Direct Nucleosome Binding of Borealin Secures Chromosome Association of the Chromosomal Passenger Complex

CPC-NCP complexes were crosslinked using EDC and analysed by mass spectrometry. The results showed Borealin is critical for nucleosome binding made extensive contacts with NCPs, whereas Survivin interactions are mostly limited to the BIR domain and the H3 N-terminal tail as expected. Mapping the crosslinks onto the three dimensional structures of NCP and CPC suggests a model where the localisation module of the CPC together with a highly basic N-terminal tail of Borealin docks onto the acidic patch formed by H2A and H2B, a surface commonly involved in nucleosome recognition. This interaction may orient the Survivin BIR domain to facilitate binding of histone H3 tail phosphorylated at Thr3. Notably, Borealin loop residues trace along the DNA-histone interface implying its major contribution to nucleosome binding involves both protein-histone and possibly protein-DNA contacts.