Checkpoint inhibition of the APC/C in HeLa cells is mediated by a complex of BUBR1, BUB3, CDC20, and MAD2.
J Cell Biol
; 154(5): 925-36, 2001 Sep 03.
Article
em En
| MEDLINE
| ID: mdl-11535616
ABSTRACT
The mitotic checkpoint prevents cells with unaligned chromosomes from prematurely exiting mitosis by inhibiting the anaphase-promoting complex/cyclosome (APC/C) from targeting key proteins for ubiquitin-mediated proteolysis. We have examined the mechanism by which the checkpoint inhibits the APC/C by purifying an APC/C inhibitory factor from HeLa cells. We call this factor the mitotic checkpoint complex (MCC) as it consists of hBUBR1, hBUB3, CDC20, and MAD2 checkpoint proteins in near equal stoichiometry. MCC inhibitory activity is 3,000-fold greater than that of recombinant MAD2, which has also been shown to inhibit APC/C in vitro. Surprisingly, MCC is not generated from kinetochores, as it is also present and active in interphase cells. However, only APC/C isolated from mitotic cells was sensitive to inhibition by MCC. We found that the majority of the APC/C in mitotic lysates is associated with the MCC, and this likely contributes to the lag in ubiquitin ligase activity. Importantly, chromosomes can suppress the reactivation of APC/C. Chromosomes did not affect the inhibitory activity of MCC or the stimulatory activity of CDC20. We propose that the preformed interphase pool of MCC allows for rapid inhibition of APC/C when cells enter mitosis. Unattached kinetochores then target the APC/C for sustained inhibition by the MCC.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas Quinases
/
Proteínas de Ligação ao Cálcio
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Proteínas Fúngicas
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Proteínas
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Proteínas de Transporte
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Genes cdc
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Proteínas de Ciclo Celular
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Proteínas de Saccharomyces cerevisiae
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Complexos Ubiquitina-Proteína Ligase
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Ligases
Idioma:
En
Ano de publicação:
2001
Tipo de documento:
Article