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Inhibition of the anaphase-promoting complex by the Xnf7 ubiquitin ligase

Inhibition of the anaphase-promoting complex by the Xnf7 ubiquitin ligase Degradation of specific protein substrates by the anaphase-promoting complex/cyclosome (APC) is critical for mitotic exit. We have identified the protein Xenopus nuclear factor 7 (Xnf7) as a novel APC inhibitor able to regulate the timing of exit from mitosis. Immunodepletion of Xnf7 from Xenopus laevis egg extracts accelerated the degradation of APC substrates cyclin B1, cyclin B2, and securin upon release from cytostatic factor arrest, whereas excess Xnf7 inhibited APC activity. Interestingly, Xnf7 exhibited intrinsic ubiquitin ligase activity, and this activity was required for APC inhibition. Unlike other reported APC inhibitors, Xnf7 did not associate with Cdc20, but rather bound directly to core subunits of the APC. Furthermore, Xnf7 was required for spindle assembly checkpoint function in egg extracts. These data suggest that Xnf7 is an APC inhibitor able to link spindle status to the APC through direct association with APC core components. Footnotes Abbreviations used in this paper: APC, anaphase-promoting complex/cyclosome; CRS, cytoplasmic retention sequence; CSF, cytostatic factor; IAP, inhibitor of apoptosis; RRL, rabbit reticulocyte lysate; Xnf7, Xenopus nuclear factor 7. Submitted: 8 November 2004 Accepted: 7 March 2005 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Cell Biology Rockefeller University Press

Inhibition of the anaphase-promoting complex by the Xnf7 ubiquitin ligase

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References (65)

Publisher
Rockefeller University Press
Copyright
© 2005 Rockefeller University Press
ISSN
0021-9525
eISSN
1540-8140
DOI
10.1083/jcb.200411056
pmid
15824132
Publisher site
See Article on Publisher Site

Abstract

Degradation of specific protein substrates by the anaphase-promoting complex/cyclosome (APC) is critical for mitotic exit. We have identified the protein Xenopus nuclear factor 7 (Xnf7) as a novel APC inhibitor able to regulate the timing of exit from mitosis. Immunodepletion of Xnf7 from Xenopus laevis egg extracts accelerated the degradation of APC substrates cyclin B1, cyclin B2, and securin upon release from cytostatic factor arrest, whereas excess Xnf7 inhibited APC activity. Interestingly, Xnf7 exhibited intrinsic ubiquitin ligase activity, and this activity was required for APC inhibition. Unlike other reported APC inhibitors, Xnf7 did not associate with Cdc20, but rather bound directly to core subunits of the APC. Furthermore, Xnf7 was required for spindle assembly checkpoint function in egg extracts. These data suggest that Xnf7 is an APC inhibitor able to link spindle status to the APC through direct association with APC core components. Footnotes Abbreviations used in this paper: APC, anaphase-promoting complex/cyclosome; CRS, cytoplasmic retention sequence; CSF, cytostatic factor; IAP, inhibitor of apoptosis; RRL, rabbit reticulocyte lysate; Xnf7, Xenopus nuclear factor 7. Submitted: 8 November 2004 Accepted: 7 March 2005

Journal

The Journal of Cell BiologyRockefeller University Press

Published: Apr 11, 2005

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