CCAAT/enhancer binding protein activates the promoter of the serum albumin gene in cultured hepatoma cells.
An expression vector capable of encoding full-length CCAAT/enhancer-binding protein (C/EBP) has been constructed and tested in transient transfection assays for its capacity to activate transcription from the promoter of the serum albumin gene. When tested in cultured hepatoma cells, the C/EBP expression vector achieved potent trans-activation of the albumin promoter. Less substantial activation was observed when the same experiment was conducted using cultured mouse fibroblasts. Expression vectors that encoded defective forms of C/EBP failed to activate the albumin promoter. Moreover, mutated variants of the albumin promoter that lack the C/EBP-binding site failed to be trans-activated. The data are consistent with the interpretation that C/EBP is a bona fide transcription factor. During the course of these experiments it was noted also that C/EBP is more than an order of magnitude less concentrated in cultured hepatoma cells than it is in adult liver cells. Given these findings, we speculate that C/EBP may play a general role in establishing and maintaining the differentiated, nonproliferative state.
Friedman
A D
AD
Howard Hughes Research Laboratories, Carnegie Institution of Washington, Department of Embryology, Baltimore, Maryland 21210.
Landschulz
W H
WH
McKnight
S L
SL
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D007739:L Cells; D008113:Liver Neoplasms / Q000473:pathology; D051379:Mice; D011401:Promoter Regions, Genetic; D051381:Rats; D012709:Serum Albumin / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D012709:Serum Albumin; D014157:Transcription Factors