C/EBPα bypasses granulocyte colony-stimulating factor signals to rapidly induce PU.1 gene expression, stimulate granulocytic differentiation, and limit proliferation in 32D cl3 myeloblasts

Xinping Wang, Edward Scott, Charles L. Sawyers, Alan D. Friedman

Research output: Contribution to journalArticle

Abstract

Within hematopoiesis, C/EBPα is expressed only in myeloid cells, and PU.1 is expressed mainly in myeloid and B-lymphoid cells. C/EBPα-deficient mice lack the neutrophil lineage and retain monocytes, whereas PU.1-deficient mice lack monocytes and have severely reduced neutrophils. We expressed a C/EBPα-estrogen receptor ligand-binding domain fusion protein, C/EBPαWT- ER, in 32D cl3 myeloblasts. 32D cl3 cells proliferate in interleukin-3 (IL- 3) and differentiate to neutrophils in granulocyte colony-stimulating factor (G-CSF). In the presence of estradiol, C/EBPαWT-ER induced morphologic differentiation and the expression of the myeloperoxidase, lactoferrin, and G-CSF receptor mRNAs. C/EBPαWT-ER also induced a G1/S cell cycle block, with induction of p27 and Rb hypophosphorylation, bcr-abl(p210) prevented 32D cl3 cell differentiation. Activation of C/EBPα-ER in 32D-bcr-abl(p210) or Ba/F3 B-lymphoid cells induced cell cycle arrest independent of terminal differentiation. C/EBPαWT-ER induced endogenous PU.1 mRNA within 8 hours in both 32D cl3 and Ba/F3 cells, even in the presence of cycloheximide, indicating that C/EBPα directly activates the PU.1 gene. However, activation of a PU.1-ER fusion protein in 32D cl3 cells induced myeloperoxidase (MPO) RNA but not terminal differentiation. Thus, C/EBPα acts downstream of G-CSF and upstream of PU.1, p27, and potentially other factors to induce myeloblasts to undergo granulocytic differentiation and cell cycle arrest.

Original languageEnglish (US)
Pages (from-to)560-571
Number of pages12
JournalBlood
Volume94
Issue number2
DOIs
StatePublished - Jul 15 1999

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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