Depletion of p31^comet protein promotes sensitivity to antimitotic drugs

Abstract

Antimitotic spindle poisons are among the most important chemotherapeutic agents available. However, precocious mitotic exit by mitotic slippage limits the cytotoxicity of spindle poisons. The MAD2-binding protein p31 comet is implicated in silencing the spindle assembly checkpoint after all kinetochores are attached to spindles. In this study, we report that the levels of p31 comet andMAD2in different cell lines are closely linked with susceptibility to mitotic slippage. Down-regulation of p31 comet increased the sensitivity of multiple cancer cell lines to spindle poisons, including nocodazole, vincristine, and Taxol. In the absence of p31 comet, lower concentrations of spindle poisons were required to induce mitotic block. The delay in checkpoint silencing was induced by an accumulation of mitotic checkpoint complexes. The increase in the duration of mitotic block after p31 comet depletion resulted in a dramatic increase in mitotic cell death upon challenge with spindle poisons. Significantly, cells that are normally prone to mitotic slippage and resistant to spindle disruption-mediated mitotic death were also sensitized after p31 comet depletion. These results highlight the importance of p31 comet in checkpoint silencing and its potential as a target for antimitotic therapies. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.