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Updated: May 24, 2026

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
10:54

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations

Published on: September 17, 2012

An APC/C inhibitor stabilizes cyclin B1 by prematurely terminating ubiquitination

Xing Zeng1, Randall W King

  • 1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA.

Nature Chemical Biology
|February 28, 2012
PubMed

Insights

Tosyl arginine methyl ester (TAME) inhibits the anaphase-promoting complex/cyclosome (APC) by ejecting its activator, Cdc20. TAME stabilizes cyclin B1 by slowing its ubiquitination and preventing further Cdc20 binding, ultimately halting proteolysis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The anaphase-promoting complex/cyclosome (APC) is a crucial ubiquitin ligase regulating mitosis.
  • Tosyl arginine methyl ester (TAME) previously identified as an APC inhibitor, competes with Cdc20 for APC binding.

Purpose of the Study:

  • To elucidate the precise mechanism by which TAME inhibits APC function.
  • To investigate the role of Cdc20 autoubiquitination and cyclin B1 in TAME-mediated inhibition.

Main Methods:

  • Biochemical assays in Xenopus extracts.
  • Analysis of protein-protein interactions and enzyme kinetics.
  • Monitoring ubiquitination of APC substrates like cyclin B1.

Main Results:

  • TAME promotes Cdc20 autoubiquitination, leading to its ejection from the APC in the absence of substrates.
  • Cyclin B1 counteracts TAME by enhancing Cdc20 binding and suppressing autoubiquitination.
  • TAME stabilizes cyclin B1 by reducing the APC-Cdc20 complex's catalytic rate and diminishing cyclin B1's ability to promote Cdc20 binding as it becomes ubiquitinated.

Conclusions:

  • TAME inhibits APC-dependent proteolysis through a dual mechanism involving Cdc20 ejection and modulation of cyclin B1 ubiquitination.
  • These findings reveal complex regulatory interplay between TAME, Cdc20, and cyclin B1 in controlling mitotic exit.

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