LIPOPOLYSACCHARIDE INDUCTION OF TISSUE FACTOR EXPRESSION IN THP-1 MONOCYTIC CELLS - PROTEIN-DNA INTERACTIONS WITH THE PROMOTER

Tissue factor, the cellular receptor for factor VII/VIIa, activates both the intrinsic and extrinsic pathways of blood coagulation. In this analysis we have used DNase I footprinting to map the sites of protein-DNA interaction along the promoter (-383 to +8) using nuclear extracts prepared from uninduced and lipopolysaccharide-induced THP-1 cells. We have identified six regions that interact with nuclear factors in both uninduced and induced extracts. Four footprints are contained within a region reported to confer base-line high level expression and lipopolysaccharide and serum induction. Two additional footprints map to a region reported to reduce basal transcription by 50%. The only qualitative change in the footprint pattern with uninduced and induced extracts is the appearance of two hypersensitive sites with uninduced extracts. In addition, changes in the level of protein- DNA binding are detected with only one probe by DNA mobility shift analysis. A combination of well characterized transcription factors (AP1), primarily lymphoid cell specific regulatory proteins (NF-kappaB- and/or Ets-1-related proteins), as well as additional, uncharacterized proteins appear to interact with these sequences. Our data suggest that post-translational modification of existing transcription factors, and not induction of new DNA-binding activity, mediates the lipopolysaccharide induction of tissue factor synthesis in THP-1 cells.