Functional NF-kappa B element in rabbit serum amyloid A gene and its role in acute phase induction.

Serum amyloid A (SAA) protein synthesis is highly induced in acute inflammatory conditions. Such induction process is primarily regulated at the transcriptional level and large amount of SAA mRNA has been found to accumulate in rabbit liver during acute inflammation. To identify the promoter element(s) involved in inducible transcription of SAA, a 5' flanking region of this gene has been fused to a reporter chloramphenicol acetyl transferase (CAT) gene and transfected into BNL liver cells. This DNA is capable of inducing synthesis of the reporter gene in response to lipopolysaccharide-stimulated monocyte-derived conditioned medium. Deletion analyses have shown that a region from -135 to -78 that contains a putative NF-kappa B element is responsible for the inducible function of the promoter. Gel shift assay has detected DNA-binding activity in the induced cells that appear to interact with the potential NF-kappa B element located within -112 to -78 of the SAA gene. Similar factor(s) have also been detected in the lipopolysaccharide-treated rabbit liver which is highly active in transcribing SAA mRNA. Appearance of these factors in acute-phase induced animals and their binding to the NF-kappa B-like element in the SAA proximal promoter region correlated with SAA mRNA synthesis suggests functional role of this promoter element in SAA gene expression under LPS-induced acute-phase condition.