title: Protein partners of C/EBPepsilon.
abstract: CCAAT-enhancer binding protein-epsilon (C/EBPepsilon) is a nuclear transcription factor implicated in the regulation of terminal myeloid differentiation. Using a yeast two-hybrid screen, potential interaction partners of C/EBPepsilon involved in myeloid development were identified. C/EBPepsilon was found to associate with other C/EBP family members, including C/EBPepsilon and CHOP as well as other proteins that are known to contain a leucine-zipper protein interaction motif including CREB2, LDOC1, E6TP1, and AF-17. In addition, C/EBPepsilon demonstrated the potential for interaction with proteins that do not possess a leucine-zipper motif, including proteins that may be involved in sumoylation (protein inhibitor of activated STAT1 [PIAS1] and ubiquitin-conjugating enzyme E2I). As expected, the association of C/EBPepsilon with other C/EBP family members depends on the presence of a functional leucine-zipper motif. Mapping studies of C/EBPepsilon with PIAS1 (as an example of a nonleucine-zipper-containing protein) showed that C/EBPepsilon interacts with the amino-terminal domain of PIAS1. The function of C/EBPepsilon interacting proteins was further investigated. Co-expression of C/EBPepsilon with C/EBPdelta resulted in potent transactivation in a lactoferrin reporter system. A gel mobility shift assay suggests that C/EBPepsilon, C/EBPalpha, and C/EBPdelta proteins can bind as heterodimers to a C/EBP consensus DNA-binding site. As CHOP is known to represent a transcriptional repressor, the functional interaction between C/EBPepsilon and CHOP was investigated. Co-expression of C/EBPepsilon and c-Myb with CHOP caused marked transcriptional repression of target reporter genes. Our results suggest heterodimeric partners of C/EBPepsilon modulate the function of C/EBPepsilon in mediating gene transcription during myelopoiesis.
authors.affiliation: Division of Hematology/Oncology, Cedars-Sinai Medical Center, UCLA School of Medicine, Los Angeles, Calif. 90048, USA.
authors.forename: Doris Y
authors.initials: DY
authors.lastname: Chih
authors.forename: Dorothy J
authors.initials: DJ
authors.lastname: Park
authors.forename: Mitchell
authors.initials: M
authors.lastname: Gross
authors.forename: Gregory
authors.initials: G
authors.lastname: Idos
authors.forename: Peter T
authors.initials: PT
authors.lastname: Vuong
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Hirama
authors.forename: Alexey M
authors.initials: AM
authors.lastname: Chumakov
authors.forename: Jonathan
authors.initials: J
authors.lastname: Said
authors.forename: H Phillip
authors.initials: HP
authors.lastname: Koeffler
mesh_terms: D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D019169:Jurkat Cells; D007781:Lactoferrin / Q000235:genetics / Q000378:metabolism; D038042:Myelopoiesis / Q000235:genetics / Q000502:physiology*; D011485:Protein Binding / Q000502:physiology; D050828:Protein Inhibitors of Activated STAT; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C106529:PIAS1 protein, human; D050828:Protein Inhibitors of Activated STAT; D025841:Small Ubiquitin-Related Modifier Proteins; D014157:Transcription Factors; D044763:Ubiquitin-Conjugating Enzymes; D007781:Lactoferrin; D000098843:Ubiquitin-Conjugating Enzyme UBC9