c-Jun controls the efficiency of MAP kinase signaling by transcriptional repression of MAP kinase phosphatases.
The mammalian JNK signaling pathway regulates the transcriptional response of cells to environmental stress, including UV irradiation. This signaling pathway is composed of a classical MAP kinase cascade; activation results in phosphorylation of the transcription factor substrates c-Jun and ATF2, and leads to changes in gene expression. The defining components of this pathway are conserved in the fission yeast S. pombe, where the genetic studies have shown that the ability of the JNK homolog Spc1 to be activated in response to UV irradiation is dependent on the presence of the transcription factor substrate Atf1. We have used genetic analysis to define the role of c-Jun in activation of the mammalian JNK signaling pathway. Our results show that optimal activation of JNK requires the presence of its transcription factor substrate c-Jun. Mutational analysis shows that the ability of c-Jun to support efficient activation of JNK requires the ability of Jun to bind DNA, suggesting a transcriptional mechanism. Consistent with this, we show that c-Jun represses the expression of several MAP kinase phosphatases. In the absence of c-Jun, the increased expression of MAP kinase phosphatases leads to impaired activation of the ERK, JNK, and p38 MAP kinases after pathway activation. The results show that one function of c-Jun is to regulate the efficiency of signaling by the ERK, p38, and JNK MAP kinases, a function that is likely to affect cellular responses to many different stimuli.
Sprowles
Amy
A
Division of Hematology/Oncology and The UC Davis Cancer Center, Research Building III, Room 1100, 4645 2nd Avenue, Sacramento, CA 95817, USA.
Robinson
Dan
D
Wu
Yi-Mi
YM
Kung
Hsing-Jien
HJ
Wisdom
Ron
R
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D017874:Immediate-Early Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D037941:Silencer Elements, Transcriptional / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D016755:Proto-Oncogene Proteins c-jun; D012097:Repressor Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases