Dimerization and dissociation studies of the basic-helix-loop-helix transcription factors, E47 and Tal

The dimerization and DNA binding properties of the basic-helix-loop-helix (bHLH) domain of the transcription factors, E47 and Tal were evaluated utilizing a minimalistic, peptide based approach. The results from our studies indicated that contrary to literature precedent, the bHLH domain of Tal could dimerize efficiently. Mutant and fusion proteins were investigated to probe the lack of DNA binding by the Tal homodimer. The results indicated that the DNA binding basic region from Tal, when tethered to the dimerization domain of E47, was sufficient for DNA recognition. The methodologies developed in the course of this study allowed the development of a potent dissociative strategy to disrupt the dimerization and DNA binding abilities of E47 utilizing interfacial peptides. This study allowed for the identification of small peptides that adopted novel $\beta$-sheet secondary structures and inhibited the dimerization and DNA binding of E47 at equimolar concentrations. Furthermore, structure-activity studies established that the $\beta$-sheet characteristics of the interfacial peptides directly correlated with their inhibitory potential. This is perhaps the first example of a $\beta$-sheet peptide that directly interferes with the dimerization of a predominantly $\alpha$-helical protein.