Role of the Ets transcription factors in the regulation of the vascular-specific Tie2 gene

The Tie2 gene encodes a vascular endothelium-specific receptor tyrosine kin ase that is required for normal vascular development and is also upregulate d during angiogenesis, The regulatory regions of the Tie2 gene that are req uired for endothelium-specific gene expression in vivo have been identified , However, the transcription factors required for Tie2 gene expression rema in largely unknown. We have identified highly conserved binding sites for E ts transcription factors in the Tie2 promoter. Mutations in 2 particular bi nding sites lead to a 50% reduction in the endothelium-specific activity of the promoter. We have compared the ability of several members of the Ets f amily to transactivate the Tie2 promoter. Our results demonstrate that 1 of 3 distinct isoforms of the novel Ets transcription factor NERF, NERF2, is expressed in endothelial cells and can strongly transactivate the regulator y regions of the Tie2 gene in comparison to other Ets factors, which have l ittle or no effect. NERF2 can bind to the Tie2 promoter Ets sites in electr ophoretic mobility shift assays. These studies support a role for Ets facto rs in the regulation of vascular-specific gene expression and suggest that the novel Ets factor NERF2 may be a critical transcription factor in specif ying the expression of the Tie2 gene in vascular endothelial cells.