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Molecular and Cellular Biology, May 2005, p. 4046-4061, Vol. 25, No. 10
0270-7306/05/$08.00+0     doi:10.1128/MCB.25.10.4046-4061.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Transcriptional Control of BubR1 by p53 and Suppression of Centrosome Amplification by BubR1

Laboratory of Veterinary Internal Medicine, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515,¹ Department of Veterinary Internal Medicine, Graduate Schools of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan,⁴ Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521,² Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105³

Received 18 January 2005/ Returned for modification 27 January 2005/ Accepted 31 January 2005

Elimination of the regulatory mechanism underlying numeral homeostasis of centrosomes, as seen in cells lacking p53, results in abnormal amplification of centrosomes, which increases the frequency of chromosome segregation errors, and thus contributes to the chromosome instability frequently observed in cancer cells. We have previously reported that p53^–/– mouse cells in prolonged culture undergo genomic convergence similar to that observed during tumor progression; early-passage p53^–/– cells are karyotypically heterogeneous due to extensive chromosome instability associated with centrosome amplification, while late-passage p53^–/– cells are aneuploid yet karyotypically homogeneous and chromosomally stable. Moreover, they contain numerically normal centrosomes. Through the microarray analysis of early- and late-passage p53^–/– cells, we identified the BubR1 spindle checkpoint protein, which plays a critical role in suppression of centrosome amplification and stabilization of chromosomes in late-passage p53^–/– cells. Up-regulation of BubR1 augments the checkpoint function, which effectively senses the spindle/chromosome aberrations associated with centrosome amplification. We further found that BubR1 transcription is largely controlled by p53. In early-passage p53^–/– cells, BubR1 expression is low and the checkpoint function in response to microtubule toxin is considerably compromised. In late-passage cells, however, regaining of BubR1 expression restores the checkpoint function to mitotic aberrations caused by microtubule toxin. Our studies demonstrate the molecular aspect of genomic convergence in cultured cells, providing critical information for understanding the stepwise progression of tumors.

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