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首页> 外文期刊>Journal of bacteriology >Features of the rho-dependent transcription termination polar element within the hisG cistron of Salmonella typhimurium.
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Features of the rho-dependent transcription termination polar element within the hisG cistron of Salmonella typhimurium.

机译：鼠伤寒沙门氏菌hisG顺反子内rho依赖性转录终止极性元件的特征。

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摘要

Previous genetic analysis showed that the polar effects of mutations in the hisG cistron of Salmonella typhimurium are dependent on the presence of a single putative transcription termination element within the hisG gene. In fact, all proximal mutations causing translation termination are strongly polar, whereas distal ones are not. The element was mapped by isolating mutations able to relieve the polar phenotype, and they were found to be small deletions in the region downstream of the translational stop codon (M. S. Ciampi and J. R. Roth, Genetics 118:193-202, 1988). In this study, we analyzed the his-specific RNAs synthesized in vivo in different strains harboring the polar frameshift hisG2148 mutation. The nature of the polarity effects is clearly transcriptional, since shorter RNA molecules were produced. When the hisG2148 mutation was transferred in a rho background or in strains harboring the small distal deletions, an increase in readthrough transcription was observed. The transcriptional termination element was characterized in more detail by performing high-resolution S1 nuclease mapping experiments. This analysis showed that (i) termination or exonucleolytic degradation following termination produced transcripts with heterogeneous 3' ends; (ii) this process is dependent on the transcription termination factor Rho, since relief of termination occurs in a rho background; and (iii) the element appears to function as a transcription terminator, at least to some extent, even in the course of active translation of the hisG cistron.
机译：先前的遗传分析表明，鼠伤寒沙门氏菌的hisG顺反子中突变的极性影响取决于hisG基因中单个推定转录终止元件的存在。实际上，所有导致翻译终止的近端突变都是强极性的，而远端突变则不是。通过分离能够缓解极性表型的突变来定位该元件，发现它们是翻译终止密码子下游区域中的小缺失（M.S.Ciampi和J.R.Roth，遗传学118：193-202，1988）。在这项研究中，我们分析了在不同菌株中体内合成的his特异性RNA，这些菌株具有极性移码hisG2148突变。极性效应的性质显然是转录的，因为产生的RNA分子较短。当hisG2148突变在rho背景中或在具有较小远侧缺失的菌株中转移时，观察到通读转录的增加。通过执行高分辨率S1核酸酶作图实验，可以更详细地表征转录终止元件。该分析表明：（i）终止或终止后的核酸外降解降解产生具有异质3'末端的转录本; （ii）该过程取决于转录终止因子Rho，因为终止的解除发生在rho背景中; （iii）即使在hisG顺反子的主动翻译过程中，该元件似乎也至少在某种程度上起着转录终止子的作用。

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