The PAI-1 Gene as a Direct Target of Endothelial PAS Domain Protein-1 in Adenocarcinoma A549 Cells

Endothelial PAS domain protein-1 (EPAS1) regulates transcription of the genes encoding erythropoietin and vascular endothelial growth factor, which are important for maintaining oxygen homeostasis. We have previously shown that plasminogen activator inhibitor-1 (PAI-1) gene expression is induced by hypoxia. In this study, we sought to determine whether PAI-1 gene expression is directly regulated by EPAS1 in cancer cells because activities of proteases and their inhibitors are tightly regulated for tumor invasion. Hypoxia increased the PAI-1 mRNA levels in human adenocarcinoma A549 cells. Overexpression of EPAS1 significantly increased the PAI-1 mRNA and protein levels. Transient transfection assays revealed that EPAS1 increased PAI-1 gene transcription through a sequence containing 5'-CACGTACA-3' located at -194 (we refer to it as site HREPAI-1) and GT-box located at -78. Electrophoretic gel mobility shift assays revealed that HREPAI-1 serves as a binding site for EPAS1, and Sp1 constitutively binds to GT-box. In conclusion, PAI-1 expression is induced by EPAS1 through HREPAI-1 and through an Sp1-binding site. These results indicate that the PAI-1 gene is a direct target of EPAS1 and suggest the role of EPAS1 and Sp1 in the hypoxic response of cancer cells.