Overview:

BUB1B or budding uninhibited by benzimidazoles 1 homolog beta is involved in spindle checkpoint function and has been localized to the kinetochore. BUB1B plays a role in the inhibition of the anaphase-promoting complex/cyclosome (APC/C), delaying the onset of anaphase and ensuring proper chromosome segregation (1). BUB1B links the regulation of chromosome-spindle attachment to mitotic checkpoint signaling (2). BUB1B expression during the spindle checkpoint is dependent on residual BUB1B expression and impaired spindle checkpoint function has been found in many forms of cancer. BUB1B is essential for early embryonic development and normal hematopoiesis.

References:

1. Rio Frio. Et.al: Homozygous BUB1B mutation and susceptibility to gastrointestinal neoplasia. New Eng. J. Med. 363: 2628-2637, 2010. 

2. Lampson, M. A., Kapoor. et.al: The human mitotic checkpoint protein BubR1 regulates chromosome-spindle attachments. Nature Cell Biol. 7: 93-98, 2005.