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Regulation of the MDM2-p53 pathway by the nucleolar protein CSIG in response to nucleolar stress

Nan Xie1, Liwei Ma1, Feng Zhu1

  • 1Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, 38 Xueyuan Road, Beijing 100191, PR China.

Scientific Reports
|November 5, 2016
PubMed

Insights

The nucleolar protein CSIG regulates the MDM2-p53 pathway by inhibiting MDM2 activity, crucial for cellular stress response. This discovery clarifies a key mechanism in nucleolar stress signaling.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Nucleolar proteins are key regulators of the MDM2-p53 pathway, essential for cellular stress responses.
  • The precise mechanisms governing this regulation, particularly in response to nucleolar stress, are not fully understood.

Purpose of the Study:

  • To identify and characterize novel nucleolar proteins involved in the MDM2-p53 pathway.
  • To elucidate the role of the nucleolar protein CSIG in regulating cellular responses to nucleolar stress.

Main Methods:

  • Investigated nucleolar protein CSIG's localization and function.
  • Utilized knockdown experiments to assess CSIG's impact on p53 induction and cell cycle arrest.
  • Performed co-immunoprecipitation and in vitro assays to determine CSIG's interaction with MDM2 and its effect on E3 ligase activity.

Main Results:

  • CSIG translocates from the nucleolus to the nucleoplasm upon nucleolar stress.
  • CSIG knockdown impairs p53 induction and G1 phase arrest following nucleolar stress.
  • CSIG directly binds to the MDM2 RING finger domain, inhibiting MDM2's E3 ubiquitin ligase activity.
  • This inhibition reduces MDM2-mediated ubiquitination and degradation of p53.

Conclusions:

  • CSIG is a novel and critical regulator of the MDM2-p53 pathway.
  • The CSIG-MDM2-p53 regulatory axis is vital for orchestrating cellular responses to nucleolar stress.
  • Findings provide new insights into the molecular mechanisms of stress response pathways.

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