The family of inhibitor of differentiation (Id) proteins is a group of evolutionarily conserved
molecules, which play important regulatory roles in organisms ranging from Drosophila to
humans. Id proteins are small polypeptides harboring a helix-loop-helix (HLH) motif, which
are best known to mediate dimerization with other basic HLH proteins, primarily E proteins.
Because Id proteins do not possess the basic amino acids adjacent to the HLH motif
necessary for DNA binding, Id proteins inhibit the function of E protein homodimers, as well …