The RUNX1 gene provides instructions for making a protein called runt-related transcription factor 1 (RUNX1). Like other transcription factors, the RUNX1 protein attaches (binds) to specific regions of DNA and helps control the activity of particular genes. This protein interacts with another protein called core binding factor beta or CBFβ (produced from the CBFB gene), which helps RUNX1 bind to DNA and prevents it from being broken down. Together, these proteins form one version of a complex known as core binding factor (CBF). The RUNX1 protein turns on (activates) genes that help control the development of blood cells (hematopoiesis). In particular, it plays an important role in development of hematopoietic stem cells, early blood cells that have the potential to develop into all types of mature blood cells such as white blood cells, red blood cells, and platelets.