallel, we demonstrate that the consequences of ERCC6L2-deficiency are not limited to HSPCs, as we observe a striking phenotype in patient-derived and ERCC6L2-silenced MSCs, which exhibit enhanced osteogenesis and suppressed adipogenesis. Altogether, our study introduces a valuable surrogate model to study the impact of inherited myeloid mutations and highlights the importance of accounting for the influence of germline mutations in HSPCs and their microenvironment.

The phosphorylation to acetylation/methylation cascade in transcriptional regulation: how kinases regulate transcriptional activities of DNA/histone-modifying enzymes

Transcription factors directly regulate gene expression by recognizing and binding to specific DNA sequences, involving the dynamic alterations of chromatin structure and the formation of a complex with different kinds of cofactors, like DNA/histone modifying-enzymes, chromatin remodeling factors, and cell cycle factors. Despite the significance of transcription factors, it remains unclear to determine how these cofactors are regulated to cooperate with transcription factors, especially DNA/histone modifying-enzymes. It has been known that DNA/histone modifying-enzymes are regulated by post-translational modifications. And the most common and important modification is phosphorylation. Even though various DNA/histone modifying-enzymes have been classified and partly explained how phosphorylated sites of these enzymes function characteristically in recent studies. It still needs to find out the relationship between phosphorylation of these enzymes and the diseases-associated transcriptional regulation. Here this review describes how phosphorylation affects the transcription activity of these enzymes and other functions, including protein stability, subcellular localization, binding to chromatin, and interaction with other proteins.

Autophagy regulated by the HIF/REDD1/mTORC1 signaling is progressively increased during erythroid differentiation under hypoxia

For hematopoietic stem and progenitor cells (HSPCs), hypoxia is a specific microenvironment known as the hypoxic niche. How hypoxia regulates erythroid differentiation of HSPCs remains unclear. In this study, we show that hypoxia evidently accelerates erythroid differentiation, and autophagy plays a pivotal role in this process. We further determine that mTORC1 signaling is suppressed by hypoxia to relieve its inhibition of autophagy, and with the process of erythroid differentiation, mTORC1 activity gradually decreases and autophagy activity increases accordingly. Moreover, we provide evidence that the HIF-1 target gene REDD1 is upregulated to suppress mTORC1 signaling and enhance autophagy, thereby promoting erythroid differentiation under hypoxia. Together, our study identifies that the enhanced autophagy by hypoxia favors erythroid maturation and elucidates a new regulatory pattern whereby autophagy is progressively increased during erythroid differentiation, which is driven by the HIF-1/REDD1/mTORC1 signaling in a hypoxic niche.

Epigenetic and Transcriptional Control of Erythropoiesis

Erythropoiesis is a process of enormous magnitude, with the average person generating two to three million red cells every second. Erythroid progenitors start as large cells with large nuclei, and over the course of three to four cell divisions they undergo a dramatic decrease in cell size accompanied by profound nuclear condensation, which culminates in enucleation. As maturing erythroblasts are undergoing these dramatic phenotypic changes, they accumulate hemoglobin and express high levels of other erythroid-specific genes, while silencing much of the non-erythroid transcriptome. These phenotypic and gene expression changes are associated with distinct changes in the chromatin landscape, and require close coordination between transcription factors and epigenetic regulators, as well as precise regulation of RNA polymerase II activity. Disruption of these processes are associated with inherited anemias and myelodysplastic syndromes. Here, we review the epigenetic mechanisms that govern terminal erythroid maturation, and their role in human disease.

