c-Myc is a critical target for c/EBPalpha in granulopoiesis.
CCAAT/enhancer binding protein alpha (C/EBPalpha) is an integral factor in the granulocytic developmental pathway, as myeloblasts from C/EBPalpha-null mice exhibit an early block in differentiation. Since mice deficient for known C/EBPalpha target genes do not exhibit the same block in granulocyte maturation, we sought to identify additional C/EBPalpha target genes essential for myeloid cell development. To identify such genes, we used both representational difference analysis and oligonucleotide array analysis with RNA derived from a C/EBPalpha-inducible myeloid cell line. From each of these independent screens, we identified c-Myc as a C/EBPalpha negatively regulated gene. We mapped an E2F binding site in the c-Myc promoter as the cis-acting element critical for C/EBPalpha negative regulation. The identification of c-Myc as a C/EBPalpha target gene is intriguing, as it has been previously shown that down-regulation of c-Myc can induce myeloid differentiation. Here we show that stable expression of c-Myc from an exogenous promoter not responsive to C/EBPalpha-mediated down-regulation forces myeloblasts to remain in an undifferentiated state. Therefore, C/EBPalpha negative regulation of c-Myc is critical for allowing early myeloid precursors to enter a differentiation pathway. This is the first report to demonstrate that C/EBPalpha directly affects the level of c-Myc expression and, thus, the decision of myeloid blasts to enter into the granulocytic differentiation pathway.
Johansen
L M
LM
Harvard Institutes of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA.
Iwama
A
A
Lodie
T A
TA
Sasaki
K
K
Felsher
D W
DW
Golub
T R
TR
Tenen
D G
DG
D000818:Animals; D001665:Binding Sites; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D002460:Cell Line; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D005786:Gene Expression Regulation; D006098:Granulocytes / Q000166:cytology*; D006801:Humans; D009504:Neutrophils / Q000166:cytology; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D020298:U937 Cells
C533431:Arid4a protein, mouse; D022763:CCAAT-Enhancer-Binding Protein-alpha; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D016271:Proto-Oncogene Proteins c-myc; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors