Document Detail


C/EBPepsilon directly interacts with the DNA binding domain of c-myb and cooperatively activates transcription of myeloid promoters.
MedLine Citation:
PMID:  10233885     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
C/EBPepsilon is essential for granulocytic differentiation. We investigated the role of C/EBPepsilon in the transcriptional activation of various myeloid-specific genes. We found that two C/EBPepsilon isoforms, p32 and p30, possessing transcriptional activation domains were coexpressed in myeloid cells. Interestingly, isoform C/EBPepsilon p30 but not p32 was differentially upregulated in NB-4 promyelocytic leukemia cells treated with retinoids. Both isoforms bound specifically to C/EBP sites in myeloid promoters. The kd for C/EBPepsilon binding to the C/EBP site of the neutrophil elastase promoter was 4.2 nmol/L. In transfection assays using the nonhematopoietic cell line, CV-1, the p32 isoform activated promoters from the myeloid-specific mim-1, neutrophil elastase, and granulocyte colony-stimulating factor (G-CSF) receptor genes by 2.5-, 1.8-, and 1.6-fold, respectively. The p30 isoform lacked significant transcriptional activity, suggesting that other hematopoietic-specific factors were required for its function. Consistent with this prediction, transfections into the hematopoietic cell line Jurkat showed a 9.0- and 2.5-fold activation of the mim-1 promoter by the p32 and p30 isoforms, respectively. The additional 32 NH2-terminal residues made p32 a significantly more potent transcriptional activator than p30. T lymphoblasts (Jurkat cells) and immature myeloid cells (eg, Kcl22 cells) expressed high levels of the c-myb hematopoietic transcription factor. Cotransfection of c-myb with either the p32 or p30 isoform of C/EBPepsilon in CV-1 cells cooperatively transactivated the mim-1 promoter by 20- and 16-fold, respectively, and the neutrophil elastase promoter by 10-and 7-fold, respectively. Pulldown assays showed that each C/EBPepsilon isoform interacted directly with the DNA binding domain of the c-myb protein. Further studies showed that Kcl22 myeloid cells only contained active C/EBPepsilon, but not C/EBPalpha, C/EBPbeta, or C/EBPdelta. A mutation of the C/EBP site in the neutrophil elastase promoter markedly decreased the transactivation of the promoter in Kcl22 myeloblasts. These results demonstrate a role for C/EBPepsilon in regulating myeloid promoters, such as neutrophil elastase, probably through a direct interaction with c-myb.
Authors:
W Verbeek; A F Gombart; A M Chumakov; C Müller; A D Friedman; H P Koeffler
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Blood     Volume:  93     ISSN:  0006-4971     ISO Abbreviation:  Blood     Publication Date:  1999 May 
Date Detail:
Created Date:  1999-06-10     Completed Date:  1999-06-10     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7603509     Medline TA:  Blood     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  3327-37     Citation Subset:  AIM; IM    
Affiliation:
Division of Hematology/Oncology, Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine, Los Angeles CA, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Binding Sites
CCAAT-Enhancer-Binding Proteins*
COS Cells
Cell Nucleus / metabolism
Cloning, Molecular
DNA-Binding Proteins / metabolism
Genes, Reporter
Hematopoiesis / genetics*
Humans
Jurkat Cells
Leukocyte Elastase / genetics
Mice
Oncogenes
Promoter Regions, Genetic*
Protein Biosynthesis
Protein Isoforms / genetics,  metabolism
Proto-Oncogene Proteins / genetics*,  metabolism*
Proto-Oncogene Proteins c-myb
Recombinant Fusion Proteins / biosynthesis
Trans-Activators / genetics*,  metabolism*
Transcription Factors / genetics*,  metabolism*
Transcription, Genetic*
Transcriptional Activation
Transfection
U937 Cells
Chemical
Reg. No./Substance:
0/CCAAT-Enhancer-Binding Proteins; 0/Cebpe protein, mouse; 0/DNA-Binding Proteins; 0/Protein Isoforms; 0/Proto-Oncogene Proteins; 0/Proto-Oncogene Proteins c-myb; 0/Recombinant Fusion Proteins; 0/Trans-Activators; 0/Transcription Factors; 142805-41-2/CEBPE protein, human; EC 3.4.21.37/Leukocyte Elastase

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