Myb

MYB refers to a family of transcription factors characterized by a conserved DNA-binding domain known as the MYB domain. These proteins are found across eukaryotes, including animals, plants, and fungi. The defining feature is the presence of one to three imperfect repeats (R1, R2, R3) within the domain, which form a helix-turn-helix structure that binds DNA. In plants, the most common form is the R2R3-MYB protein, which carries two repeats and represents the largest subfamily in many plant genomes.

In animals, several MYB family members play distinct roles in development and cell-cycle control. The best-known examples are c-Myb (the MYB proto-oncogene), A-Myb (MYBL1), and B-Myb (MYBL2). c-Myb regulates proliferation and differentiation of hematopoietic progenitor cells, and its misregulation is linked to leukemias. A-Myb is involved in meiosis and certain neural and reproductive tissues, while B-Myb is important for cell-cycle progression and is expressed in proliferating cells.

In plants, R2R3-MYB transcription factors regulate diverse processes, especially in development and metabolism. They control phenylpropanoid pathways that produce flavonoids, anthocyanins, and lignin, and they participate in responses to light and stress. Many plant MYBs operate as part of MBW protein complexes with basic helix-loop-helix (bHLH) and WD40 proteins to regulate target genes. Examples include MYB75 (PAP1), which activates anthocyanin biosynthesis, and various MYBs involved in trichome formation, stomatal development, and stress responses.

Evolutionarily, MYB genes are part of large, dynamic families generated by gene duplication and diversification. They remain a focus of study for understanding transcriptional networks and for potential applications in crop improvement and metabolic engineering.