Phan Trang Thi Phuong, Schumann Wolfgang
Institute of Genetics, University of Bayreuth, Bayreuth, Germany.
Curr Microbiol. 2009 Oct;59(4):463-8. doi: 10.1007/s00284-009-9461-4. Epub 2009 Jul 28.
About 2% of the Bacillus subtilis genes are subject to regulation by riboswitch-controlled mechanisms. One of them is the L-lysine-dependent lysC gene which is turned on when the L-lysine concentration within the cytoplasm is low. In the presence of a high L-lysine concentration, only a 0.27-kb transcript is synthesized representing the riboswitch due to transcription termination. When the L-lysine concentration is low, the full-length 1.6-kb transcript is produced due to transcription anti-termination. Here, we show for the first time that even under conditions of transcription anti-termination the truncated form of the RNA is still predominant. This 0.27-kb transcript is neither the result of enhanced stability nor does it result from processing of the full-length transcript. When the region coding for the transcription terminator was removed, the riboswitch RNA failed to be produced. These data were confirmed by analysis of a transcriptional fusion between the promoter-riboswitch region of lysC with and without a functional transcriptional terminator and the lacZ reporter gene. The putative function(s) of the riboswitch under conditions of low L-lysine concentration is discussed.
约2%的枯草芽孢杆菌基因受核糖开关控制机制的调控。其中之一是L-赖氨酸依赖的lysC基因，当细胞质内L-赖氨酸浓度较低时该基因开启。在L-赖氨酸浓度较高时，由于转录终止，仅合成代表核糖开关的0.27 kb转录本。当L-赖氨酸浓度较低时，由于转录抗终止作用，会产生全长1.6 kb的转录本。在此，我们首次表明，即使在转录抗终止条件下，截短形式的RNA仍然占主导。这种0.27 kb的转录本既不是稳定性增强的结果，也不是全长转录本加工的结果。当编码转录终止子的区域被去除时，核糖开关RNA无法产生。通过分析lysC启动子-核糖开关区域（有或没有功能性转录终止子）与lacZ报告基因之间的转录融合，证实了这些数据。讨论了在低L-赖氨酸浓度条件下核糖开关的假定功能。
