Transcriptional activity of CCAAT/enhancer-binding proteins is controlled by a conserved inhibitory domain that is a target for sumoylation.
CCAAT/enhancer-binding proteins (C/EBPs) are basic region/leucine zipper transcription factors that function as regulators of cell growth and differentiation in numerous cell types. We previously localized transcriptional activation and inhibitory regions in one family member, C/EBP epsilon. Here we describe the further characterization of a C/EBP epsilon inhibitory domain termed regulatory domain I. We show that functionally related domains are present in C/EBP alpha, C/EBP beta, and C/EBP delta. These domains contain an evolutionarily conserved five-amino acid motif (the regulatory domain motif (RDM)) that conforms to the consensus sequence (I/V/L)KXEP. Mutagenesis studies revealed that the residues at positions 1, 2, and 4 of the RDM are critical for inhibitory domain function. Data base searches identified RDM-like sequences in a number of nuclear proteins. We found that small regions from c-Jun, JunB, and JunD containing this sequence also function as transcriptional inhibitory domains. Importantly, the RDM is similar to the recognition sequence for attachment of the ubiquitin-like protein, small ubiquitin-like modifier-1 (SUMO-1), and the conserved lysine residue of each C/EBP RDM served as an attachment site for SUMO-1. SUMO-1 attachment decreased the inhibitory effect of the C/EBP epsilon regulatory domain, suggesting that sumoylation may play an important role in modulating C/EBP epsilon activity as well as that of the other C/EBP family members.
Kim
Jinyong
J
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
Cantwell
Carrie A
CA
Johnson
Peter F
PF
Pfarr
Curt M
CM
Williams
Simon C
SC
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D017930:Genes, Reporter; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D022762:CCAAT-Enhancer-Binding Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D025842:SUMO-1 Protein