A last-minute rescue of trapped chromatin.

University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, MA 01655, USA.
Cell (Impact Factor: 31.96). 03/2009; 136(3):397-9. DOI: 10.1016/j.cell.2009.01.028
Source: PubMed

ABSTRACT Chromosome segregation and cytokinesis must be tightly coordinated to ensure that chromosomes are accurately partitioned between dividing cells. In this issue, Steigemann et al. (2009) report that Aurora B kinase promotes proper chromosome segregation by delaying abscission when chromatin is trapped between dividing cells.

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    ABSTRACT: Aurora B kinase is an integral regulator of cytokinesis, as it stabilizes the intercellular canal within the midbody to ensure proper chromosomal segregation during cell division. Here we identified that the ubiquitin E3 ligase complex SCF(FBXL2) mediates Aurora B ubiquitination and degradation within the midbody, which is sufficient to induce mitotic arrest and apoptosis. Three molecular acceptor sites (K(102), K(103) and K(207)) within Aurora B protein were identified as important sites for its ubiquitination. A triple Lys mutant of Aurora B (K(102)/(103)/(207R)) exhibited optimal resistance to SCF(FBXL2)-directed polyubiquitination, and overexpression of this variant resulted in a significant delay in anaphase onset, resulting in apoptosis. A unique small molecule F-box/LRR-repeat protein 2 (FBXL2) activator, BC-1258, stabilized and increased levels of FBXL2 protein that promoted Aurora B degradation, resulting in tetraploidy, mitotic arrest and apoptosis of tumorigenic cells, and profoundly inhibiting tumor formation in athymic nude mice. These findings uncover a new proteolytic mechanism targeting a key regulator of cell replication that may serve as a basis for chemotherapeutic intervention in neoplasia.
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