Human Zw10 and ROD ave mitotic checkpoint proteins that bind to kinetochores

Here we show that human Zeste White 10 (Zw10) and Rough deal (Rod) are new components of the mitotic checkpoint, as cells lacking these proteins at ki netochores fail to arrest in mitosis when exposed to microtubule inhibitors . Checkpoint failure and premature mitotic exit may explain why cells defec tive for hZw10 and hRod divide with lagging chromosomes. As Zw10 and Rod ar e not conserved in yeast, our data, combined with an accompanying study of Drosophila Zw10 and Rod, indicate that metazoans may require an elaborate s pindle checkpoint to monitor complex kinetochore functions.