Gadd45 beta mediates the NF-kappa B suppression of JNK signalling by targeting MKK7/JNKK2.
NF-kappa B/Rel transcription factors control apoptosis, also known as programmed cell death. This control is crucial for oncogenesis, cancer chemo-resistance and for antagonizing tumour necrosis factor alpha (TNFalpha)-induced killing. With regard to TNFalpha, the anti-apoptotic activity of NF-kappa B involves suppression of the c-Jun N-terminal kinase (JNK) cascade. Using an unbiased screen, we have previously identified Gadd45 beta/Myd118, a member of the Gadd45 family of inducible factors, as a pivotal mediator of this suppressive activity of NF-kappa B. However, the mechanisms by which Gadd45 beta inhibits JNK signalling are not understood. Here, we identify MKK7/JNKK2--a specific and essential activator of JNK--as a target of Gadd45 beta, and in fact, of NF-kappa B itself. Gadd45 beta binds to MKK7 directly and blocks its catalytic activity, thereby providing a molecular link between the NF-kappa B and JNK pathways. Importantly, Gadd45 beta is required to antagonize TNFalpha-induced cytotoxicity, and peptides disrupting the Gadd45 beta/MKK7 interaction hinder the ability of Gadd45 beta, as well as of NF-kappa B, to suppress this cytotoxicity. These findings establish a basis for the NF-kappa B control of JNK activation and identify MKK7 as a potential target for anti-inflammatory and anti-cancer therapy.
Pubmed ID: 14743220 RIS Download
Amino Acid Sequence | Animals | Antigens, Differentiation | Apoptosis | Cells, Cultured | Enzyme Activation | Fibroblasts | Humans | JNK Mitogen-Activated Protein Kinases | MAP Kinase Kinase 7 | Mice | Mice, Knockout | Mitogen-Activated Protein Kinase Kinases | Mitogen-Activated Protein Kinases | Molecular Sequence Data | NF-kappa B | Peptides | Protein Binding | Sequence Alignment | Signal Transduction | Tumor Necrosis Factor-alpha