A Novel RNA Phosphorylation State Enables 5' End-Dependent Degradation in Escherichia coli.
A Novel RNA Phosphorylation State Enables 5' End-Dependent Degradation in Escherichia coli.
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DOI：
10.1016/j.molcel.2017.05.035
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发表时间：
2017-07-06
期刊：
影响因子：
16
通讯作者：
Belasco JG
中科院分区：
文献类型：
--
作者：
Luciano DJ;Vasilyev N;Richards J;Serganov A;Belasco JG
曾经逃过检测的RNA修饰现在被认为是控制原核生物和真核生物RNA寿命的关键。例如，将细菌转录本的5 ‘端三磷酸转化为单磷酸，会触发RNase e对5 ’端依赖性降解。然而，从未报道过细菌中存在二磷酸化的RNA，也没有提出过这种修饰的生物学作用。通过使用一种新的测定方法，我们在这里显示，对于具有代表性的大肠杆菌mrna，每个转录物的约35-50%被二磷酸化。其余部分主要是单磷酸化的，令人惊讶的是，很少有三磷酸化的RNA。此外，二磷酸化的RNA是RNA焦磷酸水解酶RppH的首选底物，其生物学功能以前被认为是从三磷酸化的转录物中去除焦磷酸。我们得出结论，在大肠杆菌中，诱导5 '端依赖性RNA降解的三磷酸到单磷酸转化是一个两步过程，包括通过一种未知的酶去除γ-磷酸，从而使随后的RppH能够去除β-磷酸。Luciano等人的研究表明，二磷酸化的mRNA 5 '端在大肠杆菌中大量存在，并且大肠杆菌RNA焦磷酸水解酶RppH更喜欢二磷酸化的底物而不是三磷酸化的底物。他们的发现表明，在RNase E切割之前，将三磷酸化的5 ‘端转化为单磷酸化的5 ’端涉及到不同酶的连续磷酸去除。
RNA modifications that once escaped detection are now thought to be pivotal for governing RNA lifetimes in both prokaryotes and eukaryotes. For example, converting the 5′-terminal triphosphate of bacterial transcripts to a monophosphate triggers 5′-end-dependent degradation by RNase E. However, the existence of diphosphorylated RNA in bacteria has never been reported, and no biological role for such a modification has ever been proposed. By using a novel assay, we show here for representative Escherichia coli mRNAs that ~35–50% of each transcript is diphosphorylated. The remainder is primarily monophosphorylated, with surprisingly little triphosphorylated RNA evident. Furthermore, diphosphorylated RNA is the preferred substrate of the RNA pyrophosphohydrolase RppH, whose biological function was previously assumed to be pyrophosphate removal from triphosphorylated transcripts. We conclude that triphosphate-to-monophosphate conversion to induce 5′-end-dependent RNA degradation is a two-step process in E. coli involving γ-phosphate removal by an unidentified enzyme to enable subsequent β-phosphate removal by RppH. Luciano et al. show that diphosphorylated mRNA 5′ ends are abundant in E. coli and that the E. coli RNA pyrophosphohydrolase RppH prefers diphosphorylated substrates to their triphosphorylated counterparts. Their findings suggest that converting triphosphorylated to monophosphorylated 5′ ends before RNase E cleavage involves sequential phosphate removal by distinct enzymes.
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