Human securin proteolysis is controlled by the spindle checkpoint and reveals when the APC/C switches from activation by Cdc20 to Cdh1.
Progress through mitosis is controlled by the sequential destruction of key regulators including the mitotic cyclins and securin, an inhibitor of anaphase whose destruction is required for sister chromatid separation. Here we have used live cell imaging to determine the exact time when human securin is degraded in mitosis. We show that the timing of securin destruction is set by the spindle checkpoint; securin destruction begins at metaphase once the checkpoint is satisfied. Furthermore, reimposing the checkpoint rapidly inactivates securin destruction. Thus, securin and cyclin B1 destruction have very similar properties. Moreover, we find that both cyclin B1 and securin have to be degraded before sister chromatids can separate. A mutant form of securin that lacks its destruction box (D-box) is still degraded in mitosis, but now this is in anaphase. This destruction requires a KEN box in the NH2 terminus of securin and may indicate the time in mitosis when ubiquitination switches from APCCdc20 to APCCdh1. Lastly, a D-box mutant of securin that cannot be degraded in metaphase inhibits sister chromatid separation, generating a cut phenotype where one cell can inherit both copies of the genome. Thus, defects in securin destruction alter chromosome segregation and may be relevant to the development of aneuploidy in cancer.
Hagting
Anja
A
Wellcome/Cancer Research UK Institute, Cambridge CB2 1QR, United Kingdom.
Den Elzen
Nicole
N
Vodermaier
Hartmut C
HC
Waizenegger
Irene C
IC
Peters
Jan-Michael
JM
Pines
Jonathon
J
D000705:Anaphase / Q000502:physiology; D015415:Biomarkers; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D002842:Chromatids / Q000502:physiology; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008677:Metaphase / Q000502:physiology; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D064249:Securin; D017384:Sequence Deletion; D008941:Spindle Apparatus / Q000502:physiology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D014452:Ubiquitins / Q000378:metabolism
D015415:Biomarkers; C534699:CCNB1 protein, human; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; D064249:Securin; D014452:Ubiquitins; C578002:pituitary tumor-transforming protein 1, human; D018844:Cyclin-Dependent Kinases