Activation of protein kinase C decreases phosphorylation of c-Jun at sites that negatively regulate its DNA-binding activity.
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.
Boyle
W J
WJ
Molecular Biology and Virology Laboratory, Salk Institute, La Jolla, California 92037.
Smeal
T
T
Defize
L H
LH
Angel
P
P
Woodgett
J R
JR
Karin
M
M
Hunter
T
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D038341:Glycogen Synthase Kinases; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D009841:Oligonucleotides / Q000737:chemistry; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D009841:Oligonucleotides; D010750:Phosphoproteins; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D010768:Phosphoserine; D011494:Protein Kinases; D038341:Glycogen Synthase Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate