INTRAMOLECULAR SIGNAL-TRANSDUCTION IN C-JUN

The DNA-binding activity of c-Jun is determined by the phosphorylation state of a cluster of threonine and serine residues located near its COOH-terminus. We have analyzed the events that lead to c-Jun activati on via dephosphorylation of these sites in response to phorbol esters. Our results indicate that COOH-terminal dephosphorylation is an indir ect consequence of a separate phosphorylation event targeted to the NH 2-terminus of c-Jun. Thus, the activation of c-Jun DNA-binding potenti al, caused by COOH-terminal dephosphorylation, may not require the reg ulation of the kinase/phosphatase system that brings about this change , but rather an alteration in the accessibility of the COOH-terminal p hosphoacceptor sites of c-Jun.