title: The antiapoptotic DeltaNp73 is degraded in a c-Jun-dependent manner upon genotoxic stress through the antizyme-mediated pathway.
abstract: p73, the structural and functional homologue of p53, exists as two major forms: the transactivation-proficient, proapoptotic TAp73 or the transactivation-deficient, antiapoptotic DNp73. Expectedly, expression of both these major forms has to be coordinated precisely to achieve the desired cellular outcome. Genotoxic insults resulting in cell death lead to the stabilization of TAp73, mainly through posttranslational modifications, and the concomitant degradation of DNp73, through poorly understood mechanisms. We have therefore investigated the possible mechanisms of stress-induced DNp73 degradation and show here that c-Jun, the AP-1 family member activated by stress signals and involved in stabilizing TAp73, promotes DNp73 degradation. Genotoxic stress-mediated DNp73 degradation was found to occur in a c-Jun-dependent manner through a ubiquitin-independent but proteasome-dependent mechanism. Absence or down-regulation of c-Jun expression abrogated the reduction of DNp73 levels upon stress insults, whereas overexpression of c-Jun led to its degradation. c-Jun controlled DNp73 degradation through the nonclassical, polyamine-induced antizyme (Az) pathway by regulating the latter's processing during stress response. Consistently, expression of c-Jun or Az, or addition of polyamines, promoted DNp73 degradation, whereas silencing Az expression or inhibiting Az activity in cells exposed to stress reduced c-Jun-dependent DNp73 degradation. Moreover, Az was able to bind to DNp73. These data together demonstrate the existence of a c-Jun-dependent mechanism regulating the abundance of the antiapoptotic DNp73 in response to genotoxic stress.
authors.affiliation: Laboratory of Molecular Carcinogenesis, Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, Singapore.
authors.forename: Iqbal
authors.initials: I
authors.lastname: Dulloo
authors.forename: Ganesan
authors.initials: G
authors.lastname: Gopalan
authors.forename: Gerry
authors.initials: G
authors.lastname: Melino
authors.forename: Kanaga
authors.initials: K
authors.lastname: Sabapathy
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D015398:Signal Transduction; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011506:Proteins; D016755:Proto-Oncogene Proteins c-jun; C000606460:TP73 protein, human; C000606368:Trp73 protein, mouse; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; C000606369:delta Np73 protein, human; C031017:ornithine decarboxylase antizyme; D046988:Proteasome Endopeptidase Complex