The protein families belongs to Jun (e.g., c-Jun, JunB, and JunD); Fos (e.g., c-Fos, FosB, Fra-1, and Fra-2); activating transcription factor (ATF) (e.g., ATF2 and LRFI/ATF3); and musculoaponeurotic fibrosarcoma (MAF) (e.g., c-Maf, MafB, MafA, MafG/F/K); whereby all groups bind to a common DNA site, namely AP-1 binding site [175]. The gene discussed is FOSB; the disease is fibrosarcoma.