ETS TRANSCRIPTION FACTOR-BINDING SITE IS REQUIRED FOR POSITIVE AND TNF-ALPHA-INDUCED NEGATIVE PROMOTER REGULATION

Thrombomodulin (TM) is expressed on vascular endothelial cells and plays an important role in the anticoagulant pathway by maintaining the thromboresistance of the blood vessel wall. We show that in primary human endothelial cells TM gene expression is repressed at the transcriptional level by Tumour necrosis factor (TNFalpha) through a protein kinase C independent pathway. The TM promoter is highly active in endothelial cells and is inhibited by TNFalpha. The -76/-56 region mediates both specific high basal activity and TNFalpha-repression. It binds a nuclear factor specific to endothelial cells, that appears to belong to the Ets-family by various criteria. The -76/-56 region contains three direct repeats of the ets-core sequence GGAA that are important for specific high basal activity, TNFalpha repression and trans-activation by expression of Ets-1 and 2. Although human Ets-1 (h-Ets-1) and chicken c-Ets-1 and 2 stimulate the TM promoter through the -76/-56 element, their activity is not suppressed by TNFalpha. c-Ets-1 competes and overrides TNFalpha repression in a concentration dependent manner. We propose that either a different member of the Ets domain protein family, or an Ets-associated co-factor, is the target of the TNFalpha signalling cascade in endothelial cells.