Myc Inhibits p27-Induced Erythroid Differentiation of Leukemia Cells by Repressing Erythroid Master Genes without Reversing p27-Mediated Cell Cycle Arrest

Acosta, Juan Carlos; Ferrándiz, Nuria; Bretones, Gabriel; Torrano, Verónica; Blanco, Rosa; Richard, Carlos; O’Connell, Brenda; Sedivy, John M.; Delgado, M. Dolores; León, Javier

doi:10.1128/mcb.00752-08

Cited by 55 publications

(60 citation statements)

References 57 publications

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“…Studies in G1E erythroid cell lines report that forced Myc expression prevented cell cycle arrest but had minimal effects on erythroid maturation (20). In contrast, Myc expression blocked erythroid differentiation in human leukemia K562 cells without preventing the cell cycle exit (21). These discrepancies are possibly a result of the different cell lines used as models of terminal erythroid maturation.…”

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confidence: 51%

Down-regulation of Myc Is Essential for Terminal Erythroid Maturation

Jayapal

Lee

et al. 2010

Journal of Biological Chemistry

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Terminal differentiation of mammalian erythroid progenitors involves 4 -5 cell divisions and induction of many erythroid important genes followed by chromatin and nuclear condensation and enucleation. The protein levels of c-Myc (Myc) are reduced dramatically during late stage erythroid maturation, coinciding with cell cycle arrest in G 1 phase and enucleation, suggesting possible roles for c-Myc in either or both of these processes. Here we demonstrate that ectopic Myc expression affects terminal erythroid maturation in a dose-dependent manner. Expression of Myc at physiological levels did not affect erythroid differentiation or cell cycle shutdown but specifically blocked erythroid nuclear condensation and enucleation. Continued Myc expression prevented deacetylation of several lysine residues in histones H3 and H4 that are normally deacetylated during erythroid maturation. The histone acetyltransferase Gcn5 was up-regulated by Myc, and ectopic Gcn5 expression partially blocked enucleation and inhibited the late stage erythroid nuclear condensation and histone deacetylation. When overexpressed at levels higher than the physiological range, Myc blocked erythroid differentiation, and the cells continued to proliferate in cytokine-free, serum-containing culture medium with an early erythroblast morphology. Gene expression analysis demonstrated the dysregulation of erythropoietin signaling pathway and the up-regulation of several positive regulators of G 1 -S cell cycle checkpoint by supraphysiological levels of Myc. These results reveal an important dose-dependent function of Myc in regulating terminal maturation in mammalian erythroid cells.Mammalian terminal erythroid development is a precisely regulated process involving rapid proliferation and serial morphological changes of committed erythroid progenitors (colony forming units-erythroid, or CFU-E) 5 to form mature erythrocytes. The initial stages of terminal erythroid maturation are highly dependent on erythropoietin (1), whose roles in activation of erythroid specific genes, terminal proliferation, and protection against apoptosis are well understood (2). This is followed by an erythropoietin-independent, fibronectin-dependent phase where survival and proliferation of the erythroblasts require signaling by ␣4␤1 integrins (3). Upon erythropoietin stimulation, CFU-E progenitors undergo 4 -5 cell divisions accompanied by a decrease in cell size, increase in hemoglobin content, and nuclear condensation followed by withdrawal from the cell cycle (4). Late stage mammalian erythroblasts undergo nuclear condensation and enucleate by extrusion of the pycnotic nucleus surrounded by a thin layer of cytoplasm and cell membrane (5-7). The molecular mechanisms that regulate this hallmark process remain to be fully elucidated. We previously reported that Rac GTPases and their downstream effector mDia2 play important roles in the cytoskeletal reorganization leading to the extrusion of the pycnotic nucleus from late stage erythroblasts (8). Nevertheless, the mechanisms regu...

