A mouse p53 mutant lacking the proline-rich domain rescues Mdm4 deficiency and provides insight into the Mdm2-Mdm4-p53 regulatory network

Cancer Cell. 2006 Apr;9(4):273-85. doi: 10.1016/j.ccr.2006.03.014.


The mechanisms by which Mdm2 and Mdm4 (MdmX) regulate p53 remain controversial. We generated a mouse encoding p53 lacking the proline-rich domain (p53DeltaP). p53DeltaP exhibited increased sensitivity to Mdm2-dependent degradation and decreased transactivation capacity, correlating with deficient cell cycle arrest and reduced apoptotic responses. p53DeltaP induced lethality in Mdm2-/- embryos, but not in Mdm4-/- embryos. Mdm4 loss did not alter Mdm2 stability but significantly increased p53DeltaP transactivation to partially restore cycle control. In contrast, decreasing Mdm2 levels increased p53DeltaP levels without altering p53DeltaP transactivation. Thus, Mdm4 regulates p53 activity, while Mdm2 mainly controls p53 stability. Furthermore, Mdm4 loss dramatically improved p53DeltaP-mediated suppression of oncogene-induced tumors, emphasizing the importance of targeting Mdm4 in chemotherapies designed to activate p53.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Cells, Cultured
  • DNA / genetics
  • DNA Damage
  • Gene Expression Regulation, Neoplastic
  • Mice
  • Mice, Transgenic
  • Mutation / genetics*
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Neoplasms / pathology
  • Proline / genetics
  • Proline / metabolism*
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins / deficiency*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-mdm2 / deficiency
  • Proto-Oncogene Proteins c-mdm2 / genetics
  • Proto-Oncogene Proteins c-mdm2 / metabolism*
  • Transcriptional Activation / genetics
  • Tumor Suppressor Protein p53 / chemistry
  • Tumor Suppressor Protein p53 / genetics*
  • Tumor Suppressor Protein p53 / metabolism*
  • Ubiquitin-Protein Ligases / deficiency*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • Mdm4 protein, mouse
  • Proto-Oncogene Proteins
  • Tumor Suppressor Protein p53
  • DNA
  • Proline
  • Proto-Oncogene Proteins c-mdm2
  • Ubiquitin-Protein Ligases