Wild type p53 stabilization and activation in response to stress is critical for its tumor suppressor function. Paradoxically, mutant p53 is also highly stabilized in tumors and promotes metastasis and therapy resistance through gain-of-function. Elucidating the mechanisms that regulate p53 stability and activation may provide novel therapeutic strategies that target wild type or mutant p53. MDM2 and MDMX are major regulators of p53 ubiquitination, DNA binding, and transcriptional activity. Our recent study suggested that ATM-dependent phosphorylation of MDM2 and MDMX near the RING domains are important for stabilization and activation of p53. We found that these phosphorylation events inhibit the homo-dimerization of MDM2 RING domain, inhibit the intra- molecular interaction between the MDM2 RING and acidic domains, and inhibit the intra-molecular interaction between MDMX acidic and p53 binding domains. We also identified the MDM2 acidic domain as an important activator of the RING domain E3 ligase activity. These findings led to the hypothesis that various signaling pathways target the intra-molecular interactions in MDM2 and MDMX to stabilize and activate p53. The following experiments are proposed to further study the mechanisms of p53 activation during stress response. (1) Determine the function and mechanism of the MDM2 acidic domain. (2) Investigate the regulation of MDM2 domain interactions by stress signals. (3) Test a novel strategy of targeting intra-molecular interactions (4) Characterize the structure and dynamics of the MDM2 and MDMX domain interactions. The proposed experiments will lead to a new level of understanding of p53 regulation, explore novel intra- molecular regulatory mechanisms of MDM2 and MDMX, and develop new strategies for investigating and targeting MDM2 and MDMX.

Public Health Relevance

This proposal investigates the molecular mechanisms by which cells control the level and activity of the p53 tumor suppressor. Wild type p53 stabilization and activation in response to stress is critical for its tumor suppressor function. Paradoxically, mutant p53 is also highly stabilized in tumors and promotes metastasis and therapy resistance through gain-of-function. Elucidating the mechanisms that regulate p53 stability and activation may provide novel therapeutic strategies that target wild type or mutant p53. MDM2 and MDMX are major regulators of p53 ubiquitination, DNA binding, and transcriptional activity. This proposal will investigate the mechanism of p53 activation

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA141244-10
Application #
9650541
Study Section
Tumor Cell Biology Study Section (TCB)
Program Officer
Watson, Joanna M
Project Start
2009-07-01
Project End
2021-02-28
Budget Start
2019-03-01
Budget End
2021-02-28
Support Year
10
Fiscal Year
2019
Total Cost
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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