Hemogen /BRG1 cooperativity modulates promoter and enhancer activation during erythropoiesis

Hemogen, also known as EDAG, is a hematopoietic tissue-specific gene that regulates the proliferation and differentiation of hematopoietic cells. However, the mechanism underlying hemogen function in erythropoiesis is unknown. We found that depletion of hemogen in human CD34+ erythroid progenitor cells and HUDEP2 cells significantly reduced the expression of genes associated with heme and hemoglobin synthesis, supporting a positive role of hemogen in erythroid maturation. In human K562 cells, hemogen antagonized the occupancy of co-repressors NuRD complex and facilitated LDB1 complex-mediated chromatin looping. Hemogen recruited SWI/SNF complex ATPase BRG1 as a co-activator to regulate nucleosome accessibility and H3K27ac enrichment for promoter and enhancer activity. To ask if hemogen/BRG1 cooperativity is conserved in mammalian systems, we generated hemogen KO/KI mice and investigated hemogen/BRG1 function in murine erythropoiesis. Loss of hemogen in E12.5-E16.5 fetal liver cells impeded erythroid differentiation through reducing the production of mature erythroblasts. ChIP-seq in WT and hemogen KO animal revealed BRG1 is largely dependent on hemogen to regulate chromatin accessibility at erythroid gene promoters and enhancers. In summary, hemogen/BRG1 interaction in mammals is essential for fetal erythroid maturation and hemoglobin production through its active role in promoter and enhancer activity and chromatin organization.

Hemgn Protects Hematopoietic Stem and Progenitor Cells Against Transplantation Stress Through Negatively Regulating IFN-γ Signaling

Hematopoietic stem and progenitor cells (HSPCs) possess the remarkable ability to regenerate the whole blood system in response to ablated stress demands. Delineating the mechanisms that maintain HSPCs during regenerative stresses is increasingly important. Here, it is shown that Hemgn is significantly induced by hematopoietic stresses including irradiation and bone marrow transplantation (BMT). Hemgn deficiency does not disturb steady-state hematopoiesis in young mice. Hemgn^-/- HSPCs display defective engraftment activity during BMT with reduced homing and survival and increased apoptosis. Transcriptome profiling analysis reveals that upregulated genes in transplanted Hemgn^-/- HSPCs are enriched for gene sets related to interferon gamma (IFN-γ) signaling. Hemgn^-/- HSPCs show enhanced responses to IFN-γ treatment and increased aging over time. Blocking IFN-γ signaling in irradiated recipients either pharmacologically or genetically rescues Hemgn^-/- HSPCs engraftment defect. Mechanistical studies reveal that Hemgn deficiency sustain nuclear Stat1 tyrosine phosphorylation via suppressing T-cell protein tyrosine phosphatase TC45 activity. Spermidine, a selective activator of TC45, rescues exacerbated phenotype of HSPCs in IFN-γ-treated Hemgn^-/- mice. Collectively, these results identify that Hemgn is a critical regulator for successful engraftment and reconstitution of HSPCs in mice through negatively regulating IFN-γ signaling. Targeted Hemgn may be used to improve conditioning regimens and engraftment during HSPCs transplantation.

GPS2 promotes erythroid differentiation by control of the stability of EKLF protein

Erythropoiesis is a complex multistage process that involves differentiation of early erythroid progenitors to enucleated mature red blood cells, in which lineage-specific transcription factors play essential roles. Erythroid Krüppel-like factor (EKLF/KLF1) is a pleiotropic erythroid transcription factor that is required for the proper maturation of the erythroid cells, whose expression and activation are tightly controlled in a temporal and differentiation stage-specific manner. Here, we uncover a novel role of G-protein pathway suppressor 2 (GPS2), a subunit of the nuclear receptor corepressor/silencing mediator of retinoic acid and thyroid hormone receptor corepressor complex, in erythrocyte differentiation. Our study demonstrates that knockdown of GPS2 significantly suppresses erythroid differentiation of human CD34+ cells cultured in vitro and xenotransplanted in nonobese diabetic/severe combined immunodeficiency/interleukin-2 receptor γ-chain null mice. Moreover, global deletion of GPS2 in mice causes impaired erythropoiesis in the fetal liver and leads to severe anemia. Flow cytometric analysis and Wright-Giemsa staining show a defective differentiation at late stages of erythropoiesis in Gps2-/- embryos. Mechanistically, GPS2 interacts with EKLF and prevents proteasome-mediated degradation of EKLF, thereby increasing EKLF stability and transcriptional activity. Moreover, we identify the amino acids 191-230 region in EKLF protein, responsible for GPS2 binding, that is highly conserved in mammals and essential for EKLF protein stability. Collectively, our study uncovers a previously unknown role of GPS2 as a posttranslational regulator that enhances the stability of EKLF protein and thereby promotes erythroid differentiation.

