Sledjeski D D, Gupta A, Gottesman S
Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD 20892-4255, USA.
EMBO J. 1996 Aug 1;15(15):3993-4000.
dsrA encodes a small, untranslated RNA. When over-expressed, DsrA antagonizes the H-NS-mediated silencing of numerous promoters. Cells devoid of DsrA grow normally and show little change in the expression of a number of H-NS-silenced genes. Expression of a transcriptional fusion of lacZ to dsrB, the gene next to dsrA, is significantly lower in cells carrying mutations in dsrA. All expression of beta-galactosidase from the dsrB::lacZ fusion is also dependent on the stationary phase sigma factor, RpoS. DsrA RNA was found to regulate dsrB::lacZ indirectly, by modulating RpoS synthesis. Levels of RpoS protein are substantially lower in a dsrA mutant, both in stationary and exponential phase cells. Mutations in dsrA decrease the expression of an RpoS::LacZ translational fusion, but not a transcriptional fusion, suggesting that DsrA is acting after transcription initiation. While RpoS expression is very low in exponential phase at temperatures of 30 degrees C and above, at 20 degrees C there is substantial synthesis of RpoS during exponential growth, all dependent on DsrA RNA. dsrA expression is also increased at low temperatures. These results suggest a new role for RpoS during exponential growth at low temperatures, mediated by DsrA.
dsrA编码一种小的非翻译RNA。当过度表达时，DsrA拮抗H-NS介导的众多启动子沉默。缺乏DsrA的细胞正常生长，并且许多H-NS沉默基因的表达几乎没有变化。在dsrA中携带突变的细胞中，lacZ与dsrA旁边的基因dsrB的转录融合体的表达显著降低。来自dsrB::lacZ融合体的β-半乳糖苷酶的所有表达也依赖于稳定期σ因子RpoS。发现DsrA RNA通过调节RpoS合成间接调节dsrB::lacZ。在dsrA突变体中，无论是在稳定期还是指数期细胞中，RpoS蛋白水平都显著降低。dsrA中的突变降低了RpoS::LacZ翻译融合体的表达，但不降低转录融合体的表达，这表明DsrA在转录起始后起作用。虽然在30摄氏度及以上温度的指数期RpoS表达非常低，但在20摄氏度时，在指数生长期间有大量RpoS合成，所有这些都依赖于DsrA RNA。dsrA表达在低温下也增加。这些结果表明RpoS在低温下的指数生长过程中具有由DsrA介导的新作用。
