Evolution of Myb Proteins

The Myb domain is a highly conserved 50 amino acid motif found in all eukaryotes and often in tandem repeats within a single protein. DNA binding proteins with three such repeats (3R) are present in animals, plants, fungi and protists. Invertebrate animals have a single 3R myb gene, whereas all vertebrates studied thus far have at least three such genes. The 3R myb genes of vertebrates arose by two duplications from a B-myb/Dm-myb-like ancestral gene. The first duplication appears to have resulted in a neomorphic paralogue with a central transactivation domain. This new gene then duplicated again to give rise to A-myb and c-myb. An examination of a wide variety of more distantly related Myb domain-containing proteins suggests that the most highly conserved function of the Myb domain may be interaction with chromatin proteins rather than with DNA.