Function and Regulation of MDMX

Summary

Principal Investigator: Jiandong Chen
Abstract: DESCRIPTION (provided by applicant): MDM2 and its homolog MDMX are important regulators of the p53 tumor suppressor. Knockout experiments showed that both are essential for viability of mouse embryos. In human tumor cells, MDMX knockdown inhibits tumor xenograft formation, whereas MDMX overexpression increases tumor resistance to chemotherapy. Unlike MDM2, MDMX does not have E3 ligase activity and its mechanism of p53 regulation is poorly understood. We found that MDMX is an integral part of signaling pathways that activate p53. DNA damage induces MDMX phosphorylation by ATM and Chk2, leading to its degradation by MDM2. Oncogenic and nucleolar stress also induce MDMX degradation by ARF and L11 regulation of MDM2. Therefore, accelerated MDMX degradation is a common mechanism for p53 activation. We found that 14-3-3 proteins regulate MDMX degradation after DNA damage by binding to a Chk2 phosphorylation site (S367) on MDMX. We have also identified CK11 as an MDMX binding partner that phosphorylates MDMX S289 and enhances the ability of MDMX to inhibit p53. We hypothesize that signaling to p53 is in part mediated through regulation of MDMX phosphorylation and degradation. The following experiments are proposed to further study the function and regulation of MDMX during stress response. (1) Determine the mechanism of p53 inhibition by MDMX. (2) Investigate the regulation of MDMX-p53 interaction by Chk2 and CK1?. (3) Investigate the regulation of MDMX degradation. (4) Test the in vivo functions of MDMX interactions with 14-3-3 and CK1?. These experiments should lead to a better understanding of the mechanisms that regulate MDMX and may identify novel strategy for targeting MDMX in human cancer. PUBLIC HEALTH RELEVANCE: The proposal will study the regulation of the mdmx oncoprotein and the mechanism of p53 inactivation by mdmx. The experiments are based on recent findings on the regulation of mdmx degradation by phosphorylation and interactions with kinases and ribosomal proteins. The experiments will also use mouse models to test the physiological functions of mdmx modifications. Understanding the mechanisms of mdmx regulation may lead to new strategies to activate p53 in cancer cells.
Funding Period: 2004-07-01 - 2014-11-30
more information: NIH RePORT

Top Publications

  1. pmc Therapeutic implications of autoimmune vitiligo T cells
    Kepa Oyarbide-Valencia
    Department of Pathology Oncology Institute, Loyola University Chicago, 2160 South First Ave, Bldg 112, Rm 203, Maywood, IL 60153, USA
    Autoimmun Rev 5:486-92. 2006
  2. pmc Regulation of SirT1-nucleomethylin binding by rRNA coordinates ribosome biogenesis with nutrient availability
    Leixiang Yang
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida, USA
    Mol Cell Biol 33:3835-48. 2013
  3. pmc p53 promotes repair of heterochromatin DNA by regulating JMJD2b and SUV39H1 expression
    H Zheng
    Molecular Oncology Department, H Lee Moffitt Cancer Center, Tampa, FL, USA
    Oncogene 33:734-44. 2014
  4. pmc Casein kinase 1α regulates an MDMX intramolecular interaction to stimulate p53 binding
    Shaofang Wu
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida, USA
    Mol Cell Biol 32:4821-32. 2012
  5. pmc Conjugation of spermine enhances cellular uptake of the stapled peptide-based inhibitors of p53-Mdm2 interaction
    Avinash Muppidi
    Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA
    Bioorg Med Chem Lett 21:7412-5. 2011
  6. pmc Regulation of MDM2 E3 ligase activity by phosphorylation after DNA damage
    Qian Cheng
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida 33612, USA
    Mol Cell Biol 31:4951-63. 2011
  7. pmc Inhibition of p53 DNA binding function by the MDM2 protein acidic domain
    Brittany Cross
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida 33612, USA
    J Biol Chem 286:16018-29. 2011
  8. pmc Synthesis of cell-permeable stapled peptide dual inhibitors of the p53-Mdm2/Mdmx interactions via photoinduced cycloaddition
    Michael M Madden
    Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA
    Bioorg Med Chem Lett 21:1472-5. 2011
  9. pmc MDM2 recruitment of lysine methyltransferases regulates p53 transcriptional output
    Lihong Chen
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
    EMBO J 29:2538-52. 2010
  10. pmc p53 inactivation by MDM2 and MDMX negative feedback loops in testicular germ cell tumors
    Baozong Li
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
    Cell Cycle 9:1411-20. 2010

Research Grants

  1. A PATHWAY OF TUMOR SUPPRESSION
    Guillermina Lozano; Fiscal Year: 2013
  2. Mechanisms of Mdm2/Mdmx in repressing p53
    Wei Gu; Fiscal Year: 2013

