title: Human C/EBP-epsilon activator and repressor isoforms differentially reprogram myeloid lineage commitment and differentiation.
abstract: CCAAT enhancer-binding protein-epsilon (C/EBP-epsilon) is required for the terminal differentiation of neutrophils and eosinophils. Human C/EBP-epsilon is expressed as 4 isoforms (32, 30, 27, and 14 kDa) through differential RNA splicing, and alternative promoters and translational start sites. The C/EBP-epsilon(32/30) isoforms are transcriptional activators, whereas C/EBP-epsilon(27) interacts with and represses GATA-1 transactivation of eosinophil promoters. C/EBP-epsilon(14) contains only DNA-binding and -dimerization domains and may function as a dominant-negative regulator. To define functional activities for these C/EBP-epsilon isoforms in myelopoiesis, human CD34(+) progenitors were transduced with internal ribosomal entry site-enhanced green fluorescent protein retroviral vectors encoding the 32/30, 27, and 14-kDa isoforms, purified by fluorescence-activated cell sorter, and analyzed in colony-forming assays and suspension cultures. Progenitors transduced with C/EBP-epsilon(32/30) default exclusively to eosinophil differentiation and gene expression, independent of interleukin-5, and regardless of inclusion of cytokines to induce other lineages. In contrast, the putative repressor C/EBP-epsilon(27) isoform strongly inhibits eosinophil differentiation and gene expression, including GATA-1, promoting granulocyte (neutrophil)-macrophage differen-tiation. The C/EBP-epsilon(14) repressor isoform strongly inhibits eosinophil development and gene expression, promoting erythroid differentiation, an effect enhanced by erythropoietin. Thus, C/EBP-epsilon isoforms can reprogram myeloid lineage commitment and differentiation consistent with their predicted activities based on activator and repressor domains and in vitro functional activities.
authors.affiliation: Department of Biochemistry and Molecular Genetics, Section of Hematology-Oncology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607, USA.
authors.forename: Richa
authors.initials: R
authors.lastname: Bedi
authors.forename: Jian
authors.initials: J
authors.lastname: Du
authors.forename: Arun K
authors.initials: AK
authors.lastname: Sharma
authors.forename: Ignatius
authors.initials: I
authors.lastname: Gomes
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Ackerman
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D004804:Eosinophils / Q000166:cytology / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D038042:Myelopoiesis / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D020033:Protein Isoforms; D012097:Repressor Proteins; C070790:CEBPE protein, human