A cAMP response element and an Ets motif are involved in the transcriptional regulation of flt-1 tyrosine kinase (vascular endothelial growth factor receptor 1) gene

The fit-1 gene encodes a transmembrane tyrosine kinase, Fit-1, a receptor for vascular endothelial growth factor. The expression of fit-1 gene is restricted to endothelial cells in vivo, To understand the molecular mechanism underlying endothelial-specific expression of this gene, we studied the functional significance of transcriptional motifs in the 200-base pair region of the human fit-1 gene promoter, which has been identified to confer cell type specificity. By point mutation analysis using chloramphenicol acetyltransferase plasmids in 293E1 cells, which express significant levels of fit-1 mRNA, me found that an Ets motif, E4, at -54 to -51 and a cAMP response element (GRE) at -83 to -76 are involved in the transcriptional regulation of this gene, Disruption of either this GRE or E4 within the promoter sequence of 90 base pairs resulted in a decrease in chloramphenicol acetyltransferase activity of 90%, indicating that co-existence of both of CRE and Ets motif E4 is necessary for transcription of the fit-1 gene. Go-transfection of an expression vector containing c-ets-l, c-ets-2, or c-erg cDNA with this 90-base pair sequence yielded a 5-8-fold elevation of chloramphenicol acetyltransferase activity, further supporting the idea that Ets family protein(s) participates in the regulation of the fit-1 gene. Gel shift assays using nuclear extracts of 293E1 and endothelial cells demonstrated the existence of protein factor(s) that specifically binds to CRE and Ets motif E4, respectively. Taken together, our results strongly suggest cooperation of a GRE and an Ets motif for the function of the fit-1 gene promoter.