FIG. 2.

Tax 1 downregulates VEGF promoter activity. (a) Luciferase assays were carried out on lysates from 293T cells transfected with the full-length VEGF promoter construct PGL3-2.6 and incubated under normoxic and hypoxic conditions. The lower panel shows the expression level of HIF-1α in both conditions as determined by Western blotting. 293T (b), COS 7 (c), and HeLa (d) cells were cotransfected with PGL3-2.6 and the indicated concentrations of pCA-Tax1-HIS or empty pCA vector together with pRLTK, which was used as an internal control. Luciferase activity was quantified after 48 h and was normalized to thymidine kinase (TK) values. Basal activity was set at 100%. Differences in normalized luciferase activity between transfected and nontransfected cells were significant as determined by Student's t test. The lower panels in each figure show the levels of Tax 1 expression in lysates used for luciferase assays as determined by Western blotting.