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Positive feedback sharpens the anaphase switch


At the onset of anaphase, sister-chromatid cohesion is dissolved abruptly and irreversibly, ensuring that all chromosome pairs disjoin almost simultaneously. The regulatory mechanisms that generate this switch-like behaviour are unclear. Anaphase is initiated when a ubiquitin ligase, the anaphase-promoting complex (APC), triggers the destruction of securin, thereby allowing separase, a protease, to disrupt sister-chromatid cohesion1,2,3,4. Here we demonstrate that the cyclin-dependent kinase 1 (Cdk1)-dependent phosphorylation of securin near its destruction-box motif inhibits securin ubiquitination by the APC. The phosphatase Cdc14 reverses securin phosphorylation, thereby increasing the rate of securin ubiquitination. Because separase is known to activate Cdc14 (refs 5 and 6), our results support the existence of a positive feedback loop that increases the abruptness of anaphase. Consistent with this model, we show that mutations that disrupt securin phosphoregulation decrease the synchrony of chromosome segregation. Our results also suggest that coupling securin degradation with changes in Cdk1 and Cdc14 activities helps coordinate the initiation of sister-chromatid separation with changes in spindle dynamics.

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Figure 1: Cdk1 and Cdc14 control the phosphorylation state of securin near its destruction-box and modulate the rate of securin ubiquitination.
Figure 2: Modulation of securin ubiquitination by Cdk1 and Cdc14 gives rise to a potential positive feedback loop in the anaphase regulatory network.
Figure 3: Modulation of securin ubiquitination by Cdk1 is required for an abrupt anaphase.
Figure 4: Modulation of securin ubiquitination by Cdk1 helps coordinate anaphase onset with changes in spindle dynamics.


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We thank: P. H. O’Farrell, A. D. Johnson and M. J. Sullivan for discussions; J. A. Ubersax, G. Goshima and O. Cohen-Fix for reagents; S. Foster, M. C. Rodrigo-Brenni, M. Enquist-Newman and the Morgan laboratory for help generating strains and reagents; J. M. Pedraza and A. van Oudenaarden for help with the model; K. S. Thorn and the University of California, San Francisco, Nikon Imaging Center for help with microscopy; and M. J. Sullivan and J. L. Feldman for reading the manuscript. This work was supported by funding from the National Institute of General Medical Sciences (D.O.M.), a grant from the Sandler Family Foundation (A.N.K.) and a fellowship from the National Science Foundation (L.J.H.).

Author Contributions L.J.H. designed, performed and analysed the experiments; A.N.K performed mass spectrometric analysis; D.O.M. provided guidance.

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Correspondence to David O. Morgan.

Supplementary information

Supplementary Information

The file contains Supplementary Figures 1-9 with Legends and legends to Supplementary Movies 1-3 (PDF 1798 kb)

Supplementary Movie 1

The file contains Supplementary Movie 1 showing wild-type cell. (MOV 1197 kb)

Supplementary Movie 2

The file contains Supplementary Movie 2 showing securin-2A cell. (MOV 1058 kb)

Supplementary Movie 3

The file contains Supplementary Movie 3 showing securinΔ cell. (MOV 476 kb)

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Holt, L., Krutchinsky, A. & Morgan, D. Positive feedback sharpens the anaphase switch. Nature 454, 353–357 (2008).

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