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Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
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Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

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Molecular dissection of the APC/C inhibitor Rca1 shows a novel F-box-dependent function

Norman Zielke1, Silvia Querings, Ruth Grosskortenhaus

  • 1Institute for Genetics, University of Cologne, Zülpicherstrasse 47, 50674 Köln, Germany.

EMBO Reports
|November 14, 2006
PubMed

Insights

Regulator of Cyclin A (Rca1) inhibits the anaphase-promoting complex/cyclosome (APC/C) in G2. Rca1 also promotes S-phase entry via its F-box domain, suggesting a novel SCF complex role.

Area of Science:

  • Cell cycle regulation
  • Protein complex function
  • Molecular biology

Background:

  • Regulator of Cyclin A (Rca1)/early mitotic inhibitor (Emi) proteins are crucial APC/C inhibitors.
  • In Drosophila, Rca1 prevents premature cyclin degradation by APC/C-Fzr during G2.
  • Rca1/Emi proteins possess an F-box domain, implying SCF complex interaction, though its function was unknown.

Purpose of the Study:

  • To investigate the structure-function relationship of Rca1.
  • To elucidate the role of the Rca1 F-box domain in APC/C regulation and cell cycle progression.

Main Methods:

  • Structure and function analysis of Rca1.
  • Investigating APC/C inhibition by Rca1 fragments.
  • Assessing the impact of F-box presence/absence on cell cycle transitions.
  • Overexpression and gene replacement studies in Drosophila.

Main Results:

  • A carboxy-terminal fragment of Rca1 is sufficient for APC/C inhibition.
  • The F-box domain is dispensable for G2 APC/C-Fzr inhibition.
  • Rca1 exhibits an F-box-dependent function at the G1-S transition.
  • Rca1 overexpression accelerates G1-S transition; F-box deletion delays S-phase entry.

Conclusions:

  • Rca1 has dual roles: APC/C inhibition (G2) and promoting S-phase entry (G1-S).
  • The F-box domain is critical for Rca1's role in promoting S-phase entry.
  • Rca1 likely functions as an F-box protein in an unknown SCF complex to facilitate S-phase entry.

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