Transcription factor JunD is a protein that in humans is encoded by the JUND gene. The protein encoded by this intronless gene is a member of the JUN family, and a functional component of the AP1 transcription factor complex. It has been proposed to protect cells from p53-dependent senescence and apoptosis. Alternate translation initiation site usage results in the production of different isoforms. The dominant negative mutant variant of JunD, known as ΔJunD or Delta JunD, is a potent antagonist of the ΔFosB transcript, as well as other forms of AP-1-mediated transcriptional activity. In the nucleus accumbens, ΔJunD directly opposes many of the neurological changes that occur in addiction (i.e., those induced by ΔFosB). ΔFosB inhibitors (drugs that oppose its action) may be an effective treatment for addiction and addictive disorders. Being an unnatural genetic variant, deltaJunD has not been observed in humans. JunD has been shown to interact with ATF3, MEN1, DNA damage-inducible transcript 3 and BRCA1.