Required for proper alignment of chromosomes at metaphase and their accurate segregation during mitosis. Involved in the maintenance of spindle microtubules attachment to the kinetochore during sister chromatid biorientation. May recruit CENPE and CENPF to the kinetochore. Interacts with MAD2L2. Interacts with POGZ, CBX1, CBX3 and CBX5. Phosphorylated by CDK1. Mitotic phosphorylation is required for the attachment of spindle microtubules to the kinetochore. Extended N-terminus. Truncated N-terminus.