Ets Motifs Are Necessary for Endothelial Cell–Specific Expression of a 723-bp Tie-2 Promoter/Enhancer in Hprt Targeted Transgenic Mice

Abstract
Objective— Tie-2 is an endothelial cell–specific receptor tyrosine kinase that is involved in the remodeling of blood vessels and angiogenesis. Our goal was to characterize Tie-2 promoter function as a means of providing insight into the mechanisms of endothelial cell–specific gene regulation. Methods and Results— When targeted to the Hprt locus of mice, a small Tie-2 promoter fragment (containing a 300-bp intronic enhancer coupled upstream to a 423-bp core promoter) (T-short) directed widespread endothelial cell expression in vivo. The T-short promoter contains 2 clusters of Ets sites, one in the first exon, the other in the intronic enhancer. In cultured endothelial cells, a combined mutation of the Ets motifs resulted in a significant reduction in promoter activity. Consistent with these results, the same Ets mutations resulted in a loss of detectable expression of the T-short promoter in all vascular beds with the notable exception of the brain. Conclusions— These results suggest that the T-short prom...

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