Transcriptional Regulation of the Tissue Factor Gene in Human Epithelial Cells Is Mediated by Sp1 and EGR-1

Tissue factor (TF) gene expression is rapidly induced in epithelial cells by phorbol 12-myristate 13-acetate and serum. We have shown that this induction is mediated by a novel serum response region (SRR) (111 to 14 bp) within the human TF promoter. In this study, we characterized cis-acting genetic elements within the SRR that regulated basal and inducible expression of the TF gene in HeLa cells. Gel mobility shift assays using oligonucleotides spanning the entire SRR identified three 12-base pair (bp) motifs within subregions 1, 2, and 3 that bound constitutively expressed Sp1 and inducibly expressed EGR-1. Analysis of protein binding to these 12-bp motifs by competition with Sp1 and EGR-1 sites, mutation, and antibody supershift experiments indicated that they each contained distinct EGR-1 and Sp1 sites that overlapped by 6 bp. Functional studies using HeLa cells transfected with plasmids containing the wild-type TF promoter (111 to 14 bp) or derivatives containing mutations in the three Sp1 and/or EGR-1 sites examined basal and inducible expression. The Sp1 sites mediated basal promoter activity, and both Sp1 and EGR-1 sites were required for maximal induction of the TF promoter by phorbol 12-myristate 13-acetate or serum. These data indicated that TF gene expression in HeLa cells was regulated by both Sp1 and EGR-1.