HIF-1β, or Hypoxia-Inducible Factor 1 Beta, is a protein that plays a crucial role in the body's response to low oxygen levels, known as hypoxia. It is part of a larger complex that helps cells adapt to changing oxygen availability by regulating the expression of various genes involved in processes like metabolism, angiogenesis, and cell survival. This protein works alongside HIF-1α, another subunit of the HIF complex, to form a functional transcription factor. Together, they activate genes that promote the formation of new blood vessels and enhance the ability of cells to utilize oxygen efficiently, which is vital for maintaining tissue health and function under stress conditions.