Myogenic regulatory factors (MRF) are basic helix-loop-helix (bHLH) transcription factors that regulate myogenesis: MyoD, Myf5, myogenin, and MRF4.
These proteins contain a conserved basic DNA binding domain that binds the E box DNA motif. They dimerize with other HLH containing proteins through an HLH-HLH interaction.
References
Myogenic regulatory factors Wikipedia(Text) CC BY-SA