title: Repression and coactivation of CCAAT/enhancer-binding protein epsilon by sumoylation and protein inhibitor of activated STATx proteins.
abstract: CCAAT/enhancer-binding protein epsilon (C/EBPepsilon) is a neutrophil-specific transcription factor whose activity is controlled by juxtaposed activating and regulatory domains. We previously determined that the function of the major regulatory domain (RD1) in C/EBPepsilon was dependent on the integrity of a five-amino acid motif that was identical to the recognition site for members of the small ubiquitin-like modifier (SUMO) family of ubiquitin-related proteins. We show here that the SUMO attachment site (the regulatory domain motif) is necessary and sufficient both for the intrinsic inhibitory function of RD1 and for coactivation by PIASxalpha and PIASxbeta, two members of the protein inhibitor of activated STAT (PIAS) family of SUMO E3 ligases. PIASxbeta was a more potent coactivator than PIASxalpha of both full-length C/EBPepsilon and fusion proteins containing the N-terminal portion of C/EBPepsilon, whereas PIASxalpha was more active on fusion proteins containing a heterologous activation domain. Two modes of coactivation were observed, one that was dependent on the integrity of the RING finger (RF) domain and was shared by both PIASxalpha and PIASxbeta and a second mode that was independent of the RF and was only observed with PIASxbeta. Sumoylation of C/EBPepsilon was enhanced by coexpression of PIASxalpha, suggesting that this modification is associated with the enhanced activity of the target protein. These results suggest that a complex interplay of accessory factors, including SUMO and PIAS proteins, modulates the activity of C/EBPepsilon.
authors.affiliation: Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
authors.forename: Jinyong
authors.initials: J
authors.lastname: Kim
authors.forename: Savitha
authors.initials: S
authors.lastname: Sharma
authors.forename: Yamin
authors.initials: Y
authors.lastname: Li
authors.forename: Everardo
authors.initials: E
authors.lastname: Cobos
authors.forename: Jorma J
authors.initials: JJ
authors.lastname: Palvimo
authors.forename: Simon C
authors.initials: SC
authors.lastname: Williams
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D005822:Genetic Vectors; D047468:Immunoprecipitation; D008025:Ligases / Q000378:metabolism*; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D050828:Protein Inhibitors of Activated STAT; D017434:Protein Structure, Tertiary; D025842:SUMO-1 Protein / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D044767:Ubiquitin-Protein Ligases
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C489468:Cebpe protein, mouse; D050828:Protein Inhibitors of Activated STAT; D025842:SUMO-1 Protein; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C476735:Pias2 protein, mouse