Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric transcription factor consisting of alpha and beta subunits. The levels of functional HIF-1 in the cell depends on the level of oxygen allowing cells to respond to hypoxic conditions. HIF-1α is a ubiquitously expressed protein containing an oxygen-dependent degradation domain that under normal conditions regulates its constant degradation. HIF-1 beta, on the other hand, is a stable constitutively expressed protein that localizes to the nucleus.
