HIF-1 suppression by ERβ is due to ARNT degradation. (a) Hep3B or MCF-7 cells in six-well plates were transfected with hERβ. At 36 h post-transfection, total protein extracts were immunoblotted as indicated. (b) HEK293 cells in 24-well plates were cotransfected with HRE-Luc reporter (0.5 μg) and hERβ (0.2 μg) or ARNT plasmid (0.1 or 0.2 μg) as indicated. At 24 h post-transfection, cells were incubated under hypoxic conditions for 24 h. After incubation, luciferase expression was determined. Values represent the mean ± S.D. (N = 3). **a P <0.005 vs. con; **b P <0.005 vs. Hypoxia; *c P <0.05 vs. Hypoxia+ERβ. All experiments were repeated at least three times.