The helix-loop-helix domain: a common motif for bristles, muscles and sex

Bioessays. 1991 Oct;13(10):493-8. doi: 10.1002/bies.950131002.


Three apparently unrelated developmental processes--mammalian myogenesis, the choice of neural fate and sex determination in Drosophila--are controlled by a common mechanism. Most of the genes governing these processes encode transcriptional factors that contain the helix-loop-helix (HLH) motif. This domain mediates the formation of homo- or heterodimers that specifically bind to DNA through a conserved basic region adjacent to the HLH motif. Dimers differ in their affinity for DNA and in their ability to activate transcription from HLH binding-site containing promoters. In addition, the activity of HLH proteins is inhibited by dimerization with another class of HLH proteins that lack a basic domain entirely or have an altered one. These structural properties provide a molecular mechanism to explain the synergistic and antagonistic functional relations among the HLH encoding genes that control several developmental pathways.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Drosophila / genetics
  • Female
  • Male
  • Mammals / genetics
  • Models, Structural
  • Molecular Sequence Data
  • Muscles / physiology*
  • Protein Conformation
  • Sequence Homology, Nucleic Acid
  • Sex Determination Analysis*
  • Transcription Factors / genetics*


  • Transcription Factors