title: The MDM2 RING domain and central acidic domain play distinct roles in MDM2 protein homodimerization and MDM2-MDMX protein heterodimerization.
abstract: The oncoprotein murine double minute 2 (MDM2) is an E3 ligase that plays a prominent role in p53 suppression by promoting its polyubiquitination and proteasomal degradation. In its active form, MDM2 forms homodimers as well as heterodimers with the homologous protein murine double minute 4 (MDMX), both of which are thought to occur through their respective C-terminal RING (really interesting new gene) domains. In this study, using multiple MDM2 mutants, we show evidence suggesting that MDM2 homo- and heterodimerization occur through distinct mechanisms because MDM2 RING domain mutations that inhibit MDM2 interaction with MDMX do not affect MDM2 interaction with WT MDM2. Intriguingly, deletion of a portion of the MDM2 central acidic domain selectively inhibits interaction with MDM2 while leaving intact the ability of MDM2 to interact with MDMX and to ubiquitinate p53. Further analysis of an MDM2 C-terminal deletion mutant reveals that the C-terminal residues of MDM2 are required for both MDM2 and MDMX interaction. Collectively, our results suggest a model in which MDM2-MDMX heterodimerization requires the extreme C terminus and proper RING domain structure of MDM2, whereas MDM2 homodimerization requires the extreme C terminus and the central acidic domain of MDM2, suggesting that MDM2 homo- and heterodimers utilize distinct MDM2 domains. Our study is the first to report mutations capable of separating MDM2 homo- and heterodimerization.
authors: From the Department of Radiation Oncology, the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, and Curriculum in Genetics and Molecular Biology.
authors: Patrick L
authors: PL
authors: Leslie
authors: Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27514.
authors: Hengming
authors: H
authors: Ke
authors: From the Department of Radiation Oncology, the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, and Department of Pharmacology, and the Jiangsu Center for the Collaboration and Innovation of Cancer Biotherapy, Cancer Institute, Xuzhou Medical College, Xuzhou, Jiangsu 221002, China ypzhang@med.unc.edu.
authors: Yanping
authors: Y
authors: Zhang
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D006801:Humans; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000502:physiology
chemical_list: D018797:Cell Cycle Proteins; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2
keywords: RING finger protein 4 (RNF4); cancer; enzyme mechanism; mouse double minute 2 homolog (MDM2); p53