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Raf kinase inhibitory protein regulates aurora B kinase and the spindle checkpoint

Eva M Eves1, Paul Shapiro, Karuna Naik

  • 1Ben May Institute for Cancer Research, University of Chicago, Chicago, Illinois 60637, USA.

Molecular Cell
|August 19, 2006
PubMed

Insights

Raf kinase inhibitory protein (RKIP) regulates cell division by interacting with kinetochores and the spindle checkpoint. RKIP depletion disrupts mitosis, impacting cell cycle fidelity through the MAPK pathway.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Raf kinase inhibitory protein (RKIP) is a known inhibitor of the Raf/MEK/MAP kinase cascade.
  • RKIP also functions as a suppressor of cancer metastasis.
  • The role of RKIP in cell cycle regulation, specifically mitosis, is not fully understood.

Purpose of the Study:

  • To investigate the role of RKIP in the regulation of the spindle checkpoint in mammalian cells.
  • To determine the association of RKIP with centrosomes and kinetochores.
  • To elucidate the mechanism by which RKIP influences the Raf-1/MEK/ERK cascade and cell cycle fidelity.

Main Methods:

  • RKIP depletion studies using siRNA or other methods.
  • Analysis of mitotic indices, cell cycle progression (e.g., nuclear envelope breakdown to anaphase), and response to spindle poisons.
  • Investigating the effects of Raf-1 depletion, MEK inhibition, or Raf hyperactivation.
  • Assessing kinetochore localization and kinase activity of Aurora B.

Main Results:

  • RKIP associates with centrosomes and kinetochores, regulating the spindle checkpoint.
  • RKIP depletion leads to decreased mitotic index, fewer metaphase cells, and faster cell cycle progression.
  • RKIP depletion results in override of mitotic checkpoints and reduced Aurora B kinase activity and kinetochore localization.
  • Raf-1 depletion or MEK inhibition reverses RKIP depletion effects, while Raf hyperactivation mimics them.

Conclusions:

  • RKIP plays a critical role in regulating the spindle checkpoint and Aurora B kinase activity.
  • The Raf-1/MEK/ERK cascade is involved in RKIP-mediated regulation of the spindle checkpoint.
  • Modulations in the MAP kinase pathway, influenced by RKIP, significantly impact cell cycle fidelity.

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