title: The deubiquitinating enzyme USP2a regulates the p53 pathway by targeting Mdm2.
abstract: Mdm2 is an E3 ubiquitin ligase that promotes its own ubiquitination and also ubiquitination of the p53 tumour suppressor. In a bacterial two-hybrid screen, using Mdm2 as bait, we identified an Mdm2-interacting peptide that bears sequence similarity to the deubiquitinating enzyme USP2a. We have established that full-length USP2a associates with Mdm2 in cells where it can deubiquitinate Mdm2 while demonstrating no deubiquitinating activity towards p53. Ectopic expression of USP2a causes accumulation of Mdm2 in a dose-dependent manner and consequently promotes Mdm2-mediated p53 degradation. This differs from the behaviour of HAUSP, which deubiquitinates p53 in addition to Mdm2 and thus protects p53 from Mdm2-mediated degradation. We further demonstrate that suppression of endogenous USP2a destabilises Mdm2 and causes accumulation of p53 protein and activation of p53. Our data identify the deubiquitinating enzyme USP2a as a novel regulator of the p53 pathway that acts through its ability to selectively target Mdm2.
authors.affiliation: CR-UK Cell Transformation Research Group, Department of Surgery and Molecular Oncology, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.
authors.forename: Lauren F
authors.initials: LF
authors.lastname: Stevenson
authors.forename: Alison
authors.initials: A
authors.lastname: Sparks
authors.forename: Nerea
authors.initials: N
authors.lastname: Allende-Vega
authors.forename: Dimitris P
authors.initials: DP
authors.lastname: Xirodimas
authors.forename: David P
authors.initials: DP
authors.lastname: Lane
authors.forename: Mark K
authors.initials: MK
authors.lastname: Saville
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D010450:Endopeptidases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism; D043222:Ubiquitin Thiolesterase
chemical_list: D010455:Peptides; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D010450:Endopeptidases; C108665:USP2 protein, human; D043222:Ubiquitin Thiolesterase