Molecular evolution of the Myb family of transcription factors: evidence for polyphyletic origin

Abstract. The Myb family of proteins is a group of functionally diverse transcriptional activators found in both plants and animals that is characterized by a con-served DNA-binding domain of approximately 50 amino acids. Phylogenetic analyses of amino acid sequences of this family of proteins portray very disparate evolution-ary histories in plants and animals. Animal Myb proteins have diverged from a common ancestor, while plants appear related only within the DNA-binding domain. Re-sults imply a pattern of modular evolution of the Myb proteins centering on the possession of a helix-turn-helix motif. Based on this it is suggested that Myb proteins are a polyphyletic group related only by a ‘‘Myb-box’’ DNA-binding motif