Phosphorylation of histone H3 is similar in EnM and mitosis and is ablated by an inhibitor of aurora kinase. (A) EnM murine MK and mitotic cell adjacent to each other allowing direct comparison of phosphorylation of histone H3. Phospho-histone H3 is shown in green; tubulin is stained in red. (B) Murine MKs were purified and incubated for 2 hours with either vehicle (DMSO) or 5 μM ZM447439 prior to fixation and immunostaining for phospho-histone H3 (green). (C) Spindle structure in MKs treated with an aurora inhibitor is not the same as that in MKs treated with an Eg5 inhibitor. Murine MKs were incubated for 2 hours with either 5 μM ZM447439 or 100 μM monastrol prior to fixation and immunostaining for tubulin and phospho-histone H3.