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Myeloid leukemia factor 1 regulates p53 by suppressing COP1 via COP9 signalosome subunit 3

Noriko Yoneda-Kato1, Kiichiro Tomoda, Mari Umehara

  • 1Department of Animal Molecular Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama, Ikoma, Nara, Japan. noriko-k@bs.naist.jp

The EMBO Journal
|April 30, 2005
PubMed

Insights

Myeloid leukemia factor 1 (MLF1) negatively regulates cell growth by inducing p53-dependent cell cycle arrest. This process involves the COP9 signalosome subunit 3 (CSN3) and impacts p53 ubiquitination via COP1, suggesting a role in leukemogenesis.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Myeloid leukemia factor 1 (MLF1) is linked to cancer, but its role in cell growth regulation is unclear.
  • MLF1 overexpression correlates with malignant transformation in human cancers.
  • MLF1 is normally expressed in hematopoietic stem cells and other tissues.

Purpose of the Study:

  • To elucidate the mechanism by which MLF1 regulates cell growth.
  • To investigate the interaction of MLF1 with cell cycle regulators.
  • To identify novel binding partners and pathways involved in MLF1 function.

Main Methods:

  • Cell cycle analysis in murine embryonic fibroblasts.
  • Small interfering RNA (siRNA) knockdown of CSN3.
  • Western blotting to assess protein levels (p53, CSN3, COP1).
  • Analysis of p53 activation and ubiquitination.

Main Results:

  • MLF1 acts as a negative regulator of cell cycle progression, functioning upstream of p53.
  • MLF1 induces p53-dependent G1 cell cycle arrest.
  • CSN3 is a novel binding partner required for MLF1's function.
  • CSN3 knockdown abrogates MLF1-induced arrest and impairs p53 activation.
  • MLF1 and CSN3 levels inversely correlate with COP1, a p53 ubiquitin ligase.
  • COP1 overexpression rescues MLF1-induced growth arrest.

Conclusions:

  • MLF1 is a critical regulator of p53.
  • MLF1 influences p53 stability and activation through a novel CSN3-COP1 pathway.
  • This pathway suggests a role for MLF1 in leukemogenesis.

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