Tissue factor (TF) is a transmembrane glycoprotein that mediates cellular initiation of the coagulation serine protease cascades. Moreover, expression of TF in human atherosclerotic plaques is likely to play a significant role in the thrombotic complications associated with plaque rupture. In this study the complete murine TF gene, Cf-3, was isolated from mouse NIH 3T3 cells and was found to consist of six exons spanning about 11 kilobase pairs (kbp) of DNA. A major transcriptional start site was located 24 bp downstream of a TATA box. Cf-3 was mapped to chromosome 3 by analysis of an intersubspecies test cross. Conserved transcription factor-binding sites were identified by comparison of 5' flanking regions of the murine and human TF genes. A region of the TF promoter required for constitutive expression exhibited 85% identity in DNA sequence and included two conserved binding sites for Spl. Furthermore, two AP-1 sites and an NF-KB site were conserved in a 56-bp region necessary for transcriptional activation in response to bacterial lipoporysaccharide. These highly conserved regions of the TF promoter, which contain several binding sites for well-characterized transcription factors, are likely to be functionally important in the complex pattern of TF gene expression observed in a variety of cell types. 1 These proteins may share a common global architecture of binding domains based on the conservation of two pairs of cysteine residues.2 TF initiates the coagulation serine protease cascades by forming a complex with circulating factors VII/VIIa. 3Under normal circumstances TF is not expressed within the vasculature. However, TF expression can be rapidly induced in cultured peripheral blood monocytes and human umbilical vein endothelial cells in response to a variety of agonists, including bacterial lipoporysaccharide (LPS) and the inflammatory cytokines tumor necrosis factor-a (TNF-a) and interleukin-1 (IL-1). 4 -7 Activation of the coagulation protease cascades by