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. 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. In additon,extracellular signals can induce post-translational modifications of JUN,resulting in altered transcriptional activity and target gene expression. 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.