We have constructed five new temperature-sensitive DNA topoisomerase II mutations and have analyzed their physiological consequences in yeast. Several lines of evidence suggest that the activity of topoisomerase II is required specifically at the time of miosis. First, top2 mutations cause dramatic lethality at the restrictive temperature, but only if the mutant cells are actively traversing the cell cycle. Second, temperature-shift experiments with synchronized cultures show that the onset of inviability coincides with the time of mitosis. Third, fluorescence microscopy reveals that the normal progression of mitosis is disturbed in mutant cells at the restrictive temperature. Finally, inviability at the restrictive temperature is prevented by nocodazole, an inhibitor of tubulin polymerization that prevents formation of the mitotic spindle. These results are consistent with the hypothesis that the essential function of topoisomerase II is to allow the separation of intertwined chromosomal DNA molecules during mitosis.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|