C-JUN PHOSPHORYLATION IN SIGNAL-TRANSDUCTION AND GENE-REGULATION

This study analyzed the post-translational regulation of the transcrip tion factor AP-1 on the level of c-Jun phosphorylation. For this purpo se a new assay system employing a histidine-tag method of transient ex pression and rapid purification of recombinant c-Jun, in conjuction wi th <<southwestern>> blotting and in situ phosphatase treatment, was de veloped. It is demonstrated that the specific DNA-binding potential of c-Jun which is dependent on dephosphorylation can be modulated both b y extracellular and endogenous factors. Exposure of cells to phorbol e sters as well as artificially increasing the intracellular concentrati on of AP-1 target sites can stimulate the DNA-binding function of c-Ju n. These results indicate the existence of a novel cellular mechanism that serves to dynamically adjust the activity of c-Jun to the number of accessible responsive genes.