Exit from mitosis in budding yeast: biphasic inactivation of the Cdc28-Clb2 mitotic kinase and the role of Cdc20

Mol Cell. 2000 Mar;5(3):501-11. doi: 10.1016/s1097-2765(00)80444-x.


Cdc20, an activator of the anaphase-promoting complex (APC), is also required for the exit from mitosis in Saccharomyces cerevisiae. Here we show that during mitosis, both the inactivation of Cdc28-Clb2 kinase and the degradation of mitotic cyclin Clb2 occur in two steps. The first phase of Clb2 proteolysis, which commences at the metaphase-to-anaphase transition when Clb2 abundance is high, is dependent on Cdc20. The second wave of Clb2 destruction in telophase requires activation of the Cdc20 homolog, Hct1/Cdh1. The first phase of Clb2 destruction, which lowers the Cdc28-Clb2 kinase activity, is a prerequisite for the second. Thus, Clb2 proteolysis is not solely mediated by Hct1 as generally believed; instead, it requires a sequential action of both Cdc20 and Hct1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase / physiology
  • Anaphase-Promoting Complex-Cyclosome
  • CDC28 Protein Kinase, S cerevisiae / metabolism*
  • Cdc20 Proteins
  • Cdh1 Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cyclin B / metabolism*
  • Fungal Proteins
  • GTP-Binding Proteins / genetics
  • Ligases / metabolism
  • Mitosis / physiology*
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins*
  • Telophase / physiology
  • Ubiquitin-Protein Ligase Complexes*
  • Ubiquitin-Protein Ligases


  • CDC15 protein
  • CDC20 protein, S cerevisiae
  • CDH1 protein, S cerevisiae
  • CLB2 protein, S cerevisiae
  • CLB5 protein, S cerevisiae
  • Cdc20 Proteins
  • Cdh1 Proteins
  • Cell Cycle Proteins
  • Cyclin B
  • Fungal Proteins
  • Saccharomyces cerevisiae Proteins
  • Ubiquitin-Protein Ligase Complexes
  • Anaphase-Promoting Complex-Cyclosome
  • Ubiquitin-Protein Ligases
  • CDC28 Protein Kinase, S cerevisiae
  • GTP-Binding Proteins
  • Ligases