Basic helix-loop-helix (bHLH) transcription factors are sequence-specific DNA-binding proteins that regulate transcription. They are characterized by a 60 amino acid region comprising a basic DNA binding domain followed by a HLH motif formed from two amphipathic α-helices connected by a loop. bHLH transcription factors form homo- and hetero-dimeric complexes, which bind to a E box consensus sequence. (Adapted from PMID:15186484).