Rood J I, Sneddon M K, Morrison J F
J Bacteriol. 1980 Nov;144(2):552-9. doi: 10.1128/jb.144.2.552-559.1980.
The transformation of tyrR strains of Escherichia coli with multicopy plasmids which carry the tyrosine operon gave rise to modified plasmids with either insertions or deletions. The effect of each of these insertions or deletions was to decrease the level of expression of this operon. It is proposed that plasmid instability arose as a direct consequence of the metabolic effects of an overproduction of the enzymes coded for by the tyrosine operon. The results have significant implications for the cloning of genes that are repressed by the product of a regulatory gene. Since the predominant plasmid modification observed was the insertion of an IS1 element near the regulatory region of the tyrosine operon, the results also suggest a role for IS1 elements in the regulation of gene expression.
用携带酪氨酸操纵子的多拷贝质粒转化大肠杆菌的tyrR菌株，产生了带有插入或缺失的修饰质粒。这些插入或缺失中的每一个的作用都是降低该操纵子的表达水平。有人提出，质粒不稳定性是酪氨酸操纵子编码的酶过量产生的代谢效应的直接结果。这些结果对于被调节基因产物所抑制的基因的克隆具有重要意义。由于观察到的主要质粒修饰是在酪氨酸操纵子调节区域附近插入一个IS1元件，这些结果也表明IS1元件在基因表达调控中起作用。
