Induction of C/EBPO gene expression in mouse liver

Bacterial lipopdysaccharide (IPS) was used to induce an acute phase response (APR) in liver of young (4 mo) and aged (28 mo) male C57BI6 mice. The expression of C/EBP5, a member of a bZp family of transcription factors, was examined using northern and western analysis. C/EBPo mRNA is present at low levels in control 4 mo animals and is induced by IPS. Increased mRNA levels are seen by 30 min, peak at 3 hr, and approach control by 6 hr. This mRNA is detected in the polysome fraction and sediments with polysemes on sucrose gradients. Western analysis of isolated nuclear protein shows very little 28 kDa C/EBP8, and a cross-reacting peptide of 45 kDa which is induced by IPS, peaks at 30 min and declines very quickly. Analysis of polysome associated and cytoplasmic protein shows no 28 kDa in control, but 28 kDa peptide is detected after IPS induction. \Afestem analysis of nuclear protein from 28 mo control mice shows increased 28 kDa C/EBP5 compared to young and this form is induced with IPS. We conclude that although C/EBPô gene transcription is induced by IPS in young mice, and that this mRNA is translated, the protein is not transported to the nucleus to interact with target APR genes. In aged mice, however, C/EBPô expression is activated in the absence of LPS and the protein is capable of entering the nucleus.