Erythroblast Transformation by FLI-1 Depends upon Its Specific DNA Binding and Transcriptional Activation Properties

Ano, Sabine; Pereira, Rui; Pironin, Martine; Lesault, Isabelle; Milley, Caroline; Lebigot, Ingrid; Quang, Christine Tran; Ghysdael, Jacques

doi:10.1074/jbc.m303816200

Cited by 10 publications

(11 citation statements)

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“…Others have also shown that enforced expression of Fli-1 in avian erythroid progenitors induces their survival and proliferation and impedes their differentiation in response to Epo (3,34,40). These data strongly suggest that Fli-1 contributes to survival and proliferation of F-MuLV-infected erythroleukemic cells blocked in their differentiation.…”

supporting

confidence: 53%

Spi-1 and Fli-1 Directly Activate Common Target Genes Involved in Ribosome Biogenesis in Friend Erythroleukemic Cells

Juban

Giraud

Guyot

et al. 2009

Molecular and Cellular Biology

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Friend erythroleukemia has been a powerful model for dissection of how multiple oncogenes cooperate to initiate and maintain leukemic transformation. The Friend viral complex contains a replication-defective spleen focus-forming virus (SFFV) and a replication-competent Friend murine leukemia virus (F-MuLV). It induces a multistep erythroleukemic process in susceptible mice (8,33,50). SFFV virus is the pathogenic component responsible for this acute erythroleukemia. During the early stage of the disease, the product of the SFFV env gene, gp55, interacts with the erythropoietin receptor (Epo-R) and constitutively activates signaling pathways allowing the proliferation of proerythroblasts still able to differentiate in the absence of Epo. During this early step, the activation of signaling pathways allowing proerythroblast proliferation is also strictly dependent on the c-Kit receptor and on the small form of the STK receptor tyrosine kinase (20, 57). The second stage of the disease is characterized by a clonal population outgrowth of leukemic proerythroblasts blocked in their differentiation and able to grow as permanent cell lines in vitro. Virtually all tumors display SFFV proviral integration upstream of the Spi-1/PU.1 gene, leading to overexpression of the normal transcription factor Spi-1/PU.1 (hereinafter called Spi-1). It is now well established that the dysregulation of Spi-1 expression is a critical event in the process of SFFV-induced erythroleukemia.Indeed, the terminal erythroid differentiation can be reinitiated in Friend tumor cells by chemical inducers such as hexamethylenebisacetamide (HMBA). This differentiation is associated with a decrease in Spi-1 levels (18,24,27,51), and it can be reversed by Spi-1-enforced expression (43,64). Similarly, enforced expression of Spi-1 together with both gp55 and constitutively activated Epo-R inhibits differentiation of avian erythroid progenitors (42). Furthermore, transgenic mice overexpressing Spi-1 spontaneously develop an erythroleukemia characterized by an Epo-dependent proliferation of proerythroblasts blocked in their differentiation (38). Spi-1 knockdown induced by RNA interference is sufficient to inhibit proliferation and restore terminal erythroid differentiation of erythroleukemic cell lines established from either SFFVinfected (4) or Spi-1 transgenic mice (47). At least one contribution of Spi-1 overexpression to erythroleukemia is through the inhibition of GATA-1 transcriptional activity (39,45,46,67). Indeed, enforced expression of GATA-1 is sufficient to restore the differentiation of SFFV-infected erythroleukemic cells (13,45,46). Recent data have shown that Spi-1 inhibits expression of some GATA-1 target genes by binding to GATA-1 on transcriptional promoters and creating a repressive chromatin structure through the recruitment of pRB, the histone methylase SUV39h, and the heterochromatin protein HP1␣ (55). However, although this mechanism might explain the contribution of Spi-1 to the repression of erythroid-specific GATA-1-dependent gene tr...

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supporting

confidence: 53%

Spi-1 and Fli-1 Directly Activate Common Target Genes Involved in Ribosome Biogenesis in Friend Erythroleukemic Cells

Juban

Giraud

Guyot

et al. 2009

Molecular and Cellular Biology

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“…27,28 Contrasting with this role of FLI-1 in the positive control of megakaryopoiesis, enforced expression of FLI-1 blocks the erythrocytic differentiation of normal avian progenitors as well as several human or murine erythroleukemic cells. [29][30][31][32] Furthermore, a recent study showed that embryonic stem (ES) cell contribution to erythroid progenitors of chimeric mice is greatly enhanced when using 20,39 All these data led us to suggest that functional antagonism between FLI-1 and EKLF might be involved in the commitment toward erythrocytic or megakaryocytic differentiation, but this hypothesis still remained to be demonstrated.The present study combined inducible and constitutive shRNA expression to knockdown EKLF in mouse erythroleukemia (MEL) cells and in normal human progenitors. Concordant results of these experiments demonstrate that EKLF actually restricts megakaryocytic at the benefit of erythrocytic gene transcription and differentiation and suggest that this negative effect of EKLF on megakaryocytic commitment is mediated at least partially through the inhibition of FLI-1 recruitment to megakaryocytic as well as to Fli-1 gene promoters.…”

