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BubR1 is essential for kinetochore localization of other spindle checkpoint proteins and its phosphorylation requires Mad1

BubR1 is essential for kinetochore localization of other spindle checkpoint proteins and its... The spindle checkpoint delays anaphase onset until all chromosomes have attached properly to the mitotic spindle. Checkpoint signal is generated at kinetochores that are not bound with spindle microtubules or not under tension. Unattached kinetochores associate with several checkpoint proteins, including BubR1, Bub1, Bub3, Mad1, Mad2, and CENP-E. I herein show that BubR1 is important for the spindle checkpoint in Xenopus egg extracts. The protein accumulates and becomes hyperphosphorylated at unattached kinetochores. Immunodepletion of BubR1 greatly reduces kinetochore binding of Bub1, Bub3, Mad1, Mad2, and CENP-E. Loss of BubR1 also impairs the interaction between Mad2, Bub3, and Cdc20, an anaphase activator. These defects are rescued by wild-type, kinase-dead, or a truncated BubR1 that lacks its kinase domain, indicating that the kinase activity of BubR1 is not essential for the spindle checkpoint in egg extracts. Furthermore, localization and hyperphosphorylation of BubR1 at kinetochores are dependent on Bub1 and Mad1, but not Mad2. This paper demonstrates that BubR1 plays an important role in kinetochore association of other spindle checkpoint proteins and that Mad1 facilitates BubR1 hyperphosphorylation at kinetochores. spindle checkpoint; Xenopus ; BubR1; Mad1; Bub1 Footnotes ↵ * Abbreviations used in this paper: APC, anaphase promoting complex; CSF, cytostatic factor; LPP, lambda protein phosphatase. Submitted: 9 April 2002 Accepted: 10 June 2002 Revision received 7 June 2002 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Cell Biology Rockefeller University Press

BubR1 is essential for kinetochore localization of other spindle checkpoint proteins and its phosphorylation requires Mad1

Chen, Rey-Huei
The Journal of Cell Biology , Volume 158 (3): 487 – Aug 5, 2002
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Publisher
Rockefeller University Press
Copyright
© 2002 Rockefeller University Press
ISSN
0021-9525
eISSN
1540-8140
DOI
10.1083/jcb.200204048
pmid
12163471
Publisher site
See Article on Publisher Site

Abstract

The spindle checkpoint delays anaphase onset until all chromosomes have attached properly to the mitotic spindle. Checkpoint signal is generated at kinetochores that are not bound with spindle microtubules or not under tension. Unattached kinetochores associate with several checkpoint proteins, including BubR1, Bub1, Bub3, Mad1, Mad2, and CENP-E. I herein show that BubR1 is important for the spindle checkpoint in Xenopus egg extracts. The protein accumulates and becomes hyperphosphorylated at unattached kinetochores. Immunodepletion of BubR1 greatly reduces kinetochore binding of Bub1, Bub3, Mad1, Mad2, and CENP-E. Loss of BubR1 also impairs the interaction between Mad2, Bub3, and Cdc20, an anaphase activator. These defects are rescued by wild-type, kinase-dead, or a truncated BubR1 that lacks its kinase domain, indicating that the kinase activity of BubR1 is not essential for the spindle checkpoint in egg extracts. Furthermore, localization and hyperphosphorylation of BubR1 at kinetochores are dependent on Bub1 and Mad1, but not Mad2. This paper demonstrates that BubR1 plays an important role in kinetochore association of other spindle checkpoint proteins and that Mad1 facilitates BubR1 hyperphosphorylation at kinetochores. spindle checkpoint; Xenopus ; BubR1; Mad1; Bub1 Footnotes ↵ * Abbreviations used in this paper: APC, anaphase promoting complex; CSF, cytostatic factor; LPP, lambda protein phosphatase. Submitted: 9 April 2002 Accepted: 10 June 2002 Revision received 7 June 2002

Journal

The Journal of Cell Biology – Rockefeller University Press

Published: Aug 5, 2002

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