Transcription factor JunB is a member of the transcription factor activator protein (AP)-1 family, comprising Jun (c-Jun, JunB, and JunD), Fos (c-Fos, FosB, Fra1, and Fra2), ATF (ATFa, ATF-2 and ATF-3) and JDP (JDP-1 and JDP-2) family members []. They are basic leucine zipper transcription factors that play a central role in regulating gene transcription in various biological processes []. JunB may serve as a biomarkers for prognosis of breast cancer [].AP-1 proteins have a α-helical bZIP domain, which contains a basic DNA-binding region and regularly spaced leucine residues known as the leucine zipper motif []. They have similar protein structure and can either form homodimers or form heterodimers with other AP-1 proteins (predominantly with Jun proteins), which can then bind to TRE-like sequences (consensus sequence 5'-TGAG/CTCA-3') []. Each of these proteins are expressed in different tissues and can be regulated in different ways, which means that every cell type has a complex mixture of AP-1 dimers with subtly different functions [].
