Carnevali F, Caserta M, Di Mauro E
J Mol Biol. 1983 Mar 25;165(1):59-77. doi: 10.1016/s0022-2836(83)80242-3.
The effect of the insertion of foreign genes or gene systems in closed DNA domains has been investigated in vitro in purified systems. We observe that in chimaeric plasmids two apparently independent classes of modifications, (1) functional and (2) topological, do take place in defined instances. (1) Among the screened yeast gene systems, examples have been found of DNA sequences that upon insertion cause activation of in vitro transcription of distant genes. (2) Foreign DNA sequences may lead to new topological features of the harbouring plasmids; it is shown that more than one S1-sensitive secondary structure may be contemporaneously present on the same chimaeric plasmid. DNA superhelicity is a prerequisite of these modifications. The two classes of effects (1) functional and (2) topological are not a priori directly related one to the other but appear to be two independent consequences of the same cause: the insertion of foreign DNA sequences into closed DNA domains. These observations suggest a regulatory model of gene expression based on alternative topologies of closed DNA domains.
在体外纯化系统中，研究了将外源基因或基因系统插入封闭DNA结构域的效果。我们观察到，在嵌合质粒中，两种明显独立的修饰类型，即（1）功能性修饰和（2）拓扑学修饰，确实会在特定情况下发生。（1）在筛选的酵母基因系统中，已发现一些DNA序列的例子，这些序列插入后会导致远距离基因的体外转录激活。（2）外源DNA序列可能会导致所携带质粒出现新的拓扑特征；结果表明，同一嵌合质粒上可能同时存在不止一种对S1敏感的二级结构。DNA超螺旋是这些修饰的前提条件。这两类效应，即（1）功能性效应和（2）拓扑学效应，并非先验地直接相互关联，而是似乎是同一原因的两个独立结果：将外源DNA序列插入封闭DNA结构域。这些观察结果提示了一种基于封闭DNA结构域的替代拓扑结构的基因表达调控模型。
