The ZW10 and Rough Deal checkpoint proteins function together in a large, evolutionarily conserved complex targeted to the kinetochore

The zeste-white 10 (zw10) and rough deal (rod) genes of Drosophila both enc ode kinetochore components, and mutations in either gene greatly increase t he missegregation of sister chromatids during mitosis. Here, we present gen etic, cytological and biochemical evidence for a close, evolutionarily cons erved relationship between the ROD and ZW10 proteins. We show that the phen otypes caused by disruption of either gene's function are similar in Drosop hila and in C elegans. No additive effects are observed in zw10; rod double null mutants. In flies, the two proteins always colocalize and, moreover, require each other for their recruitment to the mitotic apparatus. The huma n ROD and ZW10 homologs also colocalize on HeLa cell kinetochores or kineto chore microtubules throughout most but not all of mitosis. Finally, we show that in both Drosophila and human cells, ROD and ZW10 are in fact physical ly associated, and in Drosophila these proteins are together constituents o f a large (700-900 kDa), soluble macromolecular complex.