Required for high-fidelity chromosome segregation during the later part of each cell cycle. Acts in opposition to the phosphatase PP1. Has a role in attaching the kinetochores to the microtubules and ensuring that sister kinetochores connect to opposite poles. The promotion of bi-orientation is achieved by selectively detaching kinetochore-microtubule attachments that are not under tension. Phosphorylates histone H3 to form H3S10ph during mitosis and meiosis. Phosphorylates RGD1 in vitro. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Associates with the mitotic spindle and on elongated and disassembling spindles. Also associated with the kinetochore. Present with 149 molecules/cell in log phase SD medium. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. Aurora subfamily.