IG/EBP (C/EBP-GAMMA) IS A TRANSDOMINANT NEGATIVE INHIBITOR OF C/EBP FAMILY TRANSCRIPTIONAL ACTIVATORS

摘要

Analysis of cDNA and genomic clones shows that the murine lg/EBP (C/EBP gamma) gene encodes a small protein with a predicted molecular weight of 16.4 kDa which contains C/EBP family basic and leucine zipper domains but lacks the transcriptional activation domains present in C/EBP (C/EBP alpha)and NF-IL6 (C/EBP beta). In transfection assays Ig/EBP is neither an activator nor a repressor of transcription; however, Ig/EBP inhibits the transcriptional ability of NF-IL6 (C/EBP beta) and C/EBP (C/EBP alpha), acting as a transdominant negative regulator, Thus Ig/EBP resembles LIP, another negative regulator of the C/EBP family, in both structure and transcriptional activity, Of the three known C/EBP family inhibitors, Ig/EBP, LIP and CHOP-10, only Ig/EBP is ubiquitously expressed. Therefore, Ig/EBP may act as a general buffer for C/EBP activators in many cell types.