Aurora A kinase phosphorylates Hec1 to regulate metaphase kinetochore-microtubule dynamics.

Precise regulation of kinetochore-microtubules 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/NDC80, which is a component of the NDC80 complex, a force-transducing link between kinetochores and microtubules. While Aurora B is regarded as the “master regulator” of kinetochore-microtubule attachment, it is likely that other mitotic kinases contribute to Hec1phosphorylation. Here we show that Aurora A kinase phosphorylates the tail domain of Hec1 at Serine 69, a previously uncharacterized phosphorylation target site, and plays an important role in controlling kinetochore-microtubule attachment dynamics. Using phospho-specific antibodies, Hec1 phospho-deficient mutants, and kinase inhibitors, we demonstrate that Aurora A is required for the regulation of kinetochore-microtubule dynamics of metaphase chromosomes and identify Hec1 Serine 69 as a critical Aurora A substrate for this regulation. Additionally, we demonstrate that Aurora A kinase associates with 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 Aurora B contribute to kinetochore-microtubule attachment dynamics, and they uncover an unexpected role for Aurora A in mitosis.