P53 stabilization and activation in response to stress is critical for its tumor suppressor function. DNA damage induces p53 accumulation by activating ATM. We recently identified multiple novel ATM phosphorylation sites near the RING domain of MDM2, an E3 ligase that promotes p53 ubiquitination. Mutational analyses showed that these sites act in a redundant fashion to regulate p53 stability after DNA damage. Blocking MDM2 phosphorylation prevents p53 stabilization after DNA damage. Phosphorylation of MDM2 specifically blocks p53 poly-ubiquitination but not mono- ubiquitination. We also found that MDM2 interacts with histone methyltransferases and induces p53 C terminal lysine methylation. Therefore, MDM2 is an important signaling target in ATM stabilization of p53. Furthermore, MDM2 regulates p53 transcriptional activity through novel mechanisms. The following experiments are proposed to further study the mechanisms of p53 activation during stress response. (1) Determine the mechanism of p53 stabilization by MDM2 phosphorylation after DNA damage. (2) Investigate the mechanism of p53 stabilization by MDM2-binding proteins during non-genotoxic stress. (3) Investigate the regulation of p53 activity by MDM2-mediated lysine methylation. (4) Test the in vivo function of MDM2 phosphorylation in p53 tumor suppression. These experiments will lead to better understanding of the novel mechanisms that activate p53, and are critical for developing novel strategies of targeting MDM2 in cancer.

Public Health Relevance

The proposal will study the regulation of the mdm2 oncoprotein and the mechanism of p53 inactivation by mdm2. The experiments are based on recent findings on the regulation of mdm2 activity by phosphorylation and histone methyltransferases. The experiments will also use mouse models to test the physiological functions of mdm2 phosphorylation. Understanding the mechanisms of mdm2 regulation may lead to new strategies to activate p53 in cancer cells.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA141244-03
Application #
8066461
Study Section
Tumor Cell Biology Study Section (TCB)
Program Officer
Watson, Joanna M
Project Start
2009-07-01
Project End
2014-04-30
Budget Start
2011-05-01
Budget End
2012-04-30
Support Year
3
Fiscal Year
2011
Total Cost
$336,129
Indirect Cost
Name
H. Lee Moffitt Cancer Center & Research Institute
Department
Type
DUNS #
139301956
City
Tampa
State
FL
Country
United States
Zip Code
33612
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Huang, Qingling; Chen, Lihong; Yang, Leixiang et al. (2018) MDMX acidic domain inhibits p53 DNA binding in vivo and regulates tumorigenesis. Proc Natl Acad Sci U S A 115:E3368-E3377
Borcherds, Wade; Becker, Andreas; Chen, Lihong et al. (2017) Optimal Affinity Enhancement by a Conserved Flexible Linker Controls p53 Mimicry in MdmX. Biophys J 112:2038-2042
Chen, Jiandong (2016) Intra molecular interactions in the regulation of p53 pathway. Transl Cancer Res 5:639-649
Chen, Jiandong (2016) The Cell-Cycle Arrest and Apoptotic Functions of p53 in Tumor Initiation and Progression. Cold Spring Harb Perspect Med 6:a026104
Wei, Xi; Wu, Shaofang; Song, Tanjing et al. (2016) Secondary interaction between MDMX and p53 core domain inhibits p53 DNA binding. Proc Natl Acad Sci U S A 113:E2558-63
Sun, Lidong; Kokura, Kenji; Izumi, Victoria et al. (2015) MPP8 and SIRT1 crosstalk in E-cadherin gene silencing and epithelial-mesenchymal transition. EMBO Rep 16:689-99
Yang, Leixiang; Song, Tanjing; Chen, Lihong et al. (2015) Nucleolar repression facilitates initiation and maintenance of senescence. Cell Cycle 14:3613-23
Chen, Lihong; Borcherds, Wade; Wu, Shaofang et al. (2015) Autoinhibition of MDMX by intramolecular p53 mimicry. Proc Natl Acad Sci U S A 112:4624-9
Zheng, H; Chen, L; Pledger, W J et al. (2014) p53 promotes repair of heterochromatin DNA by regulating JMJD2b and SUV39H1 expression. Oncogene 33:734-44

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