title: TAp73 induction by nitric oxide: regulation by checkpoint kinase 1 (CHK1) and protection against apoptosis.
abstract: Nitric oxide (NO) is a potent activator of the p53 tumor suppressor protein, thereby inducing cell cycle arrest and apoptosis. However, little is known about the regulation of the two other p53-family members, p63 and p73, by nitrogen oxides. We report here an up-regulation of p73 by NO in p53-null K-562 leukemia cells. Chemical NO prodrugs or macrophage iNOS activity induced an accumulation of the TAp73α isoform in these cells, whereas macrophages from iNOS(-/-) mice did not. NO also up-regulated TAp73 mRNA expression, suggesting a transcriptional regulation. The checkpoint kinases Chk1 and Chk2 can regulate TAp73 induction after DNA damage. We show that these kinases were rapidly phosphorylated upon NO treatment. Genetic silencing or pharmacological inhibition of Chk1 impaired NO-mediated accumulation of TAp73α. Because NO is known to block DNA synthesis through ribonucleotide reductase inhibition, the up-regulation of TAp73α might be caused by DNA damage induced by an arrest of DNA replication forks. In support of this hypothesis, DNA replication inhibitors such as hydroxyurea and aphidicolin similarly enhanced TAp73α expression and Chk1 phosphorylation. Moreover, inhibition of Chk1 also prevented TAp73α accumulation in response to replication inhibitors. The knockdown of TAp73 with siRNA sensitized K-562 cells to apoptosis induced by a nitrosative (NO) or oxidative (H(2)O(2)) injury. Therefore, TAp73α has an unusual cytoprotective role in K-562 cells, contrasting with its pro-apoptotic functions in many other cell models. In conclusion, NO up-regulates several p53 family members displaying pro- and anti-apoptotic effects, suggesting a complex network of interactions and cross-regulations between NO production and p53-related proteins.
authors.affiliation: From the Université Paris-Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, F-91405 Orsay, France,; CNRS, F-91405 Orsay, France, and; the Division of Endocrinology, Diabetes, and Metabolism, Department of Molecular Medicine, University of Utah School of Medicine, Salt Lake City, Utah 84112.
authors.forename: Ali
authors.initials: A
authors.lastname: Tebbi
authors.affiliation: From the Université Paris-Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, F-91405 Orsay, France,; CNRS, F-91405 Orsay, France, and.
authors.forename: Olivier
authors.initials: O
authors.lastname: Guittet
authors.affiliation: From the Université Paris-Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, F-91405 Orsay, France,; CNRS, F-91405 Orsay, France, and.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Cottet
authors.affiliation: From the Université Paris-Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, F-91405 Orsay, France,; CNRS, F-91405 Orsay, France, and.
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Vesin
authors.affiliation: From the Université Paris-Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, F-91405 Orsay, France,; CNRS, F-91405 Orsay, France, and. Electronic address: michel.lepoivre@u-psud.fr.
authors.forename: Michel
authors.initials: M
authors.lastname: Lepoivre
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D000071877:Checkpoint Kinase 1; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology*; D004261:DNA Replication / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D020014:K562 Cells; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C000606460:TP73 protein, human; C000606368:Trp73 protein, mouse; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D009569:Nitric Oxide; D004247:DNA; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse; D006918:Hydroxyurea