cJunAP1

cJunAP1, often written as c-Jun/AP-1, refers to the activator protein-1 transcription factor complex centered on the Jun family member c-Jun. AP-1 is a dimeric transcription factor formed by Jun and Fos family proteins, with c-Jun able to form homodimers or heterodimers with other AP-1 components such as c-Fos, FosB, Fra-1, or Fra-2.

AP-1 binds to the AP-1 recognition motif TGACTCA (and related sequences) in promoters and enhancers to regulate transcription in response to a wide range of stimuli, including growth factors, cytokines, stress, and oncogenic signals.

c-JunAP1 activity is regulated by phosphorylation and other post-translational modifications. MAP kinases, especially JNK, phosphorylate c-Jun on serine residues (notably Ser63 and Ser73), enhancing transcriptional activity. Dimer composition and cofactor recruitment further refine target gene selection.

Functionally, c-Jun/AP-1 controls genes involved in cell proliferation, differentiation, apoptosis, migration, and immune responses. It plays a role in development and tissue remodeling and can impact neuronal survival or death depending on cellular context.

Structurally, c-Jun contains an N-terminal transactivation domain and a C-terminal basic leucine zipper (bZIP) domain that mediates DNA binding and dimerization. Dimerization with Fos family members expands DNA-binding specificity and regulatory potential.

Dysregulation of AP-1 activity is implicated in cancer, fibrosis, and inflammatory diseases. Because of its central role in transducing diverse signals into gene expression changes, c-Jun/AP-1 remains a focus of basic research and drug development efforts.

See also: AP-1, JUN, FOS.