The HIF (hypoxia-inducible factor) transcription factor is a member of the basic-helix-loop-helix (bHLH) family of transcription factors and plays an important role in maintaining cellular oxygen homeostasis. HIF-1α has emerged as an important drug target in breast and prostate cancer, cardiovascular disease, and ischemia. Cayman's HIF-1αTranscription Factor Assay is a sensitive ELISA-based method for detecting HIF-1α DNA binding activity in nuclear extracts and whole cell lysates.