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confidence: 96%

Section: Introductionmentioning

confidence: 99%

EKLF restricts megakaryocytic differentiation at the benefit of erythrocytic differentiation

Bouilloux

Juban

Cohet

et al. 2008

Blood

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Previous observations suggested that functional antagonism between FLI-1 and EKLF might be involved in the commitment toward erythrocytic or megakaryocytic differentiation. We show here, using inducible shRNA expression, that EKLF knockdown in mouse erythroleukemia (MEL) cells decreases erythrocytic and increases megakaryocytic as well as Fli-1 gene expression. Chromatin immunoprecipitation analyses revealed that the increase in megakaryocytic gene expression is associated with a marked increase in RNA pol II and FLI-1 occupancy at their promoters, albeit FLI-1 protein levels are only minimally affected. Similarly, we show that human CD34 ؉ progenitors infected with shRNA lentivirus allowing EKLF knockdown generate an increased number of differentiated megakaryocytic cells associated with increased levels of megakaryocytic and Fli-1 gene transcripts. Single-cell progeny analysis of a cell population enriched in bipotent progenitors revealed that EKLF knockdown increases the number of megakaryocytic at the expense of erythrocytic colonies. Taken together, these data indicate that EKLF restricts megakaryocytic differentiation to the benefit of erythrocytic differentiation and suggest that this might be at least partially mediated by the inhibition of FLI-1 recruitment to megakaryocytic and Fli-1 gene promoters. (Blood. 2008; 112:576-584) IntroductionErythrocytic and megakaryocytic lineages derive from a common bipotent progenitor (megakaryocyte/erythroid progenitor, MEP) able to generate only erythrocytic or megakaryocytic progenitors. 1,2 A common bipotent precursor, precursor for erythroid and megakaryocytic cells (PEM), has also been characterized in the spleen of anemic mice. 3,4 Despite this very close proximity, the molecular mechanisms controlling commitment toward either one of these 2 lineages remain poorly understood.Two main models have been proposed to explain the commitment of multipotent hematopoietic progenitors. 5,6 According to the "instructive model," lineage commitment is dictated by specific extracellular signals such as cytokines. Although erythropoietin and thrombopoietin enhance the proliferation, survival, and differentiation of already committed erythrocytic and megakaryocytic progenitors expressing erythropoietin-or thrombopoietin-specific receptors, it is now well established that they have no instructive role in the commitment. 7,8 Available data are more compatible with a "stochastic model," suggesting that commitment is dictated by the spontaneous formation of specific and mutually exclusive combinations of transcription factors. 5,6 At least 10 different transcription factors involved in erythrocytic and/or megakaryocytic differentiation have been identified. [9][10][11][12] Most of them, such as GATA-1, NF-E2, TAL-1, LMO2, FOG1, and GFI-1B, are involved in the regulation of both erythrocytic and megakaryocytic differentiation. However, there is no indication that differential expression of either one of these 6 factors might be involved in the commitment decision. Several transgenic...

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“…Luciferase reporter assays QT6 or HEK293 cells on 24-well plates were transfected with PUx3-TK81-Luc (Ano et al, 2004), pFR-Luc (Stratagene, La Jolla, CA, USA) or pGL3-M-CSFR-Luc (Dahl et al, 2007) luciferase reporter construct (50 ng/well), together with effector plasmids (DEB-PU.1 (Ano et al, 2004), pCMV-T7-wtcSki, pCMV-T7-mt-cSki, pM or pM-PU.1) as indicated in the figure legend. The total amount of transfected DNA was equalized with pEGFP-C1 (vector, Clontech).…”

Section: Methodsmentioning

confidence: 99%

Ski can negatively regulates macrophage differentiation through its interaction with PU.1

2007

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Erythroblast Transformation by FLI-1 Depends upon Its Specific DNA Binding and Transcriptional Activation Properties

Cited by 10 publications

References 54 publications

Spi-1 and Fli-1 Directly Activate Common Target Genes Involved in Ribosome Biogenesis in Friend Erythroleukemic Cells

Spi-1 and Fli-1 Directly Activate Common Target Genes Involved in Ribosome Biogenesis in Friend Erythroleukemic Cells

EKLF restricts megakaryocytic differentiation at the benefit of erythrocytic differentiation

Ski can negatively regulates macrophage differentiation through its interaction with PU.1

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