MDM2 protein-mediated ubiquitination of numb protein: identification of a second physiological substrate of MDM2 that employs a dual-site docking mechanism.
The E3 ubiquitin ligase, MDM2, uses a dual-site mechanism to ubiquitinate and degrade the tumor suppressor protein p53, involving interactions with the N-terminal hydrophobic pocket and the acidic domain of MDM2. The results presented here demonstrate that MDM2 also uses this same dual-site mechanism to bind to the cell fate ... determinant NUMB with both the N-terminal hydrophobic pocket and the acidic domain of MDM2 also involved in forming the interaction with NUMB. Furthermore, the acidic domain interactions are crucial for MDM2-mediated ubiquitination of NUMB. Contrary to p53, where two separate domains form the interface with MDM2, only one region within the phosphotyrosine binding domain of NUMB (amino acids 113-148) mediates binding to both these regions of MDM2. By binding to both domains on MDM2, NUMB disrupts the MDM2-p53 complex and MDM2-catalyzed ubiquitination of p53. Therefore, we have identified the mechanism NUMB uses to regulate the steady-state levels of the p53 in cells. By targeting the acidic domain of MDM2 using acid domain-binding ligands we can overcome MDM2-mediated ubiquitination and degradation of NUMB impacting on the stabilization of p53 in cells. Furthermore, delivery of MDM2 acid domain-binding ligands to cancer cells promotes p53-dependent growth arrest and the induction of apoptosis. This highlights the dual-site mechanism of MDM2 on another physiological substrate and identifies the acid domain as well as N terminus as a potential target for small molecules that inhibit MDM2.
Mesh Terms:
Apoptosis, Binding Sites, Cell Line, Tumor, Cell Lineage, Cell Proliferation, Enzyme-Linked Immunosorbent Assay, Flow Cytometry, Humans, Ligands, Membrane Proteins, Nerve Tissue Proteins, Protein Binding, Protein Structure, Tertiary, Proto-Oncogene Proteins c-mdm2, Tumor Suppressor Protein p53, Ubiquitin, Ubiquitin-Protein Ligases, Ubiquitination
Apoptosis, Binding Sites, Cell Line, Tumor, Cell Lineage, Cell Proliferation, Enzyme-Linked Immunosorbent Assay, Flow Cytometry, Humans, Ligands, Membrane Proteins, Nerve Tissue Proteins, Protein Binding, Protein Structure, Tertiary, Proto-Oncogene Proteins c-mdm2, Tumor Suppressor Protein p53, Ubiquitin, Ubiquitin-Protein Ligases, Ubiquitination
J. Biol. Chem.
Date: Apr. 20, 2012
PubMed ID: 22337874
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