Detail Information

Publications14

  1. pmc Therapeutic implications of autoimmune vitiligo T cells
    Kepa Oyarbide-Valencia
    Department of Pathology Oncology Institute, Loyola University Chicago, 2160 South First Ave, Bldg 112, Rm 203, Maywood, IL 60153, USA
    Autoimmun Rev 5:486-92. 2006
    ....
  2. pmc Regulation of SirT1-nucleomethylin binding by rRNA coordinates ribosome biogenesis with nutrient availability
    Leixiang Yang
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida, USA
    Mol Cell Biol 33:3835-48. 2013
    ..This RNA-mediated mechanism enables the eNoSC to amplify the effects of upstream nutrient-responsive regulators. ..
  3. pmc p53 promotes repair of heterochromatin DNA by regulating JMJD2b and SUV39H1 expression
    H Zheng
    Molecular Oncology Department, H Lee Moffitt Cancer Center, Tampa, FL, USA
    Oncogene 33:734-44. 2014
    ..The results suggest that by regulating JMJD2b and SUV39H1 expression, p53 not only controls transcription but also promotes HC relaxation to accelerate a rate-limiting step in the repair of complex genomes. ..
  4. pmc Casein kinase 1α regulates an MDMX intramolecular interaction to stimulate p53 binding
    Shaofang Wu
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida, USA
    Mol Cell Biol 32:4821-32. 2012
    ..Therefore, CK1α is an important functional partner of MDMX. DNA damage activates p53 in part by disrupting CK1α-MDMX interaction and reducing MDMX-p53 binding affinity...
  5. pmc Conjugation of spermine enhances cellular uptake of the stapled peptide-based inhibitors of p53-Mdm2 interaction
    Avinash Muppidi
    Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA
    Bioorg Med Chem Lett 21:7412-5. 2011
    ....
  6. pmc Regulation of MDM2 E3 ligase activity by phosphorylation after DNA damage
    Qian Cheng
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida 33612, USA
    Mol Cell Biol 31:4951-63. 2011
    ..These results suggest that the acidic domain and RING domain of MDM2 are both allosterically coupled to the intervening ATM sites, which enables the same modification to regulate multiple MDM2 functions critical for p53 ubiquitination...
  7. pmc Inhibition of p53 DNA binding function by the MDM2 protein acidic domain
    Brittany Cross
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida 33612, USA
    J Biol Chem 286:16018-29. 2011
    ....
  8. pmc Synthesis of cell-permeable stapled peptide dual inhibitors of the p53-Mdm2/Mdmx interactions via photoinduced cycloaddition
    Michael M Madden
    Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA
    Bioorg Med Chem Lett 21:1472-5. 2011
    ..Furthermore, the positively charged, stapled peptides showed enhanced cellular uptake along with modest in vivo activity...
  9. pmc MDM2 recruitment of lysine methyltransferases regulates p53 transcriptional output
    Lihong Chen
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
    EMBO J 29:2538-52. 2010
    ..These results suggest that MDM2-dependent recruitment of methyltransferases is a novel mechanism of p53 regulation through methylation of both p53 itself and histone H3 at target promoters...
  10. pmc p53 inactivation by MDM2 and MDMX negative feedback loops in testicular germ cell tumors
    Baozong Li
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
    Cell Cycle 9:1411-20. 2010
    ..Furthermore, TGCT cells are unique in having a strong apoptosis response to p53. Direct activation of p53 by targeting MDM2 and MDMX may provide a backup approach for the treatment of TGCTs resistant to DNA-damaging drugs...
  11. pmc Mechanism of p53 stabilization by ATM after DNA damage
    Qian Cheng
    Molecular Oncology Department, Mofftt Cancer Center, Tampa, FL, USA
    Cell Cycle 9:472-8. 2010
    ..These findings suggest a novel model of p53 activation and a general mechanism of E3 ligase regulation by phosphorylation...
  12. pmc Structure-based design of high affinity peptides inhibiting the interaction of p53 with MDM2 and MDMX
    Jason Phan
    Molecular Oncology, H Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA
    J Biol Chem 285:2174-83. 2010
    ..These include large conformational changes of the pDIQ to reach into a hydrophobic site unique to MDMX. The findings suggest new strategies toward the rational design of small molecule inhibitors efficiently targeting MDMX...
  13. pmc ATM activates p53 by regulating MDM2 oligomerization and E3 processivity
    Qian Cheng
    Department of Molecular Oncology, Moffitt Cancer Center, Tampa, FL, USA
    EMBO J 28:3857-67. 2009
    ..Promoting or disrupting E3 oligomerization may be a general mechanism by which signalling kinases regulate ubiquitination reactions, and a potential target for therapeutic intervention...
  14. pmc hMOF acetylation of DBC1/CCAR2 prevents binding and inhibition of SirT1
    Hong Zheng
    Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida, USA
    Mol Cell Biol 33:4960-70. 2013
    ..These results suggest that acetylation of DBC1 inhibits binding to SirT1 and serves as a mechanism that connects DNA damage signaling to SirT1 and cell fate determination. ..

Research Grants30

  1. A PATHWAY OF TUMOR SUPPRESSION
    Guillermina Lozano; Fiscal Year: 2013
    ..Lastly, we will identify factors that allow tumor (but not normal) cells to tolerate high Mdm2 levels using genetic screens. ..
  2. Mechanisms of Mdm2/Mdmx in repressing p53
    Wei Gu; Fiscal Year: 2013
    ..This study will elucidate the precise mechanisms for both Mdm2 and Mdmx in p53 regulation and yield crucial insights regarding how to target these two oncoproteins in cancer therapy. ..