Essential roles of Drosophila inner centromere protein (INCENP) and auroraB in histone H3 phosphorylation, metaphase chromosome alignment, kinetochore disjunction, and chromosome segregation

We have performed a biochemical and double-stranded RNA-mediated interferen ce (RNAi) analysis of the role of two chromosomal passenger proteins, inner centromere protein (INCENP) and aurora B kinase, in cultured cells of Duos ophila melanogaster. INCENP and aurora B function is tightly interlinked. T he two proteins bind to each other in vitro, and DmINCENP is required for D mAurora B to localize properly in mitosis and function as a histone H3 kina se. DmAu-rora B is required for DmINCENP accumulation at centromeres and tr ansfer to the spindle at anaphase. RNAi for either protein dramatically inh ibited the ability of cells to achieve a normal metaphase chromosome alignm ent. Cells were not blocked in mitosis, however, and entered an aberrant an aphase characterized by defects in sister kinetochore disjunction and the p resence of large amounts of amorphous lagging chromatin. Anaphase A chromos ome movement appeared to be normal, however cytokinesis often failed. DmINC ENP and DmAurora B are not required for the correct localization of the kin esin-like protein Pavarotti (ZEN-4/CHO1/MKLP1) to the midbody at telophase. These experiments :reveal that INCENP is required for aurora B kinase func tion and confirm that the chromosomal passengers have essential roles in mi tosis.