title: Upregulation of the p53R2 ribonucleotide reductase subunit by nitric oxide.
abstract: The p53R2 ribonucleotide reductase subunit is a p53-inducible protein involved in DNA repair and mitochondrial DNA replication. It has been shown that p53 is activated by nitric oxide, which can damage DNA at high concentrations. This suggests that NO may regulate p53R2 expression through p53 activation. We show here that NO increases p53 protein expression in p53-wt cell lines and upregulates p53R2 at the protein and mRNA levels in a p53-dependent manner. Other p53 target genes, such as DDB2, WAF1 and PCNA, are also induced by NO. Surprisingly, p53R2 is similarly upregulated by NO in two p53-deficient cell lines, showing the existence of p53-independent regulatory mechanisms. Delta Np73, which is overexpressed in many cancers, inhibits the transcriptional activity of p53 and p53 homologs. In p53-wt cells, the Delta Np73alpha isoform inhibits basal and NO-induced p53R2 protein expression. In p53-null cells, it also strongly inhibits p53R2 expression, and represses the enhancer activity of the p53-responsive element present in the p53R2-encoding gene. These results demonstrate that p53R2 expression can be controlled by p53 homologs in the absence of p53, and is downregulated by oncogenic Delta Np73 isoforms. Knocking down p53R2 in p53-wt cells dramatically enhances NO-induced DNA damages, indicating a protective function of the p53R2 ribonucleotide reductase subunit in prevention or repair of NO-mediated genotoxic injury.
authors.affiliation: UMR CNRS 8619, Institute of Molecular and Cellular Biochemistry and Biophysics, University Paris Sud XI, F-91405 Orsay cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Guittet
authors.forename: Ali
authors.initials: A
authors.lastname: Tebbi
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Cottet
authors.forename: Françoise
authors.initials: F
authors.lastname: Vésin
authors.forename: Michel
authors.initials: M
authors.lastname: Lepoivre
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D018920:Coculture Techniques; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008264:Macrophages; D051379:Mice; D009569:Nitric Oxide / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000502:physiology; D020011:Protective Agents; D021122:Protein Subunits / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects; D012264:Ribonucleotide Reductases / Q000032:analysis / Q000235:genetics*; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D020011:Protective Agents; D021122:Protein Subunits; D012333:RNA, Messenger; C000606368:Trp73 protein, mouse; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C000606369:delta Np73 protein, human; D009569:Nitric Oxide; C405947:RRM2B protein, human; D012264:Ribonucleotide Reductases