title: The spindle checkpoint, APC/C(Cdc20), and APC/C(Cdh1) play distinct roles in connecting mitosis to S phase.
abstract: 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.
authors.affiliation: Division of Cell Biology I (B5), The Netherlands Cancer Institute (NKI-AvL), 1066 CX Amsterdam, Netherlands. l.clijsters@nki.nl
authors.forename: Linda
authors.initials: L
authors.lastname: Clijsters
authors.forename: Janneke
authors.initials: J
authors.lastname: Ogink
authors.forename: Rob
authors.initials: R
authors.lastname: Wolthuis
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D015703:Antigens, CD; D015820:Cadherins / Q000378:metabolism / Q000502:physiology*; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D056744:Cyclin B1 / Q000378:metabolism; D064248:Geminin; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints; D008938:Mitosis / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D016196:S Phase / Q000502:physiology*; D043743:Ubiquitin-Protein Ligase Complexes / Q000502:physiology*
chemical_list: D015703:Antigens, CD; C103706:CDC6 protein, human; C513384:CDH1 protein, human; C467199:CDT1 protein, human; D015820:Cadherins; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D056744:Cyclin B1; C577995:GMNN protein, human; D064248:Geminin; D009687:Nuclear Proteins; C577488:CDC20 protein, human; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome