JUN is also named as c-Jun and AP1, belongs to the bZIP family and Jun subfamily. JUN, the most extensively studied protein of the activator protein-1 (AP-1) complex, is involved in numerous cell activities, such as proliferation, apoptosis, survival, tumorigenesis and tissue morphogenesis[PMID: 22180088]. JUN is a transcription factor that recognizes and binds to the enhancer heptamer motif 5'-TGA[CG]TCA-3'. It promotes activity of NR5A1 when phosphorylated by HIPK3 leading to increased steroidogenic gene expression upon cAMP signaling pathway stimulation. JUN is a basic leucine zipper (bZIP) transcription factor that acts as homo- or heterodimer, binding to DNA and regulating gene transcription[PMID: 9732876]. In additon, extracellular signals can induce post-translational modifications of JUN, resulting in altered transcriptional activity and target gene expression[PMID:8464713]. More over, it has uncovered multiple layers of a complex regulatory scheme in which JUN is able to crosstalk, amplify and integrate different signals for tissue development and disease. Jun is predominantly nuclear, ubiquitinated Jun colocalizes with lysosomal proteins[PMID: 15469925].