Hypoxia-Inducible Factor 1 (HIF-1) Pathway

Hypoxia-inducible factor 1 (HIF-1) is a basic helix-loop-helix-PAS domain transcription factor that is expressed in all metazoan organisms and is composed of HIF-1alpha and HIF-1beta subunits. Under hypoxic conditions, HIF-1 regulates the transcription of hundreds of genes in a cell type-specific manner. The HIF-1alpha subunit is regulated by O2-dependent hydroxylation of proline residue 402, 564, or both, by prolyl hydroxylase domain protein 2 (PHD2), which promotes binding of the von Hippel-Lindau protein (VHL), leading to ubiquitination and proteasomal degradation; and O2-dependent hydroxylation of asparagine residue 803 by factor inhibiting HIF-1 (FIH-1), which blocks the binding of the 300-kilodalton…