basic Helix-Loop-Helix-zipper (bHLHzip) domain found in basic helix-loop-helix domain-containing protein USF3 and similar proteins
USF3, also termed upstream transcription factor 3, is a bHLHzip protein that is involved in the negative regulation of epithelial-mesenchymal transition, the process by which epithelial cells lose their polarity and adhesion properties to become mesenchymal cells with enhanced migration and invasive properties.