A pivot-tether model for nucleosome recognition by the chromosomal passenger complex
Spatial restriction of Aurora B to centromeres during prometaphase and metaphase enables it to phosphorylate proteins necessary for spindle assembly checkpoint signalling and biorientation of chromosomes on the mitotic spindle. Aurora B binding to T3-phosphorylated histone H3 (H3pT3) nucleosomes requires a multivalent targeting module, the chromosomal passenger complex (CPC), consisting of survivin, borealin, and INCENP. To shed light on how these components mediate CPC localisation during prometaphase and metaphase, we determined the structure of the CPC targeting module in complex with haspin-phosphorylated H3pT3-nucleosomes by cryo-electron microscopy. This structure shows how the N-terminus of borealin and the survivin BIR domain act as pivot and flexible tethering points, respectively, to increase CPC affinity for H3pT3 nucleosomes without limiting it to a specific orientation. We demonstrate that this flexible, yet constrained pivot-tether arrangement is important for the control of spindle assembly checkpoint signalling by Aurora B.