Cell Biology

Reinforcing the Scaffold

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Science  10 Mar 2006:
Vol. 311, Issue 5766, pp. 1347-1349
DOI: 10.1126/science.311.5766.1347d

During cell division, chromosomes condense into their stereotypical compact rod-like shapes, and this allows them to be manipulated efficiently by the mitotic spindle for partitioning into the daughter cells. Using fluorescence microscopy on live cells, Gerlich et al. examined the roles of the condensin proteins I and II in chromosome restructuring during mitosis. Condensin II remained associated with chromosomes throughout mitosis, whereas condensin I began to associate with chromosomes in prometaphase, after compaction had been completed in prophase. As mitosis progressed, the levels of chromosome-associated condensin I increased, until chromosomes had lined up on the mitotic spindle, for partitioning during anaphase. When levels of condensin I were reduced experimentally, chromosomes condensed normally, but during alignment and separation, the compacted chromosomes were mechanically unstable and more readily disrupted. In contrast, when levels of condensin II were reduced, condensed chromosomes remained robust enough to withstand partitioning. Thus, it seems that condensin I reinforces the scaffold of condensed chromosomes and helps them to withstand the forces applied as they interact with the mitotic spindle. — SMH

Curr. Biol. 16, 333 (2006).

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