Fig. 2
From: Focusing on the hypoxia-inducible factor pathway: role, regulation, and therapy for osteoarthritis
Schematic diagram of the HIF-1 pathway. Under normal oxygen conditions, HIF-1α protein is hydroxylated by prolyl 4-hydroxylase (PHD) on proline residues and polyubiquitinated by von Hippel–Lindau protein (pVHL). In this case, it will be degraded by the 26S proteasome system. Under hypoxia, HIF-1α can enter the nucleus and form a transcription complex with HIF-1β subunits and then recruit coactivators (such as CBP/p300) to regulate the transcriptional activity of downstream genes. PHD, molecules containing proline-hydroxylase domain; Ub, ubiquitin; FIH, a novel protein that interacts with HIF-1alpha and VHL to mediate repression of HIF-1 transcriptional activity