Wang H, Di Gate R J, Seeman N C
Department of Chemistry, New York University, NY 10003, USA.
Proc Natl Acad Sci U S A. 1996 Sep 3;93(18):9477-82. doi: 10.1073/pnas.93.18.9477.
A synthetic strand of RNA has been designed so that it can adopt two different topological states (a circle and a trefoil knot) when ligated into a cyclic molecule. The RNA knot and circle have been characterized by their behavior in gel electrophoresis and sedimentation experiments. This system allows one to assay for the existence of an RNA topoisomerase, because the two RNA molecules can be inter-converted only by a strand passage event. We find that the interconversion of these two species can be catalyzed by Escherichia coli DNA topoisomerase III, indicating that this enzyme can act as an RNA topoisomerase. The conversion of circles to knots is accompanied by a small amount of RNA catenane generation. These findings suggest that strand passage must be considered a potential component of the folding and modification of RNA structures.
已设计出一段合成RNA链，使其在连接成环状分子时能够呈现两种不同的拓扑状态（一个环和一个三叶结）。RNA结和环已通过它们在凝胶电泳和沉降实验中的行为得到表征。该系统可用于检测RNA拓扑异构酶的存在，因为这两个RNA分子只有通过链穿入事件才能相互转化。我们发现这两种分子的相互转化可由大肠杆菌DNA拓扑异构酶III催化，这表明该酶可作为一种RNA拓扑异构酶发挥作用。环向结的转化伴随着少量RNA连环体的产生。这些发现表明，链穿入必须被视为RNA结构折叠和修饰的一个潜在组成部分。
