The chromosomal passenger complex of Aurora B kinase, INCENP, and Survivin has essential regulatory roles at centromeres and the central spindle in mitosis. Borealin is also a member of the complex. Approximately half of Aurora B in mitotic cells is complexed with INCENP, Borealin, and Survivin. Depletion of Borealin by RNA interference delays mitotic progression and results in kinetochore-spindle mis-attachments and an increase in bipolar spindles associated with ectopic asters [1].

1: Borealin: a novel chromosomal passenger required for stability of the bipolar mitotic spindle. Gassmann R, Carvalho A, Henzing AJ, Ruchaud S, Hudson DF, Honda R, Nigg EA, Gerloff DL, Earnshaw WC; J Cell Biol. 2004;166:179-191. PMID:15249581