SP1 RECOGNITION SITES IN THE PROXIMAL PROMOTER OF THE HUMAN VASCULAR ENDOTHELIAL GROWTH-FACTOR GENE ARE ESSENTIAL FOR PLATELET-DERIVED GROWTH FACTOR-INDUCED GENE-EXPRESSION

Stimulation of NIH3T3 cells with platelet-derived growth factor (PDGF) -BB enhances expression of vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen and a key mediator of tumor angio genesis. Here, we identified cis-acting VEGF promoter elements and tra ns-acting factors which are involved in PDGF-stimulated VEGF expressio n. By 5'-deletion and transient transfection analysis, a G + C-rich re gion at -85 to -50 of the human VEGF promoter was shown to be necessar y and sufficient for both PDGF inducible and basal expression. The reg ion contains three potential recognition sites for Spl transcription f actors, which overlap with two Egr-1 sites. Mutations that abolish the ability of Spl to interact with the VEGF promoter element also abroga te expression induced by PDGF. Mutations of the potential Egr-1 bindin g sites did not affect PDGF responsiveness. Gel shift and antibody sup ershift analyses showed that Spl and Sp3 interact constitutively with the VEGF promoter element. Our data strongly suggest that enhanced VEG F gene expression in PDGF-induced NIH3T3 cells is mediated by Spl and/ or Sp3 transcription factors bound to the -85 to -50 promoter region o f the VEGF gene.