Identification of cis-Acting Sequences Responsible for Phorbol Ester Induction of Human Serum Amyloid A Gene Expression via a Nuclear Factor κB-Like Transcription Factor

Abstract

We have analyzed the 5′-flanking region of one of the genes coding for the human acute-phase protein, serum amyloid A (SAA). We found that SAA mRNA could be increased fivefold in transfected cells by treatment with phorbol 12-myristate 13-acetate (PMA). To analyze this observation further, we placed a 265-base-pair 5′ SAA fragment upstream of the reporter chloramphenicol acetyltransferase (CAT) gene and transfected this construct into HeLa cells. PMA treatment of these transient transfectants resulted in increased CAT expression. Nuclear proteins from PMA-treated HeLa cells bound to this DNA fragment, and methylation interference analysis showed that the binding was specific to the sequence GGGACTTTCC (between −82 and −91), a sequence previously described by R. Sen and D. Baltimore (Cell 46:705-716, 1986) as the binding site for the nuclear factor NFκB. In a cotransfection competition experiment, we could abolish PMA-induced CAT activity by using cloned human immunodeficiency virus long-terminal-repeat DNA containing the NFkB-binding sequence. The same long-terminal-repeat DNA containing mutant NFκB-binding sequences (G. Nabel and D. Baltimore, Nature [London] 326:711-713, 1987) did not affect CAT expression, which suggested that binding by an NFκB-like factor is required for increased SAA transcription.