The role of Drosophila CID in kinetochore formation, cell-cycle progression and heterochromatin interactions

Centromere function requires the coordination of many processes including k inetochore assembly, sister chromatid cohesion, spindle attachment and chro mosome movement. Here we show that CID, the Drosophila homologue of the CEN P-A centromere-specific H3-like proteins, colocalizes with molecular-geneti cally defined functional centromeres in minichromosomes. Injection of CID a ntibodies into early embryos, as well as RNA interference in tissue-culture cells, showed that CID is required for several mitotic processes. Deconvol ution fluorescence microscopy showed that CID chromatin is physically separ ate from proteins involved in sister cohesion (MEI-S332), centric condensat ion (PROD), kinetochore function (ROD, ZW10 and BUB1) and heterochromatin s tructure (HP1). CID localization is unaffected by mutations in mei-S332, Su (var)2-5 (HP1), prod or polo. Furthermore, the localization of POLO, CENP-m eta, ROD, BUB1 and MEI-S332, but not PROD or HP1, depends on the presence o f functional CID. We conclude that the centromere and flanking heterochroma tin are physically and functionally separable protein domains that are requ ired for different inheritance functions, and that CID is required for norm al kinetochore formation and function, as well as cell-cycle progression.