ENDOTHELIAL-CELL-SPECIFIC REGULATION OF VON-WILLEBRAND-FACTOR GENE-EXPRESSION

In both tissue sections and cell culture, the endothelial nature of a cell is most commonly determined by demonstration of its expression of von Willebrand factor (vWf) protein and/or mRNA. Thus, the mechanism of cell-type-specific transcriptional regulation of the vWf gene is ce ntral to studying the basis of endothelial-cell-specific gene expressi on. In this study, deletion analyses were carried out to identify the region of the vWf gene which regulates its endothelial-cell-specific e xpression. A 734-bp fragment which spans the sequence from -487 to +24 7 relative to the transcription start site was identified as the cell- type-specific promoter. It consists of a minimal core promoter located between -90 and +22, a strong negative regulatory element located ups tream of the core promoter (ca. -500 to -300), and a positive regulato ry region located downstream of the core promoter in the first exon. T he activity of the core promoter is not cell type specific, and the ne gative regulatory region is required to inhibit its activity in all ce ll types. This positive regulatory region relieves this inhibition onl y in endothelial cells and results in endothelial-cell-specific gene e xpression. The positive regulatory region contains sequences predictin g possible SP1, GATA, and octamer binding sites. Mutations in either t he SP1 or octamer sequence have no effect on transcriptional activity, while mutation in the GATA binding element totally abolishes the prom oter activity. Evidence that a GATA factor is involved in this interac tion is presented. Thus, the positive regulatory region with an intact GATA binding site is required to overcome the inhibitory effect of th e negative regulatory element and activate vWf gene expression in an e ndothelial-cell-specific manner.