NEED FOR DNA TOPOISOMERASE ACTIVITY AS A SWIVEL FOR DNA-REPLICATION FOR TRANSCRIPTION OF RIBOSOMAL-RNA
NEED FOR DNA TOPOISOMERASE ACTIVITY AS A SWIVEL FOR DNA-REPLICATION FOR TRANSCRIPTION OF RIBOSOMAL-RNA
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DOI：
10.1038/326414a0
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发表时间：
1987-03-26
期刊：
影响因子：
64.8
通讯作者：
STERNGLANZ, R
中科院分区：
文献类型：
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作者：
BRILL, SJ;DINARDO, S;STERNGLANZ, R
在酵母菌中，DNA拓扑异构酶I和II基因突变的酵母菌株先前已在Saccharomyces gonae 1 - 3和Schizosophylomycespombe 4中鉴定。拓扑异构酶II突变体（top2）是条件致死温度敏感（ts）突变体。它们在终止DNA复制和分离子染色体2 -5方面有缺陷，但在其他方面似乎可以正常复制和转录DNA。拓扑异构酶I突变体（top1），包括无效突变的菌株是可行的，并没有表现出明显的生长缺陷，表明DNA拓扑异构酶I是不是必不可少的酵母中的活力1，4，6，7。与单突变体相比，来自裂殖酵母和酵母的top1 top2 ts双突变体在允许温度下生长不良，在非允许温度下迅速停止生长4，7。在这里，我们报告说，DNA和核糖体RNA的合成显着抑制在一个S。在限制性温度下，酿酒酵母top1 top2 ts双突变体，但是poly（A）+RNA合成的速率仅降低约三倍，而转移RNA合成保持相对正常。结果表明，DNA复制和至少核糖体RNA的合成需要一个活跃的拓扑异构酶，大概是作为一个旋转，以减轻扭转应力，和拓扑异构酶可以执行所需的功能（除了在终止DNA复制，拓扑异构酶II是必需的）。
Yeast strains with mutations in the genes for DNA topoisomerases I and II have been identified previously in bothSaccharomyces cerevisiae1–3andSchizosaccharomyces pombe4. The topoisomerase II mutants (top2) are conditional-lethal temperature-sensitive (ts) mutants. They are defective in the termination of DNA replication and the segregation of daughter chromosomes2–5, but otherwise appear to replicate and transcribe DNA normally. Topoisomerase I mutants (top1), including strains with null mutations are viable and exhibit no obvious growth defects, demonstrating that DNA topoisomerase I is not essential for viability in yeast1,4,6,7. In contrast to the single mutants,top1 top2ts double mutants from bothSchizosaccharomyces pombeandSaccharomyces cerevisiaegrow poorly at the permissive temperature and stop growth rapidly at the non-permissive temperature4,7. Here we report that DNA and ribosomal RNA synthesis are drastically inhibited in anS. cerevisiae top1 top2ts double mutant at the restrictive temperature, but that the rate of poly(A)+RNA synthesis is reduced only about threefold and transfer RNA synthesis remains relatively normal. The results suggest that DNA replication and at least ribosomal RNA synthesis require an active topoisomerase, presumably to act as a swivel to relieve torsional stress, and that either topoisomerase can perform the required function (except in termination of DNA replication where topoisomerase II is required).