Mitotic spindle pulls but fails to separate chromosomes in type II DNA topoisomerase mutants: uncoordinated mitosis
Mitotic spindle pulls but fails to separate chromosomes in type II DNA topoisomerase mutants: uncoordinated mitosis
复制标题
II 型 DNA 拓扑异构酶突变体中有丝分裂纺锤体拉动但无法分离染色体：不协调的有丝分裂
DOI：
10.1002/j.1460-2075.1986.tb04315.x
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
M. Yanagida
中科院分区：
文献类型：
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作者：
T. Uemura;M. Yanagida
裂变酵母top2基因座由五个温度敏感性突变定义，这些突变导致细胞提取物中II型DNA拓扑异构酶的热不稳定活性。我们表明，顶2位点是II型拓扑异构酶的结构基因，通过克隆的基因组DNA片段，补充顶2。在限制性温度下，top2突变体在有丝分裂时产生异常染色体;这些染色体随伸长的有丝分裂纺锤体沿着暂时延伸成丝状结构，但不分离。top2的一个主要缺陷似乎是形成异常有丝分裂染色体的纺锤体产生的力不可分割的。一致地，在有丝分裂期间变得致死的前2个细胞含有ARS质粒的链状二聚体。如果胞质分裂被阻断，DNA和RNA继续合成。不协调的有丝分裂，即没有染色体分离的纺锤体动力学的发生，在top2中被揭示，并讨论了与有丝分裂调控的关系。本文中描述的top2和top1-top2之间的不同表型可以通过先前提出的假设来解释，即II型拓扑异构酶具有双重体内功能：一个是decatenates和unknots双链DNA是必不可少的有丝分裂，而另一个是松弛超螺旋是整个细胞周期所需的，如果I型拓扑异构酶是缺席的。
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 that the top2 locus is a structural gene for type II toposiomerase by cloning a genomic DNA fragment that complements top2. The top2 mutants at restrictive temperature produce abnormal chromosomes at the time of mitotis; these are transiently extended into filamentous structures along with the elongating mitotic spindle but are not separated. A primary defect in top2 appears to be the formation of aberrant mitotic chromosomes inseparable by the force generated by the spindle apparatus. Consistently, the top2 cells that become lethal during mitotis contain a catenated dimer of an ARS plasmid. DNA and RNA continue to be synthesized if cytokinesis is blocked. Uncoordinated mitosis, that is the occurrence of spindle dynamics without chromosome separation, is revealed in top2, and is discussed in relation to mitotic regulation. Different phenotypes between top2 and top1–top2 described in the present paper can be explained by a previously proposed hypothesis that type II topoisomerase has dual in vivo functions: one that decatenates and unknots duplex DNAs is essential in mitotis, whereas the other which relaxes supercoils is required throughout the cell cycle if type I topoisomerase is absent.