 This causes "c-Myc" to be placed downstream of the highly active immunoglobulin (Ig) promoter region, leading to overexpression of "Myc".The protein product of "Myc" family genes all belong to the Myc family of transcription factors, which contain bHLH (basic helix-loop-helix) and LZ (leucine zipper) structural motifs.The bHLH motif allows Myc proteins to bind with DNA, while the leucine zipper TF-binding motif allows dimerization with Max, another bHLH transcription factor.