Figure 8. HIF-1a degradation in normoxia. HIF-1a is primarily degraded through two pathways. The first pathway utilizes prolyl hydroxylase enzymes to ubiquitinate HIF-1a for proteasomal degradation. The second pathway acts by hydroxylation of asparagine residues by FIH-1, preventing HIF-1a from interacting with co-activators (HIF-1b and CBP/p300) inside the nucleus. HIF-1a, hypoxia-inducible factor-1 alpha; FIH, factor inhibiting HIF-1; HIF-1b, hypoxia-inducible factor-1; CBP, CREB-binding protein; p300, E1A binding protein p300.