Fig. 5. PHD2 controls HIF-1α stability upon re-oxygenation of hypoxic cells. HeLa cells transfected with siRNAs (200 nM) were incubated in normoxia (N; 20% O₂) or hypoxia (H; 1–2% O₂) for 4 h, after which hypoxic cells were returned to 20% O₂ for 0–180 min. Total cellular extracts were immunoblotted with the anti-HIF-1α antibody.