Transcriptional Activator Myb (c-Myb)

The c-Myb protein is a DNA-binding transcriptional regulator with a highly conserved DNA-binding domain composed of three ‘Myb repeats’ resembling consecutive homeodomain-like or helix–turn–helix-like motifs. The proto-oncoprotein c-Myb is the normal counterpart to the oncogenic v-Myb proteins expressed by two avian leukemia viruses, avian myeloblastosis virus and E26. Both viruses induce acute myeloid leukemias in birds and transform immature myeloid cells in tissue culture. In birds and mice, the c-myb gene is a common target for retroviral insertions leading to myeloid and lymphoid tumors. Interestingly, transgenic overexpression of normal c-Myb does not induce tumors in mice, although transgenic v-Myb can induce leukemias after a long latency, indicating that v-Myb-induced leukemogenesis requires additional secondary mutations.