RTEF-1, a Novel Transcriptional Stimulator of Vascular Endothelial Growth Factor in Hypoxic Endothelial Cells.

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor known to be up-regulated in ischemic heart and hypoxic endothelial cells. However, the transcriptional regulation of VEGF in hypoxia-induced angiogenesis is not fully understood. Transcriptional enhancer factor-1 (TEF-1) is a transcriptional factot family that can regulate many genes expressed in cardiac and skeletal muscle cells by binding to myocytespecific chloramphenicol acetyltransferase heptamer elements in the promoters of these genes. In this study, we demonstrated that related TEF-1 (RTEF-1), a membet of the TEF-1 family, is up-regulated in hypoxic endothelial cells. Overexpression of RTEF-1 increases VEGF promoter activity and VEGF expression. Sequential deletion and site-directed mutation analyses of the VEGF promoter demonstrated that a GC-rich region containing four Spl response elements, located between -114 and -50, was essential for RTEF-1 function. This region is beyond the hypoxia-inducible factor-lα binding site and does not consist of M-CAT-related elements. By electrophoretic mobility shift assay, RTEF-1 was 'found to interact with the first Spl residue (-97 to -87) of the four consecutive Spl elements. Binding activity of RTEF-1 to VEGF promoter is also confirmed by chromatin immunoprecipitation. In addition, induction of VEGF promoter activity by RTEF-1 results in an increase of angiogenic processes including endothelial cells proliferation and vascular structure formation. These results indicate that RTEF-1 acts as a transcriptional stimulator of VEGF by regulating VEGF promoter activity through binding to Spl site. In addition, RTEFl-induced VEGF promoter activity was enhanced in a hypoxic condition, indicating that RTEF-1 may play an important role in the regulation of VEGF under hypoxia. [ABSTRACT FROM AUTHOR]