title: Mdm2-mediated NEDD8 modification of TAp73 regulates its transactivation function.
abstract: Mutations in p73 are rare in cancer. Emerging evidence suggests that the relative expression of various p73 isoforms may contribute to tumorigenesis. Alternative promoters and N-terminal splicing result in the transcription and processing of either full-length (TA) or N-terminally truncated (deltaN) p73 isoforms. TAp73 possesses pro-apoptotic functions, while deltaNp73 has anti-apoptotic properties via functional inhibition of TAp73 and p53. Here, we report that TAp73, but not deltaNp73, is covalently modified by NEDD8 under physiologic conditions in an Mdm2-dependent manner. Co-expression of NEDP1, a cysteine protease that specifically cleaves NEDD8 conjugates, was shown to deneddylate TAp73. In addition, blockage of the endogenous NEDD8 pathway increased TAp73-mediated transactivation of p53- and p73-responsive promoter-driven reporter activity, and in conjunction, neddylated TAp73 species were found preferentially in the cytoplasm. These results suggest that Mdm2 attenuates TAp73 transactivation function, at least in part, by promoting NEDD8-dependent TAp73 cytoplasmic localization and provide the first evidence of a covalent post-translational modification exclusively targeting the TA isoforms of p73.
authors.affiliation: Cancer Research Program and Division of Haematology-Oncology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Watson
authors.forename: Alvaro
authors.initials: A
authors.lastname: Blanch
authors.forename: Dan C C
authors.initials: DC
authors.lastname: Lin
authors.forename: Michael
authors.initials: M
authors.lastname: Ohh
authors.forename: Meredith S
authors.initials: MS
authors.lastname: Irwin
mesh_terms: D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D008156:Luciferases / Q000378:metabolism; D000075687:NEDD8 Protein; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000235:genetics; D011499:Protein Processing, Post-Translational; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D009687:Nuclear Proteins; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D014452:Ubiquitins; C000606369:delta Np73 protein, human; D008156:Luciferases; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D010450:Endopeptidases; C477008:SENP8 protein, human