Myb proto-oncogene protein is a member of the MYB (myeloblastosis) family of transcription factors. The protein contains three domains, an N-terminal DNA-binding domain, a central transcriptional activation domain and a C-terminal domain involved in transcriptional repression. This protein plays an essential role in the regulation of hematopoiesis and may play a role in tumorigenesis, including the regulation of miR-155 in B-cells.