Evidence for an enhanced transcription-dependent de novo synthesis of C/EBPbeta in the LPS activation of the chicken lysozyme gene.

C/EBPbeta has been shown to mediate the lipopolysaccharide (LPS)-induced expression of the lysozyme gene through enhanced binding to the -6.1-kb lysozyme enhancer. In this study, we describe the LPS regulation of the C/EBPbeta gene in myelomonocytic HD11 cells. Northern analysis showed that the steady state level of C/EBPbeta mRNA increased in response to LPS. The half life of C/EBPbeta mRNA of about 1 h in HD11 cells was not affected by exposure to LPS. Nuclear run-on transcription experiments with isolated nuclei revealed that the rate of C/EBPbeta gene transcription was enhanced by LPS, demonstrating that the C/EBPbeta gene in HD11 cells was regulated at the transcriptional level in response to LPS. Furthermore, the LPS-induced binding activity of C/EBPbeta to the -6.1-kb lysozyme enhancer was dependent not only on protein synthesis, but also on transcription. Thus, these results suggested that the LPS-induced binding activity to the -6.1-kb lysozyme enhancer in HD11 cells was regulated by an enhanced transcription-dependent de novo synthesis of C/EBPbeta.