CCAAT/enhancer binding protein epsilon is preferentially up-regulated during granulocytic differentiation and its functional versatility is determined by alternative use of promoters and differential splicing.
CCAAT/enhancer binding protein (C/EBP) epsilon is a recently cloned member of the C/EBP family of transcription factors and is expressed exclusively in cells of hematopoietic origin. The human C/EBPepsilon gene is transcribed by two alternative promoters, Palpha and Pbeta. A combination of differential splicing and alternative use of promoters generates four mRNA isoforms, of 2.6 kb and 1.3-1.5 kb in size. These transcripts can encode three proteins of calculated molecular mass 32.2 kDa, 27.8 kDa, and 14.3 kDa. Accordingly, Western blots with antibodies specific for the DNA-binding domain, that is common to all forms, identify multiple proteins. C/EBPepsilon mRNA was greatly induced during in vitro granulocytic differentiation of human primary CD34(+) cells. Retinoic acid treatment of HL60 promyelocytic leukemia cells for 24 hr induced C/EBPepsilon mRNA levels by 4-fold, while prolonged treatment gradually reduced mRNA expression to pretreatment levels. Transient transfection experiments with expression vectors for two of the isoforms demonstrated that the 32.2-kDa protein is an activator of transcription of granulocyte colony-stimulating factor receptor promoter, while the 14.3-kDa protein is not. Thus, C/EBPepsilon is regulated in a complex fashion and may play a role in the regulation of genes involved in myeloid differentiation.
Yamanaka
R
R
Clinical Gene Therapy Branch, National Human Genome Research Institute, Building 10, Room 10C103, National Institutes of Health, Bethesda, MD 20892-1851, USA.
Kim
G D
GD
Radomska
H S
HS
Lekstrom-Himes
J
J
Smith
L T
LT
Antonson
P
P
Tenen
D G
DG
Xanthopoulos
K G
KG
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D002454:Cell Differentiation; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers; D005091:Exons; D006098:Granulocytes / Q000166:cytology / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D016350:Leucine Zippers; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000502:physiology; D009504:Neutrophils / Q000502:physiology; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D014162:Transfection
D022762:CCAAT-Enhancer-Binding Proteins; C489468:Cebpe protein, mouse; D017931:DNA Primers; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; C070790:CEBPE protein, human