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Mitotic exit: closing the gap

L Pintard1, M Peter

  • 1Swiss Institute for Experimental Cancer Research, Switzerland.

Molecular Cell
|March 12, 2002
PubMed

Insights

Tem1p activation initiates mitosis completion by inhibiting the Bub2p/Bfa1p GTPase-activating protein complex. Spindle checkpoints prevent mitotic exit by blocking Bfa1p phosphorylation, maintaining GAP activity.

Area of Science:

  • Cell biology
  • Molecular biology
  • Biochemistry

Background:

  • Mitosis completion is regulated by signaling pathways.
  • The Ras-like GTP-binding protein Tem1p is crucial for mitotic exit.
  • Tem1p's activity is modulated by GTPase-activating proteins (GAPs).

Purpose of the Study:

  • To investigate the mechanism of Tem1p activation.
  • To elucidate the role of the Bub2p/Bfa1p complex in regulating Tem1p.
  • To understand how spindle checkpoints influence mitotic exit.

Main Methods:

  • The study utilized biochemical assays and genetic analysis.
  • Investigated the interaction between Cdc5p, Bfa1p, and Bub2p.
  • Analyzed the effect of spindle checkpoint activation on Bfa1p phosphorylation.

Main Results:

  • Tem1p activation is achieved by inhibiting the Bub2p/Bfa1p GAP.
  • Phosphorylation of Bfa1p by the Polo kinase Cdc5p inhibits GAP activity.
  • Spindle checkpoint activation suppresses Bfa1p phosphorylation, maintaining GAP activity.

Conclusions:

  • Cdc5p-mediated phosphorylation of Bfa1p is a key step in Tem1p activation and mitotic exit.
  • Spindle checkpoint signaling prevents premature mitotic exit by inhibiting Bfa1p phosphorylation.
  • The Bub2p/Bfa1p complex acts as a critical regulator linking spindle checkpoint status to mitotic progression.

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