Aurora kinase promotes turnover of kinetochore microtubules to reduce chromosome segregation errors

Merotelic kinetochore orientation is a misattachment in which a single kinetochore binds microtubules from both spindle poles rather than just one and can produce anaphase lagging chromosomes, a major source of aneuploidy [1]. Merotelic kinetochore orientation occurs frequently in early mitosis, does not block chromosome alignment at the metaphase plate, and is not detected by the spindle checkpoint [2-5]. However, microtubules to the incorrect pole are usually significantly reduced or eliminated before anaphase [3, 6]. We discovered that the frequency of lagging chromosomes in anaphase is very sensitive to partial inhibition of Aurora kinase activity by ZM447439 at a dose, 3 mu M, that has little effect on histone phosphorylation, metaphase chromosome alignment, and cytokinesis in PtK1 cells. Partial Aurora kinase inhibition increased the frequency of merotelic kinetochores in late metaphase, and the fraction of microtubules to the incorrect pole. Measurements of fluorescence dissipation after photoactivation showed that kinetochore-microtubule turnover in prometaphase is substantially suppressed by partial Aurora kinase inhibition. Our results support a preanaphase correction mechanism for merotelic attachments in which correct plus-end attachments are pulled away from high concentrations of Aurora B at the inner centromere, and incorrect merotelic attachments are destabilized by being pulled toward the inner centromere.