Modification of CCAAT/enhancer-binding protein-beta by the small ubiquitin-like modifier (SUMO) family members, SUMO-2 and SUMO-3.
CCAAT/enhancer-binding protein-beta (C/EBP beta) activator isoforms, C/EBP beta-1 and C/EBP beta-2, differ by only 23 amino acids in the human; however, evidence is accumulating that these transcription factors are functionally distinct. Here we demonstrate that C/EBP beta-1, but not C/EBP beta-2, is conjugated to the small ubiquitin-like modifier (SUMO) family members, SUMO-2 and SUMO-3 despite the fact that the SUMO target consensus is present in both isoforms of this transcription factor. This conjugation is dependent on the integrity of the extreme N terminus of C/EBP beta-1 and requires lysine 173 in the human protein. Furthermore, mutation of this lysine relieves the repression of the cyclin D1 promoter by C/EBP beta-1 without altering the subnuclear localization of C/EBP beta-1. The sumoylation of C/EBP beta-1 is likely to be important in the functional differences observed between C/EBP beta-1 and C/EBP beta-2.
Eaton
Erin M
EM
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Sealy
Linda
L
D016475:3T3 Cells; D000409:Alanine / Q000737:chemistry; D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics* / Q000378:metabolism*; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D019938:Cyclin D1 / Q000235:genetics; D005822:Genetic Vectors; D006801:Humans; D008239:Lysine / Q000737:chemistry; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D025841:Small Ubiquitin-Related Modifier Proteins / Q000502:physiology*; D014162:Transfection; D014452:Ubiquitins / Q000502:physiology*
D022782:CCAAT-Enhancer-Binding Protein-beta; D020033:Protein Isoforms; C117909:SUMO2 protein, human; C492189:SUMO3 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; C117908:Sumo3 protein, mouse; D014452:Ubiquitins; D019938:Cyclin D1; D008239:Lysine; D000409:Alanine