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Originally published as MBC in Press, 10.1091/mbc.E08-05-0547 on August 13, 2008

Vol. 19, Issue 10, 4421-4433, October 2008

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DNA Topoisomerase II Is a Determinant of the Tensile Properties of Yeast Centromeric Chromatin and the Tension Checkpoint

Tariq H. Warsi, Michelle S. Navarro, and Jeff Bachant

Department of Cell Biology and Neuroscience, University of California, Riverside, Riverside, CA 92521

Submitted June 2, 2008; Revised July 29, 2008; Accepted August 6, 2008
Monitoring Editor: Kerry S. Bloom

InCytes from MBC

Centromeric (CEN) chromatin is placed under mechanical tension and stretches as kinetochores biorient on the mitotic spindle. This deformation could conceivably provide a readout of biorientation to error correction mechanisms that monitor kinetochore–spindle interactions, but whether CEN chromatin acts in a tensiometer capacity is unresolved. Here, we report observations linking yeast Topoisomerase II (Top2) to both CEN mechanics and assessment of interkinetochore tension. First, in top2-4 and sumoylation-resistant top2-SNM mutants CEN chromatin stretches extensively during biorientation, resulting in increased sister kinetochore separation and preanaphase spindle extension. Our data indicate increased CEN stretching corresponds with alterations to CEN topology induced in response to tension. Second, Top2 potentiates aspects of the tension checkpoint. Mutations affecting the Mtw1 kinetochore protein activate Ipl1 kinase to detach kinetochores and induce spindle checkpoint arrest. In mtw1top2-4 and mtw1top2-SNM mutants, however, kinetochores are resistant to detachment and checkpoint arrest is attenuated. For top2-SNM cells, CEN stretching and checkpoint attenuation occur even in the absence of catenation linking sister chromatids. In sum, Top2 seems to play a novel role in CEN compaction that is distinct from decatenation. Perturbations to this function may allow weakened kinetochores to stretch CENs in a manner that mimics tension or evades Ipl1 surveillance.

This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E08-05-0547) on August 13, 2008.

Address correspondence to: Jeff Bachant (jeffbach{at}citrus.ucr.edu)

Abbreviations used: APC, anaphase promoting complex; CEN, centromere; GFP, green fluorescent protein; NZ, nocodazole; SAC, spindle assembly checkpoint; Topo II, DNA topoisomerase II; WT, wild type.


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