Aurora B/AIR-2 regulates sister centromere resolution and CENP-A/HCP-3 organization to prevent merotelic attachments.

During cell division, the accurate capture of sister kinetochores that are built on the centromeres of chromosomes by microtubules emanating from opposite spindle poles governs faithful chromosome segregation. To ensure sister chromatids separate correctly, sister centromeres undergo resolution to achieve bi-polar orientation prior to microtubule attachments. Failure of centromere resolution increases the frequency of merotelic attachments, with microtubules from opposite poles attaching to the same sister kinetochore, causing lagging chromosome, aneuploidy, and even cancer progression. The Aurora B-mediated tension-sensing machinery to correct erroneous kinetochore-microtubule attachments has been well studied. However, preventative mechanisms to avoid merotelic attachments that occur in the earlier mitotic stage are poorly understood. In this study, we found that inactivation of mitotic kinase Aurora B/AIR-2 increases merotelic attachments in Caenorhabditis elegans. On one hand, Aurora B/AIR-2-deficient cells exhibited a delay in the occurrence of centromere resolution and a disruption in targeting condensin II components to chromatin. On the other hand, loss of Aurora B/AIR-2 results in an increased localization of centromeric proteins CENP-A/HCP-3 and M18BP1/KNL-2 as well as the kinetochore protein MIS-12 on chromatin, which may generate ectopic kinetochores causing erroneous attachments. To conclude, this study elucidated that Aurora B/AIR-2 regulates sister centromere resolution and CENP-A/HCP-3 deposition to actively prevent merotely and chromosome instability in cells.