Regulating the Regulators: The Role of Histone Deacetylase 1 (HDAC1) in Erythropoiesis

Histone deacetylases (HDACs) play important roles in transcriptional regulation in eukaryotic cells. Class I deacetylase HDAC1/2 often associates with repressor complexes, such as Sin3 (Switch Independent 3), NuRD (Nucleosome remodeling and deacetylase) and CoREST (Corepressor of RE1 silencing transcription factor) complexes. It has been shown that HDAC1 interacts with and modulates all essential transcription factors for erythropoiesis. During erythropoiesis, histone deacetylase activity is dramatically reduced. Consistently, inhibition of HDAC activity promotes erythroid differentiation. The reduction of HDAC activity not only results in the activation of transcription activators such as GATA-1 (GATA-binding factor 1), TAL1 (TAL BHLH Transcription Factor 1) and KLF1 (Krüpple-like factor 1), but also represses transcription repressors such as PU.1 (Putative oncogene Spi-1). The reduction of histone deacetylase activity is mainly through HDAC1 acetylation that attenuates HDAC1 activity and trans-repress HDAC2 activity through dimerization with HDAC1. Therefore, the acetylation of HDAC1 can convert the corepressor complex to an activator complex for gene activation. HDAC1 also can deacetylate non-histone proteins that play a role on erythropoiesis, therefore adds another layer of gene regulation through HDAC1. Clinically, it has been shown HDACi can reactivate fetal globin in adult erythroid cells. This review will cover the up to date research on the role of HDAC1 in modulating key transcription factors for erythropoiesis and its clinical relevance.

Chromatin-modifying drugs and metabolites in cell fate control

For multicellular organisms, it is essential to produce a variety of specialized cells to perform a dazzling panoply of functions. Chromatin plays a vital role in determining cellular identities, and it dynamically regulates gene expression in response to changing nutrient metabolism and environmental conditions. Intermediates produced by cellular metabolic pathways are used as cofactors or substrates for chromatin modification. Drug analogues of metabolites that regulate chromatin-modifying enzyme reactions can also regulate cell fate by adjusting chromatin organization. In recent years, there have been many studies about how chromatin-modifying drug molecules or metabolites can interact with chromatin to regulate cell fate. In this review, we systematically discuss how DNA and histone-modifying molecules alter cell fate by regulating chromatin conformation and propose a mechanistic model that explains the process of cell fate transitions in a concise and qualitative manner.

EDAG mediates Hsp70 nuclear localization in erythroblasts and rescues dyserythropoiesis in myelodysplastic syndrome

During human erythroid maturation, Hsp70 translocates into the nucleus and protects GATA-1 from caspase-3 cleavage. Failure of Hsp70 to localize to the nucleus was found in Myelodysplastic syndrome (MDS) erythroblasts and can induce dyserythropoiesis, with arrest of maturation and death of erythroblasts. However, the mechanism of the nuclear trafficking of Hsp70 in erythroblasts remains unknown. Here, we found the hematopoietic transcriptional regulator, EDAG, to be a novel binding partner of Hsp70 that forms a protein complex with Hsp70 and GATA-1 during human normal erythroid differentiation. EDAG overexpression blocked the cytoplasmic translocation of Hsp70 induced by EPO deprivation, inhibited GATA-1 degradation, thereby promoting erythroid maturation in an Hsp70-dependent manner. Furthermore, in myelodysplastic syndrome (MDS) patients with dyserythropoiesis, EDAG is dramatically down-regulated, and forced expression of EDAG has been found to restore the localization of Hsp70 in the nucleus and elevate the protein level of GATA-1 to a significant extent. In addition, EDAG rescued the dyserythropoiesis of MDS patients by increasing erythroid differentiation and decreasing cell apoptosis. This study demonstrates the molecular mechanism of Hsp70 nuclear sustaining during erythroid maturation and establishes that EDAG might be a suitable therapeutic target for dyserythropoiesis in MDS patients.

