HYPOXIA REGULATORY ELEMENTS OF THE HUMAN VASCULAR ENDOTHELIAL GROWTH-FACTOR GENE

Vascular endothelial growth factor (VEGF) expression is highly stimula ted by hypoxia, both in vitro and in vivo. Recent findings suggest tha t the VEGF gene utilizes an oxygen sensing mechanism similar to the on e used by the erythropoietin gene. The genomic sequences that control the VEGF response to hypoxia are, however, largely unknown. In utilizi ng transient transfection assays in HeLa cells we determined that hypo xia/cobalt responsive enhancer elements are present at the 5' and 3' f lanking regions of the human VEGF gene. The 3' enhancer is contained i n a 160 bp fragment located about 60 bp downstream of the polyadenylat ion site. It contains a sequence stretch of about 12 bp which are high ly homologous to sequences in the erythropoietin hypoxia-responsive en hancer. The 5' flanking enhancer is contained in a 100 bp fragment loc ated about 800 bp upstream of the start site. This fragment does not c ontain significant homologies with the erythropoietin enhancer. Thus, it appears that the response to hypoxia of the VEGF gene is controlled by two regulatory elements; one which may be related to the erythropo ietin enhancer and a second, which appears to be a completely unrelate d sequence.