Lookup NU author(s): Deyu Li,
Dr Gary Morley,
Emeritus Professor Michael Whitaker,
Dr Jun-yong Huang
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To prevent aneuploidy, cells require a mitotic surveillance mechanism, the spindle assembly checkpoint (SAC). The SAC prevents metaphase/anaphase transition by blocking the ubiquitylation and destruction of cyclin B and securin via Cdc20-activated anaphase promoting complex or cyclosome (APC/C) mediated proteolysis pathway. This checkpoint involves kinetochore proteins Mad2, BubR1 and Cdc20. Mad2 and BubR1 are inhibitors of the APC/C, but Cdc20 is an activator. Exactly how the SAC regulates Cdc20 via unattached kinetochores remains unclear, in vertebrates most current models suggest that kinetochore bound Mad2 is required for initial binding to Cdc20 to form a stable complex that includes BubR1. Here we show that the Mad2 kinetochore dimerisation recruitment mechanism is conserved, and that the recruitment of Cdc20 to kinetochores in Drosophila requires BubR1 but not Mad2. BubR1 and Mad2 can bind to Cdc20 independently and the interactions are enhanced after cells are arrested at mitosis by the depletion of Cdc27 using both RNAi in S2 cells or by MG132 treatment in syncytial embryos. These findings offer an explanation of why BubR1 is more important than Mad2 in flies for SAC function. These findings could lead to a better understanding of vertebrate SAC mechanisms.
Author(s): Li D, Morley G, Whitaker M, Huang JY
Publication type: Article
Journal: Molecular and Cellular Biology
Print publication date: 26/04/2010
ISSN (print): 0270-7306
ISSN (electronic): 1098-5549
Publisher: American Society for Microbiology
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