Runt-related transcription factor 1 （RUNX1） also known as acute myeloid leukemia 1 protein （AML1） or core-binding factor subunit alpha-2 （CBFA2） is a protein that in humans is encoded by the RUNX1 gene. RUNX1 is a transcription factor that regulates the differentiation of hematopoietic stem cells into mature blood cells. In addition it plays a major role in the development of the neurons that transmit pain. It belongs to the Runt-related transcription factor （RUNX） family of genes which are also called core binding factor-α （CBFα）. RUNX proteins form a heterodimeric complex with CBFβ which confers increased DNA binding and stability to the complex.