BUB1 is a kinase which involved in spindle checkpoint function that in part by phosphorylating a member of the miotic checkpoint complex and activating the spindle checkpoint. BUB1 is highly expreesed in thymus, ovary, and testis (1). BUB1 maintains the steady-state level and centromeric localization of SGO1, and they concluded that BUB1 protects centromeric cohesion in mitosis through SGO1 (2). BUB1-mediated phosphorylation of CDC20 is required for proper checkpoint signaling and that inhibition of APC by BUB1 may partly account for the sensitivity of the spindle checkpoint. BUB1 kinase creates a mark for shugoshin localization and the correct partitioning of chromosomes.