Transcription factor Jun (c-Jun) (c-Jun)

Transcription factor Jun (commonly known as **c-Jun**) is a key component of the activator protein 1 (**AP‑1**) transcription complex. It forms heterodimers with proteins from the Fos family (such as **c-Fos**, **FosB**, **Fra‑1**) via its basic region-leucine zipper (**bZIP**) domain. The AP‑1 complex binds specific DNA sequences known as AP‑1 sites (5'-TGAGTCA), regulating genes involved in critical cellular processes including differentiation, proliferation, apoptosis, and response to stress signals such as UV irradiation and cytokines. The activity of c‑Jun is tightly regulated by post-translational modifications—most notably phosphorylation by Jun N-terminal kinases (**JNKs**), which enhances its ability to activate gene expression programs linked with cell cycle progression and survival under stress conditions. Dysregulation or overactivation of c‑Jun/AP‑1 has been implicated in various human diseases—especially cancers—where it can drive uncontrolled growth through direct regulation of genes like cyclin D1. Because it integrates multiple signaling pathways at the level of gene regulation—and because aberrant activity contributes directly to disease phenotypes—it is considered an important therapeutic target despite challenges associated with drugging nuclear transcription factors directly.

Other names

Jun proto-oncogene, AP-1 transcription factor subunitAP-1 transcription factor subunit c-Junp39V-Jun avian sarcoma virus 17 oncogene homolog

Drugs or compounds that inhibit the JNK pathway reduce phosphorylation and activation of c-Jun, thereby decreasing its ability to regulate target gene expression involved in proliferation and survival. This can lead to reduced tumor growth or increased apoptosis in cancer cells.