UM171 expands distinct types of myeloid and NK progenitors from human pluripotent stem cells

Scaling up blood cell production from hPSCs is critical to advancing hPSC technologies for blood transfusion, immunotherapy, and transplantation. Here we explored the potential of the HSC agonist pyrimido-indole derivative UM171, to expand hematopoietic progenitors (HPs) derived from hPSCs in chemically defined conditions. We revealed that culture of hPSC-HPs in HSC expansion conditions (SFEM with added TPO, SCF, FLT3L, IL3 and IL6) in the presence of UM171 predominantly expanded HPs with a unique CD34⁺CD41a^loCD45⁺ phenotype that were enriched in granulocytic progenitors (G-CFCs). In contrast, in lymphoid cultures on OP9-DLL4, in the presence of SCF, FLT3L, and IL7, UM171 selectively expanded CD34⁺CD45⁺CD7⁺ lymphoid progenitors with NK cell potential, and increased NK cell output up to 10-fold. These studies should improve our understanding of the effect of UM171 on de novo generated HPs, and facilitate development of protocols for robust granulocyte and lymphoid cell production from hPSCs, for adoptive immunotherapies.

Divergent Hemogen genes of teleosts and mammals share conserved roles in erythropoiesis: analysis using transgenic and mutant zebrafish

Hemogen is a vertebrate transcription factor that performs important functions in erythropoiesis and testicular development and may contribute to neoplasia. Here we identify zebrafish Hemogen and show that it is considerably smaller (∼22 kDa) than its human ortholog (∼55 kDa), a striking difference that is explained by an underlying modular structure. We demonstrate that Hemogens are largely composed of 21-25 amino acid repeats, some of which may function as transactivation domains (TADs). Hemogen expression in embryonic and adult zebrafish is detected in hematopoietic, renal, neural and gonadal tissues. Using Tol2- and CRISPR/Cas9-generated transgenic zebrafish, we show that Hemogen expression is controlled by two Gata1-dependent regulatory sequences that act alone and together to control spatial and temporal expression during development. Partial depletion of Hemogen in embryos by morpholino knockdown reduces the number of erythrocytes in circulation. CRISPR/Cas9-generated zebrafish lines containing either a frameshift mutation or an in-frame deletion in a putative, C-terminal TAD display anemia and embryonic tail defects. This work expands our understanding of Hemogen and provides mutant zebrafish lines for future study of the mechanism of this important transcription factor.

Summary: Transgenic and mutant zebrafish lines were created to characterize the expression and functions of Hemogen, a transcription factor involved in the formation of red blood cells and other processes.

EDAG promotes the expansion and survival of human CD34+ cells

EDAG is multifunctional transcriptional regulator primarily expressed in the lin^loc^-kit⁺Sca-1⁺ hematopoietic stem cells (HSC) and CD34⁺ progenitor cells. Previous studies indicate that EDAG is required for maintaining hematopoietic lineage commitment balance. Here using ex vivo culture and HSC transplantation models, we report that EDAG enhances the proliferative potential of human cord blood CD34⁺ cells, increases survival, prevents cell apoptosis and promotes their repopulating capacity. Moreover, EDAG overexpression induces rapid entry of CD34⁺ cells into the cell cycle. Gene expression profile analysis indicate that EDAG knockdown leads to down-regulation of various positive cell cycle regulators including cyclin A, B, D, and E. Together these data provides novel insights into EDAG in regulation of expansion and survival of human hematopoietic stem/progenitor cells.

