Regulated expression of three C/EBP isoforms during adipose conversion of 3T3-L1 cells

• Published in: Genes & development Vol. 5; no. 9; pp. 1538 - 1552
• Main Authors: ZHAODAN CAO, UMEK, R. M, MCKNIGHT, S. L
• Format: Journal Article
• Language: English
• Published: Cold Spring Harbor, NY Cold Spring Harbor Laboratory 01-09-1991
• Subjects: Adipose Tissue - cytology; Adipose Tissue - metabolism; Amino Acid Sequence; Animals; Base Sequence; Biological and medical sciences; Blotting, Northern; Blotting, Western; CCAAT-Enhancer-Binding Proteins; Cell Differentiation; Cell Line; Cloning, Molecular; DNA - metabolism; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - genetics; DNA-Binding Proteins - isolation & purification; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation; Leucine Zippers; Mice; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Nuclear Proteins - biosynthesis; Nuclear Proteins - genetics; Nuclear Proteins - isolation & purification; Sequence Alignment; Transcriptional Activation; Adipocyte; Molecular form; Transcription; Rodentia; Molecular interaction; Primary structure; Gel retardation technique; Cell differentiation; Gene expression; Biological activity; Vertebrata; Regulation(control); Mammalia; Mouse; DNA; Blotting assay; Molecular cloning; Transcription factor
• ISSN: 0890-9369; 1549-5477
• DOI: 10.1101/gad.5.9.1538

In an effort to identify protein factors that play a regulatory role in the differentiation of adipocytes, we have isolated two genes that encode polypeptides related to CCAAT/enhancer-binding protein (C/EBP; hereafter termed C/EBP alpha). The proteins encoded by these C/EBP-related genes, termed C/EBP beta and C/EBP delta, exhibit similar DNA-binding specificities and affinities compared with C/EBP alpha. Furthermore, C/EBP beta and C/EBP delta readily form heterodimers with one another as well as with C/EBP alpha. The transcriptional activating capacity of these two newly identified C/EBP isoforms was demonstrated by transient transfection experiments in which expression vectors encoding C/EBP beta and C/EBP delta were observed to induce transcription from the promoter of the serum albumin gene in cultured hepatoma cells. The mRNAs encoding C/EBP beta and C/EBP delta were detected in a number of tissues, most of which corresponded to sites of expression of C/EBP alpha. The expression pattern of C/EBP beta and C/EBP delta during adipose conversion of 3T3-L1 cells was examined by Western and Northern blotting assays. In contrast to the expression profile of the gene encoding C/EBP alpha, whose product is not detectable until the late phase of adipocyte differentiation, the c/ebp beta and c/ebp delta genes were actively expressed very early during adipocyte differentiation. Moreover, transcription of the c/ebp beta and c/ebp delta genes was observed to be induced directly by adipogenic hormones. The accumulation of C/EBP beta and C/EBP delta reached a maximal level during the first 2 days of differentiation and declined sharply before the onset of C/EBP alpha accumulation. The temporal pattern of expression of these three C/EBP isoforms during adipocyte differentiation may reflect the underpinnings of a regulatory cascade that controls the process of terminal cell differentiation.