BUB1

BUB1 is a conserved mitotic checkpoint serine/threonine kinase that localizes to kinetochores through interaction of its BUB3-binding motif with phosphorylated MELT repeats of the KNL1 scaffold. At kinetochores BUB1 supports spindle assembly checkpoint signaling, recruits the chromosomal passenger complex, and phosphorylates histone H2A to help establish centromeric protection of cohesin during mitosis. BUB1 also contributes to chromosome congression and segregation independently of the checkpoint. Reduced or mutated BUB1 function produces chromosomal instability and aneuploidy, and altered BUB1 expression has been observed in tumors, making it a candidate target for aneuploidy-selective cancer therapy.