Bub1b also known as BUB1beta, BUBR1 is a kinase involved in spindle checkpoint function. Bub1b plays a critical role in the mitotic checkpoint, ensuring that chromosomes are properly aligned before cell division proceeds. Bub1b localizes to the kinetochore, where Bub1b interacts with microtubules to monitor their attachment and stability. This localization prevents the premature separation of sister chromatids, safeguarding genomic integrity during cell division. Disruption of Bub1b function can lead to aneuploidy and has been implicated in various cancers, highlighting Bub1b′s importance in maintaining proper cell cycle regulation. Bub1b interacts with other key proteins such as BUB3, which is essential for the spindle assembly checkpoint, further underscoring Bub1b′s role in the complex network of proteins that govern mitosis.