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confidence: 51%

Down-regulation of Myc Is Essential for Terminal Erythroid Maturation

Jayapal

Lee

et al. 2010

Journal of Biological Chemistry

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“…Moreover, the overexpression of p27 in C2C12 cells induces myogenic differentiation, whereas elimination of p27 prevents differentiation (Munoz-Alonso et al, 2005). In another example it has been shown that overexpression of p27 induces the expression of erythroid markers in the K562 cell line (Acosta et al, 2008). All these data suggested that the nuclear role of p27 in quiescence might rely not only on the inhibition of cyclin-cdk complexes but also on the transcriptional repression of specific target genes.…”

Section: Introductionmentioning

confidence: 89%

p27Kip1 represses transcription by direct interaction with p130/E2F4 at the promoters of target genes

et al. 2011

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“…Kp27-5 cells are K562 cells stably transfected with a p27 gene inducible by Zn 2ϩ (39). Kp27MER are Kp27-5 cells transduced with the MycER gene (40). KmycBp53 are KmycB cells expressing a p53 mutant that is activated at 32°C (41).…”

Section: Methodsmentioning

confidence: 99%

“…Immunofluorescence Analysis-Kp27MER cells were treated with ZnSO 4 and/or 4HT for 24 h and immunostained with anti-SKP2 and -p27 antibodies as described and revealed with fluorescein-or rhodamine-conjugated secondary antibodies as described (40). The cells were mounted with Vectashield mounting medium (Vector Laboratories) with DAPI to visualize nuclei.…”

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confidence: 99%

SKP2 Oncogene Is a Direct MYC Target Gene and MYC Down-regulates p27KIP1 through SKP2 in Human Leukemia Cells

Bretones

Acosta

Caraballo

et al. 2011

Journal of Biological Chemistry

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SKP2 is the ubiquitin ligase subunit that targets p27 KIP1(p27) for degradation. SKP2 is induced in the G 1 -S transit of the cell cycle, is frequently overexpressed in human cancer, and displays transformation activity in experimental models. Here we show that MYC induces SKP2 expression at the mRNA and protein levels in human myeloid leukemia K562 cells with conditional MYC expression. Importantly, in these systems, induction of MYC did not activate cell proliferation, ruling out SKP2 up-regulation as a consequence of cell cycle entry. MYC-dependent SKP2 expression was also detected in other cell types such as lymphoid, fibroblastic, and epithelial cell lines. MYC induced SKP2 mRNA expression in the absence of protein synthesis and activated the SKP2 promoter in luciferase reporter assays. With chromatin immunoprecipitation assays, MYC was detected bound to a region of human SKP2 gene promoter that includes E-boxes. The K562 cell line derives from human chronic myeloid leukemia. In a cohort of chronic myeloid leukemia bone marrow samples, we found a correlation between MYC and SKP2 mRNA levels. Analysis of cancer expression databases also indicated a correlation between MYC and SKP2 expression in lymphoma. Finally, MYC-induced SKP2 expression resulted in a decrease in p27 protein in K562 cells. Moreover, silencing of SKP2 abrogated the MYC-mediated down-regulation of p27. Our data show that SKP2 is a direct MYC target gene and that MYC-mediated SKP2 induction leads to reduced p27 levels. The results suggest the induction of SKP2 oncogene as a new mechanism for MYC-dependent transformation.c-MYC (hereafter MYC) is an oncogenic transcription factor of the helix-loop-helix/leucine zipper protein family. MYC exerts a wide array of biological functions in different cellular models related to cell cycle control, genomic instability, energetic metabolism, protein synthesis, intercellular communication, and control of cell differentiation (for reviews see Refs.

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Myc Inhibits p27-Induced Erythroid Differentiation of Leukemia Cells by Repressing Erythroid Master Genes without Reversing p27-Mediated Cell Cycle Arrest

Cited by 55 publications

References 57 publications

Down-regulation of Myc Is Essential for Terminal Erythroid Maturation

Down-regulation of Myc Is Essential for Terminal Erythroid Maturation

p27Kip1 represses transcription by direct interaction with p130/E2F4 at the promoters of target genes

SKP2 Oncogene Is a Direct MYC Target Gene and MYC Down-regulates p27KIP1 through SKP2 in Human Leukemia Cells

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