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Essential role of the B23/NPM core domain in regulating ARF binding and B23 stability

Takeharu Enomoto1, Mikael S Lindström, Aiwen Jin

  • 1Department of Radiation Oncology, University of North Carolina at Chapel Hill, NC 27599-7512, USA.

The Journal of Biological Chemistry
|May 9, 2006
PubMed

Insights

The tumor suppressor p14(ARF) interacts with nucleolar protein B23 to inhibit cell growth. A conserved B23 core motif is crucial for this interaction, stability, and nucleolar localization, impacting cancer origins.

Area of Science:

  • Cellular biology
  • Cancer research
  • Molecular genetics

Background:

  • Understanding cell cycle regulation during genotoxic stress is key to cancer origins.
  • Mechanisms linking DNA synthesis and ribosomal biogenesis are not fully understood.
  • The tumor suppressor p14(ARF) interacts with nucleolar protein B23/NPM, inhibiting rRNA biogenesis.

Purpose of the Study:

  • To elucidate the molecular basis of the p14(ARF)-B23 interaction.
  • To identify the specific B23 domain responsible for ARF binding.
  • To investigate the functional consequences of disrupting this interaction.

Main Methods:

  • Site-directed mutagenesis of conserved B23 core residues (L102A, G105A, G107A).
  • In vivo ARF binding assays.
  • Conformational modeling of the B23 core.
  • Analysis of mutant B23 stability, oligomerization, localization, ubiquitination, and degradation.

Main Results:

  • A conserved motif in the B23 oligomerization domain is essential for ARF binding.
  • Mutations in B23 core residues (L102A, G105A, G107A) abolish ARF interaction.
  • Mutant B23 proteins exhibit instability, impaired oligomerization, and nucleolar delocalization.
  • B23 core mutants show increased ubiquitination and proteasomal degradation.

Conclusions:

  • The functional integrity of the B23 core motif is essential for its stability and nucleolar localization.
  • This core motif is critical for mediating the interaction with p14(ARF).
  • Disruption of the ARF-B23 interaction impacts cellular processes relevant to cancer development.

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