Precise regulation of kinetochore-microtubule attachments is essential for 
successful chromosome segregation. Central to this regulation is Aurora B 
kinase, which phosphorylates kinetochore substrates to promote microtubule 
turnover. A critical target of Aurora B is the N-terminal "tail" domain of Hec1, 
which is a component of the NDC80 complex, a force-transducing link between 
kinetochores and microtubules. Although Aurora B is regarded as the "master 
regulator" of kinetochore-microtubule attachment, other mitotic kinases likely 
contribute to Hec1 phosphorylation. In this study, we demonstrate that Aurora A 
kinase regulates kinetochore-microtubule dynamics of metaphase chromosomes, and 
we identify Hec1 S69, a previously uncharacterized phosphorylation target site 
in the Hec1 tail, as a critical Aurora A substrate for this regulation. 
Additionally, we demonstrate that Aurora A kinase associates with inner 
centromere protein (INCENP) during mitosis and that INCENP is competent to drive 
accumulation of the kinase to the centromere region of mitotic chromosomes. 
These findings reveal that both Aurora A and B contribute to 
kinetochore-microtubule attachment dynamics, and they uncover an unexpected role 
for Aurora A in late mitosis.