Expression and DNA-binding activity of C/EBP alpha and C/EBP beta in humanliver and differentiated primary hepatocytes

Background/Aims: Limited information is available on the expression and rol e of C/EBP factors in human liver and hepatocytes. We investigated the expr ession and DNA-binding activity of C/EBP alpha and C/EBP beta in human live r needle biopsies, surgical lobectomies and differentiated cultured hepatoc ytes derived from lobectomies. Methods: RNA and protein extracts were analyzed by RNAse protection, immuno blot and gel shift assays. Results: C/EBP mRNAs, isoforms and DNA-binding activities were low/undetect able in lobectomies. In contrast, several C/EBP alpha (47, 45, 35 and 33 kD a) and C/EBP beta isoforms (47, 43, 40, 35 and 21 kDa) were observed in nee dle biopsies. In cultured hepatocytes, the C/EBP expression pattern dramati cally changed with time. C/EBP alpha mRNA and the 45 kDa, isoform increased in parallel, reaching a maximum after 3-4 weeks coincident with weak DNA-b inding activity. C/EBP beta mRNA and isoform expression increased rapidly r eaching a plateau within 1-2 weeks; all C/EBP beta isoforms were phosphoryl ated. C/EBP beta exhibited greater DNA-binding activity than C/EBP alpha, a nd this activity paralleled C/EBP beta isoform expression. Conclusions: C/EBP isoforms exhibit markedly different expression patterns in lobectomies, needle biopsies and cultured hepatocytes. Stress stimuli du ring and/or after surgery for lobectomy resections may account for this dif ference. The pattern of C/EBP isoform expression in long-term highly differ entiated cultured hepatocytes is close to that observed in needle biopsies. (C) 2001 European Association for the Study of the Liver. Published by Els evier Science B.V. All rights reserved.