Hfq affects mRNA levels independently of degradation
Hfq affects mRNA levels independently of degradation
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DOI：
10.1186/1471-2199-11-17
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发表时间：
2010-02-18
影响因子：
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通讯作者：
Hajnsdorf, Eliane
中科院分区：
文献类型：
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作者：
Le Derout, Jacques;Boni, Irina V.;Hajnsdorf, Eliane
背景资料：细菌Lsm蛋白Hfq是一种RNA分子伴侣，参与许多与RNA代谢相关的反应，如复制和稳定性，小RNA活性的控制和多聚腺苷酸化。尽管这一广泛的已知功能，Hfq的全球作用几乎肯定是低估了，它的能力，结合DNA和许多其他蛋白质的相互作用，现在才开始被考虑。大肠杆菌中进行了体内研究。数据显示，当Hfq不存在时，rpsO mRNA丰度的降低伴随着其稳定性的增加。这表明hfq突变体中mRNA水平的变化不是由其RNA稳定性的修饰引起的。此外，一系列独立的实验表明，mRNA水平的降低不是翻译效率降低的结果，Hfq不直接参与rpsO表达的翻译控制。在不存在Hfq的情况下，rpsT、rpsB和rpsB-tsf的稳态mRNA水平也降低，但lpp、pnp或tRNA转录物未降低。嵌合转录物rpsO-lacZ和rpsB-lacZ（其表达分别由rpsO和rpsB启动子驱动）的丰度在hfq无效突变体中也较低，而β-半乳糖苷酶产量保持与亲本野生型菌株中大致相同。获得的数据表明，rpsO，在Hfq缺陷条件下观察到的rpsT和rpsB-tsf转录物水平不是由转录后事件引起的，例如mRNA不稳定或翻译控制的变化，而可能是由于转录活性的变化。到目前为止，Hfq如何影响转录仍不清楚。我们提出，Hfq介导的转录调节的可能机制之一可能在延伸步骤的早期操作，当Hfq与新生转录本的相互作用将有助于克服转录暂停并防止初步转录本释放。
Background: The bacterial Lsm protein, Hfq, is an RNA chaperone involved in many reactions related to RNA metabolism, such as replication and stability, control of small RNA activity and polyadenylation. Despite this wide spectrum of known functions, the global role of Hfq is almost certainly undervalued; its capacity to bind DNA and to interact with many other proteins are only now beginning to be taken into account.Results: The role of Hfq in the maturation and degradation of the rpsO mRNA of E. coli was investigated in vivo. The data revealed a decrease in rpsO mRNA abundance concomitant to an increase in its stability when Hfq is absent. This indicates that the change in mRNA levels in hfq mutants does not result from its modification of RNA stability. Moreover, a series of independent experiments have revealed that the decrease in mRNA level is not a consequence of a reduction of translation efficiency and that Hfq is not directly implicated in translational control of rpsO expression. Reduced steady-state mRNA levels in the absence of Hfq were also shown for rpsT, rpsB and rpsB-tsf, but not for lpp, pnp or tRNA transcripts. The abundance of chimeric transcripts rpsO-lacZ and rpsB-lacZ, whose expression was driven by rpsO and rpsB promoters, respectively, was also lower in the hfq null-mutants, while the beta-galactosidase yield remained about the same as in the parent wild-type strain.Conclusions: The data obtained suggest that alteration of rpsO, rpsT and rpsB-tsf transcript levels observed under conditions of Hfq deficiency is not caused by the post-transcriptional events, such as mRNA destabilization or changes in translation control, and may rather result from changes in transcriptional activity. So far, how Hfq affects transcription remains unclear. We propose that one of the likely mechanisms of Hfq-mediated modulation of transcription might operate early in the elongation step, when interaction of Hfq with a nascent transcript would help to overcome transcription pauses and to prevent preliminary transcript release.