title: An intact HDM2 RING-finger domain is required for nuclear exclusion of p53.
abstract: The p53 tumour-suppressor protein is negatively regulated by HDM2. Recent reports indicate that the leucine-rich nuclear-export sequence (NES) of HDM2 enables it to shuttle to the cytoplasm, and that this activity is required for degradation of p53. However, it is unclear whether HDM2 is involved in nuclear export of p53, partly because p53 has itself been shown to contain a functional NES within its tetramerization domain. Here we show that co-expression of HDM2 with green fluorescent protein (GFP)-tagged p53 causes redistribution of p53 from the nucleus to the cytoplasm of the cell. This activity is dependent on binding of p53 to HDM2, and requires an intact p53 NES, but is independent of the HDM2 NES. A mutant of the HDM2 RING-finger domain that is unable to ubiquitinate p53 does not cause relocalization of p53, indicating that ubiquitin ligation or other activities of this region of HDM2 may be necessary for its regulation of p53 localization.
authors.affiliation: MIT Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Massachusetts Avenue, Cambridge 02139, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Boyd
authors.forename: K Y
authors.initials: KY
authors.lastname: Tsai
authors.forename: T
authors.initials: T
authors.lastname: Jacks
mesh_terms: D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D051379:Mice; D016296:Mutagenesis; D009687:Nuclear Proteins; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism; D016335:Zinc Fingers
chemical_list: D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D014452:Ubiquitins; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2