Ets transcription factor binding site is required for positive and TNF alpha-induced negative promoter regulation.

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RESUMO

Thrombomodulin (TM) is expressed on vascular endothelial cells and plays an important role in the anticoagulant pathway by maintaining the thrombo-resistance 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 (TNF alpha) through a protein kinase C independent pathway. The TM promoter is highly active in endothelial cells and is inhibited by TNF alpha. The -76/-56 region mediates both specific high basal activity and TNF alpha-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, TNF alpha 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 TNF alpha. c-Ets-1 competes and overrides TNF alpha 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 TNF alpha signalling cascade in endothelial cells.

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