REGULATION OF THE TISSUE FACTOR GENE IN HUMAN MONOCYTIC CELLS - ROLE OF AP-1, NF-KAPPA-B REL, AND SP1 PROTEINS IN UNINDUCED AND LIPOPOLYSACCHARIDE-INDUCED EXPRESSION/

Tissue factor (TF) expression by peripheral blood monocytes during sep sis initiates intravascular thrombosis. Bacterial lipopolysaccharide ( LPS) rapidly induces TF gene transcription in monocytes. The human TF promoter contains binding sites for the transcription factors AP-1, c- Rel/p65, Egr-1, and Sp1. NF-kappa B/Rel proteins have been shown to ph ysically interact with both AP-1 and Sp1 proteins. In this study, we i nvestigated the role of these transcription factors in uninduced and L PS-induced TF gene expression in human monocytic THP-1 cells. Deletion al analysis indicated that five Sp1 sites mediated basal expression in uninduced cells. The two AP-1 sites bound c-Fos/c-Jun heterodimers in both unstimulated and LPS-stimulated cells. Maximal LPS induction of the TF promoter required the two AP-1 sites and the kappa B site withi n the LPS response element. Disruption of the conserved spacing betwee n the proximal AP-1 site and the kappa B site abolished LPS induction. Replacement of the two AP-1 sites with intrinsically bent DNA partial ly restored LPS induction, suggesting an additional structural role fo r the AP-1 sites. Synergistic transactivation of the LPS response elem ent in Drosophila Schneider cells by coexpression of c-Fos, c-Jun, c-R el, and p65 or c-Jun and p65 required the transactivation domains of c -Jun and p65. These data indicated that c-Fos/c-Jun, c-Rel/p65, and Sp 1 regulate TF gene expression in human monocytic cells.