Haspin phosphorylates histone H3 at Thr3 (H3T3ph) during mitosis [1, 2], 
providing a chromatin binding site for the chromosomal passenger complex (CPC) 
at centromeres to regulate chromosome segregation [3-5]. H3T3ph becomes 
increasingly focused at inner centromeres during prometaphase [1, 2], but little 
is known about how its level or location and the consequent chromosomal 
localization of the CPC are regulated. In addition, CPC binding to shugoshin 
proteins contributes to centromeric Aurora B localization [5, 6]. Recruitment of 
the shugoshins to centromeres requires the phosphorylation of histone H2A at 
Thr120 (H2AT120ph) by the kinetochore kinase Bub1 [7], but the molecular basis 
for the collaboration of this pathway with H3T3ph has been unclear. Here, we 
show that Aurora B phosphorylates Haspin to promote generation of H3T3ph and 
that Aurora B kinase activity is required for normal chromosomal localization of 
the CPC, indicating an intimate linkage between Aurora B and Haspin functions in 
mitosis. We propose that Aurora B activity triggers a CPC-Haspin-H3T3ph feedback 
loop that promotes generation of H3T3ph on chromatin. We also provide evidence 
that the Bub1-shugoshin-CPC pathway supplies a signal that boosts the 
CPC-Haspin-H3T3ph feedback loop specifically at centromeres to produce the 
well-known accumulation of the CPC in these regions.