Successful partitioning of chromosomes in mitosis relies on the bipolar 
attachment of sister chromatids at metaphase. For this biorientation, the 
chromosomal passenger complex (CPC), composed of catalytic kinase Aurora B and 
regulatory components (INCENP, Survivin, and Borealin), must be localized at the 
center of paired kinetochores, the site called the inner centromere. It is 
largely unknown what defines the inner centromere and how the CPC is targeted to 
this site. Recent studies point out that the shugoshin protein (SGO), originally 
identified as a cohesin protector, also acts as a conserved centromeric adapter 
of the CPC. Phosphorylation of the CPC by Cdk1 promotes direct binding with 
shugoshin, thus explaining how the CPC is targeted to the centromere in a timely 
manner at prometaphase during the cell cycle. Moreover, the phosphorylation of 
histone H3 threonine 3 (H3-pT3) mediated by Haspin cooperates with Bub1-mediated 
H2A-S121 phosphorylation in targeting the CPC to the inner centromere. H3-pT3 
promotes nucleosome binding of Survivin, whereas H2A-pS121 facilitates the 
binding of shugoshin. Haspin colocalizes with cohesin by associating with Pds5, 
a cohesin-binding protein, and Bub1 localizes at kinetochores. Thus, the inner 
centromere is defined by the spatial intersection of two histone marks mediated 
by cohesin- and kinetochore-associated kinases.