Aurora kinase is required for chromosome segregation in tobacco BY-2 cells.

Post-translational modifications of core histone tails play crucial roles in chromatin structure and function. Although phosphorylation of Ser10 and Ser28 (H3S10ph and H3S28ph) of histone H3 is ubiquitous among eukaryotes, the phosphorylation mechanism during the cell cycle remains unclear. In the present study, H3S10ph and H3S28ph in tobacco BY-2 cells were observed in the pericentromeric regions during mitosis. Moreover, the Aurora kinase inhibitor Hesperadin inhibited the kinase activity of Arabidopsis thaliana Aurora kinase 3 (AtAUR3) in phosphorylating both Ser10 and Ser28 of histone H3 in vitro. Consistently, Hesperadin inhibited both H3S10ph and H3S28ph during mitosis in BY-2 cells. These results indicate that plant Aurora kinases phosphorylate not only Ser10, but also Ser28 of histone H3 in vivo. Hesperadin treatment increased the ratio of metaphase cells, while the ratio of anaphase/telophase cells decreased, although the mitotic index was not affected in Hesperadin-treated cells. These results suggest that Hesperadin induces delayed transition from metaphase to anaphase, and early exit from mitosis after chromosome segregation. In addition, micronuclei were observed frequently and lagging chromosomes, caused by the delay and failure of sister chromatid separation, were observed at anaphase and telophase in Hesperadin-treated BY-2 cells. The data obtained here suggest that plant Aurora kinases and H3S10ph/H3S28ph may have a role in chromosome segregation and metaphase/anaphase transition.