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A p53-independent role for the MDM2 antagonist Nutlin-3 in DNA damage response initiation.

Valentine, JM; Kumar, S; Moumen, A (2011) A p53-independent role for the MDM2 antagonist Nutlin-3 in DNA damage response initiation. BMC CANCER, 11 (79). ISSN 1471-2407
SGUL Authors: Moumen, Abdeladim

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BACKGROUND: The mammalian DNA-damage response (DDR) has evolved to protect genome stability and maximize cell survival following DNA-damage. One of the key regulators of the DDR is p53, itself tightly regulated by MDM2. Following double-strand DNA breaks (DSBs), mediators including ATM are recruited to the site of DNA-damage. Subsequent phosphorylation of p53 by ATM and ATM-induced CHK2 results in p53 stabilization, ultimately intensifying transcription of p53-responsive genes involved in DNA repair, cell-cycle checkpoint control and apoptosis. METHODS: In the current study, we investigated the stabilization and activation of p53 and associated DDR proteins in response to treatment of human colorectal cancer cells (HCT116p53+/+) with the MDM2 antagonist, Nutlin-3. RESULTS: Using immunoblotting, Nutlin-3 was observed to stabilize p53, and activate p53 target proteins. Unexpectedly, Nutlin-3 also mediated phosphorylation of p53 at key DNA-damage-specific serine residues (Ser15, 20 and 37). Furthermore, Nutlin-3 induced activation of CHK2 and ATM - proteins required for DNA-damage-dependent phosphorylation and activation of p53, and the phosphorylation of BRCA1 and H2AX - proteins known to be activated specifically in response to DNA damage. Indeed, using immunofluorescent labeling, Nutlin-3 was seen to induce formation of γH2AX foci, an early hallmark of the DDR. Moreover, Nutlin-3 induced phosphorylation of key DDR proteins, initiated cell cycle arrest and led to formation of γH2AX foci in cells lacking p53, whilst γH2AX foci were also noted in MDM2-deficient cells. CONCLUSION: To our knowledge, this is the first solid evidence showing a secondary role for Nutlin-3 as a DDR triggering agent, independent of p53 status, and unrelated to its role as an MDM2 antagonist.

Item Type: Article
Additional Information: © 2011 Valentine et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: Animals, Cells, Cultured, DNA Damage, Gene Expression Regulation, Gene Knockdown Techniques, HCT116 Cells, Humans, Imidazoles, Mice, Models, Biological, Phosphorylation, Piperazines, Protein Stability, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins c-mdm2, Tumor Suppressor Protein p53, Science & Technology, Life Sciences & Biomedicine, Oncology, HUMAN P53, NEGATIVE REGULATION, IONIZING-RADIATION, ACTIVATION, PHOSPHORYLATION, ATM, STABILIZATION, APOPTOSIS, DEGRADATION, MUTATIONS
Journal or Publication Title: BMC CANCER
ISSN: 1471-2407
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21 February 2011Published
Web of Science ID: WOS:000288016100001
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