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Mol Biol Cell. 2009 Apr;20(8):2218-28. doi: 10.1091/mbc.E08-08-0885. Epub 2009 Feb 18.

Aurora B kinase regulates the postmitotic endoreduplication checkpoint via phosphorylation of the retinoblastoma protein at serine 780.

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  • 1Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

Abstract

The phenotypic change characteristic of Aurora B inhibition is the induction of polyploidy. Utilizing specific siRNA duplexes and a selective small molecule inhibitor (AZD1152) to inhibit Aurora B activity in tumor cells, we sought to elucidate the mechanism by which Aurora B inhibition results in polyploidy. Cells treated with AZD1152 progressed through mitosis with misaligned chromosomes and exited without cytokinesis and subsequently underwent endoreduplication of DNA despite activation of a p53-dependent pseudo G1 checkpoint. Concomitant with polyploid cell formation, we observed the appearance of Rb hypophosphorylation, an event that occurred independently of cyclin-dependent kinase inhibition. We went on to discover that Aurora B directly phosphorylates Rb at serine 780 both in vitro and in vivo. This novel interaction plays a critical role in regulating the postmitotic checkpoint to prevent endoreduplication after an aberrant mitosis. Thus, we propose for the first time that Aurora B determines cellular fate after an aberrant mitosis by directly regulating the Rb tumor suppressor protein.

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