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Dev Cell. 2009 Jan;16(1):118-31. doi: 10.1016/j.devcel.2008.11.004.

BubR1 N terminus acts as a soluble inhibitor of cyclin B degradation by APC/C(Cdc20) in interphase.

Author information

1
Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.

Abstract

BubR1 is an essential mitotic checkpoint protein with multiple functional domains. It has been implicated in mitotic checkpoint control, as an active kinase at unattached kinetochores, and as a cytosolic inhibitor of APC/C(Cdc20) activity, as well as in mitotic timing and stable chromosome-spindle attachment. Using BubR1-conditional knockout cells and BubR1 domain mutants, we demonstrate that the N-terminal Cdc20 binding domain of BubR1 is essential for all of these functions, whereas its C-terminal Cdc20-binding domain, Bub3-binding domain, and kinase domain are not. We find that the BubR1 N terminus binds to Cdc20 in a KEN box-dependent manner to inhibit APC/C activity in interphase, thereby allowing accumulation of cyclin B in G(2) phase prior to mitosis onset. Together, our results suggest that kinetochore-bound BubR1 is nonessential and that soluble BubR1 functions as a pseudosubstrate inhibitor of APC/C(Cdc20) during interphase to prevent unscheduled degradation of specific APC/C substrates.

PMID:
19154723
PMCID:
PMC2659634
DOI:
10.1016/j.devcel.2008.11.004
[Indexed for MEDLINE]
Free PMC Article

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