The anaphase-promoting complex/cyclosome (APC/C) is required for rereplication control in endoreplication cycles.
Endoreplicating cells undergo multiple rounds of DNA replication leading to polyploidy or polyteny. Oscillation of Cyclin E (CycE)-dependent kinase activity is the main driving force in Drosophila endocycles. High levels of CycE-Cdk2 activity trigger S phase, while down-regulation of CycE-Cdk2 activity is crucial to allow licensing of replication origins. In mitotic cells relicensing in S phase is prevented by Geminin. Here we show that Geminin protein oscillates in endoreplicating salivary glands of Drosophila. Geminin levels are high in S phase, but drop once DNA replication has been completed. DNA licensing is coupled to mitosis through the action of the anaphase-promoting complex/cyclosome (APC/C). We demonstrate that, even though endoreplicating cells never enter mitosis, APC/C activity is required in endoreplicating cells to mediate Geminin oscillation. Down-regulation of APC/C activity results in stabilization of Geminin protein and blocks endocycle progression. Geminin is only abundant in cells with high CycE-Cdk2 activity, suggesting that APC/C-Fzr activity is periodically inhibited by CycE-Cdk2, to prevent relicensing in S-phase cells.
University of Cologne, Institute for Genetics, 50674 Köln, Germany.
Norman
N
Zielke
Silvia
S
Querings
Carmen
C
Rottig
Christian
C
Lehner
Frank
F
Sprenger
D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D030801:Animals, Genetically Modified; D064200:Cdh1 Proteins; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D019927:Cyclin E / Q000502:physiology; D051357:Cyclin-Dependent Kinase 2 / Q000502:physiology; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D042522:DNA Replication Timing / Q000235:genetics / Q000502:physiology*; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D064248:Geminin; D005786:Gene Expression Regulation; D008938:Mitosis / Q000235:genetics; D008954:Models, Biological; D018741:Replication Origin / Q000502:physiology; D012469:Salivary Glands / Q000378:metabolism; D014162:Transfection; D043743:Ubiquitin-Protein Ligase Complexes / Q000502:physiology*
D064200:Cdh1 Proteins; D018797:Cell Cycle Proteins; D019927:Cyclin E; D029721:Drosophila Proteins; D064248:Geminin; C491136:Rca1 protein, Drosophila; C577674:fzr protein, Drosophila; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D051357:Cyclin-Dependent Kinase 2; C495887:cdk2 protein, Drosophila