低于阈值水平的DNA拓扑异构酶会导致酵母核糖体DNA以染色体外环状形式被切除。

A subthreshold level of DNA topoisomerases leads to the excision of yeast rDNA as extrachromosomal rings.

作者信息

Kim R A, Wang J C

机构信息

Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.

出版信息

Cell. 1989 Jun 16;57(6):975-85. doi: 10.1016/0092-8674(89)90336-x.

DOI:10.1016/0092-8674(89)90336-x

PMID:2544296

Abstract

In a yeast DNA topoisomerase double mutant TG205 (delta top1 top2-4), over half of the rDNA is present as extrachromosomal rings containing one 9 kb unit of the rDNA gene or tandem repeats of it. Expression of a plasmid-borne TOP1 or TOP2 gene in the strain leads to the integation of the extrachromosomal rDNA rings back into the chromosomal rDNA cluster. When the plasmid-borne topoisomerase gene is expressed from an inducible promoter of the GAL1 gene, repression of the gene by dextrose leads to reappearance of the extrachromosomal rDNA rings. The DNA topoisomerase-dependent excision/integration of rDNA is discussed in terms of the possibility of rDNA supercoiling by transcription and the effects of DNA topology on intra- and interchromosomal recombination.

摘要

在酵母DNA拓扑异构酶双突变体TG205（top1缺失top2 - 4）中，超过一半的核糖体DNA（rDNA）以染色体外环状形式存在，这些环状结构包含一个9 kb的rDNA基因单位或其串联重复序列。在该菌株中表达质粒携带的TOP1或TOP2基因会导致染色体外rDNA环重新整合回染色体rDNA簇中。当质粒携带的拓扑异构酶基因由GAL1基因的可诱导启动子表达时，葡萄糖对该基因的抑制会导致染色体外rDNA环再次出现。从转录导致rDNA超螺旋的可能性以及DNA拓扑结构对染色体内和染色体间重组的影响方面讨论了rDNA的DNA拓扑异构酶依赖性切除/整合。