Zengel J M, Lindahl L
Department of Biological Sciences, University of Maryland, Baltimore 21228, USA.
J Bacteriol. 1996 Apr;178(8):2383-7. doi: 10.1128/jb.178.8.2383-2387.1996.
Ribosomal protein L4 of Escherichia coli regulates transcription of the 11-gene S1O operon by promoting premature termination of transcription (attenuation) at a specific site within the 172-base untranslated leader. We have analyzed the roles of various domains of the leader RNA in this transcription control. Our results indicate that the first 60 bases of the leader, forming the three proximal hairpin structures, are not essential for in vivo L4-mediated attenuation control. However, a deletion removing the fourth hairpin, which is immediately upstream of the terminator hairpin, eliminates L4's effect on transcription. Base changes disrupting complementarity in the 6-bp stem of this hairpin also abolish L4 control, but compensatory base changes that restore complementarity also restore L4's effect. In vitro transcription studies confirm that this hairpin structure is necessary for L4's role in stimulating transcription termination by RNA polymerase.
大肠杆菌的核糖体蛋白L4通过促进转录在172个碱基的非翻译前导区内的特定位点提前终止（衰减）来调节11基因S1O操纵子的转录。我们分析了前导RNA的各个结构域在这种转录控制中的作用。我们的结果表明，前导序列的前60个碱基形成三个近端发夹结构，对于体内L4介导的衰减控制不是必需的。然而，缺失紧邻终止子发夹上游的第四个发夹会消除L4对转录的影响。破坏该发夹6个碱基茎中互补性的碱基变化也会消除L4的控制作用，但恢复互补性的补偿性碱基变化也会恢复L4的作用。体外转录研究证实，这种发夹结构对于L4在刺激RNA聚合酶转录终止中的作用是必需的。
