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

2008 ◽  
Vol 19 (10) ◽  
pp. 4421-4433 ◽  
Author(s):  
Tariq H. Warsi ◽  
Michelle S. Navarro ◽  
Jeff Bachant

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.

1989 ◽  
Vol 9 (1) ◽  
pp. 159-168 ◽  
Author(s):  
C Holm ◽  
T Stearns ◽  
D Botstein

The hypothesis that DNA topoisomerase II facilitates the separation of replicated sister chromatids was tested by examining the consequences of chromosome segregation in the absence of topoisomerase II activity. We observed a substantial elevation in the rate of nondisjunction in top2/top2 cells incubated at the restrictive temperature for one generation time. In contrast, only a minor increase in the amount of chromosome breakage was observed by either physical or genetic assays. These results suggest that aneuploidy is a major cause of the nonviability observed when top2 cells undergo mitosis at the restrictive temperature. In related experiments, we determined that topoisomerase II must act specifically during mitosis. This latter observation is consistent with the hypothesis that the mitotic spindle is necessary to allow topoisomerase II to complete the untangling of sister chromatids.


1989 ◽  
Vol 9 (1) ◽  
pp. 159-168
Author(s):  
C Holm ◽  
T Stearns ◽  
D Botstein

The hypothesis that DNA topoisomerase II facilitates the separation of replicated sister chromatids was tested by examining the consequences of chromosome segregation in the absence of topoisomerase II activity. We observed a substantial elevation in the rate of nondisjunction in top2/top2 cells incubated at the restrictive temperature for one generation time. In contrast, only a minor increase in the amount of chromosome breakage was observed by either physical or genetic assays. These results suggest that aneuploidy is a major cause of the nonviability observed when top2 cells undergo mitosis at the restrictive temperature. In related experiments, we determined that topoisomerase II must act specifically during mitosis. This latter observation is consistent with the hypothesis that the mitotic spindle is necessary to allow topoisomerase II to complete the untangling of sister chromatids.


Author(s):  
Jason R. Swedlow ◽  
Neil Osheroff ◽  
Tim Karr ◽  
John W. Sedat ◽  
David A. Agard

DNA topoisomerase II is an ATP-dependent double-stranded DNA strand-passing enzyme that is necessary for full condensation of chromosomes and for complete segregation of sister chromatids at mitosis in vivo and in vitro. Biochemical characterization of chromosomes or nuclei after extraction with high-salt or detergents and DNAse treatment showed that topoisomerase II was a major component of this remnant, termed the chromosome scaffold. The scaffold has been hypothesized to be the structural backbone of the chromosome, so the localization of topoisomerase II to die scaffold suggested that the enzyme might play a structural role in the chromosome. However, topoisomerase II has not been studied in nuclei or chromosomes in vivo. We have monitored the chromosomal distribution of topoisomerase II in vivo during mitosis in the Drosophila embryo. This embryo forms a multi-nucleated syncytial blastoderm early in its developmental cycle. During this time, the embryonic nuclei synchronously progress through 13 mitotic cycles, so this is an ideal system to follow nuclear and chromosomal dynamics.


2010 ◽  
Vol 999 (999) ◽  
pp. 1-14 ◽  
Author(s):  
K. Chikamori ◽  
A.G. Grozav ◽  
T. Kozuki ◽  
D. Grabowski ◽  
R. Ganapathi ◽  
...  

1986 ◽  
Vol 261 (17) ◽  
pp. 8063-8069
Author(s):  
R A Heller ◽  
E R Shelton ◽  
V Dietrich ◽  
S C Elgin ◽  
D L Brutlag

2016 ◽  
Vol 103 ◽  
pp. 29-39 ◽  
Author(s):  
Ka C. Lee ◽  
Rebecca L. Bramley ◽  
Ian G. Cowell ◽  
Graham H. Jackson ◽  
Caroline A. Austin

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