Activation of protein kinase C decreases phosphorylation of c-Jun at sites that negatively regulate its DNA-binding activity

• Published in: Cell Vol. 64; no. 3; p. 573
• Main Authors: Boyle, W J, Smeal, T, Defize, L H, Angel, P, Woodgett, J R, Karin, M, Hunter, T
• Format: Journal Article
• Language: English
• Published: United States 08-02-1991
• Subjects: Amino Acid Sequence; Base Sequence; Calcium-Calmodulin-Dependent Protein Kinases; DNA Mutational Analysis; DNA-Binding Proteins - metabolism; Enzyme Activation; Glycogen Synthase Kinases; HeLa Cells; Humans; In Vitro Techniques; Molecular Sequence Data; Nuclear Proteins - metabolism; Oligonucleotides - chemistry; Phosphoproteins - metabolism; Phosphorylation; Phosphoserine - metabolism; Protein Binding; Protein Kinase C - metabolism; Protein Kinases - metabolism; Proto-Oncogene Proteins c-jun; Tetradecanoylphorbol Acetate - pharmacology; Transcription Factors - metabolism
• ISSN: 0092-8674
• DOI: 10.1016/0092-8674(91)90241-P

In resting human epithelial and fibroblastic cells, c-Jun is phosphorylated on serine and threonine at five sites, three of which are phosphorylated in vitro by glycogen synthase kinase 3 (GSK-3). These three sites are nested within a single tryptic peptide located just upstream of the basic region of the c-Jun DNA-binding domain (residues 227-252). Activation of protein kinase C results in rapid, site-specific dephosphorylation of c-Jun at one or more of these three sites and is coincident with increased AP-1-binding activity. Phosphorylation of recombinant human c-Jun proteins in vitro by GSK-3 decreases their DNA-binding activity. Mutation of serine 243 to phenylalanine blocks phosphorylation of all three sites in vivo and increases the inherent trans-activation ability of c-Jun at least 10-fold. We propose that c-Jun is present in resting cells in a latent, phosphorylated form that can be activated by site-specific dephosphorylation in response to protein kinase C activation.