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Purification of Ubiquitinated p53 Proteins from Mammalian Cells
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p53 suppresses 14-3-3γ by stimulating proteasome-mediated 14-3-3γ protein degradation

De-Yu Chen1, Dong-Fang Dai1, Ye Hua1

  • 1Institute of Oncology, The Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu 212001, P.R. China.

International Journal of Oncology
|November 12, 2014
PubMed

Insights

The tumor suppressor p53 protein degrades the oncogenic 14-3-3 gamma protein through a post-transcriptional mechanism. Loss of p53 function in lung cancer may lead to increased 14-3-3 gamma levels.

Area of Science:

  • Molecular Biology
  • Oncology
  • Cellular Biology

Background:

  • 14-3-3 proteins are highly conserved and involved in numerous cellular processes.
  • Overexpression of 14-3-3 proteins is observed in various cancers, suggesting oncogenic roles.
  • Previous work indicated p53 negatively regulates 14-3-3 gamma transcription.

Purpose of the Study:

  • Investigate p53 and 14-3-3 gamma protein levels in lung cancer.
  • Determine the mechanism by which p53 affects 14-3-3 gamma expression.
  • Explore the role of p53-mediated regulation of 14-3-3 gamma in lung cancer.

Main Methods:

  • Analysis of p53 and 14-3-3 gamma protein levels in human lung tissues.
  • Ectopic expression of wild-type and mutant p53 in cancer cell lines.
  • Co-immunoprecipitation to study protein interactions.
  • Ubiquitination assays and proteasome inhibition studies (MG132).

Main Results:

  • 14-3-3 gamma expression correlates with p53 overexpression in lung cancer tissues.
  • Wild-type p53, but not mutant p53 (R175H), suppresses 14-3-3 gamma levels in cancer cells.
  • p53 interacts with the C-terminal domain of 14-3-3 gamma, inducing its ubiquitination.
  • Proteasome inhibitor MG132 blocks p53's effect, indicating proteasome-mediated degradation.

Conclusions:

  • p53 suppresses 14-3-3 gamma protein levels via a post-transcriptional mechanism involving proteasome-mediated degradation.
  • This regulation pathway is active in lung cancer.
  • Loss of p53 function in lung cancer could lead to 14-3-3 gamma upregulation and potential oncogenesis.

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