Fos proto-oncogene, AP-1 transcription factor subunit (FOS (or c-Fos))

The Fos proto-oncogene, AP-1 transcription factor subunit encodes the nuclear phosphoprotein c-Fos, a member of the Fos family of transcription factors. It forms heterodimers with JUN family proteins via its leucine zipper domain to create the AP-1 complex, which binds specific DNA sequences at promoter/enhancer regions and regulates genes involved in cell growth, differentiation, survival, apoptosis, angiogenesis, and response to extracellular stimuli. Expression of c-Fos is rapidly induced by diverse signals including growth factors and stressors; it acts both as an activator and repressor depending on context. Dysregulation—especially overexpression—of c-Fos contributes significantly to oncogenic transformation across multiple cancer types through promotion of cell proliferation and invasion. The protein’s function is tightly controlled at multiple levels including rapid degradation via proteasome-mediated turnover.

Other names

c-FosProto-oncogene c-FosAP-1 transcription factor subunitFBJ murine osteosarcoma viral oncogene homolog

Drugs that affect FOS do so primarily by inhibiting upstream signaling pathways (e.g., MAPK/ERK), thereby reducing FOS gene expression or protein stability. Some anti-cancer strategies aim to disrupt dimerization with JUN proteins or block DNA binding of the AP-1 complex.