Rho-independent transcription terminators inhibit RNase P processing of the secG leuU and metT tRNA polycistronic transcripts in Escherichia coli
Rho-independent transcription terminators inhibit RNase P processing of the secG leuU and metT tRNA polycistronic transcripts in Escherichia coli
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DOI：
10.1093/nar/gkm991
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发表时间：
2008-02-01
影响因子：
14.9
通讯作者：
Kushner, Sidney R.
中科院分区：
文献类型：
--
作者：
Mohanty, Bijoy K.;Kushner, Sidney R.
在大肠杆菌中广泛接受的trna加工模型涉及到RNase E在多顺反电子转录物中进行必要的初始切割，以产生前trna，这些前trna随后成为RNase p的底物。最近，我们发现了两个多顺反子tRNA转录本，它们的核内分解加工完全依赖于RNase p。在这里，我们表明secG - leuU和metT - leuW glnU glnW metU glnV glnX多顺反子转录本的加工是通过不同类型的成熟途径进行的。具体来说，RNase P主要通过RNase E在核内溶解去除远端rho非依赖性转录终止子后分离每个操纵子内的tRNA单元。在RNase E缺失菌株中，不能去除rho非依赖性转录终止子会抑制RNase P对两种转录物的加工，导致成熟tRNA水平降低，全长转录物水平显著增加。此外，我们首次发现RNase G也可以去除与secG leuU操纵子相关的rho非依赖性转录终止子。我们的数据还表明，Rne-1蛋白在非允许温度下对tRNA底物保持显著的活性。综上所述，很明显，在大肠杆菌中，有多种途径参与了trna的成熟。
The widely accepted model for the processing of tRNAs in Escherichia coli involves essential initial cleavages by RNase E within polycistronic transcripts to generate pre-tRNAs that subsequently become substrates for RNase P. However, recently we identified two polycistronic tRNA transcripts whose endonucleolytic processing was solely dependent on RNase P. Here we show that the processing of the secG leuU and metT leuW glnU glnW metU glnV glnX polycistronic transcripts takes place through a different type of maturation pathway. Specifically, RNase P separates the tRNA units within each operon following the endonucleolytic removal of the distal Rho-independent transcription terminator, primarily by RNase E. Failure to remove the Rho-independent transcription terminator inhibits RNase P processing of both transcripts leading to a decrease in mature tRNA levels and dramatically increased levels of full-length transcripts in an RNase E deletion strain. Furthermore, we show for the first time that RNase G also removes the Rho-independent transcription terminator associated with the secG leuU operon. Our data also demonstrate that the Rne-1 protein retains significant activity on tRNA substrates at the non-permissive temperature. Taken together it is clear that there are multiple pathways involved in the maturation of tRNAs in E. coli.