Cho K O, Yanofsky C
Department of Biological Sciences, Stanford University, CA 94305-5020.
J Mol Biol. 1988 Nov 5;204(1):51-60. doi: 10.1016/0022-2836(88)90598-0.
In studies with a trpE promoter-strength measuring system we observed that constructs containing the Escherichia coli trp promoter and its adjacent transcribed region yielded lower levels of trpE protein than were expected. To analyze this observation we introduced mutational changes in the nucleotide sequence preceding the trpE Shine-Dalgarno region and examined their effects on trpE mRNA synthesis, translation and decay. We found that certain deletion, insertion and substitution mutations in the pre-Shine-Dalgarno region caused a two- to fivefold increase in trpE enzyme activity. These increases were accompanied by increases in steady-state levels of trpE mRNA. Pulse-chase analyses of trpE mRNA degradation revealed that the observed steady-state trpE mRNA levels correlated with changes in trpE mRNA stability. These findings are interpreted in terms of alternative models in which the primary effect of mutational changes that elevate trpE expression is to increase trpE mRNA translation, versus increasing trpE mRNA stability.
在使用trpE启动子强度测量系统的研究中，我们观察到含有大肠杆菌trp启动子及其相邻转录区域的构建体产生的trpE蛋白水平低于预期。为了分析这一观察结果，我们在trpE Shine-Dalgarno区域之前的核苷酸序列中引入了突变变化，并研究了它们对trpE mRNA合成、翻译和降解的影响。我们发现，Shine-Dalgarno区域之前的某些缺失、插入和替换突变导致trpE酶活性提高了两到五倍。这些增加伴随着trpE mRNA稳态水平的增加。对trpE mRNA降解的脉冲追踪分析表明，观察到的trpE mRNA稳态水平与trpE mRNA稳定性的变化相关。这些发现根据替代模型进行了解释，在这些模型中，提高trpE表达的突变变化的主要作用是增加trpE mRNA翻译，而不是增加trpE mRNA稳定性。
