Drosophila Aurora B kinase is required for histone H3 phosphorylation and condensin recruitment during chromosome condensation and to organize the central spindle during cytokinesis

Aurora/Ipl1-related kinases are a conserved family of enzymes that have mul tiple functions during mitotic progression. Although it has been possible t o use conventional genetic analysis to dissect the function of aurora, the founding family member in Drosophila (Glover, D.M., M.H. Leibowitz, D.A. Mc Lean, and H. Parry. 1995. Cell. 81:95-105), the lack of mutations in a seco nd aurora-like kinase gene, aurora B, precluded this approach. We now show that depleting Aurora B kinase using double-stranded RNA interference in cu ltured Drosophila cells results in polyploidy. aurora B encodes a passenger protein that associates first with condensing chromatin, concentrates at c entromeres, and then relocates onto the central spindle at anaphase. Cells depleted of the Aurora B kinase show only partial chromosome condensation a t mitosis. This is associated with a reduction in levels of the serine 10 p hosphorylated form of histone H3 and a failure to recruit the Barren conden sin protein onto chromosomes. These defects are associated with abnormal se gregation resulting from lagging chromatids and extensive chromatin bridgin g at anaphase, similar to the phenotype of barren mutants (Bhat, M.A., A.V. Philp, D.M. Glover, and H.J. Bellen. 1996. Cell. 87:1103-1114.). The major ity of treated cells also fail to undertake cytokinesis and show a reduced density of microtubules in the central region of the spindle. This is accom panied by a failure to correctly localize the Pavarotti kinesin-like protei n, essential for this process. We discuss these conserved functions of Auro ra B kinase in chromosome transmission and cytokinesis.