c-Fos-Knockdown HeLa Cell Lysate

c-FOS (encoded by the FOS gene) is a well-characterized proto-oncogene product and a core member of the basic leucine zipper (bZIP) transcription factor family. As a prototypical immediate-early gene (IEG), c-FOS is typically maintained at low basal levels in quiescent cells but undergoes rapid and transient induction in response to diverse extracellular cues—including growth factors, mitogens, cytokines, cellular stress, and membrane depolarization—primarily downstream of MAPK/ERK and Ca²⁺/CREB signaling cascades. Once expressed, c-FOS heterodimerizes with Jun-family proteins (such as c-Jun, JunB, and JunD) to form the functional Activator Protein-1 (AP-1) transcription factor complex, which binds to specific DNA consensus sequences (TPA response elements, TRE) to modulate gene expression networks controlling cell proliferation, differentiation, survival, apoptosis, and synaptic plasticity. In neuroscience, c-FOS induction is widely used as a robust surrogate marker for mapping cellular and neuronal activation. c-FOS antibodies are extensively employed in Western blotting, immunohistochemistry (IHC), immunofluorescence (IF), and chromatin immunoprecipitation (ChIP) to monitor immediate-early transcriptional activation, oncogenic signaling, and neural circuit activity. c-FOS knockout (KO) may impair canonical AP-1 transcriptional activity, attenuate mitogen-driven proliferation, alter differentiation trajectories, and diminish activity-dependent gene transcription in neurons; however, the overt cellular phenotype is strongly influenced by cell type, developmental stage, and compensatory upregulation of other Fos-family members (such as FOSB, FRA-1, or FRA-2).