Multiple functions of CREB-binding protein during postembryonic development: identification of target genes

Background

Juvenile hormones (JH) and ecdysteroids control postembryonic development in insects. They serve as valuable targets for pest management. Hence, understanding the molecular mechanisms of their action is of crucial importance. CREB-binding protein (CBP) is a universal transcriptional co-regulator. It controls the expression of several genes including those from hormone signaling pathways through co-activation of many transcription factors. However, the role of CBP during postembryonic development in insects is not well understood. Therefore, we have studied the role of CBP in postembryonic development in Tribolium, a model coleopteran insect.

Results

CBP is ubiquitously expressed in the red flour beetle, Tribolium castaneum. RNA interference (RNAi) mediated knockdown of CBP resulted in a decrease in JH induction of Kr-h1 gene expression in Tribolium larvae and led to a block in their development. Moreover, the injection of CBP double-stranded RNA (dsRNA) showed lethal phenotypes within 8 days of injection. RNA-seq and subsequent differential gene expression analysis identified CBP target genes in Tribolium. Knockdown of CBP caused a decrease in the expression of 1306 genes coding for transcription factors and other proteins associated with growth and development. Depletion of CBP impaired the expression of several JH response genes (e.g., Kr-h1, Hairy, early trypsin) and ecdysone response genes (EcR, E74, E75, and broad complex). Further, GO enrichment analyses of the downregulated genes showed enrichment in different functions including developmental processes, pigmentation, anatomical structure development, regulation of biological and cellular processes, etc.

Conclusion

These data suggest diverse but crucial roles for CBP during postembryonic development in the coleopteran model insect, Tribolium. It can serve as a target for RNAi mediated pest management of this stored product pest.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4373-3) contains supplementary material, which is available to authorized users.

Transcription factors, coregulators, and epigenetic marks are linearly correlated and highly redundant

The DNA microstates that regulate transcription include sequence-specific transcription factors (TFs), coregulatory complexes, nucleosomes, histone modifications, DNA methylation, and parts of the three-dimensional architecture of genomes, which could create an enormous combinatorial complexity across the genome. However, many proteins and epigenetic marks are known to colocalize, suggesting that the information content encoded in these marks can be compressed. It has so far proved difficult to understand this compression in a systematic and quantitative manner. Here, we show that simple linear models can reliably predict the data generated by the ENCODE and Roadmap Epigenomics consortia. Further, we demonstrate that a small number of marks can predict all other marks with high average correlation across the genome, systematically revealing the substantial information compression that is present in different cell lines. We find that the linear models for activating marks are typically cell line-independent, while those for silencing marks are predominantly cell line-specific. Of particular note, a nuclear receptor corepressor, transducin beta-like 1 X-linked receptor 1 (TBLR1), was highly predictive of other marks in two hematopoietic cell lines. The methodology presented here shows how the potentially vast complexity of TFs, coregulators, and epigenetic marks at eukaryotic genes is highly redundant and that the information present can be compressed onto a much smaller subset of marks. These findings could be used to efficiently characterize cell lines and tissues based on a small number of diagnostic marks and suggest how the DNA microstates, which regulate the expression of individual genes, can be specified.

Cell-specific expression of aquaporin-5 (Aqp5) in alveolar epithelium is directed by GATA6/Sp1 via histone acetylation

