Figure 1.

The hypoxia inducible factor (HIF) pathway. Under adequate oxygen pressure, prolyl-hydroxylase domain enzymes (PHDs) hydroxylate two prolyl residues on the α-subunit of the hypoxia-inducible transcription factors (HIF-α). The hydroxylated residues are recognized by the ubiquitin ligase Von Hippel–Lindau, leading to subsequent degradation of HIF-α via the proteasome (upper part of the figure). However, during hypoxia (deprived oxygen pressure), PHDs are inactive and HIF-α is able to translocate into the nucleus, interacts with the HIF-β subunit and P300/CBP enabling binding to hypoxia-responsive elements (HRE) in the promotor region of genes implicated in the hypoxia response (lower part of the figure).