title: p73 Induces apoptosis via PUMA transactivation and Bax mitochondrial translocation.
abstract: p73, an important developmental gene, shares a high sequence homology with p53 and induces both G(1) cell cycle arrest and apoptosis. However, the molecular mechanisms through which p73 induces apoptosis are unclear. We found that p73-induced apoptosis is mediated by PUMA (p53 up-regulated modulator of apoptosis) induction, which, in turn, causes Bax mitochondrial translocation and cytochrome c release. Overexpression of p73 isoforms promotes cell death and bax promoter transactivation in a time-dependent manner. However, the kinetics of apoptosis do not correlate with the increase of Bax protein levels. Instead, p73-induced mitochondrial translocation of Bax is kinetically compatible with the induction of cell death. p73 is localized in the nucleus and remains nuclear during the induction of cell death, indicating that the effect of p73 on Bax translocation is indirect. The ability of p73 to directly transactivate PUMA and the direct effect of PUMA on Bax conformation and mitochondrial relocalization suggest a molecular link between p73 and the mitochondrial apoptotic pathway. Our data therefore indicate that PUMA-mediated Bax mitochondrial translocation, rather than its direct transactivation, correlates with cell death. Finally, human DeltaNp73, an isoform lacking the amino-terminal transactivation domain, inhibits TAp73-induced as well as p53-induced apoptosis. The DeltaNp73 isoforms seem therefore to act as dominant negatives, repressing the PUMA/Bax system and, thus, finely tuning p73-induced apoptosis. Our findings demonstrate that p73 elicits apoptosis via the mitochondrial pathway using PUMA and Bax as mediators.
authors.affiliation: Biochemistry Laboratory, Instituto Dermopatico Dell'Immacolata-Istituto di Ricovero e Cura a Carattere Scientifico, Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, 00133 Rome, Italy. gerry.melino@uniroma2.it
authors.forename: Gerry
authors.initials: G
authors.lastname: Melino
authors.forename: Francesca
authors.initials: F
authors.lastname: Bernassola
authors.forename: Marco
authors.initials: M
authors.lastname: Ranalli
authors.forename: Karen
authors.initials: K
authors.lastname: Yee
authors.forename: Wei Xing
authors.initials: WX
authors.lastname: Zong
authors.forename: Marco
authors.initials: M
authors.lastname: Corazzari
authors.forename: Richard A
authors.initials: RA
authors.lastname: Knight
authors.forename: Doug R
authors.initials: DR
authors.lastname: Green
authors.forename: Craig
authors.initials: C
authors.lastname: Thompson
authors.forename: Karen H
authors.initials: KH
authors.lastname: Vousden
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology; D015870:Gene Expression; D016147:Genes, Tumor Suppressor; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008156:Luciferases / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2; D012326:RNA Splicing; D015533:Transcriptional Activation; D014162:Transfection; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000502:physiology; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; C438378:BBC3 protein, human; C494827:Bax protein, mouse; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C000606460:TP73 protein, human; C000606368:Trp73 protein, mouse; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein; C000606369:delta Np73 protein, human; D045304:Cytochromes c; D008156:Luciferases