Epigenetic regulation of differentiation-related genes is poorly understood. We previously reported that transcription factors GATA6 and Sp1 interact with and activate the rat proximal 358-bp promoter/enhancer (p358P/E) of lung alveolar epithelial type I (AT1) cell-specific gene aquaporin-5 (Aqp5). In this study, we found that histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) increased AQP5 expression and Sp1-mediated transcription of p358P/E. HDAC3 overexpression inhibited Sp1-mediated Aqp5 activation, while HDAC3 knockdown augmented AQP5 protein expression. Knockdown of GATA6 or transcriptional co-activator/histone acetyltransferase p300 decreased AQP5 expression, while p300 overexpression enhanced p358P/E activation by GATA6 and Sp1. GATA6 overexpression, SAHA treatment or HDAC3 knockdown increased histone H3 (H3) but not histone H4 (H4) acetylation within the homologous p358P/E region of mouse Aqp5. HDAC3 binds to Sp1 and HDAC3 knockdown increased interaction of GATA6/Sp1, GATA6/p300 and Sp1/p300. These results indicate that GATA6 and HDAC3 control Aqp5 transcription via modulation of H3 acetylation/deacetylation, respectively, through competition for binding to Sp1, and suggest that p300 modulates acetylation and/or interacts with GATA6/Sp1 to regulate Aqp5 transcription. Cooperative interactions among transcription factors and histone modifications regulate Aqp5 expression during alveolar epithelial cell transdifferentiation, suggesting that HDAC inhibitors may enhance repair by promoting acquisition of AT1 cell phenotype.

Up-regulation of IRF-3 expression through GATA-1 acetylation by histone deacetylase inhibitor in lung adenocarcinoma A549 cells

Interferon regulatory factor 3 (IRF-3) is an important transcription factor for interferon genes. Although its functional activation by viral infection has been widely explicated, the regulatory mechanism of IRF-3 gene expression in cancer cells is poorly understood. In this study, we demonstrated treatment of lung adenocarcinoma A549 cells with trichostatin A (TSA) and valproic acid (VPA), two different classes of histone deacetylase inhibitors, strongly stimulated IRF-3 gene expression. Truncated and mutated IRF-3 promoter indicated that a specific GATA-1 element was responsible for TSA-induced activation of IRF-3 promoter. Chromatin immunoprecipitation and electrophoretic mobility shift assay showed that TSA treatment increased the binding affinity of GATA-1 to IRF-3 promoter. Using immunoprecipitation assay and immunoblotting, we demonstrated that TSA increased the level of acetylated GATA-1 in A549 cells. In summary, our study implied that TSA enhanced IRF-3 gene expression through increased GATA-1 recruitment to IRF-3 promoter and the acetylation level of GATA-1 in lung adenocarcinoma A549 cells.

EDAG-1 promotes proliferation and invasion of human thyroid cancer cells by activating MAPK/Erk and AKT signal pathways

Erythroid differentiation-associated gene (EDAG) is differentially expressed in normal hematopoietic progenitor/stem cells and a variety of embryonic tissues. High EDAG-1 expression is also found in human thyroid cancer cells and peripheral blood of patients with leukemia, but its functional significance was unclear. Current study aims to further clarify the expression pattern of EDAG-1 and tests its roles in proliferation and invasion of human thyroid cancer cells in vitro and in vivo. To this end, we have performed gain-of-function and loss-of-function studies to clarify how EDAG-1 regulates the proliferation, invasion, and adhesion ability of human thyroid cancer cells SW579cells. We found that overexpression of EDAG-1 promoted the proliferation, invasion, and adhesion of human thyroid cancer cells, whereas silencing of EDAG-1 reversed all these changes and reduced the tumorigenesis risk of nude mice. Mechanistically, we found that overexpression of EDAG-1 activated the MAPK/Erk and AKT signal pathways. These findings provide novel insights of the role of EDAG-1 in thyroid tumors, and may have direct clinical implication.

miR-214 protects erythroid cells against oxidative stress by targeting ATF4 and EZH2

