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MEKK1/JNK signaling stabilizes and activates p53
S Y Fuchs1, V Adler, M R Pincus
1Ruttenberg Cancer Center, Mount Sinai School of Medicine, New York, NY 10029, USA.
Summary
The mitogen-activated protein kinase kinase kinase (MEKK1) activates Jun-NH2 kinase (JNK) signaling, stabilizing the tumor suppressor p53. This pathway enhances p53
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- The tumor suppressor p53 is crucial for cellular stress response.
- Jun-NH2 kinase (JNK) signaling is often induced by stress and interacts with p53.
- p53 stability is influenced by its association with JNK.
Purpose of the Study:
- To investigate the relationship between the JNK signaling pathway and p53 stability and activity.
- To elucidate how MEKK1 influences p53 levels and function.
Main Methods:
- Expression of constitutively active JNKK upstream kinase (DeltaMEKK1).
- Analysis of p53 levels, ubiquitination, and half-life.
- Site-directed mutagenesis of the JNK-binding site on p53.
- In vitro phosphorylation assays and assessment of p53-Mdm2 interactions.
- Measurement of p53 transcriptional activity and p53-dependent apoptosis.
Main Results:
- DeltaMEKK1 expression increased p53 levels by reducing its ubiquitination and prolonging its half-life.
- Mutations in the p53 JNK-binding region abrogated DeltaMEKK1-mediated stabilization.
- JNK phosphorylation of p53 inhibited Mdm2 binding, reduced p53 ubiquitination, and dissociated p53-Mdm2 complexes.
- DeltaMEKK1 enhanced p53 transcriptional activity and potentiated p53-dependent apoptosis.
Conclusions:
- MEKK1-JNK signaling plays a significant role in stabilizing p53.
- This pathway enhances p53's transcriptional activity and apoptotic function.
- MEKK1-JNK signaling is integral to the cellular stress response mediated by p53.