title: Autoinhibition of MDMX by intramolecular p53 mimicry.
abstract: The p53 inhibitor MDMX is controlled by multiple stress signaling pathways. Using a proteolytic fragment release (PFR) assay, we detected an intramolecular interaction in MDMX that mechanistically mimics the interaction with p53, resulting in autoinhibition of MDMX. This mimicry is mediated by a hydrophobic peptide located in a long disordered central segment of MDMX that has sequence similarity to the p53 transactivation domain. NMR spectroscopy was used to show this hydrophobic peptide interacts with the N-terminal domain of MDMX in a structurally analogous manner to p53. Mutation of two critical tryptophan residues in the hydrophobic peptide disrupted the intramolecular interaction and increased p53 binding, providing further evidence for mechanistic mimicry. The PFR assay also revealed a second intramolecular interaction between the RING domain and central region that regulates MDMX nuclear import. These results establish the importance of intramolecular interactions in MDMX regulation, and validate a new assay for the study of intramolecular interactions in multidomain proteins with intrinsically disordered regions.
authors.affiliation: Departments of Molecular Oncology and.
authors.forename: Lihong
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Cell Biology, Microbiology, and Molecular Biology and Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33612.
authors.forename: Wade
authors.initials: W
authors.lastname: Borcherds
authors.affiliation: Departments of Molecular Oncology and.
authors.forename: Shaofang
authors.initials: S
authors.lastname: Wu
authors.affiliation: Chemical Biology Core, Moffitt Cancer Center, Tampa, FL 33612; and.
authors.forename: Andreas
authors.initials: A
authors.lastname: Becker
authors.affiliation: Drug Discovery.
authors.forename: Ernst
authors.initials: E
authors.lastname: Schonbrunn
authors.affiliation: Department of Cell Biology, Microbiology, and Molecular Biology and Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33612.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Daughdrill
authors.affiliation: Departments of Molecular Oncology and jiandong.chen@moffitt.org.
authors.forename: Jiandong
authors.initials: J
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014364:Tryptophan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D010455:Peptides; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D014364:Tryptophan; D051736:Proto-Oncogene Proteins c-mdm2
keywords: MDMX; acidic domain; intramolecular; p53; protease
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