Nuclear factor (erythroid-derived 2) like 2 (Nrf2) is a key regulator in protecting cells against stress by targeting many anti-stress response genes. Recent evidence also reveals that Nrf2 functions partially by targeting mircroRNAs (miRNAs). However, the understanding of Nrf2-mediated cytoprotection through miRNA-dependent mechanisms is largely unknown. In the current study, we identified a direct Nrf2 targeting miRNA, miR-214, and demonstrated a protective role of miR-214 in erythroid cells against oxidative stresses generated by radiation, excess iron and arsenic (As) exposure. miR-214 expression was transcriptionally repressed by Nrf2 through a canonical antioxidant response element (ARE) within its promoter region, and this repression is ROS-dependence. The suppression of miR-214 by Nrf2 could antagonize oxidative stress-induced cell death in erythroid cells by two ways. First, miR-214 directly targeted ATF4, a crucial transcriptional factor involved in anti-stress responses, down regulation of miR-214 releases the repression of ATF4 translation and leads to increased ATF4 protein content. Second, miR-214 was able to prevent cell death by targeting EZH2, the catalytic core component of PRC2 complex that is responsible for tri-methylation reaction at lysine 27 (K27) of histone 3 (H3) (H3K27me3), by which As-induced miR-214 reduction resulted in an increased global H3K27me3 level and a compromised overexpression of a pro-apoptotic gene Bim. These two pathways downstream of miR-214 synergistically cooperated to antagonize erythroid cell death upon oxidative stress. Our combined data revealed a protective role of miR-214 signaling in erythroid cells against oxidative stress, and also shed new light on Nrf2-mediated cytoprotective machinery.

Promotion of Erythropoietic Differentiation in Hematopoietic Stem Cells by SOCS3 Knock-Down

Suppressor of cytokine signaling 3 (SOCS3) plays an important role in mice fetal liver erythropoiesis, but the roles of SOCS3 in human hematopoietic stem cells (HSCs) have not been well investigated. In the present study, lentiviral small interference RNA expression vectors (shRNA) of SOCS3 were constructed and stably transferred into HSCs. We found that SOCS3 knockdown induced erythroid expansion in HSCs. Conversely, Ectopic expression of SOCS3 in progenitor cells blocked erythroid expansion and erythroid colony formation of HSCs. To further explore the involved mechanism, we compared gene expression profiles of SOCS3-shRNA tranduced HSCs with that of control HSCs by whole genome microarrays. The results indicated that cell developmental process related genes, especially hematopoietic lineage-specific genes, associated with the responses to SOCS3 in HSCs.Downexpression of SOCS3 in HSCs or differentiated erythroid progenitor cells induced a transcriptional program enriched for erythroid development relative genes. Our results proved that SOCS3 down-expression induced lineage commitment towards erythroid progenitor cell fate by activation of erythroid-specific gene in HSCs and provided new insight into the mechanism of erythropoietic development.

The over-expression of aquaporin-1 alters erythroid gene expression in human erythroleukemia K562 cells

Aquaporin genes are differentially expressed in primitive versus definitive erythropoiesis. Our previous research results showed that over-expression of aquaporin-1 (AQP1) gene greatly promotes the erythroid differentiation of erythroleukemia K562 cells, using benzidine staining and quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) analysis for representative erythroid-related genes, including γ-globin. But the molecular mechanisms underlying erythroid-specific gene regulation remain unknown. In this study, we demonstrated that AQP1 induced hemoglobins expression and altered erythroid gene expression by microarray analysis in K562 cells. The retroviral expression vector of AQP1 (pBABE-puro-AQP1) was constructed and infected K562 cells to establish a stable AQP1 over-expression cell line (K562-AQP1). AQP1 over-expression effectively inhibited cell proliferation and induced cell growth arrest in G1 phase of K562 cells. Then microarray profile was applied to analyze the differentially expressed genes which involved the mechanism of AQP1 in erythroid differentiation induction. The DAVID functional annotation clustering tool was used to identify biological functions enriched with the differentially expressed genes (n = 466 genes) and to group genes into clusters based on their functional similarity. Significant enrichment of genes involved in "oxygen transporter activity" (p = 3.8E-7) including hemoglobins (HBD, HBG, HBB, HBE1, and HBQ1), HEMGN, and EBP42 were validated by qRT-PCR. Moreover, silencing of HEMGN by RNA interference in K562-AQP1 cells resulted in down-regulation of these genes. These data provide a better understanding of the role of AQP1 in erythroid differentiation, by promoting HEMGN induction and other potential signaling pathways associated with hemoglobin induction.