Histone H1-like protein participates in endothelial cell-specific activation of the von Willebrand factor promoter.

A region of the von Willebrand factor (VWF) promoter has been identified that is necessary to confer endothelial cell-specific activation to the VWF promoter. This region spans sequences +155 to +247 and contains binding sites for GATA6 and NFY transcription factors. To identify potential DNA binding transcription factors that directly interact with these sequences in an endothelial-specific manner, we have performed extensive gel mobility assays with use of 7 overlapping DNA probes that collectively span this entire region. An endothelial-specific protein DNA complex was formed with an oligonucleotide that corresponded to sequences +155 to +184 of the VWF gene. Mutation analysis identified a 6-nucleotide element corresponding to sequences +164 to +169 as the core-binding region for the formation of this complex. Transfection analysis demonstrated that the mutation, which abolished DNA-protein interaction, resulted in significant inhibition of the VWF promoter activity. DNA pull-down analysis, mass spectrometry, and Western blot analysis demonstrated that a 32-kDa polypeptide with homology to histone H1 constituted the endothelial-specific DNA binding protein, or a DNA binding subunit of this protein complex. On the basis of these results, we hypothesize that an H1-like protein functions as an endothelial cell-specific transcriptional activator of the VWF promoter.