title: Transcriptional control of BubR1 by p53 and suppression of centrosome amplification by BubR1.
abstract: 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.
authors.affiliation: Laboratory of Veterinary Internal Medicine, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Oikawa
authors.forename: Masaru
authors.initials: M
authors.lastname: Okuda
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Ma
authors.forename: Rakesh
authors.initials: R
authors.lastname: Goorha
authors.forename: Hajime
authors.initials: H
authors.lastname: Tsujimoto
authors.forename: Hisashi
authors.initials: H
authors.lastname: Inokuma
authors.forename: Kenji
authors.initials: K
authors.lastname: Fukasawa
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D018385:Centrosome / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005784:Gene Amplification / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D051379:Mice; D011494:Protein Kinases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000502:physiology; D014158:Transcription, Genetic / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: C584278:Bub1b protein, mouse; D018797:Cell Cycle Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D011494:Protein Kinases; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases