Hypoxia-inducible factor 1 (HIF-1) allows cells to respond to changing levels of oxygen in the environment. HIF-1 is a heterodimeric transcription factor consisting of alpha and beta subunits. Under normal conditions HIF-1 alpha is continuously synthesized and degraded. HIF-1 alpha degradation is mediated through an oxygen-dependent degradation domain that is hydroxylated and leads to ubiquitylation and proteolysis. HIF-1 beta on the other hand is constitutively expressed and localizes to the nucleus.
