The spindle checkpoint, APC/C(Cdc20), and APC/C(Cdh1) play distinct roles in connecting mitosis to S phase

J Cell Biol. 2013 Jun 24;201(7):1013-26. doi: 10.1083/jcb.201211019. Epub 2013 Jun 17.


DNA replication depends on a preceding licensing event by Cdt1 and Cdc6. In animal cells, relicensing after S phase but before mitosis is prevented by the Cdt1 inhibitor geminin and mitotic cyclin activity. Here, we show that geminin, like cyclin B1 and securin, is a bona fide target of the spindle checkpoint and APC/C(Cdc20). Cyclin B1 and geminin are degraded simultaneously during metaphase, which directs Cdt1 accumulation on segregating sister chromatids. Subsequent activation of APC/C(Cdh1) leads to degradation of Cdc6 well before Cdt1 becomes unstable in a replication-coupled manner. In mitosis, the spindle checkpoint supports Cdt1 accumulation, which promotes S phase onset. We conclude that the spindle checkpoint, APC/C(Cdc20), and APC/C(Cdh1) act successively to ensure that the disappearance of licensing inhibitors coincides exactly with a peak of Cdt1 and Cdc6. Whereas cell cycle entry from quiescence requires Cdc6 resynthesis, our results indicate that proliferating cells use a window of time in mitosis, before Cdc6 is degraded, as an earlier opportunity to direct S phase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase-Promoting Complex-Cyclosome
  • Antigens, CD
  • Cadherins / metabolism
  • Cadherins / physiology*
  • Cdc20 Proteins
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology*
  • Cell Line, Tumor
  • Cyclin B1 / metabolism
  • Geminin
  • Humans
  • M Phase Cell Cycle Checkpoints*
  • Mitosis / physiology*
  • Nuclear Proteins / metabolism
  • S Phase / physiology*
  • Ubiquitin-Protein Ligase Complexes / physiology*


  • Antigens, CD
  • CDC6 protein, human
  • CDH1 protein, human
  • CDT1 protein, human
  • Cadherins
  • Cdc20 Proteins
  • Cell Cycle Proteins
  • Cyclin B1
  • GMNN protein, human
  • Geminin
  • Nuclear Proteins
  • CDC20 protein, human
  • Ubiquitin-Protein Ligase Complexes
  • Anaphase-Promoting Complex-Cyclosome