Choi S S, Kim S K, Oh T G, Choi E C
College of Pharmacy, Seoul National University, Korea.
J Bacteriol. 1997 Mar;179(6):2065-7. doi: 10.1128/jb.179.6.2065-2067.1997.
To study the role of mRNA termination in the regulation of ermK, we introduced mismatches into terminators by in vitro mutagenesis. In wild-type ermK, only truncated transcription products were detected in the absence of induction. In contrast, only the full-length transcript was synthesized in the terminator 1 and terminator 2 double mutants, even in the absence of erythromycin. These results indicate that the expression of ermK is primarily regulated by transcriptional attenuation rather than translational attenuation. We also tested the possible contribution of translational attenuation control to the regulation of ermK by constructing a triple mutant (terminator 1 plus terminator 2 plus the methylase Shine-Dalgarno region). A higher level of beta-galactosidase synthesis was seen in the triple mutant. Therefore, unlike with previously described attenuators, it can be concluded that both transcriptional and translational attenuation contribute to the regulation of ermK, although transcriptional attenuation plays a larger role.
为了研究mRNA终止在ermK调控中的作用，我们通过体外诱变在终止子中引入错配。在野生型ermK中，未诱导时仅检测到截短的转录产物。相反，即使在没有红霉素的情况下，在终止子1和终止子2双突变体中也仅合成全长转录本。这些结果表明，ermK的表达主要受转录衰减而非翻译衰减调控。我们还通过构建三突变体（终止子1加终止子2加甲基化酶Shine-Dalgarno区域）测试了翻译衰减控制对ermK调控的可能贡献。在三突变体中观察到更高水平的β-半乳糖苷酶合成。因此，与先前描述的衰减子不同，可以得出结论，转录衰减和翻译衰减都对ermK的调控有贡献，尽管转录衰减起更大的作用。
