FOS and fibrosarcoma: These genes participated in the IL-17 signaling pathway, osteoclast differentiation pathway, chemokine signaling pathway, viral protein interaction with cytokine and cytokine receptor pathway, etc. Activator protein 1 (AP-1), which was combined with Jun (c-Jun, JunB, and JunD), Fos (c-Fos, FosB, Fra-1, and Fra-2), activating transcription factor (Atf) and musculoaponeurotic fibrosarcoma (Maf) proteins to form homodimer or heterodimer is a dimeric leucine zipper (bZIP) transcription factor (23).