title: p53 induces the expression of its antagonist p73 Delta N, establishing an autoregulatory feedback loop.
abstract: The p53 tumor suppressor protein activates transcription and induces cell death. A close homologue of p53, termed p73, is expressed in transactivating (TA) forms that induce growth arrest and apoptosis much like p53. However, the p73 gene contains a second promoter, giving rise to the expression of p73 Delta N, a species of p73 proteins that lack the N-terminal transactivation domain. We show here that the expression of p73 Delta N is induced by p53 on the mRNA and protein level. The promoter that regulates p73 Delta N expression in human cells was cloned and found to be activated by p53, as well as by p73TA, directly through a specific DNA element. The p73 Delta N proteins, that are thereby expressed, bound to p53-responsive promoter DNA, competed with p53 for DNA binding, antagonized the activation of transcription by p53, and prevented p53-induced cell death. In addition, a transcriptional repressor domain was identified within the splicing variant p73 Delta Nalpha. The combination of p73DeltaNalpha and mdm2 antagonized p53 more strongly than either p73Nalpha or mdm2 alone. Blocking endogenous p73 Delta N by a trans dominant fragment, or its removal by siRNA, increased the activity of a p53-responsive promoter in cells that contain a wild type p53 gene. Thus, the induction of p73 Delta N expression by p53 establishes an autoregulatory feedback loop that keeps the trigger of cell death under tight control.
authors.affiliation: Institut für Virologie, Philipps-Universität Marburg, Robert Koch Str. 17, 35037 Marburg, Germany.
authors.forename: Natalia N
authors.initials: NN
authors.lastname: Kartasheva
authors.forename: Ana
authors.initials: A
authors.lastname: Contente
authors.forename: Claudia
authors.initials: C
authors.lastname: Lenz-Stöppler
authors.forename: Judith
authors.initials: J
authors.lastname: Roth
authors.forename: Matthias
authors.initials: M
authors.lastname: Dobbelstein
mesh_terms: D017209:Apoptosis; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins; D025461:Feedback, Physiological; D016147:Genes, Tumor Suppressor; D006706:Homeostasis; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000502:physiology*; D025521:Tumor Suppressor Proteins
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins