Abstract
Proper deposition and activation of Aurora B at the centromere is critical for faithful chromosome segregation in mammals. However, the mechanistic basis for abrupt Aurora B kinase activation at the centromere has not yet been fully understood. We demonstrate here that Aurora B-mediated phosphorylation of histone H2AX at serine 121 (H2AX-pS121) promotes Aurora B autophosphorylation and is essential for proper chromosome segregation. Aurora B-mediated H2AX-pS121 is specifically detected at the centromere during mitosis. H2AX depletion results in a severe defect in activation and deposition of Aurora B at this locus. A phosphomimic mutant of H2AX at S121 interacts with activated Aurora B more efficiently than wild-type in vitro. Taken together, these results propose a model in which Aurora B-mediated H2AX-pS121 probably provide a platform for Aurora B autoactivation circuitry at centromeres and thus play a pivotal role in proper chromosome segregation.
Highlights
Proper deposition and activation of Aurora B at the centromere is critical for faithful chromosome segregation in mammals
Aurora B kinase activity itself is essential for forcing chromosomal passenger complex (CPC) to localize to the inner centromere[16,17], at least in part through a positive feedback loop between Haspin and Aurora B18
As H2AX is involved in the maintenance of genome integrity and H2AX À / À mouse embryonic fibroblasts (MEFs) can be cultured for long periods, a defect in cell proliferation in H2AX À / À MEFs might result from the accumulation of gene abnormalities that might affect cell cycle progression
Summary
H2AX is required for proper chromosome segregation. Given that H2AX knockout (KO) mice are growth retarded[29], we speculated that this H2A variant could function in normal cell cycle progression. Similar types of mitotic abnormalities were observed in Aurora B-depleted (shAurora B) and Haspin-depleted (shHaspin) HeLa cells, both kinases which are known to be essential for proper chromosome segregation (Fig. 1b), suggesting that the defects in the cell proliferation of H2AX-KD cells appeared to be due to mitotic abnormalities. Such abnormalities were not detected or only barely detected in control HeLa cells. Chromosome spread analysis demonstrated that H2AX depletion resulted in a reduction in Aurora B and more markedly its active phosphorylation at centromeres, and an increase in Aurora B on chromosome arms (Fig. 3c). Haspin-mediated H3-pT3 and a hH2A hH2AX b
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