MYC Family Genes encode MYC Family Proteins, class III bHLH leucine zipper transcription factors having cellular proliferative and apoptotic roles. Dimerization via leucine zippers of MYC proteins with bHLH/lz proteins, such as MAX, is required for efficient DNA binding. Leucine zippers are present in many gene regulatory proteins, including CREB proteins, Jun/AP1 transcription factors, and FOS-type proteins, as well as MYC proteins. The periodically repeated leucine side chains extending from one alpha helix interdigitate with leucine residues of another alpha helix, facilitating coiled-coil dimerization; like charge repulsion in this region perturbs homodimer formation; heterodimers are promoted by opposing charge attractions. c-MYC transcription factor binds to CAC(GA)TG DNA sites. MYC sequences have been highly conserved throughout evolution, from Drosophila to vertebrates. (NCI) [ ]