Rough deal and Zw10 are required for the metaphase checkpoint in Drosophila

The metaphase-anaphase transition during mitosis is carefully regulated in order to assure high-fidelity transmission of genetic information to the da ughter cells. A surveillance mechanism known as the metaphase checkpoint (o r spindle-assembly checkpoint) monitors the attachment of kinetochores to t he spindle microtubules, and inhibits anaphase onset until all chromosomes have achieved a proper bipolar orientation on the spindle. Defects in this checkpoint lead to premature anaphase onset, and consequently to greatly in creased rates of aneuploidy. Here we show that the Drosophila kinetochore c omponents Rough deal (Rod) and Zeste-White 10 (Zw10) are required for the p roper functioning of the metaphase checkpoint in flies. Drosophila cells la cking either ROD or ZwlO exhibit a phenotype that is similar to that of bub 1 mutants - they do not arrest in metaphase in response to spindle damage, but instead separate sister chromatids, degrade cyclin B and exit mitosis. These ave the first checkpoint components to be identified that do not have obvious homologues in budding yeast.