NOVEL TOPOLOGICALLY KNOTTED DNA FROM BACTERIOPHAGE P4 CAPSIDS - STUDIES WITH DNA TOPOISOMERASES
NOVEL TOPOLOGICALLY KNOTTED DNA FROM BACTERIOPHAGE P4 CAPSIDS - STUDIES WITH DNA TOPOISOMERASES
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DOI：
10.1093/nar/9.16.3979
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发表时间：
1981-01-01
影响因子：
14.9
通讯作者：
CALENDAR, R
中科院分区：
文献类型：
--
作者：
LIU, LF;DAVIS, JL;CALENDAR, R
从噬菌体P4中分离的DNA分子大多是线性的，具有内聚末端，能够形成环状和串联结构。相比之下，几乎所有从P4无尾衣壳（头部）分离的DNA分子都是单体DNA环，其内聚端是氢键。与简单的DNA环不同，这种P4头DNA环包含拓扑结。P4头部DNA的凝胶电泳和电镜分析表明，拓扑结是高度复杂和异质性的。用各种DNA拓扑异构酶研究了这种复杂结的分解。II型DNA拓扑异构酶可以催化两个交叉的双链DNA片段的拓扑传递（Liu， L. F., Liu， C. C. & Alberts， B. M.(1980) Cell, 19, 697-707）)，证明高度结的P4 DNA转化为简单的圆形。即使存在过量的I型DNA拓扑异构酶，结P4头DNA也可用于检测II型DNA拓扑异构酶的灵敏测定。
DNA molecules isolated from bacteriophage P4 are mostly linear with cohesive ends capable of forming cicular and concatemeric structures. In contrast, almost all DNA molecules isolated from P4 tailless capsids(heads) are monomeric DNA circles with their cohesive ends hydrogen-bonded. Different from simple DNA circles, such P4 head DNA circles contain topological knots. Gel electrophoretic and electronmicroscopic analyses of P4 head DNA indicate that the topological knots are highly complex and heterogeneous. Resolution of such complex knots has been studied with various DNA topoisomerases. The conversion of highly knotted P4 DNA to its simple circular form is demonstrated by type II DNA topoisomerases which catalyze the topological passing of two crossing double-stranded DNA segments{Liu, L. F., Liu, C. C. & Alberts, B. M.(1980) Cell, 19, 697–707}. The knotted P4 head DNA can be used in a sensitive assay for the detection of a type II DNA topoisomerase even in the presence of excess type I DNA topoisomerases.