Mitotic spindle pulls but fails to separate chromosomes in type II DNA topoisomerase mutants: uncoordinated mitosis.

摘要: Abstract The fission yeast top2 locus is defined by five temperature-sensitive mutations that cause heat-labile activity of type II DNA topoisomerase in the cell extracts. We show a structural gene for toposiomerase cloning genomic fragment complements top2. The mutants at restrictive temperature produce abnormal chromosomes time mitotis; these are transiently extended into filamentous structures along with elongating mitotic spindle but not separated. A primary defect appears to be formation aberrant inseparable force generated apparatus. Consistently, cells become lethal during mitotis contain catenated dimer an ARS plasmid. and RNA continue synthesized if cytokinesis blocked. Uncoordinated mitosis, occurrence dynamics without chromosome separation, revealed top2, discussed relation regulation. Different phenotypes between top1–top2 described present paper can explained previously proposed hypothesis has dual vivo functions: one decatenates unknots duplex DNAs essential mitotis, whereas other which relaxes supercoils required throughout cycle I absent.