CONTROL OF C-JUN ACTIVITY BY INTERACTION OF A CELL-SPECIFIC INHIBITOR WITH REGULATORY DOMAIN-DELTA - DIFFERENCES BETWEEN V-JUN AND C-JUN

Analysis of transcriptional activation properties of c-Jun chimeras in different cell lines suggests that it contains an activator domain (A1) that is negatively regulated by a cell type-specific inhibitor. A regulatory domain of c-Jun, δ, previously identified by in vitro experiments, also regulates transcriptional activation by c-Jun in vivo. The δ domain facilitates or stabilizes the interaction of the cellular inhibitor with A1. v-Jun, which lacks δ, is a stronger transcriptional activator than c-Jun, since its activity is not efficiently repressed by the cellular inhibitor. In vitro transcription with chimeric Jun proteins and extracts from different cell types confirms that the A1 and δ domains are repressed in a cell type-specific manner. These findings implicate a specific cellular factor in the negative regulation of c-Jun activity and suggest a molecular basis for the observed difference in transcriptional properties between v-Jun and c-Jun. © 1990.